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Moldable elastomeric pressure sensitive adhesives

  • US 4,831,070 A
  • Filed: 11/02/1987
  • Issued: 05/16/1989
  • Est. Priority Date: 11/02/1987
  • Status: Expired due to Fees
First Claim
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1. A composition for forming elastomeric pressure sensitive adhesives comprising a homogeneous mixture of:

  • (A) a xylene-soluble resin copolymer employed in an amount from 50 to 70 parts by weight, said xylene-soluble resin copolymer consisting essentially of R3 SiO1/2 units and SiO4/2 units in a mol ratio of from 0.6 to 0.9R3 SiO1/2 units for each SiO4/2 unit, wherein each R denotes, independently, a monovalent hydrocarbon radical having from 1 to 6 inclusive carbon atoms, said resin copolymer having less than 0.7 weight % silicon-bonded hydroxyl units, said resin copolymer substantially free of volatile components,(B) a polydiorganosiloxane fluid employed in an amount from 30 to 50 parts by weight, said polydiorganosiloxane fluid endcapped with silicon-bonded hydroxyl groups and having the average formula HO(R'"'"'2 SiO)n H wherein each R'"'"' denotes, independently, a monovalent hydrocarbon or halohydrocarbon radical having from 1 to 6 inclusive carbon atoms and n has an average value so that the polydiorganosiloxane fluid has a viscosity such that the elastomeric pressure sensitive adhesive composition has a plasticity of less than 150×

    10-3 inches at 25°

    C. without the addition of organic solvents, the total of resin copolymer (A) and polydiorganosiloxane fluid (B) being 100 parts by weight,(C) an alkoxy-containing organosilicon compound having an average of more than two silicon-bonded alkoxy units per molecule employed in an amount from 0.35 to 2 parts by weight,(D) a condensation catalyst employed in an amount from 0.5 to 13 parts by weight, and(E) a trimethyl-endblocked polydimethylsiloxane employed from 0 to 15 parts by weight and having a viscosity of from 10 to 1000 cSt. at 25°

    C.

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