Composition and process for manufacturing PBT catheter balloons

Abstract

A processing technique and a composition which allow compositions of PBT polymers or copolymers to be formed into blow molded articles, especially medical balloons such as dilatation or stent placement balloons, from extruded tubular parisons. The process includes a longitudinal stretch step run at a temperature below the Tg of the polymeric material and a radial expansion step run at a temperature above the Tg of the polymeric material. During the longitudinal stretch step, the tubing is subjected to high internal pressure. In the composition a small amount of boric acid is added to the polybutylene terephthalate in a melt blend to give a formulation which has reduced crystallinity after extrusion and which can more readily fashioned into high strength blow molded articles than PBT by itself. Articles, which may be formed using the invention include medical device balloon articles in which the polymer consists essentially of PBT optionally blended with boric acid.

1 . A composition prepared by melt mixing a high butylene terephthalate content polymer material with 0.01-5.0% by weight of said composition of boric acid.  
     
     
         2 . A composition as in  claim 1  wherein the polymer material is a member selected from the group consisting of 
 a) poly(butylene terephthalate) homopolymer,    b) random polyester copolymers having above 80% butylene terephthalate repeat units,    c) block copolymers comprising about 60% or more by weight of poly(butylene terephthalate),    d) mixtures of at least two of a), b) and/or c); and    e) mixtures of one or more of a), b) and/or c) with no more than 10% by weight of another polymer.    
     
     
         3 . A composition as in  claim 1  wherein the polybutylene terephthalate content is sufficient to cause opacification of extruded material in the absence of said boric acid.  
     
     
         4 . A composition as in  claim 1  wherein said polymer material is poly(butylene terephthalate) homopolymer.  
     
     
         5 . A composition as in  claim 1  wherein said polymer material is poly(butylene terephthalate)-block-poly(tetramethylene oxide).  
     
     
         6 . A composition as in  claim 1  wherein the amount of boric acid is from about 0.05 to 0.5% by weight.  
     
     
         7 . A composition as in  claim 1  wherein the amount of boric acid is from about 0.1 to 0.3% by weight.