Moisture-curable hot melt silicone pressure-sensitive adhesives

Claim 1

A moisture-curable silicone hot melt pressure-sensitive adhesive composition comprising: (i) a hydroxyl-functional organopolysiloxane resin having a softening point above ambient temperature and comprising R 3 SiO 1/2 siloxane units and SiO 4/2 siloxane units, wherein the mole ratio of the R 3 SiO 1/2 siloxane units to SiO 4/2 siloxane units has a value of from 0.5/1 to 1.2/1, R is selected from hydrocarbon radicals and halogenated hydrocarbon radicals and said hydroxyl content is 1.2 to 6 percent by weight; (ii) a diorganopolysiloxane polymer each terminal group thereof containing at least two silicon-bonded alkoxy radicals having 1-4 carbon atoms, said polymer having a viscosity of 25°C. of 20 to 100,000 mPa·s (centipoise) or a diorganopolysiloxane polymer as just defined capped in situ; and the weight ratio of said resin to said polymer being in the range 40:60 to 80:20; (iii) a silane of the formula R' 4-y SiX y , in which R' is selected from hydrocarbon radicals and substituted hydrocarbon radicals having 1-6 carbon atoms, X is a hydrolyzable group and y is 2 to 4, the amount of said silane being sufficient to provide stability to said composition; and (iv) sufficient catalyst to accelerate the cure of said composition, said composition being a solvent-free, solid at 25°C having a minimum room temperature dynamic viscosity in the range 2 x 10 7 to 8 x 10 7 mPa·s (cP) when measured at 1 radion/sec and which cures to a non-tacky elastomer upon exposure to moisture.