Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Patent
1998-02-10
2000-03-21
Krynski, William
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
428359, 428375, 428378, 428408, 4234471, 4234472, 4234473, 523205, 523215, 524496, 427384, B32B 900
Patent
active
06040051&
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to carbon fibers which are useful mainly for producing a fiber-reinforced thermoplastic resin composition by mixing them with a resin and a process for their production, and a fiber-reinforced resin composition employing them.
DESCRIPTION OF THE BACKGROUND
In recent years, a fiber-reinforced resin composition having carbon fibers mixed and dispersed in various matrix resins, has attracted an attention as an industrially important material by virtue or its mechanical properties such as high strength, high rigidity, low specific gravity and high abrasion resistance. Particularly, in the field of electronic products for which downsizing and weight reduction have recently been progressing, molded parts of a highly rigid fiber-reinforced resin composition have been developed for application as substitute material for metal. Heretofore, in a case where such carbon fibers are mixed and dispersed in various resins to obtain a fiber-reinforced resin material, it has been common to employ a method wherein a plurality of long carbon fibers are preliminarily bundled by a resin so-called a sizing agent and then cut into short carbon fibers, which are used to be mixed with the matrix resins.
To improve the performance of such a fiber-reinforced resin composition, it is important to increase the fiber content, and for this purpose, it has been important to obtain carbon fibers having a high bulk density.
However, heretofore, if it is attempted to cut carbon fiber strands having a high yield (the weight per 1 m of a carbon fiber strand) for the purpose of obtaining carbon fibers having a high bulk density, there has been a problem that the strands get loose, and fuzz (a few or a few tens carbon fibers separated from the main bodies of the strands) will form. Namely, carbon fibers of fine strands having a low yield, can easily be cut, but cutting of carbon fibers of thick strands having a high yield has been difficult, accompanied with loosening of the strands and formation of fuzz.
Further, when such carbon fibers are mixed with a resin, fuzz are likely to interlock one another, whereby the flowability of carbon fibers in the feeder for feeding the carbon fibers, tends to be poor, and a constant amount feeding tends to be difficult. Thus, it has been difficult to uniformly disperse such carbon fibers in the resin.
Therefore, the yield of carbon fibers in this field, particularly pitch type carbon fibers, which have been known heretofore, has been at a level of 0.8 g/m at best, and carbon fibers excellent in flowability, while having a higher yield, have been desired.
SUMMARY OF THE INVENTION
The present inventors have conducted extensive studies to solve such a problem and as a result, have found to their surprise that when carbon fibers having a high yield fuzzed by cutting are subjected to stirring treatment, fuzz will gather one another to form pills (spherical products having diameters of from 3 to 100 mm formed by interlocking of fuzz), which will be separated from the main bodies of the carbon fiber strands. And it has been found that with the carbon fibers separated from the pills, the flowability is remarkably improved.
The object of the present invention is to obtain carbon fibers which have a high bulk density and have the drawbacks resulting at the time of producing a fiber-reinforced resin material overcome, and which have good handling efficiency and are excellent in operation efficiency in the dispersing step, and further to obtain a fiber-reinforced resin composition which contains carbon fibers having a high bulk density and which has a high fiber content.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Namely, the gist of the present invention resides in carbon fibers which are carbon fibers obtained by bundling carbon fibers having a yield of at least 0.9 g/m, followed by cutting, and which are characterized in that the following collapse initiating angle and funnel drop time are at most 65.degree. and at most 20 seconds, respectively;
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Inoue Yoshiaki
Kakikura Eisaku
Kinouchi Masami
Shiotsu Tamotsu
Yamamoto Iwao
Gray J. M.
Krynski William
Mitsubishi Chemical Corporation
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