Advanced polymer wood composite

Abstract

The invention relates to a composition comprising a polymer and wood fiber composite that can be used in the form of a linear extrudate or thermoplastic pellet to manufacture structural members. The polymer and wood fiber composite structural members can be manufactured in an extrusion process or an injection molding process. The linear extrudate or pellet can have a cross-section of any arbitrary shape, or can be a regular geometric. The pellet can have a cross-section shape having a volume of at least about 12 mm 3 . Preferably the pellet is a right cylindrical pellet having a minimum radius of about 1.5 mm and a minimum length of 1 mm weighing at least 14 mg. The invention also relates to an environmentally sensitive recycle of waste streams. The polymer and wood fiber composite contains an intentional recycle of a waste stream comprising polymer flakes or particles or wood fiber. The waste stream can comprise, in addition to polymer such as polyvinyl chloride or wood fiber, adhesive, paint, preservative, or other chemical stream common in the wood-window or door manufacturing process, or mixtures thereof. The initial mixing step before extrusion of the composite material insures substantial mixing and melt contact between molten polymer and wood fiber. The extruded pellet comprises a consistent proportion of polymer, wood fiber and water. During the extrusion, water is removed intentionally to dry the material to a maximum water content of less than about 10 wt-% based on the pellet weight. To make a structural unit, the pellet is introduced into an extruder or injection molding apparatus wherein, under conditions of temperature and pressure, the composite pellet material is shaped into a useful cross-section. Alternatively, the extruded thermoplastic mass, in the form of an elongated linear extrudate without a pelletizing step, can be immediately directed after formation into an extruder or injection molding apparatus.

We claim:  
     
         1 . A composite pellet, capable of formation into a structural member, which pellet comprises a cylindrical extrudate having a radius of about 1 to 5 mm, a length of about 1 to 10 mm; 
 the pellet composition comprising: 
 (a) about 45 to 70 wt-% of a polymer comprising vinyl chloride;  
 (b) about 30 to 50 wt-% of wood fiber having a minimum thickness of 1 μm and a minimum length of 3 μm and a minimum aspect ratio of about 1.8; and  
 (c) less than about 8 wt-% water; and wherein the wood fiber is dispersed throughout a continuous polymer phase.  
   
     
     
         2 . The composition of  claim 1  wherein the polymer comprises a polyvinyl chloride homopolymer.  
     
     
         3 . The composition of  claim 1  wherein the polymer comprises a polyvinyl chloride copolymer.  
     
     
         4 . The composition of  claim 1  wherein the wood fiber comprises a by-product of milling or sawing wooden members.  
     
     
         5 . The composition of  claim 4  wherein the wood fiber comprises sawdust.  
     
     
         6 . The composition of  claim 1  wherein the composition additionally comprises a compatiblizing agent.  
     
     
         7 . The composition of  claim 2  wherein the polymer has a molecular weight of about 90,000±50,000.  
     
     
         8 . The composition of  claim 3  wherein the copolymer has a molecular weight of about 88,000±10,000.  
     
     
         9 . The composition of  claim 1  wherein the wood fiber has a fiber width of about 0.3 to 1.5 mm, a fiber length of about 1 to 10 mm and a aspect ratio of about 2 to 7.  
     
     
         10 . The composition of  claim 1  wherein the water comprises about 0.01 to 5 wt-% of the pellet.  
     
     
         11 . The composition of  claim 1  wherein the intentionally recycled impurity comprises about 0 to 5 wt-% of a hot melt adhesive composition, about 0 to 5 wt-% of a paint and about 0.01 to 15 wt-% of recycled polyvinyl chloride cladding, wherein the cladding comprises about 9.0 to 99.9 wt-% polyvinyl chloride and about 0.01 to 2 wt-% of a pigment.  
     
     
         12 . A polymer and wood fiber composite capable of formation into a structural member, which composite comprises a cylindrical linear extrudate having a radius of about 1 to 5 mm; the linear extrudate composition comprising: 
 (a) about 45 to 70 wt-% of a polymer comprising vinyl chloride;    (b) about 30 to 50 wt-% of wood fiber having a minimum thickness of 1 mm and a minimum length of 3 mm and an aspect ratio of about 1.8;    (c) less than about 8 wt-% water; and wherein the wood fiber is dispersed throughout a continuous polymer phase.    
     
     
         13 . The composition of  claim 12  wherein the polymer comprises a polyvinyl chloride homopolymer.  
     
     
         14 . The composition of  claim 12  wherein the polymer comprises a polyvinyl chloride copolymer.  
     
     
         15 . The composition of  claim 12  wherein the wood fiber comprises a by-product of milling or sawing wooden members.  
     
     
         16 . The composition of  claim 15  wherein the wood fiber comprises sawdust.  
     
     
         17 . The composition of  claim 12  wherein the composition additionally comprises a compatiblizing agent.  
     
     
         18 . The composition of  claim 15  wherein the polymer has a molecular weight of about 95,000±50,000.  
     
     
         19 . The composition of  claim 14  wherein the copolymer has a molecular weight of about 88,000±10,000.  
     
     
         20 . The composition of  claim 12  wherein the wood Fiber has a fiber width of about 0.3 to 1.5 mm, a fiber length of about 1 to 10 mm and a aspect ratio of about 2 to 7.  
     
     
         21 . The composition of  claim 12  wherein the water comprises about 0.01 to 5 wt-% of the pellet.  
     
     
         22 . A composite composition, capable of extrusion into a dimensionally stable structural member, which composition comprises: 
 (a) about 40 to 70 wt-% of a polymer comprising vinyl chloride;    (b) about 30 to 50 wt-% of wood fiber having a minimum width of 0.3 mm and a minimum length of 1 mm and an aspect ratio of greater than about 1.8;    (c) about 0.01 to 25 wt-% of an intentionally recycled impurity comprising thermoplastic polymer, an adhesive, a paint, a thermoplastic resin or mixtures thereof; and    (d) less than about 10 wt-% water;    wherein the wood fiber is dispersed throughout a continuous polymer phase.    
     
     
         23 . The composition of  claim 22  wherein the polymer comprises a polyvinyl chloride homopolymer.  
     
     
         24 . The composition of  claim 22  wherein the polymer comprises a polyvinyl chloride copolymer.  
     
     
         25 . The composition of  claim 22  wherein the wood fiber comprises a by-product of milling or sawing wooden members.  
     
     
         26 . The composition of  claim 22  wherein the wood fiber comprises sawdust.  
     
     
         27 . The composition of  claim 23  wherein the polymer has a molecular weight of about 95,000±50,000.  
     
     
         28 . The composition of  claim 24  wherein the copolymer has a molecular weight of about 88,000±10,000.  
     
     
         29 . The composition of  claim 22  wherein the wood fiber has a fiber width of about 0.3 to 1.5 mm, a fiber length of about 1 to 10 mm and a aspect ratio of about 2 to 7.  
     
     
         30 . The composition of  claim 22  wherein the concentration of water comprises about 0.01 to 3.5 wt-% of the composition.