Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to a liquid composition and
in paxticulax to a liquid composition comprising a metal
. compound a~d an orga~ic silicon compound suitable for
the preparation of shaped bodies especially fibres, . -~
: S coatings 9 foams and binders comprising a metal oxide and
silica,
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Composi~ions comprising precursors or metal oxide
and inorganic precursors of silica, for exam~le hydrated
silica sols, are knOWn9 and have served to produce metal
oxide solids 9 notably alumina and zirconia, contai~ing
dispersed silica. It is also known that dispersed silica
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has an e~ect on the phase change properties o alumina.
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With known pxocesses ~or incorporating silica into alumina,
a signi~icant e~fect on the stabilisation of transitional
alumina phases is not achieved a~ high tempera*ures,
Suppression of the appearance of the alpha form of alumina
at 1400C can be achieve~ only by adding suf~icient silica
so that the major phase present is crystalline alumino-
silicate (mullite). We have now iound that surprisingly
metal oxide solids con~aining dispersed silica may be
produced ~rom composi~ions comprising precursors of metal
oxides and organic silicon compounds. The sta~ilisation
of alumina phases for example can thereby be ef~ected a~
tempexatures at which stabilisation was prevlously.~otpOE~e
Furthermore stabilisation at low~r temperatures can be
achieved with lowec proportions of silica than hîtherto
possible.
According to the present invention there is provided
a liquid composition comprising an aqueous solution of a ~ .
water~soluble metal compound decomposable or rea~table to
pxoduce a metal oxide and of a water-soluble organic silicon
20 compound which is hydxolytically stable in the liquid . :.
composition and in which the silicon atoms are at-tached to
carbon ~toms directly or through an oxygen atom whe:cein
the concentration of the metal compound expressed as ~ .
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equivalent metal oxide exceeds the concentration of the.
25 silicon compound expressed as silicon dioxide. :.
I By solution is meant a txue solution or a colloidal
~ solution~
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Compositions according to the invention are capableof being converted, for example by heating to solids
comprising one or more metal oxides and silica which are
suitable for use in the form of foams, binders, ~oatings,
gIanules, cenospheres, films and espec~ally fibres.
The relative concentrations of metal compound and
organic silicon compound may be varied over wide limits,
for example from l~o by weight of silicon.compound to 94%
by weight of metal compound. Preferably the weight ratio ~
10 of the equivalent metal o~ide to the equivalent SiO2 is ::
at least 85:15.
The metal of the metal compound may be selected f.rom .~ ~ .
the elements of the Periodic Table having an atomic number
of 4, 12, 13, 20 to 32, 38 to 429 44 to 51, 56 to 60, 62
15 tv 83, 90, 92 ox 94. The metals Al, Fe~ Zr, Ti, Be~ Cr,
Mg7 Th~ U, Y, Ni, V, Mg9 M~, W and Co or mixtures *hereof
are pxeferred; the metals Al, Fe, Zr~ Ti and Th and more
particularly Al are especially preferred for fibres made
from the compositions~
The anionic constituent of the metal compound may
also be sele~ted from a wide range~ Two or more compounds
of the same or different metals may be used~ if desired~ :
Simple inorganic compounds including the hydroxides; the
halides and oxyhalides, especia~ly chlorides and
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oxychlorides; carbonates; nitratesj phosphates; and
sulphates are useful. Salts of organic acids such as
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neutral or basic acetates, oxalates, propionates, orformates or organo-metallic compounds are also suitable.
Basic salts are preferred as they polymerise in sol~tionO
~specially preferred are metal compounds which can orm
a refractory oxide, especially aluminium oxychloride,
basic aluminium aceta*e~ basic aluminium formate, ~ :
~irconium oxychloride, basic zirconium acetate, basic
zixconium nitrate or basic zirconium formate~ mixtures
thereof or mixed salts thereof.
The metal compound is most conveniently decomposable
: to the metal oxide by heating, usually at a temperature : .
from 200C to 1000C, Carbidas of the metals may be .:
formed by including carbon or a carbonaceous matexial in
the composition which, on heating ~or example, reacts
with the metal compound or a reaction product thereo.
In an analogous fashion, nitrides can be formed by
.including nitrogen-containing compounds in the composition. ;~
Reaction to form carbides or nitrides may also be grought ~ -
about by the action of carbon- or nitxogen-containiny gases
on the metal oxide.
The water-solubility of the organic silicon compound
is preferably sufficiently high to provide a concentration
of at least 0.1% by weight expressed as SiO2 dissolved in
the liquid composition~ The wateI solubility may be
incxeased by the inclusion of a water~miscible organic
solvent, for e~ple an alcohol, in the liquid composition.
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The silicon compound is preferably a compound
containing a monomeric or polymeric siloxane, silanol
or silanolate group, and~or a water-solubilising carpon
functional group. By water-solubilising carbon
functional grGup is meant a group which is attached to
the compound through carbon and which confexs water~
solubility on an otherwise relatively insoluble compound.
Ex~mples of such groups are amine, amide, esterj alcohol~
ether and caxboxyl groups. More pxeferably the silicon
10 compound is selected from wa~ex-soluble polysiloxane-
polyoxyalkylene copolymers. Such copolymers may
conveniently be divided into those in which the po~ymer
blocks have,Si_C linkages and those in which the polymer
blocks have Si_O_C l~inkagesO Si-C linkages are preerred
lS as copolymers having such linkages axe more stable to
hydrolysis than those ha~iny Si-O_C linkages.
.The polysiloxane blocks used in the copolymers
preferably contains at least two siloxane gxoups of the
general type ~ SiO4 b whexe b is 1, 2 or 3~ ~specially
useful polysiloxane ~locks can contain~ ~or example~
chain terminating groups R3SiOo 5, main chain groups
_ 0 50Si(R2)o 5 - or chain branchi~g groups RSi(Oo 5)3
or combinations o such groups having the same ox
'~ dife~ent R substituents. It will be understood that the
00 5 units indicate that the oxyyen atom is shared wi~h a
neighbouxing Si atom. The polysiloxane block may be
linear, cyclic or cross_linked~ or it can have combinations
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of these structures, R may be any monovalent hydrocarbonxadical of which examples include alkyl radicals sueh as
methyl, ethyl~ propyl, butyl~ octyl and octadecyl,
cycloalkyl radicals such as cyclohexyl, aryl radicals
such as phenyl and tolyl and arylalkyl radicals such as
benzyl and phenylethyl radicals. Polymethylsiloxane
blocks are preferred as they can provide copolymers of
hiyhest water-.solubility. A m:Lnor proportion of Sî-H
groups may also be p~esent, The polysiloxane block
usually has an average molecular weight from 220 to
50~000; molecular weights of preferred blocks axe 220 ~ :
to 20000, more preferably 220 to 2000.
The polyoxyalkylene block used in the SloC linked
copolymer may be represented as
_ Rl ~ o(cm~l2mo)d R ]
in wh;ch the -Rl- linking group is attached directly to
a si~icon atom o~ the polysiloxane by one of its
valencies~ the other valencies (~ in numbe~) being
attached to ~ num~er of polyoxyalkylene groups of the
type
O(C~H2mO)d Rll. Typical divalent -Rl- groups include
1,3-propylene-(CH2)3-, 1,11-undecylene..(CH2)11-9
--(CH2)3~ CH2-CIHCH2-
: ~ CH3
25 ~CH2CH2-C~ Divalent _R1- groups
C2l~5 CH3
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containing C, H and 0 may also be used, for example
-CH2_cH2c(o) - ~ _(CH2)3c(O)--~ _(CH2)3CH2c(o)-j
2)3 ( 2)2C()~ -(CH2)1~0CH2C(o)_~ -(CH ) ~
O~CH2)2C(O)
Typical divalent -Rl- groups containing C 9 H, 0 and N
include -(CH2)3~HC(0)_,
C~H5 R
-(CH2)3Nl(0)~ -(CH2)3 lC(o)- where R = alkyl~ cycloalkyl
or hydroxyl~ ~HC(~)-
-(CH2)30C(O)NH ~ CH3 CH2-
Trivalent -Rl = groups may be used, including ~(CH2)3-CH~
CH2-
( l2)30CH2lH~CH2-~ -(CH2) OCH C -2~ H ~~~~
CH2-
f H 20C ( O ) ~H~NHC ~ O ) -
:, -(CH2)3 IH . Amongst useful
CH~oc(O)NH ~ _ N~C(O)-
tetravalent -R _ groups are
- / CH2 ~ C(0)-l
( 2)3 H2C j CH2- ' ~(CH2)3C~2C[CH2C()NH ~ ~3
H2- .
Xn the oxyalkylene ~oup (CmH2mO-)dR~ m~ is preexably
25 2~ 3 or 4; especially use~ul oxyalkylene groups are
oxyethylene, oxy-192-propylene~ oxy-1~3-pr~pylene and
oxy-194~butylene, the oxyethylene especially aiding
water solubility. The oxyalkylene groups may be the
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same or mi~tures of oxyalkylene groups may be used. The
value of ~d~ is pref erably chosen so that the molecular
weight of the (-CmH2mO)d_ block falls within the ranS2
120 to 9000. especially within the range 400 to 5000. :
The terminal group Rll of the polyoxyalkylene
chains can be varied widely. Alipha*ic and aromatic
groups free from olefinic unsaturation are preferred,
:fox example methyl 9 ethyl, isopropyï, n-butyl, i-bu*yl, : .
undecenyl, 2-ethylhexyl~ cycloalkyl groups including
c~clohexyl 9 phenyl ~ tolyl or naphthyl ~, Other terminal
groups R11 which may be used include acetyl~ propionyl,
butyryl, carbo~ate or substituted carbamyl groups such : :
as n-phenyl-carbamyl C6H5NHC(O) and n-ethyl carbamyl
', . C2H5NHC: ( O ), . .
~or copolymers having an Si-O_~ linkage between the
polymer blocks~ Rl in the polyoxyalkylene block is omitted.
The polyoxyalkylene groups ~O(CmH2mO)dR11 of the Si~O-C
linked copolymiexs are as hereinbeore described.
The oxyethylene content of the polyoxyalkylene is
~ 20 of impoLtance in controlling the water-solubility of
-. the copolymer. Preexably the average C:O ratio in
~e oxyalkylene chain (-CmH2mO)~ is below 3:1 to attain
su~ficient water solubility. We ~ind that about 30% by
we~t oxyethylene units together with oxypropylene units
is usually about the lower limit of oxyethylene which
will impart adequate water solubility to an oxyethylene/
ox~propy~ene polymer, or a copolymer of this with a : :
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siloxane; the C:O ~atio in the oxyallcylene chain in
such cases is about 2.6:1. More preerably~ there~ore9
suf~icient oxyethylene units should be pxesent in the
oxyalkylene block to provide a C:O xatio of at most
2.6:1~ The ratio of siloxane to polyoxyalkylene ln a
methyl siloxane copolymer is preferably less than 2.5:1
fox adequa*e water solubili~y.
Examples of water-so~uble Si~C linked copolymers
useful for the compositions o the invention are
described in United Kingdom Patent Specifications
Nos. 955,916; 1,015,611 and 1,133,273. Examples of
suitable water-soluble Si_0-C linked copol~mers are ~ -
descxibed in United Kingdom Pate~t Speciication
No. 954,041,
It is also preferxed that the silicon compound be
compatible with the other compounds of the liquid
composition~ especially in not precipitating a gc-!l or
a soli~ therefrom. Thus, silicon compounds which axe
: strongly alkaline in water solution are less satisfactoxy
~0 than those which produce a neutral or acidic reaction in
water.
The compositions ~re pre~erably used at a temperature
such that the cloud point of the silicon compound is not
exceeded in the liquid.
Other silicon compounds which may be used in the
compositions inc~ude water-soluble alkoxy silanes,
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quaternary and other water-soluble nitrogen~containing
silanes and siloxanes. ~lkali metal siliconates are
generally sufficiently water-soluble to be use~ul, for
example CH3Si(OH)(ONa)2 or CH3Si(OH)2(ONa). Howeve~,
such compounds give strongly alkaline solutions and are
less favoured for reasons described hereina~ter~
Since the compositions are usually heated in order
to foxm solid products, the silicon compound is
decomposable to ~orm silica. It is thexeo~e pre~erred
that the silicon compound should yield the maxim~m silica
on decomposition~ consis*ent with its other requirements.
Suitably, silica yields may vary ~rom 5% to 65% by weight
of the silicon compound~ Polysiloxanes solubilised by
amine functional groups, for example _(CH2)3-N(CH3~,
can yield above 65%, for example 65% to 75%, by weight
of silic~.
Add~tional components such as pigments, polymers,
colourants~ surfactants~ viscosity control additives,
or sources o~ other oxides, ~ay ~e incl~ded in the
compositions, but since the purpose of the additional
component is related generally to uses o~ the composition,
these are descxibed in more detail hereinafter.
~ he compositions may conveniently be prepared by
dissolving the metal compound, t}le silicon compound and
any other soluble components in water in any convenient
orde~, For some em~odiments it is necessary to provide
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some heat to assist dissolution. The compounds may be
formed rom suitable prec~sors 9 usually i~ the presence
of the water solvent, ~or most uses of the composi~ions
the concentrations of the majox components 9 for exa~pIe
the metal compound, range from very dil~lte to satuxation9
; e,g. in the range 10% to 80% by weight of composition.
The concentra*ion o~ dissolved organic silicon compound
in the composition is preferably at least O~l~o by weight
expressed as silicon dioxide~
The composition is p~epared at any viscosity
suitable for the use to which the composition is puto
Viscositie~ of greater than G.1 poise, for example from
0~1 poise to 5000 poise~ are generally convenient for
use as ~inders and for the formation of shaped bodies.
Viscosity control additives~ for example wa~er-soluble
polymers 9 are useful in producing the desired v.iscosity.
It is also possible to use a polymeric metal
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compound, for example basic aluminium or zirconium salts,
to increase the viscosity of the compositions~
Especially in the casa o~ compositions containin~ :
metal compounds wh.ich tend to gel in alkaline conditions
it is pre~erred to maintain a neutral or acid reaction
in the com~osition.
Especially for use o~ the compositions for making
~5 fibres as hereinafter described, a water~soluble silicon_ -
free organic polymer is a much preferxed additional :~
component of the compositions.
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The or~anic polymer is preer~bly ~ non-ionic
water~soluble organic polymer; a polyhydro~ylated organic
polymer or a natuxal water-sol~ble gum. The organic
polymer is preferably the~mally stable under the
conditions of fibrising~ fox example ~xom ~mbient
temperature to within several degrees o~ the boiling
point of water. Examples of preferred organic polymers
include:
partially hydrolysed polyvinyl acetate ~polyvinyl alcohol)~
polyacrylamide and partially hydrolysed polyacrylamide,
polyacrylic acids,
polyethylene oxides5
carboxyalkyl celluloses, for exam~le carboxymethyl cellulose~
hydro~yalkyl celluloses, or example hydroxymethyl cellulose,
alkyl celluloses~ for example methyl cellulose, .- .
: hydrolysed starches,
dex*rans, . .:
guar gum, .
polyvinyl pyrrolido~es J
polyethylene ~lycols,
alginic acids,
polyisobutylene derivatives~
polyurethanes~ and
esters, copolymers or mixtuxes thereof~
Most preferred organic polymers are straight~chain
polyhydroxyl~ted organic polymers, for example polyvinyl
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alcohol, partially hydxolysed polyvinyl acetate,
polyethylene oxide or polyethylene glycol.
Conveniently the molecular weight of the organic
polymer is in the range 103 to 107, preferably as high
a molecular weight as is consistent with the ability of
the organic polymer to dissolve in the solvent used in
the process o the invention. For example, it is
preerred or the polyvinyl alcohol or partially
hydrolysed polyvinyl acetate t~ have a medium or high
molecular weight, the polyethylene oxide to have a
molecular weight of 104 to 1o6 and the polymers dexived
from cellu~ose to have a molecular weight of 10000 to
50000 0 :
It is preferred that the ccncentxation of organic
polymer in a composition used for ~ormin~ ibres be from
0.1% to 10% by weight, more preferably from 0.1% to 2%
by weight.
We prefer that little or no che~ical reaction should
occur between the metal compound and the oxganic polymer
,, in the fibrising composition~
The especial property o the liquid compositions
which makes them useful for many technical purposes is
their ability to be converted to a solid composition in
which the metal and silicon compounds remain as an
intimate mixture. Many such mix*ures are reractory
and hard and suitable for many applications especially
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those requiring a resistance to high temperature~
Decomposition or reaction of the met~l ~nd silicon
compounds to their oxides is usually preceded by at
least partial drying o the composition~ Conversion tc-
a solid is conveniently effected by hea~ing, preferably~t 200C t~ 1000C.
Conversion of the liquid composition may be
advantageously carried out, especially fox compositions
comprising al~minium compounds, by subjecting the dry or
paxtially dry composition to hydrothermal treatment,
that is, to the simultaneous action of heat and water
vapour~ Treatment with steam at 250C to 500C is
preerred.
In embodlments where a solid composition is pxoduced
from a liquid composition comprising a me*al compound
having an acid anion, ~or example aluminium o~chloride, ~:
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it is especially advantageous to subject the solid to
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the action o a basic substance~ for example ammonia or
a volatile amine, before, or simul~aneously with
hydrothexmal treatment.
The solid composition may be fuxther heate~ to
change the crystalline ~orm o~ the oxide phases present ~ :
or to sinter the composition, prefexably at 1000C to
2000C.
A composition according to the invention may be
used to coat substratess D fox example glasses, metals,
etal oxides cr cer~mlcs by applying it to the substrate
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and subsequently converting it to form an insoluble
coating. The substrate may take a variety of shapes,
e~g. fibre, filament, film, ~ranule or powder. Any
convenient method, e.g. dip-coating, spraying, roller-
or brush_coatin~, may be used to apply the coating tothe substrate The coating is dried, at least partly,
and preferably heated~ for e~amp~e to a ~emperature
from 200C to 1000C to decompose the metal compound
and the silicon compound.
The compositions may also be used as a binder or
adhesive for a wide variety of materials, especially
ceramic or refractory granules and ~ibres~
; The compositions according to the invention are
especially useful for the preparation of shaped bodies, ~ ;
for example cenospheres, films, porous structures and
especially fibres, by forming the composition into the
desired shape and convexting the composition to a solid~
Shaped bodies o~ thin section are preferred9 as the
release of volatile materials on decomposition or
reaction of the composition is thereby facilitated, and
is less likely to lead to cracking ~ailure of the body
Any convenient method ox forming the composition
into the desired shape may be employed; for cenosphexes,
spray-drying or prilling processes are suitable; for
fi~ms, extrusion or casting techniques are convenient;
for porous structures, a suitable ~oaming process or
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honeycomb formation technique may be used; for fibres~
any convenient method of ibrisin~ may be used, for
~xampl~ centriugal spinning, drawing~ blowin~, t~cXr
spinning, extrusion through a spinneret or suitable
combinations thereof. A relic process in which the
composi~ion is used to impxegnatP an organic fibxe~ may
also be used. ~ibrising by blowing is effected as
hereinafter described.
The viscosity of the composition used to form fibres
is preferably one suited to the fibrising method employed.
Conveniently the viscosity i5 in the ra~ge 0.1 *o 3000
poise, preferably 100 to 1000 poise when fibrising is
effected by extrusion o~ the co~position through a
spinneret to form a continuous ~ilament. ~ibrising of
compositions of low viscosity, for example 0.1 to 100
poise, is preferably carried ou* by a blowing process
as hereinafter described~
It is preferred to ~emove solvent rom the formed
body by evaporation9 for example by heating at a
temperature from 30C to 110C, optionally under reduced
pressure.
The shaped body may be further heated to a
temperatuxe greater tha~ that of a drying treatment in
order subsequently to complete decomposition of the me-tal
or silicon compound, to change the crystalline form of
metal oxide phases formed or to sinter the body~ Thus the
body may be heated at 1000C to 2000C, preferably at
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lo~PC to ~Q~, usually for a period from one minute to
one hour. Heating may be carried out in stages, for
example in successive steps o increasing te~perature.
Heating in the presence of air or oxygen may be desirable
to oxidise any organic ma~erial pxesent in the bodyO
Various additives may be included in the shaped body5
singly or in combination 9 conven~ently by adding them to
the composition from which ~he shaped body is formed~
Additives may also be included on the surface of the body
by any suitable trea*ment process. Examples of additives
which may be included are:
(a) alkaline earth compounds, for example compounds o~
magnesium or calcium, decomposable to alkaline eaxth
oxides;
(b) acid oxides, especially B203, P205 or ZxO2 or
compounds which decompose to form acid oxîdes;
(c) catalyst materials, for example Pt7 Sb, Cu9 Al,
Pd9 Ag; Ru, Bi, Zn9 Ni, Co, Cr, Ti9 ~e, V or Mn
in elemental form or compou~d orm;
(d3 fluorides, for example H~, Na~ or Ca~2;
(e) alkali metal compounds, fox example compounds of
lithium, sodium or potassium,
(f) xeinforcing particles or fillexs such as colloidal
silica;
~ 25 (g) colouxing agents~ .~or example mordant dyes or pigments;
; (h) rare earth oxides or yttria or precursors thereofO
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The catalyst material may be present on the surface
of the shaped body-or it may be included within the body.
In some embodiments 7 the catalyst material may be p ~tly
within the body and par~ly on its surface. o~e ~r more
catalyst materials may be pxesent.
When a-t leas~ part of the catalyst material ~s
included in the body7 it is convenient to disperse or
dissolve ~he catalys~ material~ or a precursor therefor 9
in the composition fxom which the shaped body is foxmed.
By precu~sor is meant a material which when suitably
txeated, ~or example by hea*ing or reduction, will
ge~esate ~ catalyst material, directly ox indirectly.
Shaped bodies, especially fibxes comprising a catalyst
matexial may be used in a wide variety o~ catalytic
~: 15 processes as hereinafter described~
The preerred shaped body is a fibre, conveniently
made by fibrising the liquid composition ol10wed by
decompositiQn. ~ibrisi~g by extrusion thxough a
spinneret ~s especially useul in producing continuous
fibre~ ~ibrising is most conveniently carried out at
the ambient temperatuxe~ but i~ desixed it may be carried
out at any other tempexature at which the fibrising
composition is stable. ~ox ex~mple, it may be convenient
in some embodiments to vary the temperature in order to
2S produce the viscosity of the composition appxopriate for
fibxising~
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Fibrisi.ng by blowillg compri ses ext:ruding the
~ibrising composition through one or more apertures
into at least one gas stream having a component o~
high velocity in ~he direction of travel o~ the e~tr~ed
~omposition. The extruded composition is drawn down by
the actiOn o the gas stream on it. The dimensions of
the aperture through which the fibrising co~position is
extruded may vary widely. We prefex to use an aperture
having at least one dimension larger then SO microns
and smaller than 500 microns. The aperture may have a
vaxiety of shapes, Ior example we have used circular,
triangular and star~shaped apertures. It is convenient
in some embodiments to extrude the ~ibrising composition
~hrough a slitg which may be substantially straight or
curved, for example in the case of an annular sli~. A
plu~ality o~ apertures may be used in one ex*rusion head.
The material in which the ~pertuxe is formed may be chosen
from a wide vaxiety of substances. A metalS for example
stainless steel or monel, îs especially use~uln Owing to
the fact -that the fibrising composition may be at or near
ambient temperature during extrusion and that two low
extrusion pressures are used, it is convenient,
especially fxom the point of view of ~heapness~ to use a
plastics material in which to form the aperture; suitable
plastics materials include polystyrene, polypropylene,
polyvinyl chloride and polytetrafluoroethylene.
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- It is prefe~red to use two gas streams which converge
at or near the point where the fibrising composition is
extruded from the aperture; preferably the angle be*ween
the converging gas streams is fxom 30 to 60~ In
S pxeferred embodiments~ gas streams emexge from slots on
each side of a xow of aper*uxes or a sli$, or a
conically-shaped gas stxe~m emerges from an annular slot
arranged substantially concentrically around an annular
extrusion slit. The velocity of the gas stream may be
varied over a wide range; we prefer to use velocities
in the region of 40 to 1500 ft per second~ Air is the
pxefexred gas, most conveniently air at ambient
temperature,
Control of the rate of water removal from the
extruded composition may be e~ected by the degxee of
saturation of the gas stream. Conveniently the gas may
: be mixed with water vapour in the gas reservo:~x, but as ,.
expansion of the gas from its reservoir may tend to altex ~:
*he degree of saturation, it is sometimes useful to add
water-vapour ater expansion. Air at a relati~e humidity
o~ greater than 80% is especially usefulJ ~;
The distance separating the point o~ emergence o~
the gas stream from the extrusion aperture should be as
small as possible; we prefer that the distance between
the closest edges of the apexture and the air slot be
less than 0.-5 mm.
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The pressure employed to extrude the fib~ising
- composition will depend on the viscosity of the
composition, the size and shape of the aperture and the
desired xate o~ extrusion. We find that pressures from
16 to 120 lb per square inch absoluteare convenient for
compositions having viscosities up to about 100 poise~
The f~bre ~ay be dried fur~hPr a~er at-tenuation in
the gas stxeam i~ required. .rhe ibxe may then be
subjected to hydxothermal and/or ammonia treatment as
hereinbefore described9 if desired. The fibre may also
optionally be subjected to furth~r processing which may
be requiredg for example it may be heated to complete
the decomposition of the metal compound to the oxide and :
to decompose the organic materials in the fibrising
composition, to change the crystalline Xoxm of oxide
phases present or to sinter the fibre~ Typically, the ~ :
ibre may be heated at a tempexature from 500C to 1200C
: or a period of from one minute to one hour, preferably ::;
500C to 800C for one minute to one hour. . :
Various additives as hereinbefore described may be
included in ox on the surace of *he fibre, singly or in
any combination, conveniently by adding them to the
fibrising composition or by including them on the surface
of the fibxe by any sui*able treatment process. ~-
~hus the fibxes may be coated with a size, such as ~:
polyvinyl alcohol or stearic acid. They may be immersed
', ' ',":' ~''
';
'.
. ~.
,:
!, . . ~: , . . , , ~ . ,
~7Z69g
23.
in a solutio~ o~ ethyl silicate9 washed and heated to ~ive
a fibre'containin~ extra ~lic~- They may also be soaked
in solutions of metal compounds, for example m~gnesium
ethoxide in methanol~ and the treated fibres heated to
give a fibre containing additional refractory metal
oxide. The ~ibres may be given a silicone tLeatment
~or example by applying a chlorosilane (in vapour ox
solution form) to the fibre sur~aceO
Especially conveniently a catalyst material may be
~; 10 dispersed in the fibrising composi*ion by dissolv;ng it 9 ~'
or its precursor, in the said composition. In pre~erred
embodimen*s of the invention water-soluble materials,
for example salts o catalytic metals9 especially metal
nitrates, axe dissolved in the aqueous ~ibxising
1$ compositions~
Dispexsion of the catalyst matexial in the fibrising
composition may also conveniently be carried vut by mixing .
lnsolublP ox paxtly soluble particulate catalyst material
with the fibrising com~osition. Pre~erably the mean si2e
o particles thus dispexsed should be smaller than the mean
diameter of the fibx~i pxoduced~ and moxe particular~y
particles should be of colloidal size.
Any deslxed qu~ntity of catalyst material may be
dispersed in the i.brising composition provided that the
fibre formed is still suficiently strong and cohexent
for use ao a librous catalyst, We ii~d that up to about
~';
., ~
: . .
1~726~39
2~.
10% o~ a catalyst material may be incorporated in the
fibre without serious deterioration in fibre properties.
It is pre~erred that the catalyst material be
rhemically compatible w~th the constituents of the
`~ 5 fibrising composition. When the fibre is heated as
herein dexcribed, it is preerable for the catalyst
material to be stable at the tempexature o~ heating.
In the case of a catalys-~ material precursor~ it is
frequently convenient for the catalyst to be formed
from the said precursor during hea~ing of the fibre.
The catalyst material m~y be incorporated into
the fibre by soaking the said ~ibre in a solution of ~`
the catalyst material or a catalyst material precursor
in a suitable solvent and subsequen*ly removing the said ~ -
solvent from the fibre. Water is a suitable solvent for ~-
many catalyst materials or their precurs, for example
metal salts, A fibre may be soaked befoxe or after it
is heated to ~orm a fibre of dif~erent composition as
hexein described~
The catalyst material may conveniently be deposited
in a suitable form on at leas-t part o~ the ~ibre sur~ace~
~or ~his purpose it may, i~ desired9 be bonded to the
said sur~ace by means of a binding agent, w~kh may itself
be a catalyst material, for example aluminium phosphate.
2S Bonding may also be effec*ed by means of an application
of a composition according to the invention to the said
, '~ .:',
~'
~L~7Z6~
25.
surface or to the catal~st material or bo*h, and removal
of the solven-t of the said composition.
In embodiments in which no binder is used to as~sist '.
adherence of the catalyst material to the fibre surface~
it is often possible to bxing about some chemical
intexaction between the catalys~ and the fibre to improve .'
bonding. In most embodiments of the invention, however,
it is satîsfactory merely to deposit the catalyst material
on the fibre surface in a form sufficiently fine that the
normal forces o~ physical attraction take effect. Thus
it is convenient to deposit the catalyst material from a
mist or vapour comprising the catalyst material or its
precursor. Most con~eniently the catalyst matexial or
its precursor is deposited on the fibre surface by
treating the.said surface with a dispersion comprisi~g
the catalyst matexial or its pxecursox and a suitable
liquid~ A solution o the catalyst material or its
~' precursor in a volatile solvent is especially useful.
In cases where the catalyst material is dispersed in a :
~iquid which does not dissolve it, it is pre~erred that
the catalyst material,be in a finely-divided form, most
preferably having a mean si~e less than 0.5 micron!
The fibre comprising a catalyst material may be
further treated, or example *o bring about desixed
changes in the catalyst material. Fox example 9 in cases
where a catalyst material precuxsor has been incorporated
in or on~the fibxe, it will be necessary to genexate the
.
.' .
.~
, . . . .
,: :
~72~9~
26.
active catalyst material by a s~itable process. The
processe~ normally used include chemical reaction to
form a different compound, reduction and heating. ~ome
o these processes, especial~ heating, may be combined
with hydrothexmal treatment or heating the fibre to
decompose the metal compound or the organic material of
the ibrising composition. Treatment o~ the fibxe to
achieve desirable physical changes in the catalyst
matexial may also be carried out; for exampl~, changes
in the surface area or crystal structure may be desirable
to achieve specific catalytic effects. Trea$ment o~ the
fibre to eliminate undesirable substances~ for example
catalyst poisons, may be useful in some embodiments.
The compositions of the invention are especially
useful or the preparation of coatings, binders and
shaped bodies, especially fibres, compxising zirconia
or alumina and silica. Thus compositions comprising an
aluminium compound decomposable to alumina, especially
aluminium oxychloride~ basic aluminium acetate ox basic
al~minium formate, and a water-soluble organic silicon
compound as herein described may be clecomposed by heating
to form solid compositions compxising alumina and silica
in which the alumina is substantially in one or more of
its transitional phase orms at temperatures up $o 1400~C~
~5 Alumina is transformed from its transitional phase
forms (eta, gamma, delta and theta) to its alpha form on
~ .
' ~ - - .
~7Z699
,
27.
heati~g at 1200C for a shoxt ~ime (~Alumina as a
Ceramic Material~ Fdited by W.H. Gitzen, The American
Ce~amic Society~ 1970)o
While not wishing ~o be restricted to any partI~ular
theor~, we believe *ha~ it is likely that the addition of
silica to tlle alumina by *he use of a water-soluble :
silicon compound in the composition o the invention
gives a homogeneous dispersion o the silica in the alumina
and thereby produ~es a very considerable reduction of the
rate of trans~oxmation o low temperature phases to high
temperatu~e phases and in particular of transitional
aluminas to alpha_alumina on heatingO T.hus shaped bodi.es
comprising alumina prepared according to the invention
will exhibit improved thermal stability.
15The invention thus provides a solid composi-tion,
ox example a fibxe, comprising al~mina and silica
wherein the ratio by weight of alumina to silica is f~om
85:15 to 98:2 i~ which the crystalline alumina is
substantially in one or more of its txansitional foxms
when the composition is heated at 1200C for at least
~` one hour 9 pre~erably for at least ten hoursO I~ such
compositions ~he crystalline alumina is therefo~e
substantially free fxom the alpha phase.
The invention also provides solid compositions
compxising alumina ~nd silica which, when heated to
1400~C or one inute~ two minutes os ive ~i~utes are
,
,~ .
.:. '' '
1C~72~i99
28~
substantially free from alpha_alumina and the mu~lite
phase o:f ~luminosilicate
The invention further provides solid compositions
comprising alumina and silica which, when heated to
1300aC for five minutes, thirty minutes or two hours,
are substantially ~ree from alpha-alumina and the mullite
phase o aluminosilicate~
. The inventio~ further provides solid compositions
comprising alumlna ~o silica which~ when heated to 1200C
or ten minutes or one hundred hours, are substantially
free ~rom alpha_alumina and the mullite phase of alumino-
. si}icateO
The i~vention ~urther provides so~id co~positions
compxising alumina and silica which~ when heated to 1100C
fox one hour, ten hours or one hundred hours, is
substantially free from alpha_alumina and the mullite
phase of alum~nosilicate.
Solid compositions comprising alumina and silica
when h~ated to the temperatures and for the times
: 20 described are substantial~y in one or more of the
~ transitional alumina forms.
: Thus solid compositions comprising alumina and silica
whexein the ratio by wei~ht of alumina to silicon is from
85:15 to 98:2 may be obtained in which the crystalline
alumina is substantially in the delta or theta phase when
the composition is heated at 1200C for at least one hour,
preferably for te~ ho~rs.
~'
:
: ., . : .. .
:.: .. .. .: .... . ..... . . ...
107Z6~
29,
~ urther~ such solid compositions, apart from those
in which theta is the major phase~ when he~ted to the
temperatures and or the times described, show no X_ray
crystallographic evidence for the existence of
s crystalline silica or aluminosilica*e (m~llite).
The introduction of silica in~o fibres comprising
metal oxides by the processes of the invention have the
further advantaye that the homogeneity of the ~ibrising
composition avoids the problems associated with the use
of particulate silica, for example as colloidal particles.
~ch pxoblems include (1) the need to limit ~ibre diameter
due to interference to required 10w characteristics for
fibrising by the presence o~ particles; t2) bhe necessity
to avoid otherwise desirable polymeric organic fibrising
aids whioh tend to flocculate sols; and (3) the presence
in the finished fibre of regions o~ high silica content
which are liable to crystalli.se to a silicate phase.
The invention thus provides a fibre comp~ising silica
and alumina and/or other metal oxide, especially zirconia~
p~efexably wherein the ratio by weight of metal c,xide and
silica is 85:15 to 98:2, preerably from 90:10 to 9~:3
which may be in continuous or discontinuous ~èngths,
although discontin~ous ~ibres may have very high ratios
of length to diameter, for example greater than 5000
~ibres can be made with average diameters less than
20 microns, typically rrom 0~5 to 5nO microns. As a result
- ,.
.'-~
'
'" ' :.'
~1~72~9~
30.
of the avoidance of formation v undesirable crystal
forms of alumina as hereinbefore reerred to9 alumina
fibres show remarkable resistance to physical change
at high temperature~ for example from 1000C to ~00C.
In general~ the fibres heated at 500C to 800C have a
very high sur~ace area, a BET surface axea of more than
50 m /g being consistently observed5 and figures of
2 2
50 m /9 to 200 m /g being the usual measured range after
hydrothermal ~reatmen~ and af~er one hour of heating at
500C to 800C. The presence of silica introd~ced by
the processes of the invention increases the thermal and
hydrothermal sta~ility with ~espect to suxface area of
a~ alumina fibre~ and hence certain catalytic properties.
The acidity of the alumina conferred by the silica conten~
' 15 provides impsoved ion exchange properties of the solid
composition. The fibxes may be collected as individual
~ibres or they may be collected in the orm of a yarn~
mat or felt~ Mats or felts are conveniently formed by
collecting the fibres on a moving bandg prefe~ably a band
of foxaminous material, for example steel mesh~ The ~ibxes
may be collected on a mould to provide a shaped elt. I
desired the ibres may be bonded together, for example by
collecting the fibses before they are dry and heating the
resultant mat or felt. Bonding may also be effected by
the use of a binding agent. The mat or felt may be
compressed, i~ desired, for example to incxease its density.
.
" ' .
' ~.
~'
' ' '.,
:
. .
~7~
The invention is especially useful in preparing glassy
fibresO F`ibres spun int~ yarn may b~ made up as cloth.
~ ibrous catalys~s according to the invention
comprising the metals copper, ruthenium, nickel, palladium7
S platinum ox silvexg compounds or combinations thereo~ are
especially use~ul in processes such as the following:
dehydration of al~ohols~
meth~nol synthesis~
: reduction of nitrobenzene,
~0 ammonia decomposition~
steam re~orming o~ naphtha or natural gas~
hydrogenation of oleins, aromatics, nitrides, ats and oils,
sulphur dioxide oxidation~
hydroalkylation,
; 15 methane ammoxidation~
ethylene oxide ~rom ethylene,
~oxmaldehyde from methanol.
Semiconductor oxides are useful catalyst materials.
For example, Cr203~"eta" alumina may be used for para~fin
dehydrogenation ox naphtha xeforming.
Metallic halides, ~or example CuCl2, Sb~13, ~lCl3 or
CrC13, provide fibrous catalysts which are useful or a
vaxiety of ohlorination and oxychlorination reactions or
isomerisation o parains, oleins and aromatics.
Oxgano.metallic catalysts may be best employed in
the invention by soaking or coating of the preorred
.- : .
~7~6g9
3~. :
fibre. The fibrous catalysts are useful in producing
: ethylene oligomers, polyethylenes and polyesters~ Metal
carbonyls~ fox exa~ple HCo(CO)4~ provide fibrous
catalysts suitable for carrying out 0~0 processes.
S The fibrous catalysts~ especially ~hose containing
platinum, palladium, molybdenum~ Co30~5 V205, Cr203~
MnO2, ~e203 or NiO, or combinations thereof, may be used
in a car e~haust ~reatmen~ device, for example to ca~alyse
the oxidation of car exhaust gases~ for example in an
afterburner.
Other catalytic materials found useful include:
cobalt molybda~e,
nickel molybdate,
bismuth molyb~ate,
copper molybdate,
2inc chromite,
cobalt oxide, Co3040
~ibrous catalysts according to the invention are
advantageous owing to their high external sur~ace areas;
they are heat-xesistant and mechanically strong. :
: The invention is thus use~ul in producing shaped
bodies comprising metal oxides,especially ibres and
.
~ore especially alunina fib~es which may be of very small :
diameter, dense, white, strong and of high modulus for
example 20 x 1o6 to 3S x ~o6 pounds p~ squar~ inch
Young~s modulus in ~hc case of alurina fibres. The ~;
:~:
. ~':
`
~L~7Z6~9
bodies, especially the fibxes, may conveniently be used,
for example as high temperature insulatirlg matexials~
fillers, as reinforcement for resins, me~als and cerdmic
materials, inext filters~ catalysts or catalyst supports~
The invention is illus~rated, but not limi*ed, by
the following ExamplesO. All X-ray difrac~ion resul~s
quoted in the Examples were obtained using a Philips
di~ractometex, ~ncident Copper radiation and a graphite
monochromator in the diffracted beam to select the K ~y
wavelengthO Apparent crystallite sizes of eta alumina
were derived from the measured full width at half height
of the diffxaction maxima at 67 2 e after instrumental
broadeni~g had been removed by fouriQr deconvolution,
(an apparent crystallite si~e of 60 A is derived rom a
peak at 67 2 e having a deconvolu~ed ~ull width at half ~ :
height o~ 1.76 2 ~). Phase identiication is based on
the results of J W Newsome, H W Heiser, A S Russell, :
H C Stumf~ Technical Paper No.10, second revision,
AIumina Proper~ies~ Alumînium Company of ~mexica~
Pittsburg, Pennsylvania 9 1960.
Xn the ~ollowing Examples reference is made to
various silicon compounds. Details of these are shown
in the ollowing tables~ with the corresponding xeference
used in the Examples.
,. -:
:
.
~7Z6~9
34.
.Table 1
O ~
O ~
) ~ ~ it~
h ~: . . . .. - .
O ~ ~ C`~ O I
t) ~ .. . .. .. -
rl ~ ~ ~
U~ ~1
P~ . .
O O O ' O O O
O O O O O O O
~ O ~
1~
.
. .
X~
. ~ C~,
"; ~ ',
O ' i~ 0~,",0 ~ ~ ~'
~1 ~ ~ (Ji
~1 ~ a~ ~
(I) C~ l t` '.
~ ,) ' to~ X ~ .
)
~ I t/) --' lJ~ -- O) `-- Q) I
rl O O O ~ O ~ O
~0 ~ C~ ~ '.
. ~ Z ~ ~ O Z O Z O _~ :
~ C a~ .
-- ~ a) X
~ ~ 1 $ ~: $ ~ $ r~ V . .
-- O --' O ~ ~ -- U) -- ~ ~H .,
~ C~ ` Q `.
1~ .'
~ If) Il') ~ ~ _~ .. . .
_ ~ _ ~ ~ 0~ O ,,
~ ~ .
' 'I ' tn in
O O O O O _ . ''.
~ rl
(~ 1) tO O ~
1 t~ ~ ~\ ~ ~ O .:
Q) ~ a) a) a) al ~ ~.
~ ~ :
~ ¢ ~ -
:
~ ~t7;Z6~
Table_2
~= Spurce ¦ ~pprox
. DC192 Dow~Cornîng Corporation 25,000 1:2.6
DC193 Dow_Corning Corporation 2,100 1:1.7
L546 Union Carbide Corporation 15,000 1:2.6
5_ _ ~ Union Carbide Corporation 14,000 lo~.S
; .
:
., . . . . . . -- -, :: ~ .. ,. . ,, , , -. , "-
~72~3191
,
36 .
Exampl e
Fibres were prepared from a solution of the following
compositi~n.
200g Aluminium chlorohydrate. tAl:Cl ratio 2 :1
23 . 8% w/w Al 23 )
s 94.49 Polyvinyl pyrrolidone solution ~ 3% w/w o~
k-90 grade to give 6% w/w Al203)
9.3g Polysiloxane copolymer A (Table I)
The solution was evaporated under partial vacuum at
35-40C until the viscosity at ambient temperature was
lS poise. The solution was extruded through small holes
240 microns diameter) and attenuated with air to yive dry
unfired fibres with a mean diameter o 4 microns.
The ibres were further dried at ~00C, heated in
steam at 350C for 15 minutes and fired at 900C for
15 minutes to give a strong white flexible product~
Chemical analysis showed that the ~ibre contained
5% SiO2 (w/w Al~03). Electron microscope examination
showed no evidence of oxide phases other than the
transition alumina phases.
Samples of fibxes were heated to the tempera~ure
given below. Surface area measurement by the nitrogen
BET method gave ~he ~ollow.ing resu~ts:
Temp. C Time (hr) SA m2/g
llO0 1 61
1200 2 40
X-ray phase analysis showed that fibres heated ~or
65 hours at 1200C were in the gamma and delta alumina
.
97;~6~
37.
ph~scs, with only a trace of the alpha phase detected.
Fibres heated for 1 hour at 1350C were in a mixture of
the gamm~, delta and theta phases, with no trace o~ alpha
alumina~
Exampl~ 2
Fibres were prepared as in Example 1, but with only
4.6g of the polysiloxane copolymer A to give 2% SiO2 w/w
Al~03. ~ibxes fired as described in Example 1 up to 9Q0C
and then fired for 1 hour at 1200C maintained flexibility
and strength. X-ray analysis showed only the gamma and
delta phases.
Example 3
Fibres prepared as in Example l, but co~tainin9 S%
SiO2 w/w Al~03 from the polysiloxane copolymer B instead
of A were fired as in Example 1 to 900C. Nitrogen
absorption measurements gave a surface area of 74 m /g
and a pore volume of 00083 cm3/g. The only phase present
on heating to 1000C or 2 hours was eta alumina~ After
heating to 1100C for 16 hours the major phase present
was gamma alumlna with a trace of delta alumina.
No evidence was obtained ~or an aluminosilicate or
silica phase.
Example 4
Solutions were prepared as in Example 1 using the
Z5 commercially available water-soluble polysiloxane ;~
copolymers DC 192, DC 193, L 546 and L 5340 listed in
Table ~I. Appropriate quantities were added to ~ive 2%
~ .
.
' ' ' ' ' ;;`'~.
' :
1~7Z~99
-ilica in the final alumina fibres which were spun an~
-.e~t - -tr~at~d as in Exampl~ 1 up to 900~C. After
~alcination at 900C the fi.bres were strong and flexible,
-.:ith no evidence of a mullite or alpha alumina phase by
,;-ray investigation. x-ray analysis on fibres heated to
1050C for 1 hour gave only transition alumina phases,
EXAMPLE 5
Fibres were prepared as in Example 1 using the
polysiloxane copolymer C to give the following combinations
of compositions, - all percentage weights expressed on the
Al203 content of the fi~res or solutions: :
5.1 5% SiO2
6% Polyvinyl pyrrolidone
5.2 5% SiO2
: 6% Polyvinyl alcohol - high molecular weight
water-soluble grade
5.3 1% SiO2
6% Polyvinyl pyrrolidone ~PVP)
5,~ 7.5/O SiO2
6% PVP
After heat treatment as in Example 1 to 900C all
fibres were strong and flexible.
EXAMPLE 6
A sample of the fibres prepared in Example 3 and
heated to 900C were sandwiched between 'Incoloy' (~rade
~lark) allo~ DS metal yauzes and tested for 50 hours in a
car exhaust stream on an engine test bed at temperatures up
to 750C,
-38
.
~C~7Z6~39
39~ ~
At the end of the test the total time at 750"C was
20 hours, with the majority of the remaillder at 500C~
Inspection of the fibrous pad aftex this treatment showed
that the fibre had not suffered signiicant damage or
~eight loss. X_ray analysis after treatment showed the
only phase present was eta alumina with a crystallite
size less than 80 A. The surface area after treatment
had increased to 110 m2/g.
E ample 7
~ibres were prepared as in Example 1 but with a
5% nickel content9 added to the solution as NiCl2.6H~O.
On firing as in Example 1 to 900C strong fibres were
produced.
Examl~le 8
Fibres were prepared as in Example 1 with 5% MgO
content~ added as MgC12.6H~O to the spinning sol-ltionO
On firing to 900C as in Example 1 strong white fibres
were produced. When heated in a hot-stage X-ray
apparatus, the fibres showed the pxesence of alpha
alumina at 1140C.
Example_9
Fibres were prepared to give a l:l w/w ratio of
ZrO2:A1203 with 7% w/w based on ZrO2 of rare earth oxides
~60% yttria grade) as a zirconia phase stabiliser and
containing 5% w/w of silica. The spinning solution was
prepared from the lollowing components:
:
:
,, : - , .. , . - : . , ... :,, .. . .. ~::
~726~
40.
~luminium oxychloride solution ~23.5Yo A120~ w/w~
Al:Cl, 2:1)
~irconyl acetate solution. (Commercial 22% w/w ~rO2
9rade3
Rare earth chlorides solution (60% yttria gracle)
Polyethylene oxide (3000,000 MW)
Polysiloxane copolymer B
The solution was evaporated, spun into fibres and
fired as in Example 1. After 1 hour at 1200~C thc fibres
were strong and 1exible. In comparison fibres prepared
from a similar solution without the siloxane additive
were weak and friable when fired to 1200C.
Example 10
Fibres were prepared as in Example 1 but usin~l the
siloxane copolymer D to give 5% SiO2A The solut.i~n p.rior
to spinning was cloudy and the unfired flbres prod~lced by
extrusion follcwed by attenuation with an ~ir str~m were
of variable ~eometric quality. The fibres wer~ heate~l in
steam at 350C for 15 minutes, followed by calc:in~t.ic>n at
1?00C for 1 hour to give white flQxible ~ibres. ~-r.ly
.~ analysis showed ~he fibres contained eta, gammc~ anc2~lelta
alumina with a minor amount of alpha alumina. Th~
presence of alpha alumina is thoug~t to be d- e t~ phase
separation (cloudiness) resulting in a lower effective
SiO~ content in some parts of the fired fibre. :
Example 11 .;~
A spinnin~ solution was prepared from the followi.ng
. components: -
.~ .
.:
.~ ,', .
,
~CI37269~
41.
200g Aluminium ehlorohydrate (23~8% ~1203 by weiyht
Al:Cl. 2:1)
2.85g Polyvinyl alcohol (high molecular wei~Jht
wat(~r-solubl~ ~Jrad~
140y Water
9.4g Polysiloxane copolymer C
The solution was evaporated to a viscosity ~f 15 poise
measuxed at ambient temperature and spun into fibres with
a mean diameter of four microns. The fibres were dri~d ~t
100C, heated in steam at 350C for 15 minutes and calcined
at 900C for 15 minutes. A sample of these fibres was
heated to 1200C on a hot-stage X-ray dif~ractometer at
a rate of 30C/hour~ Phases present at 800C were ch:i and .-~
eta alumina; the gamma phase appeared at 1020C and
reached a maximum at 1110C; the delta phas~ appc~ar~d at
1060C and reached a maximum at 1140C~ while the eta
phase had faded by 1150C. There was no ~vidcncc ~or
mullite or alpha alumina at 1200C, or on re coolin~ to : -
room temperature.
Example .l2
:
~ solution suitable for use as a binder or co~ting ~:
material was prepared by co-dissolving the ~ollowin~
components,
400g Aluminium chlorohydrate solution (2:1 Al:Cl ratio,
;. : -~
ly.Glacial acetic acid
lOg Polyvinyl pyrrolidone (K 60 yrad~
'~ .
" ~
.'- :,
.:
' : . '
::
~72~;99
~2.
24g Siloxane copolymer A (23.5~ w/w S:i02)
2009 of a graded tabular alumina grog were well-mi~ed
with 20~ of the above solution and presse~d into a ~l~ss
dishO Thc~ contents of the dish werc su~jectcd to
ultrasonic vibrat;.on for 30 minutes, and allowed to set
for 20 hours in a drying oven at 80C. The tablet so
formed was removed from the dish and heated to 400~C over
a 2 hour periodS and subsequently to 900C over a further
: 2 houxs. The tablet was then transferred directly into a
furrlace at 1400C and heated at that temperature for 1 hour.
After the tablet was removed from the furnace and allowed
to cool to room temperaturc, it was examined and found to
. be tough and free from surface cracks.
: Example 13
A 1-inch cube of ceramic honeycomb, suitable ~or use
as a car-exhaust ceramic matrix component, was coated with ~ "
' hiyh-surface area alumina using the so].ution prepared as ~;
. described in Example 12. The untreated cube had a .~
,, ,
specific BET surface area of 0~4 m /g, an estimatecl flat
geometric area of 200 cm2, and a weight of 13g. Thi.s
cube was soaked in the solution described above while
suspended on a fine wire, and then slowly withdrawn fr~m
the solution over a period of 5 minutes. The cube w~s
placed on a filter paper pad to allow residual solutio~
to drain off, and was dried at 80C for 10 minutes. The
cubc was subsequently heated in air at 350C or
10 min~tes and fired at 900~C for 15 minutes. ~ oolin~ ~ :
:
: :- '
. .
~726~
~3
~h~ w(~ t i ncrease was loun(l to b(` 0. (~1 all(l tll(` 1~1 '1`
s~ raco (~I' the cube was 4~ m /9.
I,xample 14
To 809 o~ the solution preparecl as dc?scri~ed .in
Example 12 was added 19 of chloroplatinic salt (0.49 Pt).
A ceramic honeycomb cube as used in ~xample 13 was coat~d
in this solution, drained, dried and fired to 900C as
described in Example 13. The increase in weight of the
cube was found to be 0. 8g, and the BET surface of the
cube was now found to be 4.3 m2/y.
~ :':' .
The silicone-po~yoxyethylene compound ~ having a
calculated silica equivalent of 46.5% was found tv ~ive
a cloudy mixture when added to an aluminium oxychloride
solution at a viscosity of 10 poise, which settled out
to give two distinct lay~rs of solution. Accordingly
compound E was mixed at a 50:50 volume ratio with
industrial methylated spiri~s, and this solution was :
carefully mixed with a 20 poise solution cont.aining 1% w/w
polyethylene oxide (molecular weight 300,000~ and 28~ w/w
A1203 as basic aluminium oxychloride, to give a clear
bubble~free mixture. This mixture was extruded through
small holes into co-current streams of high-velocity -.
humidified convergent air jets and collected on a wi.ro -~ :
gauze as fibre having a me~n diameter of 6 microns.
.' ' : .. '.:
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-
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,
Example 16
An amine-functional polysiloxane copolymer l~ contain~d
a 'silica equivalent' of 66.3%~
1.799 of this compound were mixed with an equal volume
of industrial methylated spirits and then titrated with
N/10 hydrochloric acid to give a pH reading of 4Ø This
solution was then mixed with 36.7g polyethylene oxide
solution (250 w/w of molecular weight 300,000) and lOOg of
23.8% w/w A1203 equivalent aluminium oxychloride solution~
The final mixture was evaporated down to a viscosity of ~-
20 poise in a vacuum rotary evaporator and blow-spun into
fibres having diameters in the range 2-3 microns.
Example 17
.76g of t-butoxy silatrane were dissolved in water
and filtered to remove a trace of insoluble material.
The p~l of the solution was adjustect to 4.0 with dilut~
hydrochloric acid and the solution was mixed with lVOt~
of 5/6 basic aluminium oxychlnride solution ~2~.59 ~
and 36.79 of a 2% aqueous solution of 300,000 molecular
weight polyethylene oxide. The mixture was eva~jorated
to a viscosity of 30 poise on a vacuum rotary evaporator
to give a clear yellowish solution. A samplc~ W-lS allowed
to thicken by evaporation in a glass dish and fibres were
pulled from the s~mple at the end of a spa~ula. ~n
stan~in~ for 20 hours a sample was found to h~ve set to a
gelatinous material. The fibres obtaine~ were treclte(t
with ammonia, heated in steam a$ 350C and fired at 900~C ~ ;
,
'
~7z6~
~5.
for 15 minut~s follo~ved by 1200C f~r 1 hour.
xarnple 18
Alumina fibres containing silica and boric acid wexe
prepared from the following composition:
2009 Aluminium chlorohydrate (Albright & Wilson,
23.5% A1203, 2:1 Al:Cl ratio)
29 Boric acid
5.69 Polysiloxane copolymer A
143g Polyethylene oxide (1% w/w 300,000 molecùlar weight)
The solution ~vas evaporated to a viscosity of 20 poise
and blow_spun into fibres having a mean diameter of
4 microns. The ~ibres were treated with 0.2% v/v an~monia
in air at ambient temperature, heated in steam at 350C
for 1/4 hour and fired at 900C ~or 1/4 hour, and inally
at 1300C for 1 hour. Phase analysis by X-ray dif~raction
show~d that the major phase was delta alumina with a minor
theta alumina phase and a smaller amount of an unidentified
phase. No trace of alpha alumina or mullite was d~tected.
A further sample of the fibre fired to 900C was reheate(i
at 1400C for 1 hour and found to contain a majox theta
aluminium phase and a minor alpha alumina phase: a~in
mullite was not detected~
Example 19
~ibres wer~ prepared from the following fcrmulatic>ns:
2009 aluminium oxyc,hloride ( 23~ 55r~ w/w A1203.
Albright & Wilson)
. ..
1389 Polyvinyl alcohol solution, 2~ w/w 7l`1vanol'(~rade klark~
50-42 in watc~r
':
..
~:117Z69~
~6.
~).2~ I'olysiloxane copolymer A
The solution was evaporated to a viscosity of 100 po~se
and allowed to stand for 20 hours. The solution was then
extruded from a bomb through a microfilter and out of ~
100 micron spinere~te hole. ~ibres were drawn down and
wound up on a rotating drum covered in polythelle film.
The fibres were removed from the drum, dried at 100C,
heated in steam containing 5% v/v ammonia at 350C for
- hour and fired at 1000C for -I- houra Samples of this
fibre were fired at 1200~ 1300 and 1400~C ~ox 2-hour
periods. Selected fibxes~ with di~meters approximately
10 microns were mounted on the head of a radi~ loud speaker
using sealing wax. The modulus of the fibres w~s measur~d
using the vibrating reed technique for lengths in tne
range 0.2 to 0.4 cm~ The loud speaker was fed from a
decade oscillator and the resonant frequency of the f ibres
was measured by observing the vibration at resonance
frequency using a travelling microscope. A graph was
plotted for each fibre of the fundament~l resonance
frequency fr against D/12, where ~ = diameter ~nd 1 = length
are found to be a straight line passing through the~ origin
within expected error. The specific modulus o~ the fi~re
(E/p) was then calculated from the slope M using tlle ormul~ -
, E~p = 0~074 M2 psi, whexe ~ = fibre density.
The xesu1ts for the relative specific modulus are
~iven below, compared with that of E-glass fibre ~L/~D = 1)
.,:
47 o
¦ l1iring Temperature (2 hr) C 11000 1200 jl~OO) 1400
... __ ............. __ .... ,_ l l
Rclative Specific Modulus (E/~ 1 1.31 I.5 1 2~:s
l~or comparison, similar fibres made from a Iormulatioll
not containing the copolymer and fired at 90~C gave ~In
E/~ value of 1.5, but on firing at 1000C this dr~ppcd
to 1 and at high temperatures the fibres were too brit-tle
for measurements to be obtained.
Example 20
~ibres were prepared from the following components:
200g Aluminium chlorohydrate ~23.8% w/w A1~03,
2:1 Al:Cl ratio)
142.8g Polyethylene oxide solution (lYo wfw 3009000 MW)
18.89 Polysiloxane copolymer A
The solution was evaporated to a viscosity of 15 poiso
and blow-spun into fibres havi~g a mean diameter of
3 microns. The fibres were collected and treated with
0.2% v/v ammonia gas in air, heated in steam at 350"C
for 1/4 hour and fired at 900C for 1/4 hour. Chemical
analysis indicated that the fibres contained a ratio of
~i2 Al23 of 9 100-
~ sample of fibre was heated for 1 hour at l200C.
X_ray analysis indicated that the fibres contained a
major delta alumina phase and a minor gamma phase. No
alpha alumina or mullite was detected.
A further s~mple was fired at 1300C for 1 hour,
This sample gave major phases o~ mullite and thcta alumina.
On firing a further sample to 1400C for 1 hour major
., '
~' :
7269
a~8o
~ha~ of mullite ~n(l the-ta alumina w~r~ pr~ nt~ Wi~
trace ~f alpha alumina detecte~.
Exa~ple 2l
Fibres were prepared as in Example 20, but with only
4.7g of the copolymer A. These fibres on heating for
1 hour at 1200C gave major gamma and dclta phases with
eta alumina also present. On firing for 1 hour at 1300C
major alpha and theta phases of alumina were observedO
After 1 hour at 1400C a major alpha alumina phase and
the mullite phase of alumino silicate was observed.
In comparison, a similar fibre of eta alumina
containing no silica gave a major alpha alumina phase
àfter 1 hour at 1200C. However a major delta phase
could be obtained by heatiny the pure alumina fibre when
in lts eta phase in an atmosphere ree from chloricle for
2 hours at 1050C. Heatin~ the pure alumina fibre at
1200C for a further 2 hour ~ave alpha alumina.
Example 22
Fibres were produced as in Example 20, but with the
requisite amount of copolymer A to give 5% silica w/w
total oxides in the final fired fibre. The fibre was
fired for periods o 1-20 hours at 1000C. Phase analysis
showed that ~fter 20 hours the phase was eta alumina with
an apparent crystallite size of 60 A. A sample of fibre
was set in epoxy resin and ion beam thinned with argon
ions to give a specimen suitable for transmission
election microscope (TEM) studies~ Examination of the
- .
:
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d~9
microstructure by TEM with modifications of up to 200,000
showed an even granular structure. No evidence was
obtain~d or the presence of more than one crystalline
phase, nor was there any evidenc~ for a non-homoc~erleous
dispersion of silica or silicate particles.
A sample of fibres fired for 20 hours at 1200C gave
a major del~a alumina phase by X-ray analysis. An lon- -
; heam thinned sample showed a granular microstructure
similar in orm to that previously described, although
dark field images showed larger crystalline regions of
the order of 500 A in size.
Further X-ray studies on the samples indicated the
~gree of crystallinity o the delta alumina was greater
than 25~o by weight, and the intensity of background
scattering was consistent with an amorphous component in
the order of 25~ by weight.
Example 23
~ibres were produced as in Example 20~ but with
suficient silica content from the copolymer A to give
7% by weight of SiO2:A1203. Aftex the 900C firing
stage, these fibres were refired for 3 minutes at 1500C
in a tube furnace. Transmission electra microscopy on
an ion beam thinned sample at a magnification of x 100,000
single crystal platelets apparently set in a glassy matrix.
Examination of a sample of this fibre by X-ray analysis
showed that the fibre cont~ined a major theta alumina
phase and a minor mullite phase. Stereoscan microgr~phs
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Z69g
so~
(Cam~)rid~ tereoscan ~2~) of these Libr~?s ~t ~1
magnification of lO,000 showed an apparently smooth
fibre surface.
A further sample of these fi~rcs heate~ t(~ 16
for 5 minutes h~d conv~rt~d to a major ~lph~ ~1lul11ina
phase with a minor mullite phasc~ Transmission el~ction
microscopy show~d anisometric single crystals of alpha
alumina with one dimension of~ 2000 A and a second
dimension of up to 2 microns.
A further sample in the form of a fibre blanket was
heated at l400C for 2~ hours. Thesc fibres had developed
a surface roughness when observed with the Stereoscan at
a mag~ification of 5,000. Fibres of pure alumina from a
similar formulation but without the silica, when heated
lS in an identical manner gave blankets of lower resilience,
and on Stereoscan examination showed surface features
corresponding to the formation of large alpha alumina
crystals which in many places crossed the visible surface.
~xa~ 24
Fibres produced as in Example 23 were heate~ in air
fox l hour at 1200C and shown to contain a major delta
phase of alumina with no trace of mullite or silica
phases.
In comparison, a sample of commercial alumina/silica
catalyst was analysed and found to have a similar
composition (3.8% Si, 42.2% Al). }larshaw aIumina
AL_1605P_12621_35_3] was found to give a small amount of
'` ':"
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10~72699
51.
cristobalite and ~ trace of mullite ~Yhen fired for 1 hour
at 1200C. E~urthermore, after 5 minutes at 1400C the
sample contained ~ major alph~ alumina phasc, to(~:ther
with t~leta alumina an(1 mullite.
I~`xampl~ ~5
~Comparative Exar?lc~ )
Fibres ~ere prepared from the follo~ving components:
2009 Basic aluminium oxychloride solution (Al:Cl ratio
1.7 1, 23% A1~03) -
8089 Silica sol (7Ludox~AM Trade Mark)(28.5% sio2)
The solution was evaporated down to a viscosity of
80 poise on a xotary vacuum evaporator, and spun on a
centrifugal spinner at 2500 rpm through small peripheral
holes to give fibres with ~ mean diameter of 10 microns.
The fibxes ~Jere dried at 80C ior ~ hours~ he~ted in st;eam
for 8 hours at 350C and fired to 1000C for 1/4 hour.
, X-xay analysis showed that these fibres contained the eta
i and chi phases of alumina, but on heating in a hot-stage
X-ray diffractiometer up to 1200C, in addition to
transition alumina phases, mullite was observed from 1160~C.
Fibres heated to 1200C were weak in comparison to those
produced as in Example 22 and heated in a similar manner.
' '': ''
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