Method of preparing polymer-fiber composite material and composite material resulting therefrom

Abstract

A method of preparing a composite material in which a dry mixture of a polymeric material and a fiber material is subjected to heating and pressure followed by cooling and reduction of pressure sufficient to melt the polymeric material and to maximize fiber material-polymeric material interactions, while minimizing fiber material-fiber material interactions. The resulting composite material has excellent strength.

What is claimed is:  
     
         1 . A method of preparing a composite material comprising: 
 a) mixing a dry short fiber material with a polymeric material in powder form to form a fiber material-polymeric material mixture;    b) heating the fiber material-polymeric material mixture at a temperature and under pressure sufficient to melt the polymeric material and initiate a fiber material-polymeric material interaction in the substantial absence of fiber material-fiber material interaction to form a pre-composite material; and    c) cooling and reducing the pressure of the pre-composite material to form said composite material.    
     
     
         2 . The method of  claim 1  wherein the short fiber material has a length of up to 5 mm.  
     
     
         3 . The method of  claim 1  wherein the short fiber material is in the form of particles having a maximum dimension of no more than about 0.5 mm.  
     
     
         4 . The method of  claim 1  wherein the fiber material-polymeric material mixture is heated to a temperature of from about 360° to 380° F.  
     
     
         5 . The method of  claim 1  wherein the fiber material-polymeric material mixture is subjected to a pressure of from about 80 to 115 psi.  
     
     
         6 . The method of  claim 1  wherein step (c) lowers the temperature and pressure of the pre-composite material to ambient temperature and pressure.  
     
     
         7 . The method of  claim 1  wherein the amount of the polymeric material is at least about 50% by weight of the fiber material-polymeric material mixture.  
     
     
         8 . The method of  claim 1  wherein the amount of the polymeric material is from about 50 to 75% by weight of the fiber material-polymeric material mixture.  
     
     
         9 . The method of  claim 1  further comprising adding a fiber material-polymeric material interaction enhancing agent to the fiber material-polymer material mixture.  
     
     
         10 . The method of  claim 9  wherein the fiber material-polymeric material interaction enhancing agent enhances the coupling of the fiber material to the polymeric material.  
     
     
         11 . The method of  claim 9  wherein the fiber material-polymeric material interaction enhancing agent is selected from the group consisting of polyethylene maleic anhydride, silanes, and combinations thereof.  
     
     
         12 . The method of  claim 1  wherein the fiber material is selected from the group consisting of a native cellulose material, treated wood pulp, wood pulp, synthetic fibers and combinations thereof.  
     
     
         13 . The method of  claim 1  wherein the polymeric material is selected from the group consisting of polypropylene, polyvinylacetate, high density polyethylene, polymethylmethacrylate and combinations thereof.  
     
     
         14 . A composite material produced by the process of  claim 1 .  
     
     
         15 . A composite material comprising fibers having a length of no more than about 5 mm in combination with a melted polymeric material in which the composite material contains no more than about 20% by weight of moisture.  
     
     
         16 . The composite material of  claim 1  in which the composite material contains no more than 15% by weight of moisture.  
     
     
         17 . The composite material of  claim 1  in which the composite material contains no more than 10% by weight of moisture.  
     
     
         18 . The composite material of  claim 1  in which the composite material contains no more than 5% by weight of moisture.  
     
     
         19 . The composite material of  claim 15  wherein the fibers having a length of from about 0.5 to 5 mm.  
     
     
         20 . The composite material of  claim 15  wherein the fibers are made from or derived from a cellulose material.  
     
     
         21 . The composite material of  claim 15  wherein the polymeric material is selected form the group consisting of polypropylene polyvinyl acetate, high density polyethylene, polymethyl methacrylate and mixtures thereof.  
     
     
         22 . The composite material of  claim 15  wherein the amount of the polymeric material is at least 50% of the composite material.