Method of increasing the tensile strength of a dilatation balloon

Claim 1

A method of making a thin wall dilatation balloon (12) having a high percentage of the maximum tensile strength of the balloon material, the method comprising the steps of heating a thin wall tubular parison (20) made of biaxially orientable polymer to a temperature no less than the orientation temperature of the polymer, axially drawing and circumferentially expanding the parison (20) while it is subjected to said temperature, said circumferential expansion being achieved by sealing one end of the parison (20) and injecting fluid (27) to expand the parison (20) characterised in that said fluid (27) being heated and in that the tubular parison (20) has a wall thickness of no greater than about 0.635mm (0.025 inches) and is heated to provide a temperature gradient across the sidewall of the parison (20) which gradient results in a decrease of the temperature of the wall from the inner to the outer surface of the parison (20), the parison (20) is axially drawn and circumferentially expanded while it is subjected to said temperature gradient, and the temperature gradient is selected to compensate for differing degrees of stretch across the sidewall whereby a thin wall dilatation balloon (12) is produced having a high average tensile strength and a substantially uniform and relatively high degree of orientation across its sidewall.

Claim 4

The method of any preceding claim characterised in that the temperature gradient is selected to produce a balloon (12) having a difference in orientation across the sidewall of less than 50%.

Claim 5

The method of any preceding claim characterised in that the parison (20) is axially drawn and circumferentially expanded to produce a balloon (12) having a wall thickness of no greater than about 0.1mm (4 mils).

Claim 6

The method of any preceding claim characterised in that the polymer is selected from the group consisting of polyester, polyurethane, nylon, polyester and/or polyether block copolymers, ionomer resins, and combinations thereof.

Claim 7

The method of any preceding claim characterised in that the polymer is semi crystalline.

Claim 10

The method of any preceding claim characterised in that the parison (20) is expanded at substantially different inner and outer diameter stretch ratios which differ by at least 25% whereby the resulting expanded article has a high percentage of the maximum tensile strength of the parison material.

Claim 11

The method of any preceding claim further characterised by the step of heat setting the drawn and circumferentially expanded parison (20) by elevating the temperature of the formed balloon (12) and maintaining the temperature for a period of time sufficient for heat setting the balloon (12) and ensuring the dimensional stability of the balloon (12).