Extruded tubing and catheters having increased rotational stiffness

Claim 1

In the method of manufacturing tubing by extrusion of a plastic material through a tube extrusion die having an outer wall to define the extruded tube outer diameter and an inner wall to define the extruded tube inner diameter, the improvement comprising, in combination: extruding a tube of liquid crystal polymer plastic-containing material through said tube extrusion die with longitudinal stretching while rotating the outer and inner walls relative to each other whereby said tube of liquid crystal polymer plastic-containing material exhibits at least a degree of circumferential orientation, in which said liquid crystal polymer plastic-containing material comprises a blended mixture of from 1 to 40 weight percent of a liquid crystal polymer and 60 to 99 weight percent of a different, structural plastic matrix, said liquid crystal polymer defining a separate phase from said structural plastic matrix, said separate phase forming generally helically extending fibrils within said extruded tube, said fibrils being dispersed in said structural plastic, whereby an increased amount of rotational stiffness is provided to at least a section of said tubing, and further in which the relative rotation rate of said outer and inner wall is varied as said tube is extruded, whereby various sections of the extruded tubing exhibit helically extending fibrils of differing angles to the longitudinal axis of said extruded tubing, and the various sections of the extruded tubing exhibit differing, predetermined rotational stiffness.