Modified ethylene-vinyl alcohol copolymer, gas barrier resin, and molded article of the same

Abstract

Ethylene-vinyl alcohol copolymers have superior gas barrier properties, but are inferior in bending fatigue resistance. The present invention improves bending fatigue resistance without reducing the gas barrier property and heat resistance. An ethylene-vinyl alcohol copolymer having an ethylene content of 20 to 50 percent by mole is modified by incorporating 0.01 to 1% mol of a structural unit expressed by the following formula (3): wherein, n indicates an integer of 2 to 5, m indicates an integer of 10 to 20, and R 1 indicates a C 1 to C 20 aliphatic hydrocarbon group provided that R 1 may contain a mercapto group, thioester group, sulfenamide, vinyl group, methacryloxy group, or acryloxy group. The modified ethylene vinyl alcohol copolymer may be used as a gas barrier resin and this gas barrier resin may be shaped or laminated and used in various applications such as in pneumatic tires and hoses.

1 . A modified ethylene-vinyl alcohol copolymer comprising 20 to 50 percent by mole of a structural unit (1) expressed by the following formula (1):
   —CH 2 —CH 2 —  (1)   a structural unit (2) expressed by the following formula (2):   
     
       
         
         
             
             
         
       
       and 0.01 to 1 percent by mole of a structural unit (3) expressed by the following formula (3): 
     
     
       
         
         
             
             
         
       
       wherein n indicates an integer of 2 to 7, m indicates an integer of 10 to 20, and R 1  indicates a C 1  to C 20  aliphatic hydrocarbon group or aliphatic hydrocarbon group substituted with a mercapto group, thioester group, sulfonamide, vinyl group, methacryloxy group, or acryloxy group. 
     
   
   
       2 . A modified ethylene-vinyl alcohol copolymer as set forth in  claim 1 , wherein the modified ethylene-vinyl alcohol copolymer is prepared by melt blending an ethylene-vinyl alcohol copolymer with an alkyl polyether silane expressed by the following formula (4): 
     
       
         
         
             
             
         
       
       wherein R 2  is a methyl group or ethyl group, and R 1 , n, and m are the same as the above. 
     
   
   
       3 . A gas barrier resin comprising a modified ethylene-vinyl alcohol copolymer as set forth in  claim 1 . 
   
   
       4 . A gas barrier resin as set forth in  claim 3 , comprising 100 parts by weight of the modified ethylene-vinyl alcohol copolymer and 5 to 120 parts by weight of a soft resin modified by an acid anhydride. 
   
   
       5 . A molded article comprising a gas barrier resin as set forth in  claim 3 . 
   
   
       6 . A laminate comprising a layer of a gas barrier resin as set forth in  claim 3  and a layer of a resin and/or an elastomer other than the gas barrier resin. 
   
   
       7 . A laminate as set forth in  claim 6 , wherein the resin other than the gas barrier resin is at least one resin selected from the group consisting of a polyolefin, polyamide, polyester, polystyrene, polyurethane, poly(vinylidene chloride), poly(vinyl chloride), polyacrylonitrile, and polycarbonate. 
   
   
       8 . A laminate as set forth in  claim 6 , wherein the elastomer other than the gas barrier resin is selected from the group consisting of a diene-based elastomer, urethane-based elastomer, olefin-based elastomer, and styrene-based elastomer. 
   
   
       9 . A pneumatic tire comprising a gas barrier resin as set forth in  claim 3  as an air barrier layer. 
   
   
       10 . A hose comprising a gas barrier resin as set forth in  claim 3  as an air barrier layer. 
   
   
       11 . A pneumatic tire comprising a laminate as set forth in  claim 6  as an air barrier layer. 
   
   
       12 . A hose comprising a laminate as set forth in  claim 6  as an air barrier layer. 
   
   
       13 . A gas barrier resin comprising a modified ethylene-vinyl alcohol copolymer as set forth in  claim 2 . 
   
   
       14 . A molded article comprising a gas barrier resin as set forth in  claim 4 . 
   
   
       15 . A laminate comprising a layer of a gas barrier resin as set forth in  claim 4  and a layer of a resin and/or an elastomer other than the gas barrier resin. 
   
   
       16 . A laminate as set forth in  claim 15 , wherein the resin other than the gas barrier resin is at least one resin selected from the group consisting of a polyolefin, polyamide, polyester, polystyrene, polyurethane, poly(vinylidene chloride), poly(vinyl chloride), polyacrylonitrile, and polycarbonate. 
   
   
       17 . A laminate as set forth in  claim 16 , wherein the elastomer other than the gas barrier resin is selected from the group consisting of a diene-based elastomer, urethane-based elastomer, olefin-based elastomer, and styrene-based elastomer. 
   
   
       18 . A laminate as set forth in  claim 7 , wherein the elastomer other than the gas barrier resin is selected from the group consisting of a diene-based elastomer, urethane-based elastomer, olefin-based elastomer, and styrene-based elastomer. 
   
   
       19 . A gas barrier resin as set forth in  claim 13 , comprising 100 parts by weight of the modified ethylene-vinyl alcohol copolymer and 5 to 120 parts by weight of a soft resin modified by an acid anhydride. 
   
   
       20 . A pneumatic tire comprising a gas barrier resin as set forth in  claim 4  as an air barrier layer.