Method of forming dual porosity FTFE tubes by extrusion of concentric preforms

• US 5,453,235 A
• Filed: 01/29/1993
• Issued: 09/26/1995
• Est. Priority Date: 01/29/1993
• Status: Expired due to Term

• Current Assignee: Bard Peripheral Vascular Incorporated (Becton, Dickinson & Co)
• Original Assignee: IMPRA Incorporated (Becton, Dickinson & Co)
• Inventors: Kowligi, Rajagopal R., Calcote, Robert W., Wollner, Stacy
• Primary Examiner(s): Kuhns, Allan R.
• Application Number:
  US08/010,974
• Time in Patent Office: 970 Days
• Field of Search: 264/127, 264/288.8, 264/289.3, 264/41, 264/209.5
• US Class Current: 264/127
• CPC Class Codes: A61F 2/06 Blood vessels
• CPC Class Codes: A61L 27/16 obtained by reactions only involving carbon-to-carbon unsaturated bonds
• CPC Class Codes: A61L 27/56 Porous materials, e.g. foams or sponges
• CPC Class Codes: A61M 2025/0062 having features to improve the sliding of one part within another by using lubricants or surfaces with low friction coatings A61M2025/0046
• CPC Class Codes: A61M 25/0009 Making of catheters or other medical or surgical tubes
• CPC Class Codes: B29C 48/022 characterised by the choice of material
• CPC Class Codes: B29C 48/09 Articles with cross-sections having partially or fully enclosed cavities, e.g. pipes or channels
• CPC Class Codes: B29C 48/21 the layers being joined at their surfaces
• CPC Class Codes: B29C 48/335 Multiple annular extrusion nozzles in coaxial arrangement, e.g. for making multi-layered tubular articles
• CPC Class Codes: B29C 48/475 using pistons, accumulators or press rams
• CPC Class Codes: B29C 55/00 Shaping by stretching, e.g. drawing through a die; Apparatus therefor B29C61/08 takes precedence
• CPC Class Codes: B29C 55/30 Drawing through a die pultrusion B29C70/52
• CPC Class Codes: B29K 2027/18 PTFE, i.e. polytetrafluorethene , e.g. ePTFE, i.e. expanded polytetrafluorethene
• CPC Class Codes: B29L 2031/7534 Cardiovascular protheses
• CPC Class Codes: B29L 2031/7542 Catheters
• CPC Class Codes: C08L 27/18 Homopolymers or copolymers or tetrafluoroethene
• CPC Class Codes: Y10T 428/139 Open-ended, self-supporting conduit, cylinder, or tube-type article
• CPC Class Codes: Y10T 428/1393 Multilayer [continuous layer]
• CPC Class Codes: Y10T 428/249981 Plural void-containing components
• CPC Class Codes: Y10T 428/31544 Addition polymer is perhalogenated

Abstract

A dual porosity PTFE tube including an inner surface of expanded PTFE material having a first porosity and an outer surface of expanded PTFE material having a porosity different from that of the inner surface. The preferred method includes the step of forming inner and outer preformed tubular billets of PTFE resin particles mixed with a lubricant; the outer billet is adapted to closely fit around and concentric to the inner billet. Porosity of the inner and outer surfaces is varied by changing, in the respective billets, the lubrication level and/or the PTFE resin characteristic average particle size. The inner billet is placed inside the outer billet, and the two are extruded together, thereby melding the two billets. The extrudate is then longitudinally expanded and sintered. The inner surface of the resulting PTFE tube exhibits a different porosity than the outer surface of the tube; the porosities of the inner and outer surfaces are both within a range of about 0.10-200μ.

Claims

1. A method of producing a dual porosity PTFE tube, said method comprising the steps of:

a. preforming a first inner tubular billet of PTFE resin particles having an average particle size of less than or equal to 355μ and

a lubricant, the first tubular billet having a predetermined lube level in the range of 50 to 150 grams of lubricant to 500 grams PTFE resin;

b. preforming a second outer tubular billet of PTFE resin particles having an average particle size of greater than or equal to 450μ and

a lubricant, the second tubular billet having a lube level in the range of 50 to 150 grams of lubricant to 500 grams PTFE resin and different from the predetermined lube level in the first inner tubular billet;

c. concentrically joining the first inner and the second outer tubular billets thereby forming a tubular extrusion billet;

d. co-extruding the tubular extrusion billet into a composite tubular extrudate;

e. longitudinally expanding the extrudate, thereby providing a PTFE tube having an inner surface with a first porosity and an outer surface with a second porosity different from the first porosity; and

f. sintering the extrudate.

2. The method of claim 1, wherein the dual porosity graft produced thereby has an average inner surface internodal distance greater than 8μ

and average outer surface internodal distance greater than 55μ

.

3. The method of claim 2, wherein the dual porosity graft produced thereby has an average inner surface internodal distance in the range of 8 to 40μ

and an average outer surface internodal distance in the range of 55 to 150μ

.

4. The method of claim 1, wherein the dual porosity graft produced thereby has an average outer surface internodal distance greater than 8μ

and average inner surface internodal distance greater than 55μ

.

5. The method of claim 4, wherein the dual porosity graft produced thereby has an average inner surface internodal distance in the range of 8 to 40μ

and an average outer surface internodal distance in the range of 55 to 150μ

.