Moisture curable silicone-urethane copolymer sealants
AssigneeDAP Products Inc.
InventorGary L. Linden
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Abstract
A moisture curable, one-part sealant composition comprising a silicone-urethane copolymer is provided. The copolymer is prepared via reaction of an alpha, omega hydroxy terminated siloxane having a molecular weight of 5,000 or less with a polyisocyanate. The copolymer has a free NCO content of greater than about 1 wt. % available for moisture cure upon usage.
Claims13
A clear, paintable, one-part storage stable, moisture curable, sealant/caulk composition for filling joints between adjacent structural units, said composition being devoid of solvent and comprising a polyurethane-silicone copolymer, said copolymer comprising the reaction product of a hydroxy functional siloxane having a molecular weight of less than about 5,000 and an aliphatic or alicyclic polyisocyanate compound, said hydroxy functional siloxane being represented by the formula ##STR6## wherein each R.sub.1 is --CH.sub.2 CH.sub.2 CH.sub.2 OH each R.sub.2 is methyl and wherein x is from 1 to about 50, said copolymer, prior to moisture curing, comprising about 8.67 wt. % of free NCO groups, said composition emitting only CO.sub.2.
A clear, paintable, one-part storage stable sealant/caulk composition for filling joints between adjacent structural units, said composition being devoid of solvent and comprising a moisture curable polyurethane-silicone copolymer, said copolymer consisting essentially of the reaction product of an aliphatic or cycloaliphatic polyisocyanate and an alpha, omega, hydroxy terminated siloxane compound represented by the formula ##STR7## wherein each R.sub.1 is --CH.sub.2 CH.sub.2 CH.sub.2 OH and wherein x is from about 1-50, said siloxane compound having a molecular weight of less than 5,000;
- said copolymer, prior to moisture curing comprising about 8.67 wt. % of free NCO groups and being characterized by having a Shore A hardness of between about 80-85, said composition, upon curing, emitting only CO.sub.2.
A method of making a clear, paintable, one-part storage stable, moisture curable polyurethane-silicone copolymer for filling a joint located between adjacent structural units, and wherein said composition will emit only CO.sub.2 upon curing, said method comprising the steps of:
- a) providing a reaction medium including
- 1) an hydroxy functional siloxane having a molecular weight of less than 5,000 and having the formula ##STR8## wherein each R.sub.1 is --CH.sub.2 CH.sub.2 CH.sub.2 OH each R.sub.2 is methyl, wherein x is from 1 to about 50;
- and
- 2) a polyisocyanate compound comprising a member selected from the group consisting of aliphatic polyisocyanates and cycloaliphatic polyisocyanates;
- in an organic solvent, providing a stoichiometric excess of NCO groups to OH groups in said reaction medium such that the copolymer formed from said siloxane and polyisocyanate compound will have about 8.67 weight % free NCO groups therein;
- (b) reacting said siloxane and said polyisocyanate compound at room temperature under anhydrous conditions;
- and
- (c) removing said solvent from said reaction medium thereby isolating said copolymer.
Dependencies are inferred from the claim text.