Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1998-03-16
2001-03-06
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S439000, C524S440000, C524S492000, C524S493000, C524S494000, C524S495000, C524S496000, C524S449000
Reexamination Certificate
active
06197862
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a filler-containing polytetrafluoroethylene granular powder and a preparation process thereof.
BACKGROUND ART
Hitherto, a process for preparing a filler-containing polytetrafluoroethylene (PTFE) granular powder by granulating a mixture of a filler and a PTFE powder with stirring in water was proposed, for example, in JP-B-8611/1968, JP-B-22619/1969, JP-B-37576/1973, JP-B-17855/1974, JP-B-8044/1981, JP-B-18730/1982, etc.
However, by the process for preparation disclosed in each of the above-mentioned patent publications, a filler-containing PTFE granular powder having a small particle size and a sharp particle size distribution could not be obtained.
For that reason, in case of preparing, for example, small articles such as seal rings in the form of a rubber band, thin moldings and molded products having a small surface roughness, there was a problem such that complicated and uneconomical steps must be employed, such as step of sieving a filler-containing PTFE granular powder to take out only particles of small size and molding them, or step of cutting the obtained molding.
Also a granular powder having excellent powder flowability cannot be obtained by only pulverizing a filler-containing PTFE granular powder.
In JP-B-21694/1985, there was proposed a process for preparing a filler-containing PTFE granular powder by granulating, with stirring in water, a PTFE powder and a filler which has been previously surface-treated with an aminosilane compound in coexistence with a water-insoluble organic liquid and an anionic surfactant. However, an apparent density of the filler-containing PTFE granular powder and tensile strength of molded products obtained therefrom are not fully satisfactory.
The present inventors have made intensive studies in view of the above-mentioned problems, and as a result, have found that those problems can be solved by granulating a mixture of a PTFE powder and a filler in the presence of an organic liquid which forms liquid-liquid interface with water, and a nonionic surfactant with stirring in water.
Namely, an object of the present invention is to provide a filler-containing PTFE granular powder having a good processability and a process for preparation thereof. Particularly an object of the present invention is to provide a filler-containing PTFE granular powder having a large apparent density, a small average particle size, a sharp particle size distribution and good physical properties such as powder flowability, which gives molded products having excellent physical properties such as elongation and surface smoothness, and a process for preparation thereof.
DISCLOSURE OF THE INVENTION
The present invention relates to a process for preparing a filler-containing polytetrafluoroethylene (PTFE) granular powder which is characterized in that a mixture of a polytetrafluoroethylene (PTFE) powder and a filler is granulated with stirring in water in the presence of an organic liquid which forms liquid-liquid interface with water, and a nonionic surfactant.
By the above-mentioned process, a filler-containing PTFE granular powder having an apparent density of not less than 0.6 g/cm
3
can be obtained.
The present invention also relates to a filler-containing PTFE granular powder, in which when an apparent density (d) is 0.6≦d<0.9, 0.9≦d<1.0 and 1.0≦d, an angle of repose is not more than 40 degrees, not more than 38 degrees and not more than 36 degrees, respectively and an average particle size is not more than 500 &mgr;m.
REFERENCES:
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patent: 5189143 (1993-02-01), Honda et al.
patent: 5306739 (1994-04-01), Lucey
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patent: WO 93/16126 (1993-08-01), None
Chereshkevich at al., “Filled Poly(tetrafluoroethylene)”, Chemical Abstracts, vol. 70, No. 6, Abstract No. 2097768, Feb. 10, 1969, Columbus, Ohio.
Asano Michio
Kawachi Shoji
Shimizu Tetsuo
Sukegawa Masamichi
Tanigawa Shingo
Armstrong, Westerman Hattori, McLeland & Naughton
Cain Edward J.
Daikin Industries Ltd.
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