Fluorosilicone rubber composition, process and polymer
First Claim
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1. In a solvent resistant room temperature vulcanizable silicone rubber composition comprising(A) a mixture composed of(i) a vinyl-terminated base polymer, said base polymer being prepared by copolymerization of methyl-3,3,3-trifluoropropylsiloxane cyclic trimer and octamethylcyclotetrasiloxane, and the viscosity of said base polymer varies from 1,000 to 200,000 centipoise at 25°
- C., and(ii) a platinum catalyst, and(B) alone, or in admixture with base polymer (i),(iii) a cross-linking polymer selected from(a) a resin having ##STR10## and SiO2 units where the R to Si ratio varies from 1.0 to 2.7;
(b) a resin having ##STR11## units, SiO2 units and RR3 SiO units where the R to Si ratio varies from 1.2 to 2.7;
(c) a polymer of the formula;
##STR12## where R is alkyl of from 1 to 8 carbon atoms or phenyl, R1 is perfluoroalkyl of from 1 to 8 carbon atoms, s is at least 1, t and z may be zero or a positive integer and the viscosity or the polymer varies from 10 to 1,000 centipoise at 25°
C., where the concentration of siloxy units taken t times varies from 0 to 75 mole percent, and R3 is alkyl of 1 to 8 carbon atoms, or --CH2 CH2 R1 ;
or a mixture of (a), (b) and (c), the total composition (A) and (B) comprising per 100 parts by weight of a base polymer (i), from 0.1 to 50 parts per million of platinum catalyst (ii), and from 1 to 50 parts of cross-linking polymer (iii), the improvement wherein the cyclic trimer used in the preparation of said base polymer (i) contains no more than 1.0 weight percent of a difluoropropenyl-containing compound of the formula ##STR13##
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Abstract
High strength solvent resistant rubber compositions comprise a vinyl terminated fluorosilicone copolymer gum having a controlled, low amount of backbone vinyl unsaturation, a conventional platinum curing agent, and a crosslinker containing a least two Si-H bonds.
52 Citations
12 Claims
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1. In a solvent resistant room temperature vulcanizable silicone rubber composition comprising
(A) a mixture composed of (i) a vinyl-terminated base polymer, said base polymer being prepared by copolymerization of methyl-3,3,3-trifluoropropylsiloxane cyclic trimer and octamethylcyclotetrasiloxane, and the viscosity of said base polymer varies from 1,000 to 200,000 centipoise at 25° - C., and
(ii) a platinum catalyst, and (B) alone, or in admixture with base polymer (i), (iii) a cross-linking polymer selected from (a) a resin having ##STR10## and SiO2 units where the R to Si ratio varies from 1.0 to 2.7;
(b) a resin having ##STR11## units, SiO2 units and RR3 SiO units where the R to Si ratio varies from 1.2 to 2.7;
(c) a polymer of the formula;
##STR12## where R is alkyl of from 1 to 8 carbon atoms or phenyl, R1 is perfluoroalkyl of from 1 to 8 carbon atoms, s is at least 1, t and z may be zero or a positive integer and the viscosity or the polymer varies from 10 to 1,000 centipoise at 25°
C., where the concentration of siloxy units taken t times varies from 0 to 75 mole percent, and R3 is alkyl of 1 to 8 carbon atoms, or --CH2 CH2 R1 ;
or a mixture of (a), (b) and (c), the total composition (A) and (B) comprising per 100 parts by weight of a base polymer (i), from 0.1 to 50 parts per million of platinum catalyst (ii), and from 1 to 50 parts of cross-linking polymer (iii), the improvement wherein the cyclic trimer used in the preparation of said base polymer (i) contains no more than 1.0 weight percent of a difluoropropenyl-containing compound of the formula ##STR13## - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
- C., and
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12. In a vinyl-terminated polymer prepared by copolymerization of methyl-3,3,3-trifluoropropyl-siloxane cyclic trimer and octamethylcyclotetrasiloxane, said polymer having a viscosity of from 1,000 to 200,000 centipoise at 25°
- C., the improvement wherein the cyclic trimer used in preparation of said polymer contains no more than 1.0 weight percent of a difluoropropenyl-containing compound of the formula ##STR14##
Specification