Thermoplastic elastomer composition for core back type injection foaming and injection foaming method using the same

Abstract

The thermoplastic elastomer composition of the present invention comprises a thermoplastic elastomer which includes an ethylene•α-olefin copolymer and a crystalline polyethylene resin, wherein the crystalline polyethylene resin constitutes a three-dimensional network structure in a matrix formed by the ethylene•α-olefin copolymer, an organic or inorganic blowing agent and a nucleating agent, wherein the thermoplastic elastomer has a melt flow rate of 5 g/10 min or more at a temperature of 230° C. and a load of 10 kg, and a melt tension of 3.0 gf or more at a temperature of 210° C. and a pulling rate of 2 m/min. Also the foam injection molding method of the present invention is a method comprising of injecting the above-mentioned composition into a cavity space of a metal mold and then expanding the cavity space to foam by opening the metal mold at a mold opening rate of 0.05 to 0.4 mm/sec.

1 . A thermoplastic elastomer composition for core-back system foam injection molding, comprising a thermoplastic elastomer which includes an ethylene•α-olefin-based copolymer ( 1 ) and a crystalline polyethylene-based resin ( 2 ), wherein said crystalline polyethylene-based resin ( 2 ) constitutes a three-dimensional network structure in a matrix formed by said ethylene•α-olefin-based copolymer ( 1 ), a blowing agent ( 4 ) and a nucleating agent ( 5 ), 
 wherein said thermoplastic elastomer has a melt flow rate of 5 g/10 min or more at a temperature of 230° C. and a load of 10 kg, and a melt tension of 3.0 gf or more at a temperature of 210° C. and a pulling rate of 2 m/min; and    characterized by said thermoplastic elastomer composition for core-back system foam injection molding is injected into a cavity space of a metal mold and is foamed by opening the metal mold thereby expanding said cavity space to form an injection foaming product having a skin layer and a foamed layer.    
     
     
         2 . The thermoplastic elastomer composition for core-back system foam injection molding according to  claim 1 , wherein said nucleating agent ( 5 ) is an inorganic compound powder of a particle diameter of 2 to 50 μm, and said blowing agent ( 4 ) is at least one selected from the group consisting of sodium hydrogencarbonate, ammonium hydrogencarbonate, ammonium chloride and ammonium carbonate, and said composition further comprises at least a weakly acidic compound selected from the group consisting of oxalic acid, malonic acid, citric acid, lactic acid, boric acid, monosodium citrate and acidic potassium tartrate.  
     
     
         3 . A thermoplastic elastomer composition for core-back system foam injection molding, comprising a thermoplastic elastomer which includes an ethylene•α-olefin-based copolymer ( 1 ) and a crystalline polyethylene-based resin ( 2 ), wherein said crystalline polyethylene-based resin ( 2 ) constitutes a three-dimensional network structure in a matrix formed by said ethylene•α-olefin-based copolymer ( 1 ); 
 a blowing agent-containing resin in which a blowing agent ( 4 ) is kneaded in an olefin resin ( 6 ); and    a nucleating agent-containing resin in which a nucleating agent ( 5 ) is kneaded in an olefin resin ( 6 );    wherein said thermoplastic elastomer has a melt flow rate of 5 g/10 min or more at a temperature of 230° C. and a load of 10 kg, and a melt tension of 3.0 gf or more at a temperature of 210° C. and a pulling rate of 2 m/min; and    characterized by said thermoplastic elastomer composition for core-back system foam injection molding is injected into a cavity space of a metal mold and is foamed by opening the metal mold thereby expanding said cavity space to form an injection foaming product having a skin layer and a foamed layer.    
     
     
         4 . The thermoplastic elastomer composition for core-back system foam injection molding according to  claim 3 , wherein said nucleating agent ( 5 ) is an inorganic compound powder of a particle diameter of 2 to 50 μm, and said blowing agent ( 4 ) is at least one selected from the group consisting of sodium hydrogencarbonate, ammonium hydrogencarbonate, ammonium chloride and ammonium carbonate, and said composition further comprises at least a weakly acidic compound selected from the group consisting of oxalic acid, malonic acid, citric acid, lactic acid, boric acid, monosodium citrate and acidic potassium tartrate.  
     
     
         5 . A thermoplastic elastomer composition for core-back system foam injection molding, comprising a thermoplastic elastomer which includes an ethylene α-olefin-based copolymer ( 1 ), a crystalline polyethylene-based resin ( 2 ) and a following block copolymer ( 3 ), wherein said crystalline polyethylene-based resin ( 2 ) and said block copolymer ( 3 ) constitute a three-dimensional network structure in a matrix formed by said ethylene•α-olefin-based copolymer ( 1 ), a blowing agent ( 4 ) and a nucleating agent ( 5 ); 
 wherein said thermoplastic elastomer has a melt flow rate of 5 g/10 min or more at a temperature of 230° C. and a load of 10 kg, and a melt tension of 3.0 gf or more at a temperature of 210° C. and a pulling rate of 2 m/min;    said block copolymer ( 3 ) is a block copolymer having a crystalline ethylene polymer block and a block having a higher compatibility to said ethylene α-olefin-based copolymer ( 1 ) than to said crystalline polyethylene-based resin ( 2 ); and    characterized by said thermoplastic elastomer composition for core-back system foam injection molding is injected into a cavity space of a metal mold and is foamed by opening the metal mold thereby expanding said cavity space to form an injection foaming product having a skin layer and a foamed layer.    
     
     
         6 . The thermoplastic elastomer composition for core-back system foam injection molding according to  claim 5 , wherein said nucleating agent ( 5 ) is an inorganic compound powder of a particle diameter of 2 to 50 μm, and said blowing agent ( 4 ) is at least one selected from the group consisting of sodium hydrogencarbonate, ammonium hydrogencarbonate, ammonium chloride and ammonium carbonate, and said composition further comprises at least a weakly acidic compound selected from the group consisting of oxalic acid, malonic acid, citric acid, lactic acid, boric acid, monosodium citrate and acidic potassium tartrate.  
     
     
         7 . A thermoplastic elastomer composition for core-back system foam injection molding, comprising a thermoplastic elastomer which includes an ethylene•α-olefin-based copolymer ( 1 ), a crystalline polyethylene-based resin ( 2 ) and a following block copolymer ( 3 ), wherein said crystalline polyethylene-based resin ( 2 ) and said block copolymer ( 3 ) constitute a three-dimensional network structure in a matrix formed by said ethylene•α-olefin-based copolymer ( 1 ); 
 a blowing agent-containing resin in which a blowing agent ( 4 ) is kneaded in an olefin resin ( 6 ); and    a nucleating agent-containing resin in which a nucleating agent ( 5 ) is kneaded in an olefin resin ( 6 );    wherein said thermoplastic elastomer has a melt flow rate of 5 g/10 min or more at a temperature of 230° C. and a load of 10 kg, and a melt tension of 3.0 gf or more at a temperature of 210° C. and a pulling rate of 2 m/min;    said block copolymer ( 3 ) is a block copolymer having a crystalline ethylene polymer block and a block having a higher compatibility to said ethylene•α-olefin-based copolymer ( 1 ) than to said crystalline polyethylene-based resin ( 2 ); and    characterized by said thermoplastic elastomer composition for core-back system foam injection molding is injected into a cavity space of a metal mold and is foamed by opening the metal mold thereby expanding said cavity space to form an injection foaming product having a skin layer and a foamed layer.    
     
     
         8 . The thermoplastic elastomer composition for core-back system foam injection molding according to  claim 7 , wherein said nucleating agent ( 5 ) is an inorganic compound powder of a particle diameter of 2 to 50 μm, and said blowing agent ( 4 ) is at least one selected from the group consisting of sodium hydrogencarbonate, ammonium hydrogencarbonate, ammonium chloride and ammonium carbonate, and said composition further comprises at least a weakly acidic compound selected from the group consisting of oxalic acid, malonic acid, citric acid, lactic acid, boric acid, monosodium citrate and acidic potassium tartrate.  
     
     
         9 . A thermoplastic elastomer composition for core-back system foam injection molding, comprising a thermoplastic elastomer which includes an ethylene•α-olefin-based copolymer ( 1 ) and a crystalline polyethylene-based resin ( 2 ), wherein said crystalline polyethylene-based resin ( 2 ) constitutes a three-dimensional network structure in a matrix formed by said ethylene•α-olefin-based copolymer ( 1 ), an organic blowing agent ( 4   a ), an inorganic blowing agent ( 4   b ) and a nucleating agent ( 5 ); 
 wherein said thermoplastic elastomer has a melt flow rate of 5 g/10 min or more at a temperature of 230° C. and a load of 10 kg, and a melt tension of 3.0 gf or more at a temperature of 210° C. and a pulling rate of 2 m/min; and    characterized by said thermoplastic elastomer composition for core-back system foam injection molding is injected into a cavity space of a metal mold and is foamed by opening the metal mold thereby expanding said cavity space to form an injection foaming product having a skin layer and a foamed layer.    
     
     
         10 . The thermoplastic elastomer composition for core-back system foam injection molding according to  claim 9 , wherein said nucleating agent ( 5 ) is an inorganic compound powder of a particle diameter of 2 to 50 μm, said organic blowing agent ( 4   a ) is at least one selected from the group consisting of an azo-based blowing agent, a nitroso-based blowing agent, a sulfonyl hydrazide-based blowing agent, a triazine-based blowing agent and a tetrazole-based blowing agent, said inorganic blowing agent ( 4   b ) is at least one selected from the group consisting of sodium hydrogencarbonate, ammonium hydrogencarbonate, ammonium chloride and ammonium carbonate, and said composition further comprises at least a weakly acidic compound selected from the group consisting of oxalic acid, malonic acid, citric acid, lactic acid, boric acid, monosodium citrate and acidic potassium tartrate.  
     
     
         11 . A thermoplastic elastomer composition for core-back system foam injection molding, comprising a thermoplastic elastomer which includes an ethylene•α-olefin-based copolymer ( 1 ) and a crystalline polyethylene-based resin ( 2 ), wherein said crystalline polyethylene-based resin ( 2 ) constitutes a three-dimensional network structure in a matrix formed by said ethylene•α-olefin-based copolymer ( 1 ); 
 (i) an organic blowing agent-containing resin in which an organic blowing agent ( 4   a ) is kneaded in an olefin resin ( 6 ) and an inorganic blowing agent-containing resin in which an inorganic blowing agent ( 4   b ) is kneaded in an olefin resin ( 6 ), or (ii) an organic/inorganic blowing agent-containing resin in which an organic blowing agent ( 4   a ) and an inorganic blowing agent ( 4   b ) are kneaded in an olefin resin ( 6 ); and    a nucleating agent-containing resin in which a nucleating agent ( 5 ) is kneaded in an olefin resin ( 6 );    wherein said thermoplastic elastomer has a melt flow rate of 5 g/10 min or more at a temperature of 230° C. and a load of 10 kg, and a melt tension of 3.0 gf or more at a temperature of 210° C. and a pulling rate of 2 m/min; and    characterized by said thermoplastic elastomer composition for core-back system foam injection molding is injected into a cavity space of a metal mold and is foamed by opening the metal mold thereby expanding said cavity space to form an injection foaming product having a skin layer and a foamed layer.    
     
     
         12 . The thermoplastic elastomer composition for core-back system foam injection molding according to  claim 11 , wherein said nucleating agent ( 5 ) is an inorganic compound powder of a particle diameter of 2 to 50 μm, said organic blowing agent ( 4   a ) is at least one selected from the group consisting of an azo-based blowing agent, a nitroso-based blowing agent, a sulfonyl hydrazide-based blowing agent, a triazine-based blowing agent and a tetrazole-based blowing agent, said inorganic blowing agent ( 4   b ) is at least one selected from the group consisting of sodium hydrogencarbonate, ammonium hydrogencarbonate, ammonium chloride and ammonium carbonate, and said composition further comprises at least a weakly acidic compound selected from the group consisting of oxalic acid, malonic acid, citric acid, lactic acid, boric acid, monosodium citrate and acidic potassium tartrate.  
     
     
         13 . A thermoplastic elastomer composition for core-back system foam injection molding, comprising a thermoplastic elastomer which includes an ethylene•α-olefin-based copolymer ( 1 ), a crystalline polyethylene-based resin ( 2 ) and a following block copolymer ( 3 ), wherein said crystalline polyethylene-based resin ( 2 ) and said block copolymer ( 3 ) constitute a three-dimensional network structure in a matrix formed by said ethylene•α-olefin-based copolymer ( 1 ), an organic blowing agent ( 4   a ), an inorganic blowing agent ( 4   b ) and a nucleating agent ( 5 ); 
 wherein said thermoplastic elastomer has a melt flow rate of 5 g/10 min or more at a temperature of 230° C. and a load of 10 kg, and a melt tension of 3.0 gf or more at a temperature of 210° C. and a pulling rate of 2 m/min;    said block copolymer ( 3 ) is a block copolymer having a crystalline ethylene polymer block and a block having a higher compatibility to said ethylene•α-olefin-based copolymer ( 1 ) than to said crystalline polyethylene-based resin ( 2 ); and    characterized by said thermoplastic elastomer composition for core-back system foam injection molding is injected into a cavity space of a metal mold and is foamed by opening the metal mold thereby expanding said cavity space to form an injection foaming product having a skin layer and a foamed layer.    
     
     
         14 . The thermoplastic elastomer composition for core-back system foam injection molding according to  claim 13 , wherein said nucleating agent ( 5 ) is an inorganic compound powder of a particle diameter of 2 to 50 μm, said organic blowing agent ( 4   a ) is at least one selected from the group consisting of an azo-based blowing agent, a nitroso-based blowing agent, a sulfonyl hydrazide-based blowing agent, a triazine-based blowing agent and a tetrazole-based blowing agent, said inorganic blowing agent ( 4   b ) is at least one selected from the group consisting of sodium hydrogencarbonate, ammonium hydrogencarbonate, ammonium chloride and ammonium carbonate, and said composition further comprises at least a weakly acidic compound selected from the group consisting of oxalic acid, malonic acid, citric acid, lactic acid, boric acid, monosodium citrate and acidic potassium tartrate.  
     
     
         15 . A thermoplastic elastomer composition for core-back system foam injection molding, comprising a thermoplastic elastomer which includes an ethylene•α-olefin-based copolymer ( 1 ), a crystalline polyethylene-based resin ( 2 ) and a following block copolymer ( 3 ), wherein said crystalline polyethylene-based resin ( 2 ) and said block copolymer ( 3 ) constitute a three-dimensional network structure in a matrix formed by said ethylene•α-olefin-based copolymer ( 1 ); 
 (i) an organic blowing agent-containing resin in which an organic blowing agent ( 4   a ) is kneaded in an olefin resin ( 6 ) and an inorganic blowing agent-containing resin in which an inorganic blowing agent ( 4   b ) is kneaded in an olefin resin ( 6 ), or (ii) an organic/inorganic blowing agent-containing resin in which an organic blowing agent ( 4   a ) and an inorganic blowing agent ( 4   b ) are kneaded in an olefin resin ( 6 ); and    a nucleating agent-containing resin in which a nucleating agent ( 5 ) is kneaded in an olefin resin ( 6 );    wherein said thermoplastic elastomer has a melt flow rate of 5 g/10 min or more at a temperature of 230° C. and a load of 10 kg, and a melt tension of 3.0 gf or more at a temperature of 210° C. and a pulling rate of 2 m/min;    said block copolymer ( 3 ) is a block copolymer having a crystalline ethylene polymer block and a block having a higher compatibility to said ethylene•α-olefin-based copolymer ( 1 ) than to said crystalline polyethylene-based resin ( 2 ); and    characterized by said thermoplastic elastomer composition for core-back system foam injection molding is injected into a cavity space of a metal mold and is foamed by opening the metal mold thereby expanding said cavity space to form an injection foaming product having a skin layer and a foamed layer.    
     
     
         16 . The thermoplastic elastomer composition for core-back system foam injection molding according to  claim 15 , wherein said nucleating agent ( 5 ) is an inorganic compound powder of a particle diameter of 2 to 50 μm, said organic blowing agent ( 4   a ) is at least one selected from the group consisting of an azo-based blowing agent, a nitroso-based blowing agent, a sulfonyl hydrazide-based blowing agent, a triazine-based blowing agent and a tetrazole-based blowing agent, said inorganic blowing agent ( 4   b ) is at least one selected from the group consisting of sodium hydrogencarbonate, ammonium hydrogencarbonate, ammonium chloride and ammonium carbonate, and said composition further comprises at least a weakly acidic compound selected from the group consisting of oxalic acid, malonic acid, citric acid, lactic acid, boric acid, monosodium citrate and acidic potassium tartrate.  
     
     
         17 . A foam injection molding method characterized by comprising injecting a thermoplastic elastomer composition for core-back system foam injection molding according to  claim 1  into a cavity space in a metal mold, thereafter opening said metal mold at a mold opening rate of 0.05 to 0.4 mm/sec thereby expanding said cavity space to foam said thermoplastic elastomer composition and forming an injection foaming product having a skin layer and a foamed layer.  
     
     
         18 . The foam injection molding method according to  claim 17 , wherein a metal mold retraction delay time is 0 to 5 seconds after the completion of filling.  
     
     
         19 . The foam injection molding method according to  claim 17 , wherein said mold opening is executed in such a manner that a final thickness of said injection foaming product becomes 1.1 to 5.0 times of an initial thickness of the material filled in said cavity space in said metal mold.  
     
     
         20 . The foam injection molding method according to  claim 17 , wherein said injection foaming product is formed on a surface of a base body.  
     
     
         21 . A foam injection molding method characterized by comprising injecting a thermoplastic elastomer composition for core-back system foam injection molding according to  claim 3  into a cavity space in a metal mold, thereafter opening said metal mold at a mold opening rate of 0.05 to 0.4 mm/sec thereby expanding said cavity space to foam said thermoplastic elastomer composition and forming an injection foaming product having a skin layer and a foamed layer.  
     
     
         22 . A foam injection molding method characterized by comprising injecting a thermoplastic elastomer composition for core-back system foam injection molding according to  claim 5  into a cavity space in a metal mold, thereafter opening said metal mold at a mold opening rate of 0.05 to 0.4 mm/sec thereby expanding said cavity space to foam said thermoplastic elastomer composition and forming an injection foaming product having a skin layer and a foamed layer.  
     
     
         23 . A foam injection molding method characterized by comprising injecting a thermoplastic elastomer composition for core-back system foam injection molding according to  claim 7  into a cavity space in a metal mold, thereafter opening said metal mold at a mold opening rate of 0.05 to 0.4 mm/sec thereby expanding said cavity space to foam said thermoplastic elastomer composition and forming an injection foaming product having a skin layer and a foamed layer.  
     
     
         24 . A foam injection molding method characterized by comprising injecting a thermoplastic elastomer composition for core-back system foam injection molding according to  claim 9  into a cavity space in a metal mold, thereafter opening said metal mold at a mold opening rate of 0.05 to 0.4 mm/sec thereby expanding said cavity space to foam said thermoplastic elastomer composition and forming an injection foaming product having a skin layer and a foamed layer.  
     
     
         25 . A foam injection molding method characterized by comprising injecting a thermoplastic elastomer composition for core-back system foam injection molding according to  claim 11  into a cavity space in a metal mold, thereafter opening said metal mold at a mold opening rate of 0.05 to 0.4 mm/sec thereby expanding said cavity space to foam said thermoplastic elastomer composition and forming an injection foaming product having a skin layer and a foamed layer.  
     
     
         26 . A foam injection molding method characterized by comprising injecting a thermoplastic elastomer composition for core-back system foam injection molding according to  claim 13  into a cavity space in a metal mold, thereafter opening said metal mold at a mold opening rate of 0.05 to 0.4 mm/sec thereby expanding said cavity space to foam said thermoplastic elastomer composition and forming an injection foaming product having a skin layer and a foamed layer.  
     
     
         27 . A foam injection molding method characterized by comprising injecting a thermoplastic elastomer composition for core-back system foam injection molding according to  claim 15  into a cavity space in a metal mold, thereafter opening said metal mold at a mold opening rate of 0.05 to 0.4 mm/sec thereby expanding said cavity space to foam said thermoplastic elastomer composition and forming an injection foaming product having a skin layer and a foamed layer.