Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Patent
1999-03-19
2000-04-11
Edwards, Newton
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
428394, 428400, 428373, 525440, D01F 814, D01F 694
Patent
active
060486139
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to polyurethane elastic fiber and a process for producing the same.
BACKGROUND OF THE INVENTION
The polyurethane elastic fiber has excellent stretching properties and is widely used in the fields of hosiery, underwear, sportswear etc.
Known processes for producing the polyurethane elastic fiber include a wet spinning method where a polyurethane solution is extruded and coagulated by passage through a coagulation bath, a dry spinning method where solvent is vaporized with hot air, or a melt spinning method where thermoplastic polyurethane is melted and extruded followed by solidification by cooling with air. Among these spinning processes, the melt spinning process is particularly advantageous in that organic solvent with strong possibility of polluting the human body and the environment is not used, so this process recently has attracted considerable attention as a spinning process which is not detrimental to the environment.
The melt spinning process is a process in which melted polyurethane is extruded through a spinning nozzle into air, solidified by cooling and wound as described above, so unlike the dry or wet spinning process, no volatiles are contained from the melting step to the cooling and solidification step. Accordingly, this melt spinning process is characterized in that the surface of the resulting fiber is frat and free of the uneven surface generated upon removal of volatiles from the inside of the fiber. Because of these characteristics, the polyurethane elastic fiber produced by the melt-spinning process is superior in wear resistance and further possesses the property of glistening.
However, relatively thin knitted goods such as stockings, tights, sox etc. have the disadvantage of too high glistening due to the above surface property of polyurethane elastic fiber. For example, black knitted goods generate glossy black luster. In stockings, tights, sox etc. made of covered fiber having nylon fiber etc. wound around the polyurethane elastic fiber, this luster phenomenon occurs very significantly due to relatively low degrees of coverage on the polyurethane elastic fiber.
To reduce the luster phenomenon, there is a method of increasing the number of twisting in the covering step in order to increase degrees of coverage. However, there is the disadvantage that the fiber is felt hard in proportion with an increase in the number of twisting for coverage. Further, there is also a method of dyeing the polyurethane elastic fiber darkly (e.g. black). However, the reduction in luster attained in this method is slight so significant improvements cannot be achieved.
There is also a known method of decreasing the luster phenomenon by roughening the surface of fiber. For example, there is a general method of roughening the surface of polyethylene terephthalate fiber by mixing inorganic fine particles with a polymer to form fiber and then dissolving and removing the surface of the fiber with a chemical such as alkali etc. to cause the inorganic fine particles to be removed therefrom so that the surface of the fiber is roughened.
Although this method is effective for polyethylene terephthalate fiber, it cannot be applied to polyurethane elastic fiber because there is no suitable chemical which can dissolve and remove the fiber surface.
Further, there is a method in which a large amount (e.g. about 30 to 40% by weight) of inorganic fine particles are previously mixed with a polyurethane polymer and melt-spun, and the surface of the resulting fiber is roughened in the step of solidifying the fiber by cooling. In this method, however, because a large amount of inorganic particles are contained in the polymer, the melt fluidity of the polymer is lowered, and in melt spinning, the polymer clogs a spinning nozzle, or fiber cutting frequently occurs to make spinning substantially infeasible. Even if spinning is feasible, the physical properties of fiber, such as strength, elongation etc. are significantly deteriorated.
In production of polyurethane elasti
REFERENCES:
patent: 4034016 (1977-07-01), Baron et al.
patent: 5319039 (1994-06-01), Moses et al.
patent: 5502120 (1996-03-01), Bhatt et al.
Kawata Teruyoshi
Nakai Yasushi
Tokutomi Shigeru
Yamakawa Yukio
Yoshimoto Kiyoshi
Edwards Newton
Kanebo Limited
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