Fluororesin composite compositions

Abstract

The present invention relates to a heat-meltable fluoropolymer composite composition having excellent thermal conductivity, gas and chemical liquid barrier properties and dynamic properties such as storage modulus which comprises a heat-meltable fluoropolymer fine powder and a layered-compound organized by treatment with tetraphenyl phosphonium ions. The present invention also relates to a heat-meltable fluoropolymer composite composition having similar properties to those mentioned above which is obtained by a process (I) in which a heat-meltable fluoropolymer composite composition is obtained by grinding and mixing a heat-meltable fluoropolymer fine powder and a layered-compound and a process (II) in which such heat-meltable fluoropolymer composite composition thus obtained is melted and mixed under shear stress by means of a melt-mixing extruder.

Description

TECHNICAL FIELD [0001] The present invention relates to a heat-meltable fluoropolymer composite composition having excellent thermal conductivity, gas and chemical liquid barrier properties, and dynamic properties such as storage modulus. More specifically, the present invention relates to a heat-meltable fluoropolymer composite composition having excellent thermal conductivity, gas and chemical liquid barrier properties, and dynamic properties such as storage modulus which comprises a heat-meltable fluoropolymer fine powder and a particular organically-modified layered-compound. The present invention further relates to a heat-meltable fluoropolymer composite composition having excellent thermal conductivity, gas and chemical liquid barrier properties, and dynamic properties such as storage modulus which is obtained by mixing a heat-meltable fluoropolymer fine powder and a layered-compound in advance so that the layered-compound is dispersed uniformly in the fine heat-meltable fluor...

AI Technical Summary

Benefits of technology

[0007] The inventors of the present invention have paid notice that the thermal conductivity, gas and chemical liquid barrier properties and dynamic properties such as storage modulus of a heat-meltable fluoropolymer composite can be improved by dispersing a layered-compound in which normally the unit crystal laminas constituting the layered-compound are present in such form that they are piled, further exfoliating (hereinafter referred to as “cleavage” in some cases) part of the layered-compound thus dispersed or exfoliating heat-meltable fluoropolymer between the laminas of the layered-compound so that the number of the laminas of the layered-compound is increased even if the weight percent of the layered-compound laminas that are present in the heat-meltable fluoropolymer is same. As a result, the inventors have found that a heat-meltable fluoropolymer composite composition having excellent thermal conductivity, gas and chemical liquid barrier properties and dynamic properties such as storage modulus can be provided.

[0008] The present invention provides a heat-meltable fluoropolymer composite composition having excellent thermal conductivity, gas and chemical liquid barrier properties and dynamic properties such as storage modulus. Specifically, the present invention provides a heat-meltable fluoropolymer composite composition comprising a heat-meltable fluoropolymer fine powder and a layered-compound organically modified by treatment with tetraphenyl phosphonium ions. Use of such particular layered-compound makes it possible to obtain a heat-meltable fluoropolymer composite composition having excellent thermal conductivity, gas and chemical liquid barrier properties and dynamic properties such as storage modulus only by melt-mixing such layered-compound by exerting shear stress by use of a melt-mixing extruder.

[0009] The present invention also provides a heat-meltable fluoropolymer composite composition which is obtained by a process (I) in which a heat-meltable fluoropolymer powdery composition is obtained by mixing a heat-meltable fluoropolymer fine powder and a layered-compound and a process (II) in which such heat-meltable fluoropolymer powdery composition thus obtained is melt-mixed by exerting shear stress by means of a melt-mixing extruder. Combination of these processes (I) and (II) makes it possible to obtain a heat-meltable fluoropolymer composite composition with satisfactory physical properties even by using any layered-compound other than the aforesaid particular layered-compound. It is thought that a heat-meltable fluoropolymer composite composition having excellent thermal conductivity, gas and chemical liquid barrier properties and dynamic properties such as storage modulus is obtained as a result of the layered-compound is dispersed, exfoliated or exfoliated more uniformly in the heat-meltable fluoropolymer under process (II) in which the materials are melt-mixed under shear stress, in addition to the mixing under process (I). Especially, an excellent effect in improving the physical properties can be produced by using a layered-compound organically modified by treatment with organic phosphonium ions, preferably tetraarylphosphonium ions, more preferably tetraphenylphosphonium ions.

Problems solved by technology

However, the tubes made of these resins have to be replaced periodically owing to such problems as the contamination of the peripheral devices and environmental pollution due to the permeation of the chemical liquid.

Furthermore, when these resins are used for the heat exchanger tubes in an alkali tank, the tubes show low thermal conductivity, and therefore there is also a demand for materials exhibiting higher thermal conductivity.

However, the aforesaid polymerization method cannot be said to be economical because although the polymerization method allows the filler to be dispersed efficiently, it requires polymerization equipment, entailing high cost.

Besides, since the monomer that is inserted between the laminas of the aforesaid layered clay mineral will not stay stably between the laminas, a gas monomer is not preferable, and the choice of the monomer is limited to a liquid monomer.

However, such method essentially requires the use of a large amount of an organic solvent in causing a layered clay mineral to be swelled, but a fluoropolymer has the problem of extremely low compatibility with an organic solvent.

On top of that, the infinite-swollen layered-compound by use of the aforesaid organic solvent also has the problem of returning to a swollen state from such infinite-swollen state as part of the organic solvent will evaporate at the temperature of extrusion of the fluoropolymer in such process of coming into contact with the melted resin.

However, there was no significant improvement reported in the mechanical properties of a composite mixture in which the layered clay mineral was dispersed which had been organized to some extent by melting and mixing the layered clay mineral by means of a twin-screw extruder of the non-intermeshing type with the result that the inter-layer distance was increased (Plastic Engineering, P56, 2001).

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