Microfiber-reinforced porous polymer film and a method for manufacturing the same and composites made thereof

• US 5,545,475 A
• Filed: 07/05/1995
• Issued: 08/13/1996
• Est. Priority Date: 09/20/1994
• Status: Expired due to Term

• Current Assignee: W. L. Gore & Associates (W.L. Gore & Associates)
• Original Assignee: W. L. Gore & Associates (W.L. Gore & Associates)
• Inventors: Korleski, Joseph E.
• Primary Examiner(s): Ryan, Patrick
• Assistant Examiner(s): WEISBERGER, RICHARD C
• Application Number:
  US08/498,488
• Time in Patent Office: 405 Days
• Field of Search: 525/151, 525/153, 525/165, 428/306.6, 428/308.4, 428/311.1, 428/314.4, 428/317.9, 428/320.2
• US Class Current: 428/306.6
• CPC Class Codes: C08J 2327/18 Homopolymers or copolymers of tetrafluoroethylene
• CPC Class Codes: C08J 2467/00 Characterised by the use of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Derivatives of such polymers
• CPC Class Codes: C08J 5/18 Manufacture of films or sheets
• CPC Class Codes: C08J 9/42 with macromolecular compounds
• CPC Class Codes: C08L 2666/04 Macromolecular compounds according to groups C08L7/00 - C08L49/00, or C08L55/00 - C08L57/00; Derivatives thereof
• CPC Class Codes: C08L 2666/14 Macromolecular compounds according to C08L59/00 - C08L87/00; Derivatives thereof
• CPC Class Codes: C08L 27/18 Homopolymers or copolymers or tetrafluoroethene
• CPC Class Codes: C08L 67/00 Compositions of polyesters obtained by reactions forming a carboxylic ester link in the main chain of polyester-amides C08L77/12; of polyester-imides C08L79/08; Compositions of derivatives of such polymers
• CPC Class Codes: C08L 67/04 Polyesters derived from hydroxycarboxylic acids, e.g. lactones C08L67/06 takes precedence
• CPC Class Codes: H05K 1/0353 consisting of two or more materials, e.g. two or more polymers, polymer + filler, + reinforcement
• CPC Class Codes: Y10T 428/249955 Void-containing component partially impregnated with adjacent component
• CPC Class Codes: Y10T 428/249958 Void-containing component is synthetic resin or natural rubbers
• CPC Class Codes: Y10T 428/249962 Void-containing component has a continuous matrix of fibers only [e.g., porous paper, etc.]
• CPC Class Codes: Y10T 428/249976 Voids specified as closed
• CPC Class Codes: Y10T 428/249986 Void-containing component contains also a solid fiber or solid particle
• CPC Class Codes: Y10T 428/249994 Composite having a component wherein a constituent is liquid or is contained within preformed walls [e.g., impregnant-filled, previously void containing component, etc.]

Abstract

A porous composite sheet is prepared from a mixture of polytetrafluoroethylene particulates and liquid crystal polymer particulates. The liquid crystal polymer in the porous composite sheet can be in the form of particulates contained within a polytetrafluoroethylene microstructure, or formed into a network of liquid crystal polymer fibers contained within and attached to the polytetrafluoroethylene microstructure. The porous composite sheet can be used as a self-reinforced porous sheet, for example, as a filter media. The pores of the composite sheet can be at least partially filled with polymeric resins and the composite sheet laminated to form useful electronic assemblies such as printed circuit boards and the like.

Claims

1. A porous composite sheet comprising:

(a) polytetrafluoroethylene; and

(b) liquid crystal polymer;

said sheet formed from a mixture of polytetrafluoroethylene particulate and liquid crystal polymer particulate;

said sheet having a concentration of liquid crystal polymer in the range 2 to 85 volume percent.

2. The porous composite sheet of claim 1 wherein the liquid crystal polymer is a thermotropic nematic liquid crystal polymer.

3. The porous composite sheet of claim 2, wherein the liquid crystal polymer is contained within a porous microstructure of polytetrafluoroethylene;

said liquid crystal polymer being in particulate form.

4. The porous composite sheet of claim 3, wherein the polytetrafluoroethylene is expanded polytetrafluoroethylene having a microstructure of nodes interconnected by fibrils.

5. The porous composite sheet of claim 4, wherein the liquid crystal polymer forms a microstructure of liquid crystal polymer fibers attached to and disposed within the microstructure of nodes interconnected by fibrils of the polytetrafluoroethylene.

6. The porous composite sheet of claim 1 further comprising a polymeric adhesive resin, wherein at least a portion of the void volume of the porous sheet is replaced with said polymeric adhesive resin.

7. The porous composite sheet of claim 2 further comprising a polymeric adhesive resin, wherein at least a portion of the void volume of the porous sheet is replaced with said polymeric adhesive resin.

8. The porous composite sheet of claim 3 further comprising a polymeric adhesive resin, wherein at least a portion of the void volume of the porous sheet is replaced with said polymeric adhesive resin.

9. The porous composite sheet of claim 4 further comprising a polymeric adhesive resin, wherein at least a portion of the void volume of the porous sheet is replaced with said polymeric adhesive resin.

10. The porous composite sheet of claim 5 further comprising a polymeric adhesive resin, wherein at least a portion of the void volume of the porous sheet is replaced with said polymeric adhesive resin.