Method for hot crystallization of neck portion in preform of biaxial stretch blow molded bottle and jig for use in the method

Abstract

A method for thermally crystallizing a neck of a primary molded product for forming a bottle-shaped container made of polyethylene terephthalate as principal ingredient, said neck having a functional part and a neck ring at a lower end thereof, said functional part being formed with screw threads at an upper portion thereof and a bead ring below the screw threads, said method comprising: heating the neck, and then squeezing the bead ring heated to the heat-deformable temperature, from outside so as to form an outer diameter of the bead ring within a dimensional tolerance for deformation with regard to sealing effect. Preferably, the primary molded product includes at least one resin layer(s) made of polyethylene terephthalate as principal ingredient and at least one gas barrier material layer(s), and has a multilayer structure. Also, preferably, the bead ring is squeezed by 0.1 mm to 0.4 mm in terms of an outer diameter of the bead ring immediately after a completion of heating. Also, a jig for the above method is provided.

1 . A method for thermally crystallizing a neck of a primary molded product for forming a bottle-shaped container made of polyethylene terephthalate as principal ingredient, 
 said neck having a functional part and a neck ring at a lower end thereof,    said functional part being formed with screw threads at an upper portion thereof and a bead ring below the screw threads,    said method comprising:    heating the neck, and then    squeezing the bead ring heated to the heat-deformable temperature, from outside so as to form an outer diameter of the bead ring within a dimensional tolerance for deformation with regard to sealing effect.    
   
   
       2 . The method according to  claim 1 , wherein the primary molded product has a multilayer structure including at least one gas barrier material layers in a resin layer made of polyethylene terephthalate as principal ingredient.  
   
   
       3 . The method according to  claim 1 , wherein the bead ring is squeezed by 0.1 mm to 0.4 mm in terms of an outer diameter of the bead ring immediately after a completion of heating.  
   
   
       4 . The method according to  claim 1 , wherein the bead ring is started to be squeezed at 10 seconds to 40 seconds after a completion of heating.  
   
   
       5 . The method according to  claim 1 , wherein the bead ring is squeezed for 3-15 seconds.  
   
   
       6 . A jig to be used for a thermal crystallization method of a neck of a primary molded product for forming a bottle-shaped container made of polyethylene terephthalate, said neck being formed with screw threads at an upper portion thereof, a bead ring below the screw threads, and a neck ring at a lower end thereof, wherein 
 said jig comprises a cylinder, and a piston rod in the cylinder,    said cylinder has a reduced diameter section and a tapered section outwardly expanded at a lower end thereof,    said reduced diameter section has a diameter smaller by 0.1 mm to 0.4 mm than an outer diameter of the bead ring having a thermally deformable temperature immediately after heating, and    said piston rod abuts an upper end of the neck, to prevent the neck from being pulled up.    
   
   
       7 . The jig according to  claim 6 , wherein said primary molded product has a multilayer structure including a gas barrier material layer in a resin layer made of polyethylene terephthalate as principal ingredient.  
   
   
       8 . The method according to  claim 2 , wherein the bead ring is squeezed by 0.1 mm to 0.4 mm in terms of an outer diameter of the bead ring immediately after a completion of heating.  
   
   
       9 . The method according to  claim 2 , wherein the bead ring is started to be squeezed at 10 seconds to 40 seconds after a completion of heating.  
   
   
       10 . The method according to  claim 3 , wherein the bead ring is started to be squeezed at 10 seconds to 40 seconds after a completion of heating.  
   
   
       11 . The method according to  claim 2 , wherein the bead ring is squeezed for 3-15 seconds.  
   
   
       12 . The method according to  claim 3 , wherein the bead ring is squeezed for 3-15 seconds.  
   
   
       13 . The method according to  claim 4 , wherein the bead ring is squeezed for 3-15 seconds.