Note: Descriptions are shown in the official language in which they were submitted.
The present invention relates to polysiloxane polymers and more
particularly to thiofunctional polysiloxane polymers and to a process for
preparing the same.
Heretofore, sulfur-containing compounds have been prepared by re-
acting hydroxyl-terminated dimethylpolysiloxane fluids with a methoxy-contain-
:Lng silacyclopentane thiol in the presence of an acid clay to affect the
condensation reaction of the sulfur-containing silane and the dimethylpoly-
siloxane. In the condensation reaction, the acid clay not only catalyzes
the condensation between the methoxy groups of the sulfur-containing com-
pound and the hydroxyl groups of the dimethylpolysiloxane but also catalyzes
the condensation between hydroxyl groups to form a mixture of compounds.
Furthermore, the process requires that a preformed hydroxyl-terminated di-
methylpolysiloxane fluid be prepared prior to the condensation reaction.
Viventi discloses in U.S. Patent No. 3,346,405, a process for
preparing sulfur ~ntaining siloxanes by reacting sodium sulfohydride with
-chloroalkyl containing organopolysiloxanes in the presence of dimethyl-
formamide. Also, U.S. Patent No. 2,960,492 to Morton et al disclose a
process for preparing sulfur containing organopolysiloxanes by re~cting a
vinyl containing siloxane with a mercaptan to form an adduct therewith by
- 20 combining the sulfohydride group with the unsaturated vinyl group of the
siloxane. U.S. Patent 3,388,144 to Musolf et al discloses reacting a silox-
ane containing one or two mercaptoalkyl groups per silicon atom with a
polyhydroxylated carbon compound containing an unsaturated olefin group in
the presence of a peroxide catalyst.
The above described processes for preparing thiofunctional silox-
ane polymers have several disadvantages. For example, long reaction times
are required. Also, siloxanes having chloroalkyl groups or vinyl unsatura-
tion are required as one of the reactants. Moreover, it is very difficult
to obtain complete conversion of the chloroalkyl groups or vinyl groups to
-- 2 --
73~
thiofunctional groups; thus polymers having both functional groups are
obtained from the above proces-ses~
U.S. Patent No. 4,046,795 to Martin discloses a process for pre-
paring thofunctional polysiloxane polymers by reacting a disiloxane and/or
a hydroxy or hydrocarbonoxy containing silane or siloxane with a cyclic
trisiloxane in the presence of an acid catalyst, in which at least one of
the silanes or siloxanes contains a thiol group. However, when a cyclic
siloxane containing more than three silicon atoms, e.g., octamethylcyclo-
tetrasilane, is substituted for hexamethylcyclotrisiloxane, there is no
detectable reaction observed in the presence of an acid catalyst.
Therefore, it is an object of one aspect of this invention to
provide a process for preparing thioEunctional polysiloxane polymers which
do not require vinyl unsaturation or chloroalkyl substituents.
An object of a further aspect of this invention is to provide a
process for preparing a broad spectrum of thiofunctional polysiloxanes
from siloxanes having more than three silicon atoms per molecule in the
presence of an acîd catalyst.
In accordance with aspects of this invention, a process is pro-
vided for preparing thiofunctional polysiloxane polymers which comprises:
(1) reacting a cyclic trisiloxane with a hydroxy or hydrocarbonoxy con-
taining organosilicon oompound selected from the group consisting of
silanes and siloxanes in the pre ence of a catalyst having a pK value below
1, in which one of the silicon reactants contains at least one thiol group,
to form a thiofunctional copolymer having at least one unit of the formula
R
e(R"S)yRl:]f - SiO4 f g
and the other units are selected from the formulas R2SiO, R3SiOo 5 and
ROo 5 and thereafter (2) equïlibrating the thionfunctional polysiloxane
copolymer with an organopolysiloxane containing at least four silicon
, -3_
' ' ' ,
~12~
atoms per molecule i~ the presence of an acid catalyst having a pK value of
less than 1 in an aqueous solution, in which R is a monovalent hydrocarbon
radical having from 1 to 18 carbon atoms, R' is a substituted or unsub-
stituted divalent, trivalent or tetravalent hydrocarbon radical free of
aliphatic unsaturation having from l to 18 carbon atoms, hydrocarbon ether,
hydrocarbon thioether, hydrocarbon ester and hydrocarbon thioester radicals,
R" is a monovalent hydrocarbon radical or hydrogen, f is a number of from l
to 3, and g is a number of from 0 to 1 and the sum of f + g is from 1 to 3,
and y is a number of from 1 to 3.
By a variant thereof, the mixture also contains (3) up to 35 per-
cent by weight oE an organopolysiloxane having less than four silicon
atoms in the molecule based on the weight of siloxanes (1) and (3).
By another variant, the acid catalyst is present in an amount of
from 0.003 percent up to lO percent by weight based on the weight of the
organopolysiloxane and thiofunctional polysiloxane copolymers.
By a further variant, the equilibration is conducted at a
temperature of from 25C. up to 200C.
By another variant, the equilibration is conducted in the presence
of a protic compound.
; 20 By a further variant, the equilibration is conducted in the pre-
sence of a hydrocarbon solvent.
- By yet another variant3 the organopolysiloxane (1) is a cyclic
siloxane havirg at least four carbon atoms.
By a still further variant, the organopolysiloxane (1) is a
linear organopolysiloxane.
By other aspects of this invention, each of the aspects and
variants of $he process provides a novel product.
Surprisingly, it has been found that the thiofunctional poly-
siloxane polymers prepared in accordance with U.S. Patent No. 4,046,795 will
- 4 -
39~4
further react with siloxanes having more than three carhon atoms in the
molecule in the presence of an acid catalyst to form higher molecular
weight thiofunctional polysiloxane polymers. This process is of commercial
': ,
' :
.: .
~
.
A - 4a -
~lZ~34~
significance since it now provides a means for utilizing organopolysiloxanes
e.g. cyclic siloxanes having more than three silicon atoms per molecule
in the preparation of thiofunctional polysiloxane polymers.
Organopolysiloxanes (1) which may be reacted with the thiofunction-
al polysiloxane copolymers are cyclic or linear organopolysiloxanes having
the general formula
R
. ' ` . --S iO--
z
where R is a monovalent hydrocarbon radical or a halogenated monovalent hy-
drocarbon radical having up to 18 carbon atoms and z is a number of at least
4 and up to 20,000.
Examples of suitable monovalent,hydrocarbon radicals represented
by R ara alkyl radicals, e.g. methylJ ethyl, propyl, butyl, pentyl, hexyl,
.
octyl, decyl and octadecyl radicals; aryl radicals e.g. phenyl, diphenyl
and naphthyl radicals; alkaryl radicals e.g. tolyl, xylyl and ethylphenyl
radicals; aralkyl radicals e.g. ben~yl~ c~ -phenylethyl, ~ -phenylethyl,
C~ -phenylbutyl radicals; cycloalkyl radicals, e.g. cyclobutyl, cyclopentyl,
cyclohexyl radicals and halogenated hydrocarbon radicals, e.g. chloromethyl,
bromoethyl, tetrafluoroethyl, fluoroethyl, trifluorotolyl, and hexafluoro-
xylyl radicals.
Examples of preferred cyclic organopolysiloxanes (1) are octa-
methylcyclotetrasiloxane, octaethylcyclotetrasiloxane, octabutylcyclotetra-
siloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane,
tetradecamethylcycloheptasiloxane, hexadecamethylcyclooctasiloxane, octa-
decamethylcyclononasiloxane and eicosamethylcyclodecasiloxane.
Examples of other organopolysiloxanes which may be used are
those represented by the unit formula
R SiO
n 4-n
~LZ73~D~
wherein each R is the same as above and n has an average value of from
1.95 to 2.01. These organopolysiloxanes have terminal triorganosiloxy
units and consist essentially of the same or different chemically combined
siloxy units having an average of two organic radicals attached to the sili-
COD atom. Diorganosiloxane units predominate in such polymers and consti-
tute more than 50 molar percent or more of the units present. However,
limited amounts of monorganosiloxane units and triorganosiloxane units can
be present so long as the average organic substituent to silicon ratio re-
mains within the prescribed limits. All of the organic substituents in the
polymer can be the same or different. It is preferred that at least 50
percent of the substituents be methyl radicals. Mixtures of polymers as
well as copo~ymers can be employed. The operative polymers have a viscosity
in the range of from 5 cs. to 500,000 cs, at 25C and more preferably from
about 50 to 300,000 cs. at 25C.
- Suitable examples of linear or branched organopolysiloxanes (1)
which may be employed in the process of aspects of this invention are deca-
methyltetrasiloxane, tetradecamethylhexasiloxane, octadecamethyloctasiloxane,
eicosamethylnonisiloxanç and organopolysiloxanes consisting essentially of
dimethylsiloxy units, or a mixture of chemically combined dimethylsiloxy
units and phenylsiloxy units, e.g. methylphçnylsiloxy units and diphçnyl-
; siloxy units.
In the equilibration, thç mixturç may also contain (3) siloxanes
having less than four silicon atoms in the molecule in combination with
the organopolysiloxanes (1) having at least four silicon atoms in the
molecule. Thus, where a mixture of siloxanes is employed, the siloxanes
having less than four silicon atoms in the molecule may be present in an
amount of from 0 to 35 percPnt by weight based on the weight of the
siloxanes having less than four silicon atoms per molecule and those having
at least four silicon atoms per molecule. In any event, the organopoly-
l~Z739Lf~ "
; ; .
siloxanes (1) having at least four silicon atoms in the molecule should be
present in an amount of at least 65 percent by weight based on the weight
. .
of the siloxane (3) having less than four silicon atoms per molecule and
those slloxanes (1) having at least four silicon atoms per molecule.
Examples of siloxanes ~3) having less than four silicon atoms per
molecule are disiloxanes, e.g., hexamethyldisiloxane, hexapropyldisiloxane,
hexabutyldisiloxane and trisiloxanes, e.g. octamethyltrisiloxane, octabutyl-
trisiloxane, hexamethylcyclotrisiloxane, hexabutylcyclotrisiloxane and
1,2,3-trimethyl-1,2,3-triphenylcyclotrisiloxane.
The thiofunctional polysiloxane copolymers (2) which are equili-
brated w~th the organopolysiloxanes (1) having at least four silicon atoms
'~ per molecule are prepared in accordance with the procedure described in
U.S. Patent No. 4,04~,795 to Martin in which a cyclic-trisiloxane is reacted
with a disiloxane and/or a hydroxy or hydrocarbonoxy containing silane or
siloxane in the presence of an acid catalyst in which at least one of the
above organosilicon compounds contain a thiol group.
Cyclic trisiloxanes employed in the preparation of thiofunctional
polysiloxane copolymers (2) are those represen~ed by the general formula
~ - . . .
I 6-a
(~ Si 0
where R is the same as above, M is a group represented by the formula
R'(SR"~)y and
. .
R"'
f___ ~ SR"
~ - R~
where Rl is a substituted or unsubstituted divalent, trivalent or tetrava-
lent hydrocarbon radical free of aliphatic unsaturation having from 1 to 18
carbon atoms, hydrocarbon ether, hydrocarbon
~;27~
hioether, hydrocarbon ester, and hydrocarbon thioester radicals in which R'
is attached to the silicon atom via a silicon-carbon bond, R" is hydrogen
or a monovalent hydrocarbon xadical having from 1 to 18 carbon atoms, R"'
which may be the same as R" or a radical represented by the formula
R""X, where X is
O
11
HC- ,
~ -~OCR, OH or a cyanoalkyl radical, R"" is a divalent hydrocarbon radical free
: of aliphatic unsatuxation having from 1 to 18 càrbon atoms, a is a number
of from O to 6 and y is a number of from 1 to 3.
Disiloxanes which may be employed in the preparation of the thio-
functional polysiloxane copolymers (2) ;may be represented by the formula
)6-a
(M) - Si O
: ~here R, M and a are the same as above.
Suitable examples of silanes or siloxanes which may be reacted
with the cyclic trisiloxanes or mixtures:of the cyclic trisiloxanes and di-
: siloxanes to form the thiofunctional polysiloxane compolymers (2) are silanes
of the general formula
~c
(M3b-Si(OR )4-(b+c)
or siloxanes of the general formula
~ 1 1 r I 1 l3-e~
Y- - SiO - _ _ - SiO - SiSOR")e
Md R _
m~ . n
- 8 -
~z~
where R, R" and M are the same as above, Y is a radical of the formula
3 0.5
~R3-e
(R")eSil/2
where R and R" are the same as above, b is a number of from O to 3, c is a
number of from O to 3 and the sum of b + c is from 1 to 2, d is a number of
~ from O to 2, e is a number of from 1 to 3, m and n are each equal to a num-
-~ ber of from O to 999 and the sum of m + n is at least 1.
Examples of suitable divalent hydrocarbon radicals represented
by R' and R"" are ethylene, trimethylene, tetramethylene, hexamethylene,
octamethylene and the like. Suitable examples of trivalent and tetravalent
hydrocarbon radicals are represented by the formula =CHCH2-, =CHCH2CH2-,
=CH(CH2)3-, =CH(CH2)4-, =CH(CH2)17-,
, =CHCH-,
CH3
,~.,
~: = C(CH2)2-
C2H5
2 2)2 ' C(CH2)3-1 -C(CH2)17-~ -CCHCH2-, -CCH(CH ) -
CH3 C2H5
and the like.
Suitable examples of monovalent hydrocarbon radicals represented
by R" are alkyl radicals, e.g. methyl, ethyl, propyl, butyl, pentyl,
hexyl, octyl, decyl, octadecyl, aryl radicals, e.g. tolyl, xylyl and ethyl-
phenyl; aralkyl radicals, e.g. benzyl, ~ -phenylethyl, ~ -phenylethyl,
~-phenylbutyl and cycloalkyl radicals, e.g. cyclobutyl, cyclopentyl and
cyclohexyl.
_ g _
:: :
~Z~ 4
Suitable examples of R'(S~"') groups include -CH2SH, ~C2H4SH,
3 6 2 4 9~ C2H4sc2H5r -C3H6sc6H5r (HSCH2)2CHCH CH -
(HSCH2CH2)(HSCH2)CH(CH2)4--,(HSCH2CH2)3CCH2CH2--,(HSCH2CH2)(HSCH2)CHCH--
(CH2SH)CH2CH2CH2-' HS (CH2) 5CH(CH2CH2SH)CH2CH2CH (ci~H2CH3)-r ~HSCH2CH2)2-
CHCH CH -, (HSCH2)2CHSCH2CH2CH2-, (HSCH2)2( 2 5 2 2 2 3
(HSCH2)3CCH2SCH2CH2CH2-, (HSCH2)(HSCH2CH2CH2CH2)CHSCH2CH2CH2-,
HScH2cH2)2cHcH2scH2cH2CH2-, (HSCH2)2(C2H5CCH2SCH2CH2s(cH2)3-r
(HSCH2)3CcH2s(cH2)3s( 2 3 S
~ 2)3CHcH3cH2cscH2cH2cH2-~ -
,.
lSI
(~SCH.2~ 3CCH2cscH`2cH2cH2 .'
., . : . , S~
. ( 2~2C 2 .5) 2 2 2CH2 ,
(HscH2?2(c2Hs)ccu2scH2cH(cH3~cocH2cH2cH2-.
' O . . ,
(~SCH2)3CCH2SCH2CH(C~3?COCH2CH2CH2-, .
' ', ' ' O O O
~C~ ~ S(cH2)~cocH3j (CH2)3s(c~2~2 ' 2 3
(~2)3S(CH2)2CN and the llke. -
Hydroxy and hydrocarbonoxy containing silanes which may be used
to prepare the thiofunctional polysiloxane copolymer (2) ~mployed in the
process of aspects of this invention are silanes, e.g. 3-mercaptopropyl-
trimethoxysilane, 2-mercaptoethyltriethoxysilane, ~J-mercaptodecyltri-
ethoxysilane, ~v -mercaptoamyltriethoxysilane, 2-(triethoxysilyl)ethyl
butyl
- 10--
1~2~3~
~ . .
thioether, 3-~trimethoxysilyl)-propyl butyl thioether, ~-(triethoxysilyl)
butyl methyl thioe~her, 2-(methyldiethoxysilyl)ethyl methyl thioether, 2-
. .
- (methyldiethoxysilyl)ethyl phenyl thioether, 2-(methyldiethoxysilyl)ethyl
dodecyl thioether~ 6-(trimethoxysilyl)hexyl ethyl thioether, ~ethyltri-
ethoxysilane, dimethyldiethoxysilane, trimethylethoxysilane, dimethylsilane
diol, diphenylsilane diol and the like.
Also, the corresponding siloxanes or copolymers thereof which
contain at least one or more alkoxy or hydroxy groups may be employed in
the preparation of the thiofunctional polymers. Suitable examples of these
- 10 polysiloxanes are monoethoxy endblocked beta-mercaptoethylpropylpolysilox-
ane or methyldiethoxy silyl endblocked beta-mercaptobutylmethylpolysiloxane,
monohydroxy endblocked beta-mercaptoethyl methyl polysiloxane, dihydroxy
endblocked dimethylpolysiloxane and diethoxy-endblocked dimethylpolysilox-
ane.
These polysiloxanes may be prepared either by the cohydrolysis
and condensation of trialkylalkoxysilanes with thiol containing organopoly-
siloxanes or by the equilibration of cyclic thiol containing organopoly-
- siloxanes with silicon atoms containing predominantly silicon-bQnded alkoxy
groups.
Other hydroxy and/or hydrocarbonoxy silicon compounds which may
be employed as one of the initial reactants with the cyclic trisiloxane
or mixture of cyclic trisiloxane and disiloxane are the silacyclopentane
thiol compounds disciosed in U.S. Patent 3,655,713 to Le Grow.
Examples of suitable cyclic trisiloxanes which may be used in the
preparation of the thiofunctional polymers (2) used in the process of as-
pects of the present invention are hexamethylcyclotrisiloxane, hexaethyl-
trisiloxane, hexaphenyltrisiloxane, hexabutyltrisiloxane~ hexaoctyltrisilox-
ane, l,2,3-trimethyl-1,2,3 triphenylcyclotrisiloxane and the like.
The thiofunctional polysiloxane polymers of aspects of this in-
-- 11 --
~1~7;~44
vention are prepared according to other aspects of this invention by
equilibrating (1) an organopolysiloxane having at least four silicon atoms
per molecule or a mixture of organopolysiloxanes in which at least 65 per-
cent by weight of the mixture consists of organopolysiloxanes having at
least four silicon atoms per molecule and (2) a thiofunctional polysiloxane
copolymer in the presence of acid catalysts.
Catalysts which may be employed in affecting the equilibration
are acid clays and organic and inorganic acids having a pK value less than
1.0 and more preferably below 0.7 in aqueous solutions. Suitable acid
catalysts which may be employed are benzosulfonic acid, para-toluenesulfonic
acid, sulfuric acid, sulfurous acid, nitric acid, perchloric acid, hydro-
chloric acid~and acid clays, e.g, those known by the Trade Mark FILTROL
No. 13 and No. 24 (available from Filtrol Corporation).
_ _ _ _ _ . _, . . . . .. , _ .. _ . . . . . _ _ . .
Although the amount of catalyst is not critlcal, it is preferred
that from about 0.003 percent up to 10 percent by weight of catalyst based
on the total weight of the reactants, i.e., the organopolysiloxane (1), the
thiofunctional polysiloxane copolymer (2) and organopolysiloxane (3) be em-
ployed. Greater amounts of catalyst may be used; however, it is the intent
of aspects of this invention to provide a catalyst system which does not
alter the functionality of the resultant composition.
- Generally, it is desirable to remove or destroy the catalysts
after the equilibration is complete because their presence will adversely
affect the properties of the resulting polymer. The catalysts may be re-
moved, for example, by washing with water or they may be destroyed by
neutralizing with basic reagents. In addition, certain catalysts, for ex-
ample acid clays, may be removed by filter~ng the reaction mixture.
The equilibration may be conducted at any temperature ranging
from 25~ up to 200C over a period of time ranging from 0.5 hour up to
several days and, if desired, in the presence of a hydrocarbon solvent.
Under certain conditions, for example, when an anhydrous acid catalyst is
- 12 -
. .
~127~4~L
. , .
employed, a catalytic amount of a protic compound is required to effect
the equlllbration. The term "protic compound" refers to compounds having
a reactive hydrogen, for example, alcohols, e.g., methanol, ethanol, propan-
ol, butanol and water. The amount of protic compound is not critical and
may range from 0.0001 to 10 percent based on the total weight of the silane
and siloxane reactants.
The equilibration may be conducted in the absence of a solvent;
however, when a solvent i8 ~employed, it may be employed in an amount of
from 1 to ~0 percent by weight based on the weight of the reactants. Ex-
amples of suitable hydrocarbon solvents are heptane, benzene, toluene,xylene and the like. Moreover, it is preferred that the reaction be conduc-
ted in an inert atmosphere.
The thiofunctional polysiloxane polymers of aspects of this in-
vention may be used as metal protectants and as release agents on metal
substrates. These compositions may be applied to metal surfaces to-improve
their resistance to corrosion and to high temperature oxidation. Also,
these compositions are useful in duplicating machines, as coating agents
and as release agents.
The thiofunctional polysiloxane copolymers (2) employed in the
equilibration reaction with the organopoIysiloxanes (l) having at least
four carbon atoms are prepared in the following manner in which all parts
are by weight.
(A) To a one liter reaction vessel is added 243 parts of hexa-
methyldisiloxane, 196 parts of 3-mercaptopropyltrimethoxysilane, 196 parts
of water, 100 parts of heptane and 5 parts of FILTROL No; 13 acid clay
(available from Filtrol Corporation). The vessel is heated to 80C and
maintained at this temperature for three hours. The contents of the vessel
are then cooled to room temperature and filtered. The volatiles are re-
moved by heating for 2 hours at 150C at less than 1 torr. A clear~
~ ~LZ~
transparent liquid is obtained having a viscosity of 871 cs. at 25C.
Nuclear Magnetic Resonance (N~R~ analysis shows that the product has a mol
ratio of CH2S HSC3H6 si CH3H6 si CH3 of 1.0:1.0:2.43.
The SH content of the product is 14.4 percent.
~ B) To a reaction vessel are added 79.7 parts of hexamethyl-
cyclotrisiloxane and 6.2 parts of heptane. The vessel is heated to 70C,
then 4.9 parts of 3-mercaptopropyltrimethoxysilane, 4.9 parts of water,
2.9 parts of hexamethyldisiloxane and 1.5 parts of acid clay (FILTROL No.
13) are added to the vessel. The reactants are heated to 80~C and main-
tained at this temperature for three hours. The contents of the vessel are
- cooled to room temperature and filtered. The volatiles a~e then removed
at 185C at less than 1 torr.
A clear transparent liquid is obtained having a viscosity of
97.3 cs. at 25C and an SH content of 0.975 percent. Nuclear Magnetic
Resonance (NMR) analysis shows that the product has a mol ratio of CH2S:
Si(cH3)2 of 1:52.6.
Embodiments of this invention are further illustrated by the fol-
lowing examples in which all parts are by weight unless otherwise specified.
EXAMPLE 1
To a reaction vessel containing 84.4 parts of the thiofunctional
polysiloxane copolymer prepared in accordance with (A) above, are added
1184 parts of octamethylcyclotetrasiloxane, 21.5 parts of hexamethyldisilox-
ane and 25.8 parts of acid clay (FILTROL No. 13) and heated to 80C for
three hours. The contents of the reaction vessel are cooled to 45C and
vacuum filtered. The filtrate is heated to 185C at 1 torr to remove the
volatiles. A-clear transparent liquid is obtained having a viscosity of
71.2 cs. at 25C and an SH content of 1.26 percent. Nuclear Magnetic
Resonance (N~R) analysis shows that the product has a mol ratio of CH2S:
CH2 Si(CH3)2 of 1 -73 2-2-
- 14 -
~ ~.;Z73~
. .
~ EXAMPLE 2
:~ .
To a reaction vessel containing 200 parts of the thiofunctional
polysiloxane copolymer prepared in accordance with (B) above, are added
200 parts of a trimethylsiloxy-terminated dimethylpolysiloxane having a
viscosity of 1000 cs. at 25C and 8 parts of acid clay (FILTROL No. 13) and
heated to 155C for six hours. The contents of the vessel are cooled to
room temperature and vacuum filtered. A liquid having a slight ha~e is
obtained havlng a viscosity of 293 cs. at 25C and an SH content of .44
- percent.
EXAMPLE 3 ~ ~
- To a reaction vessel containing 200 parts of the thiofunctional
polysiloxane copolymer prepared in accordance with (B) above, are added
- 200 parts of a trimethylsiloxy-terminated dimethylpolysiloxane having a
viscosity of 60,000 cs. at 25C, 50 parts of hexamethyldisiloxane and 8
parts of acid clay (FILTROL No. 13) and heated to 155C for six hours. The
contents of the vessel are cooled to room temperature and vacuum filtered.
A clear, colorless liquid product is obtaiDed having a viscosity of 400 cs.
at 25C and an SH content of 0.39 percent. Nuclear Magnetic Resonance
analysis of the product shows a ratio of CH2S:Si(CH3)2 of 1.98.
COMPARISON EXAMPLE V
- A blend is prepared by mixing 100 parts of the thiofunctional
polysiloxane copolymer prepared in (B) above with 100 parts of a trimethyl-
siloxy-terminated dimethylpolysiloxane fluid having a viscosity of 60,000
cs. at 25C and 25 parts of hexamethyldisiloxane. The resultant product
has a viscosity of 2,354 cs. at 25C.
EXAMPLE 4
The procedure of Example 3, is repeated except the hexamethyl-
disiloxane is omitted. The resultant product has a viscosity of 5,681 cs.
at 25C and an SH content of 0.21 percent. Nuclear Magnetic Resonance
-- lS --
l~LZ7~
.
analysis of the product shows a ratlo of CH2S:Si(CU3)2 of 1:83.3.
COMPARISON EXAMPLE Vl
A blend is prepared in accordance with the procedure described
in Comparison Example V, except that the hexamethyldisiloxane is omitted.
The result product has a viscosity of 6,488 cs. at 25C.
EXAMPLE 5
- The procedure of Example 3 is repeated except that a trimethyl-
siloxy-terminated dimethylpolysiloxane having a viscosity of 20 cs. at 25C
is substituted for the trimethylsiloxy terminated diorganopolysiloxane hav-
ing a viscosity of 609000 cs. at 25C. A clear, colorless product is ob-
tained having a viscosity of 33.4 cs. at 25C and an SH content of 0.436
percent. Nuclear Magnetic Resonance analysis of the product shows a ratio
of CH2S si(CH3)2 of 1 104-2-
C0MPARISON EXAMPLE V2
A blend is prepared in accordance with Comparison Example Vl, ex-
cept that a trimethylsiloxy--terminated dimethylpolysiloxane having a viscosi-
ty of 20 cs. at 25C is substituted for the trimethylsiloxy-terminated
diorganopolysiloxane having a vlscosity of 60,000 cs. at 25C. The result
product has a viscosity of 46 cs. at 25C.
EXAMPLE 6
.
To a reaction vessel containing 45 parts of the ~hiofunctional
polysiloxane copolymer prepared in accordance with (A) above, are added
250 parts of octamethylcyclotetrasiloxane and 6 parts of acid clay (FILTROL
No. 13) and heated to 145C for six hours. The product is cooled, filtered
and the volatiles removed at a temperature of 185C at less than 1 torr.
The resultant product is a colorless, ha y fluid having a viscosity of 90
cs. at 25C and an SH content of 0.94 percent.
~127~
,
` COMPARISON EXAMPLE V3
~ . ' - .
To a reaction vessel containing 415.5 parts of octamethylcyclo-
tetrasiloxane are added 37.5 parts of toluene, 28.5 parts of 2-mercapto-
propyltrimethoxysilane, 21 parts of water, 15 parts of hexamethyldisiloxane
and 9 parts of acid clay (FILTROL No. 13) and heated to reflux temperature.
.. _ .. _ . .., .. _ . .
~ The water and methanol are azetroped off and collected in a dean stark
head. The contents are refluxed three days and after each day a sample is
withdrawn, filtered and the volatiles removed. After three days, the con-
tents of the reaction vessel are still volatile and the viscosity remains
fairly constant indicating that no equilibration has occorred.
; Comparison Example V3 shows that a cyclic siloxane having at
least four silicon atoms in the molecule will not equilibrate with a
thiofunctional silane; however, Example (6) shows that the same cyclic
siloxane will equilibrate with a thiofunctional copolymer.
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