Process of producing a fibrillated semi-interpenetrating polymer network of polytetrafluoroethylene and silicone elastomer and shaped products thereof

• US 4,945,125 A
• Filed: 01/05/1987
• Issued: 07/31/1990
• Est. Priority Date: 01/05/1987
• Status: Expired due to Term

• Current Assignee: Donaldson Company Incorporated
• Original Assignee: Tetratec Corporation
• Inventors: Dillon, Joseph A., Dillon, Mark E.
• Primary Examiner(s): BRIGGS SR, WILBERT
• Application Number:
  US07/000,389
• Time in Patent Office: 1,303 Days
• Field of Search: 525/104, 264/127, 264/DIG. 47, 264/210.2, 264/211.24
• US Class Current: 524/427
• CPC Class Codes: B29C 48/022 characterised by the choice of material
• CPC Class Codes: B29C 48/08 flexible, e.g. films
• CPC Class Codes: B29K 2027/18 PTFE, i.e. polytetrafluorethene , e.g. ePTFE, i.e. expanded polytetrafluorethene
• CPC Class Codes: C08F 230/08 containing silicon
• CPC Class Codes: C08F 259/08 on to polymers containing fluorine
• CPC Class Codes: C08G 77/12 containing silicon bound to hydrogen C08G77/045 takes precedence
• CPC Class Codes: C08G 77/20 containing silicon bound to unsaturated aliphatic groups C08G77/045 takes precedence
• CPC Class Codes: C08J 2427/00 Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers
• CPC Class Codes: C08J 2483/00 Characterised by the use of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon with or without sulfur, nitrogen, oxygen, or carbon only; Derivatives of such polymers
• CPC Class Codes: C08K 5/01 Hydrocarbons C08K5/0091 takes precedence
• 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 83/04 Polysiloxanes
• CPC Class Codes: Y10S 264/47 Processes of splitting film, webs or sheets

Abstract

A process for producing a semi-interpenetrating polymer network of polytetrafluoroethylene and silicone elastomers is described which comprises the steps of (1) intimately blending a mixture of a major amount of unsintered and unfibrillated particulate polytetrafluoroethylene dispersion resin and minor amounts of (A) a hydrocarbon liquid and (B) an addition curable silicone composition consisting essentially of a polydiorganosiloxane having alkenyl unsaturation, an organohydrogenpoly-siloxane crosslinking agent, a catalyst for promoting crosslinking of said polysiloxane, and an inhibitor for the catalytic reaction; (2) forming said blend into an extrudable shape; (3) biaxially extruding said blend through a die into a shaped extrudate product having a randomly fibrillated structure; (4) evaporating said hydrocarbon liquid, and activating said catalyst so as to generate a cured silicone elastomer and polytetrafluoroethylene semi-interpenetrating polymer network comprising said fibrillated extrudate structure. Products produced by this process have improved physical properties as compared to extruded fibrillated polytetrafluoroethylene dispersion resin alone.

Claims

1. A process for producing a semi-interpenetrating polymer network of polytetrafluoroethylene and silicone elastomers which comprises the steps of (1) intimately blending a mixture of a major amount of unsintered and unfibrillated particulate polytetrafluoroethylene dispersion resin and minor amounts of (A) a hydrocarbon liquid and (B) an addition curable silicone composition consisting essentially of a polydiorganosiloxane having alkenyl unsaturation, an organohydrogenpolysiloxane crosslinking agent, a catalyst for promoting crosslinking of said polysiloxane, and an inhibitor for the catalytic reaction;

(2) forming said blend into an extrudable shape;

(3) biaxially extruding said blend through a die into a shaped extrudate product having a randomly fibrillated structure;

(4) evaporating said hydrocarbon liquid, and activating said catalyst so as to generate a cured silicone elastomer and polytetrafluoroethylene semi-interpenetrating polymer network comprising said fibrillated extrudate structure.

2. The process of claim 1 further characterized by calendering the shaped extrudate product to a uniform thickness.

3. The process of claim 1 wherein the amount of addition curable silicone composition constitutes at least two percent by weight of the mixture of polytetrafluoroethylene, hydrocarbon liquid and addition curable silicone composition.

4. The process of claim 1, wherein the mixture of step (1) includes additionally a minor amount of calcium carbonate.

5. The product of the process of claim 1.