Adhesive composition, process for producing the same, molded objects, and process for producing heat-shrinkable tube

Abstract

An adhesive composition comprising 100 parts by weight of a fluorine-containing polymer and 2 to 30 parts by weight of an unsaturated compound containing at least one polar group selected from the group consisting of an epoxy group and a carboxyl group, wherein the fluorine-containing polymer has been graft-modified with the polar group-containing unsaturated compound by irradiation of ionizing radiation, a production process thereof, and formed products such as a heat-shrinkable tube equipped with a layer composed of the adhesive composition.

1 . An adhesive composition comprising 100 parts by weight of a fluorine-containing polymer and 2 to 30 parts by weight of an unsaturated compound containing at least one polar group selected from the group consisting of an epoxy group and a carboxyl group, wherein the fluorine-containing polymer has been graft-modified with the polar group-containing unsaturated compound by irradiation of ionizing radiation.  
     
     
         2 . The adhesive composition according to  claim 1 , which further comprises an antioxidant in a proportion of 0.1 to 5 parts by weight per 100 parts by weight of the fluorine-containing polymer.  
     
     
         3 . The adhesive composition according to  claim 1 , wherein the fluorine-containing polymer is at least one polymer selected from the group consisting of a fluororesin and a fluororubber.  
     
     
         4 . The adhesive composition according to  claim 3 , wherein the fluororesin is a fluororesin having a melting point not lower than 80° C., but lower than 140° C., and the fluororubber is a fluororubber having a Mooney viscosity (ML 1+10 , 121° C.) of 5 to 70.  
     
     
         5 . The adhesive composition according to  claim 3 , wherein the fluororesin is at least one fluororesin selected from the group consisting of polyvinylidene fluoride (PVdF), binary copolymers (VdF-TFE copolymers) of vinylidene fluoride (VdF) and tetrafluoroethylene (TFE), binary copolymers (VdF-HFP copolymers) of vinylidene fluoride (VdF) and hexafluoropropylene (HFP), ternary copolymers (VdF-TFE-HFP terpolymers) of vinylidene fluoride (VdF), tetrafluoroethylene (TFE) and hexafluoropropylene (HFP), copolymers (ETFEs) of ethylene and tetrafluoroethylene (TFE), copolymers (ECTFEs) of ethylene and chlorotrifluoroethylene (CTFE), copolymers (FEPs) of tetrafluoroethylene (TFE) and hexafluoropropylene (HFP), and copolymers (PFAs) of tetrafluoroethylene (TFE) and a perfluoroalkyl vinyl ether.  
     
     
         6 . The adhesive composition according to  claim 3 , wherein the fluororubber is at least one fluororubber selected from the group consisting of copolymer rubber (VdF-HFP fluororubber) of vinylidene fluoride (VdF) and hexafluoropropylene (HFP), terpolymer rubber (VdF-HFP-TFE fluororubber) of vinylidene fluoride (VdF), hexafluoropropylene (HFP) and tetrafluoroethylene (TFE), copolymer rubber (VdF-PFP fluororubber) of vinylidene fluoride (VdF) and pentafluoropropylene (PFP), terpolymer rubber (VdF-PFP-TFE fluororubber) of vinylidene fluoride (VdF), pentafluoropropylene (PFP) and tetrafluoroethylene (TFE), terpolymer rubber (VdF-PFMVE-TFE fluororubber) of vinylidene fluoride (VdF), perfluoromethyl vinyl ether (PFMVE) and tetrafluoroethylene (TFE), copolymer rubber (VdF-CTFE fluororubber) of vinylidene fluoride (VdF) and chlorotrifluoroethylene (CTFE), copolymer rubber (TFE-P fluororubber) of tetrafluoroethylene (TFE) and propylene (P), and thermoplastic fluororubber.  
     
     
         7 . The adhesive composition according to  claim 1 , wherein the epoxy group-containing unsaturated compound is a compound having at least one epoxy group and a polymerizable carbon-carbon unsaturated bond in a chemical structure thereof.  
     
     
         8 . The adhesive composition according to  claim 7 , wherein the epoxy group-containing unsaturated compound is at least one compound selected from the group consisting of glycidyl esters of unsaturated carboxylic acids, allylglycidyl isocyanates, monoglycidyl or polyglycidyl esters of unsaturated polycarboxylic acids, and allyl glycidyl ethers.  
     
     
         9 . The adhesive composition according to  claim 8 , wherein the glycidyl ester of the unsaturated carboxylic acid is glycidyl methacrylate, and the allylglycidyl isocyanate is diallylmonoglycidyl isocyanate.  
     
     
         10 . The adhesive composition according to  claim 1 , wherein the carboxyl group-containing unsaturated compound is a compound having at least one carboxyl group or acid anhydride group and a polymerizable carbon-carbon double bond in a chemical structure thereof.  
     
     
         11 . The adhesive composition according to  claim 10 , wherein the carboxyl group-containing unsaturated compound is at least one compound selected from the group consisting of unsaturated carboxylic acids, anhydrides of unsaturated dicarboxylic acids, and anhydrides of unsaturated carboxylic acids.  
     
     
         12 . The adhesive composition according to  claim 11 , wherein the acid anhydride of the unsaturated dicarboxylic acid is maleic anhydride.  
     
     
         13 . The adhesive composition according to  claim 1 , wherein the fluorine-containing polymer has been graft-modified with the polar group-containing unsaturated compound by irradiation of ionizing radiation in the quantity of 20 to 700 kGy.  
     
     
         14 . The adhesive composition according to  claim 1 , which exhibits initial adhesion strength of at least 1.0 kg/cm to any of a stainless steel plate, a copper plate, an iron plate and an aluminum plate when a strip sample formed from the adhesive composition and having a thickness of 1 mm is laminated on a metal plate selected from the group consisting of the stainless steel plate, copper plate, iron plate and aluminum plate, and the laminated sample is then subjected to a T-shape peeling test at a rate of pulling of 50 mm/min.  
     
     
         15 . The adhesive composition according to  claim 1 , which exhibits initial adhesion strength of at least 1.0 kg/cm to any of a stainless steel plate, a copper plate, an iron plate and an aluminum plate when a strip sample formed from the adhesive composition and having a thickness of 1 mm is laminated on a metal plate selected from the group consisting of the stainless steel plate, copper plate, iron plate and aluminum plate, the laminated sample is then left to stand for 3,000 hours in a gear oven of 150° C. to accelerate its deterioration, and the sample is then subjected to a T-shape peeling test at a rate of pulling of 50 mm/min.  
     
     
         16 . A formed product on a desired position of which an adhesive layer composed of the adhesive composition according to any one of  claims 1  to  15  has been arranged.  
     
     
         17 . A multi-layer heat-shrinkable tube having a structure that an adhesive layer composed of the adhesive composition according to any one of  claims 1  to  15  has been arranged on an internal surface of a heat-shrinkable tube.  
     
     
         18 . A heat-shrinkable cap having a structure that an adhesive layer composed of the adhesive composition according to any one of  claims 1  to  4  has been arranged on an internal surface of a heat-shrinkable tube, and one opening end of the heat-shrinkable tube has been shrunk by heat shrinkage to seal the end with the molten adhesive composition.  
     
     
         19 . A process for producing an adhesive composition comprising a fluorine-containing polymer, which comprises the following steps i and ii: 
 (i) Step i of incorporating 2 to 30 parts by weight of an unsaturated compound containing at least one polar group selected from the group consisting of an epoxy group and a carboxyl group into 100 parts by weight of the fluorine-containing polymer to prepare a fluorine-containing polymer composition; and    (ii) Step ii of forming the composition into a desired shape as needed, and then irradiating the composition with ionizing radiation to graft-modify the fluorine-containing polymer with the polar group-containing unsaturated compound.    
     
     
         20 . A process for producing a multi-layer heat-shrinkable tube having an adhesive layer on an internal surface thereof, which comprises the following steps 1 to 4: 
 (1) Step 1 of co-extruding a radiation-crosslinking composition comprising a fluorine-containing polymer and a polyfunctional monomer and a fluorine-containing polymer composition comprising 100 parts by weight of a fluorine-containing polymer and 2 to 30 parts by weight of an unsaturated compound containing at least one polar group selected from the group consisting of an epoxy group and a carboxyl group to form a tube-like formed product of a 2-layer structure having an outer layer composed of the radiation-crosslinking composition and an inner layer composed of the fluorine-containing polymer composition;    (2) Step 2 of irradiating the tube-like formed product with ionizing radiation to crosslink the radiation-crosslinking composition of the outer layer and graft-modify the fluorine-containing polymer composition of the inner layer;    (3) Step 3 of expanding the tube-like formed product in a radial direction thereof under heating; and    (4) Step 4 of cooling the tube-like formed product to fix the form expanded in the radial direction.