Claims
- 1. In an improved liquid silicone rubber composition comprising the product obtained by blending to homogeniety
- (A) an organopolysiloxane containing at least 2 silicon-bonded alkenyl radicals in each molecule and having a viscosity of from 100 to 300,000 centipoise (0.1-300 Pa.s) at 25.degree. C.
- (B) a microparticulate hydrophilic silica, and
- (C) an amount of a platinum-alkenylsiloxane complex sufficient to promote curing of said composition in the presence of an organohydrogensiloxane,
- the improvement characterized by the pK.sub.a value exhibited by a dispersion in a nonpolar solvent of 100 parts by weight of said silica and from 10 to 100 weight parts of said complex as atomic platinum, where said value is within the range of from 2.0 to 9.0, inclusive.
- 2. A composition according to claim 1 where said silica is produced by the reaction of water glass with acid.
- 3. A composition according to claim 1 where said alkenylsiloxane is a divinyltetramethyldisiloxane.
- 4. A composition according to claim 3 where said alkenylsiloxane is a symmetrical divinyltetraalkyldisiloxane.
- 5. A composition according to claim 4 where said alkenylsiloxane is sym-tetramethyldivinyldisiloxane.
- 6. A composition according to claim 1 where said nonpolar solvent is an aromatic hydrocarbon.
- 7. A composition according to claim 6 where said aromatic hydrocarbon is benzene.
- 8. A composition according to claim 1 where the pK.sub.a value of the silica is adjusted by treating it with a basic material selected from the group consisting of an alkali metal, an alkaline earth metal, an alkali metal hydroxide, an alkali metal silanolate, an alkali metal alcoholate, an alkaline earth metal hydroxide, an alkaline earth metal silanolate, and a calcium salt of a higher aliphatic carboxylic acid.
- 9. A composition according to claim 8 where the silica treating agent is sodium hydroxide or calcium stearate.
- 10. A composition according to claim 1 where said organopolysiloxane is a diorganovinylsiloxy-terminated diorganopolysiloxane exhibiting a viscosity of from 300 to 100,000 centipoise.
- 11. A composition according to claim 10 where said diorganovinylsiloxy-terminated diorganopolysiloxane is a dimethylvinylsiloxy-terminated dimethylpolysiloxane.
Priority Claims (1)
Number |
Date |
Country |
Kind |
61-221189 |
Sep 1986 |
JPX |
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REFERENCE TO COPENDING APPLICATIONS
This application is a continuation-in-part of copending application Ser. No.056.821. filed on June 2, 1987.
US Referenced Citations (3)
Number |
Name |
Date |
Kind |
4500584 |
Modic |
Feb 1985 |
|
4585848 |
Evans et al. |
Apr 1986 |
|
4608395 |
Hamada et al. |
Aug 1986 |
|
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
56821 |
Jun 1987 |
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