Filled polyurethane composites with lightweight fillers

1. A composite comprising:

(a) a polyurethane formed by the reaction of

(i) one or more isocyanates selected from the group consisting of diisocyanates, polyisocyanates, and mixtures thereof, and

(ii) one or more polyols;

(b) from 35% to 75% by weight, based on the total weight of the composite, of a particulate filler having a bulk density of 1 g/cm 3 or greater; and

(c) from 4% to 20% by weight, based on the total weight of the composite, of a lightweight filler having a bulk density of from 0.01 g/cm 3 to less than 1 g/cm 3 , wherein the lightweight filler is chosen from expanded volcanic ash, expanded perlite, pumicite, expanded vermiculite, expanded clay, foamed glass, soybean hulls, rice hulls, seeds, seed husks, chopped straw, expanded polystyrene beads, scoria, and combinations thereof;

wherein the composite has a density of from 2 lb/ft 3 to 37 lb/ft 3 ; and

wherein the composite has flexural strength of 1000 psi or greater as measured by ASTM C1185-08 (2012).

2. The composite of claim 1 , wherein the lightweight filler has a bulk density of from 0.05 g/cm 3 to 0.6 g/cm 3 .

3. The composite of claim 1 , wherein the lightweight filler includes expanded perlite, expanded clay, foamed glass, or a combination thereof.

4. The composite of claim 1 , wherein the lightweight filler has an average particle size diameter of from 0.01 micron to 2 mm.

5. The composite of claim 1 , wherein the particulate filler comprises fly ash.

6. The composite of claim 5 , wherein the fly ash is present in an amount of from 50% to 75% by weight, based on the total weight of the composite.

7. The composite of claim 1 , wherein the weight ratio of the lightweight filler to the particulate filler is from 1:10 to 1:1.

8. A building material comprising the composite of claim 1 .

9. The composite of claim 1 , where the density is from 10 lb/ft 3 to 35 lb/ft 3 .

10. A method of making a polyurethane composite comprising:

(a) mixing

(1) one or more isocyanates selected from the group consisting of diisocyanates, polyisocyanates, and mixtures thereof,

(2) one or more polyols,

(3) 35% to 75% by weight, based on the total weight of the mixture, of a particulate filler having a bulk density of 1 g/cm 3 or greater, and

(4) 4% to 20% by weight, based on the total weight of the mixture, of a lightweight filler having a bulk density of from 0.01 g/cm 3 to less than 1 g/cm 3 to form a mixture, wherein the lightweight filler is chosen from expanded volcanic ash, expanded perlite, pumicite, expanded vermiculite, expanded clay, foamed glass, soybean hulls, rice hulls, seeds, seed husks, chopped straw, expanded polystyrene beads, scoria, and combinations thereof;

(b) allowing the one or more isocyanates and the one or more polyols to react in the presence of the particulate filler and the lightweight filler to form the polyurethane composite having

(1) a density of from 2 lb/ft 3 to 37 lb/ft 3 , and

(2) flexural strength of 1000 psi or greater as measured by ASTM C1185-08 (2012), and

wherein the mixture is free of a blowing or foaming agent other than water.

11. The method of claim 10 , wherein the mixture further comprises a catalyst.

12. The method of claim 10 , wherein the mixture contains less than about 0.5 wt % water.

13. The composite of claim 1 , wherein the polyurethane is present in an amount of from 15% to 40%, by weight, based on the total weight of the composite.

14. The composite of claim 13 , further comprising from 4% to 8% by weight, based on the total weight of the composite, of a fiber material.

15. The method of claim 10 , wherein the mixture is processed at a temperature of from 200° F. to 500° F.

16. The method of claim 10 , wherein the mixture does not comprise a catalyst.

17. The composite of claim 1 , wherein the composite has a handleability of 9 in-lb/in or greater as measured by ASTM C1185-08 (2012).

18. The method of claim 10 , wherein the polyurethane composite has a handleability of 9 in-lb/in or greater as measured by ASTM C1185-08 (2012).

19. The composite of claim 3 , wherein the particulate filler includes fly ash.

20. The method of claim 10 , wherein the particulate filler includes fly ash, and wherein the lightweight filler includes expanded perlite, expanded clay, foamed glass, or a combination thereof.