Distensible dilatation balloon with elastic stress response and manufacture thereof

Abstract

Balloons and balloon catheters with a superior overall combination of distensibility, elastic stress response and strength. The improved properties of the balloons result from the method or process used to form the balloons, as well as the polymeric materials used in said balloon forming process. Additionally, the enhanced combination of properties of the balloons will not be adversely affected by the novel sterilization process contemplated by this invention.

1 . A balloon characterized by an improved overall combination of distensibility, elastic stress response and wall tensile strength made by the process comprising: 
 a. providing a parison of a block copolymer having regions of inter-molecular chain interaction separated by regions in which those individual portions of the polymer chains have the ability to uncoil, said parison having a predetermined original outer diameter, a predetermined wall thickness and a predetermined length;    b. subjecting said parison to at least one axial stretch step and at least one radial expansion step at temperature T 1  which is below the melting temperature of said block copolymer to increase the diameter and length of said parison to at least 3 times the original diameter and 2 times the original length and to decrease the original wall thickness to at least 20% of the original wall thickness to form an expanded parison; and    c. heating said expanded parison to a temperature of T 2  which is above T 1  but below the melting temperature of said block copolymer.    
     
     
         2 . The balloon according to  claim 1  wherein said radial expansion step is conducted while said parison is simultaneously subjected to said axial stretch step.  
     
     
         3 . The balloon according to  claim 1  wherein said axial stretch and radial expansion steps are conducted at temperature T 1  which is greater than the glass transition temperature of said block copolymer.  
     
     
         4 . A balloon according to  claim 1  wherein said block copolymer is selected from the group consisting of polyester block copolymers, polyamide block copolymers, polyurethane block copolymers, a mixture of nylon and polyamide block copolymers and a mixture of polyethylene terephthalate and polyester block copolymers.  
     
     
         5 . A balloon according to  claim 1  wherein said balloon has a distensibility of about 5 to about 20%, an elastic stress response not greater than about 5.00, and a wall tensile strength greater than about 14,000 psi.  
     
     
         6 . A balloon according to  claim 1  wherein said balloon has a distensibility of about 6 to about 17%, an elastic stress response of about 0.75 to about 4.00 and a wall tensile strength of about 16,000 to about 30,000 psi.  
     
     
         7 . A balloon according to  claim 1  wherein said block copolymer is a polyurethane having a Shore Hardness of about 74 D, a specific gravity of about 1.21, a tensile modulus of about 165,000 psi, a flexual modulus of about 190,000 psi, an ultimate tensile strength of about 6,980 psi and an ultimate elongation of about 250%.  
     
     
         8 . A balloon according to  claim 6  wherein T 1  is about 90-100° C. and T 2  is about 110-120° C.  
     
     
         9 . A process of forming a balloon characterized by an improved overall combination of distensibility, elastic stress response and wall tensile strength comprising: 
 a. providing a parison of a block copolymer having regions of inter-molecular chain interaction separated by regions in which those individual polymer portion of chains have the ability to uncoil, said parison having a predetermined original outer diameter, a predetermined wall thickness and a predetermined length;    b. subjecting said parison to at least one axial stretch step and at least one radial expansion step at temperature T 1  which is below the melting temperature of said block copolymer to increase the diameter and length of said parison to at least 3 times the original diameter and 2 times the original length and to decrease the original wall thickness to at least 20% of the original wall thickness to form an expanded parison; and    c. heating said expanded parison to a temperature of T 2  which is above T 1  but below the melting temperature of said block copolymer.    
     
     
         10 . The process according to  claim 9  wherein said radial expansion step is conducted while said parison is simultaneously subjected to said axial stretch step.  
     
     
         11 . The process according to  claim 9  wherein said axial stretch and radial expansion steps are conducted at temperature T 1  which is greater than the glass transition temperature of said block copolymer.  
     
     
         12 . A process according to  claim 9  wherein said block copolymer is selected from the group consisting of polyester block copolymers, polyamide block copolymers, polyurethane block copolymers, a mixture of nylon and polyamide block copolymers and a mixture of polyethylene terephthalate and polyester block copolymers.  
     
     
         13 . A process according to  claim 9  wherein said balloon formed has a distensibility of about 5 to about 20%, an elastic stress response of not greater than about 5.00 and a wall tensile strength greater than about 14,000 psi.  
     
     
         14 . A process according to  claim 9  wherein the balloon formed has a distensibility of about 6 to about 17%, an elastic stress response of about 0.75 to about 4.00 and a wall tensile strength of about 16,000 to about 30,000 psi.  
     
     
         15 . A process according to  claim 9  wherein said block copolymer is a polyurethane having a Shore Hardness of about 74 D, a specific gravity of about 1.21, a tensile modulus of about 165,000 psi, a flexual modulus of about 190,000 psi, an ultimate tensile strength of about 6,980 psi and an ultimate elongation of about 250%.  
     
     
         16 . A balloon catheter comprising the balloon of  claim 1 .  
     
     
         17 . A process for sterilizing balloons and balloon catheters comprising: 
 a. subjecting said balloons and balloon catheters to a temperature of about to about 45° C. and a relative humidity of about 55% for about 15 hours;    b. treating said balloons and balloon catheters at a temperature of about 35 to about 45° C. and a relative humidity of about 55% with ethylene oxide for about 15 hours; and    c. discontinuing treatment with ethylene oxide and subjecting said balloons and balloon catheters to a temperature of about 35 to about 45° C. for about 22 hours.