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US 5,859,094 AGranted
Use of high molecular weight organopolysiloxanes to improve physical properties of liquid silicone rubber compositions
AssigneeDow Corning Corporation
InventorsLori Jean Conway, Phillip Joseph Griffith, Jary David Jensen, Peter Lamont
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Abstract
A platinum group-metal curing liquid silicone rubber compositions having improved physical properties such as tear and heat-aging, especially at durometers below about 35 and above about 65. The present inventors have unexpectedly discovered that the addition of diorganohydrogensiloxy end-blocked polydiorganosiloxanes and triorganosiloxy end-blocked polydiorganosiloxanes having a viscosity greater than about 10 Pa.cndot.s at 25.degree. C. to liquid silicone rubber compositions can provide for the described improved properties.
Claims29
A platinum group-metal curing liquid silicon rubber composition comprising:
- (A) 35 to 75 weight percent, based on the weight of the composition, of a diorganoalkenylsiloxy end-blocked polydiorganosiloxane having a viscosity within a range of about 20 Pa.cndot.s to 200 Pa.cndot.s at 25.degree. C. and containing essentially no ethylenically unsaturated hydrocarbon radicals bonded to non-terminal silicon atoms,
- (B) 0 to 30 weight percent, based on the weight of the composition of a diorganoalkenylsiloxy end-blocked polydiorganosiloxane having a viscosity within a range of about 0.1 Pa.cndot.s to 200 Pa.cndot.s at 25.degree. C., where from 1 to about 5 percent of the non-terminal repeating units of the diorganoalkenylsiloxy end-blocked polydiorganosiloxane comprise an alkenyl radical,
- (C) 1 to 30 weight percent, based on the weight of the composition, of a polydiorganosiloxane described by formula
- R.sup.1.sub.2 R.sup.2 SiO(R.sup.1 R.sup.2 SiO).sub.x OSiR.sub.1.sub.2 R.sup.2,
- where each R.sup.1 is independently selected from a group consisting of saturated monovalent hydrocarbon radicals and aryl radicals, each R.sup.2 is independently selected from a group consisting of hydrogen, R.sup.1, and alkenyl radicals with the proviso that R.sup.2 comprise no more than one alkenyl radical per polydiorganosiloxane molecule and x is a value such that the polydiorganosiloxane has a viscosity greater than about 10 Pa.cndot.s at 25.degree. C.,
- (D) 5 to 40 weight percent, based on the weight of the composition, of a treated reinforcing silica filler,
- (E) an amount sufficient to cure the composition of an organohydrogensiloxane crosslinker, and
- (F) a platinum group-metal containing catalyst in an amount sufficient to effect curing of the composition.
5 more elements
A platinum curing liquid silicon rubber composition comprising:
- (A) 50 to 60 weight percent, based on the weight of the composition, of a dimethylvinylsiloxy end-blocked polydimethylsiloxane having a viscosity within a range of about 40 Pa.cndot.s to 70 Pa.cndot.s at 25.degree. C. and containing essentially no ethylenically unsaturated hydrocarbon radicals bonded to non-terminal silicon atoms,
- (B) 5 to 15 weight percent, based on the weight of the composition, of a dimethylvinylsiloxy end-blocked polydimethyl(methylvinyl)siloxane having a viscosity within a range of about 0.1 Pa.cndot.s to 20 Pa.cndot.s at 25.degree. C., where from 1 to about 5 percent of the non-terminal repeating units of the dimethylvinylsiloxy end-blocked polydimethyl(methylvinyl)siloxane comprise a vinyl radical,
- (C) 10 to 20 weight percent, based on the weight of the composition, of a polydiorganosiloxane selected from the group consisting of trimethylsiloxy end-blocked polydimethylsiloxane and dimethylhydrogensiloxy end-blocked polydimethylsiloxane where the polydiorganosiloxane has a viscosity within a range of about 60 Pa.cndot.s to 1000 Pa.cndot.s at 25.degree. C.,
- (D) 10 to 30 weight percent, based on the weight of the composition, of a treated reinforcing silica filler having a BET surface area within a range of about 200 m.sup.2 /g to 500 m.sup.2 /g.
- (E) an organohydrogensiloxane crosslinker providing a ratio of silicon-bonded hydrogen atoms to vinyl substituents of components (A) and (B) within a range of about 1.7:1 to 2:1.
- (F) a neutralized reaction product of chloroplatinic acid and sym-tetramethyldivinyldisiloxane providing about 1 ppm to 10,000 ppm platinum.
3 more elements
Dependencies are inferred from the claim text.