Co-injection molding of the structural portion of a vehicle liftgate inner panel

Abstract

A thermoplastic liftgate inner panel construction is provided by using a co-injected injection molding process. In a first phase, a class A surface material is injected into the molds and thereafter in a second phase an inner core of material is injected using a gas-infused reinforced polymer.

What is claimed is: 
     
         1 . A thermoplastic vehicle body closure panel for a vehicle comprising:
 an outer surface layer of a thermoplastic injection moldable material having a class A forming surface on at least part of said thermoplastic vehicle body closure panel; and   at least one structural member substantially filled with a foam core.   
     
     
         2 . The thermoplastic vehicle body closure panel of  claim 1 , wherein the foamed core includes microcellular spaces for reducing weight and providing structural support. 
     
     
         3 . A process for manufacture of a thermoplastic vehicle body closure panel comprising:
 providing a mold having at least part thereof capable of forming a Class A surface and configured for injection of a supercritical fluid into predetermined class A areas of the molded liftgate inner panel;   providing an injection moldable thermoplastic material; and   injection molding the thermoplastic vehicle body closure panel structure from said thermoplastic material in a first step with injection of a combination of said supercritical fluid and a second thermoplastic material into said predetermined areas of said mold after the class A surface of the mold is pre-covered in thermoplastic material.   
     
     
         4 . The process for manufacture of a thermoplastic vehicle body closure panel of  claim 3 , wherein a sequential valve gate mold is used for the process. 
     
     
         5 . The process for manufacture of a thermoplastic vehicle body closure panel of  claim 4 , wherein a two shot nozzle is used. 
     
     
         6 . The process for manufacture of a thermoplastic vehicle body closure panel of  claim 4 , wherein virgin show surface thermoplastic is injected first at a first portion of the mold and said second thermoplastic material is injected at a separate location along with said supercritical fluid. 
     
     
         7 . The process for manufacture of a thermoplastic vehicle body closure panel of  claim 3 , wherein said thermoplastic is a virgin thermoplastic resin. 
     
     
         8 . The process for manufacture of a thermoplastic vehicle body closure panel of  claim 3 , wherein the part produced is greater than 3 mm thick at all areas of the part. 
     
     
         9 . The process for manufacture of a thermoplastic vehicle body closure panel of  claim 3 , wherein the part is produced to be from 4-6 mm thick. 
     
     
         10 . The process for manufacture of a thermoplastic vehicle body closure panel of  claim 3 , further comprising molding a continuously molded structure including at least a first cosmetic area, a second structural area and a third attachment area, and wherein said second structural area and third attachment area are said predetermined areas for injection of said supercritical fluid and said second thermoplastic material. 
     
     
         11 . A thermoplastic vehicle body closure panel for a vehicle comprising:
 a continuously molded structure including at least a first cosmetic area, a second structural area and a third attachment area,   each of said first second and third areas having a thickness of greater than 3 mm and including an outer surface of a thermoplastic injection moldable material having a class A forming surface on at least part of said liftgate inner panel and substantially filled with a micro cellular enhanced foam core.   
     
     
         12 . The thermoplastic vehicle body closure panel of  claim 11 , wherein the foamed core includes microcellular spaces for reducing weight and providing structural support at least in the third attachment and second structural areas. 
     
     
         13 . The thermoplastic vehicle body closure panel of  claim 11 , wherein the panel has a thickness of from about 5-6 mm throughout. 
     
     
         14 . The thermoplastic vehicle body closure panel of  claim 11 , wherein said part is selected from the group comprising an inner liftgate panel and a rear truck tailgate. 
     
     
         15 . The thermoplastic vehicle body closure panel of  claim 11 , wherein said part includes at least an outer show surface of a virgin polymer material and inner microcellular structural core of a long glass fiber reinforced thermoplastic material. 
     
     
         16 . The thermoplastic vehicle body closure panel of  claim 15 , wherein said reinforced thermoplastic material is a polyolefin which is from about 30% to about 40% filled with 12 mm glass fibers which are reduced to from about 1-4 mm length fibers during the injection process. 
     
     
         17 . A process for manufacture of a thermoplastic vehicle body closure panel comprising:
 providing a mold having at least part thereof capable of forming a Class A surface and configured for injection of a supercritical fluid into predetermined class A areas of the molded liftgate inner panel;   providing an injection moldable thermoplastic material; and   injection molding the thermoplastic vehicle body closure panel structure from said thermoplastic material in a first step with injection of a combination of said supercritical fluid and a second thermoplastic material into said predetermined areas of said mold after the class A surface of the mold is pre-covered in thermoplastic material with the mold closed in a dimension of from about  2  to about  3  mm part thickness and thereafter releasing the pressure on the mold cavity and allowing controlled parallel expansion of the mold during the microcellular foam expansion to provide a final part thickness of from about 4 mm to 6 mm.   
     
     
         18 . The process for manufacture of thermoplastic vehicle body closure panel of  claim 17 , wherein a sequential valve gate mold and a press having leveling on four corners of the mold for allowing parallel controlled mold expansion is used for the process. 
     
     
         19 . The process for manufacture of thermoplastic vehicle body closure panel of  claim 18 , wherein a two shot nozzle is used. 
     
     
         20 . The process for manufacture of thermoplastic vehicle body closure panel of  claim 19 , wherein virgin show surface thermoplastic is injected first at a first portion of the mold and said second thermoplastic material is injected at a separate location along with said supercritical fluid. 
     
     
         21 . The process for manufacture of a thermoplastic vehicle body closure panel of  claim 17 , wherein said thermoplastic is a virgin thermoplastic resin. 
     
     
         22 . The process for manufacture of a thermoplastic vehicle body closure panel of  claim 17 , wherein the part produced is greater than 3 mm thick at all areas of the part. 
     
     
         23 . The process for manufacture of a thermoplastic vehicle body closure panel of  claim 17 , wherein the part is produced to be from 4-6 mm thick. 
     
     
         24 . The process for manufacture of a thermoplastic vehicle body closure panel of  claim 17 , further comprising molding a continuously molded structure including at least a first cosmetic area, a second structural area and a third attachment area, and wherein said second structural area and third attachment area are said predetermined areas for injection of said supercritical fluid and said second thermoplastic material.