Attached, high reactivity rigid polyurethane foams

1. A method of forming a rigid polyurethane foam attached to an automotive part having an open cavity, comprising mixing a polyisocyanate component with a polyol component in the presence of at least one catalyst for the reaction of a polyol with a polyisocyanate and a blowing agent, dispensing the resulting mixture onto an automotive part defining an open cavity and subjecting the mixture to conditions sufficient to cause the mixture to cure to form a foam having a bulk density of 3 to 40 pounds per cubic foot (48-640 kg/m 3 ) that is adherent to the automotive part, wherein

(a) the polyisocyanate component contains at least one compound having a plurality of free isocyanate groups,

(b) the polyol component contains isocyanate-reactive materials that have an average functionality of at least about 2.3 and includes at least one polyol and,

(c) the volume ratio of the polyisocyanate component to the polyol component is no greater than 5:1 and no less than 1:5,

(d) the ratio of isocyanate groups in the polyisocyanate component to the number of isocyanate-reactive groups in the polyol component is from about 0.7:1 to about 1.25:1;

(e) the blowing agent consists of a carbamate of an alkanolamine or a mixture of water and a carbamate of an alkanolamine; and

(f) the cream time of the mixture is less than 2 seconds.

2. The method of claim 1 wherein the carbamate is contained in a non-aqueous medium.

3. The method of claim 2 wherein the carbamate is a reaction product of carbon dioxide and N-methyl-2-aminoethanol, N-ethyl-2-aminoethanol, 2-(2-N-methyl-aminoethyl)-1,2-ethanediol, N,N′-bis-(β-hydroxyethyl)-ethylene diamine, N,N′-bis-(β-hydroxypropyl)ethylene diamine, N,N′-bis-(β-hydroxyethyl)-1,2-propylene diamine, N,N′-bis-(β-hydroxypropyl)-1,3-propane diamine, N,N′-bis-(β-hydroxyethyl)-1-methyl-2,4-diaminocyclohexane N,N′-bis-(β-hydroxyethyl)-1-methyl-2,6-diaminocyclohexane, N,N′-bis-(β-hydroxypropyl)-p-xylylene diamine, N-(β-hydroxyethyl-N′-(β-hydroxypropyl)ethylene diamine or tris-(β-hydroxyethyl)-1,6,11 triaminoundecane.

4. The method of claim 2 wherein the carbamate is the reaction product of carbon dioxide and an alkanolamine having the structure

H z N—[(CHR′—CHR″—O—) a —(CH 2 ) x —OH] y

where y is at least 1, z+y equals 3, R′ and R″ are independently hydrogen, ethyl or methyl, x is a number from 1 to 4, and a is 1 or 2, provided that a times y is not greater than 2.

5. The method of claim 4 wherein the alkanolamine is 2-(2-aminoethoxy)ethanol or 2-(2-(2-aminoethoxy)ethoxy)ethanol.

6. The method of claim 1 wherein the isocyanate component includes a isocyanate-terminated prepolymer which is a reaction product of an organic polyisocyanate and at least one polyol.

7. The method of claim 1 wherein the isocyanate component includes a isocyanate-terminated prepolymer which is a reaction product of an organic polyisocyanate, at least one polyol and a hydroxyl-functional acrylate or methacrylate.

8. The method of claim 6 wherein the polyisocyanate component includes at least one plasticizer.

9. The method of claim 1 wherein at least one polyol in the polyol component contains a tertiary amine group.

10. The method of claim 1 wherein the polyol component contains at least one amine-terminated polyether.

11. The method of claim 1 wherein the blowing agent is blended into the polyol component before the polyol component and polyisocyanate component are mixed.

12. The method of claim 1 wherein the catalyst is blended into the polyol component before the polyol component and polyisocyanate component are mixed.

13. The method of claim 1 wherein the cream time is less than 1 second.

14. The method of claim 1 wherein the automotive part is assembled onto a vehicle or vehicle frame when the foam formulation is applied and foamed.

15. The method of claim 14 wherein the automotive part is a pillar, rocker, sill, sail, cowl, plenum, seam, frame rail, vehicle sub assembly, hydro-formed part, cross car beam or engine cradle.