COMPOSITIONS FOR COMPOUNDING, EXTRUSION AND MELT PROCESSING OF FOAMABLE AND CELLULAR FLUOROPOLYMERS

Abstract

The present invention relates generally to the use of talc as a chemical foaming agent in perfluoropolymers to form foamable and foamed compositions. For example, in one aspect, a foamable composition is disclosed, which comprises (i) one or more base perfluoropolymers comprising at least 50 percent by weight of the composition, and (ii) talc blended with the one or more base perfluoropolymers, where the talc comprises 3 percent to about 15 percent by weight of the composition. Each of the perfluoropolymers is selected from the group consisting of tetrafluoroethylene/perfluoromethylvinyl ether copolymer (MFA), hexafluoropropylene/tetrafluoroethylene copolymer (FEP) and perfluoroalkoxy (PFA) and any blend thereof, where hydrogen-containing fluoropolymers are absent from the composition. The one or more base perfluoropolymers are melt-processable at one or more elevated processing temperatures of at least about 600 F. at which the talc functions as a chemical foaming agent for extrusion or mold processing of the composition into a foamed article having uniform cell structures.

Claims

1-20. (canceled)

21. A method for manufacturing a foamed article comprising: heating a composition comprising a melt-processable perfluoropolymer and talc to a processing temperature of at least 600 F. at which said talc functions as a chemical foaming agent, thereby causing the foaming of said composition at a foaming rate in a range from 20% to 50% so as to form a foamed article; wherein said melt-processable perfluoroploymer is selected from the group consisting of tetrafluoroethylene/perfluoromethylvinyl ether copolymer (MFA), hexafluoropropylene/tetrafluoroethylene copolymer (FEP), perfluoroalkoxy (PFA) and any blend thereof, and wherein said talc is the only foaming agent in said composition and wherein said foaming is achieved without gas injection.

22. The method of claim 21, wherein said processing temperature is in a range of about 600 F. to about 660 F.

23. The method of claim 21, wherein said processing temperature is in a range of about 630 F. to about 660 F.

24. The method of claim 21, wherein said processing temperature is in a range of about 640 F. to about 660 F.

25. The method of claim 21, wherein said talc comprises recycled talc.

26. The method of claim 21, wherein said perfluoropolymer comprises recycled perfluoropolymer.

27. The method of claim 21, wherein said foamed article comprises any of a separator, wire insulation or cable jacketing.

28. The method of claim 21, further comprising extruding said foaming composition to form said foamed article.

29. The method of claim 21, further comprising mold processing said foaming composition to form said foamed article.

30. The method of claim 21, wherein said perfluoropolymer comprises at least 50 percent by weight of the composition.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0303] FIG. 1 is a schematic which are representative of processes used to produce the disclosed compositions.

DETAILED DESCRIPTIONS OF DRAWING

[0304] The following description will further help to explain the inventive features of the system, method and compositions of the present disclosure.

[0305] There are four distinct compositions that are created by the system and are noted as a first composition [100], a second composition [200], a third composition [300] and a fourth composition [400]. The first composition comprises a blend of selected perfluoropolymer [110], magnesium carbonate (MgCO.sub.3) [120], calcium carbonate (CaCO.sub.3) [130], and AClyn wax [140] as a powder blend mixed homogeneously. The second composition [200] is a blowing or foaming agent comprised of the first composition [100] and a selected perfluoropolymer [110] that is melted by heat, blended, extruded and pelletized by a specially flighted extruder [250] wherein the extruder is specifically designed to minimize heat transfer such that foaming or nucleation is not prematurely initiated and such that the composition may be melted, blended, extruded and pelletized without premature foaming of the composition. The third composition [300] which is a nucleating agent is comprised of a selected perfluoropolymer [110] and talc [310] (magnesium silicate hydroxide or other talc derivative) (Mg.sub.3Si.sub.4O.sub.10(OH).sub.2) which is blended, melted by heat extruded and pelletized in a specially flighted extruder [350]. The fourth composition [400] is comprised of the second composition [200] and the third composition [300] which are tumble blended for use in a profile extruder [450].

[0306] The first composition [100] comprises a selected perfluoropolymer [110] that may be MFA, FEP, or PFA, as a selected, uniform, pure perfluoropolymer [110] or as a mixture of one or more different perfluoropolymers [110] at or about 94.8 percent by weight. The perfluoropolymer [110], magnesium carbonate [120] at or about 3.79 percent, calcium carbonate [130] at or about 0.94 percent and AClyn wax [140] at or about 0.47 percent are mixed into a homogeneous powder in a Henschel blender.

[0307] The second composition [200] is comprised of the first composition [100] and a selected perfluoropolymer [110]. The ratio of perfluoropolymer [110] to first composition [100] is at or about 80 percent to at or about 20 percent by weight. The perfluoropolymer [110] may be MFA, FEP, or PFA, as a selected, uniform, pure perfluoropolymer [110] or as a mixture of one or more different perfluoropolymers [110]. The perfluoropolymer [110] may be substituted with fluoropolymer [115]. The first composition [100] and selected perfluoropolymer [110] are then placed in a extruder that minimizes mechanical shear and increased heating thereby mitigating premature foaming [250] during the process of melting blending, extruding and pelletizing.

[0308] The third composition [300] is comprised of magnesium silicate hydroxide, commonly known as talc [310] and perfluoropolymer [110]. The ratio of talc [310] is at or about 15 percent with the perfluoropolymer [110] at or about 85 percent by weight, however the talc [310] may range in concentration from 0.2 to 20 percent. The perfluoropolymer [110] component of the third composition [300] may be MFA, FEP, or PFA, as a selected, uniform, pure perfluoropolymer [110] or as a mixture of one or more different perfluoropolymers [110] or 100 percent recycled and/or blended with non-recycled perfluoropolymers [110] in any ratio from 1 to 99 percent. The third composition [300] is then placed in an extruder specifically designed to minimize heat transfer such that foaming or nucleation is not prematurely initiated [350] and such that the composition may be melted, blended, extruded and pelletized. Additionally, an organic or inorganic salt [320] may be added to the third composition [300].

[0309] The fourth composition [400] is comprised of the second composition [200] and third composition [300]. In pellet form, it is tumble blended at a ratio of 30 percent of the second composition [200] and 70 percent of the third composition [300]. It is also possible to form chemically foamed or gas injected foamed components [600] using 100 percent of the third composition [300] only. An additional blend of the fourth composition [400] includes approximately a 35 percent second composition [200], a 30 percent third composition [300] and 35 percent of a selected perfluoropolymer [110]. The blended fourth composition [400] or third composition alone [300] is then ready for use in profile extrusion. The fourth composition [400] may also comprise inorganic and/or organic additives that include inorganic salts, metallic oxides, silica and silicon oxides as well as substituted and unsubstituted fullerenes. Any combination of compositions [200], [300], and [400] may be combined in any ratio to form a single pelletized product or may be individually pelletized to form a single pelletized product.

[0310] The profile extrusion unit [450] may optionally utilize air or inert gas in addition or in lieu of chemical foaming to adjust the cellular size of the foamed end products [600] which are high performance multi-media cable insulative components [500] for example: wire insulation [510], fiber optic sheathing [520], cable support-separators [530], jacketing [540], wraps [550] and tapes [560]. The blown or foamed insulative components [600] exhibit a smaller and more consistent cell structure than has been previously achieved and at a lower cost than any known present methods.

[0311] It will, of course, be appreciated that the system, method and compositions that have been described have been given simply by the way of illustration, and the disclosure is not limited to the precise embodiments described herein; various changes and modifications may be effected by one skilled in the art without departing from the scope or spirit of the invention as defined in the inventive claims.