Cellulosic-reinforced composites having increased resistance to water absorption

1. A cellulosic-reinforced composite comprising:

(a) 35 to 85 wt. % polyolefin matrix polymer consisting of:

(i) a high density polyethylene resin having a density in the range 0.935 to 0.970 g/cm 3 and

(ii) a silane copolymer, the weight ratio of said high density polyethylene to said silane copolymer ranging from 50:1 to 1:50; and

(b) 15 to 65 wt. % cellulosic filler.

2. The composite of claim 1 wherein the high density polyethylene is a copolymer of ethylene and butene-1, hexene-1 or octene-1 and has a density from 0.940 to 0.965 g/cm 3 .

3. The composite of claim 2 wherein the high density polyethylene has a density from 0.945 to 0.960 g/cm 3 and melt index from 0.01 to 50 g/10 min.

4. The composite of claim 1 wherein the silane copolymer is an ethylene polymer having silane functionality incorporated in the polymer chain by copolymerization or attached to the polymer chain by grafting.

5. The composite of claim 4 wherein the silane copolymer has from 0.1 to 20 wt. % alkoxysilane of the formula H 2 C═CH—Si—(OR) 3 where R is a C 1-4 alkyl group incorporated by copolymerization or grafting.

6. The composite of claim 5 wherein the silane copolymer has a density from 0.865 to 0.965 g/cm 3 and melt index from 0.05 to 50 g/10 min.

7. The composite of claim 6 wherein the silane copolymer is a copolymer of ethylene and 0.5 to 7.5 wt. % vinyltrimethoxysilane having a density from 0.915 to 0.960 g/cm 3 and melt index from 0.25 to 40 g/10 min.

8. The composite of claim 1 wherein the weight ratio of high density polyethylene to silane copolymer is from 20:1 to 1:1.

9. The composite of claim 1 wherein the cellulosic filler is a wood filler and comprises 20 to 60 wt. % of the composite.

10. The composite of claim 9 wherein the wood filler is wood flour.

11. The composite of claim 1 containing 0.01 to 25 wt. % additional additives.

12. The composite of claim 11 which contains 0.01 to 2 wt. % metal carboxylate.

13. The composite of claim 11 which contains 0.1 to 10 wt. % ethylene polymer grafted with 0.1 to 5 wt. % ethylenically unsaturated carboxylic acid or acid derivative.

14. The composite of claim 11 which contains 1 to 20 wt. % mineral filler.

15. A cellulosic-reinforced composite comprising:

(a) 35 to 85 wt. polyolefin matrix polymer consisting of a mixture of

(i) high density copolymer of ethylene and butene-1, hexene-1 or octene-1 having a density from 0.940 to 0.965 g/cm 3 and melt index from 0.01 to 50 g/10 min and

(ii) ethylene polymer having 0.1 to 20 wt. % alkoxysilane of the formula H 2 C═CH—Si—(OR) 3 where R is a C 1-4 alkyl group incorporated in the polymer chain by copolymerization or attached to the polymer chain by grafting, the weight ratio of (i):(ii) ranging from 20:1 to 1:1; and

(b) 15 to 65 wt. % wood filler.

16. The composite of claim 15 comprising 40 to 80 wt. % (a) and 20 to 60 wt. % wood flour.