Method of making continuous filament reinforced structural plastic profiles using pultrusion/coextrusion

Abstract

A system and method are disclosed for producing a continuous filament reinforced thermoplastic profile having consistent cross section. A continuous reinforcing filament is pre-wetted with a first thermoplastic resin and introduced into a die, where it is contacted with a second thermoplastic resin extruded from an extruder at melt state. The temperature of the die is carefully controlled so that the pre-wetted filament and first resin do not cure or solidify until after they have contacted and mixed with the second thermoplastic resin. The mixture temperature is then controlled to make a substantially solidified profile pre-shape. A capping layer comprising a third thermoplastic resin is then co-extruded onto the outer surface of the pre-shape. A multistage die for bringing together the filament and thermoplastic resins and for maintaining appropriate temperatures at each stage of the profile-forming process is also disclosed.

1 . A method for manufacturing a reinforced thermoplastic structure, comprising:
 providing a plurality of reinforcing filaments;   wetting the reinforcing filaments with a first thermoplastic resin;   introducing the reinforcing filaments with the first thermoplastic resin into a first portion of a die and maintaining said thermoplastic resin at a first temperature;   introducing a second thermoplastic resin into a second portion of the die;   contacting the second thermoplastic resin with the reinforcing filaments and the first thermoplastic resin within the second portion of said die; and   heating the first and second thermoplastic polymer resins to a second temperature to form a partially solidified reinforced thermoplastic structure having a predetermined outer shape; and   wherein the first temperature is a value below the solidification temperature of the first thermoplastic resin and the second temperature is a value above the solidification temperature of at least the first thermoplastic resin.   
     
     
         2 . The method of  claim 1 , further comprising contacting the partially solidified reinforced thermoplastic structure with a third thermoplastic resin to form a capping layer on an exterior surface of the reinforced thermoplastic structure. 
     
     
         3 . The method of  claim 1 , wherein the predetermined outer shape comprises a preshape form, the method further comprising directing the partially solidified reinforced thermoplastic structure through a sizing die or calibrator to impart a final form to the structure. 
     
     
         4 . The method of  claim 1 , wherein the step of introducing said reinforcing filaments with the first thermoplastic resin into the first portion of a die further comprises providing the die with a filament channel sized and configured to receive the reinforcing filaments with the first thermoplastic resin, the filament channel further configured to direct the filaments to an introduction location of the second thermoplastic polymer within the die. 
     
     
         5 . The method of  claim 4 , further comprising the step of maintaining a temperature of an interior surface of the filament channel below the solidification temperature of the first polymer while the first polymer is located within the filament channel. 
     
     
         6 . The method of  claim 5 , wherein the filament channel has a proximal input end and a distal output end, and the distal output end is located adjacent to, or within, the second portion of the die, the distal output end being positioned to place the associated filaments at a predetermined cross-sectional location within the reinforced thermoplastic structure. 
     
     
         7 . The method of  claim 4 , further comprising providing a plurality of filament channels, the plurality of filament channels being positioned within the die to place the reinforcing filaments at predetermined locations adjacent the second portion of the die to produce a reinforced thermoplastic structure having a predetermined reinforcement scheme. 
     
     
         8 . The method of  claim 1 , wherein the second thermoplastic resin is introduced into the second portion of the die in a first flow direction, the first flow direction forming a first angle with respect to a movement direction of the reinforcing filament and the first thermoplastic resin through the die, and wherein the first angle is less than 90 degrees so that a component of the first flow direction is parallel to the movement direction. 
     
     
         9 . The method of  claim 2 , wherein the first thermoplastic resin comprises plastisol, and the second thermoplastic resin comprises polyvinylchloride which is introduced into the second portion of the die at melt state. 
     
     
         10 . The method of  claim 2 , wherein the third thermoplastic resin comprises an acrylic material which is introduced into the third portion of the die at melt state. 
     
     
         11 . The method of  claim 1 , further comprising using a first extruder to melt the second thermoplastic resin, and providing a quantity of reinforcing material into the first extruder with the second thermoplastic resin. 
     
     
         12 . The method of  claim 1 , wherein the first temperature is in the range of about 70° F. to about 250° F. and the second temperature is in the range of 300° F. to about 380° F. 
     
     
         13 . The method of  claim 1 , wherein the reinforcing filaments comprise a filament bundle. 
     
     
         14 . The method of  claim 1 , further comprising introducing the partially solidified reinforced thermoplastic structure into a mold cavity and forming a final form to the structure within the mold. 
     
     
         15 . A method for manufacturing a reinforced thermoplastic structure, comprising:
 providing a reinforcing filament;   wetting the reinforcing filament with a first thermoplastic resin;   introducing the reinforcing filament with the first thermoplastic resin into a first portion of a die and maintaining said thermoplastic resin at a first temperature;   introducing a second thermoplastic resin into a second portion of the die;   contacting the second thermoplastic resin with the reinforcing filament wetted by the first thermoplastic resin within the second portion of said die;   transporting the first and second thermoplastic polymer resins through the second portion of said die while forming the first and second thermoplastic polymer resins into a reinforced thermoplastic structure having a predetermined outer shape; and   exposing the reinforced thermoplastic structure to a zone having a second temperature;   wherein the first temperature is a temperature at which the first thermoplastic resin is in a stable liquid state and the second temperature is a value at which the first thermoplastic resin can at least partially solidify.   
     
     
         16 . The method of  claim 15 , further comprising contacting the at least partially solidified reinforced thermoplastic structure with a third thermoplastic resin to form a capping layer on an exterior surface of the reinforced thermoplastic structure. 
     
     
         17 . The method of  claim 15 , wherein the predetermined outer shape comprises a preshape form, the method further comprising directing the partially solidified reinforced thermoplastic structure through a sizing die or calibrator to impart a final form to the structure. 
     
     
         18 . The method of  claim 15 , wherein the step of introducing said reinforcing filament with the first thermoplastic resin into a first portion of a die further comprises providing the die with a filament channel sized and configured to receive the reinforcing filament with the first thermoplastic resin, the filament channel further configured to direct the filament to an introduction location of the second thermoplastic polymer within the die. 
     
     
         19 . The method of  claim 18 , further comprising the step of maintaining a temperature of an interior surface of the filament channel below an upper solidification temperature of the first polymer while the first polymer is located within the filament channel. 
     
     
         20 . A method for manufacturing a reinforced thermoplastic structure, comprising:
 providing a plurality of reinforcing filaments;   wetting the reinforcing filaments with a first thermoplastic resin;   introducing the reinforcing filaments with the first thermoplastic resin into a first portion of a die and maintaining said thermoplastic resin at a first temperature;   introducing a second thermoplastic resin into a second portion of the die;   contacting the second thermoplastic resin with the reinforcing filaments and the first thermoplastic resin within the second portion of said die;   heating the first and second thermoplastic polymer resins to a second temperature to form an at least partially solidified reinforced thermoplastic structure having a predetermined outer shape; and   contacting the reinforced thermoplastic structure with a third thermoplastic resin to form a capping layer on an exterior surface of the reinforced thermoplastic structure;   wherein the first temperature is a value below the solidification temperature of the first thermoplastic resin and the second temperature is a value above the solidification temperature of the first thermoplastic resin.