Use of polyvinylacetate polymers or copolymers to increase the viscosity of the isocyanate component of a two-component curable polymeric system
Disclosed is a two-component curable polymeric system having increased viscosity. One component contains a homogeneous blend of a polyisocyanate and a homopolymer or copolymer of vinyl acetate. This component has a higher viscosity than the polyisocyanate alone, thereby increasing the viscosity of the two-component curable system. The other component of the two-component curable system is a composition containing an isocyanate reactive component. The polyisocyanate and the isocyanate reactive component react together (“cure”) to form a polymer. Typically, but not always, the isocyanate reactive component is a polyol or polyamine that is capable of reacting with the polyisocyanate, thereby forming a polyurethane (polyol) or polyurea (polyamine).
1. A two-component curable adhesive composition comprising:
a component A comprising at least one isocyanate-reactive composition, and a component B, wherein component B is an isocyanate functional composition comprising:
a) an isocyanate material comprising a polyisocyanate, wherein the polyisocyanate has an average isocyanate functionality of at least 2 and has a viscosity measured on a Brookfield viscometer at 20 RPM with spindle 6 at 25° C.; and
b) a polymer comprising, a vinyl acetate homopolymer, a vinyl acetate/vinyl chloride copolymer or a combination thereof;
wherein component B is a homogeneous mixture and wherein component B has a component B viscosity measured on a Brookfield viscometer at 20 RPM with spindle 6 at 25° C.
2. The two-component curable adhesive composition according to claim 1 , wherein the isocyanate-reactive composition in component A comprises at least one compound selected from polyol, polyamine, polythiol, aminoalcohol, and mixtures thereof.
3. The two-component curable adhesive composition according to claim 1 , wherein the isocyanate-reactive composition in component A comprises a polyol.
4. The two-component curable adhesive composition according to claim 1 , wherein the polyisocyanate comprises methylene diphenyl diisocyanate.
5. The two-component curable adhesive composition according to claim 1 , wherein the polyisocyanate comprises polymeric polyisocyanate.
6. The two-component curable adhesive composition according to claim 1 , wherein the component B viscosity is in the range of 500 mPa·sec to 300,000 mPa·sec.
7. The two-component curable adhesive composition according to claim 1 , wherein the polymer comprises, as polymerized units, at least 50% by weight of vinyl acetate.
8. The two-component curable adhesive composition according to claim 1 , wherein component A and component B are present in a stoichiometric ratio of 1.0: 0.90 to 1.0: 1.40 based on the number of moles of isocyanate-reactive groups in component A and the number of moles of isocyanate groups in component B.
9. The two-component curable adhesive composition according to claim 1 , wherein the isocyanate material is a pre-polymer comprising methylene diphenyl diisocyanate.
10. The two-component curable adhesive composition according to claim 1 , wherein the polyisocyanate has been reacted with a urethane to afford an allophanate.
11. The two-component curable adhesive composition according to claim 1 , wherein the composition viscosity is at least 1000 mPa·sec at a temperature of 25° C.
12. The two-component curable adhesive composition according to claim 1 , wherein the polymer comprises the copolymer of vinyl acetate and vinyl chloride.
13. The two-component curable adhesive composition according to claim 1 , wherein the vinyl acetate homopolymer has a weight average molecular weight in the range of 15,000 to 35,000 Daltons and the vinyl acetate/vinyl chloride copolymer has a weight average molecular weight in the range of 45,000 Daltons to about 140,000 Daltons.