Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
2000-06-15
2001-06-12
Edwards, N. (Department: 1774)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C428S394000, C264S206000
Reexamination Certificate
active
06245423
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to thick carbon fiber precursor acrylic tows containing at least 20,000 filaments, with high quality and high productivity, as well as methods of producing and using the same.
2. Description of the Background
Demand for carbon fibers has increased in recent years, since they are widely used in premium applications, such as in airplane and sporting goods manufacture, and in general industrial applications typified by civil engineering. To satisfy the increasing demand of fibers for such applications, a drastic reduction in the cost of production of fibers, as well as an increase in fiber production capacity has been required. As a means for increasing the productivity of acrylic fiber tows as the precursor of carbon fibers, it has been found not to be effective to increase the total denier of the fibers by increasing the number of single fibers constituting the tows and to improve productivity per setup.
According to conventional methods of production, a spinning dope is guided into a coagulation bath to prepare coagulated tows. To guide and draw the tows, a plurality of rollers is used to transfer the tows before they are dried and compacted. However, when the total size of the tows is increased, the existing setups that are based on 12,000 filaments suffer from the disadvantage that the gap between the tows of adjacent weights becomes small and mutual interference and blending of the tows occur. As a result, damage of the single fiber, breakage, fluff and bonding, for example, occur and the process approval factor deteriorates. At the same time, a non-uniform size in a subsequent drawing processes invites non-uniformity of the size and also eventually, a deterioration of the properties of the resulting carbon fiber.
In order to prevent such a problem, the width of each roller must be widened in order to enlarge the gap between the tows of the adjacent weights. In this case, large modification of the setups, inclusive of a driving unit, must be made. If the roller is widened excessively, the guide operation of the tow and counter-measures to cope with problems become more difficult. These problems raise serious problems from the standpoint of safety.
Japanese Patent Laid-Open No. 5-195306 describes a method of controlling the tow width by using curved guides during the processing inside a bath. While this method allows for control of the tow width between the guides inside the bath, however, the problem of mutual interference and blending of the tows remains problematic on the rollers where problems are more likely to occur. Moreover, the weight variation ratio in the longitudinal direction of the tow made by prior art method is very large. As the result, the tensile strength in the longitudinal direction of the tow is not uniform. At the same time, the process approval factor deteriorates and non-uniform oiling occurs. The properties of the resulting carbon fiber deteriorate also.
Thus, a need continues to exist for a method of producing acrylic fiber tows for carbon fiber production which overcomes the above disadvantages.
SUMMARY OF THE INVENTION
Accordingly, one object of the present invention is to provide a thick acrylic fiber tow for carbon fiber production, wherein mutual interference and blending of the adjacent acrylic fiber tows is prevented during the production of the acrylic fiber tows, and to methods of producing and using the tow.
Another object of the present invention is to provide thick acrylic fiber tows for carbon fiber production having a total size of at least 22,000 dtex.
Still a further object of the present invention is to provide a method of producing the above described acrylic fiber tow.
Briefly, these objects and other objects of the present invention as hereinafter will become more readily apparent can be attained by a thick acrylic fiber tow, as a precursor for the production of carbon fibers, having a total size of at least 22,000 dtex and a weight variation ratio in a longitudinal direction of not greater than 3.5%.
REFERENCES:
patent: 5348802 (1994-09-01), Matsuhisa et al.
patent: 5401576 (1995-03-01), Yoon et al.
patent: 5-140815 (1993-06-01), None
patent: 5-195313 (1993-08-01), None
patent: 10-215924 (1998-09-01), None
patent: 11-12874 (1999-01-01), None
Fukuen Nobuyuki
Ikeda Katsuhiko
Makishima Toshihiro
Edwards N.
Mitsubishi Rayon Co. Ltd.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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