Wet use chopped strand glass as reinforcement in extruded products

Abstract

A method for incorporating wet use chopped strand glass (WUCS) in a screw extrusion process is provided. A polymeric resin is added to an extruder in a polymer feed zone and conveyed to a first compression zone where the resin is at least partially melted. The molten resin is conveyed to a high volume zone where WUCS fibers are added. In the high volume zone, the flights of the screw may have a greater pitch to facilitate the introduction of the WUCS into the extruder. The molten resin/fiber mixture is conveyed to a second compression zone where the resin and fibers are intimately compounded. Next, the molten resin/fiber mass is conveyed to a low pressure zone where moisture evaporated from the fibers is released through an opening. The resin/fiber mixture is then conveyed through a compression/die feed zone to further compound and mix the resin and fibers.

1 . A method for forming a reinforced extruded thermoplastic product comprising the steps of: 
 at least partially melting a polymeric resin in a barrel of an extruder in a first compression zone, said barrel encasing at least one rotatable screw having flights and extending substantially along a length of said barrel;    feeding wet reinforcement fibers into said barrel in a high volume zone where said flights are positioned at a greater pitch than said flights located in said first compression zone to facilitate the introduction of said wet reinforcement fibers into said barrel, said wet reinforcement fibers mixing with said molten resin to form a molten resin/fiber mixture;    conveying said resin/fiber mixture downstream along said at least one screw to a low pressure zone where water vapor released from said wet reinforcement fibers exits said barrel through an opening in said barrel; and    passing said resin/fiber mixture through an extrusion die to form said extruded thermoplastic product.    
     
     
         2 . The method according to  claim 1 , wherein said wet reinforcement fibers are wet use chopped strand glass fibers.  
     
     
         3 . The method according to  claim 2 , further comprising the step of: 
 passing said resin/fiber mixture through a second compression zone where said wet use chopped strand glass fibers are at least partially filamentized prior to said conveying step.    
     
     
         4 . The method according to  claim 3 , wherein said flights in said second compression zone have a pitch that is smaller than the pitch of said flights in said polymer feed zone, said low pressure zone, and said high volume zone.  
     
     
         5 . The method according to  claim 3 , further comprising the step of: 
 adding said polymeric resin to said barrel in a polymer feed zone prior to said melting step.    
     
     
         6 . The method according to  claim 5 , further comprising the step of: 
 passing said resin/fiber mixture through a compression/die feed zone to further mix and compound said resin and said wet use chopped strand glass fibers prior to entering said extrusion die.    
     
     
         7 . The method according to  claim 3 , further comprising the step of: 
 adding a blowing agent to said barrel.    
     
     
         8 . The method according to  claim 5 , further comprising the step of: 
 pre-blending a blowing agent with said resin prior to adding said resin to said barrel.    
     
     
         9 . The method according to  claim 2 , further comprising the step of: 
 at least partially opening said wet use chopped strand glass fibers prior to feeding said wet use chopped strand glass fibers into said barrel.    
     
     
         10 . The method according to  claim 2 , further comprising the step of: 
 removing at least a portion of water located in said wet use chopped strand glass fibers prior to feeding said wet use chopped strand glass fibers into said barrel.    
     
     
         11 . The method according to  claim 2 , further comprising the step of: 
 embossing said extruded thermoplastic product.    
     
     
         12 . The method according to  claim 2 , further comprising the step of: 
 co-extruding a cap stock onto said extruded thermoplastic product.    
     
     
         13 . An apparatus for extruding a reinforced thermoplastic product comprising: 
 an elongated barrel having an outlet;    a polymer resin feed hopper to hold a polymer resin;    a wet reinforcement fiber feed hopper to hold wet reinforcement fibers;    an opening in said barrel downstream of said wet reinforcement fiber feed hopper to vent moisture released from said wet reinforcement fibers; and    at least one rotatable screw disposed within said barrel and extending substantially the length of said barrel, said at least one screw having flights in cooperation with an inner surface of said barrel to define a passage for conveying said resin and said wet reinforcement fibers downstream through said barrel to said outlet, said at least one screw including: 
 a polymer feed zone where said polymer resin is introduced into said barrel;  
 a high volume zone downstream of said polymer feed zone, said flights in said high volume zone having a pitch sufficient to facilitate the introduction of said wet reinforcement fibers into said barrel;  
 a first compression zone where said resin and said wet reinforcement fibers are compounded and said wet reinforcement fibers are at least partially filamentized; and  
 a low pressure zone downstream of said high volume zone, said low pressure zone having flights positioned at a pitch greater than said pitch of said flights in said first compression zone.  
   
     
     
         14 . The apparatus of  claim 13 , wherein said wet reinforcement fibers are wet use chopped strand glass fibers.  
     
     
         15 . The apparatus of  claim 14 , further comprising: 
 a first feedthroat interconnecting said polymer resin feed hopper and said barrel; and    a second feedthroat interconnecting said wet reinforcement fiber feed hopper and said barrel.    
     
     
         16 . The apparatus of  claim 15 , further comprising a metering mechanism within said first feedthroat to feed said polymer resin into said barrel.  
     
     
         17 . The apparatus of  claim 15 . further comprising an inlet in direct communication with said first feedthroat to supply at least one member selected from the group consisting of blowing agents, thermostabilizers, UV stabilizers, lubricants, colorants, fillers, compatibilizers, melt strength enhancers and tackifiers to said first feedthroat.  
     
     
         18 . The apparatus of  claim 13 , further comprising an opener connected to said wet reinforcement fiber feed hopper to at least partially filamentize said wet reinforcement fibers.  
     
     
         19 . The apparatus of  claim 18 , further comprising a condenser interconnecting said opener and said reinforcement fiber feed hopper to at least partially dry said at least partially filamentized wet reinforcement fibers.  
     
     
         20 . The apparatus of  claim 13 , wherein said at least one screw further includes a second compression zone positioned downstream of said polymer feed zone where said polymer resin is at least partially melted.  
     
     
         21 . The apparatus of  claim 20 , wherein said at least one screw further comprises a compression/die feed zone positioned adjacent to said outlet, said flights in said compression/die feed zone having a pitch that is the same as or smaller than the pitch of said polymer feed zone, said first compression zone, said high volume zone, and said low pressure zone.  
     
     
         22 . The apparatus of  claim 21 , wherein said flights in said high volume zone have a pitch that is greater than the pitch of said flights in said first and second compression zones.  
     
     
         23 . The apparatus of  claim 13 , wherein said flights in said first compression zone have a pitch that is less than the pitch of said polymer feed zone, said high volume zone, and said low pressure zone.  
     
     
         24 . An apparatus for extruding a reinforced thermoplastic product comprising: 
 an elongated barrel having an outlet;    a polymer resin feed hopper to hold a polymer resin;    a resin/fiber feedthroat interconnecting said polymer resin feed hopper to said barrel;    a wet reinforcement fiber feed hopper connected to said resin/fiber feedthroat to hold wet reinforcement fibers;    an opening in said barrel downstream of said polymer resin feed hopper and said wet reinforcement fiber feed hopper to vent moisture released from said wet reinforcement fibers; and    at least one rotatable screw disposed within said barrel and extending substantially the length of said barrel, said at least one screw having flights in cooperation with an inner surface of said barrel to define a passage for conveying said resin and said wet reinforcement fibers downstream through said barrel to said outlet, said at least one screw including: 
 a polymer feed zone where said polymer resin is introduced into said barrel;  
 a compression zone positioned downstream of said polymer feed zone where said polymer resin is at least partially melted;  
 a low pressure zone having flights positioned at a pitch greater than the pitch of said flights in said compression zone; and  
 a compression/die feed zone positioned adjacent to said outlet, said flights in said compression/die feed zone having a pitch that is the same as or smaller than the pitch of said polymer feed zone, said compression zone, and said low pressure zone.  
   
     
     
         25 . The apparatus of  claim 24 , wherein said wet reinforcement fibers are wet use chopped strand glass fibers.  
     
     
         26 . The apparatus of  claim 25 , further comprising a member selected from the group consisting of one or more baffles, a crammer and a vibratory screw positioned in said resin/fiber feedthroat to mix said resin and said wet reinforcement fibers.  
     
     
         27 . The apparatus of  claim 25 , wherein said wet fiber feedthroat interconnects said wet reinforcement fiber feed hopper and said resin/fiber feedthroat, said wet fiber feedthroat including a vibratory screw.  
     
     
         28 . The apparatus of  claim 25 , further comprising an opener connected to said wet reinforcement fiber feed hopper to at least partially filamentize said wet use chopped strand glass fibers.  
     
     
         29 . The apparatus of  claim 28 , further comprising a condenser interconnecting said opener and said reinforcement fiber feed hopper to at least partially dry said filamentized wet use chopped strand glass fibers.  
     
     
         30 . A method for forming a reinforced extruded thermoplastic product comprising the steps of: 
 adding a premix to a barrel of an extruder in a polymer feed zone, said barrel encasing at least one rotatable screw having flights and extending substantially along a length of said barrel;    at least partially melting said premix in a compression zone to form a molten resin/fiber mixture;    conveying said molten resin/fiber mixture downstream along said at least one screw to a low pressure zone where water vapor released from said wet reinforcement fibers as said resin/fiber moisture is conveyed along said at least one screw escapes from said barrel through an opening in said barrel; and    passing said molten resin/fiber mixture through an extrusion die to form said extruded thermoplastic product.    
     
     
         31 . The method of  claim 30 , wherein said wet reinforcement fibers are wet use chopped strand glass fibers.  
     
     
         32 . The method according to  claim 31 , further comprising the step of: 
 passing said molten resin/fiber mixture through a compression/die feed zone prior to passing said resin/fiber mixture through said die, said flights in said die feed zone having a pitch that is no larger than said flights in said polymer feed zone.    
     
     
         33 . The method of  claim 32 , further comprising the step of: 
 blending a polymer resin and wet reinforcement fibers to form said resin/fiber premix.    
     
     
         34 . The method according to  claim 33 , further comprising the step of: 
 adding a member selected from the group consisting of blowing agents, thermostabilizers, UV stabilizers, lubricants, colorants, fillers, compatibilizers, melt strength enhancers, and tackifiers to said barrel.    
     
     
         35 . The method according to  claim 31 , further comprising the steps of: 
 at least partially opening said wet use chopped strand glass fibers prior to blending said wet use chopped glass fibers and said resin; and    removing at least a portion of water located in said wet use chopped strand glass fibers after said wet use chopped strand glass fibers have been at least partially opened.    
     
     
         36 . A method for forming a reinforced extruded thermoplastic product comprising the steps of: 
 feeding a polymeric resin and wet reinforcement fibers into a barrel of an extruder;    at least partially melting the polymeric resin in the barrel;    mixing said fibers with said molten resin to form a molten resin/fiber mixture;    conveying said resin/fiber mixture downstream along said at least one screw to a zone where water vapor released from said wet reinforcement fibers exits said barrel through an opening in said barrel; and    passing said resin/fiber mixture through an extrusion die to form said extruded thermoplastic product.    
     
     
         37 . A method for forming a reinforced extruded thermoplastic product comprising the steps of: 
 feeding a polymeric resin and wet reinforcement fibers into a barrel of an extruder;    at least partially melting the polymeric resin in the barrel;    mixing with said molten resin to form a molten resin/fiber mixture;    conveying said resin/fiber mixture downstream along said at least one screw to a zone where at least a portion of the water vapor released from said wet reinforcement fibers acts as a blowing agent for said resin; and    passing said resin/fiber mixture through an extrusion die to form said extruded thermoplastic product.    
     
     
         38 . The method according to  claim 37 , further comprising the step of: 
 conveying said resin/fiber mixture downstream along said at least one screw to a zone where at least a portion of the water vapor released from said wet reinforcement fibers is removed from said barrel.    
     
     
         39 . The method according to  claim 37 , further comprising the step of: 
 feeding active or anhydrous fillers to said mixture to bind moisture released during said process.    
     
     
         40 . The method according to  claim 37 , further comprising the step of: 
 adding a blowing agent to said barrel.