High modulus, nonconductive adhesive useful for installing vehicle windows
The invention is a composition comprising a) one or more isocyanate functional polyether based prepolymers containing one or more organic based polymers dispersed therein; b) one or more isocyanate functional polyester based prepolymers which is solid at 23° C.; c) one or more polyisocyanates having a nominal functionality of about 3 or greater; d) one or more conductive carbon blacks in an amount such that the composition has a dielectric constant of about 15 or less; and e) one or more catalysts for the reaction of isocyanate moieties with hydroxyl groups, wherein the composition demonstrates upon cure a modulus of 2.0 MPa or greater at 25° C. measured according to ASTM D4065; a dielectric constant of about 15 or less; a sag of an uncured sample of less than 2 mm, a press flow viscosity of about 20 to about 50 and a storage modulus of about 5.3×10 5 Pa or greater.
1. A composition comprising:
a) from about 25 to about 55 percent of one or more isocyanate functional polyether based prepolymers containing one or more organic based polymers dispersed therein having a free isocyanate content of about 0.8 to about 2.2 percent by weight based on the weight of the prepolymer;
b) from about 0.5 to about 10 percent of one or more isocyanate functional polyester based prepolymers which is solid at 23° C.;
c) from about 1 to about 8 percent of one or more polyisocyanates having a nominal functionality of about 3 or greater;
d) from about 10 to about 18 percent of one or more conductive carbon blacks in an amount such that the composition has a dielectric constant of about 15 or less; and
e) from about 0.005 to about 2 percent one or more catalysts for the reaction of isocyanate moieties with hydroxyl groups;
wherein the percentages are based on the weight of the composition and the composition demonstrates upon cure a modulus of 2.0 MPa or greater at 25° C. measured according to ASTM D4065; a dielectric constant of about 15 or less; a sag of an uncured sample of less than 2 mm, a press flow viscosity of about 20 to about 50 and a storage modulus of about 5.3×10 5 Pa or greater.
2. A composition according to claim 1 wherein the isocyanate functional polyester prepolymer exhibits a melting point of about 50° C. or greater.
3. A composition according to claim 2 wherein the polyfunctional polyisocyanate is an oligomer or polymer based on hexamethylene diisocyanate or methylene diphenyl diisocyanate.
4. A composition according to claim 1 wherein the organic based polymer is a thermoplastic polymer, a rubber modified thermoplastic polymer or a polyurea.
5. A composition according to claim 4 wherein the organic based polymer is a rubber modified thermoplastic polymer.
6. A composition according to claim 1 wherein
a) the one or more isocyanate functional polyether based prepolymers are present in an amount of about 25 to about 55 percent;
b) the one or more isocyanate functional polyester based prepolymers are present in an amount of about 1 to about 5 percent;
c) one or more polyfunctional isocyanates are present in an amount of about 1 to about 8 percent;
d) one or more conductive carbon blacks are present in an amount of about 10 to about 18 percent; and
e) one or more catalysts for the reaction of isocyanate moieties with hydroxyl groups are present in an amount of about 0.1 to about 1.75 percent; wherein the percentages are based on the weight of the composition.