Low modulus room temperature vulcanizable silicone rubber compositions

Claim 2

A low modulus room temperature vulcanizable silicone rubber composition comprising: (A) 100 parts by weight of a silanol terminated diorganopolysiloxane polymer having a viscosity ranging from 50,000 centipoise to 350,000 centipoise at 25° C. and where the organo groups are monovalent hydrocarbon radicals; and (B) 1 to 20 parts by weight of a catalyst mixture per 100 parts by weight of (A), said catalyst mixture comprising: (1) 60 to 100 parts by weight of an acyloxy functional silane of the formula R--Si--(OCOR.sup.1).sub.3 where R and R 1 are monovalent hydrocarbon radicals and (2) a co-catalyst comprising: (a) 0.1 to 5 parts by weight of an alkyl tin salt of a carboxylic acid and (b) 0.001 to 0.4 parts by weight of a zinc salt of a carboxylic acid, a zirconium salt of a carboxylic acid or mixture thereof.

Claim 3

The composition of claim 1 wherein ingredient (A) further comprises 5 to 100 parts by weight of a filler.

Claim 4

The composition of claim 2 wherein the filler is selected from the class consisting of fumed silica and precipitated silica.

Claim 5

The composition of claim 2 wherein the filler is selected from the class consisting of titanium dioxide, zirconium silicate, silica aerogel, iron oxide, diatomaceous earth, glass fibers, polyvinyl chloride, ground quartz, lithopone, zinc oxide, calcium carbonate, magnesium oxide, chromic oxide, zirconium oxide, aluminum oxide, alpha quartz, calcined clay, carbon, graphite, cotton and synthetic fibers.

Claim 6

The composition of claim 2 wherein the filler is treated with a cyclotetrapolysiloxane.

Claim 7

The composition of claim 1 wherein ingredient (A) further comprises 1 to 50 parts by weight of a plasticizer.

Claim 8

The composition of claim 6 wherein the plasticizer is a diorganopolysiloxane having a viscosity ranging from 10 to 5000 centipoise at 25° C.

Claim 9

The composition of claim 7 wherein the plasticizer is dimethylpolysiloxane.

Claim 10

The composition of claim 1 wherein ingredient (A) further comprises 1 to 25 parts by weight of a chainstopping fluid having (R 3 ) 2 SiO units, (R 3 ) 3 SiO 0 .5 units and R 3 SiO 1 .5 units, where the ratio of organosiloxy units to diorganosiloxy units varies from approximately 0.11 to 1.4 and the ratio of triorganosiloxy units to diorganosiloxy units varies from about 0.02 to 1.0, and where R 3 is a monovalent hydrocarbon radical.

Claim 11

The composition of claim 1 wherein ingredient (B) further comprises 5 to 40 parts by weight of an adhesion promoter.

Claim 12

The composition of claim 10 wherein the adhesion promoter is a ditertiaryalkoxydiacyloxy functional silane.

Claim 13

The composition of claim 11 wherein the adhesion promoter is ditertiarybutoxydiacetoxysilane.

Claim 14

The composition of claim 1 wherein the tin salt is dibutyltindilaurate.

Claim 15

The composition of claim 1 wherein the tin salt alkyl portion is methyl and the carboxylic acid portion has from 2 to 22 carbon atoms.

Claim 16

The composition of claim 14 wherein the tin salt is dimethyl tin neodecanoate.

Claim 17

The composition of claim 1 wherein the zinc salt is zinc octoate.

Claim 18

The composition of claim 1 wherein the zirconium salt is zirconium octoate.

Claim 19

A process for forming a low modulus room temperature vulcanizable silicone rubber composition comprising the steps of: (a) mixing: (A) 100 parts by weight of a silanol terminated diorganopolysiloxane polymer having a viscosity ranging from 50,000 centipoise to 350,000 centipoise at 25° C. and where the organo groups are monovalent hydrocarbon radicals; and (B) 1 to 20 parts by weight of a catalyst mixture per 100 parts by weight of (A), said catalyst mixture comprising (1) 60 to 100 parts by weight of an acyloxy functional silane of the formula R--Si(OCOR.sup.1).sub.3 where R and R 1 are monovalent hydrocarbon radicals and (2) a co-catalyst comprising: (a) 0.1 to 5 parts by weight of an alkyl tin salt of a carboxylic acid and (b) 0.001 to 0.4 parts by weight of a zinc salt of a carboxylic acid, a zirconium salt of a carboxylic acid, or mixtures thereof. (b) curing the mixture in the presence of atmospheric moisture.

Claim 20

A process for forming a low modulus room temperature vulcanizable silicone rubber composition comprising the steps of: (a) mixing: (A) 100 parts by weight of a silanol terminated diorganopolysiloxane polymer having a viscosity ranging from 50,000 centipoise to 350,000 centipoise at 25° C. and where the organo groups are monovalent hydrocarbon radicals; and (B) 1 to 20 parts by weight of a catalyst mixture per 100 parts by weight of (A), said catalyst mixture comprising (1) 60 to 100 parts by weight of an acyloxy functional silane of the formula R--Si(OCOR.sup.1).sub.3 where R and R 1 are monovalent hydrocarbon radicals and (2) a co-catalyst comprising: (a) 0.1 to 5 parts by weight of an alkyl tin salt of a carboxylic acid and (b) 0.001 to 0.4 parts by weight of a zinc salt of a carboxylic acid, a zirconium salt of a carboxylic acid, or mixtures thereof. (b) curing the mixture in the presence of atmospheric moisture.

Claim 21

The process of claim 18 wherein ingredient (A) further comprises 5 to 100 parts by weight of a filler.

Claim 22

The process of claim 19 wherein the filler is selected from the class consisting of fumed silica and precipitated silica.

Claim 23

The process of claim 19 wherein the filler is selected from the class consisting of titanium dioxide, zirconium silicate, silica aerogel, iron oxide, diatomaceous earth, glass fibers, polyvinyl chloride, ground quartz, lithopone, zinc oxide, calcium carbonate, magnesium oxide, chromic oxide, zirconium oxide, aluminum oxide, alpha quartz, calcined clay, carbon, graphite, cotton and synthetic fibers.

Claim 24

The process of claim 19 wherein the filler is treated with a cyclotetrapolysiloxane.

Claim 25

The process of claim 18 wherein ingredient (A) further comprises 1 to 50 parts by weight of a plasticizer.

Claim 26

The process of claim 23 wherein the plasticizer is a diorganopolysiloxane having a viscosity ranging from 10 to 5000 centipoise at 25° C.

Claim 27

The process of claim 24 wherein the plasticizer is dimethylpolysiloxane.

Claim 28

The process of claim 18 wherein ingredient (A) further comprises 1 to 25 parts by weight of a chainstopping fluid having (R 3 ) 2 SiO units, (R 3 ) 3 SiO 0 .5 units R 3 SiO 1 .5 units, where the ratio of organosiloxy units to diorganosiloxy units varies from approximately 0.11 to 1.4 and the ratio of triorganosiloxy units to diorganosiloxy units varies from about 0.02 to 1.0, and where R 3 is a monovalent hydrocarbon radical.

Claim 29

The process of claim 18 wherein ingredient (B) further comprises 5 to 40 parts by weight of an adhesion promoter.

Claim 30

The process of claim 27 wherein the adhesion promoter is a ditertiaryalkoxydiacyloxy functional silane.

Claim 31

The process of claim 28 wherein the adhesion promoter is ditertiarybutoxydiacetoxysilane.

Claim 32

The process of claim 18 wherein the tin salt is dibutyltindilaurate.

Claim 33

The process of claim 18 wherein the tin salt alkyl portion is methyl and the carboxylic acid portion has 2 to 22 carbon atoms.

Claim 34

The process of claim 31 wherein the tin salt is dimethyltinneodecanoate.

Claim 35

The process of claim 18 wherein the zinc salt is zinc octoate.

Claim 36

The process of claim 18 wherein the zirconium salt is zirconium octoate.