Patent GB-1474096-A (GB)
Title: Vulcanizable systems
IPC: C08L83/04
Filed: 1974-05-09
Abstract: 1474096 Silicone rubber compositions GENERAL ELECTRIC CO 9 May 1974 [9 Aug 1973] 20487/74 Heading C3T A two-part RTV silicone rubber composition comprises, when mixed, (a) a linear, fluid OH- terminated organopolysiloxane having a viscosity of 500 to 10,000,000 c.p. at 25 C., the organo groups being monovalent hydrocarbon, halohydrocarbon or cyanoalkyl radicals; (b) a filler, preferably in an amount of from 5-300% wt. of (a); (c) from 0À1 to 15% wt. of (a) of (1) an organosilicate of the formula (R<SP>40</SP>O) 3 SiR<SP>41</SP> where R<SP>40</SP> is a monovalent hydrocarbon, halohydrocarbon or cyanoalkyl radical, and R<SP>41</SP> is an alkyl, haloalkyl, aryl, alkaryl, aralkyl, haloaryl, alkenyl, cycloalkyl, cycloalkenyl, cyanoalkyl, alkoxy, aryloxy or acyloxy radical or a liquid partial hydrolysate of the said organosilicate; or (2) an organopolysiloxane resin having a functionality greater than 2; or (3) an organohydrogenpolysiloxane of the formula R<SP>43</SP> a HSiO (3-a)/2  where R<SP>43</SP> is alkyl or aryl and a is a number less than 2 but not zero; (d) from 0À1 to 5% wt. of (a) of a catalyst which is the reaction product of an organotin oxide of the formula R<SP>11</SP>R<SP>111</SP>SnO, where R<SP>11</SP> and R<SP>111</SP> are monovalent hydrocarbon radicals, preferably alkyl or aryl, with an oxygen-containing acid having at least one oxygen atom in the acid radical attached to a replaceable acid hydrogen atom such acids being mono- or dicarboxylic acids or an inorganic acid having at least one oxygen atom as defined above, the composition being mixed from one part comprising component (a) and another part comprising component (c). The compositions may also include 0À1-10% wt. of (a) of a self-bonding additive which is a nitrogen functional silane of the formula # (3-a) Si(R) a # where R is a monovalent hydrocarbon or halohydrocarbon radical, # is a hydrolysable alkoxy, phenoxy or dialkylamino group, and 0 is a saturated, aliphatically unsaturated or aromatic nitrogenfunctional hydrocarbon residue functionalized by an amino, cyano, oxo or ester, and a=0-2. Suitable fillers are TiO 2 , lithopone, ZnO, zirconium silicate, silica aerogel, iron oxide, diatomaceous earth, CaCO 3 , fumed silica, precipitated silica, glass fibres, MgO, chromic oxide, zirconium oxide, aluminium oxide, crushed quartz, calcined clay, asbestos, carbon, cork, graphite, cotton or synthetic fibres. Component (a) is preferably a diorganopolysiloxane having 250-7275 repeating units. Component (c) is preferably partially hydrolysed ethyl silicate. Suitable nitrogen-functional silanes are those of the formula where R<SP>1</SP> is a monovalent hydrocarbon or halohydrocarbon radical of up to 10 C atoms, R<SP>12</SP>- R<SP>16</SP> are H, alkyl or aryl radicals of up to 10 C atoms, M is SO 2  or C=O, h=3-20; or those of the formula where R<SP>31</SP> is a monovalent hydrocarbon or halohydrocarbon radical, R<SP>16</SP>, R<SP>12</SP> and R<SP>13</SP> are H, alkyl or aryl radicals of up to 10 carbon atoms, M is SO 2  or C = O and h=3-20; or those of the formula where R<SP>2</SP> and R<SP>6</SP> are H, alkyl or aryl radicals of up to 10 carbon atoms, B is N, S or O, G is or -N(R<SP>7</SP>) 2  where R<SP>7</SP>#R<SP>2</SP>, c and n=1-10, t=0 or 1, v=1-5; or those of the formula L 3-a Si(R) a [(CH 2 ) n OCOCHR<SP>51</SP>-CHR<SP>51</SP>-NR<SP>3</SP>R<SP>4</SP>] where L is R<SP>1</SP> 2 N- or R<SP>1</SP>O, R<SP>51</SP> is H, alkyl or aryl of up to 10 carbon atoms, R<SP>3</SP> and R<SP>4</SP> are H, alkyl, aryl, -R<SP>5</SP>NR<SP>3</SP>R<SP>4</SP>, -R<SP>5</SP>OH, -R<SP>5</SP>-S-R<SP>1</SP>, -R<SP>5</SP>COR<SP>1</SP>, -R<SP>5</SP>CN, or -R<SP>5</SP>OR<SP>1</SP> where R<SP>5</SP> = an alkylene or arylene radical of up to 10 carbon atoms, n=1-20; or those of the formula where R<SP>9</SP>-R<SP>11</SP> are H, alkyl or aryl radicals or up to 10 carbon atoms, j=3-20, w=1-500 and A is H, alkyl, aryl or radical; or those of the formula  where R<SP>12</SP>, R<SP>13</SP> are H, alkyl or aryl radicals of up to 10 carbon atoms, z=2-20. Numerous other nitrogen-functional silanes are described. The composition may also comprise organic solvents. In Example 1 a base polymer solution comprising OH-terminated dimethylpolysiloxane oil (5000 cP), silica, hydrogenated castor oil, titanium dioxide, colour pigment, ceramic black and mineral spirits is mixed with a catalyst composition comprising the reaction product of dibutyltin oxide and either dimethylphthalate or dimethyl maleate, ethyl silicate 40, xylene and any one of the following silanes: and cured at room temperature. Other examples are described.