Process for producing a high strength porous polytetrafluoroethylene product having a coarse microstructure
First Claim
1. A process for producing a porous material of polytetrafluoroethylene polymer, which material is characterized by relatively large nodes interconnected by realtively long fibrils and having relatively high matrix tensile strength, the material having been produced from paste-extruded unsintered polytetrafluoroethylene extrudate, the process comprising the steps:
- (a) providing an unsintered dry extrudate;
(b) increasing the density of the dry extrudate to greater than about 1.80 gm/cc at a temperature below the crystalline melt temperature of PTFE; and
(c) stretching said densified dry extrudate at an elevated temperature less than the crystalline melt temperature.
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Accused Products
Abstract
Porous polytetrafluoroethylene materials having high strength and coarse microstructure are produced by densifying the materials after removal of lubricant and then stretching. The term, "coarse," is used to indicate that the nodes are larger, the fibrils are longer, and the effective pore size is larger than conventional materials of the same matrix tensile strength. Densification can be achieved through the use of such devices as a densification die, a calender machine, or a press. This invention can be used to produce all kinds of shaped articles.
341 Citations
18 Claims
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1. A process for producing a porous material of polytetrafluoroethylene polymer, which material is characterized by relatively large nodes interconnected by realtively long fibrils and having relatively high matrix tensile strength, the material having been produced from paste-extruded unsintered polytetrafluoroethylene extrudate, the process comprising the steps:
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(a) providing an unsintered dry extrudate; (b) increasing the density of the dry extrudate to greater than about 1.80 gm/cc at a temperature below the crystalline melt temperature of PTFE; and (c) stretching said densified dry extrudate at an elevated temperature less than the crystalline melt temperature. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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Specification