Room temperature vulcanizable silicone rubber composition

Claim 2

A ROOM TEMPERATURE VULCANIZABLE SILICONE RUBBER COMPOSITION WITH THERMAL STABILITY, LOW SHRINKAGE UPON CURE AND A LONG WORK-LIFE COMPRISING: A. A LINEAR FLUID ORGANOPOLYSILOXANE CONTAINING TERMAL SILICON-BONDED HYDROXY GROUPS AND HAVING A VICOSITY OF 100 TO 10,000,000 CENTIPOISE AT 25*C, THE ORGANIC GROUPS OF THE AFOREMENTIONED ORGANOPOLYSILOXANE REPRESENTING MONOVALENT HYDROCARBON RADICALS, B. 100 AND 350% BY WEIGHT OF SAID LINEAR ORGANOPOLYSILOXANE OF AN EXTENDING FILLER, C. FROM 1 TO 30% BY WEIGHT OF AN ALKIL SILICATE BASED ON SAID LINEAR ORGANOPOLYSILOXANE SELECTED FROM THE CLASS CONSISTING OF (1) A MONOMERIC ORGANOSILICATE CORRESPONDING TO THE GENRAL FORMULA,

Claim 3

The composition of claim 1 wherein the extending filler is selected from the class consisting of titanium dioxide, lithopone, zinc oxide, zirconium silicate, crushed quartz, silica aerogel, iron oxide, diathomaceous earth, calcium carbonate, glass fibers, magnesium oxide, zirconium oxide, aluminum oxide, calcined clay, asbestos, carbon, graphite, cotton fibers and synthetic fibers.

Claim 4

The composition of claim 1 wherein there is present 90 to 9000 parts per million of free water in the composition so as to facilitate deep section cure in the composition.

Claim 5

The composition of claim 1 further comprising having in the composition from 20 to 100% by weight of said linear organopolysiloxane of a silicone dispersing agent of the formula,

Claim 6

The composition of claim 1 wherein there is utilized a concentration of 5 to 30% by weight of said partial hydrolysis product of the monomeric organosilicate compound.

Claim 7

The composition of claim 1 wherein linear organopolysiloxane has the formula,

Claim 8

The composition of claim 1 wherein R4 and R5 are selected from the class consisting of alkyl radicals and aryl radicals of up to 8 carbon atoms.

Claim 9

The composition of claim 1 wherein the liquid partial hydrolysis product of the organosilicate monomeric compound is polyethyl silicate which is present at a concentration of 5 to 30% by weight.

Claim 10

The composition of claim 1 wherein R3 is selected from the class consisting of alkyl radicals of 1 to 8 carbon atoms, cycloalkyl radicals, phenyl radicals and vinyl radicals.

Claim 11

The composition of claim 1 wherein R4 and R5 are independently selected from the class consisting of alkyl radicals of 1 to 8 carbon atoms, cycloalkyl radicals of 4 to 6 carbon atoms, phenyl and vinyl radicals.

Claim 12

The composition of claim 1 wherein the R7 radicals of the linear organopolysiloxane are selected from the class consisting of alkyl radicals of 1 to 8 carbon atoms, cycloalkyl radicals, phenyl radicals and vinyl radicals.

Claim 13

A process for preparing a room temperature vulcanizable silicone rubber composition which composition has been cured to an elastomer, has thermal stability, low shrinkage upon cure, and a long work life comprising: a. mixing a linear organopolysiloxane containinG terminal silicon-bonded hydroxy groups and having a viscosity of 1000 to 10,000,000 centipoise at 25*C, the organic groups of the aforementioned organopolysiloxanes representing monovalent hydrocarbon radicals; b. from 100 to 350% by weight of said linear organopolysiloxane of an extending filler; c. from 1 to 30% by weight of an alkyl silicate based on said linear organopolysiloxane selected from the class consisting of (1) a monomeric organosilicate corresponding to the general formula, (R''0)3 SiR'''' where R'' is a radical selected from the class consisting of monovalent hydrocarbon radicals and halogenated monovalent hydrocarbon radicals and R'''' is selected from the class consisting of alkyl, haloalkyl, aryl, haloaryl, alkenyl, cycloalkyl, alkoxy, and aryloxy radicals, and (2) a liquid partial hydrolysis product of the aforementioned organosilicate monomeric compound; d. from 0.5 to 6% by weight based on said linear organopolysiloxane of a work-life extending additive of the formula,

Claim 14

A process for preparing a room temperature vulcanizable silicone rubber composition which composition has been cured to an elastomer, has thermal stability, low shrinkage upon cure, and a long work life comprising: a. mixing a linear organopolysiloxane containinG terminal silicon-bonded hydroxy groups and having a viscosity of 1000 to 10,000,000 centipoise at 25*C, the organic groups of the aforementioned organopolysiloxanes representing monovalent hydrocarbon radicals; b. from 100 to 350% by weight of said linear organopolysiloxane of an extending filler; c. from 1 to 30% by weight of an alkyl silicate based on said linear organopolysiloxane selected from the class consisting of (1) a monomeric organosilicate corresponding to the general formula, (R''0)3 SiR'''' where R'' is a radical selected from the class consisting of monovalent hydrocarbon radicals and halogenated monovalent hydrocarbon radicals and R'''' is selected from the class consisting of alkyl, haloalkyl, aryl, haloaryl, alkenyl, cycloalkyl, alkoxy, and aryloxy radicals, and (2) a liquid partial hydrolysis product of the aforementioned organosilicate monomeric compound; d. from 0.5 to 6% by weight based on said linear organopolysiloxane of a work-life extending additive of the formula,

Claim 15

The process of claim 12 wherein in step (a) the extending filler is selected from the class consisting of titanium dioxide, lithopone, zinc oxide, zirconium silicate, crushed quartz, silica aerogel, iron oxide, diatomaceous earh, calcium carbonate, glass fibers, magnesium oxide, zirconium oxide, aluminum oxide, calcined clay, asbestos, carbon, graphite, cotton fibers and synthetic fibers.

Claim 16

The process of claim 12 wherein in step (a) there is also mixed into the ingredients of from 90 to 3000 parts per million of free water.

Claim 17

The process of claim 12 where there is also mixed into the ingredients in step (a) from 20% to 100% by weight of said linear organopolysiloxane of a silicone dispersing agent of the formula,

Claim 18

The process of claim 12 wherein there is utilized in step (a) a concentration of 5 to 30% by weight of said partial hydrolysis product of the monomeric organosilicate compound.

Claim 19

The process of claim 12 wherein the linear organopolysiloxane has the formula,