Paper making and fiber liberation – Processes and products – Synthetic fiber
Patent
1996-08-27
1998-06-02
Chin, Peter
Paper making and fiber liberation
Processes and products
Synthetic fiber
1621643, 162182, 427212, 428361, 428378, 428395, D21H 1326
Patent
active
057593485
DESCRIPTION:
BRIEF SUMMARY
This invention relates to an aromatic polyamide pulp surface-treated with an epoxy resin and to a process for producing the same. More particularly, it relates to an aromatic polyamide pulp which is easy to handle in the case where an aromatic polyamide pulp is dispersed and mixed with other materials as in friction materials, gasket and the like and which gives a product excellent in mechanical properties, and to a process for producing the same.
Aromatic polyamides such as polyparaphenylene terephthalamide, polymetaphenylene isophthalamide and the like referred to hereinafter as aramids in some cases) are known to be useful for fiber, pulp, film and the like which are excellent in heat resistance, mechanical characteristics, electric characteristics and the like. In particular, aramid pulp obtained by fibrillating aramid fibers is useful as asbestos-substitutes. Processes for producing aramid pulp have heretofore been proposed. As an example, Japanese Patent Application Kokoku No. 59-603 discloses a process for producing aramid pulp by forming a film-like material or a monofilament from an optically anisotropic dope of para-aromatic polyamide and then fibrillating the film-like material or monofilament by a mechanical shear force. Also, Japanese Patent Application Kokai No. 2-200,809 discloses a process for producing aramid pulp directly from a solution of a polymer of a meta-aromatic polyamide, and apparatus to be used therein. When aramid fibers are to be used as reinforcing fibers, it is important that the aramid fibers are excellent in wettability with and adhesiveness to a resin or rubber which is a matrix, and from this view point, various methods have been proposed for the purpose of improving the wettability and adhesiveness between aramid fiber and matrix.
For example, Japanese Patent Application Kokai No. 62-218,425 discloses a method of improving the adhesiveness between an aramid material and an epoxy resin in applying the epoxy resin to the surface of an aramid material (short fiber, long fiber, woven fabric, sheet or the like) by immersing in or spray-coating with an organic solvent solution of an epoxy resin and also applying a heat-treatment thereto in said case. In addition, Japanese Patent Application Kokai No. 62-225,539 discloses a method of improving the adhesiveness of an aramid material to an epoxy resin by heat-treating the aramid material in the presence of an ammonia gas in the application of an epoxy resin to the surface of the aramid material. However, all these methods are concerned with treatment of aramid fibers having a fiber diameter of about 12 .mu.m, and when these methods are applied to highly fibrillated aramid pulp having a fiber diameter of 1 .mu.m or less, the fibrils are adhered to one another to cause a problem of impairing the dispersibility and opening property of the aramid pulp, so that it is difficult to apply the above methods as they are to the aramid pulp.
The object of this invention is to provide an aramid pulp which is used as an asbestos-substitute for friction materials, gaskets and the like and suitable for producing a product excellent in wettability with and adhesiveness to a matrix, such as phenol resin and rubber, and also excellent in inorganic filler retention and exhibits high mechanical properties without impairing the dispersibility and opening property of the aramid pulp.
These and other objects are achieved by the invention, which is summarized as follows. with an epoxy resin whose glycidyl groups have been partially hydrolyzed and having a water content of less than 30% by weight. an epoxy resin and having a water content of less than 30% by weight, characterized by dispersing an aromatic polyamide pulp in an aqueous epoxy 20 resin emulsion, and subjecting the same to filtering, dehydrating, drying and opening. above wherein an aqueous emulsion of an epoxy resin whose glycidyl groups have been partially hydrolyzed is used.
This invention is explained in detail below. The aramid used in this invention, that is, the total aromatic polyamid
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Asagi Kosaku
Yamabayashi Toshiharu
Akzo Nobel nv
Chin Peter
Fennelly Richard P.
Morris Louis A.
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