Wood particle filled polyvinyl chloride composites and their foams
View Patent ↗Extruded composite compositions of PVC and wood particles containing chitosan or chitin as a coupling agent are described. The composite compositions have improved physical and mechanical properties.
1. A process for preparing a composite composition which comprises:
(a) blending a mixture of:
(1) coupling agent chitin;
(2) polyvinyl chloride (PVC);
(3) a dried wood flour with a moisture content of less than 1% by weight, wherein the coupling agent is present in an amount up to about 10 percent by weight of the wood flour; and
(4) a heat stabilizer for the PVC; and
(b) extruding the blended mixture at an elevated temperature between about 150° C. and a decomposition temperature of the PVC or wood to form the composite composition with increased dimensional stability based upon water adsorption with a reduction in a percent of thickness swell compared to the composition without the chitin.
2. The process of claim 1 wherein the extruder has dual screws which are counter-rotating.
3. The process of claims 1 or 2 wherein as an additional step the extruded composite composition is pressed at an elevated temperature and pressure to provide a shaped product.
4. The process of claims 1 or 2 wherein a foaming agent which expands as a gas at the elevated temperatures is provided in the mixture of step (a).
5. The process of claim 1 wherein the heat stabilizer is a tin stabilizer.