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.

Description

[0001] This is a continuation of application Ser. No. 10 / 179,646 filed Jun. 24, 2002, now U.S. Pat. No. 6,787,095, which is a divisional of application Ser. No. 09 / 706,266, filed Nov. 30, 2000, now U.S. Pat. No. 6,465,067, which is a continuation of Ser. No. 09 / 657,494, filed Sep. 8, 2000, now abandoned, which is a division of Ser. No. 09 / 034,431, filed Mar. 4, 1998, now abandoned, all incorporated herein by reference.BACKGROUND OF THE INVENTION [0002] Devices having a balloon mounted at the distal end of a catheter are useful in a variety of medical procedures. A balloon reservoir may be used to deliver a biologically compatible fluid, such a radiologically opaque fluid for contrast x-rays, to a site within the body. Radial expansion of a balloon may be used to expand or inflate a stent positioned within the body. A balloon may also be used to widen a vessel into which the catheter is inserted by dilating the blocked vessel. For example, in the technique of balloon angioplasty, a c...

AI Technical Summary

Benefits of technology

The present invention is about a processing technique for making blow molded articles, such as medical balloons, from PBT polymers or copolymers. The technique involves a longitudinal necking step and a radial expansion step. The invention also includes the use of a small amount of boric acid in the polymer material to improve processability and strength of the resulting article. The invention is useful for making articles from PBT polymers and can be practiced together with the described processing technique.

Problems solved by technology

To date, however, no reference has actually reported the preparation of a PBT dilatation balloon, or even a PBT balloon layer.

The imaging balloons prepared according to this patent are not suitable for dilatation or for other high pressure applications.

However for articles which are prepared from an extruded parison by a blow molding process, use of PBT polymer material has proven to be extremely difficult or impossible.

This is because even very rapidly quenched extrusions are typically so high in crystallinity that the parison cannot be further processed in a practical manner.

Opacification of the parison, another effect of PBT's high crystallinity, may also have been perceived as a problem for quality control in a manufacturing process.

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