DE1745171A1 - Process for the production of elastomer-forming siloxane compositions - Google Patents

Description

DR. R. POSCHENRIEDER

DR. E. BOETTNER
DIPL.-ING. HJ. MÜLLER 1745171

Patent attorneys

Munich 80 P 17 45 171.7-44

Lucile-Grahn-StraBe38 -η * λ π

/ Eat

Midland Silicones Limited, Reading Bridge House, Reading, Berkshire, England

Process for making elastomers? educational ».

Siloxane compositions

The present invention relates to a process for the production of elastomer-forming siloxane compositions and the elastomers made therefrom.

Siloxane compounds, which have the property Cure to rubber-like materials at room temperature or near this temperature are on known, and they are used on an industrial scale, for example for coating substrates, for electrical insulation, as embedding materials and as impression compounds, e.g. for the production of Casting molds, products of this type have hitherto been supplied as single-pack preparations that vulcanize, when exposed to the atmosphere, as well as preparations that mix the contents of two Require packets for vulcanization to take place. If also the recently developed single-package products have found a broad technical application, there are still numerous areas of application, on which the two-päokchen materials have proven to be more useful and are therefore superior to single-pack materials »

Ea has now been found that an improved elastomer-forming Maas ", which in the form of a β 2wei-

- 2 - ·

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packet product can be made available, If you combine a polydiorganosiloxane, you get two or three silicon-bonded polydiorganosiloxanes Alkojcyreste bonded to each terminal silicon atom are, contains, with a hydroxylated polydiorgan siloxane and a condensation catalyst, wherein a certain ratio of silicon-bonded alkoxy groups to silicon-bonded hydroxyl groups in the mixture is set.

Accordingly, the present invention relates to a method for producing an elastomer-forming composition which characterized in that a mixture is formed from

(A) at least one polydiorganosiloxane, its organic Residues of monovalent hydrocarbon groups, halogenated monovalent hydrocarbon groups or cyanoalkyl groups and the end groups of the general formula

-SiR » _a (OR ') ₃ . _a

contains, in which a has the value 0 or 1, R "denotes a monovalent hydrocarbon ^{radical or a monovalent halogenated hydrocarbon radical and R 1 represents} an alkyl radical with fewer than 7 carbon atoms,

(b) a polydiorganosiloxane which contains terminal, silicon-bonded hydroxyl groups and has a viscosity of at least 200 centistokes at 25 ⁰ G and

(c) a condensation catalyst,

where the ratio of the total number of -OR 'residues that be introduced into the mixture through component (a), to the total number of hydroxyl groups that through the component (b) are introduced, is 1: 1 to 35: 1.

109839/1297 " ³ "

7 4 517

The present invention also relates to a method for the production of organopolysiloxane elastomers, which through the working stages of the processing of the polydiorganosiloxane (a) with the hydroxylated polydrolganosiloxane (b) and the condensation catalyst (e), deforming of the mixture to the desired shape and allowing it to harden until an elastomer is formed is.

The polydiorganosiloxanes which form the component (a) required for the process <ier present invention are characterized in that there are two or Cvei, alkoxy groups on, each? terminal .Si] .ieiumatorn contained in. the molecule bound. To these Pol.yd.lcr-4, .Γ: ίΐθ £ ίΓιoxaaen born beiapieioweise those cU-i

j (I.
a i
ί
ί - -a " 1 j ί he dc is il it whom Igge de y ii. t, ο] ■: t $ e: riW € ~ · Ι J-- t
Λ '. l C. ■ - 1 X rl r:

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u.1. . ur

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Amine, or using other suitable conditions which are able to catalytically accelerate the ^{reaction of the radicals SiOH + SiOR 1, which takes place with the release of an alcohol.} Such polydiorganosiloxanes and processes for their preparation are described in British Patent 957,255, for example.

Purely one use as component (a) according to the teaching of the present invention-also suitable are polydiorganosiloxanes in which the terminal silicon atoms, which contain alkoxy groups bonded to it, to the remainder of the polysiloxane chain through other bridge members are bound as siloxane bridges, for example by means of a divalent hydrocarbon radical or a divalent hydrocarbon radical containing oxygen in the form of ether groups. Polysiloxanes of this type can e.g. be represented by the following general formula:

(R'O) ₃ - _a Si

-X - Si

■ 0 Si -

Jn L

—-X -

In this formula, a, n, R ¹ , R "and R have the meanings given above, and X stands for a divalent hydrocarbon radical or an oxygen-containing carbon atom, for example the ethylene, propylene, butylene or rolymethylene group.

Po ^.; .- · ■: ■ Λorgs.r,;!? Ilo>: ane, in which the end groups at the '^ lvo :, Loxa, -. "Grease over divalent.

09839/1 29

residues are bound, preferably by a Accelerated addition by means of a platinum catalyst an alkoxysilane containing a silicon-bonded unsaturated radical, such as the vinyl radical, to a palydiorganosiloxane, which contains hydrogen atoms bonded to terminal silicon atoms, prepared as for example, is described in British Patent Specification 957 554.

3? For the purposes of the present invention, the organic Residues in the polydiorganosiloxane (a) consist of monovalent hydrocarbon residues, e.g. alkyl residues, such as methyl, ethyl, propyl or octadecyl groups from Alkenyl radicals, such as vinyl or allyl groups, from alkaryl radicals, such as benzyl or phenylpropyl groups, and from aromatic residues such as phenyl or ITaphthyl groups, and from monovalent halogenated hydrocarbon radicals, such as chloromethyl, 2,2,2-, erifluoromethyl or 3,3,3-trifluoropropyl groups. They can also consist of cyanoalkyl groups. The radicals R ″ and R in the general given iOrrael can therefore consist of any one or more of these groups. Preferably, however, the organic radicals in the polydiorganosiloxane consist of methyl, phenyl, vinyl or trifluoropropyl groups, and at least about $ 50 of the total organic residues should consist of methyl groups. Usually they are Polydiorganosiloxanes which can be used with particular advantage those in which essentially all of the nonterminal radicals are methyl groups.

The silicon-bonded alkoxy groups present in the polydiorganosiloxane (a) are said to be desirable be limited to those who are terminal Silicon atoms are bonded. Accidental hydrolysis

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and condensation during manufacture and storage of the Polydiorganosiloxanes can, however, be the reason for the fact that a few alkoxy radicals are also present, the are bonded to silicon atoms, which are in the polysiloxane chain are not in an end position, and it goes without saying that in addition to the polydiorganosiloxanes, which are used for the purposes of the present invention also include those which have such additional Have alkoxy groups. It also goes without saying that the polydiorganosiloxane (a), which is desirably substantially linear in structure, including minor amounts of chain branching units may contain, for example, mono-organosiloxane units, provided that the polymer molecule remains essentially linear in configuration. Even if the silicon-bonded alkoxy groups, which are present in component (a) can be of any type, provided, however, that they are less than 7 carbon atoms, it is particularly advantageous if this radical is from the propoxy group consists.

The polydiorganosiloxanes (a) can vary in viscosity from free-flowing liquids to highly viscous materials, the viscosity selected in each individual case being related, for example, to the flowability or the ratio of silicon-bonded alkoxy radicals to silicon-bonded hydroxyl groups, which can be found in the Desires elastomer-forming mass. In general, it is recommended to use, as polydiorganosiloxanes (a) those having a viscosity from 30 to 50,000 centistokes at 25 ⁰ C.

The polydiorganosiloxane component (b) is an

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essential linear organosiloxane Polyieeri sat or -Mischpolymerisat used, in welGhem the organic groups consist of monovalent hydrocarbon radicals ^ monovalent halohydrocarbon radicals or cyanoalkyl groups, such radicals have already been explained above in connection with the polydiorganosiloxane (a). The polydiorganosiloxane salt hydroxyl groups, which are practically coming into being, should contain, on average, about two esadstänäige silanol groups (C-SiOH) per molecule. Bas presence * of. quite a bit. ^: Sriorganosilaxy-Restem as Eettea-ta Eadglleö the polymer is selässigj and kömiea ¥ ort © ilhafterweiee even .eiaf © »" ftitet.werdeSj gewilaeehiisrifalls ixü the modulus of iralfcanif iertes ElastöasereE zn Yerainders However sollt® ¥ 02 - = ssgsweise..? "the öurohselmlistlieh © - number cter _: sB, ßstäaclig®ss. .Silaaolgruppea pr © MoIaMiI ia feil! Ijä ^ oxyli ^ -äsa PqIj = - öiorganosiloxaa alGbt little? ale I ₅ 73 1jefeagea _o

oil © gsmäl ß @ r

rfiaaimg Ter ^ eadat.weröea ₉ fconnmi ia ites sohMaakea swiacliea 200 nmi 100Ö00 at 25 G; oSer wq> gL · iaiSlierea rfertea «You stelloa

slaä. dl © önseto

s®il ^: ÖG3 "v'QSisal'isis ^. ^ i? -, a

Polysiloxane (b) existing silicon-bonded hydroxyl groups * between 1: 1 and 35: 1, preferably between 1: 1 and 20: 1. As was found, the Hasse's vulcanizing properties worsened, though Ratios outside the stated quantity ranges are used. If you want the elastomer-forming mass give an optimal vulcanization speed and the best physical properties of the elastomeric product, so it is advisable to use the particularly preferred range from 5: 1 to 15: 1 for the ratio of -OR'-radicals to adhere to the OH groups.

The relative amounts of components (a) and (b) that are incorporated into the composition can be within further Limits vary, depending, for example, on the viscosity or the vulcanizing properties that one has to be found in the elastomer-forming Hassen, or depending on the properties which the finished vulcanized Should have elastomers. So it is possible within fairly wide limits, the curing speed the elastomer-forming Hasse by increasing the ratio of the silicon-bonded alkoxy groups increase the silicon-bonded hydroxyl groups in bulk. Such an increase can thereby be brought about be that the proportion of the polysiloxane, which contains the specified alkoxy radicals, greater power. For reasons of economy, however, it is generally more advisable to use only the minimum amount on the relatively more expensive alkoxy group-containing polydiorganosiloxane component, which the desired Vulcanizability of the mass guaranteed to apply. It is therefore more advantageous to eliminate any deficiency in the desired ratio of alkoxy groups to hydroxyl groups to be balanced to a certain extent by using the polydiorganosiloxane (a) or a part thereof replaced by a low molecular weight diorganopolysiloxane, which has a relatively higher proportion of

109839/1297

terminal, silicon-bonded alkoxy groups per Contains unit weight. The polydiorganosiloxane component (a) can thus consist of a single high molecular weight or low molecular weight polymer component, or it can consist of two or more different polymers which have different molecular weights and / or viscosities exist.

From the foregoing it can be seen that, in accordance with the teaching of the present invention, elastomer-forming compositions can be produced which have a wide range of vulcanization rates and flowability properties. In this regard, the method and compositions of the present invention are superior to known two-component vulcanizable siloxane compositions such as those made from a hydroxylated polydiorganosiloxane, an alkyl silicate and a condensation catalyst. The compositions according to the present invention are also superior to the known products mentioned in that, when they are applied in a thin layer, they have an improved hardening capacity.

The masses of the teachings of the present invention are prepared according to as a condensation catalyst, any material contained, which is capable, the reaction between a siliciuni-bonded alkoxy group and water, or or the reaction between an siliciumgöbundenen alkoxy group and a silanol group catalytically to accelerate. Catalysts of this V / irkungsr ': -ntung ij'.ru] learning expert is familiar to him, and to leri' ■ "■■ the ijwec /: - the vorj.iogendön invention preferably in ■: .-: /?.. .. ■ i <oa ~ meris.- ·: catalysts include ^{urganometai.lv/:} ';, .uc; ou,?.

■ QSÖ39 / 1297 ^·:; ·

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e.g. the metal salts of monocarboxylic acids, such as dibutyltin diacetate, Dibutyltin dilaurate, stannous octoate, zinc 2-ethylhexoate, tin oleate and zinc naphthenate, as well Amines and amine salts, such as tert-butylamine, hexylamine, Naphthylamine, hexylamine acetate and ethylamine formate. A another, albeit less recommended, catalyst type that can be used are the titanium esters, such as isopropyl titanate, butyl titanate or octylene glycol titanate. The catalysts that can be used with a special door part are the organic tin compounds such as dibutyltin dilaurate and stannous octoate and mixtures the same.

The amount of catalyst to be used is not about critical within a narrow framework; in most cases an amount of about 0.1 to about 5 parts by weight based on 100 parts of the total weight of the components (a) and (b), proved to be sufficient. '

In addition to the essential ingredients mentioned, the compositions of the invention can contain other materials which are normally used in the production of silicone rubber-forming compounds, for example fillers, pigments, additives to improve the heat resistance and the adhesion of the Rubber on substrates such as metals, glass and organic polymers. Purely for most purposes the use of masses provided with fillers is advantageous, and suitable fillers include e.g. ground quartz, pyrogenic silicon dioxide, silicon dioxide obtained by precipitation, Calcium carbonate, aluminum oxide, titanium dioxide, zirconium silicate, Zinc oxide, ferric oxide, magnesium oxide, organic fillers such as carbon black and synthetic resin powder, and finely divided ones Metals such as aluminum or copper powder. If so desired the fillers can be treated with organosilicon compounds or other materials in order to

10 9 8 3 9/1297 - 11 -

modify surface properties. The amount of The filler used is in most cases determined by the intended use for which the compound is intended and can vary within wide limits. Usually the total filler addition is about 10 to about 300 parts by weight for every 100 parts the total weight of components (a) and (b).

The elastomeric compositions made according to the teachings of the present invention can also be converted into an elastomeric foam material by incorporating a suitable blowing agent into the composition. The foaming of the mass is preferably brought about by incorporating into it a polysiloxane which contains silicon-bonded hydrogen atoms and a hydroxylated organic compound or organosilicon compound, which react together as a blowing agent, releasing hydrogen. A methyl hydrogen polysiloxane is preferably used as a polysiloxane which contains silicon-bonded hydrogen atoms. Suitable hydroxylated compounds include water, alcohols and glycols. The hydroxylated compounds which can be used with particular advantage are the hydroxylated low molecular weight dimethyl polysiloxanes.

The elastomer-forming compositions according to the invention can be vulcanized at normal room temperatures. If desired , the rate of vulcanization can in certain cases be increased by heating, but the application of heat is not essential to convert the composition to a rubbery material. For storage and shipping, two of the three essential components are preferably packaged separately from the third component, and ■■ - ■. & ■? r .. ~

1 night 9 8 3 9/1 2 9 7 -:; ..-

Halt of the two parcels are then mixed together when the vulcanization of Hasse is to take place. To this In this way, premature thickening or hardening of the compound can be avoided. Usually it is recommended » to pack the catalyst (c) separately from the mixture of the organopolysiloxane components (a) and (b).

The vulcanizing capacity of the compositions according to the invention can, if desired, be modified by the careful addition of water, an amount of up to 1 percent by weight, based on the total weight of components (a) and (b), normally being used for this purpose as has proven sufficient. The incorporation of the water in this way can take place either before or during the mixing of the three essential components. Any suitable method can be used for this purpose, E.g. distributing the water with the help of a filler before incorporating the filler into the mass.

The elastomer- forming compositions according to the present invention are industrially useful for a variety of purposes; this includes, for example, the embedding and insulation of electrical device points, the production of casting molds, the use as sealing compounds and sealing agents for buildings and other components, as well as the use as coatings on textiles and other substrates, on which they can, if desired, in the form of a dispersion or Solution can be applied.

The following examples explain the invention in more detail; here TS mean the tensile strength; E is the elongation; H is the hardness in Shore Α degrees; T is the tear resistance. All measurements of the physical properties of the rubbers given in the examples were made

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according to the provisions of British Standards 903 Part A7 (195 ^, Part A2 (1956) and Part A6 (1957).

example 1

50 g of a terminal silanol-terminated polydimethylsiloxane (viscosity 2,000 centistokes at 25 ⁰ C), 50 g of a by groups of the formula

- Si - (OCH ₂ CH ₂ CH ₅ ) ₅

terminally sealed polydimethylsiloxane having a viscosity of 2000 centistokes at 25 ⁰ C, and 100 g of an under the label "Minusil 5 yu" sold commercially, ground Siliciumdioxyds were intimately mixed on a three roll rubber mill. The ratio of - (OCH ₂ CH ₂ CH ₅ ) residues to -OH groups in the mixture was approximately 3: 1. 0.25 percent by weight of stannous octoate was then added to this mixture, and the resulting mixture was poured into a square Porm bia to a depth of 1.6 mm (1/16 ") and allowed to stand at room temperature (22 ^° C.; 65% relative After 45 minutes the mass had hardened to form an elastic material. The physical properties after standing for 24 hours were as follows:

TS EHT

28.1 kg / cm ² 170 fi 38 ° 0.7 kg

(400 lb / sq.in.) (1.6 Ib.)

Example 2

A mixture was prepared as in Example 1 except that an additional 3 _f 0 g of a polydimethylsiloxane incorporated wurueri that durchschnl t ti i.uh about 15 Dlmethylsiloxan-ELnhelten per molecule and endrUäruiige

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-Si- (OCH ₂ CH ₂ CH,), - groups

unleaded. The ratio of the - (OCH ₂ CH ₂ OH,) - radicals to the OH groups in this mixture was approximately 10: 1. The mixture was catalytically activated by adding 0.25 percent by weight of stannous octoate and the mass of the catalyst added to the ambient atmosphere in a mold about 1.6 mm (1/16 ") deep. The mass cured to a chewy solid in about half an hour, and after 24 hours the rubber exhibited the following physical properties:

TS E H T

36.6 kg / cm ² 140 # 50 ° 1.1 kg (520 lb / sq.in.) (2.4 Ib.)

Example 3

50 g of each of the organosilicon films that used in Example 1, 'were on a Three-roll grinder together with 3.0 g of a polydime thylsiloxane, which has an average of about 15 dimethylsiloxy units contained per molecule and through

-Si (OCH ₂ CH ₂ CH,), - groups

was closed at the end, furthermore with 80 g "Minusil" (5 / u) and 20 g of diatomaceous earth, which contained 0.4 g of added water dispersed therein, intimately mixed.

Was this mixture catalytically activated by adding 0.4 percent by weight of dibutyltin dilaurate and the

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1 09839/1297

Exposed to room atmosphere (23 ⁰ O; 65 # relative humidity), it solidified after about an hour to an elastic pesticide. After 24 hours of exposure, the rubber exhibited the following physical properties:

TS EHT

28.1 kg / cm ² 13056 45 ° 1.2 kg (400 Ib./sq.in.) (2.6 Ib.)

The mass activated with the catalyst took the chew-like material Properties quickly, both when exposed in a thin layer, as well as when it was exposed in the form of thick masses.

Example 4

50 g of a polydimethylsiloxane having terminal hydroxyl groups (viscosity 2000 Gentistokes at 25 ⁰ O), 50 g of a polydimethylsiloxane, which by groups of the formula

-O-Si (OCH ₂ CH ₂ CH ₃ ) ₃

was closed at the end and had a viscosity of 2000 Centistokes at 25 ⁰ C, 100 g of a ground silicon dioxide with an average particle size of 5 / U and 3.0 g of a PolydimethylBiloxans, which on average about 15 dimethylsiloxane units per molecule and terminal groups of the formula

-OSi (OCH ₂ CH ₂ CH,), Λπ became one! stayed iclüin. aU ;: ^; .-; .-? ^ ^ n

1 0 9 8 3 i> / 12 9 7 ^: "'

Rubber kneader mixed together. Thereafter, this mixture 10 was g by trimethylsiloxy groups terminally sealed polymethyl hydrogen siloxane added, which had a viscosity of about 40 centistokes at 25 ⁰ C, and at the same time was added 30 g of a liquid, terminal silanol-containing polysiloxane having an average of about 15 Containing dimethylsiloxane units per molecule, added.

If the mixture obtained in this way was catalytically activated by adding 5 percent by weight of stannous octoate, so it expanded rapidly and solidified into a foamed silicone rubber within about three minutes.

Example 5

100 g of a dimethyl polysiloxane terminated by silanol groups, which had a viscosity of 2000 centistokes at 25 ⁰ C, was on a three-roll rubber grinder with 100 g of ground silicon dioxide, the average particle size of which was 5 / U, and 10 parts by weight of a dimethyl polysiloxane, the one Viscosity of 40 centistokes at 25 ⁰ C and terminal

-Si (OCH ₂ CH ₂ CH,) »groups

contained, intimately mixed. The propoxy content of the last-mentioned polydimethylsiloxane was approximately 30 percent by weight, and the ratio of the silicon-bonded propoxy groups to the silicon-bonded hydroxyl groups in this mass was 10 t 1.

Thereafter, 0.27 g of stannous oil were intimately dispersed in the mixture, and the resulting mass was In a

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square shape was filled up to a length of 1.6 mm (1/16 ") and left to stand in the room atmosphere (22 ⁰ G; 50 $ relative humidity). After 24 hours, the mass had solidified into a solid rubber, the one

Had a tensile strength of 41.5 kg / cm (590 p.s.i.) and an elongation at break of $ 120.

Example 6

56 g of the terminal silanol group-containing dimethylpolysiloxane and 30 g of the terminal -Si (OCH ₂ CH ₂ CH ₅ U-containing dimethyl polysiloxane, which were used in Example 5, were intimately mixed on a three-roller rubber grinder with 100 g of a ground quartz -Filler, the particle size of which was 5 microns, and 44 g of a dimethylpolysiloxane, which had a viscosity of 2000 centistokes at 25 ⁰ C and in which about 12 $ of the total end groups consisted of (GE,), SiO .. / ₂ units, while the remaining units that terminate the polysiloxane consisted of those of the formula (CH,) ₂ (OH) SiO.j / _2. The ratio of the silicon-bonded alkoxy groups to the silicon-bonded hydroxyl groups in the composition thus obtained was 30:

This mass was then catalytic by mixing in 0.4 percent by weight of dibutyltin dilaurate, based on the total weight of the organopolysiloxanes; activated and the mixture poured into a square mold to a depth of 1.6 mm (1/16 ") and left at room temperature (22 °); the relative humidity was about 60 $.

After 24 hours, the mixture was ER- to a rubber

stares, which has a tensile strength of 21.1 kg / cm (300 pei)

\ and had a gross income of $ 150. After 7 days

sad the rubber has a tensile strength of 28.1 kg / cm (400 p.s.i ·) and an elongation at break of $ 90.

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Claims (7)

Claims 1. Process for the production of an elastomer-forming Composition by forming a mixture of (a) one containing silicon-bonded alkoxy groups Silicon material, (b) a terminal, silicon-bonded hydroxyl group-containing polydiorganosiloxane and (c) a condensation catalyst, characterized in that the silicon material (a) consists of at least one polydiorganosiloxane in which the organic radicals are monovalent hydrocarbon groups, halogenated monovalent hydrocarbon groups or cyanoalkyl groups and which terminal. Groups of the general formula -SiR « _a (OR ') ₃ _ _a in which a is 0 or 1, R "is a monovalent hydrocarbon radical or a monovalent halogenated hydrocarbon radical and R * is an alkyl group containing fewer than 7 carbon atoms, while the polydiorganosiloxane (b) has a viscosity of at least 200 centistokes at 25 ⁰ C and the ratio of the total number of -OR ¹ radicals introduced into the mixture by component (a) to the total number of hydroxyl groups introduced by component (b), 1: 1 to 35: 1 amounts to. 2. The method according to claim "!, characterized in that the polydiorganosiloxane component (a) consists of two or more different polydiorganosiloxanes which have different molecular weights and / or viscosity. 3. The method according to claims 1 or 2, characterized in that 109839/1297 - 19 - indicates that the ratio of the number of -OR'r radicals introduced by component (a) to the number of hydroxyl groups introduced by component (b), 5: 1 to 15: 1. 4. The method according to any one of the preceding claims, characterized in that the condensation catalyst consists of an organic tin compound. 5. The method according to any one of the preceding claims, characterized in that the elastomer-forming In addition, an organopolysiloxane containing silicon-bonded hydrogen atoms and a mass hydroxylated organic or organosilicon material be incorporated. 6. The method according to any one of the preceding claims, characterized in that forming in the elastomers Mass of up to 1 percent by weight of water, based on the total weight of components (a) and (b), introduced will. 7. The method according to any one of the preceding claims, characterized in that forming the elastomers Deformed to the desired shape and then allowed to cure to an elastomer. 109839/1297