Flexible resin boot and method for producing it

Abstract

Provided is a flexible resin boot of which the noise-preventing effect lasts long and which ensures improved sealability and durability. The boot is formed from a base resin of a thermoplastic elastomer resin, and has a large port and a small port that are connected with each other via a bellows therebetween. For this, mineral oil or vegetable oil is added to the thermoplastic elastomer resin. Preferably, the thermoplastic elastomer resin is a thermoplastic polyester elastomer, and the mineral oil is process oil having an aromatic content of at most 13%. The boot is used for covering the constant velocity joint in an automobile.

1 - 26 . (canceled)  
   
   
       27 . A product prepared by a method for producing a flexible resin boot having a large port and a small port that are connected with each other via a bellows therebetween, from a base resin material of a thermoplastic polyester elastomer, which comprises adding a liquid additive containing mineral oil or vegetable oil to hot pellets of a thermoplastic polyester elastomer and mixing and stirring them, thereafter further kneading the resulting mixture and extruding it through an extruder to prepare a molding material, and finally molding the molding material into the flexible resin boot.  
   
   
       28 . The product as claimed in  claim 27 , wherein a solid additive is added to and mixed with the mixture of the pellets and the liquid additive by stirring them, and the resulting mixture is then further kneaded and extruded to give the molding material.  
   
   
       29 . The product as claimed in  claim 27 , wherein the pellets and a solid additive are heated and then mixed by stirring them, and thereafter the liquid additive is added to and mixed with the resulting mixture by further stirring them.  
   
   
       30 . The product as claimed in  claim 27 , wherein the liquid additive is, after having been heated, added to and mixed with the pellets by stirring them.  
   
   
       31 . The product as claimed in  claim 27 , wherein the pellets, the liquid additive and a solid additive are all heated, and then mixed together by stirring them to prepare the mixture.  
   
   
       32 . The product as claimed in  claim 27 , wherein the heating temperature is not lower than 60° C.  
   
   
       33 . The product as claimed on  claim 27 , wherein the heating temperature falls between 70 and 100° C.  
   
   
       34 . The product as claimed in  claim 27 , wherein the liquid additive contains mineral oil, an aromatic content of said mineral oil being greater than 13%.  
   
   
       35 . The product as claimed in  claim 27 , wherein the thermoplastic elastomer resin comprises hard segments composed of an aromatic dicarboxylic acid and a low-molecular-weight glycol, and soft segments having a molecular weight of from 400 to 4000.  
   
   
       36 . The product as claimed in  claim 35 , wherein the aromatic dicarboxylic acid that forms the hard segments is at least one selected from terephthalic acid and naphthalenedicarboxylic acid, and the low-molecular-weight glycol is at least one selected from ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, and dimer glycols.  
   
   
       37 . The product as claimed in  claim 35 , wherein the aromatic dicarboxylic acid that forms the hard segments is terephthalic acid, and the low-molecular-weight glycol is 1,4-butanediol.  
   
   
       38 . The product as claimed in  claim 35 , wherein the soft segments are of polyoxytetramethylene glycol, polyoxypropylene glycol or aliphatic polyester-diols.  
   
   
       39 . The product as claimed in  claim 35 , wherein the soft segments are of polyoxytetramethylene glycol.  
   
   
       40 . The product as claimed in  claim 39 , wherein the polyoxytetramethylene glycol comonomer content of the thermoplastic polyester elastomer is from 35 to 55% by weight.  
   
   
       41 . The product as claimed in  claim 39 , wherein the polyoxytetramethylene glycol comonomer content of the thermoplastic polyester elastomer is from 40 to 50% by weight.  
   
   
       42 . The product as claimed in  claim 27 , wherein the aromatic content of said mineral oil is from 0 to 10%.  
   
   
       43 . The method as claimed in  claim 34 , wherein at most 5 parts by weight of the process oil is added to 100 parts by weight of the thermoplastic elastomer resin.  
   
   
       44 . The product as claimed in  claim 34 , wherein the process oil has a number-average molecular weight of from 200 to 2000.  
   
   
       45 . The product as claimed in  claim 34 , wherein the process oil has a weight-average molecular weight of from 100 to 2000.  
   
   
       46 . The product as claimed in  claim 34 , wherein the process oil has a Z-average molecular weight of from 200 to 3000.  
   
   
       47 . The product as claimed in  claim 34 , wherein the process oil has a kinematic viscosity of from 100 to 1000 m×n2/sec (25° C.) as determined by measurement with a B-type viscometer.  
   
   
       48 . The product as claimed in  claim 27 , wherein the liquid additive contains vegetable oil.  
   
   
       49 . The product as claimed in  claim 48 , wherein at most 5 parts by weight of the vegetable oil is added to 100 parts by weight of the thermoplastic elastomer resin.  
   
   
       50 . The product as claimed in  claim 34 , wherein a degree of swelling of the polyester elastomer in the mineral oil is at most 8% by volume.  
   
   
       51 . The product as claimed in  claim 34 , wherein a degree of swelling of the polyester elastomer in the mineral oil is at most 6% by weight.  
   
   
       52 . The product as claimed in  claim 34 , wherein a paraffin content of the mineral oil is from 60 to 78% and a naphthene content of the mineral oil is from 20 to 35%.