Back to results
US 4,066,603 AGranted
Sulfur containing silicone elastomer and method of preparation
AssigneeDow Corning Corporation
InventorsGary R. Homan, Chi-Long Lee
Life of this patent
Estimating the term…
Abstract
Mixing a polydimethylsiloxane having terminal vinyl groups or silacyclopentenyl groups, a mercaptoorganopolysiloxane and an organic peroxide provides a composition which cures to an elastomer at room temperature or by heating. The elastomers are useful as sealants and rubber articles.
Claims19
A composition curable to an elastomer comprising a material prepared by mixing
- A. 5 to 95 weight percent based on the combined weight of (A) and (B) of a polydimethylsiloxane having a viscosity of at least 0.3 Pa.sup.. s at 25.degree. C. and being endblocked with a siloxy unit selected from the group consisting of methylphenylvinylsiloxy units, dimethylvinylsiloxy units and units of the formula ##STR26## wherein R is a monovalent radical selected from the group consisting of alkyl radicals of from 1 to 3 carbon atoms inclusive and phenyl radicals,
- B. 5 to 95 weight percent based on the combined weight of (A) and (B) of a mercaptoorganopolysiloxane consisting essentially of a combination of units selected from dimethylsiloxane units, trimethylsiloxane units, units of the formula ##STR27## units of the formula ##STR28## units of the formula ##STR29## units of the formula ##STR30## units of the formula ##STR31## and units of the formula ##STR32## wherein R is defined above, R' is methyl or ethyl and n has a value of from 1 to 4 inclusive, there being in said mercaptoorganopolysiloxane an average of at least two sulfur containing siloxane units per molecule and no more than 16 weight percent --SH groups based on the weight of the mercaptoorganopolysiloxane, the molecular weight of the mercaptoorganopolysiloxane being at least 1,000, the amount of (A) and (B) being combined in weight ratios sufficient to provide a molar ratio of moles of --SH group in (B) per mole of C.dbd.C bond in (A) of 0.1:1 to 15:1,
- C. 1.4 to 5.5 parts by weight organic peroxide based on 100 parts by weight of (A) and (B) combined.
A method of preparing an elastomer comprising
- I. mixing at a temperature below 50.degree. C.
- A. 5 to 95 weight percent based on the combined weight of (A) and (B) of a polydimethylsiloxane having a viscosity of at least 0.3 Pa.sup.. s at 25.degree. C. and being endblocked with a siloxy unit selected from the group consisting of methylphenylvinylsiloxy units, dimethylvinylsiloxy units and units of the formula ##STR35## wherein R is a monovalent radical selected from the group consisting of alkyl radicals of from 1 to 3 carbon atoms inclusive and phenyl radicals,
- B. 5 to 95 weight percent based on the combined weight of (A) and (B) of a mercaptoorganopolysiloxane consisting essentially of a combination of units selected from dimethylsiloxane units, trimethylsiloxane units, units of the formula ##STR36## units of the formula ##STR37## units of the formula ##STR38## units of the formula ##STR39## units of the formula ##STR40## and units of the formula ##STR41## where R is defined above, R' is methyl or ethyl and n has a value of from 1 to 4 inclusive, there being in said mercaptoorganopolysiloxane an average of at least two sulfur containing siloxane units per molecule and no more than 16 weight percent --SH groups based on the weight of the mercaptoorganopolysiloxane, the molecular weight of the mercaptoorganopolysiloxane being at least 1,000, the amount of (A) and (B) being combined in weight ratios sufficient to provide a molar ratio of moles of --SH group in (B) per mole of C.dbd.C bond in (A) of 0.1:1 to 15:1,
- C. 1.4 to 5.5 parts by weight organic peroxide based on 100 parts by weight of (A) and (B) combined thereafter
- Ii. curing the resulting mixture of (I) above 20.degree. C.
2 more elements
Dependencies are inferred from the claim text.