Elastomeric tube and method of making same

Abstract

In an elastomeric tube and a method for making such a tube, two medical-grade silicone rubber compositions are coaxially coextruded to form a tube. The compositions respectively differ in at least one physical property and respectively have similar curing conditions. The two compositions are blended at an interface formed between the two compositions during the coextruding, so that between 1-99% of the tube forms a blended gradient. The coextruded tube is then cured.

What is claimed is: 
     
         1 . An apparatus for making an elastomeric tube, comprising:
 an extruder that coaxially extrudes at least two medical-grade silicone rubber compositions, respectively differing in at least one physical property and respectively having similar curing conditions to form a coextruded tube;   a blender that simultaneously blends between 1% and 99% of the at least two compositions at an interface formed between the at least two compositions during coextrusion; and   a curing unit that cures the coextruded tube.   
     
     
         2 . The apparatus according to clam  1 , wherein the curing unit implements curing with platinum. 
     
     
         3 . The apparatus according to  claim 1 , wherein the curing unit implements curing with peroxide cross-linking. 
     
     
         4 . The apparatus according to  claim 1 , wherein the blender comprises a control unit that manipulates feed rates of the at least two compositions. 
     
     
         5 . The apparatus according to  claim 1 , wherein a first composition of the at least two compositions has at least one property selected from the group consisting of a tear strength in the range of 30-60 N/mm and a tensile strength of 8-15 MPa. 
     
     
         6 . The apparatus according to  claim 1 , wherein a second composition of the at least two compositions has at least one property selected from the group consisting of a tensile strength of at least 7 MPa and an abrasion resistance according to the Taber Abrasion test (ASTM D4060) of less than 500 mg at 3000 cycles with 1000-g load and H-18 (fine). 
     
     
         7 . The apparatus according to  claim 1 , wherein a graduated mixture of the at least two compositions at the interface has at least one property selected from the group consisting of a tear strength of at least 35 M/mm and a tensile strength of at least 8.5 MPa. 
     
     
         8 . The apparatus according to  claim 1 , wherein the coextruded tube is for a cardiac lead extending between a distal end and a proximal end. 
     
     
         9 . The apparatus according to  claim 1 , wherein the coextruded tube has an outer diameter in the range of 3-34 French. 
     
     
         10 . The apparatus according to  claim 1 , wherein the coextruded tube has an inner diameter in the range of 3-34 French.