Polymer compositions, articles made from such compositions, and methods for molding such compositions

Abstract

A polymer composition comprises a thermoplastic polymer, a polymer additive selected from the group consisting of nucleating agents, clarifying agents, and combinations thereof, and a fluoropolymer. A molded article comprises at least one wall defining a cavity, the wall having an opening therein permitting access to the cavity. The wall comprises a polymer composition comprising a thermoplastic polymer, a polymer additive selected from the group consisting of nucleating agents, clarifying agents, and combinations thereof, and a fluoropolymer. A method for molding a polymer composition is also provided.

What is claimed is: 
     
         1 . A polymer composition comprising:
 (a) a thermoplastic polymer;   (b) a polymer additive selected from the group consisting of nucleating agents, clarifying agents, and combinations thereof; and   (c) a fluoropolymer, the fluoropolymer having a Melt Flow Index of about 4 to about 30 g/10 minutes as measured in accordance with ASTM D1238-04c at 265° C. using a 5 kg weight.   
     
     
         2 . The polymer composition of  claim 1 , wherein the thermoplastic polymer is a polyolefin. 
     
     
         3 . The polymer composition of  claim 2 , wherein the thermoplastic polymer is selected from the group consisting of polypropylene homopolymers, polypropylene copolymers, and combinations thereof. 
     
     
         4 . The polymer composition of  claim 3 , wherein the thermoplastic polymer is a polypropylene random copolymer. 
     
     
         5 . The polymer composition of  claim 1 , wherein the polymer additive is a clarifying agent comprising an acetal compound conforming to the structure of Formula (I) below: 
       
         
           
           
               
               
           
         
         wherein R 1  is selected from the group consisting of hydrogen, alkyl groups, alkenyl groups, hydroxyalkyl groups, alkoxy groups, and alkyl halide groups; wherein R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , R 10 , and R 11  are each independently selected from the group consisting of hydrogen, alkyl groups, alkoxy groups, alkenyl groups, aryl groups, and halogens; and wherein R 12  is a hydroxyalkyl group selected from the group consisting of —CH 2 OH and —CHOHCH 2 OH. 
       
     
     
         6 . The polymer composition of  claim 5 , wherein R 1  is selected from the group consisting of alkyl groups and alkenyl groups; R 2 , R 3 , R 5 , R 6 , R 7 , R 8 , R 10 , and R 11  are each hydrogen; R 12  is —CHOHCH 2 OH; and R 4  and R 9  are selected from the group consisting of alkyl groups and alkoxy groups. 
     
     
         7 . The polymer composition of  claim 6 , wherein R 1 , R 4  and R 9  are n-propyl groups. 
     
     
         8 . The polymer composition of  claim 1 , wherein the fluoropolymer is a polymer made from at least one monomer selected from the group consisting of vinylidene fluoride, hexafluoropropylene, chlorotrifluoroethylene, tetrafluoroethylene, perfluoro(alkyl vinyl ether), and combinations thereof. 
     
     
         9 . The polymer composition of  claim 8 , wherein the fluoropolymer is a polymer selected from the group consisting of (i) copolymers of vinylidene fluoride and a comonomer selected from the group consisting of hexafluoropropylene, chlorotrifluoroethylene, 1-hydropentafluoropropylene, and 2-hydropentafluoropropylene; (ii) terpolymers of vinylidene fluoride, tetrafluoroethylene, and a comonomer selected from the group consisting hexafluoropropylene, 1-hydropentafluoropropylene, and 2-hydropentafluoropropylene; (iii) copolymers of tetrafluoroethylene and propylene; (iv) copolymers of tetrafluoroethylene, propylene, and vinylidene fluoride; and (v) combinations of two or more of (i)-(iv). 
     
     
         10 . The polymer composition of  claim 9 , wherein the fluoropolymer is a terpolymer of vinylidene fluoride, tetrafluoroethylene, and hexafluoropropylene. 
     
     
         11 . The polymer composition of  claim 1 , wherein the fluoropolymer is present in the polymer composition in an amount of about 200 ppm or less, based on the total weight of the polymer composition. 
     
     
         12 . The polymer composition of  claim 1 , wherein the polymer composition is substantially free of interfacial agents. 
     
     
         13 . A method for molding a polymer composition, the method comprising the steps of:
 (a) providing an apparatus comprising a die and a mold cavity, the mold cavity having an interior surface defining a shape for a molded article;   (b) providing a polymer composition comprising (i) a thermoplastic polymer; (ii) a polymer additive selected from the group consisting of nucleating agents, clarifying agents, and combinations thereof; and (iii) a fluoropolymer, the fluoropolymer having a Melt Flow Index of about 4 to about 30 g/10 minutes as measured in accordance with ASTM D1238-04c at 265° C. using a 5 kg weight;   (c) heating the polymer composition to a temperature sufficient to melt the polymer composition so that it may be extruded through the die;   (d) extruding the molten polymer composition through the die to form a parison;   (e) capturing the parison in the mold cavity;   (f) blowing a pressurized fluid into the parison under sufficient pressure to inflate the parison so that it conforms to the interior surface of the mold cavity and produces a molded article;   (g) allowing the molded article to cool to a temperature at which the polymer composition at least partially solidifies so that the molded article retains its shape; and   (h) removing the molded article from the mold cavity.   
     
     
         14 . The method of  claim 13 , wherein the thermoplastic polymer is a polyolefin. 
     
     
         15 . The method of  claim 14 , wherein the thermoplastic polymer is selected from the group consisting of polypropylene homopolymers, polypropylene copolymers, and combinations thereof. 
     
     
         16 . The method of  claim 15 , wherein the thermoplastic polymer is a polypropylene random copolymer. 
     
     
         17 . The method of  claim 13 , wherein the polymer additive is a clarifying agent comprising an acetal compound conforming to the structure of Formula (I) below: 
       
         
           
           
               
               
           
         
         wherein R 1  is selected from the group consisting of hydrogen, alkyl groups, alkenyl groups, hydroxyalkyl groups, alkoxy groups, and alkyl halide groups; wherein R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , R 10 , and R 11  are each independently selected from the group consisting of hydrogen, alkyl groups, alkoxy groups, alkenyl groups, aryl groups, and halogens; and wherein R 12  is a hydroxyalkyl group selected from the group consisting of —CH 2 OH and —CHOHCH 2 OH. 
       
     
     
         18 . The method of  claim 17 , wherein R 1  is selected from the group consisting of alkyl groups and alkenyl groups; R 2 , R 3 , R 5 , R 6 , R 7 , R 8 , R 10 , and R 11  are each hydrogen; R 12  is —CHOHCH 2 OH; and R 4  and R 9  are selected from the group consisting of alkyl groups and alkoxy groups. 
     
     
         19 . The method of  claim 18 , wherein R 1 , R 4  and R 9  are n-propyl groups. 
     
     
         20 . The method of  claim 13 , wherein the fluoropolymer is a polymer made from at least one monomer selected from the group consisting of vinylidene fluoride, hexafluoropropylene, chlorotrifluoroethylene, tetrafluoroethylene, perfluoro(alkyl vinyl ether), and combinations thereof. 
     
     
         21 . The method of  claim 20 , wherein the fluoropolymer is a polymer selected from the group consisting of (i) copolymers of vinylidene fluoride and a comonomer selected from the group consisting of hexafluoropropylene, chlorotrifluoroethylene, 1-hydropentafluoropropylene, and 2-hydropentafluoropropylene; (ii) terpolymers of vinylidene fluoride, tetrafluoroethylene, and a comonomer selected from the group consisting hexafluoropropylene, 1-hydropentafluoropropylene, and 2-hydropentafluoropropylene; (iii) copolymers of tetrafluoroethylene and propylene; (iv) terpolymers of tetrafluoroethylene, propylene, and vinylidene fluoride; and (v) combinations of two or more of (i)-(iv). 
     
     
         22 . The method of  claim 21 , wherein the fluoropolymer is a terpolymer of vinylidene fluoride, tetrafluoroethylene, and hexafluoropropylene. 
     
     
         23 . The method of  claim 13 , wherein the fluoropolymer is present in the polymer composition in an amount of about 200 ppm or less, based on the total weight of the polymer composition. 
     
     
         24 . The method of  claim 13 , wherein the polymer composition is substantially free of interfacial agents.