Thermoforming system for masked polymers

Abstract

In a thermoforming system for masked polymer substrate sheets, a temperature resistant, non-stick coating is applied to a sheet of a polymer substrate material. The coated sheet is positioned on a flexible platen positioned over a mold having a predetermined shape. Heat is applied until the polymer reaches a thermoforming temperature and softens, whereupon the platen is lowered to stretch over and cover the mold. When the sheet begins to conform to the mold, the heat is withdrawn and a second platen is lowered over the sheet to urge it into conformance with the mold. The temperature resistant coating can be applied over an existing polymer film masking, and rapidly cures to form a non-stick surface which prevents adhesion of the masked polymer sheet to the platen surfaces.

1 . A system for thermoforming a polymer sheet, comprising: 
 a) a mold having a predetermined shape;    b) a platen including a flexible web for supporting the polymer sheet adjacent said mold, said platen being movable toward said mold for stretching said web over and covering said mold surface to thereby engage said sheet with said mold;    c) a heat generating source for heating the polymer sheet so that it softens to conform to said mold shape; and    d) a coating composition for coating the polymer sheet to facilitate release of the sheet from said platen.    
     
     
         2 . The system as set forth in  claim 1 , further including: 
 a second platen in spaced relation to said platen supporting the polymer sheet, said second platen including a second flexible web and being movable toward said mold for stretching said second web over and urging said polymer sheet into conformance with said mold.    
     
     
         3 . The system as set forth in  claim 1 , wherein said flexible web further comprises: 
 a. a first, stretchable, mold contacting layer;    b. a second, polymer sheet contacting layer; and    c. said first layer having a greater modulus of elasticity than said second layer.    
     
     
         4 . The system as set forth in  claim 2 , wherein said heat generating source is mounted for reciprocal positioning over said polymer sheet.  
     
     
         5 . The system as set forth in  claim 1 , wherein said coating composition exhibits non-stick characteristics with respect to a contacting surface of said sheet.  
     
     
         6 . The system as set forth in  claim 5 , wherein said coating composition is capable of resisting thermoforming temperatures of up to about 370° F.  
     
     
         7 . The system as set forth in  claim 1 , wherein said coating composition is an essentially water free mixture comprising: 
 a. silicone; and    b. organic solvents.    
     
     
         8 . The system as set forth in  claim 7 , wherein said coating composition further includes silica.  
     
     
         9 . A method of thermoforming a polymer sheet, comprising the steps of: 
 a. positioning the coated polymer sheet on a stretchable web supported by a platen positioned in spaced relation to a mold;    b. heating the coated polymer sheet to a thermoformable temperature; and    c. lowering said platen over said mold to effectively engage said sheet with said mold to thereby enable said polymer sheet to conform to said mold.    
     
     
         10 . A method of thermoforming as set forth in  claim 9 , further including the step of: 
 a. coating the polymer sheet with a heat resistant quick release composition.    
     
     
         11 - 19 . (Canceled)  
     
     
         20 . A protectively masked thermoformable polymer composition, comprising: 
 a) a thermoformable polymer sheet having a first surface and an opposite second surface;    b) first and second polymer laminate layers coupled with said respective first and second surfaces; and    c) first and second heat resistant, non-stick coatings bonded to said first and second polymer laminate layers.    
     
     
         21 . The thermoformable polymer composition as set forth in  claim 20 , wherein: 
 a. said first and second heat resistant, non-stick coating coatings include a mixture of silicone and organic solvents.    
     
     
         22 . (Canceled)  
     
     
         23 . The thermoformable polymer composition as set forth in  claim 20 , wherein said heat resistant, non-stick coatings comprise a solution including a solvating quantity of an organic solvent mixed with a quantity of a polymer selected from the group consisting essentially of silanes, silicones, siloxane, acrylic resins, polytetrafluoroethylene, epoxies, polyesters, urethanes, allyl resins, amino resins and phenolic resins.  
     
     
         24 . The thermoformable polymer composition as set forth in  claim 20 , where said heat resistant, non-stick coating coatings comprises comprise a ceramic material.  
     
     
         25 . The thermoformable polymer composition as set forth in  claim 20 , wherein: 
 a. said heat resistant, non-stick coating has a thickness of from about 0.0005 inches to about 0.005 inches.