Chemistry of inorganic compounds – Carbon or compound thereof – Elemental carbon
Patent
1998-01-20
2000-08-15
Griffin, Steven P.
Chemistry of inorganic compounds
Carbon or compound thereof
Elemental carbon
4234471, D01F 600
Patent
active
061032115
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to carbon fibers, acrylic fibers (precursor fibers) preferably used for producing the carbon fibers, and production processes thereof. In more detail, the present invention relates to carbon fibers satisfying specific relations not satisfied by the conventionally known carbon fibers, expressed as tensile strength of a resin impregnated strand of the carbon fibers, and as the average diameter of single filaments constituting the carbon fibers, and also as acrylic fibers (precursor fibers) preferably used for producing said carbon fibers, and production processes thereof.
BACKGROUND ARTS
Carbon fibers have been applied for sporting goods and aerospace materials because of their excellent specific strength and specific modulus, and are being used in wider ranges in these fields.
On the other hand, carbon fibers are also used for forming energy related apparatuses such as CNG tanks, fly wheels, wind mills and turbine blades, as materials for reinforcing structural members of roads, bridge piers, etc., and also for forming or reinforcing architectural members such as timber and curtain walls.
Since that carbon fibers are being applied in wider fields, they are demanded to have higher tensile strength when expressed as a resin impregnated strand than before, and for further expanding applicable fields, the carbon fibers are demanded to be produced at lower cost.
The conventional techniques for improving tensile strength of carbon fibers as a resin impregnated strand have been concerned with decrease of macro-defects, for example, for decreasing impurities existing inside single filaments constituting the carbon fibers, or for inhibiting the production of macro-voids formed inside the single filaments, and for reducing defects generated on the surfaces of the single filaments.
To decrease the inner impurities and macro-voids of single filaments, techniques to intensify the filtration of monomer or polymer dope are proposed in Japanese Patent Laid-Open (Kokai) No. 59-88924 and Japanese Patent Publication (Kokoku) No. 4-12882. Furthermore, techniques to inhibit the production of surface defects by controlling the shape of fiber guides used in the production process of precursor fibers or controlling the tension of fibers in contact with a guide are proposed in Japanese Patent Publication (Kokoku) No. 3-41561.
Although they were effective in improving strength in the past, when the tensile strength level of carbon fibers as a resin impregnated strand was low, the techniques have already achieved their intended effects of strength improvement, as impurities and macro-voids have been almost perfectly removed. In other words, these techniques cannot be expected to improve the strength further.
Furthermore, when precursor fibers are stabilized and carbonized at a high temperature to produce carbon fibers, coalescence between single filaments is likely to occur, and the coalescence between single filaments and marks that remain after their separation cause surface defects, and lower the fiber strength.
To inhibit coalescence between single filaments, techniques for impregnating precursor fibers with fine particles of graphite in the production process of precursor fibers are proposed in Japanese Patent Laid-Open (Kokai) No. 49-102930 and Japanese Patent Publication (Kokoku) No. 6-37724, and a technique for impregnating precursor fibers with fine particles of potassium permanganate is proposed in Japanese Patent Publication (Kokoku) No. 52-39455.
The addition of these fine particles was effective in improving strength in the past when the coalescence between filaments occurred frequently and the tensile strength of carbon fibers as a resin impregnated strand was at a low level. However, today when the coalescence between filaments has been decreased to improve the strength level due to the application of the above techniques, these hard inorganic fine particles impregnated onto soft swelling fibers during production cause surface defects and lower the tensile strength of t
REFERENCES:
patent: 5209975 (1993-05-01), Miyazaki et al.
patent: 5348802 (1994-09-01), Matsuhisa et al.
Kibayashi Makoto
Matsuhisa Yoji
Okuda Akira
Yamasaki Katsumi
Griffin Steven P.
Hendrickson Stuart L.
Miller Austin R.
Toray Industries Inc.
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