Polyvinyl chloride plastic film
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to plastic polymeric films formed from polyvinyl chloride homopolymers and copolymers. 
     2. Description of Prior Art 
     West German patent specification No. DE-GMS 8220682 describes a plastic film that has a very low or no plasticizer content. This film consists of two layers, is capable of being deep drawn, and is useful in automobile interiors. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to create a plastic film formed from polyvinyl chloride homopolymers and/or copolymers and olefinic unsaturated monomers that has improved strength, rubber-like properties, low temperature characteristics and resistance to aging. 
     It is a specific purpose of the present invention to provide a plastic film having a portion of thermoplastic rubber present in an amount by weight of preferably about 1% to about 10%, most preferably about 3%. The thermoplastic rubber renders it unnecessary to use external plasticizers that, because of their volatility or migrating characteristics, lead to the deterioration of the desirable properties of the plastic, namely low temperature behavior, resistance to aging and flexibility. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Ethylene propylene terpolymer rubber is useful as the thermoplastic rubber, preferably precipitated out of solution. But styrene butadiene rubber or styrene rubber styrene block polymers can also be used. It is advantageous if the rubber has rubber blocks free of double bonds. In this case it is a styrene ethylene butylene styrene block polymer. 
     An ethylene vinyl acetate carbon monoxide terpolymer can be used as an effective plasticizing agent. Also, processing aids such as antioxidants and stabilizers can constitute a portion of the overall formula as is well known in the art. 
     EXAMPLE 1 
     Starting mixture: polyvinyl chloride homopolymer 77.6% by weight; ethylene vinyl acetate carbon monoxide terpolymer 19.4% by weight; and processing aids 3.0% by weight. 
     This mixture was calendared for 10 minutes at 110° C. 3.0% by weight of cold ethylene propylene terpolymer rubber was added to the mixture. From this, at 165° C. with a working time of 7 minutes, plastic films were produced having the following mechanical values: 
     
         ______________________________________                                    
               Measurement                                                
                        Measurement                                       
               after 4 hours                                              
                        after 24 hours                                    
______________________________________                                    
Tensile strength (N)                                                      
                 350        346                                           
Breaking elongation (mm).sup.1                                            
                 130        134                                           
Breaking elongation (%)                                                   
                 220        235                                           
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 .sup.1 The point of the curve in the tension/elongation diagram where    
 breaking takes place.                                                    
 
    
     EXAMPLE 2 
     The same starting mixture was used as in Example 1, but instead of the ethylene propylene terpolymer rubber, 3% by weight styrene butadiene rubber was added. In this case the following mechanical values were obtained: 
     
         ______________________________________                                    
               Measurement                                                
                        Measurement                                       
               after 4 hours                                              
                        after 24 hours                                    
______________________________________                                    
Tensile strength (N)                                                      
                 320        320                                           
Breaking elongation (mm)                                                  
                 120        120                                           
Breaking elongation (%)                                                   
                 200        196                                           
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     EXAMPLE 3 
     A basic starting mixture as in Examples 1 and 2 was used, but 3% by weight of styrene rubber styrene block polymer was added, giving the following values: 
     
         ______________________________________                                    
               Measurement                                                
                        Measurement                                       
               after 4 hours                                              
                        after 24 hours                                    
______________________________________                                    
Tensile strength (N)                                                      
                 390        354                                           
Breaking elongation (mm)                                                  
                 136        135                                           
Breaking elongation (%)                                                   
                 240        239                                           
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