Method of manufacturing polystyrene foam with polymer processing additives

Abstract

Disclosed is a method for making polystyrene foam which utilizes one or more atmospheric gases, particularly CO 2 , as the blowing agent in combination with a polymer processing aid (PPA), typically an ester that is relatively non-volatile at the extrusion temperature range. The blowing agent and the PPA may both be introduced into the molten thermoplastic polystyrene resin or the PPA may be incorporated in the solid source polystyrene resins. The resulting foam will be substantially free of residual blowing agent and dimensionally stable at ambient temperatures.

1 . A method of manufacturing expanded polymeric foam, comprising: 
 preparing a polymeric melt from a major amount of a polymer composition having melt flow index of at least 10 and a minor amount of at least one adipate according to Formula I;                          wherein R 1  and R 2  are independently selected from at least one of hydrogen, C 6 -C 16  aliphatic and C 6 -C 16  aromatic groups;    injecting CO 2  into the polymeric melt to form a foamable mixture; and    ejecting the foamable mixture through a die into a region of reduced pressure.    
     
     
         2 . A method of manufacturing expanded polymeric foam according to  claim 1 , wherein: 
 the polymer composition is substantially all polystyrene.    
     
     
         3 . A method of manufacturing expanded polymeric foam according to  claim 1 , wherein: 
 the polymer composition includes a major portion of polystyrene.    
     
     
         4 . A method of manufacturing expanded polymeric foam according to  claim 1 , wherein: 
 the CO 2  represents at least about 2% by weight of the foamable mixture.    
     
     
         5 . A method of manufacturing expanded polymeric foam according to  claim 1 , wherein: 
 the CO 2  represents at least about 3.5% by weight of the foamable mixture.    
     
     
         6 . A method of manufacturing expanded polymeric foam according to  claim 1 , wherein: 
 R 1  and R 2  are Independently selected from at least one of hydrogen, C 8 -C 13      
     
     
         7 . A method of manufacturing expanded polymeric foam according to  claim 1 , wherein: 
 the adipate represents no more than about 5.0% by weight of the foamable one of:                          
     
     
         8 . A method of manufacturing expanded polymeric foam according to  claim 1 , wherein: 
 the reduced pressure is between about 101.3 kPa and about 47.3 kPa.    
     
     
         9 . A method of manufacturing expanded polymeric foam according to  claim 1 , wherein: 
 the polymer composition includes a major portion of polystyrene;    the CO 2  represents about 3.7% by weight of the foamable mixture;    the adipate represents no more than about 2.0% by weight of the foamable mixture and includes a major portion of bis(n-decanyl) adipate:                          the reduced pressure is between about 101.3 kPa and about 47.3 kPa; and    the resulting expanded foam has an average cell size of less than about 0.2 mm, a compressive modulus of no more than about 7 MPa (1000 psi).    
     
     
         10 . A method of manufacturing expanded polymeric foam, comprising: 
 preparing a polymeric melt from a major amount of a polymer composition having melt flow index of at least 10 and a minor amount of at least one additive selected from a group of compounds represented by the formulas                          wherein:    X is selected from a group consisting of O and N;    R 1  is selected from at least one of C 1 -C 20  alkyl, aryl or alkaryl;    R 2  and R 3  are independently selected from at least one of hydrogen, C 1 -C 20  alkyl, aryl, alkaryl and alkoxylate groups, wherein only one of R 2  and R 3  can be H;    R 4  and R 5  are selected from at least one of hydrogen, C 1 -C 20  alkyl, aryl, alkaryl and alkoxylate groups;    injecting CO 2  into the polymeric melt to form a foamable mixture; and    ejecting the foamable mixture through a die into a region of reduced pressure.    
     
     
         11 . A method of manufacturing expanded polymeric foam according to  claim 10 , wherein: 
 the polymer composition is substantially all polystyrene.    
     
     
         12 . A method of manufacturing expanded polymeric foam according to  claim 10 , wherein: 
 the polymer composition includes a major portion of polystyrene.    
     
     
         13 . A method of manufacturing expanded polymeric foam according to  claim 10 , wherein: 
 the CO 2  represents at least about 2% by weight of the foamable mixture.    
     
     
         14 . A method of manufacturing expanded polymeric foam according to  claim 10 , wherein: 
 the CO 2  represents at least about 3.5% by weight of the foamable mixture.    
     
     
         15 . A method of manufacturing expanded polymeric foam according to  claim 10 , wherein: 
 R 1  is selected from at least one of hydrogen, C 8 -C 13  aliphatic and aromatic groups.    
     
     
         16 . A method of manufacturing expanded polymeric foam according to  claim 10 , wherein: 
 the additive represents no more than about 5.0% by weight of the foamable mixture and is selected from at least one of:                          
     
     
         16 . A method of manufacturing expanded polymeric foam according to  claim 10 , wherein: 
 the reduced pressure is between about 101.3 kPa and about 47.3 kPa.    
     
     
         17 . A method of manufacturing expanded polymeric foam according to  claim 10 , wherein: 
 the additive represents no more than about 5.0% by weight of the foamable mixture and is selected from at least one of:                          
     
     
         18 . A method of manufacturing expanded polymeric foam according to  claim 10 , wherein: 
 the additive represents no more than about 5.0% by weight of the foamable mixture and is selected from at least one of:                          
     
     
         19 . A foam board manufactured by the process of  claim 1.