Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1997-02-03
1998-05-12
Schofer, Joseph L.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
524100, 524208, 524255, C08K 320
Patent
active
057506060
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELDS
The present invention relates to an aqueous fluorine-containing polymer dispersion, and particularly relates to an aqueous fluorine-containing polymer dispersion comprising a fluorine-containing polymer, a nonionic surfactant and a preservative. An aqueous fluorine-containing polymer dispersion containing a polytetrafluoroethylene resin, which is one of the aqueous fluorine-containing polymer dispersions of the present invention, is coated on base materials, for instance, glass clothes, carbon fibers and the like and used suitably, for example, for a conveyor belt, an architectural fabric (sheet for an air dome), a packing, a printed circuit board for high frequency and the like.
BACKGROUND ARTS
Among aqueous fluorine-containing polymer dispersions, an aqueous polytetrafluoroethylene resin dispersion (hereinafter may be referred to as "PTFE dispersion" or "PD") is explained below as a representative example.
In order to obtain dispersion stability of PTFE primary particles in a PTFE dispersion, for example, nonionic surfactants such as poly(oxyethylene alkyl ether) represented by R--O--(CH.sub.2 CH.sub.2 O).sub.n H (wherein R is an alkyl group or an alkenyl group, n is an integer of 2 to 18) or poly(oxyethylene alkylphenyl ether) represented by ##STR1## (wherein, R is an alkyl group or an alkenyl group, n is an integer of 2 to 18) have been hitherto mixed in an amount of, for instance, 3 to 10 parts by weight, preferably 5 to 8 parts by weight per 100 parts by weight of PTFE.
However the nonionic surfactants mixed in the above-mentioned PD are easy to become nutriments for microorganisms, for example, bacteria, mildews, yeasts and the like. Particularly in case of a temperature of not less than 30.degree. C. in summer time, bacteria (air-borne bacteria) become remarkably active, and there occur malodor, brown suspended matters of dead bacteria and the like, which markedly lower product value.
In order to obtain dispersion stability of the PTFE primary particles, pH of the above-mentioned PD is adjusted at 9 to 11 by means of alkaline substances such as aqueous ammonia. However since the pH lowers to about 7 to about 8 due to the above-mentioned air-borne bacteria, stability of the PTFE primary particles in the PD lowers and aggregation is easy to occur.
Also the above-mentioned PD is impregnated in glass clothes, and used, for instance, for a sheet for an air dome, a printed circuit board, a conveyor belt and the like. During the impregnation work, however, the PD is contaminated with a sizing agent such as starch and the like being contained in the glass clothes, and such an agent becomes nutriments for bacteria. As a result, the PD used once for the impregnation becomes remarkably easy to be putrefied depending on storage conditions, and cannot be stored for a long period of time.
As properties required for a preservative for the above-mentioned PD, there are desired amount, and no coloration shall occur when blending with the PD; like, and particularly antibacterial activity against Gram negative bacterium which is a main cause for putrefaction shall be high and an antibacterial effect shall be maintained for a long period of time (about 6 months). temperature of not more than 50.degree. C. and shall be decomposed quickly at a temperature of not less than 200.degree. C., and no decomposed substances such as carbides shall remain at a temperature around a melting point of PTFE. on the PD, and, when the PD is impregnated in fabrics such as glass clothes and carbon fibers, shall not cause undesired states such as cissing and aggregation on the fabrics.
The present circumstances are such that there has been reported no preservative for PD, which satisfies those properties, and that the PD mixed with the preservatives has not yet been obtained.
An object of the present invention is to provide an aqueous fluorine-containing dispersion which assures, by mixing a preservative to the above-mentioned PD, that the nonionic surfactants become difficult to be affected by the air-borne bacteria,
REFERENCES:
patent: 3833731 (1974-09-01), Grier et al.
patent: 4655815 (1987-04-01), Jakubowski
patent: 4945109 (1990-07-01), Rayudu
Hayashi Tadao
Miura Toshiro
Soda Yoshihiro
Daikin Industries Ltd.
Sarofin N.
Schofer Joseph L.
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