Note: Descriptions are shown in the official language in which they were submitted.
z~
The present invention is a divisional of Canadian patent
application No. 250,637 filed on April 21, 1976 and relates to
silicon carbide fibers having a high strength and a method for
producing said fiBers.
Silicon carBide is a compound shown by a chemical
formula of SiC and i5 usually produced in a block form by
reacting SiO2 with C at a high temperature of about 1,900-2,200C.
Accordingly, it is necessary in order to produce a
silicon carbide molding having a particularly de~ined shape
lQ that the above described hlock is pulverized and a binder is
added to the pulverized silicon carbide and the resultin~ mixture
: is molded and then si`.ntered.
However, it has been impossible to produce fibrous
silicon carbide moldings through the above described process.
United States Patent 3,433,725 discloses: a method for producing : -
silicon carbide fibers by reacting carbon fibers with SiC14 gas
which is being supplied, ~ithin a temperature range of 800- :
1,20QC. United $tates Patent 3,403,008 also teaches production
of silicon carbide fibers and moldings, in which viscose rayon
tows are i:mmersed in liquid silicon tetrachloride to form rayon
silicate and then the formed rayon silicate i~s baked up to
1,Q00-2,000.C at a rate of 5QC~hr. under vacuum of 1-10 mmHg
in a tubular oven to form silicon carbide ~i.bers.. Ho~ever, in
th.e silicon c~rhide fibers produced in the above. descri.bed
process, cry-stal grains of $iC constituti`ng the fibers are lar~e,
the strength is 1QWt the di`ameter o~ the fi~ers i.s relatively
large, the production cost i.s high and the application is
considerably limited.
~, ~6
7`~
The present invention provides a method for producing
a silicon carbide fiber having a hi.gh tensile strength which
comprises
(1) preparing a spinning solution from at least one
organosilicon high molecular weight compound having a softening
point of higher than 50C, in which silicon and carbon are the
main skeleton components, and spinning said spinning solution
into a fiber,
(2) preliminarily heating the spun fiber at a temper-
ature of 350-800C under vacuum or a non-oxidizing atmosphere
~ to volatilize low molecular weight compound contained therein,
and
(3) baking the thus trea~ed fi~er at a temperature
of 800-2,000C under vacuum or at least one non-oxidizing
; atmosphere selected from the group consisting of an inert gas,
CO gas and hydrogen gas, to form said silicon car~ide fiber.
In particular, according to the present invention, a
silicon carbide fiber having a high strength.can be produced by
the following steps:
(1l a step for producing or~anosilicon high. molecular
weight compounds, in which silicon and car~on are the main
skeleton components, ~y polycondensation reaction through at
least one already- weIl known process of addition of a poly-
condensation catalyst, irradiation and heating,
C2~ a step for obtainlng organosil$~cQn hi.gh molecular
weight compounds, of which a softeni.ng poi.nt is. higher than 5~C,
C31 a 5*ep for producing a spinnIng solution from
said organic high molecular ~eight compound ~nd spinning said
,
-2-
7C~2~
solution into fiber,
(~) a step for preliminarily heating the spun fiber
under vacuum or a non-oxidizing atmosphere, and
(5) baking the thus treated fiber at a high temper-
ature under vacuum or atmosphere of inert gas, CO gas or hydrogen
gas to form SiC fibers.
The present invention also provides a method for
producing a silicon carbide fiber having a high tensile strength
which comprises:
(A) subjecting at least one organosilicon compound
selected from (1) a compound having only Si-C bond, (2) a
compound having Si-H bond in addition to Si-C bond, (3) a
compound having Si-X bond, X being halogen, (4) a compound having
Si-N bond, (5) a compound having Si-oR bond (R=alkyl or aryl),
(6) a compound ha~ing Si-OH bond, (7) a compound having Si-Si
bond, (8) a compound having Si-O-Si bond, (.9~ an ester of
organosilicon compound and (10) a peroxide of organosilicon
compound, to polycondensation to produce an organosilicon high
molecular weight compound, in which silicon and carbon are the
main skeleton components,
(B) reducing the content of low molecular weight
compound mixed together with said high molecular welght compound
by treating the mixture with at least one treatment selected
from the group o~ treatments consisting of contacting said
mixture w-ith a suitable solvent, a~ing ~aid mixture at a temper-
ature of 5Q-700C and distilling said mixture at a temperature
of 100-500C, to produce an organosilicon hi.gh. molecular weight
compound having a soften~ng point of higher th.an 50C,
--3--
7~3~6
(C) preparing a spinning solution from said obtained
organosilicon high molecular weight compound and spinning said
spinning solution into a fiber,
(D) preliminarily heating the spun fiber at a temper-
ature of 350-800C under vacuum to volatilize remaining low
molecular weight compounds, and
(E) baking the thus treated fiber at a temperature
of 800-2,000C under vacuum or at least one non-oxidizing
atmosphere selected from the group consisting of an inert gas,
CO gas and hydrogen gas.
The present invention further provides a method for
producing a silicon carbide fiber having a high tensile strength
which comprises:
(A) subjecting at least one organosilicon compound
selected from (1) a compound having only Si-C bond, (2) a
compound having Si-H bond in additlon to ~i-C bond, (3) a
compound having Si-X bond, X being halogen, (4~ a compound having
Si-N bond, (5) a compound having Si-OR bona (.R=al~yl or aryl),
(6) a compound having Si-OH bond, (7~ a compound having Si-Si
bond, (8) a compouna having Si-O-Si bond, (.9~ an ester of
organosilicon compound and ~10~ a peroxide of organosilicon
compound, to polycondensation to produce an organosilicon high
molecular weight compound, in which silicon and carbon are the :~
main skeleton components,
~ reducing the content of lo~ molecular weight
compound mixed together with.said high. molecular weight compound
by treating the mixture ~ith at least one treatment selected
from the group of treatments consis:ting of contacting said
,
,t,~j~X~
mixture with a suitable solvent, aging said mixture at a temper-
ature of 50-700C and distilling said mixture at a temperature
of 100-500C, to produce an organosilicon high molecular weight
compound having a softening point of higher than 50C,
(C) preparing a spinning solution from said obtained
organosilicon high molecular weight compound and spinning said
spinning solution into a fiber,
(D) heating the spun fiber at a temperature of 50-
400C under an oxidizing environment to form an oxide layer on
10 the fiber surface,
(E) preliminarily heating the spun fiber at a
temperature of 350-800C under a non-oxidizing atmosphere to
volatilize remaining low molecular weight compound, and
(F) baking the thus treated fiber at a temperature
of 800-2,000C under vacuum or at least one non-oxidizing
atmosphere selected from the group consisting of an inert gas,
CO gas and hydrogen gas.
According to another aspect of the present inventlon
there is provided continuous silicon carbide fibers having
20 tensile strength of 200-800 Kg/mm2, Young's modulus of 10-40
ton/mm2 and resistant to corrosion and oxidation and showing
no decrease in the tensile strength and Young's modulus at a
temperature of 800C to 1,400C, which are composed of ultra-
fine grain silicon carbide having an average grain size of
less than 0.1 ~.
The organos~l~con compounds of th.e s~tarting materials
for producing the organosilicon hi;gh mole.cul~r ~eight compounds,
in whi.ch silicon and carbon are th.e main skele.ton components,
-
--5--
"'7''3~
and which are to be used for the spinning can be classified
into the following groups (1)(10).
(1) Compounds having only Si-C bond:
Silahydrocarbons, such as R4Si, R3Si(R'SiR2)nR'SiR3,
carbonfunctional derivatives thereof belong to this group.
For example,
(CH3)4Si, (CH2=CH)4Si, (CH3)3SiC = CSi(CH3)3,
2 5 ( 2)4' (C2H5)3SicH2cH2cl~ (C6H5)3siC02
R\ / CH2 R R\ / CH2
R CH2 R , R CH2 2
<~2 Cl ~ CH ~ Cl,
( 3)3Si ~ Si(CH3)3,
--6--
3~æ~
3) 3 2 ~-CH2Si (CH3) 3r
CH =CH-si-e~3-si-cH=cl~2~
H2 ( 3) 2
f I s i,
H2C\ ~CH2 ,(CH3) 2Si ~ Si (CH3) 2
Si CH2
R R
(2) Compounds having Si-H bond in addition to Si-C bond:
Mono-, di-, and triorganosilanes belong to this group.
For exa~ple,
(C2H5) 2SiH2, (CH2) 5siH2 ' (CH3) 3SiCH2Si (CH3) 2H,
ClCH2SiH3,
H--Si ~3 si--H,EI--Si--~--Si-CH=C
H2 H / CH3
si~ si,
H C CH H2C CH2
21 1 2 1 1i / CH3
(CH3)2Sl Si(CH3~2, (CH3)2si / \ H
CH2 CH2
(3) Compounds having Si-X bond; X being halogen:
Organohalogensilanes.
For example,
CH2=CHSiF3~ C2H5SiHC12,
(CH3)2(ClCH2)Si5i(CH3)2Cl, (C6H5)3SiBr~
R R CH2
Cl-Si-CH -C~ -Si-Cl,
1 2 2 ~ C125i SiC12
R R \ C-C \
C12si\ SiC12
CH2
(4) Compounds having 5i-N bond:
Silylamines belong to this group.
For example,
R H~
/~ \=,/ CH=CH2
Si ~ (C~3)2N-SIi-N(C~3)2
R NH ~ CH3
(5) Si-oR organoalkoxy (or aroxy) silanes:
For example,
(CH3)2Si(OC2H5)2, C2H5siC12(0C2H5)~
p-ClC6H40Si(CH3)3,
/ ~
` R O
~,
(6) Compounds having Si-OH bond:
Organosilanes.
For example,
(C2H5)3SiOH, CCH3)2Si~OH~2~ C6~5Si(OH)3,
(HO)(CH3~2SiCH2Si(CH3)2 ~ tOH~,
HO--5i~Si--OH
R R
'_'
7~3~æ~
(7) Compounds having Si-Si bond:
For example,
(CH3)3SiSi(CH3~2Cl, (CH3)3SiSi(CH3)3,
(c6H5)3sisi(c6Hs)2si(c6H5)2
/ CH2 Si(CH3)2
CjH2 Si(.CH3~2 / CH2 \
CH2 / Si(CH3)2 , (- 3~2S Si(.CH3)2
CH2 \ / Si(CH3)2,
(CH3~2
Si(CH3i2
CH2 \ Si~ 3 / Si\CH3~2
S i ~ /
(CH3~2 Si
(CH.312
CH2 ~.CH3~2
CH2 Si(.CH3~2 CH2 Si \
CH2 / Si(.CH3~2 , 2 Si Si(CH3)3
Si (CH3~2
(- 3)2
(81 Co~pound~ h.~Ying ~I-O-Si ~ond:
Organo~Uox~nes.
For example,
--10--
7'~
(CH3) 3SiOSi (CH3) 3, HO(CH3) 2SiOSi (CH3) 20H,
C12 (CH3) SioSi (CH3) ClOSi (CH3) C12, [ (C6H5) 2Sio] 4,
CH2=c(cH3)co2cH2si ' (C~3)2cH202 ( 3 2
R2Si-CH2-SiR2 2 1 2 Sl iR2
O O H2 I CIH2
2 i CH2 SiR2 , R2Si--O--SiR2
CH2 o
R2 S i \ S i R2 R2 S l Sl i R2
O O , O O
\ / \ /
SiR2 SiR2
R2 S i--CH2--S i R2 H2 f-- C 2 - .
O O
R2Si-- O--SiR2 , o
(9) Esters of organosilicon compounds-
Esters formed from silanols and acids.
(:CH3~2Si(OCoCH3)2
a) Peroxides of organosilicon compounds:
(CH3~3SiOOC ~ (CH3) 3, (CH31 3sioosi (.CH3) 3
In the aboye ~ormulae, R sho~$ alkyl or ary~l groups.
--11--
From these starting mater.ials are produced organo-
silicon high molecular weight compounds, in which silicon and
carbon are the main skeleton components. For example, compounds
having the following molecular structures are produced.
I
(a) -Si - (C)n - Si - O-
(b) -Si - O - (C)n - O-
(c) -Si - (C)n-
(d) The compounds having the above described skeleton
components (a~ - (c) as at least one partial
structure in linear, ring and three dimensional
structures or mixtures of the compounds having the
above described skeleton components (a~ - (c).
The compounds having the above descri~ed molecular
structure are, for example as follo~s.
(.al -Si - CC]n - Si - O-
.
n - 1, poly(:silmethylenesiloxanel,
n - 2, poly(~silethylenesiloxanel,
n = 6, poly(silphenylenesiloxane),
(bl -Si - O - (:C)n - O-
n ~ 1, poly(methyleneoxy~iloxanel t
-12-
,
J\7~2I~
n = 2, poly(ethyleneoxysiloxane),
n = 6, poly(phenyleneoxysiloxane),
n = 12, poly(diphenyleneoxysiloxane)
(c) - Si - (C)n -
n = 1, polysilmethylene,
n = 2, polysilethylene,
n = 3, polysiltrimethylene,
n = 6, polysilphenylene,
n = 12, polysi.ldiph.enylene
(d) The compounds having the above described skeleton
components as at least one partial structure in
linear, ring and three dimensional structures or
mixtures of the compounds having the above
described skeleton components (a~ - (.c).
The production of the organosilicon high molecular
weight compounds in which silicon and carbon are the main skeleton
components from the starting materials of the organosilicon
compounds belonging to the above described groups (1~ - (10~ can
be effected by polycondensation attained ~y suhjecting the
organosilicon compounds belonging to the. a~ove de~cri.bed groups
~ (10~ to at least one of irradiation, heati.ng and addition
of a catalyst for the pol~condensation.
For example, some ~ell known reaction formulae for
obtaining the above described or~ano.silicQn h~gh molecular weight
compounds from the above described starting materi.als belonging
~ 7~
to the groups (1) - ~10) through at least one of addition of
the catalyst, irradiation and heating, are exemplified as
follows.
(1) CH3 / CH2 /CH3r fEI3
Si SiKOH~ -Si-CH -
CH3/ CH / CH CH3 n
\ / \ fH3
Si CH2 Heating> -- li CH2CH2CH2
CH3 CH2 _CH3 _ n
(3) CH ~ 3i-H+HC-CH H2PtC16 ~i~fi- (CH2)2
CH3 CH3 H3 CH3 ~ n
. _
4) CIH3 f~3 (1) H20 CIH3 CIH3 -
Cl--Si--CH2CH2--Si-Cl ~ l-f i-CH2CH2~ O~ _
H3 CH3 l _CH3 CH3 - n
: _
/ \ ~ CH Heating) l~ O li O ~
CH3 NHPh CH3 n
Si + HO ~ o f. ~ ~ n
-14-
- ' : : ' `
'
)7~32~
(7)CH~--Sl-OH ~ ~3 CH3
(8)(CH3) 27i-CH2 1 i (CH3) 2 I f
O O H2S04 -- C 2 i O
~ l l
(CH3) 2Si-CH2-Si (CH3) 2 _CH3 CH3 n
(9)CH2
H / S (CH hv ~ Polymer
(C 3)2S \ ~ ~
(CH3~2Si-Si(CH3)2
(10) 1 3 1 3 Cl Cl
Cl - Si - Si - Cl Heating ~ -Si-CH2-Si-CH2-
3 3 3 3 n
A more detailed explanation will be made with respect
to the thermal polycondensation reaction. At least one organo-
silicon compound selected from the ahove descri~ed groups (1~ -
(10) is polymerized within a temperature range of 200-1,500C
under vacuum, an inert gas, hydrogen gas, C0 gas, C02 gas, a
hydrocarbcn gas or an organosilicon compound gas, if necessary,
under pressure to produce the organosilicon high molecular
weight compounds in ~hi:ch silicon and carbon are the main
skeleton components.
The reason why the above described reaction should
be effected within the temperature range of 2Qa-1,5Q0C is
"~
--15--
as follows. When the temperature is lower than 200C, the
synthesis reaction does not sat.isfactorily proceed, while when
the temperature is higher than 1,500C, the product becomes SiC
compound and it is impossible to form fibers in the succeeding
step, so that the temperature range must be 200 to 1,500C
and best results can be obtained within the temperature range
of 300-1,200C.
In the above described synthesis reaction, a radical
initiator of less than 10% may be ad~ed to the above described
starting material. The above described radical initiators are,
for example, benzoyl peroxide, di-tert.-butyl peroxyoxalate,
di-tert.-butyl peroxide, azoisobutyronitrile and the like. The
above described synthesis reaction does not al~ays need these
radical initiators, but their use permits a lo~eri.ng of the
temperature for starting the reaction by the succeeding heating
or the obtaining of a reaction product having an increased
average molecular weight.
When oxygen i.s present upon heating in the above
described synthesis reaction, the radi.cal polycondensation
reaction does not occur due to oxygen or even i.f said reaction
occurs, the reaction stop~ in the cours:e, s.o that th.e poly-
condensation reacti.on must be effected b.y heating under a
vacuum or at least one environment selected from the group
consisting of an inert, gas, hydrogen gas, CO yas, CO2 gas, a
hydrocarbon gas, and an organosilicon comp~und gas..
In the thermal polycondensation re.action, a pressure
is generated, so that it is not always. nece.ssary to apply
particularly a pres.sure but ~hen a pressure is: appli~d, such
`~ J
-16-
2~
pressure may be applied b~ means of at leas-t one of an inert
gas, hydrogen gas, CO gas, CO~ gas, a hydrocarbon gas and an
organosilicon compound gas.
A mechanism in which the organosilicon high molecular
weight compounds in which silicon and carbon are main skeleton
components, are produced by the above described synthesis
reactionr will be explained hereinafter, for example, in the
case of synthesis from methylchlorosilane.
Methyl group of methylchlorosilane is decomposed
into a methyl free radical and silyl free radical by the heating.
The methyl free radical takes out hydrogen from methyl group
bonded to silicon to form carbon free radical and methane gas is
formed. On the other hand, hydrogen free radical is formed from
methyl group bonded to silicon and at the s.ame time carbon free
. radical is also formed. Presumably, the silyl free radical
and the carbon free radical formed as. described above hond to
form silicon-carbon bond and the organosilicon high molecular
~- weight compounds can be formed based on the above described
reaction and the above described hydrogen free radical becomes
hydrogen gas.
In draw~ngs ~hi.ch illustrate th.e present inyention:
Figure 1 is a di~gram of an e~odiment of apparatus
for producing the organos~licon high. molecular ~ei.ght compounds;
Figure 2 shows a rel~ti.on of th.e. xesi.dual weight to
the heating temperature.~hen the high molecular ~elght compounds
containing lo~ molecular ~ei.ght compc.unds are h.eated;
Figure 3 sh.ows a ~elation of the xesi.dual ~eight to
the heating temperature ~hen the hi.gh molecular ~ei.gh.t com~ounds
-17-
~ ~7C~6
containing low molecular weight compounds are heated under
vacuum;
Figure 4 shows X-ray dif~raction patterns when the
silicon high molecular weight compound fibers are heated at
various temperatures;
Figure 5 shows a relation of the tensile strength to
the heating temperature when the spun fibers according to the
present invention are heated from 700C to 2,000C;
Figure 6 shows a relation of the tensile strength to
the baking temperature when the spun fibers are baked under no
tension;
Figure 7 shows a relation o$ the tensile ~trength to
the baking temperature when the spun fibers are baked under a
tension;
Figure 8 shows a relation of the tensile s.trength to
the baking temperature when the spun fibers are baked while
applying ultrasonic wave;
Figure 9 shows a relation of the tensi,le strength to
the baking temperature when the spun fibers are baked ~hile
applying a tension together with ultrasonic ~ave;
Figures lQ and 11 show electron dlffraction photo-
graphs of the silicon carbide fibers ob~tained ~y baking under
a tension or no tension, respectively;
Fi,gure 12 shows: relati,ons of the tensile strength and
the Young's modulus to the diameter of the si,li.con carbide fiber
according to the present i,nventlon; ~ :.
Figure 13 i,s a diagram sho~i,ng variations of the ~ `
tensile strength and tne Youngls modulus based on temperature
.
.
-18- ,
~..... . .
:` ' ' ` ~
7~
of the silicon carbide fiber according to the present invention;
Figure 14 shows an X-ray diffraction pattern of the
silicon carbide fiber baked at 1,500C;
Figures 15-17 are X-ray diffraction photographs of
Pin hole method of the silicon caxbide fiber of the present
invention;
Figure 18 is a diagram showing relations of the average
grain size of SiC crystal and the tensile strength of the
silicon carbide fiber of the present invention to the baking
temperature;
Figure 19 is a diagram showing a relation of the
tensile strength to the average grain size of SiC crystal o~
the silicon carblde fiber of the present invention;
Figures 20-23 sho~ photographs obtained by observing
SiC crystal in the silicon carbide fiber of the present
invention through a super h.igh voltage electron microscope; and
:Figure 24 is a diagram of an em~odiment of apparatus
for continuously effecting the method of the present invention.
An embodiment of apparatus for the above described
synthesis reaction is a stationary autocla~e. I:n this case,
;the heating temperature i5 preferred to be 30Q-5~0C. Another
embodiment for the above described synthes.is reacti.on is shown
in Figure 1. In th~:s dra~ing, from a valve 1, the starting
material is $ed ~nto a h.e~ting reaction column 2, wh.erein the
heating is effected at a temperature of 3Q0-1,500C, prefera~ly
500-1,20QC, a part of th.e organosili.con high molecular ~eight
compound for producin~ sili.con carbide f~bers of the present
i.nvent;on among the reaction pxoducts i~ discharged from the
~. ,
--19-- :
3'7~
reaction column through a valve 3 and low molecular weight
compounds formed in the heating reaction column 2 are fed into a
separating colu~n 5 through a valve 4 and in said column 5
distillation and separation are effected and the formed gas is
discharged from the column through a valve 6 and a high molecular
weight compound is taken out from the column through a valve 7.
The low molecular weight com~ounds separated in the tower 5 are
circulated into the heating reaction column 2 through a valve 8.
The reason why the organos.ilicon high molecular
weight compound in which silicon and carbon are the main skeleton ,
components, are used for the starting material of spinning in
the method of the present invention is that if ~ilicon or carbon
is present as a side chain, this side-element is easily
separated and volatilized b~ heating, while the skeleton
consisting of silicon and carbon components i.s not easily
decomposed and volatilized by the heating and sili.con and carbon
bond at a high temperature to form silicon carbi.de.
The organosilicon high molecular weight compounds
produced by the above described reactions, in wh.i.ch silicon
and carbon are the main skeleton components, contain low molecular
weight compounds soluble in an alcohol, ~uc~ as methyl alcohol, !:
ethyl alcohol, and the li.ke or acetone and tne ll.ke and the
softening point o~ the resulting organic sili.cone high molecular
weight compounds depends upon the: content o~ the lo~ molecular
wei.ght compounds and there are the cases whRre the softening
po~nt becomes hi`~her than 5QC and sai`d point ~,eco.~es lo~er than
5Q~C. As menti`,oned h.ereinaftex, tne s.o~teni~ng Point mus~t be
hi.~her than 5Q.C for t~e s~ta,rti`ng materlal o~ sp~nni,ng.
..
-20-
The low mulecular weight compounds soluble in the
solvent are mainly -the low molecular weight compounds having an
average molecular weight o~ 200-800, and when such compounds
are present in a large amount, the softening point of the
organosilicon high molecular weight compounds is less than 50C
and in the step of preliminary heating of the spun fibers under
vacuum, the above described low molecular weight compounds
melt and stick together with intermediate compounds having a
slightly larger molecular weight than the low molecular weight
compounds and further melt and bond with high molecular weight
compounds having a larger molecular weight than the above
intermediate compounds, whereby the shape of the spun fiber is
lost. In the fiber obtained by spinning organosilicon high
molecular weight compounds having a softeni.ng point of higher
than 50C, wherein the content of the lo~ molecular weight
compound is small, the major portion of the above described low
molecular weight compounds volatilizes upon the prellminary
heating under vacuum and the shape of fiber can be maintained.
In addition, when the spun fiber are su~jected to heating at a
low temperature under an oxidizing atmosphere for formation
of an oxide layer as explained hereinafter, the heating must
be effected at a temperature of higher than 50C. The fibers
formed from the organosilicon high molecular weight compounds
having a softening point lower than 50C will melt and stick
with one another, ~hen the oxIdized layer is formed, and the
shape of the fibe~s will thus be lost.
In general, as: the molecular ~e.ight of an organo-
silicon compound increase~, the boi.li`ng point hecomes h.igher
-21-
'7~ 6
and even if heatin~ is effectecl under vacuum, the volatilizatlon
becomes difficult. For example, the boiling point of Si6C14H36
(molecular weight: 372) under a reduced pressure of 1 mmHg is
150-153C, while the boiling point of SigC27H74 (molecular
weight: 650) under a reduced pressure of 1 mmHg is 245-300C
and even if the organosilicon compound havir.g a larger molecular
weight than that of SigC27H74 is heated under vacuum, such a
compound does not substantially volatilize. For example, a
solid organosilicon high molecular weight compound obtained by
heating dodecamethylcyclohexasilane at 400C for 48 hours under
argon atmosphere in an autoclave is diss-olved in hexane and the
resulting solution is mixed with acetone and the product which
is not dissolved in acetone, is produced. ~ relation of the
heating temperature to the residual we~ght when the resulting
product is heated under vacuum (:1 x 10 3 mmH.g~, is shown in
Figure 2. As seen from Figure 2 the ~eight decrease is not
substantially o~served at the heating temperature from room
temperature to about 500C. The residual ~eight when the above
described high molecular wei:ght compound containing a low
molecular weight compound soluble in acetone is. heated under
vacuum, is shown ~n Figure 3. As seen from Fi.gure 3, the weight
decrease becomes large above 200C and at a temperature of about
5Q0C the weight decreas.e becomes e~en larger. The reason why
the weigh.t decrease of th.e high.molecular wei~ght co~pound
containing the low molecular weight compound soluhle i.n acetone
becomes larger ab.ove 2Q0C, is based on ~he fact that the lo~
molecular ~eigh.t compound contai.ned in the high molecular
wei.gh.t compound volati`lizes.
-22-
7'~Z~
It has been found that when a larger amount of low
molecular weight compoun~ is contained and the softening point
of the organic silicone high molecular weight compound is lower
than 50C, the content can be decreased by the following means.
In the first means, the organosilicon high molecular
weight compound in which silicon and carbon are the main skeleton
components, is treated with a solvent of alcohols, such as
methyl alcohol and ethyl alcohol or acetone to extract the low
molecular weight compounds and to obtain the high molecular
weight compounds having a softening point of higher than 50C.
In the production of spinning solution of the above
described high molecular weight compound, in order to improve
the softening point and viscosity it is possible to add the
above described extracted low molecular w.eight compound to the
high molecular weight compound, which is not extracted and
remains, in such a range that the softening point does not
become lower than 50C.
In the second means, the organosi.licon high molecular
weight compound in which silicon and carbon are the main skeleton
components, is sufficiently aged under vacuum or an atmosphere
of air, oxygen, an inert gas, CO gas, ammonia gas, C02 gas,
a hydrocarbon gas or an organosili.con compound gas, if necessary ~:
under pressure at a temperature range of 5Q-70~C to polymerize
the low molecular weight compounds in the organosili.con high
molecular wei`ght compound and to form the ~igh molecular ~eight
compound having a softeni.ng poi.nt of h.i.gh.ex th.an sac. The
atm.osphere for ef~ecting the aging is, for example, as indicated
above vacuum, air, oxygen, an inert gas:, h~dxogen gas, CO gas,
.. -23-
'7~
ammonia gas, CO2 gas, a hydrocarbon gas or an organosilicon
compound gas and, if necessary the agi.ng can be effected under
pressure. When air, oxygen or ammonia gas is used, oxygen or
nitrogen atom has cross-linking function, by which the low
molecular weight compound is polymerized, so that these gases
can be advantageously used. The above described various gas
atmospheres are not always limited to one kind of gas and a
mixed atmosphere of two or more gases may be used but in this
case it is not desirable to mix gases~ which react with each
other.
The above described aging may be carried out under
vacuum, atmospheric pressure or pressure; under vacuum an
evaporation of the low molecular weight compound is promoted
while under pressure the low molecular weight compound having
a molecular weight of less than 1,00.0 contained in the organo-
silicon high molecular weight compound is not volatilized but is
polymerized to form the high. molecular wei.ght compound, so that
the yield of production is impro~ed.
When the temperature for aging the aboye described
organosilicon hlgh molecular weight compound is. lo~er than 50C,
the pol~merizati.on reaction is extremely 510w and such a temper-
ature is not economic. On the other hand, if s:ald temperature
exceeds 70ac, the above described h.igh molecular ~eight
compound is ~lolently decomposed, 50 that the. aging tempexature
must be withln a range of 5a-7~0c. The preferred tempexature
range for agi`ng vari`es depending upon the kind of atmosphere,
the kind of startlng material, the a~erage ~oleculax ~ei~ht o~
starting matexlal and the: like. Howe~er, under an a~r, oxygen
-24-
7~
or ammonia gas atmosphere, the desirable result can be obtained
at a temperature of 80-300C while under an inert gas, hydroyen
gas, CO gas, CO2 gas, a hydrocarbon gas, or an organosilicon
compound gas atmosphere, the preferable result can be obtained
at a temperature of 120-450C.
The required time for said aging relates to the aging
temperature and when the temperature is high, the required time
may be short; at a high temperature, decomposition and an
excessive cross-linking reaction occur so that when the heatlng
temperature is high, it is necessary to effect the heating for
a short time. Ho~-ever, when the heating temperature is low, the
heating time must be long. A better result can be ob.tained,
when the heating i,s effected at a lo~ temperature for a long
time and in general, the required time of 0.5-lQ0 hours is
preferred under the a~ove described preferred temperature.
The a~ove described aging vari:es the molecular weight
of the organosili.con hi.gh -molecular weight compoun~ and can
make the spinning easy and the strength of the spun fi.lament
can be improved.
2u In the thi:rd means, the low molecular wei.ght compound
can be removed ~y dist~llatlon. This distillation includes
distillati.on under atmospheri.c press~ure where m the distillation
temperature can be high. H.o~e~er, in the di$ti11ation under
vacuum the molecular weight compound can be. removed at a lower
temperature than that ~n the dist~llation under atmospheric
pres.s,ure. The distillation temperature is preferred to be
lQû,-500C and when the distillation is effected at a temperature
of lower than laOC, th.e low molecular wei.ght compound cannot
: -25-
be satisfactorily removed, while when the temperature is higher
than 500C, the distillation temperature is too high and the
polycondensation reaction proceeds to such an extent that the
obtained organosilicon high molecular weight compound cannot
be spun into filament.
In the present invention, when the organosilicon high
molecular weight compounds obtained from the above described
various organosilicon compounds by the well known polycondensa-
tion process, have a softening point of higher than 50C, such
organosilicon high molecular weight compounds can be directly
used as the spinning material. Such organo~ilicon high molecular
weight compounds are dissolved in a sol~ent or melted by heating
to form a spinning solution, which is spun into a fiber. The
resulting fibers are preliminarily heated at a temperature of
350 to 800C under vacuum and the preliminarily heated fibers
are baked at a temperature of 80Q-2,000C under at least one
non-oxidizing atmospheres to produce si.li.con carbide fibers
having high strength. according to the present invention.
The organos~l~con high molecular ~eight compounds
having a low content of the a~ove described molecular weight
compounds are dissol~ed in a solvent capa~le of dLssol~ing the
organosilicon high. molecular weigh.t compounds:, ~or ex~mple,
~enzene, toluene, xy~lene, ethylbenzene, styrene, cumene, pentane,
hexane, octane, cyclopentadiene, cyclohexane, cyclohexene,
methylene chIoride, chIoroform, carbon tetrachloride, 1,1-
dichloroethane, 1,2-d~chloroethane, meth.ylchloroform, 1,1,2-
tri.chloroethane, hexach.Ioroethane, chlorobenzene, dichloro-
henzene, ethyl ether, dioxane, tetrah.ydrofuran, methyl acetate,
-26-
, ,
7~i6
ethyl acetate, acetonitrile, carbon disulfide and the like, to
produce a spinning solution, which is filtered to remove harmful
substances in the spinning, such as macrogel, impurities and
the like, and then the spinning solution is spun in a dry
process by means of a spinning apparatus for synthetic fibers
generally used and the spun fibers are subjected to a large draft
to obtain fine fiber.
In this case, when the atmosphere in the spinning tube
of the spinning apparatus is a mixed atmosphere of the saturated
vapor of at least one of the above de~cribed solvents with air
or an inert gas, heated air, a heated inert gas or steam, the
solidification of spun fibers in the spinning tube can ~e
controlled.
In additi.on to the production of the spinning solutlon
by using the above des:cribed solvents, the above described
organosilicon high molecular weight compounds having a softening
point of higher than 50C can be heated and melted and the melt
is filtered to remove the harmful subs:tar:ces in the spinning,
~ such as macrogel, impurities and the like and the thus treated
20 melt is spun through the a~ove described s:pinning apparatus. The
temperature of the melt in the spinni.ng varies depending upon the
softening point of the organosilicon high molecular weight
compounds., but the temperature range of 5Q-4QClC i5 adYantageoUS.
In the above descri~ed spinn~ng apparatus, ~f neces$ary, there
is provided ~i.th. a spinning tube and in the spinning tube in
wh.ich. atmosphere i.s air, an inert gas., a h.eated air, a heated
inert gas or steam, a large draft, applied to obtai.n fine fibers.
The spinning rate in s~id melt spinning vari.es depenaing upon an
-27-
avera~e molecular we.ight, a molecular weight distribution and
the molecular structure of the organosilicon high molecular
weight compound, but is preferred to be 50-5,000 m/min.
The spun fibers are sub]ected to the preliminary
heating at a temperature of 350-800C under vacuum. The object
of the preliminary heating is as follows. The spun fibers
contain a small amount of the low molecular weight compounds.
The low molecular weight compounds formed in the polycondensation
reaction and by the decomposition reaction owing to heating
can act as a solvent which dissolves the spun fibers and if a
baking at a high temperature as explained hereinafter is carried
out in such a way that these low molecular weight compounds
are present, the spun fibers are dissolved and the shape of the
fibers cannot be kept. Accordingly, these lo~ molecular weight
: compounds should be evaporated by the preliminary h.eating.
The time of the preliminary heating should be enough to fully
remove these low molecular weight compounds.
In the above descr;~ed preli~inary heati.ng under
vacuum, evaporation of the easi.ly volatile components becomes
violent a~ove 5Q0.C and th~ evaporation be.comes ~eak at about
700C as seen from Fi`gure 2. ~hen th.e baking at a high temper-
ature is carried out after the low molecular ~ei.~h.t compounds
have been evaporated and removed by the prelimi.naxy heating,
the reaction for forming ~-ilicon carb.ide favourably p~oceeds and
the silicon car~ide f~ers h.aving a h.igh:s;txength can be
obtained.
In the b.aking at a high temperature, th.e. original
formation of silicon carbide i.s obs:erYe.d from ab.out 8aQC by
-28-
~ ~ 3J~
X-r~y diffraction as shown in Eigure 4. When the temperature
is further raiscd, tlle crystal of sil.icon carbide grows.
However, when the temperature exceeds 2,000C, silicon carbide
decomposes, so that the temperature in the baking at a high
temperature must be 800-2,000C.
In the practice of the pxesent invention, baking at a
high temperature may be effected under various atmospheres.
After the preliminary heating up to about 800C under vacuum
in order to evaporate the easily volati.le components, the baking
effected at a temperature of 800-2,000C under an inert gas,
CO gas or hydrogen gas atmosphere can provide silicon carbide
fibers having a high strength.
The tensile strength when the si.licon carbide fibers
are heated at a temperature of 700-2,aQaC is shown in Figure 5
and the heating at a temperature of ltQOa-1,5QQC provides the
maximum tensile strength. The result af X-ray diffraction shows
that the state of amorphous, semi-amorphous, or ultxa fine
grain silicon carbi.de is maintained up to 1,50QC and ~hen the
temperature exceeds 1,50QC, silicon c~rbi.de crys.tal grows, so
that the strength decreas~es. Accordin~l~, hi~h ten~ile strength
can be obtai.ned ~n the: for~ of the amorphous, s.emi.-amorphous
or ultra fine grain s:ilicon car~ide.
Furthermore, it has been found th~t ~hen the spun
fibers are h.eated under an o~dizi.ng atmosphere at a lo~ temper-
ature of 50-5aQaC, p~rticularly, 15Q-3QQC fox seyeral mi.nutes
to lQ houxs pr~or to the: preIiminary-heatin~, a thin ~xi.de layer
is formed on the surface of the fibexs and the fihers are not
me.lted at the succeeding preI~inary he~ting and the stickiness
-29-
3~2~
of mutual fibers can be prevented. If such a heating treatment
at a lo~ temperature under an oxi.dizing atmosphere is carried
out, it is not always necessary to effect the succeeding
preliminary h~ating treatment under vacuum and the preliminary
heating can be carried out under a non-oxidizing atmosphere,
such as an inert gas, CO gas, hydrogen gas, a hydrocarbon gas
or an organosilicon compound gas.
The atmosphere in the above described heating at a low
temperature is preferred to be oxidizing gaseous atmosphere
selected from the group consisting of air, ozone, oxygen,
chlorine gas and bromine gas. If the heating under the above
described gaseous atmosphere is carried out at a temperature
of lower than 50C, said oxide layer cannot ~e formed on the
fibers, while at a temperature of higher than 40ac the oxida-
tion of the fibers is too great, so th.at the temperature range
of 50-400C is preferable. The time for such. a heating step
depends upon the temperature and is from several minutes to
10 hours.
As the atmosphere for this heating step an aqueous
solution of KMnO4, K2Cr2O7, H2O2 and the oth.er inorganic
peroxides can be used and in this case, the temperature is
preferred to ~e from room temperature to lQ0C and the time is
preferred to be Q.5 to 10 hours.
When a tensi.on is applied in th.e a~ove described
heating under an oxi.dizing atmosphexe, a satisactoxy amount of
tens.ion i.s such an amount that the ~ave-foxmed shri.nkage of the
spun fi~ers: can be preyented ~ut In order to practically effect
th.e heating at a lo~ tempexature unde.r a tensïQn, a tension of
-30-
7~
0.001-5 Kg/mm provides a good result. If a tension of less
than 0.001 Kg/mm2 is applied, it is impossible to maintain such
a tension that the fiber does not loosen, while if a tension
of more than 5 Kg/mm2 is applied, the tension is too large and
the fibers are broken, so that the tension is preferred to be
0.001-5 Kg/mm2.
When the low molecular welght compounds are evaporated
by the above described preliminary heating, the fibers shrink and
bend but this bending can be prevented by applying a tension
during the preliminary heating. In this case, the tension may
be in such an amount that even if the fibers shrink in the above
described preliminary heating, the formation of ~ave-shaped
bending can be prevented and a good result can be obtained
within a range of 0.001 to 20 Kg/mm . If a tension of less
than 0.001 Kg/mm2 is applied to the filaments., it is impossible
to prevent the loosening of the fibers, wh.ile wh.en a tension of
more than 20 Kg/mm2 is applied, the tensi.on is too large and
the fibers are broken, so that the tension appli.ed to the fibers -~
during the preliminary heating ls preferred to be O.Q01-20
Kg/mm .
It has ~een found that if a tensi.on of 0~001 to 100
Kg/mm is applied to the fibers in th.e above. described baking
at a high temperature of 80Q-2,000C, the ori.entati.on of silicon
carbide crystal in the fibers is improved and that the strength
of th.e fibers ~aked at a temperature of hi.gher than 1,5aOC
under a tensi.on i.s appreci.abIy higher th.an th.at of the fibers
baked under no tension load. Wh.en th.e tensi.on i.s. le$s than
O.Q01 Kg~mm2, the effect of tension i.5 not o~$eryed, ~hile even
-31-
'7~
if a tension of more than 100 K~/mm2 is applied, the effect
does not vary and wllen the bakin~ is effected under a tension
of 0.01~50 Kg/mm2, the stren~th becomes maximum. When the baking
temperature is low, e.g. 800C, the tension to be applied to
the fibers is low, for example, 0.1 Kg/mm2. When the baking
temperature is raised and at the same time the tension is
gradually increased, for example, when the baking is completed
under a tension of 30 Kg/mm2, the orientation of silicon carbide
crystal is improved and silicon carbide fibers having a high
strength can be obtained.
In the method of the present invention, the stress
to be applied during baking is obtained by tension, twisting
or bending.
With respect to silicon carbide fibers obtained by
baking the fibers at a high temperature under no stress and
obtained by baking the fibers at a high temperature under a
stress, the tensile strengths are compared hereinafter.
Fibers having a diameter of about 10 ~, after being .
subjected to the preliminary heatlng, were baked under a tension
of 5 Kg/mm2 and other fibers having the same diameter, after
being subjected to the preliminary heating, were baked under
no tension. The diameter of these silicon carbide fibers does
not vary. However, the tensile strengtn of the silicon carbide
fibers baked under no tension suddenly decreases from (a baking
temperature of~ ab.out 1,500C as shown in Figure 6, while the
tensile strength reduction Gf the s~illcon carbide fi~ers baked
under a tens:i.on of 5 Kg~mm is small even at a temperature of
hi.gher than 1,50.0C as shown in Figure 7 and si`.li.con carbide
fibers having a high strength can thus be obtained.
When the baking at a high temperature is effected
while applying ultrasonic wa.ve to the fibers, the strength of
the obtained silicon carbide fibers is improved. The ultrasonic
wave having a frequency of 10 KHz to 30 MHz can be advantageously
used. If an ultrasonic wave of less than 10 KHz is used, the
` object of improving the strength cannot be attained, while if
an ultrasonic wave of more than 30 mega~lz is used, the frequency
is too large to improve the strength. The preferred frequency
of the ultrasonic wave to be applied in the present invention
is 20 KHz to 5 MHz. The strength of the silicon carbide fibers
baked at a temperature of 800-2,000C ~hile applying ultrasonic
wave by means of an ultrasonic generator having an output of
100 W at a frequency of 500 KHz is sho~n in Figure 8 and as seen
from Figure 8 the silicon carbide fibers havi,ng a constant
strength can be obtained withi.n a temperature range of 1,800
to 2,000C.
If the above described tensi.on and ultrasonic ~ave
~, are simultaneously applied to th.e si.licon car~ide fibers, the
orientation of silicon carbide crystal is- appreci.ably improved,
crystal growth.occurri,ng in a uni,form direction. ~i.li.con carbide
fibers having an excellent orientati.on of si`,licon carbide crystal
can thus be obtained. As an em~odiment of b,aking at a high
temperature under both the function of the. tension and the
ultrasonic ~ave, a relation of the tens~le strength.to the baki.ng
: temperature when the fibers having a diameter of 10. ~ are baked
at 8Q0-2,QaOQC, with applicati.on of a tension of 5 Kg/mm,2 and an
ultrasonic waYe of an output of lQQ ~at 30Q KH:z, is shown in
-33-
~ J~t~
Figure 9. As seen from ~i~ure 9, even in silicon carbide fibers
baked at about 2,000C the decrease of tensile strenyth is not
substantial and silicon carbide fibers having a high strength
can be produced.
The orientation of silicon carbide crystal in silicon
carbide fibers obtained by baking the fibers under a tension was
determined by electron diffraction. As such an embodiment, the
electron diffraction of silicon carbide fibers baked at 2,000C
under a tension of 5 Kg/mm2 is shown in ~igure 10. The electron
diffraction of silicon carbide fibers baked at 2,0~0C under
no tension is shown in Figure 11. In the above described electron
diffraction photographs (Figures lQ and 11), th.e innermost
diffraction ring is formed based on (111) plane of silicon
carbide crystal, but in the case of the bak.ing treatment under
no stress, the orientation of the s-ilicon carhide crystal in
silicon carbide fibers is irregular as shown in Fi.gure 11 and the
crystals oriented in ~11 directions are mixed, so that the
strength of the electron diffraction is uni.form in all directions
of 360 and the diffraction ring is uniform in the electron
diffraction strength in all porti.ons of the ring and therefore
the blackness of the diffraction ring is uniform, ~hi.le, as shown
in Figure 10 in the electron diffracti.on of the silicon carbide
fibers baked under a tensi.on, the. ri.ng i.5 larger in the diffrac-
tion strength only at a part of the dif~ractiQn ring, so that the
blackness of the di~f$ract~on ring is very~deep at a part and it
can ~e seen that the orientat~.on of the silicon caxbide crystal
in the fibers is very go~d. Since the orientation of the silicon
carbide crystal is h;~gh., the strength o$ the crystclline silicon
-34-
, .
7t~
carbide fibers obtained by baking under a tension does not
significantly decrease as compared with the strength of non-
crystalline silicon carbide fibers obtained by baking at a
temperature of lower than 1,500C.
In the present invention, it has been found that the
silicon carbide fibers obtained by the preliminary heating at a
low temperature and the baking at a high temperature often
contain free carbon. However, when the fibers are burnt at a
temperature of 600-1,700C under an oxidizing atmosphere, the
free carbon can be oxidized and removed. I:f such a burning under
an oxidizing atmosphere is effected at a temperature of lo~er
than 600C, the free carbon cannot be oxidized, while ~hen said
burning is effected at a temperature of higher than 1,700C, the
free carbon can be easily oxidized, but a reaction for forming
SiO2 proceeds, so that such temperatures are not desirable.
The time for oxidizing the free carbon depends upon the oxidizing
temperature and the already treated temperature of the fibers.
For example, wh.en the fibers burnt at 1,200C i~ treated under
~ an oxidizing atmosphere at 800C, 0.1-3 hours is preferable and
:~ 20 in general, it is prefer~ble to effect such a treatment at a low
- temperature for a relati~ely long time.
The silicon car~ide fi~ers according to the present
invention can be used i.n monofil~ment, yarn, robbing and cable.
The silicon carbide fibers~ according tQ the present
invention are mainly formed from ultra fine grains of e-~ic
: crystal and the average grain sizes of the crystals of the fibers
obtained by bak~ng at a temperature of l,lOUaC, 1.,3Q0.C and
1,500C under vacuum are about 2Q A, 30 A, and 80 A and the
-35-
, . . . .
`
`7~
silicon carbide ~i~ers composed of such ultra fine grains of SiC
crystals have never been heretofore known.
The tensile strength of the silicon carbide fibers
according to the present invention is 200-800 Ky/mm2 and Young's
modulus is 10-40 ton/mm2. The tensile strength and the Young's
modulus were determined with respect to silicon carbide fibers
obtained by baking at 1,300C under vacuum and the result is
shown in Figure 12. The tensile strength and the Young's
modulus become larger, as the diameter of the fibers becomes
smaller. Furthermore, as the diameter is smaller, the silicon `
carbide fibers become more flexible.
The tensile strength and Young's modulus at a high
temperature of the silicon carbide fibers according to the
present invention were determined up to a temperature of 1,400C
under vacuum and the obtained results are shown in Figure 13.
As seen from Figure 13, the tensile strengtn and the Young's
modulus of the silicon carbide fibers according to the present
invention do not vary at all from room temperature to 1,400C
and the silicon carbide fibers of the present invention are
inorganic fibers whi:ch can be satis;factorily used from room
temperature to 1,400C.
The silicon carbide fibers of the present invention
are high in corrosion resistance and, in fact/ are not corroded
at all, even if the f~bers are imme~sed in hot hydrofluoric acid,
a hot mixture o~ hydrofluoric acid and sulfuric acid, or hot
aqua regia and the tens-~le strength and Young's modulus before
and after the immersi.ng do not var~ at ~11.
The antioxi.dati.on ch.aracteri.stics of fibers according
.
-36-
to the present invention was determined by heating the silicon
carbide fibers of the present invention at 1,200C for 100 hours
in air but the fibers were not substantially oxidized and the
tensile strength and the Young's modulus before the heating at
1,200C were unaffected even after the heating at 1,200C.
The Young's modulus of the silicon carbide fibers
according to the present invention is higher than that of the
carbon fibers having the highest Young's modulus among various
presently known fibers and is about 6 times that of the glass
fibers.
In the diffraction curve determined by X-ray diffraction
method with respect to tne silicon carbide fibers obtained by
baking at 1,500QC under vacuum, there are three diffraction peaks
of 2~~36, 60 and 72 as shown in Figure 14 an~ it can be seen
that the silicon carbide crystal in the fibers is ~-5iC crystal.
Furthermore, the silicon carbide fibers baked at the
above described various temperatures were measured by Pin hole
method X-ray diffraction and the obtained diffraction photographs
are shown in Figures 15 to 17.
Figure 15 is the diffraction ph~tograph of the silicon
carbide fibers baked at 1,200C under ~acuum, Figure 16 is the
diffraction photograph of the silicon carbide fi~ers baked at
1,300C under vacuum and Figure 17 is the diffraction photograph
of the silicon carbi.de fi~ers baked at l,5QQC under vacuum.
The ring in the most inside among th.~ di.ffraction rings
in the di.ffraction photograph is formed based on ~111). plane of
~-SiC crystal and as~ the bak~ng temperature ~i`s raised, the
diffraction r~ng becomes cleax and this sho~s the gro~th.of
-37-
'79,'~
~-SiC crystal. Since the diffraction spot is not observed in
the diffraction ring, it is apparen-t that ~-SiC crystal is very
small grain.
The average grain size of SiC crystal can be calculated
from the following formula:
O.9 x
,g X COS~
L : average grain size (A)
A : X-ray wave length (A)
~ : width at half-maximum intensity (RadlanJ
~ : Brag angle
The grain size of SiC crystals in ~ilicon carbide
fibers baked at various te~peratures was calculated from the
above formula. The average grain size of SiC crystal in tne
silicon carbide fibers baked at 1,200C under vacuum is about
20 A, the average grain size of SiC crystal of the silicon carbide
fibers baked at 1,300C under vacuum is about 30 A and the
: average grain size of SiC crystal of the silicon carbide fibers
baked at 1,500C under vacuum is about 80 A. A relation of the
baking temperature to the average grain size of SiC crystal in
20 the silicon carbide fi~ers is- shown in Tigure 18 and as the
baking temperature hecomes higher, the average grain size of
SiC crystal becomes larger.
~ n the silicon carbide f~bers according to the present
invention, as the baki.ng temperature in the production becomes
higher, the tensile strength decreases and the average grain
-38-
6~ 6
size of the crystal becomes larger. A relation of the baking
temperature to the tensile strength and a relation of the tensil.e
strength to the average grain size if SiC crystal are shown in
Figures 18 and 19, respectively. From these Figures, it is
apparent that the grain size of the crystal and the tensile
strength are in an inverse relationship and the reason why the
silicon carbide fibers according to the present invention are
very high in the tensile strength is presumably based on the
fact that the silicon carbide fibers are constituted of the
ultra fine grain crystals heretofore unknown.
SiC crystal in the silicon carbide fibers according
to the present invention, which was obtained by baking at
1,500C under vacuum, was okserved by an electron microscope
of an ultra high voltage of an accelerating voltage of 1,000 KV
and the obtained photographs are shown in Figures 20-23.
Figure 20 is a photograph of the silicon carbide fiber taken in
5,000 magnification and this shows that the s:urface of the
fiber is very smooth. Figure 21 shows a ph~tograph of the
silicon carbide fiber taken in 20,000 magnification and since
the electron penetrates only the thin peri.phery portion, an
image of SiC crystal grain can be observed and a verY small
number of the grains having 100-1,000 A ~re present between the
grains of an average grain size of about sa A which are
distributed in the entire of the fiber. Figure 22 shows a
photograph of a cut end of the silicon carkide fiber taken in
20,000 magnification and a very small num~er of the large grains
hayi:ng lOQ-l,OOQ A are pres.ent between the gra~.ns. h.aYing about
50`A which are di.stribute~ in the entire of the fiber. Figure 23
.
-39-
` 7'32~
is a photograpll of a cut end of the silicon carbide fiber taken
in 50,000 magnification and the grains having about 50 A are
uniformly distributed and a very small number of large grains
having 100-1,000 A are present between said ultra fine grains,
but it can be seen that the grains mainly constituting the
silicon carbide fiber are the ultra fine grains having about
50 A.
That is, the silicon carbide fibers according to the
present invention are constituted with ultra fine grain of
crystals.
The present invention will be explained in more detail.
For a better understanding of the invention, reference
is taken to the accompanying drawings, wherein, as indicated
above:
Figure 1 is a diagram of an e~bodiment of apparatus
for producing the organosilicon high molecular ~eight compounds;
Figure 2 shows: a relatlon of the residual weight to
the heating temperature when the hi`.gh l-~lolecuiar ~eight compounds
containing low molecular weight compounds: are heateai
; 20 Figure 3 shows a relation of the res.idual weight to theheating temperature when the high molecular wei.ght compounds
containing low molecular weight compounds are heated under vacuum;
Figure 4 shows X-ray di.ffractl.on p~tterns w.hen the
silicon high molecular weight compound fib.ers are heated at
various temperatures;
F;gure 5 sho~s a relation of the tensile s.trength to
the heating temperature when the spun fibers. according to the
present invention are h.eated from 7~QC to 2,OQQC;
-40-
Figure 6 shows a relation of the tensile strength to
the baking temperature when the spun fibers are baked under no
tension;
Figure 7 shows a relation of the tensile strength to
the ba.~ing temperature when the spun fibers are baked under a
tension;
Figure 8 shows a relation of the tensile strength to
the baking temperature when the spun fibers are baked while
applying ultrasonic wave;
Figure 9 shows a relation of the tensile strength to
the baking temperature when the spun fibers are baked while
applying a tension together with ultrasonic wave;
Figures 10 and 11 show electron diffracti.on photo-
graphs of the silicon carbide fibers obtained by baking under
a tension or no tension, respectively;
Figure 12 snows relations of the t~nsile strength
and the Young's modulus to the diameter of th.e silicon carbide
fiber according to the present invention;
Figure 13 is a diagram showing vari.ations of the
tensile strength and the Young's modulus based on temperature
of the silicon carbide fiber according to the present invention;
Figure 14 shows an X-ray diffracti.on pattern of the
; silicon carbide fiber baked at 1,5QQC;
Figures 15-17 are X-ray di.ffraction photographs of
Pin hole method of the s-ilicon carbide fiber of the present
invention;
Figure 18 is a diagram showing relations of the average
grain size of SiC crystal and the tensi.le strength of the si.licon
-41-
.
'7~,~$
carbide fiber of the present invention to the baking temperature;
Figure 19 is a diagram showing a relation of the
tensile strength to the average grain size of SiC crystal of
the silicon carbide fiber of the present invention;
Figures 20-23 show photographs obtained by observing
SiC crystal in the silicon carbide fiber of the present
invention through a super high voltage electron microscope; and
Figure 24 is a diagram of an embodiment of apparatus
for continuously effecting the method of the present invention.
The following Examples are given for the purpose of
illustration of this invention and are not intende~ as limita-
tions thereof.
Example 1
10 g of dodecamethylcyclohexasilane [(Me2Si~6] was
fed in an autoclave and air in the autoclave was purged with
argon gas and the polycondensation was effected at 400C under
a pressure of about 40 atmospheres for 48 hours to obtain the
organosilicon high molecular weight compounds of the present
invention. The formed high molecular weight compounds were
permitted to cool at room temperature and then these compounds
were admixed with ether to form ether solution. Said ether
solution was taken out from the autoclave and ether was evaporated
to obtain 6.6 g of a solid product. This solid product was
dissolved in benzene and the solution was spun into fibers.
The benzene solu~le product had an average molecular weight
of more than l,5QQ.
lQ g of this organosilicon hi~gh moleculax weight
compound was dissolved in lOQ cc of n-hexane and to the resulting
-42-
7$,~
solution was added 300 cc of acetone and the insoluble portion
was about 60%. This insoluble portion was dissolved in benzene
and the resulting solution was spun in a dry process at a
spinning temperature of 20C at a spinning rate of 100 m/min. to
obtain the organosilicon high molecular weight compound fibers
having a diameter of 10 ~. The fibers were fully dried and then
subjected to the preliminary heating to a temperature of 800-
1,000C in about 2-48 hours, in average time of 12 hours under
vacuum (1 x 10 3 mmHg) to obtain the fibers having black metal
luster in a yield of 40-60%. The thus treated fibers were
baked up to 1,800C under argon atmosphere to obtain silicon
carbide fibers.
A relation of the residual weight to the heating
temperature up to the above descri~ed 1,000C is shown in
; Figure 2.
The tensile strength of the fibers heated to 1,800C
was 98 Kg/mm2 and the tensile strength of the fibers heated to
1,000C was 810 Kg/mm2 and Young's modulus was 34 ton/mm2.
Example 2
10 g of linear polydimethylsilane
Me Me
[ ~
Me Me
produced from dimethyldichlorosilane was charged in an autoclave
and heated under argon atmosphere at 400C under a pressure of
5~ atmospheres for 48 houxs. The reaction product ~as dissolved
in ether and the solution obtained ~y remoYing the insoluble
-43-
: : : : .
.
~'7~
portion was evaporated to obtain 4.3 g of a solid product. This
solid product had an average molecular weight distribution of
500-15,000 and was dissolved in 50 cc of hexane. The resulting
solution was mixed with 200 cc of acetone to obtain precipitates.
The precipitate was dissolved in benzene and the solution was
spun in a dry porcess at 25C into fibers having a diameter
of 10 ~.
The thus obtained fibers were heated gradually to
1,000C in 10 hours under vacuum. The tensile strength of the
fibers was 723 Kg/mm2 and Young's modulus was 36 ton/mm2.
Example 3
10 g of poly(dimethylsiltrimethylene),
ICH3
[ Si - CH2CH2CH2 ]n'
CH3
was dissolved in 100 cc of ben~ene~ and the resulting solution
was mixed with 400 cc of acetone to obtain 68 g of precipitate.
The precipitate was dissolved in benzene, and the resulting
solution was spun in a dry process at 30C into fibers having
a diameter of 10 ~. The spun fibers were fully dried and then
heated gradually from room temperatur to 800C in 4 hours under
vacuum to obtain silicon carbide fibers having metal luster
in a yield of 59.8%. The resulting silicon carbide fibers had a -
strength of 610 Kg/mm2 and Young's modulus of 29 ton/mm2. The
fibers were placed in a graphite crucible and ~aked up to
1,800C under a ti~ghtl~ sealed condltion. The thus treated
fibers had a tensi`le strength of 80 Kg~mm2.
-44-
7'~
Example 4
50 ~ of poly(phenyleneoxysiloxane) was dissolved in
300 cc of benzene, and then 500 cc of acetone was added to the
solution to obtain precipitates. The precipitates were
dissolved in benzene, and the resulting solution was spun in a
dry process at a spinning temperature of 50C at a spinning
rate of 150 m/min. to obtain fibers having a diameter of 10 ~.
The fibers were heated from room temperature to 800C in 6 hours
under vacuum (1 x 10 3 mmHg), and the heat treated fibers were
further heat treated from 800C to 1,800~ under helium atmos-
phere to obtain silicon carbide fibers. The fibers had a
tensile strength of 89 Kg/mm2, and even when the fibers were
kept in air at 1,500C for 100 hours, the fibers did noi change
the weight. Therefore, the fibers had excellent oxidation
resistance.
Example 5
30 g of poly(dimethylsilphenylene),
~- Si ~3
was dissolved in 200 cc of benzene, and the resulting solution
was mixed with 500 cc of acetone to obtain 24.5 g of precipitate.
The precipitate ~as dissolved in benzene, and the resultlng
solution was spun in a dry process at a tempera~ure of 40C
to obtain fibers having a diameter of 10 ~. The spun fibers
were heated from room temperature to 8Q0C in 4 hours under
vacuum to obtain fi`bers in a y~eId of 65%. The fibers ~ere
.~
-45-
',
'`'7'~
further hea~ treated from 800C to 2,000C under helium atmosphere
to obtain f.ibers having a tensile strength of about 75 Kg/~,m2.
Even when the fibers were kept in air at 1,500C ~or 100 hours,
the fibers did not change the weight, and the fibers had very
excellent oxidation resistance.
Example 6
lO g of dodecamethylcyclohexasilane was fed in an
autoclave and air in the autoclave was purged with argon gas
: and the polycondensation reaction was effected at 400C for
48 hours under a pressure of 40 atmospheres. After completion of
the reaction, the polycondensation product was permitted to
cool at room temperature, and then added with ether to form
ether solution. The ether solution was taken out from the
autoclave and ether was evaporated to obtain 6.6 g of a solid
high molecular weight compound having an average molecular
weiyht of about 1,800 and containing 4Q% of acetone-soluble
low molecular weight compounds. The solid high molecular weight
compound was heated and aged at 300C for 8 hours while slowly
stirring under atmospheric pressure in argon atmosphere to
obtain an organosili.con hi.gh molecular weigh* compound having
an average molecular weight o~ about 2,100.
The resulting organosilicon high molecular weight
compound was dissolved in benzene~ and the benzene solution
was spun in a dry process to obtain fi~ers. having a diameter of
about lQ ~. The fihers ~ere gradually heate.d from room
temperature to 80.0C in 6 h.ours under vacuum (l x lO 3 mmHg~
to effect the prelim~nar~ heating of the fi.bers, and then baked
up to l,80QC to obtai.n silicon carbi.de fi.hers.
-46-
~L~Lf;~'7~26
The tensile strength of the fibers heated to 1,200C
was 630 Kg/mm and that of the fibers heated to 1,800C was
85 Kg/mm2.
Example 7
The same solid high molecular weight compound as
obtained in Example 6 was heated and aged at 250C for 3 hours
while slowly stirring in air to obtain an organosilicon high
molecular weight compound having an average molecular weight of
about 2,300. The resulting organosilicon high molecular weight
compound was dissolved in xylene, and the xylene solution was
heated at 42C and spun into fibers having a diameter of about
10 ~. The fibers were gradually heated from room tempexature
to 800C in 6 hours under vacuum (1 x 10 3 mmHg~ to effect the
preliminary heating of the fibers, and ~ihers having a diameter
of about 8 ~ were obtained. The preliminarily heat treated
fibers were baked up to 1,800C under argon atmosphere to obtain
silicon carbide fibers having a tensile strength of 93 Kg/mm2
and Young's modulus of 38 ton/mm2. The tensile strength of
the fibers baked at 1,000C was 740 Kg/mm2. When the fibers
were kept at 1,500C $or 10~ hours in air, the fi~ers dld not
change the weight.
Example 8
10 g of linear polydimethylsilane,
Me Me
Si~,
Me Me
synthesized from dimethyld~chlorosi.lane was fed in an autoclave,
-47-
37~'' b ~
and air in the autoclave was purged with argon, and the poly-
condensation was effected at 400C for 48 hours under a pressure
of SO atmospheres. The resulting polycondensation produc~ was
dissolved in ether, and ether-insol~le portion was removed
from the ether solution, and ether was evaporated to obtain
4.3 g of a solid high molecular weight compound having an
average molecular weight of about 7,500. The compound was
heated and aged at 240C for 2 hours under atmospheric pressure
in gaseous ammonia atmosphere while slowly stirring to obtain a
high molecular weight compound having an average molecular
weight of about 8,400. The resulting high molecular weight
compound was dissolved in benzene, and the benzene solution was
spun into fibers having a diameter of about lO ~. The fibers
were gradually heated from room temperature to 800~ in 4 hours
under vacuum (1 x 10 3 mmHg~ to effect the preliminary heating
of the fibers. The resulting fibers had a diameter of about
8 ~. The preliminarily heat treated fibers.were further baked
up to 2,000C in a graphite crucible to obtain silicon carbide
fibers, which had a tensile strength of 95 Kg/mm2. The fibers
baked at 1,000C had a tensile strength of 810 Kg/mm2 and
Young's modulus of 31 ton/mm2.
Example 9
Poly(diphenyleneoxysiloxane~ havin~ an a~erage
molecular weight of ll,OQQ was heated and aged at 350C for
3 hours under a press~re of 1 atmosphere.s in hydrogen atmosphere
while slowly s:ti`rri.ng to obtain a hi`gh.molecular weight compound
having an average molecular weight of 14,QOQ. The compound was
dissolved in benzene, and the benzene solution wa~ spun in a
-48-
7~
dry process into fibers having a diameter of about 10 ~. The
fibers were ~xadually heated from room temperature to 800C in
6 hours under vacuum (1 x 10 3 mmHg) to effect the preliminary
heating of the fibers. The resulting fibers had a diameter of
about 8 ~. The preliminarily heat treated fibers were further
baked up to 1,800C under vacuum to obtain silicon carbide
fibers having a tensile strength of 80 Kg/mm2. The fibers baked
at 1,000C had a tensile strength of a~out 780 Kg/mm2 and
Young's modulus of 41 ton/mm2.
~xample 10
Methylchlorosilane was polycondensed according to
Fritz's method [Angew. Chem., 79, 657 (1967)] to prepare a
high molecular weight compound having an average molecular weight
of 1,000. The high molecular weight compound was heated and
aged at 400C for 8 hours under a pressure of 10 atmospheres in
nitrogen atmosphere to obtain a high molecular weight compound
having an average molecular weight of 2,500. The aged high
molecular weight compound was dissolved in xylene, and the xylene
solution was heated at 35C and spun into fibers having a
diameter of about 10 ~. The fibers were gradually heated from
room temperature to 800C in 4 hours under vacuum (1 x 10 3 mmHg)
to effect the preliminar~ heating of the fibers. The resulting
fibers had a diameter of about 8 ~. The fibers were further
baked up to l,800C under argon atmosphere to obtain silicon
; carbide fibers having a tensile strength of 110 Kg~mm2. The
fibers baked at 1,000C had a tensile strength of 750 Kg/mm2
; and Young's modulus of 29 ton/mm2. Even when the fi~ers were
kept at 1,500C for 100 hours in air, the fibers did not change
-49-
the weight.
Exam~le 11
The same high molecular welght compound as synthesized
in Example 10 was heated and aged at 290C for 3 hours under
gaseous ammonia atmosphere. The aged high molecular weight
compound had an average molecular weight of 2,400. The aged
compound was dissolved in benzene, and the benzene solution was
spun into fibers having a diameter of about 10 ~. The fibers
were gradually heated from room temperature to 800C in 6 hours
under vacuum to effect the preliminary heating of the fibers.
The fibers were further baked up to 1,800C under vacuum to
obtain silicon carbide fibers having a tensile strength of
89 Kg/mm2. The fibers baked at 1,000C had a tensile strength
of 780 Kg/mm2 and Young's modulus of 28 ton/mm2.
Example 12
10 g of octaphenylcyclotetrasilane was fed into an
autoclave together with 0.1 g of benzoyl peroxide, and air in
the autoclave was purged with argon gas, and the polycondensation
was effected at 370C for 24 hours under a pressure of about
35 atmospheres. After completi`on of the reaction, hexane was
added to the autoclave, and the po]ycondensation product was
taken out from the autoclave in the form of hexane solution.
Insoluble portion in hexane was filtered off, and hexane was
evaporated to obtain 7.1 g of solid high molecular weight
compounds having an average molecular weight of about 8,000.
The high molecular weight compounds were dissolved in 100 cc of
hexane, and the ~exane solution was added with 4a~ cc of
acetone to obtain 6.3 g of acetone-insolu~le precipitate. The
-5~-
., ' '
:
7~,Z~;
precipitate was dissolved in benzene, an~ the benzene solutlon
was spun in a dry process into fibers having a diameter of
about 10 ~. The fibers were heated from room temperature to
800C in 6 hours under vacuum (1 x 10 3 mmHg) to effect the
preliminary heating of the fibers. The preliminarily heated
fibers were further baked up to 1,400C in a graphite crucible
to obtain silicon carbide fibers having a tensile strength of
350 Kg/mm2 and Young's modulus of 25 ton/mm2.
Example 13
10 g of a mixture of cyclic dimethylpolysilanes having
formulae of (Me2Si)5 and ~Me2Si)6 was fed into an autoclave
together with 0.5 g of azoisobutyronitrile, and air in the
autoclave was purged witn argon gas, and the polycondensation
: was effected at 400C for 12 hours under a pressure of about
80 atmospheres. After completion of the r~action, benzene was
added to the autoclave, and the polycondensation product was
taken out from the autoclave in the form of benzene solution.
In soluble portion in benzene was filtered off and benzene was
evaporated under a reduced pressure to obta~n 4.8 g of solid
high molecular weight compounds having an average molecular
weight of about 7,000. The high molecular weight compounds
were dissolved in 50 cc of h.exane, and to the hexane solution
was added 200 cc of acetone to obtain 3.~ g of acetone-
insoluble precipitates. The precipitate was di~ssolyed in benzene,
and the benzene solution was spun i.n a dry proces.s. into fibers
having a di.ameter of about 10 ~. The ~ibers were gradually
heated from roo~ temperature to 8QQC in 6 hou~s under yacuum
(1 x 10. 3 mmHg~ to effect the prel~m~nary~heat~ng o~ the fibers.
The preliminarily heated :Eibers were furtner baked up to 1,800C
under vacuum. The tensile strength of the fibers baked at
1,300C was 7S0 Kg/mm2, and that of the fibers baked at 1,800C
was 95 K~/mm2. Even when the fibers baked at 1,300C were kept
at 1,500C for 120 hours in air, the fibers did not change the
weight.
Example 14
10 g of a mixture of cyclic dlphenylsilane of the
formula (Ph2Si)4, that of the formula (Ph2Si)5 and linear s
polydiphenylsilane was fed into an autoclave and air in the
autoclave was purged with gaseous nitrogen, and the polycondensa-
tion was effected at 380C for 50 hours under a pressure of
about 60 atmospheres. After completion of the reaction,
benzene was added to the autoclave, and the polycondensation
product was taken OUt from the autoclave in the form of benzene ~.
solution, and the ~enzene solution was concentrated under a
reduced pressure to obtain 6.9 g of solid high molecular weight
compounds. The reSUlting high molecular ~eigh.t compounds .
were dissolved in 50 cc of benzene, and to the ~enzene solution
was added 200 cc of acetone to obtain 4.8 g of acetone~insoluble
precipitates. The precipitate was dissolved in benzene, and
the benzene soluti.on was spun in a dry process into fibers
having a diameter of about 10 ~. The fibers were gradually
heated from room temperature to 8QaC in 6 hours undex vacuum
(1 x 10 3 mmHg~ to obtain black fi~ers h.avi.ng me*allic luster.
The fibers were ~urther baked up to 1,5uQC under helium
atmosphere to obtain sili.con carbide fi.bers havin~ a tensile
strength. of 300. K`g~mm2.
~.
-52-
7~Z~;
Example 15
Fluidized hexamethyldisi.lane was fed into a reaction
column heated to 850C at a feeding rate of 1 Q/hr. together
with argon gas. The starting hexamethyldisilane was subjected
to a decomposition reaction and a polycondensation reaction in
the heated reaction column and formed into high molecular weight
compounds, and at the same time low molecular weight compounds
were formed. A part of the resulting high molecular weight
compounds could be taken out from the heated reaction column.
Major part of the high molecular weight compounds was fed into
a separating column together with the low molecular weight
compounds, and gases and the low molecular weight compounds
were separated from the high molecular wei.ght compounds in the
column. The low molecular weight compound~ were again fed
into the heated reaction column and recycled. The operation was
continued for 10 hours and 5.4 Kg of high molecular weight
compounds having an average molecular w.eight o~ about 3,500 was
obtained.
From 10 g of the resulting high.molecular weight
compounds, ethyl alcohol-soluble portion was. removed by means
of a Soxhlet's extractor to obtain 7.8 g of eth~l alcohol-
insoluble portion, which was used as a spinning material. The
ethyl alcohol-insoluble portion was dissol~ed in xylene, and the
solution was heated to 45C and spun i.nto fibers h.aving a
diameter of about lQ ~. The spun fib.ers: ~ere h.eated from room
temperature to 800.C in 6 hours undex vacuum to effect the
preliminary heat~ng o~ the fibers. The fi~bers ~ere further
bak.ed by h.eati`ng up to 1,3Q~C under axgon atmosph.ere. The
-
-53-
'7~6
tensile strengtll of the baked fibers was 450 Kg/mm and ~oung's
modulus was 27 ton/mm2.
Example 16
Poly(silmethylenesiloxane) having the following formula
and an average molecular weight of about 24,000 was used as a
starting material.
CIH3 CIE~3
[ I i - CH2 - Si - O
CH3 3
A content of the low molecular weight compounds
soluble in acetone contained in this high molecular weight
compound was less than 5% and the softening point of this high
molecular weight compound was 100C. This organosilicon high
molecular weight compound was dissolved in benzene to form a
spinning solution, which was spun into fibers having a diameter
of about 10 ~. The spun fibers were subjected to a preliminary
heating by raising the temperature from room temperature to ~ :.
800C in 4 hours under vacuum (:1 x la 3 mmHg~ and then baked ~:
by heating up to 1,800C under vacuum to obtai.n silicon carbide
fibers having a diameter of about 8 ~. The tensile strength
of the fibers baked at l,000C was a~out 5Q0 Kg/mm2 and the
tensile strength of the f~bers baked at 1,8QQC was about 65
Kg/mm .
Example 17
PolyCsilarylenesilo~ane~ h.a~ing the follo~i.ng formula
and an average molecular weight of 25,00.Q had a content of the
low molecular weigh.t compounds soluble i.n acet~ne being less
than 7~ and has a softening poi.nt of 180C.
..
-54-
,, .
7~
~ O - S - O ~
The organosilicon high molecular weight compound
was dissolved in benzene and the resulting benzene solution was
; spun in a dry process to obtain fibers having a diameter of
about 10 ~. The spun fibers were subjected to a preliminary
heating by gradually raising the temperature from room tempera-
ture to 800C in 6 hours under vacuum (1 x 10 3 mmH~) and then
baked by raising the temperature up to 1,800C to form silicon
carbide fibers. The tensile strength of the fibers baked at
1,100C was 530 Kg/mm2 and the tensile strength of the fibers
baked at 1,800C was 70 Kg/mm2.
Example 18
A polysilmethylene having the following formula and
an average molecular weight of a~out 27,000 had a content of
: the low molecular weight compounds soluble in acetone being
less than 3% and had a softening point of 210C.
CH3
[ "i - CH2 ]
:~ ~H
The organosilicon high molecular welght compound
was dissolved in benzene and the resulting solution was spun
in a dry process into fibers having a diameter of about 10 ~.
The spun fibers were su~jected to a preliminary heating by
gradually raising the temperature from room temperature to
8Q0C in 6 hours under ~acuum C1 x lQ 3 m~H~ Then the fibers
-55-
~, . .
1J!7~
were baked by heating up to 1,800C under vacuum. The tensile
strength of the fibers baked at 1,300C was 680 Kg/mm2 and the
tensile strength of the fibers baked at 1,800C was 70 Kg/mm2.
Example 19
Polysiltrimethylene having the following formula and
an average molecular weight of about 28,000 had a content of
the low molecular weight compounds soluble in acetone being 4.5
and had a softening point of 230C.
fH3
[ I C 2 C 2 CH 2~
CH3
The organosilicon high molecular weight compound was
dissolved in benzene and the resulting solution was spun in a
dry process into fibers having a diameter of about lO ~. -
The fibers were subjected to a preliminary heating by
raising the temperature from room temperature to 800C in 6
hours under vacuum, and the thus treated fibers were baked by
heating up to 1,800C under argon atmosphere. The tensile
strength of the fibers baked at l~Qoaoc ~as. 580 Kg/mm2, and
the tensile strength of the fi~ers baked at 1,8Q0C ~as
76 Kg/mm2.
Example 20
lO g of cyclic polysilane (Ph2Si)5 ~as ~ed in an
; autoclave and the gas-eous content of the autoclaVe ~as
substituted with argon gas and then said pol~silane ~as reacted
by heating at 420C for 48 hburs. After completion of the
reaction, the reaction produc~ ~-as d~ssolved i~n benzene and
the solution was taken out ~rom the autocla~e and the solu.ion
-56-
's~
was fi~t~red and then berlzene was evaporated under a reduced
pressure to obtain 4.8 ~ of a solid high molecular weight
compound. An average molecular weight of this high molecular
weight compound was 18,000. The organosilicon high molecular
weight compound had a content of the low molecular weight
compound soluble in acetone being 5% and had a softening point
of 130C. The organosilicon high molecular weight compound was
dissolved in xylene, and the solution was heated at 50C to
form a spinning bath, which was spun in a dry process into
fibers having a diameter of about 10 ~. The spun fibers were
subjected to a preliminary heating by raising temperature from
room temperature to 800C in 6 hours under vacuum (1 x 10 3 mmHg)
and baked by heating up to 1,800C to form silicon carbide
fibers. The tensile strength of the fibers baked at 1,100C
was 480 Kg/mm2 and the tensile strength of the fibers baked at
1,800 C was 55 Kg/mm2.
Example 21
An apparatus for producing silicon carbide fibers as
shown in Figure 24 was used and the entire gaseous contents of
the apparatus was substituted ~ith nitrogen gas. A mixed
starting material of about 65% of dimethyldichlorosilane,
about 25% of methyltrichlorosilane, about 5% of trimethylchloro-
silane and about 5~ of the other substances ~ere charged in a
primary reaction column 1 heated at 750C at a rate of 5 l/hr.
The reaction product formed ;n this column was introduced into a
di.stillation column 2 and the: gases consis;ti.ng mainly of propane
and hydrogen were separated from liquid. The liquid ~as
i.ntroduced into a secondary reaction column 3 heated at 850C
.
-57-
~ . .
to e~fect the thermal polycondensation reaction and then the
reaction product was charged into a separating column 4 and
separated into gas, low molecular weight compounds and high
molecular weight compounds. Among them the gas was discharged
from the column through a valve 18, the low molecular weight
compounds were fed into the secondary reaction column 3 through
a valve 19 as a recycling material. The yield of the above
described high molecular welght compound was 19~ and the average
molecular weight was 2,400 and a content of acetone-soluble low
molecular weight compounds was about 25~, so that the high
molecular weight compound was fed into an aging vessel 5 through
a valve 20 and aged at 350C for 4 hours under atmospheric
pressure. Thereafter, the thus aged product was filtered with
a filter 7 and compressed with a pump 8 ana spun through a
spinneret 9 into fibers having a diameter of about 10 ~. The
spinning temperature was about 40C and the spinning rate was
20 m/min. The spun fibers were subjected to the preliminary
heating through a preliminary heating apparatus 10 under vacuum
having a length of 4 m, where the outlet temperature was 800C,
and then baked at 1,800C in a baking oven 11 under argon
atmosphere having a length of 2 m, in which the center was
1,800C, to form silicon carbide fibers, which were wound up on
a take-up device 12. The diameter of the formed silicon carbide
fibers was about 7 ~, and the yield was about 11% based on the
starting material. The tensile strength of the fiber was about
75 Kg/mm2. When the baking was effected at 1,100C, the
tensile strengt~ was 480 Kg~mm2 and Young~s modulu$ was
29 ton/mm2.
-58-
i .
Example 22
Silicon carbide fibers were produced startlng from
dimethyldichlorosilane in the same manner as described in
Example 21.
The dimethyldichlorosilane was charged in the primary
reaction column 1 heated at 780C at a rate of 8 l/hr. The
reaction product was introduced into the distillation column 2,
wherein the gases consisting mainly of propane and hydrogen
were separated from liquid. The liquid was introduced into the
secondary reaction column 3 heated at 880C to effect the thermal
polycondensation reaction. Then, the reaction product was
separated into gas, low molecular weight compounds and high
molecular weight compounds în the separating column 4.
The yield of the above high molecular weight compound
was 27%, and the average molecular weight was 3,200, and the
content of acetone soluble lo~ molecular weight compounds was 27~.
The high molecular weight compound was aged in the
aging vessel 5, at about 380C for about 3 hours, filtered,
pumped and spun through the spinneret 9 into fibers having a
diameter of about 10 ~. The spinning temperature was about
45C and the spinning rate was about 40 m/min. These spun
fibers were subjected to the preliminary heating through the
preliminary heating apparatus 10 having a length of 4 m, an
inlet temperature of room temperature and an outlet temperature
of 800C under vacuum. Then, the thus treated fibers were baked
up to l,8QQC in t~e baking oven 11 under vacuum to form
silicon caxbide fibers ha~ng a diameter of about 7 u, which
were wound up on the take-up device 12. The ~ield was about
~, ,
-59-
7~
17~ based on the startlng material. The tensile strength of
the fiber was 95 ~g/mm2. When the baking was effected at
1,000C, the tensile strength was 540 Kg/mm2 and Young's modulus
was 31 ton/mm2.
Example 23 .
Silicon carbide fibers were produced starting from a
mixture of about 78% of dimethyldichlorosilane, about 8% of
methyltrichlorosilane, about 3% of trimethylchlorosilane, about
2~ of methyldichlorosilane and about 9~ of the other substances
10 in the same manner as described in Example 21.
The mixture was charged in the primary reaction
column 1 heated at 750C at a rate of 6 l/hr. The reaction
product was introduced into the distillation column 2, wherein
the gases containing rich propane and hydrogen were separated
from liquid. The liquid was introduced into the secondary
reaction column 3 heated at 850C to effect the thermal poly-
condensation reaction. Then, the reaction product ~as separated
: into gas, low molecular weight compounds anZ. high molecular
weight compounds in the separating column 4.
The yield of the above high molecular weight compound
: was 21% and the average molecular weight ~as. 2, 6ao and the
content of acetone solu~le low molecular weight compounds was
about 22~.
The high molecular weight compound was aged in the
aging vessel 5 at 42QC for 3 hours, filtered ~ith a ~ilter 7,
compressed wi.th a pump 8 and spun through tne s~pinneret 9 into
fibers having a diameter of a~out 15 ~. These ~pun fibers were
subjected to the prelimi.nar~ h.eati.ng through the preli.minary
_6a-
heating apparatus 10 under vacuum :Erom room temperatures up to
800C in 6 hours and then baked up to 1,800C in carbon monoxide
gas to form silicon carbide fibers. The diameter o~ the formed
silicon carbide fibers was about 11 ~. The yield was 13~ based
on the starting material. The tensile strength of the fiber
was 85 Kg/mm2. When the baking was effected at 1,100C, the
tensile strength was 490 Ky/mm2 and Young's modulus was
26 ton/mm .
Example 24
Silicon carbide fiber~ were produced starting from a
mixture of about 55~ of diphenyldichlorosilane, about 35% of
diphenyltrichlorosilane and about 10% of the other substances
in the same manner as described in Example 21.
The mixture was charged in the primary reaction column
1 heated at about 800C at a rate of 4 l/hr. The reaction
product was introduced into the distillation column 2, wherein
the gases consisting mainly of chlorine were separated from
liquid. Next, the liquid was introduced i.nto the secondary
reaction column 3 heated at about 900C to ef~ect the thermal
polycondensation reaction. Then, the reaction product was
separated into gas, low molecular wei.ght compounds and high
molecular weigh.t compounds. in the separating column 4.
The yield of the above high molecular weLgh.t compound
was 24% and the average molecular weight was ab.out 5,0Q0 and
the content of acetone soluble lo~ molecular ~eight compounds
was about 5%.
The high molecular weight compound was directly
$iltered with the filter 7 without feeding into the agi.ng
-61-
~ ~t~7~
vessel 5 and ~le~ spun through the spinneret 9 into fibers having
a diameter oE about 10 1l . The spun fibers were subjected to
the preliminary heating through the preliminary heating
apparatus 10 having a length of 4 m, an inlet room temperature
and an outlet temperature of 800C under vacuum and then baked
up to l,800C under argon to form silicon carbide (SiC) fibers
having a diameter of about 7 ~. The yield was 18% based on the
starting material. The tensile strength of the fiber was
85 Kg/mm2. When the baking was effected at 1,100C, the tensile
strength was about 430 Kg/mm2 and Young's modulus was 26 ton/mm2.
Example 25
Silicon car~ide fibers were produced startlng from
tetramethylsilane in the same manner as described in
Example 21.
The tetramethylsilane was charged in the primary
reaction column 1 heated at 780C at a rate of 9 l/hr. The
reaction product was introduced into the distlllation cc,lumn 2,
wherein the gases consisting mainly of propane and hydrogen
were separated from liquid. Next, the liquid was introduced
into the secondary reaction column 3 heated at 880C to effect
the thermal polycondensation reaction. Then, the reaction
product was separated into gas, low molecular weight compoun~s
and high molecular weight polym~rs in the separating column 4.
The yield of the above high molecular weight compound
was 16~ and the average molecular weight was 2,800 and the
content of acetone soluble low molecular weight compounds was 20%.
Then, the high molecular weight compound ~as aged
in the aging vess.el 5 at about 360C for a~out 3 hours, filtered
. -, . ..
-62-
with the filter 7, compressed with the pump 8 and spun through
the spinneret 9 into fibers having a diameter of about 10 ~.
The spinning temperature was about 47C and the spinning rate
was about 50 m/~in. These spun fibers were subjected to the
preliminary heating through the preliminary heating apparatus
10 having a length of 4 m, an inlet room temperature and an
outlet temperature of 800C under vacuum. Then, the fibers
were baked up to 1,800C in the baking oven 11 under vacuum to
form silicon carbide fibers having a diameter of about 7 ~,
which were wound up on the take-up device 12. The yield was
about 14% based on the starting material. The tensile strength
of the fiber was 68 Kg/mm2. When the baking was effecled at
1,000C, the tensile strength was 420 Kg/mm2 and Young's
modulus was 35 ton/mm2.
Example 26
Fifty grams of 1,3-disilacyclob.utane was placed ir~
an autoclave and, after air in the autoclave ~as purged with
argon gas, polycondensation was effected at 410C for 48 hours.
After the complet;on of the reaction, the polycondensation
product was taken up in benzene and then benzene was evaporated
to obtain 41 g of solid high molecular weight compound. Since
this compound contained 15% of acetone-soluble lo~ molecular
weight compound, it was dissolved in 2Q0 cc of hexane and then
added with 400 cc of acetone to o~tain 33 g of acetone-insoluble
prec~pitate. Th.e precipitate was di.ssolved i.n benzene and
spun into fi~ers having a d;ameter of about lQ ~ by a dry
process. Th.e spun fi~e.rs were thoroughly dri.ed and th.en
subjected to a prell~minary heating from room temperature to
-63-
'' :. .
,
l~p ;J~
800C under vacuum (1 x 10 3 mm~g) in 6 hours. Then, the thus
treated fibers were baked up to 2,000C under argon atmosphere
to form silicon carbide fibers. The tensile strength of the
fiber was 48 Kg/mm2. When the baking was effected at 1,000C,
the tensile strength was 430 Kg/mm2 and Young's modulus was
39 ton/mm .
Example 27
An organosilane high molecular weight compound was
produced from tetramethyldisilphenylene
[H~CH3)2Si-c6~4-si(cH3)2 ]
and acetylene with a catalyst of H2PtC16. This compound had an
average m~lecular weight of about 6,uOO and a content of
acetone-soluble low molecular weight compound of 15%. Then,
30 g of the organosilane high molecular weight compound was
dissolved in 200 cc of benzene and the solution was then admixed
with 400 cc of acetone to obtain 26 g of precipitate. The
precipitate was heated to 150C and spun into fibers having a
diameter of about 10 ~. These spun fibers were subjected to a
preliminary heating from room temperature to 800C under vacuum
in 4 hours and then baked from 8Q0C up to 2,000C under argon
atmosphere to form silicon carbide fibers. The tensile strength
of the fiber baked at 1,200C ~as 3~a Kg/mm2 and the tensile
strength of the fiber baked at 2,OQ0C ~a5 63 Kg/mm2.
Example 28
Polycondensation ~,as effected ~ith N,N'-diphenyl-
~CH-3 CbH5~
diaminodimethylsilane ~ Si < ~ and p-dihydroxybenzene
~CH3 NHC~H`5J
-
-64-
to produce an organosilane high molecular weight compound. This
compound had an average molecular weight of about 7,000 and a
content of acetone-soluble low molecular weight compound of 12%.
After the low molecular weight compound was removed with ethyl
alcohol in a Soxhlet's extractor, the residue was dissolved in
benzene and spun into fibers having a diameter of about 10 ~ by
a dry process. These spun fibers were thoroughly dried and
subjected to a preliminary heating from room temperature up to
800C in 1 hour and then baked up to 1,800C under vacuum to
form silicon carbide fibers. The tensile strength of the fiber
baked at l,000C was 410 Kg/mm2 and the tensile strength of
the fiber baked at 1,800C was 43 Kg/mm2.
Example 29
Silicon car~ide fibers were produced startlng from
tetramethyldichlorodisilane in the same manner as described in
Example 21.
The tetramethyldichIorodisilane was charged in the
primary reaction column 1 heated at 750C at a rate of 11 l/hr.
The reaction product was introduced into the distillation column
~ 20 2, wherein the gases consisting mainly of propane and hydrogen
; were separated from liquid. Then, the liquid was introduced
into the secondary reaction column 3 heated at 850C to ef~ect
the thermal polycondensation reaction. Next, the reaction
product was separated into gas, low molecular weight compounds
and high molecular weight compounds in the s-eparating column 4.
The yieId of the above high molecular weight compound
~as 14% and the average molecular weight ~as 2,1aQ and the
content of acetone soluble low molecular weight compoun~s ~as
-65-
~ 76~
about 28~.
The high molecular weight compound was aged in the
aging vessel 5 at 350C under argon atmosphere for 6 hours,
filtered with the filter 7, compressed with the pump 8 and then
spun through the spinneret 9 into fibers having a diameter of
about 10 ~. These spun fibers were subjected to the preliminary
heating through the preliminary heating apparatus 10 with a
length of 4 m and an outlet temperature of 800C under vacuum
and baked at 1,800C in the baking oven 11 with a length of 2 m
under argon atmosphere to form silicon carbide fibers, which
were wound up on the take-up device 12. The silicon carbide
fiber had a diameter of about 8 ~ and a yield of about 10% based
on the starting material. The tensile strength of the fiber
was about 45 Kg/mm2. When the baking was effected at 1,100C,
the tensile strength was about: 430 Kg/mm2 and Youn~'s modulus
was 33 ton/mm2.
Example 30
An organosilicon high molecular weight compound was
produced by polycondensing p-bis~.oxydîmethylsilyl)benzene
[HO(CH3)2SiC6H4Si(CH3~2OH] with pot.as:sium hydroxide catalyst.
This compound had an a~erage moiecular ~eight of 3,500 and a
content of acetone-soluble low molecular ~.eight compound of
about 21%. Then, 30 g of the hi.gh molecular ~eight compound
was dissolved in 10.0 cc of benzene and the solution then was
admixed with 300 cc of acetone to obtain 21 g of precipitate.
The precipitate ~as heated and spun i.nto f.ibers having a
diameter of about 10 ~ by a dry process. The.se spun fi.bers
~ere subjected to a prelimi`nary heating from room temperature
-66-
~'iP'7~
up to 800C under vacuum in 4 hours and then baked up to 1,800C
under carbon monoxide atmosphere ko form silicon carbide fibers.
The tensile stren~th of the fiber baked at 1,000C was
420 Kg/mm2 and the tensile strength of the fiber baked at 1,800C
was 53 Kg/mm .
Example 31
Silicon carbide fibers were produced starting from
diacetoxydimethylsilane [(CH3)2Si(OCOCH3)2] in the same manner
as described in Example 21.
The diacetoxydimethylsilane was charged in the primary
reaction column 1 heated at about 750C at a rate of 9 l/hr.
The reaction product was introduced into the distillation
column 2, wherein the gases were separated from liquid. Then,
the liquid was introduced into the secondary reaction column 3
heated at about 850C to effect the thermal polycondensation
reaction. Next, the reaction product was. separated into gas,
low molecular weight compounds and high molecular weight
compounds in the separating column 4.
The yield of the above high. molecular wei.ght compound
was 13% and the average molecular weight was ahout 1,8Q0 and
the content of acetone soluble low molecular wei.gh.t substance
: was about 35%.
The hi.gh molecular weight compound ~as. aged in the
aging vessel 5 at 390C i.n air for 4 hours, fi.ltered with the
filter 7 and then spun through th.e spinneret 9 into fibers
having a diameter of about 10 ~. These spun fibers were
s.ubjected to th.e ~rel:iminary heati.ng th~ough th.e prelimi.nary
heati.ng apparatus lQ having a length. of 4 mm, an inle.t temperatu~e
7~
of room temperature and ~n out:let temperature of 800C under
vacuum and then baked at 1,800C in -the baking oven ll under
argon atmosphere to form silicon carbide fibers having a
diameter of about 8 ~. The yield was about 9% based on the
starting material and the tensile strength of the fiber was
48 Kg/mm2. When the baking was effected at l,lQ0C, the tensile
strength was about 410 Kg/mm2 and Young's modulus was 37 ton/mm .
Example 32
Dodecamethylcyclohexasilane was heat treated in an
autoclave at 400C for 48 hours to obtain organosilicon high
molecular weight compounds. lO g of the organosilicon high
molecular weight compounds was dissolved in 100 cc of n-hexane
and to the solution was added 300 ~c of acetone and the insoluble
portion was about 60%. This insoluble portion was dissolved in
benzene and the resulting solution was spun in a dry process at
a spinning temperature of 25C at a spinning rate of 100 m/min.
to obtain fibers having a diameter of 10 ~. The fibers were
fully dried and then subjected to a preliminary heating by
raising the temperature to 800C in about 6 hours. under vacuum
(1 x 10 mmHg~.
- The thus treated fibers were baked by heating to
1,800C under argon atmosphere, while applying a tension of
5 Kg/mm2 to obtain silicon carbide fibers. The tensile
strength of the silicon carbide fibers baked at l,8aOC was
28~ Kg/mm . The tensile strength of the silicon carbide fibers
baked in the same manner as descri~ed above without applying the
tension was 68 Kg/mm2. This shows th.at the baking at a high
temperature under a tension notice.ably~increases the tensile
-68-
7~2~
strength .
Example 33
10 g of linear polydimethylsilane produced from
dimethyldichlorosilane was fed into an autoclave and heated at
400C under a pressure of 50 atmospheres for 48 hours under argon
atmosphere. The reaction product was dissolved in ether and
an insoluble portion was removed and the resulting solution was
evaporated to obtain 4.3 g of a solid product. This solid
product had an average molecular weight of 5Q0-15,000 and was
dissolved in 50 cc of hexane and to the resulting solution was
added 200 cc of acetone to form precipitate. The precipitate
was dissolved in benzene and the benzene solution was spun at
25C in a dry process into fibers having a diameter of about 10 ~.
The spun fibers were subjected to a preliminary heating
by gradually heating up to 7Q0C in 6 hours under vacuum.
The thus treated fibers ~ere baked by raising the
temperature from 700C to 2,000C while applying ultrasonic wave
having a frequency of 2G0 KHz generated from a ultrasonic wave
generator of an output of 100 W, to form silicon carbide fibers.
The tensile strength of the silicon carbide fiberq baked at
lr700C was 293 Kg/mm2. The tensile strength of the silicon
carbide fibers baked in the same manner as described above
without applying the ultrasonic wave was 55 Kg/mm2.
Example 34
PolyCsilmethylenesiloxane~ having the follo~ing
formula and an average molecular weIght of about 24,0Q0 ~as
used as a starting material.
-69-
~iLi'7~PZ~;
1 3 1 3
tfi - CH2 - Si - 0
CH3 CH3
The organosilicon high molecular weight compound contained less
than 5~ of the low molecular weight compound soluble in acetone
and this compound was dissolved in benzene to form a spinning
solution, which was spun into fibers having a diameter of about
10 ~. The spun fibers were subjected to a preliminary heating
by raising the temperature from room temperature to 800C in
4 hours under vacuum.
The thus treated fibers were baked by heating from
800C to 2,Q00C, while applying ultrasonic wave having 300 KHz ,-
by means of an ultrasonic wave generator of an output of 100 W
to obtain silicon carbide fibers. The formed silicon carbide
fibers had a tensile strenyth of 275 Kg/mm2. The tensile
strength of the silicon carbide fibers baked in the same manner
without applying the ultrasonic wave was 64 Xg~mm2.
Example 35
Dodecamethylcyclohexasilane ~as heat treated in an
autoclave at 400C for 48 hours to o~tain organosilicon polymers.
10 g of the silicon poly~ers was- dissolved in lQQ cc of n-hexane
and to the solution was added 3Q0 cc of acetone and the
; insoluble portion was about 60%. This insoluble porti.on was
- dissolved in benzene and the resulti,n~ solution was spun in a
dry process at a spinning temperature of 25C at a spi.nning rate
of 100 m/min. through.a spinnlng tube, to ~hi.ch a mixed gas
of benzene, acetone and argon, the paxtial pres5uxes of benzene,
-70-
acetone and argon beinq 0.5, 0.3 and 0.2 atmospheric pressures
respectively, was introduced, to obtain fibers having a diameter
of 10 Il. The fibers were heated in air at 150C for 30 minutes
and then subjected to a preliminary heating by raising the
temperature to 800C in about 6 hours under vacuum (1 x 10 3 mmHg).
The thus treated fibers were baked by heating to
1,800C under argon atmosphere to obtain silicon carbide fibers.
The tensile strength of the silicon carbide fibers baked at
1,800C was 68 Kg/mm2, and that of the silicon carbide fibers
baked at 1,300C was 410 Kg/mm2 and Young's modulus was
28 ton/mm2.
Example 36
10 g of linear polydimethylsilane
Me Me
[ I i - Si~
Me Me
produced from dimethyldichlorosilane was fed in an autoclave
and heated at 400C under a pressure of 50 atmospheres for
48 hours under argon atmosphere. The reaction product was
dissolved in ether and an insoluble portion was removed and
the resulting solution was evaporated to obtain 4.3 g of a
solid product. This solid product had an average molecular
weight of 1,800 and was dissolved in 50 cc of hexane and to
- the resulting solution was added 200 cc of acetone to form
precipitate. The precipitate was dissolved in benzene and the
benzene solution was spun at 25C in a dry process through a
spinning tube, to which a gaseous mixture of benzene and air
having a benzene partial pressure of 0.3 atmospheric pressure,
-
.
`7~Z~
was introduced, into fibers having a diameter of about 10 ~.
The spun fibers were heated at 200C for 15 minutes
in air containing ozone and sub~ec-ted to a preliminary heating
by gradually heating up to 700C in 4 hours under vacuum.
The thus treated fibers were baked by raising the
temperature to l,800C under vacuum to form silicon carbide
fibers. The tensile strength of the silicon carbide fibers
baked at l,800C was 65 Kg/mm2.
Example 37
10 g of dodecamethylcyclohexasilane was fed in an
autoclave and air in the autoclave was purged with argon gas
and the polycondensation reaction was effected at 400C for
48 hours under a pressure of 40 atmospheres. After completion
of the reaction, the polycondensation product was permitted to
cool at room temperature, and then added with ether to form
ether solution. The ether solution was taken out from the
autoclave and ether was evaporated to obtain 6.6 g of a solid
high molecular weight compound containing 40% of acetone-soluble
low molecular weight compounds. The solid high molecular weight
compound was heated and aged at 300C for 8 hours while slowly
stirring under atmospheric pressure in argon atmosphere to
obtain an organosilicon high molecular weight compound
containing 5% of acetone-soluble low molecular weight compounds.
The resulting organosilicon high molecular weight
compound was dissolved in benzene, and the benzene solution was
spun in a dry process to obtain fibers having a diameter of
about 10 ~. The fibers were heated at 200C for 30 minutes
in air and then gradually heated up to 800C in 6 hours under
-72-
~7~2~
vacuum (l ~ 10 3 mm~g) to e~fect the preliminary heating of
the fibers, and then baked up to 1,800C to obtain silicon
carbide fibers.
The tensile strength of the fibers heated to 1,200C was
650 Kg/mm and that of the fibers heated to 1,800C was
85 Kg/mm .
Example 38
10 g of octaphenylcyclotetrasilane was fed in an
autoclave together with 0.1 g of benzoyl peroxide, and air
in the autoclave was purged with argon, and the polycondensation
was effected at 320C for 24 hours under about 35 atmospheric
pressure. After completion of the reaction, hexane was added
to the autoclave, and the polycondensation product was taken
out from the autoclave in the form of hexane solution.
Insoluble portion in hexane was filtered off, and hexane was
- evaporated to obtain 7.1 g of solid high molecular weight
;~ compounds having an average molecular weight of about 4,000.
The high molecular weight compounds were dissolved in 100 cc
of hexane, and the hexane solution was then admixed with 400 cc
of acetone to obtain 6.3 g of acetone-insoluble precipitate.
The precipitate was dissolved in benzene, and the benzene
solution was spun in a dry process through a spinning tube, to
which a gaseous mixture of benzene and air having a benzene
partial pressure of 0.3 atmospheric pressure, was introduced,
into fibers having a diameter of about lO ~. The fibers were
heated at 180C for 18 minutes in air and further heated up to
800C in 6 hours under vacuum (l x lO 3 mmHg) to effect the
preliminary heating of the fibers. The preliminarily heated
-73-
, . . . .
: : ..'
.
'.'D7~'1'2S
fibers were ~urther baked up to 1,800C in a graphite crucible
to obtain silicon carbide fibers. The fibers baked at 1,000C
had a tensile strength of 510 Kg/mm , and fibers baked at
1,800C had a tensile strength of 78 Kg/mm .
Example 39
lO g of a mixture of cyclic dimethylpolysilanes having
formulae of (Me2Si)5 and (~e2Si)6 was fed in an autoclave
together with 0.5 g of azoisobutyronitrile, and air in the
autoclave was purged with argon, and the polycondensation was
effected at 400C for 12 hours under a pressure of about 80
atmospheres. After completion of the reaction, benzene was
added to the autoclave, and the polycondensation product was
taken out from the autoclave in the form of benzene solution.
Insoluble portion in benzene was filtered off and benzene was
evaporated under a reduced pressure to obtain 4.8 g of solid
high molecular weight compounds having an average molecular
weight of about 3,800. The high molecular weight compounds were
dissolved in 50 cc of hexane, and the hexane solution was then
admixed with 200 cc of acetone to obtain 3.9 g of acetone-
insoluble precipitate. The precipitate was dissolved in benzene,
and the benzene solution was spun in a dry process through a
spinning tube, to which a gaseous mixture of benzene and air
having a benzene partial pressure of 0.4 atmospheric pressure was
introduced, into fibers having a diameter of about lO ~. The
fibers were heated at 150C for 30 minutes in air and then
gradually heated up to 800C in 4 hours under vacuum
(l x 10 mmHg) to effect the preliminary heating of the fibers.
The preliminarily heated fibers were further baked up to
1,800C under vacuum. The tensile strength of the fibers baked
-74-
7~.'J '~
at l,300C was 390 Kg/mm2, and tha-t of the fibers baked at
1,800C was 95 Kg/mm .
Example 40
10 g of a mixture of cyclic diphenylsilane of the
formula (Ph2Si)4, that of the formula (Ph2Si)5 and linear
polydiphenylsilane was fed in an autoclave and air in the
autoclave was purged with gaseous nitrogen, and the polycondensa-
tion was effected at 380C for 50 hours under a pressure of
about 60 atmospheres. After completion of the reaction, benzene
was added to the autoclave, and the pol~condensation product was
taken out from the autoclave in the form of benzene solution,
and the benzene solution was concentrated under a reduced
pressure to obtain 6.9 g of solid high molecular weight
compounds. The resulting high molecular weight compounds were
dissolved in 50 cc of benzene, and the benzene solution was
added with 200 cc of acetone to obtain 4 8 g of acetone-insoluble
precipitate. The precipitate was dissolved in benzene, and
the benzene solution was spun in a dry process through a spinning
tube, to which a gaseous mixture of benzene and argon having a
benzene partial pressure of 0.25 atmospheric pressure was
introduced, into fibers having a diameter of about 10 ~. The
fibers were heated at 200C for 15 minutes in air containing
ozone and then gradually heated up to 800C in 4 hours under
argon atmosphere to obtain black fibers having metallic luster.
The fibers had a tensile strength of 420 Xg/mm2. The fibers
were baked up to 1,300C under helium vacuum to obtain silicon
carbide fibers. Then said fibers were heated at 800C for
2 hours in air. The tensile strength of the fibers baked at
-75-
.
~';i7~
1,300C was 410 Kg/mm2, and that o~ the fibers baked at 1,800C
was 73 Kg~mm .
Example 41
Fluidized hexamethyldisilane was fed into a reaction
column as shown in Figure 1 heated to 850C at a feeding rate
of l l/hr. together with argon gas. The starting hexamethyldi-
silane was subjected to a decomposition reaction and a poly-
condensation reaction in the heated reaction column and formed
into high molecular weight compounds, and at the same time
low molecular weight compounds were formed. A part of the
resulting high molecular weight compounds was able to be taken
out from the heated reaction column. Major part of the high
molecular weight compounds was fed into a separating column
together with the low molecular weight compounds, and gases and
the low molecular weight compounds were separated from the high
molecular weight compounds in the column. The low molecular
weight compounds were again fed into the heated reaction
column and recycled. The operation was continued for lO hours
and 5.4 Kg of high molecular weight compounds having an
average molecular weight of about 3,500 was obtained.
From lO g of the resulting high molecular weight
compounds, ethyl alcohol-soluble portion was removed by means
of a Soxhlet's extractor to obtain 7.8 g of ethyl alcohol-
insoluble portion, which was used as a spinning material. The
ethyl alcohol-insoluble portion was heated to 145C and spun
into fibers having a diameter of about lO ~. The spun fibers
were heated from room temperature to 200C in 30 minutes in air
and further heated up to 800C in 6 hours under vacuum to effect
-76-
,
7 ~
the preliminary heatinq of the ~ibers. The preliminarily
heated fibers had a tensile strength of 430 Kg/mm2. The thus
treated fibers were further baked by heating up to 1,800C under
argon atmosphere. The tensile strength of the baked fibers
was 105 K~/mm .
Example 42
An apparatus for producing silicon carbide fibers as
shown in Figure 24, was used and the entire gaseous contents
of the apparatus was substituted with nitrogen. A mixed
starting material of about 65~ of dimethyldichlorosilane, about
25% of methyltrichlorosilane, about 5% of trimethylchlorosilane,
and about 5% of the other substances was charged in a primary
reaction column 1 heated at 750C at a rate of 5 l/hr. The
reaction product formed in this column was introduced into the
distillation column 2, wherein the gases consisting mainly of
propane and hydrogen were separated from liquid. The liquid
was introduced into a secondary reaction column 3 heated at
850C to effect the thermal polycondensation reaction and then
the reaction product was charged into a separating column 4
and separated into gas, low molecular weight compounds and high
molecular weight compounds. The separated gas was discharged
from the column through a valve 18, and the low molecular weight
compounds were fed into the secondary reaction column 3 through
a valve 19 as a recycling material.
The yield of the above high molecular weight polymer
was 19% and the average molecular weight was 2,400 and the
content of acetone soluble low molecular weight compounds was
about 25%.
.
- ~ . .
- ':' ~ ''
7~
The hi~h molecular wci~ht compounds were fed into an
aging vessel 5 through a valve 20 and aged at 340C for 4 hours
under atmospheric pressure. Thereafter, the thus aged product
was filtered with a filter 7, compressed with a pump 8 and then
spun through a spinneret 9 into fibers having a diameter of
about 10 ~. The spinning temperature was 100C and a mixture
of benzene and air having a benzene partial pressure of 0.25
atmospheric pressure was supplied into the spinning tube and
the spinning rate was 20 m/hr. These spun fibers were treated
from room temperature up to 200C in air for 30 minutes,
subjected to a preliminary heating through a preliminary heating
apparatus 10 with a length of 4 m and an outlet temperature of
800C under vacuum and then baked to 1,800C in a baking oven 11
with a length of 2 m under argon atmosphere to form silicon
carbide fibers, which were wound up on a take-up device 12. The
diameter of the formed silicon carbide fibers was about 7 ~, the
yield was about 11% based on the starting material and the tensile
strength was about 75 Kg/mm . When the baking was effected at
1,100C, the tensile strength was 480 Kg/mm and Young's
modulus was 41 ton/mm .
Example 43
Silicon carbide fibers were produced starting from
dimethyldichlorosilane in the same manner as described in
Example 42.
The dimethyldichlorosilane was charged in the primary
reaction column 1 heated at 780C at a rate of 8 l/hr. The
reaction product was introduced into the distillation column 2,
wherein the gases consisting mainly of propane and hydrogen
-
-78-
1~7~3.Z~
were separated from ll~uid. Next, the ].iquid was introduced
into the secondary reaction column 3 heated at 880C to effect
the thermal polycondensation reacti.on and then the reaction
product was separated into gas, low molecular weight compounds
and high molecular weight compounds in the separating column 4.
The yield of the above high molecular weight
compounds was 27~ and the average molecular weight was 3,200
and the content of acetone soluble low molecular weight
compounds was 20%.
The high molecular weight compoundswere aged in the
aging vessel 5 at about 350C for about 3 hours, filtered with
the filter 7, compressed with the pump 8 and then spun through
the spinneret 9 into fibers having a diameter of about 10 ~.
The spinning temperature was about 45C and the spinning rate
was about 40 m/hr. These spun fibers were heated from room
temperature up to 200C in air containing ozone for 15 minutes,
subjected to the preliminary heating through the preliminary
heating apparatus 10 having a length of 4 m, an inlet room
temperature and an outlet temperature of 800C under vacuum,
and then baked at 1,800C in the baking oven 11 under vacuum
to form silicon carbide fibers having a diameter of about 7 ~,
which were wound up on the take-up device 12. The yield was
about 17% based on the starting material and the tensile
strength of the fibersbaked at l,800C was 95 Kg/mm2. When the
baking was effected at 1,000C, the tensile strength was
430 Kg/mm2 and Young's modulus was 37 ton/mm .
Example 44
Silicon carbide fibers were produced starting from .
-79~
'
. . '
11~7~
a mixture o~ about 78~ of climethyldichlorosilane, about 8~ of
methyltrichlorosilane, about 3~ of trirnethylchlorosilane, about
2~ of methyldichlorosilane and about 9% of the other substances
in the same manner as described in Example 42.
The mixture was charged in the primary reaction
column 1 heated at 750C at a rate of 6 l/hr. The reaction
product was introduced into the distillation column 2, wherein
gases were separated from liquid. Next, the liquid was
introduced into the secondary reaction column 3 heated at
850C to effect the thermal polycondensation reaction and then
the reaction product was separated into gas, low molecular weight
compounds and high molecular weight compounds in the separating
column 4.
The yield of the above high molecular weight compounds
was 21% and the average molecular weight was 2,600 and the
content of acetone soluble low molecular weight compounds was
about 22%.
The high molecular weight compounds were aged in the
aging vessel 5 at 340C for 3 hours, filtered with the
filter 7, compressed with the pump 8 and then spun through the
spinneret 9 into fibers having a diameter of about 15 ~. The
spinning temperature was 75C. These spun fibers were cut into
a length of about 30 cm, heated from room temperature up to
150C in air for 30 minutes, subjected to the preliminary
heating from room temperature to 800C under vacuum in 6 hours
and then baked at 1,800C under carbon monoxide atmosphere to
form silicon carbide fibers. The diameter of the formed silicon
carbide fibers was about 11 ~ and the yield was 13% based on
1~)7~
the starting material. The tens.ile strength of the fiber was
85 Kg/mm2. When the baking was effected at l,100C, the
tensile strength was 490 Kg/mm .
Example 45
Silicon carbide fibers were produced starting from a
mixture of about 55% of diphenyldichlorosilane, about 35% of
diphenyltrichlorosilane and about 10% of the other substances in
the same manner as described in Example 42.
The mixture was charged in the primary reaction
column l heated at about 800C at a rate of 4 l/hr. The
reaction product was introduced into the distillation column 2,
wherein the gases consisting mainly of hydrogen and hydrocarbon
were separated from liquid. Next, the liquid was introduced
into the secondary reaction column 3 heated at about 900C to
effect the thermal polycondensation reaction and then the
reaction product was separated into gas, low molecular weight
compounds and high molecular weight compounds in the separating
column 4.
The yield of the above hish molecular weight
polymers was 24% and the average molecular weight was about
5,000 and the content of acetone soluble low molecular weight
substances was about 5%.
The high molecular weight compounds were filtered with
the filter 7 without aging and then spun through the spinneret
9 into fibers having a diameter of about lO ~. These spun
fibers were heated from room temperature up to 180C in air
for 30 minutes, subjected to the pre~iminary heating through
the preliminary heating apparatus lO having a length of 4 m,
-81-
.
1~7~
an lnlet room temperaturc and an outlet temperature of 800C under
vacuum and then baked at 1,800C in the baking oven 11 under
a~gon atmosphere to form silicon carbide fibers having a
diameter of about 7 ~. The yield of the fiber was 18% based on
the starting material. The tensile strength of the fiber was
85 Kg/mm2. When the baking was effected at 1,100C, the
tensile strength was 430 Kg/mm .
Example 46
Poly(silmethylenesiloxane) having the following
formula and an average molecular weight of about 18,000 was
used as a starting material.
IH3 CIH3
-~ Si - CH - Si - O-~
1 2 I n
CH3 CH3
A content of acetone soluble low molecular weight
substance contained in this high molecular weight compound was
less than 10% and said organosilicon high molecular weight
compound was dissolved in benzene to form a spinning solution,
which was spun into fibers having a diameter of about 10 ~
through a spinning tube using a mixed atmosphere of benzene
and air and having a benzene partial pressure of 0.3
atmospheric pressure. These spun fibers were heated from room
temperature up to 200C in air for 10 minutes, subjected to a
preliminary heating from room temperature up to 800C under
vacuum (1 x 10 3 mmHg) for 4 hours and then baked up to
1,800C under vacuum to form silicon carbide fibers having a
diameter of about 8 ~. The tensile strength of the fiber baked
at 1,000C was about 390 Kg/mm and the tensile strength of the
-82-
7~32S
fiber baked at 1,800C was about 65 Kg/mm2.
Example 47
Pol~(silarylenesiloxane) having the following formula
and an average molecular weight of about 16,000 and a content
of acetone soluble low molecular weight substance of less than 10%.
~ - I ~ ~
The organosilicon high molecular weight compound was
dissolved in benzene to form a spinning solution. This spinning
solution was spun into fibers having a diameter of about 10 ~
through a spinning tube using a mixed atmosphere of benzene and
air having a benzene partial pressure of 0.3 atmospheric pressure
by a dry process. These spun fibers were heated from room
temperature up to 2Q0C in ozone for 10 minutes, subjected to a
preliminary heating from room temperature up to 800C under vacuum
~1 x 10 3 mmHg) in 6 hours, and then baked up t~ 2,000C under
argon atmosphere. Then the fibers were heated at 1,000C in
air for 1 hour to remove free carbon. The tensile strength of
the fiber baked at 1,300C ~as 390 Kg/mm2 and the tensile strength
of the fiber baked at 2,OQ0C was 65 Kg/mm2.
Example 48
Polysilmethylene having the following formula and an
average molecular weight of about 20,000 had a content of
acetone soluble low molecular weight compounds of less than 6%.
CH3
~Si - CH
CH3
.. ~
-~3-
9~
The organosilicon high molecular weight compound was
dissolved in benzene to form a spinning solution. This spinning
solution was spun into fibers having a diameter of about 10 ~
through a spinning tube using a mixed atmosphere of benzene and
air having a benzene partial pressure of 0.15 atmospheric
pressure in a dry process. These spun fibers were heated from
room temperature up to 200C in air for 30 minutes, subjected
to a preliminary heating from room temperature up to 800C
under vacuum (1 x 10 3 mmHg) in 12 hours, and then baked up
to 1,800C under vacuum. The tensile strength of the fiber
baked at 1,300C was 415 Kg/mm2 and the tensile strength of the
fiber baked at 1,800C was 70 Kg/mm2.
Example 49
Poly(dimethylsiltrimethylene) having the following
formula and an average molecular weight of about 21,000 had a
content of acetone soluble low molecular weight compound of
less than 5%.
¦ 3
--~--Si- CH - CH2 - CH2 3
CH3
The organosilicon high molecular weight compound was
dissolved in benzene to form a spinning solution. This spinning
solution was spun into fibers having a diameter of about 10
through a spinning tube using a mixed atmosphere of benzene and
air having a benzene partial pressure of 0.3 atmospheric
pressure in a dry process.
These spun fibers were heated from room temperature up
to 200C in air containing ozone for 15 minutes and subjected to
.~ ~
-84-
7'1
1~g37~
a preliminary heating from room temperature up to 800C
under vacuum for 6 hours. The tensile strength of the fibers
baked at l,000C was 390 Kg/mm2 arld the tensile strength of the
fiber baked at 1,800C under argon atmosphere was 95 Kg/mm2.
Example 50
Silicon carbide fibers were produced starting from
tetramethylsilane in the same manner as described in Example 42.
The tetramethylsilane was charged in the primary
reaction column 1 heated at 780C at a rate of 9 l/hr. The
reaction product was introduced into the distillation column 2,
wherein gases consisting mainly of propane and hydrogen were
separated from liquid. Next, the liquid was introduced into the
secondary reaction column 3 heated at 880C to effect the
thermal polycondensation reaction and then the reaction product
was separated into gas, low molecular weight compounds and high
molecular weight compounds in the separating column 4.
The yield of the above high molecular weight compounds
was 16% and the average molecular weight was 2,800 and the
content of acetone soluble low molecular weight compounds was 20%.
The high molecular weight compound was aged in the
aging vessel 5 at about 360C for about 3 hours, filtered with
: the filter 7, compressed with the pump 8 and then spun through
the spinneret 9 into fibers having a diameter of about 10 ~.
The spinning temperature was about 147C and the spinning rate
was about 50 m/min. These spun fibers were heated from room
temperature up to 200C in air containing ozone for 15 minutes,
subjected to a preliminary heating through the preliminary
heating apparatus 10 having a length of 4 m, wherein an inlet
-85-
1~7~2~;
temperature was room temperature and an outlet temperature was
800C, under vacuum and then baked up to 1,800C in the baking
oven 11 under vacuum to form silicon carbide fibers having a
diameter of about 7 ~I~ which were wound up on the take-up
device 12. The yield was about 14~ based on the starting
material and the tensile strength of the fiber was 68 Kg/mm2.
When the baking was effected at 1,000C, the tensile strength
was 420 Kg/mm2 and Young's modulus was 36 ton/mm2.
Example 51
Fifty grams of 1,1,3,3,-tetramethyl-1,3-disilacyclo-
butane was charged into an autoclave and, after air inside the
autoclave was purged with argon, polycondensation was effected
at 410C for 48 hours. After the completion of reaction, the
polycondensation product was taken up in benzene and then
benzene was evaporated to obtain 41 g of a solid high molecular
`~ weight compound. This high molecular weight compound contained
15% of acetone soluble low molecular weight compounds, so that
it was dissolved in 200 cc of hexane and then was admixed with
400 cc of acetone to obtain 33 g of acetone insoluble precipitate.
~ 20 The precipitate was dissolved in benzene and then spun into
fibers having a diameter of about 10 ~ through a spinning tube
using a mixed atmosphere of benzene and air having a benzene
partial pressure of 0.28 atmospheric pressure in a dry process.
These spun fibers were heated from room temperature up to 200C
in air for 30 minutes, subjected to a preliminary heating from
room temperature up to 800C under vacuum (1 x 10 3 mmHg)
in 6 hours and then baked up to 2,000C under argon atmosphere
to form silicon carbide fibers. The tensile strength of the
-86-
:
,.
~Y ~7~2~;
fiber baked at l,000C was 430 Ky/mm2 and the tensile strength
of the fiber bake~ at 2, nooc was 48 Kg/mm~.
Example 52
Dodecamethylcyclohexasilane was heat treated in an
autoclave at 400C for 48 hours to obtain organosilicon polymers.
100 g of the organosilicon polymers was dissolved in 100 cc of
n-hexane and to the solution was added 700 cc of acetone to
obtain about 60% of acetone insoluble portion. This insoluble
portion was dissolved in xylene and the resulting solution was
spun in a dry process at a spinning temperature of 34C through
a spinning nozzle having a diameter of 250 ~ into a spinning
tube wherein air was fed in a rate of 2 l/min., at spinning
rate of 100 m/min. to obtain fibers having a diameter of 20 ~.
The spun fibers were heated in air at 200C for 30 minutes under
a tension of 50 g/mm2. The thus treated fibers were subjected
to a preliminary heating by raising the temperature from room
temperature to 800C in 3 hours under a tension of 200 g/mm2
under vacuum (1 x 10 3 mmHg) and then baked by raising the '! ~ '
temperature up to 1,700C at a rate of increase of 200C/hr. ~-~
under argon atmosphere to obtain silicon carbide fibers having
no bent portion. The tensile strength of the silicon carbide
fibers baked at 1,700C was 45 Kg/mm2 and the tensile strength
of the fibers baked at 1,300C was 415 Kg/mm~ and the strength
of the fibers was uniform.
Example 53
100 g of linear polydimethylsilane produced from
dimethyldichlorosilane was fed into an autoclave and heated at
400C under a pressure of 50 atmospheres for 48 hours under
~ .
argon atmosphere. The reaction product was dissolved in ether
-87-
7'~2~
and the insoluble portion was removed and the resulting solution
was evaporated to obtain 58 g of a solid product. This solid
product had an average molecular weight of 1,400 and was
dissolved in 60 cc of hexane and to the resulting solution was
added 400 cc of acetone to obtain an insoluble precipitate in a
yield of 65%. This precipitate was dissolved in toluene and
the toluene solution was filtered to form a spinning solution.
This spinning solution was spun in a dry process through a
spinning nozzle having a diameter of 200 ~ into a spinning
tube wherein air having a partial pressure of benzene of 0.01
was supplied, at a spinning rate of 150 m/min. at a spinning
temperature of 25C into fibers having a diameter of 10 ~.
The spun fibers were heated in air containing ozone at 200C for
15 minutes under a tension of 50 g/mm2. The treated fibers
were subjected to a preliminary heating by raising the
temperature from room temperature to 800C in 4 hours under a
tension of 100 g/mm under argon gas. Then, the fibers were
baked by raising the temperature up to 1,800C at a raising
temperature rate of 200C/hr. under argon atmosphere under a
tension of 100 g/mm to obtain crystalline silicon carbide
fibers. The tensile strength of the fibers baked at 1,000C
was 370 Kg/mm and the tensile strength of the fibers baked at
1,800C was 80 Kg/mm2. The thus obtained silicon carbide fibers
had no bent portion and the tensile strength was uniform and
the fibers were not substantially broken during the spinning.
Example 54
Dimethyldichlorosilane and sodium were reacted in
toluene to obtain an insoluble polysilane compound. 100 g of
this polysilane was charged in an autoclave and air in the
-88-
- ~ -
`7~.2ti
autoclave was substituted with nitrogen gas and the polysilane
was heated at 400C for 36 hours. The resulting product was
dissolved in hexane and the resulting solution was taken out
from the autoclave and filtered and then the hexane was
distilled and removed. 55 g of the formed solid high molecular
weight compounds was obtained. The softening point of the
compounds was 38C, so that the solid compounds were dissolved
in 50 cc of hexane and to the solution was added 385 cc of
acetone and 28 g of precipitate insoluble in acetone was
obtained. 2 parts of the precipitate insoluble in acetone was
mixed with 1 part of the acetone soluble portion and the mixture
was heated and melted and filtered to form a spinning bath,
which was heated at 210C and spun through a nozzle having a
diameter of 300 ~ at a spinning rate of 1,000 m/min. into
fibers having a diameter of 10 ~. The spun fibers were h~ated
from room temperature to 180C in 1 hour and maintained at 180C
for 30 minutes under a tension of 20 g/mm2 in air. The thus
treated fibers were subjected to a preliminary heating by
raising the temperature from room temperature to 800C in
3 hours under a tension of 100 g/mm2 under nitrogen gas.
Subsequently, the thus treated fibers were baked by raising the
temperature from 800C to 1,300C in 2 hours to obtain silicon
carbide fibers. The tensile strength of silicon carbide fibers
baked at l,300C was 380 Kg/mm2 and there was no bent portion
in the fibers, so that the silicon carbide fibers having a
uniform tensile strength were obtained.
Example 55
100 g of dodecamethylcyclohexasilane was fed in an
... .
-89-
~ ~79~`~
autoclave and air in the autoclave was purged with argon gas
and the polycondensation reaction was effected at 400C for
37 hours under a pressure of 40 atmospheres. After completion of
the reaction, the polycondensation product was permitted to
cool at room temperature and then was admixed with ether to
form ether solution. The ether solution was taken out from the
autoclave and the ether was evaporated to obtain 66 g of a
solid high molecular weight compound. The high molecular weight
compounds contained the low molecular weight compounds and the
softening point was lower than 50C. The solid high molecular
weight compounds were heated and aged at 300C for 3 hours
while slowly stirring under argon atmosphere to obtain organic
silicon high molecular weight compounds having a softening
point of 190C.
The resulting organic silicon high molecular weight
compounds were dissolved in xylene and the xylene solution was
spun in a dry process through a spinning nozzle having a diameter
of 300 ~ at a spinning temperature of 25C and at a spinning rate
of 250 m/min. into a spinning tube, wherein air was introduced
into fibers having a diameter of 10 ~. The spun fibers were
heated by raising the temperature from room temperature to 190C
in 1 hour and keeping 190C for 15 minutes under a tension of
50 g/mm2. The thus treated fibers were subjected to the
preliminary heating by raising the temperature from room
temperature to 800C in 4 hours under vacuum while applying a
tension of 200 g/mm2 and further baked by raising the temperature
to 1,600C at a raising temperature rate of 300C./min. under
vacuum. The tensile strength of the fibers baked at 1,200C
--90--
7~t2t~
was 410 Kg/mm2 and the tensile strength of the fibers baked at
1,600C was 105 Kg/mm2 and the fibers had no bent portion and
the tensile strength of the fibers was very uniform.
Example 56
100 g of octaphenylcyclotetrafuran was fed in an
autoclave together with 1 g of benzoyl peroxide and air in the
autoclave was purged with argon gas and the polycondensation was
effected at 350C for 24 hours under a pressure of about 35
atmospheres. After completion of the reaction, hexane was added
to the atuoclave and the polycondensation product was taken out
from the autoclave in the form of the hexane solution. Insoluble
portion in hexane was filtered off and the hexane was evaporated
to obtain 71 g of solid high molecular weight compounds having
an average molecular weight of about 2,000. The high molecular -
weight compounds were dissolved in 200 cc of hexane and to the
hexane solution was added 1,000 cc of acetone to obtain 6.3 g of
acetone insoluble precipitate. The precipitate was dissolved in
toluene and the toluene solution was spun in a dry process through
a spinning nozzle having a diameter of 250 ~ at a spinning
temperature of 30C and at a spinning rate of 150 m/min. into
fibers having a diameter of 10 ~. The spun fibers were heated
in air to 220C for 18 minutes under a tension of 50 g/mm2.
The thus treated fibers were heated by raising the temperature
from room temperature to 800C in ~ hours under argon atmosphere
while applying a tension of 200 g/mm2. Then, the fibers were
baked by raising the temperature up to l,800C in a graphite
crucible to obtain silicon carbide fibers. The tensile strength
of the fibers baked at l,000C was 350 Kg/mm2 and the tensile
~7~2~;
strength of th~ fibers baked at 1,800C was 78 Kg/mm2 and the
fibers had 310 bent portion and the tensile strength was very
uniform.
Example 57
100 g of a mixture of cyclodimethylpolysilanes having
formulae of (Me2Si)5 and (Me2Si)6 was fed in an autoclave together
with 3 g of azoisobutyronitrile and air in the autoclave was
purged with argon gas and the polycondensation was effected at
360C for 12 hours under a pressure of about 80 atmospheres.
After completion of the reaction, benzene was added into an
autoclave and the polycondensation product was taken out from
the autoclave in the form of benzene solution. Insoluble portion
in benzene was filtered off and benzene was evaporated under a
reduced pressure to obtain 48 g of solid high molecular weight
compounds having an average molecular weight of about 1,800.
The high molecular weight compounds were dissolved in 100 cc
of hexane and to the hexane solution was added 700 cc of acetone
to obtain 39 g of acetone insoluble precipitate. The precipitate
was dissolved in xylene and the solution was filtered off to
obtain a spinning solution. This spinning solution was spun in
a dry process through a spinning nozzle having a diameter of
200 ~ at a spinning temperature of 45C and at a spinning rate
of 200 m/min. into a spinning tube, wherein benzene having a
partial pressure of 0.1 was introduced, into fibers having a
diameter of 10 ~.
The spun fibers were heated at 190C in air for
30 minutes under a tension of 50 g/mm2. The thus treated
fibers were subjected to a preliminary heating by raising the
-92-
~37~2~:i
temperature from room temperature to 800C in 4 hours while
applying a t~nsion of 200 g/mm2 al~d then baked by raising the
temperature up to 1,300C at a rate of increase of 200C/hr.
under a tension of 100 g/mm2 to obtain silicon carbide fibers.
The tensile strength of the fibers baked at 1,300C was 410 Kg/~
mm . The above described silicon carbide fibers had no bent
portion and the tensile strength of the fibers was very uniform.
Example 58
100 g of a mixture of cyclophenylsilanes having the
formulae of (Ph2Si)4 and (Ph2Si)5 and linear polydiphenylsilane
was fed into an autoclave and air in the autoclave was purged
with nitrogen gas and the polycondensation was effected at
380C for 50 hours under a pressure of about 60 atmospheres.
After completion of the reaction, benzene was added into the
autoclave and the polycondensation product was taken out from
the autoclave in the form of benzene solution and the benzene
solution was concentrated under a reduced pressure to obtain
69 g of the solid high molecular weight compounds. The result-
ing high molecular weight compounds were dissolved in 100 cc of
benzene and to the benzene solution was added 700 cc of acetone
to obtain 48 g of acetone insoluble precipitate. The precipitate
was dissolved in benzene and the benzene solution was spun in a
dry process through a spinning nozzle having a diameter of
300 ~ into a spinning tube wherein air was introduced, at a
spinning temperature of 25C and at a spinning rate of
100 m/min., into fibers having a diameter oE about 10 ~
The spun fibers were heated at 200C for 15 minutes
in air containing ozone gas under a tension of 50 g/mm2. The
-93-
7~Z~i
thus treated fibers were subjected to a preliminary heating by
gradually raisillg the temperature up to 800C in 4 hours under
argon gas while applying a tension of 500 g/mm2. The fibers
were baked by raising the temperature up to l,800C under vacuum
to obtain silicon carbide fibers. The silicon carbide fibers
were heated at 800C for 0.5 hour in air. The tensile strength
of the fibers baked at 1,300C was 410 Kg/mm2 and the tensile
strength of the fibers baked at l,800C was 73 Kg/mm2. The
above described silicon carbide fibers had no bent portion and
the tensile strength of the fibers was very uniform.
Example 59
From hexamethyldisilane was produced the organosilicon
high molecular weight compounds according to the present
invention by using the apparatus as shown in Figure 1 under
atmospheric pressure. Namely, hexamethyldisilane was fed in a
fluid form into a reaction column heated at 850C at a feeding
rate o 1 l/hr. together with argon gas. The starting hexa-
methyldisilane was subjected to decomposition and polycondensa-
tion reaction in the heated reaction column and formed into high
molecular weight compounds and at the same time low molecular
weight compounds were formed. A part of the resulting high
molecular weight compounds was able to be taken out from the
; heated reaction column but the major part of the high molecular
weight compounds was fed into a separating column together with
the low molecular weight compounds and in the separating
column, gases and the low molecular weight compounds were
separated from the high molecular weight compounds. The low
molecular weight compounds were again fed into the reaction
-94-
~7~2~i
column and used as a rec~cling material. The operation was
continued for 10 hours and 5.4 Kg of high molecular weight
compounds having an average molecular weight of about 1,500 was
obtained.
From 100 g of the resulting high molecular weight
compounds, ethyl alcohol soluble portion was removed by means
of Soxhlet's extractor to obtain 78 g of ethyl alcohol
insoluble portion, which was used as a spinning material. The
ethyl alcohol insoluble portion was dissolved in xylene and
the solution was heated to 45C and spun through a spinning
nozzle having a diameter of 250 ~ at a spinning rate of
100 m/min. into fibers having a diameter of about 10 ~. The
spun fibers were heated by raising the temperature from room
temperature to 200C in 30 minutes in air under a tension
of 50 g/mm2.
The thus treated fibers were subjected to a
preliminary heating by raising the temperature up to 800C
in 4 hours under a tension of 150 g/mm2 under vacuum. The
thus treated fibers were baked by raising the temperature up to
1,400C under argon atmosphere under a tension of 100 g/mm2 to
obtain silicon carbide fibers. The tensile strength of the
obtained fibers was 430 Kg/mm2. The silicon carbide fibers had
no bent portion and the tensile strength of long fiber was very
uniform.
Example 60
An apparatus for producing silicon carbide fibers as
shown in Figure 24 was used and the entire gaseous contents of
the apparatus was substituted with nitrogen. A mixed starting
~L07'~
material of about 65~ of dimethyldichlorosilane, about 25% of
methyltrichlorosilane, about 5% oE trimethylchlorosilane and
about 5% of the other substances was charged in a reaction column
1 heated at 750C at a rate of 1 l/hr. to effect a thermal
polycondensation reaction, whereby high molecular weight compounds
and others were obtained. The reaction product was introduced
into a distillation column 2, wherein the gases consisting
mainly of methane and hydrogen were separated from liquid and
high molecular weight compounds. Among them the gas was
discharged out of the system and the liquid was again fed into
the reaction column as a recycling material.
The yield of the above high molecular weight polymer
was 34% and the average molecular weight was about 1,300 and
the softening temperature was 35C.
The high molecular weight compounds were aged at
280C in nitrogen atmosphere for 4 hours, filtered and then
spun through a spinning nozzle of 300 ~ at 190C at a rate of
1,000 m/min. into fibers having a diameter of 20 ~. In this
case, hot air was blown into the spinning tube. These spun
fibers were heated up to 150C in air containing ozone under a
tension of 150 g/mm2 in 30 minutes and then maintained at 210C
in air for 15 minutes. The thus treated fibers were heated
from room temperature up to 800C in nitrogen atmosphere under
a tension of 500 g/mm2 in 3 hours and then baked up to 1,400C
under argon atmosphere to form silicon carbide fibers. The
silicon carbide fibers had a tensile strength of 390 Kg/mm2 and
uniformity of the tensile strength was very good because of no
bent portion.
-96-
~1~g7~2~
Example 61
Organosilicon high molecular weight compounds were
produced starting from dimethyldichlorosilane in the same manner
as described in Example 60.
The dimethyldichlorosilane was charged in the
reaction column 1 heated at 780C at a rate of 1 l/hr. The
reaction product was introduced into the distillation column 2,
wherein the gases consisting mainly of methane and hydrogen
were separated from liquid and high molecular weight polymers.
The yield of the above high molecular weight polymer
was 24% and the average molecular weight was about 1,400, and
the softening temperature was 45C.
The high molecular weight polymer was aged at 210C
in air for 2 hours with slow stirring to obtain a high molecular
weight compound having a softening temperature of 180C. This
high molecular weight compound was melted and filtered to
obtain a spinning solution, which was spun into fibers having a
diameter of 15 ~ through nozzles of 300 ~ at a spinning
temperature of 200C at a spinning tube rate of 500 m/min. while
blowing hot air into a spinning tube. These spun flbers were
heated from room temperature up to 190C in air under a tension
of 50 g/mm2 in 1 hour and maintained at 190C for 30 minutes
and subjected to a preliminary heating from room temperature up
to 800C in argon atmosphere under a tension of 200 g/mm2 in
3 hours and further baked up to 1,700C under argon atmosphere at
a rate of 200C/hr. to form silicon carbide fibers. The tensile
strength of the fibers baked at 1,300C was 400 Kg/mm2 and the
tensile strength of the fibersbaked at l,700C was 85 Kg/mm2.
-97-
7~
The silicon carbide fibers had good strength properties because
of no bent portion.
Example 62
Poly(silmethylenesiloxane) having the following formula
and an average molecular weight of about 8,000 was used as a
starting material.
CIH3 IH3
~Si - CH2 - Si - 0~
CH3 3
The softening point of the above described high
molecular weight compound was higher than 50C and this
compound was melted and filtered to obtain a spinning melt.
This melt was spun through a spinning nozzle having a diameter
of 300 ~ at a spinning temperature of 150C and a spinning
rate of 500 m/min. into fibers having a diameter of 15 ~.
The spun fibers were heated by raising the temperature from room
temperature to 150 C in 1 hour and maintaining 150C for 30
minutes in air containing ozone under a tension of 100 g/mm2.
The thus treated fibers were subjected to a preliminary heating
by raising the temperature from room temperature to 800C
in 3 hours under vacuum and succeedingly, the temperature was
raised to 1,400C at a raising temperature rate of 200C/hr.
to bake the fibers, whereby silicon carbide fibers were obtained.
The tensile strength of the fibers baked at 1,400C was
390 Kg/mm and the fibers had no bent portion, so that tensile
strength was very uniform.
-98-
~ ~ 017~26
Example 63
Poly(silarylenesiloxane) having the following formula
and an average ~olecular weight of 12,000 was used as a starting
material.
~ O - S - O ~
The softening point of the above described high
molecular weight compound was 180C and was melted and filtered
to prepare a spinning melt. This melt was spun at a spinning
temperature of 203C through a spinning nozzle having a
diameter of 250 ~ at a spinning rate of 1,000 m/min. into
fibers having a diameter of 10 ~.
The spun fibers were heated by raising temperature
to 180 C in 1.5 hours and keeping 180C for 15 minutes in air
under a tension of 200 g/mm2, subjected to a preliminary heating
by raising the temperature from room temperature to 800C
in 3 hours under a tension of 400 g/mm in nitrogen gas. The
thus treated fibers were baked by raising the temperature up
to 1,700C at a raising temperature rate of 200C/hr. under
argon gas to obtain silicon carbide fibers. In the above
described silicon carbide fibers, the tensile strength of the
fibers baked at l,000C was 340 Kg/mm2, the tensile strength of
the fibers baked at 1,300C was 380 Kg/mm2 and the tensile
strength of the fibers baked at 1,700~ was 65 Kg/mm2. The
fibers had no bent portion and the tensile strength in the long
fibers was very uniform.
_99_
7¢3~
Example 64
Polysilmethylene having the following Eormula and
an average molecular weight of about 4,000 was used as a
starting material.
IH3
[ Si - CH
CH3
The above described high molecular weight compound had
a softening point of lower than 50C and was aged at 390C
for 2 hours under a nitrogen gas and then filtered to prepare
a spinning melt. This melt was spun through a spinning nozzle
having a diameter of 200 ~ at a spinning temperature of 180C
and a spinning rate of 150 m/min. into fibers having a diameter
of 10 ~. The spun fibers were heated by raising the temperature
from room temperature to 160C in 2 hours in air and then
subjected to a preliminary heating by passing through an oven
having a length of 1 m, wherein the center portion was heated
at 800C, while applying a tension of 500 g/mm2 under a
nitrogen gas.
The thus treated fibers were baked by passing through
an oven having a length of 2 m where the center portion was
2Q heated at 1,300C under argon gas to obtain silicon carbide
fibers. The tensile strength of the fibers baked at 1,300C
was 340 Kg/mm2 and the fibers had no bent portion and the
tensile strength in the long fibers was very uniform.
Example 65
Polysiltrimethylene having the following formula and
an average molecular weight of about 6,00G was used as a
--100--
' , `
~792~;
starting material.
CH3
C 2 2
CH3
The above described polymer was heated and melted
and then filtered. The filtered melt was spun through a
spinning nozzle having a diameter of 240 ~ at a spinning
temperature of 140C and a spinning rate of i,200 m/min. into
fibers having a diameter of 10 ~.
The spun fibers were heated by raising the
temperature to 130C in 1 hour and keeping 130C for 15
minutes in air containing ozone under a tension of 150 Kg/mm
and then subjected to a preliminary heating by raising the
temperature from room temperature up to 800C in 3 hours
under vacuum. The thus treated fibers were baked by raising
the temperature to 1,600C at a rate of increase of 200C/hr.
in argon gas to obtain silicon carbide fibers. The tensile
strength of the fibers baked at l,000C was 310 Kg/mm2, the
tensile strength of the fibers baked at l,300C was 380 Kg/mm2
and the tensile strength of the fibers baked at 1,600C
was 108 Kg/mm2. The fibers had no bent portion and the tensile
strength of the fibers was very uniform.
Example 66
250 g of polysilane was charged into an autoclave
of 1 Q and air in the autoclave was purged with argon gas and
said polysilane was reacted at 470C for 14 hours while
stirring. The reaction product was dissolved in n-hexane and
--101--
7~
such a solution was taken out from the autoclave and filtered.
Then, n-hexane was removed by reducing pressure by means of an
aspirator to ~orm a viscous product. This product was
concentrated at 260C under vacuum to obtain 130 g of silicon
high molecular weight compounds having a softening point of
230C and an intrinsic viscosity of 0.5.
The high molecular weight compounds were heated to
280C and spun through a spinning nozzle having a diameter of
300 ~ at a spinning rate of 300 m/min. into fibers. The spun
fibers were heated by raising the temperature from 10C to
150C in 2.5 hours and from 150C to 180C in 30 minutes and
keeping 180C for 30 minutes under air under a tension of
20 g/mm to form oxide layer on the fiber surface. The thus
treated fibers were baked by raising the temperature to 1,300C
at a rate of increase of 100C/hr. under a tension of 200 g/mm2
under vacuum and maintaining 1,300C for 1 hour to obtain
silicon carbide fibers. The tensile strength of the fibers
was 350 Kg/mm2 and the Young's modulus was 28 ton/mm2.
The silicon carbide fibers of the present invention
having the tensile strength comparable with 300-400 Kg/mm2
- of piano wire, which is the highest in the tensile strength
among steel materials, can be easily obtained and the specific
gravity was about 3Ø The acid resistance, antioxidation
and heat resistance of the fibers are excellent and the
wetting to metals and alloys is better than that of carbon
fibers and the reactivity with metals and alloys is poor, so
that the fibers are very useful for fibrous materials of fiber
reinforced metals, plastics and rubbers, electric heating
-102-
. .
,
.
7~
fibers, fire proof cloth, acid resistant membrane, atomic
furnace material, airplane constructlon material, bridges,
building material, nuclear fusion furnace material, rocket
material, radiation element, abrasive cloth, wire rope, marine
developing material, golf shaft material, sky stock material,
tennis racket material, fishing rods, shoe bottom materials
and the like.
-103-
