Catheter balloon and method for forming same
A catheter balloon and method involves extruded tubing with multiple layers of different durometer values, selected such that the blow up ratio (BUR) at the balloon's inner surface is increased. In one method a two stage blow mold process uses a small radius initial stage where radial growth is limited, followed by a second stage to a final dimension. A single stage blow mold process is also disclosed where the materials and processing are selected to approach the elongation to failure limit of the material. The single stage approach is preferably followed by a modified post-expansion heat set treatment to promote greater axial strength, leading to a preferred failure mode in the axial rather than radial direction.
1. A balloon catheter, comprising:
a) an elongated catheter shaft having a proximal end and a distal end and an inflation lumen extending therein; and
b) a multilayer balloon on a distal section of the shaft having an interior in fluid communication with the inflation lumen, the multilayer balloon having a first layer of a first elastomeric polymeric material, and a second layer of a second elastomeric polymeric material having a lower maximum blow up ratio (BUR) than the first elastomeric polymeric material and being an outer layer relative to the first layer, the multilayer balloon being formed by blow-molding such that the multilayer balloon is blown, in at least a first stage, to a final working radial dimension, wherein an area draw-down ratio (ADDR) of 2.0 for the multilayer balloon is targeted.
2. The balloon catheter of claim 1 , wherein the multilayer balloon is blown in the first stage to a first radial dimension, and further wherein the multilayer balloon is blown in a subsequent stage to the final working radial dimension.
3. The balloon catheter of claim 1 , wherein second layer has a Shore durometer hardness greater than a Shore durometer hardness of the first layer.
4. The balloon catheter of claim 1 , wherein the first layer is bonded to the second layer with a tie layer.
5. The balloon catheter of claim 1 , wherein the balloon catheter is a stent delivery catheter, and further wherein an expandable stent is mounted on the multilayer balloon for delivery and deployment within a patient's body lumen.
6. The balloon catheter of claim 1 , wherein the multilayer balloon is blown in the first stage to the final working radial dimension and further wherein the multilayer balloon is heat set at a temperature above 100° C. after blow molding.
7. The balloon catheter of claim 6 , wherein the multilayer balloon is heat set for about 15 to about 60 minutes.
8. The balloon catheter of claim 6 , wherein the second layer has a Shore durometer hardness greater than a Shore durometer hardness of the first layer.
9. The balloon catheter of claim 6 , wherein the first layer is bonded to the second layer with a tie layer.
10. The balloon catheter of claim 6 , wherein the balloon catheter is a stent delivery catheter, and further wherein an expandable stent is mounted on the multilayer balloon for delivery and deployment within a patient's body lumen.
11. A method of making a balloon catheter, comprising:
a) providing an elongated shaft having a proximal end and a distal end and an inflation lumen extending therein;
b) providing a multilayer tube comprising a first layer of a first elastomeric polymeric material and a second layer of a second elastomeric polymeric material, the second elastomeric polymeric material having a lower maximum blow up ratio (BUR) than the first elastomeric polymeric material, and the multilayer tube having an inner diameter and an outer diameter, wherein the second layer is an outer layer relative to the first layer;
c) forming a multilayer balloon by blow-molding the multilayer tube such that the multilayer balloon is blown, in at least a first stage, to a final working radial dimension, and further wherein an area draw-down ratio (ADDR) of 2.0 for the multilayer balloon is targeted; and
d) securing the multilayer balloon on a distal section of the shaft with an interior of the multilayer balloon in fluid communication with the inflation lumen.
12. The method of claim 11 , wherein the second elastomeric polymeric material has a Shore durometer hardness greater than a Shore durometer hardness of the first elastomeric polymer material.
13. The method of claim 11 , wherein the multilayer tube is formed by coextrusion.
14. The method of claim 11 , further comprising heating the balloon to at least 100° C. for about fifteen to about sixty minutes after blow-molding.