Gas-assisted co-injection molded chair

Abstract

The invention is directed to a method and article made from co-injection molding using gas-assist. The article has an inner material and an outer material. The inner material has a blowing agent uniformly distributed throughout the inner material. The outer material surrounds the inner material. At least one opening is provided in the outer material. The opening extends through the outer material to the inner material providing a pathway which allows out gas generated by the blowing agent in the inner material to escape through the outer material when the article is in a mold and after the article has been removed from the mold. The outer material provides an aesthetically pleasing outer surface and the inner material provides a strong core which is free of large voids, the inner and outer materials combining to form an article with a stable profile and repeatable size.

1 . A chair made from co-injection molding comprising:
 a thermoplastic inner material, the inner material having a blowing agent uniformly mixed therein and distributed throughout the inner material;   a thermoplastic outer material surrounding the inner material, the outer material having no blowing agent mixed therein, the outer material having a smooth finish;   at least one opening provided in the outer material, the opening extending through the outer material to the inner material providing a pathway which allows out gas generated by the blowing agent in the inner material to escape through the outer material when the chair is in a mold and after the chair has been removed from the mold;   whereby the outer material provides an aesthetically pleasing outer surface and the inner material provides a strong core which is free of large voids, the inner and outer materials combining to form an article with a stable profile and repeatable size.   
     
     
         2 . The chair as recited in  claim 1 , wherein the outer material does not have a blowing agent. 
     
     
         3 . The chair as recited in  claim 1 , wherein the blowing agent is an endothermic blowing agent. 
     
     
         4 . The chair as recited in  claim 1 , wherein the outer material is a synthetic thermoplastic resin. 
     
     
         5 . The chair as recited in  claim 1 , wherein the outer material is a glass-filled polypropylene copolymer. 
     
     
         6 . The chair as recited in  claim 1 , wherein the inner material is a synthetic thermoplastic resin. 
     
     
         7 . The chair as recited in  claim 1 , wherein the inner material is a glass-filled polypropylene copolymer. 
     
     
         8 . A co-injection molded article made by a process comprising:
 co-injection molding an outer material in a mold cavity;   co-injection molding an inner material in the mold cavity, the inner material including a blowing agent uniformly distributed therein;   injecting pressurized gas into the inner material in the mold cavity;   displacing the inner material including the blowing agent, to form a hollow channel inside the inner material;   providing a pathway which allows gas generated by the expansion of the blowing agent to be vented outside of the outer material;   removing the completed chair from the mold cavity;   maintaining the pathway as the chair is removed from the mold cavity;   wherein providing the pathway allows heat and pressure associated with the blowing agent to out gas as the chair is in the mold cavity and after the chair is removed from the mold cavity, thereby preventing the gas generated by the blowing agent from being trapped and minimizing the effects of post blow of the blowing agent.   
     
     
         9 . The co-injection molded article as recited in  claim 8 , wherein the outer material does not have a blowing agent, whereby the outer material provides an aesthetically pleasing outer surface. 
     
     
         10 . The co-injection molded article as recited in  claim 8 , wherein the blowing agent is an endothermic blowing agent. 
     
     
         11 . The co-injection molded article as recited in  claim 10 , wherein the blowing agent ranges from 0.1 to 1.00 volume percent of the inner material. 
     
     
         12 . The co-injection molded article as recited in  claim 8 , wherein the inner material ranges from 10 to 20% of the volume of the article. 
     
     
         13 . The co-injection molded article as recited in  claim 12 , wherein the first portion of the outer material ranges from 60 to 70% of the volume of the chair and the second portion of the outer material ranges from 10 to 30% of the volume of the chair. 
     
     
         14 . The co-injection molded article as recited in  claim 8 , wherein the co-injection  molded article is a chair. 
     
     
         15 . A co-injection molded article made by a process comprising:
 co-injection molding an outer material in a mold cavity;   co-injection molding an inner material in the mold cavity, the inner material having a blowing agent uniformly distributed therein;   displacing the inner material to form a hollow channel inside the inner material;   forming a pathway through the outer material and into the hollow channel of the inner material allowing gas generated by the expansion of the blowing agent to be vented outside of the outer material;   maintaining the pathway as the chair is removed from the mold cavity;   wherein forming the pathway allows out gas generated by the expanding of the blowing agent of the inner material to be vented through the outer material as the chair is in the mold cavity and after the chair is removed from the mold cavity;   whereby the outer material provides an aesthetically pleasing outer surface and the inner material provides a core which is free of large voids, the inner and outer materials combining to form an article with a stable profile and repeatable size.   
     
     
         16 . The co-injection molded article as recited in  claim 15 , wherein the outer material is a synthetic thermoplastic resin. 
     
     
         17 . The co-injection molded article as recited in  claim 15 , wherein the outer material is a glass-filled polypropylene copolymer. 
     
     
         18 . The co-injection molded article as recited in  claim 15 , wherein the inner material is a synthetic thermoplastic resin. 
     
     
         19 . The co-injection molded article as recited in  claim 15 , wherein the inner material is a glass-filled polypropylene copolymer. 
     
     
         20 . The co-injection molded article as recited in  claim 15 , wherein the co-injection molded article is a chair.