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 are comprised of one or more silanes that have been reacted into the backbone of the prepolymer or reacted with the terminal groups of the prepolymer and 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 3
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.
5. A composition according to claim 1 which further comprises more than one reinforcing filler wherein the second reinforcing filler comprises titanium dioxide, calcium carbonate, surface treated silicas, titanium oxide or fumed silica.
6. A composition according to claim 5 wherein the second reinforcing filler is calcium carbonate.
7. A composition according to claim 1 wherein the one or more catalysts for the reaction of isocyanate moieties with hydroxyl groups comprise a mixture of a metal carboxylate and one of dimorpholinodiethyl ether and (di(2-(3,5-dimethylmorpholino)ethyl)) ether.
8. A composition according to claim 7 wherein the metal carboxylate is a bismuth carboxylate.