AU620955B2

AU620955B2 - Non-adherent silicon elastomer composition vulcanizable at room temperature

Info

Publication number: AU620955B2
Application number: AU46993/89A
Authority: AU
Inventors: Jean-Marc Frances
Original assignee: Rhone Poulenc Chimie SA
Current assignee: Rhodia Chimie SAS
Priority date: 1988-12-22
Filing date: 1989-12-20
Publication date: 1992-02-27
Anticipated expiration: 2009-12-20
Also published as: FR2640987A1; JPH02202952A; EP0378952A2; AU4699389A; EP0378952A3; FR2640987B1; BR8906675A; CA2006290A1

Description

~ii COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952 !COMPLETE SPECIFICATIO NAME ADDRESS OF APPLICANT: Rhone-Poulenc Chimie Qua! Paul Doumer 92408 Courbevoie France NAME(S) OF INVENTOR(S): Jean-Marc FRANCES ADDRESS FOR SERVICE: DAVIES COLLISON Patent Attorneys I Little Collins Street, Melbourne, 3000.

COMPLETE SPECIFICATION FOR THE INVENTION ENTITLED: Non-adherent silicon elastorner composition vulcanizable at room temperature 40 4.4 4 6 4 4444 6 4 4 66 4 6646 6 0- 4 44 6 o 64 94 6 4446 6644 4 0644 The following statement Is a full description of of performing it known to me/us:this invention, including the best method o00 0 44 6 4 4 t 4 4464 4 6 6444 44 6 @4 44 p 1j5 2 The present invention relates to silicon elastomer compositions which are vulcanizable at room temperature (RTV), and more particularly to compositions formulated as two packages which are mixed at the time of use.

Such compositions are described in numerous patents, in particular in the French Patents No. 2,572,415 and 2,592,657.

However, the known compositions are often autoadherent, that is to say that they stick, once converted to elastomers, to the supports on which they have been deposited.

Moreover, these compositions generally contain a tinbased crosslinking catalyst (for example dibutyltin dilaurate). Now it has been found that the presence of tin O 15 can have an action which is harmful, with time, to the 00 00 o 4 stability of the compositions and to the properties of the elastomers obtained. In addition the presence of tin can be embarrassing, because of its toxicity, when such compositions

S

1 are used for medical or para-medical applications such as, for example, for the production of prostheses or of impressions in the dental field.

0"0 The present invention provides compositions which are vulcanizable at room temperature (that is to say in the region of 20-25 0 which are not auto-adherent (that is to S 25 say that the elastomers obtained with such compositions do 0 0 V. -1C catalyst. The compositions of the present i:ivention are vulcanizable at room temperature and have a setting time between 1 and 180 minutes, preferably between 5 and 120 minutes. The cross-linked elastomers are not sticky. Their superficial hardness in SAH, after 24 hours of crosslinking, is between 2 and The new compositions are especially well adapted for taking impressions, in the medical (for example dental), artistic or industrial field, and thus allow the production of moulds.

The compositions of the present invention, do not, after conversion into elastomers, adhere to the supports on which they have been deposited. They contain: a) an ,W -dihydroxypolydiorganosiloxane, the viscosity of which is between 500 and 1 000 000 mPa.s.

*tii b) a liquid product resulting ftom the hydrolysis of a compound of formula:

(R

1 0) 3 Si R 8 (1) ao 5 in which: al is a monovalent Cl to C12 hydrocarbon radical or a halogenated monovalent C1 to C12 hydrocarbon radical, and

R

8 is alkyl, halalkyl, aryl, haloylaryl, alkenyl, f t i t t j -4 cycloalkyl, cycloalkenyl, cycloalkyl or alkoxy, c) a crosslinking catalyst of formula (R 10) 3a Si R5- NH- R 2 in which: a is 0, 1, 2 or 3,

R

1 is a C1 to C12 hydrocarbon group, or a

R

7 3 Si- group, in which R 7 has the 6amue maaning asRI

R

5 is a Cl to 05 alkylene group,

R

3 represents: a Cl to C12, aliphatic, saturated or unsaturated, optionally halogenated alkyl, group, an OSiR 4 3 group in which R 4 has the same meaning asR1 a C5 to Cl2 cycloalkyl group, optionally substituted by halogen, or an aromatic group, and

R

2 represents: a C1 to C12 saturated or unsaturated alkyl group, a C5 to C12 cycloalkyl group, or 1(14 I I 9441 94 4 4 0I 04 ~i El.

Il 11 Li 5 a group of formula: 3 b -(R6)n H R Si (OR) 3-b Sabove R6 represents a Cl to C6 alkylene group n is 1 to 6, c is 0 or 1, and b is 0, 1, 2 or 3.

0 ft The composition of the invention comprises a) an LL-dihydroxypolydiorganosioxane, the viscosity of (4 ,and 400 000 mPa.s.

This a,u.--dihydroxypolydiorganosiloxane preferably has the formula: n i 1 -o (3) c is 0 or and -A n I L _i i j i i 11 i -i -i -iI 6 in which the R radicals, which may be identical or different, represent monovalent hydrocarbon radicals having from 1 to 10 carbon atoms each, optionally substituted by halogen or cyano, and n has a value such that the polysiloxane of formula has a viscosity of between 500 and 1 000 000 mPa.s. Preferably the R radicals are chosen from methyl, phenyl, vinyl and 3,3,3-trifluoropropyl.

The R radicals mentioned above comprise: alkyl and haloalkyl radicals having from 1 to 10 carbon atoms such as methyl, ethyl, propyl, isopropyl, butyl, pentyl, hexyl, 2-ethylhexyl, octyl, decyl, 3,3,3trifluoropropyl, 4,4,4-trifluorobutyl and 4,4,4,3,3pentafluorobutyl.

cycloalkyl and halocycloalkyl radicals having from 1 to 10 carbon atoms, such as cyclopentyl, cyclohexyl, methylcyclohexyl, propylcyclohexyl, 2,3-difluorocyclobutyl and 3,4-difluoro-5-methylcycloheptyl.

4 1 alkenyl radicals having from 2 to 4 carbon atoms, such S, as vinyl, allyl and 2-butenyl.

1 20 mononuclear aryl and haloaryl radicals having from 6 to .4t carbon atoms such as phenyl, tolyl, xylyl, chlorophenyl, dichlorophenyl and trichlorophenyl.

4 "4 cyanoalkyl radicals the alkyl chain members of which 0 44 4. have from 2 to 3 carbon atoms, such as P-cyanoethyl and p-cyanopropyl.

As concrete examples of R 2 SiO residues present in the

I

O* 0 I II I i I 1 i

I

f 7 alpha, omega-dihydroxydiorganopolysiloxane of formula (3) there may be mentioned:

(CH

3 2 SiO

CH

3

(CH

2 =CH)SiO

CH

3

(C

6

H

5 )SiO

(C

6

H

5 2 SiO

CF

3

CH

2

CH

2

(CH

3 )SiO

NC-CH

2

CH

2

(CH

3 )SiO

NC-CH

2

-CH

2

(CH

2 =CH)SiO

NC-CH

2

CH

2

(C

6

H

5 )SiO In the compositions of the present invention a 'mixture of alpha,omega-di(hydroxy)diorganopolysiloxane polymers which differ among themselves by the molecular weight and/or the nature of the groups linked to the silicon atoms can be used. In addition the polymer of formula can optionally contain RSiO 1 5 monoorganosiloxy residues and/or SiO 2 residues, in the proportion of at most 2% with respect 4t c to the number of R 2 SiO diorganosiloxy residues. In addition the diorganopolysiloxane can be a homopolymer or a copolymer I 20 such that, for example, different types of residues such as dimethyl, diphenyl, methylphenyl and the like are found in the chain, *aaa These alpha,omega-di(hydroxy)diorganopolysiloxanes are sold; in addition, they can easily be manufactured according to techniques which are now well known.

The composition according to the present invention Si rn 1 9 .r 9l 8 contains b) a product resulting from the hydrolysis of compounds of the formula: (R0) 3 -Si-R 8 in which:

R

1 is a C 1 to C 12 monovalent hydrocarbon radical or a halogenated C 1 to C 12 monovalent hydrocarbon radical, and

R

8 is alkyl, haloalkyl, aryl, haloylaryl, alkenyl, cycloalkyl, cycloalkenyl, cycloalkyl or alkoxy, and in this last case R 8 is preferably identical to R 1 0.

In this formula, the R 1 radicals can be alkyl radicals such as methyl, ethyl, propyl, isopropyl, butyl, amyl, isoamyl, cCtyl, isoor'tyl, decyl or dodecyl radicals, or haloalkyl radicals such as chlorinated, brominated or fluorinated alkyl radicals. In addition, R 1 can represent aryl, aralkyl and alkenyl radicals such as vinyl, allyl, phenyl, tolyl, xylyl, benzyl, phenylethyl, naphthyl, anthracenyl and biphenyl radicals, as well as the halosubstituted derivatives of the radicals specified above. R 1 can also represent cycloalkenyl, cycloalkyl and cyanoalkyl radicals.

44 ftf ft c 'ft 'ft ft II 4 f f Preferably a liquid product b) resulting from the hydrolysis of a monomeric silicate, that is to say a product of formula in which R 8 represents an alkoxy radical, is 4414 4 4 44.4 o.I a 4 0I( o @4 0

I

-9 used. Such products b) are obtained by carrying out a partial hydrolysis, in water, of the specific monomeric organosilicate in the presence of small proportions of acid up to a point at which it is still insoluble in water and at which it is still possible to isolate a liquid compound of the partially hydrolysed organosilicon type. Thus, ethyl silicate having the formula (C 2

H

5 0) 4 Si can be partially hydrolysed by addition of acids or of metal salts forming acids such as FeCl 3 CuClI, A1C1 3 or SnC1 4 to the liquid monomeric organosilicate, and then used in a hydrolysis of this mixture of ingredients in water to obtain a two-phase composition from which the partially hydrolysed organosilicate, which is insoluble in water, is easily separable from the aqueous phase and from the catalyst. Such a partially hydrolysed ethyl silicate is sold commercially under the brand name "Ethyl Silicate-40" by the Union Carbide o° Corporation.

0044 In a general manner, the silicate used is hydrolysed o such that the liquid product obtained contains less than Go S« ,20 and advantageously less than of unhydrolysed silicate.

Generally, in the composition according to the present invention, from 1 to 15 parts (by weight), and o° o preferably from 2 to 12 parts, of the liquid product b) are 0 0 added per 100 parts of the a, -dihydroxypolydiorganosiloxane the viscosity of which is between 500 and 1 000 000 mPa. s.

4* 0 41b 1, I 4 The composition according to the present invention contV.'; 28 crosslinking catalyst the product c) of formula (R 0) 3- Si R NHR- (2) in which the v'alues of a and the meaning of R 1

R

2

R

3 and R have been specified above in the description. It can be noted h-ere that if R 1 means R 7 3 Si-, the R 7 groups are generally

NI

identical among themselves, but that they can optionally be diffren frm ech the, R 3 Si- being capable, for example, of representing (CH 3 2

(C

6

H

5 )Si-- Ito As an illustration ,R2 and R3 can in particular represent: ij -alkyl radicals such as methyl, ethyl, propyl, butyl dodecyl radicals, these radicals being capable of being halogenated, for example by chlorine, -alkenfrl radicals, such as vinyl, cyclopentyl and cyclohexyl radicals, phenyl radicals (except, for R.

2 The R 5 alkylene group can represent in particular the methylene -(CH 2 ethylene -(CH 2

-CH

2 propyl~ene -(CH 2 tetramethylene -(CH 2 4

-CH

2

CH

2

-(CH

3

-CH

2

CH(CH

3

)-CH

2 pentamethylene -(CH 2 5 and isopentylene -CH 2

-CH

2

-(CH

3

)CH-

mom 4k I f 11

CH

2 groups. Preferably R 5 represents -(CH 2 3 The quantity of catalyst of formula introduced into the composition is such that it can catalyse the crosslinking with the required setting time already specified above in the description. The composition of the present invention generally contains between 0.05 and 5, preferably between 0.1 and 3 milliequivalents (meq.) of -NH-R 2 group (of the product according to formula 2) per 100 parts (by weight) of the a,u--dihydroxy-polydiorganopolysiloxane a) the viscosity of which is between 500 and 1 000 000 mPa.s.

These amine-containing silanes of formula can easily be prepared by using, in particular, the teaching of the article "Synthesis of 3-amino alkylsilicon compounds" J.L. Speier, C.A. Roth and John W. Ryan, J. Org. Chem; vol 36, No. 21, 1971 pages 3120-3126, o00 0 The compositions of the present invention can contain 0 4 a small quantity of water, this water being in a qcuvity 94 generally less than or equal to advantageously less than and preferably less than with respect to the 20 weight of the a,cA-dihydroxypolydiorganosiloxane used and which is discussed above in a).

This water can be added to the composition or be brought into the composition, for example when a filler is added to it which itself contains a little water.

Preferably the compositions of the present invention contain a filler or a mixture of fillers, as well as oa 0* 12 12 optionally an a,L-bis(trialkylsiloxy)dialkylpolysiloxane oil, for example a,LD-bis(trimethylsiloxy)polydimethylsiloxane of viscosity which is generally lower than that of the o ,LdihyCroxypolydiorganosiloxane used which is discussed above in a).

These fillers can be in the form of very finely divided products the mean particle diameter of which is less than 0.1 micrometre. Among these fillers are calcined silicas and precipitated silicas; their BET specific surface is generally greater than 40 m 2 /g.

Thesn fillers can also be in the form of more coarsely divided products, of mean particle diameter greater than 0.1 micrometre. As examples of such fillers there may be mentioned ground quartz, diatomaceous silicas, calcium carbonate, calcined clay, titanium oxide oi the rutile type, iron, zinc, chrome, zirconium and magnesium oxides, the o h O different forms of allumia (hydrated or unhydrated), boron nitride, lithopone, barium metaborate, barium sulphate and glass microbeads; their specific surface area is generally less than 30 m 2 /g.

These fillers may have been modified on the surface by treatment with the various organosilicon compounds normally employed for this use. Thus theSr organosilicon compounds can be organochlorosilanes, diorganocyclopolysiloxanes, hexaorganodisiioxanes, hexaorganodisilazanes or diorganocy .lopolysiloxanes (French Oa Q 7 6, s 13 Patent FR-A-1,126,884, FR-A-1,136,S85 and FR-A-1,236,505; British Patent GB-A-1,024,234). The treated filer.s contain, in most cases, from 3 to 30% of their weight of organosilicon compounds.

When the compositions according to the pr.-sent invention contain a filler (or a mixture of fillers), they generally comprise, per 100 parts (by weight) of a,L-dihydroxy-polydiorganosiloxane from 1 to 200 parts, preferably from 5 to 100 parts of fillers.

The compositions according to the present invention generally comprise from 0 to 100 parts of c,l-bis(trialkylsiloxy)-dialkylpolysiloxane oil (which has been discussed above) per 100 parts of the a,L-dihydroxypolydiorganosiloxane a).

The compositions of the present invention, when they t are put in contact with the most varied supports, allow elastcmers to be obtained which do not adhere to these supports. It has thus been ascertained that there is no adherence to: ivory (for example teeth for taking impressions, or reproduction of carve' statuettee), wood, metals (such as aluminium, iron and the like), glass, and plastic materials (for example polyvinylchloride, a s polyamides, polycarbonates, polymethylmethacrylate and the like).

The compositions of the present invention can thus be used, in particular, for the manufacture of silicone B* e a i* i( 14 elastomer moulds intended, for example, to reproduce pieces in cellular or acellular materials, constituted of organic polymers (polyesters, polyamidc~ or polyvinylchloride). The moulds obtained with the compositions according to the present invention lend themselves particularly well to the reproduction of polyurethane pieces, since they resist well the attack of the constituents of the mixtures which allow polyurethanes to be obtained (in particular polyisocyanates).

The invention is illustrated in the following Examples.

EXAMPLES 1 TO 12: The following examples were carried out by mixing (by weight) first of all, (to obtain a first mixture PI)s 100 parts of an (,c-dihydroxypolydimethylsiloxane oil of viscosity 14 000 mPa.s at 70 parts of an a,u>-bis(trimethylsiloxy)- 0 t polydimethylsiloxane oil of viscosity 800 mPa.s at 25 0

C,

50 parts of a calcined silica of specific surface area S 300 m2/g, treated with hexamethyldisilazane.

S 20 50 parts of ground quartz of mean particle diameter micrometres, 5 parts of a calcined silica of specific surface area a£a 150 m 2 and a quantity of water, in grams, specified in Tables 1 and 2 below.

To 100 parts of this mixture P1 are then added: a >a C C 8 0a i~i~gl le 1 15 A) 3.547 g of a hydrolysed ethyl polysilicate comprising: 0.6% of Si (OC 2

H

5 4 39% of (C 2

H

5 0) 3 SiO1/ 2 groups 42.4% of (C 2

H

5 0) 2 SiO 2 2 groups 18% of (C 2 H50)SiO 3 2 groups (the 3.547 g of this polysilicate thus correspond to 1.418 x 3.547 100 50.3 meq of OC 2

H

5 B) 1 meq (milliequivalent) of -NH-R 2 of the aminecontaining silane of formula the meanings of R 1

R

3

R

2 and the values of a being specified, for each example, in Tables 1 and 2 below. The mixture of A B is called the "crosslinking system".

The mixture of P1 with the "crosslinking system" allows a composition according to the present invention to be 15 obtained.

In Tables 1 and 2 below: Ts means setting time, in minutes.

The setting time of the composition is measured by noting the time during which this composition has a sufficiently fluid state to spread out under its own weight and thus take the configuration of the internal volume of the receptacle into which it is poured.

The test used to estimate the setting time is the following: the composition which has just been obtained by mixing P1 and the "crosslinking system" is poured into an aluminium 4 4 4 44 44 44,4 4 440 &41 4444 4 44 04 4 Po 4 44 t 4 4 4 4 4 4 t 4 44 14 4 1~Y_1/ 16 capsule, of cylindrical form, 4 cm in diameter. The poured composition must show, after a period of at most 5 minutes, a perfectly horizontal surface.

SAH means Shore A hardness of the product obtained (elastomer) after 24, 48 or 72 hours.

a number of days followed by a temperature (for example 7d at 70 0 C) means that the "crosslinking system" has undergone this treatment (of aging) before being mixed with P1 to produce the composition according to the present invention, the quantity of water used corresponding to that I indicated just above, in the example under consideration.

contr., for Examples 4 and 9, means that if R 2 is a hydrogen atom or a phenyl group, compositions according to the present invention are not obtained.

*r 0 00 *0 Q -0 0 0 0C 00 D 00 0 i l ^1

L

TABLE I 1. 5 2 (Ro) -Si-nR -NH- 1

R

with R =(CH2)3 Example 3 2 2 S SAH -i3 SAl H 9 in min 24 h 48 h 72 h 1 0 -H2 -(0H 2 11

-CH

3 0.18 30 9 16 19 -C{-Cit

I-(CH)J-CH

2 0 2 3 2113 0.18 26 12.5 16.5 19 7d. 70 0 c 18 11 15.5 18 70or 20 9 15,5 19,5 3 0 -CH 2

-CH

3 (CH 2 oH 3 0.18 11 14 23 0.11 22 14.5 20 21.5 0.075 38 14 19 23 4 contr. 0 -CH2 -CH3 H 0.18 22 0 2 6 0 CH 2

H

3 -C(CH93YCH 2 -C(CH.3 3 018 120 245 10 17 6 3 -osi(CH-T9 -(CH 2 7

-CH

3 0.18 60 17 20 24 7 1 -CH 3 1-CH 3 -(CH )2-CH 3 0.18 20 10 5 17 i a

A.

1.2 0* TABLE, TT (R10) 3- SI R 5 N" -R a witfl R 5 (C4 Examp ,p R 1 H~ 2 0S SAil SAil SAil g in min 24 h 48 h 72 h CrH 2 7c(ce,) -(Cll 2 3

CH

3 -(CH 2 11 cp 3 0.18 12 17 9 contr. 0 3

C

6 5 0.18 -0 0 0 0 -CH 2 7CH 3 -(CH 2 7 -CH 3 0-18 21 12.5 18.5 19.5 7d. 70 0 c 19 11.5 17 18.5 70 0 c 16 11 18 19 11 0 CH 2 CH 3

-(H

2 3 -CH 3 0.18 16 13 18 21.5 7d. 70 0 C 14 12.5 17.5 12 0 -CH 2 :-CH 3

-C

6 1 1 0.18 36 6 16,5 19,5 -(cyclohpxyl) 7d- 70 0 c 32 5.5 it

A

I

'a) 'i i1

I

19 EXAMPLE 13: To a mixture P2 consisting of: 100 parts of an a,-dihydroxypolydimethylsiloxane oil of viscosity 40 000 mPa.s at 25 0

C.

are added: A) 3.547 g of a hydrolysed ethyl polysilicate as defined in the preceding examples, B) 1 meq (milliequivalent of -NH-R 2 of the amine-containing silane of formula (2) where R 1

CH

3

-CH

2

R

2

CH

3

-CH

2

-CH

2

-CH

2 a 0 The mixture of A B is called the "crosslinking system". Mixing P2 with the "crosslinking system" allows a composition according to the present invention to be obtained.

The setting time Ts has the same meaning as for the preceding examples, and the Shore A hardness of the product 15 obtained (SAH of the elastomer) is measured in an identical manner.

Ts setting time 88 minutes at 20 0

C

Shore A hardness: after 24 h Above Face towards the air Below Confined face after 48 h Above Face towards the air 12 Below Confined face 7 EXAMPLE 14 This is carried out in the same manner as Example 13, except that the quantity of amine-containing silane of 0 0 0000 0 0 0 O06 0 0 00 1 00 0 0 00 0 0 00 99 S t It 1 4 1 20 formula is reduced to 0.5 meq (milliequivalent of -NH-

R

2 A settingi time Ts is found 168 minutes at 20 0

C.

Shore A hardness: after 24 h Above Face towards the air 7 Below Confined face 1 after 48 h Above Face towards the 12 Below Confined face 44 4 4 4 4 44 t4 t

Claims

1. Non-adherent silicone elastomner composition which is vulcanigable at room tempe-rture, comprising: an o<,4 -dihydroxypolydiorganosiloxane, the viscosity of which is between 500 anid 1 000 000 mPa.s, a liquid product resulting from the hydrolysis of a compound of formula: (Rl0) 3 Si R 8 (1) in which R 1 is a monovalent C! to C12 hydrocarbon radical or a halogenated monovalent Cl to C12 hydrocarbon radical, and -R 8 is alkyl,, haloalkyl, aryl, haloaryl, alkenyl, cycJloalkyl, cycloalkenyl, cycloalkyl or aikoxy, a crosslinking catalyst of~ formt-1a (Rl0)3-a -Si R5- NH -R()2 R3a in which: a iV 0, 1, 2 or 3, RI is a Cl to C12 hydrocarbon radical, or a R73si- group, in which R 7 has the same meaning as IR'5 is a Cl to C5 alkylene group, .4 -22 -R1 represents: *a C1 to C12, aliphatic, saturated or unsaturated, optionally halo;yenated alkyl group, a ~n OS iR 4 3 group in which R 4 has the same meaning &s R 1 *a C5 to C12 cycloalkyl group, optionally substituted by halogen, or *an aromatic group, and R 2 represents: *a C1 to C12 saturated or unsaturated alkyl group, *a C5 to C12 cycloalkyl group, or *a group of formula: jR Si (OR 3-b in which: R 1 p 3 and R 5 have the meanings given above, R 6 repra-Seljts a Cl to C6 alkyl.ene group, n is 1 to 6, c is 0ori,1 and b is 0, I, 2 or 3.

2. Composition according to claim 1, in which R 8 is alkoxy. I I I 4 94 y J 1~ 9! "d, 4 23 alkoxy.

3. Composition according to claim 2 in which R 8 is identical to R 1 0.

4. Composition according to any one of the preceding claims, which contains in addition a small quantity of water.

Composition according to any one of the preceding claims, which also contains a filler.

6. Composition according to claim 5, in which the filler comprises silica.

7. Composition according to any one of the preceding claims, in which product b) results from the hydrolysis of an alkyl silicate and contains less than of this silicate in the unhydrolysed state. 15

8. Composition according to any one of the preceding claims, in which product b) results from the hydrolysis of ethyl silicate Si(OC 2 H 5 4

9. Composition according to claim 8, in which product b) results from the hydrolysis of ethyl silicate and contains less than 6% of this silicate in the unhydrolysed state.

10. Composition according to any one of the preceding claims, which contains (by weight) per 100 parts of an a, Co-dihydroxypolydiorganosiloxane the viscosity of which is between 500 and 1 000 000 mPa.s: 1 to 15 parts of a liquid product resulting from 4O 4 4) 4 4; r(L 4 4 44 04 444,. 4 44r 4', 4 4.4 .4 4 4 4 r t -i *1 24 the hydrolysis of a compound of formula 0.05 to 5 milliequivalents of -NH-R 2 group of the product according to formula from 0 to 1 part of water, from 0 to 200 parts of filler, and from 0 to 100 parts of a,C3-bis(trialkylsiloxy)- S*Q diorganopolysiloxane oil.

11. Composition according to any one of the preceding claims, in which R 5 represents the -(CH 2 3 group.

12. Composition according to claim 1 substantially as described in any one of the foregoing Examples 1 to 3, 5 to 8 and 10 to 14.

13. An impression or mould made using a composition according to any one of claims 1 to 12. Dated this 28th day of November, 1991 RIONE-POULENC CIIIMIE, By its Patent Attorneys DAVIES COLLISON CAVE G e