Plastic and nonmetallic article shaping or treating: processes – Forming continuous or indefinite length work
Patent
1998-03-03
2000-03-14
Acquah, Samuel A.
Plastic and nonmetallic article shaping or treating: processes
Forming continuous or indefinite length work
528272, 528275, 528296, 528302, 528308, 5283086, 2641771, 264204, 264291, 26433111, 264DIG47, B32B 1118, C08G 6312
Patent
active
060369051
DESCRIPTION:
BRIEF SUMMARY
This application is the national phase under 35 U.S.C. .sctn.371 of prior PCT International Application No. PCT/KR95/00176 which has an International filing date of Dec. 12, 1995 which designated the United States of America, the entire contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates, in general, to a method for preparing polyester film suitable as a base film for magnetic tape and, more particularly, to an improvement in productivity, abrasion resistance and slip properties along with the method.
2. Description of the Prior Art
Polyesters industrially prepared, especially, ones obtained from aromatic dicarboxylic acid and ethylene glycol are extensively used for fibers, films and mold articles by virtue of superior mechanical, physical and chemical properties.
Industrial methods for the preparation of polyesters are typically exemplified by a direct esterification process or ester-interchange process. In the direct esterification, terephthalic acids and ethylene glycols are heated to reaction temperatures ranging from 200 to 280.degree. C. under atmosphere or a pressure, to directly esterify them. On the other hand, the ester-interchange process comprises two steps: first, methyl terephthalates and ethylene glycols are reacted in the presence of catalysts at reaction temperatures ranging from 140 to 240.degree. C., to synthesize prepolymers, that is, bis(beta-hydroxyethyl) terephthalate and/or low molecular weight polymers thereof (hereinafter "esterified compounds"); and, in the second step, the synthesized, esterified compounds are polycondensed in the presence of polymerization catalysts at higher reaction temperatures ranging from 260 to 300.degree. C. in vacuo, so as to obtain high molecular weight polymers.
Polyester films are generally superior in thermal resistance, mechanical properties, dimensional stability, and electric insulation and useful for a plurality of purposes including industrial field, such as magnetic recording film, photofilm, insulating substance and film for deposition, and agricultural field. Also, their consumption amount as a package use for food or other materials has sharply increased because of good chemical properties, transparency, odor preservativity, water resistance and gas barrier.
Slip property and abrasion resistance of polyester film as well as its composition significantly affect the workability in manufacture procedure of polyester film. Particularly, when base films for magnetic tape are manufactured from polyester, these properties are very important to the productivity. For example, if too much diethylene glycol and terminal carboxyl group are contained in a composition for polyester film, thermal stability is degraded, which forces the wiping cycle of extrusion nozzle to be short and thereby lowers productivity. In addition, when melt-extruded sheets are chilled on the surface of a rotary cooling drum, it is difficult to improve the productivity through casting speed if the sheets do not stick fast to the drum. The films thus obtained are nonuniform in thickness, resulting in the production of a magnetic tape with poor electromagnetic characteristics.
And, lack of slip property and abrasion resistance in polyester base film increases the friction between a coating roll and the film upon producing magnetic tapes, leading to generation of crumples and scratches therein. In addition, powder or coating is discontinued by the abrasion of film, which results in drop out of magnetic record.
Recently, it has been indicated that the scratches generated by the contact between the magnetic face and non-magnetic faces at the winding step after the steps of coating of magnetic materials and calendaring degrades the quality of video tapes. Consequently, the polyester film composition which allows the sheets to adhere fast to a drum can improve the productivity and quality of the polyester film and better abrasion resistance and slip property of polyester base film permits the pr
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patent: 4130551 (1978-12-01), Bockrath et al.
patent: 4369207 (1983-01-01), Matsumura et al.
patent: 4980108 (1990-12-01), Suzuki et al.
patent: 5328745 (1994-07-01), Kurihara et al.
patent: 5391429 (1995-02-01), Otani et al.
patent: 5478911 (1995-12-01), Park et al.
Gam Gi Tak
Han Kyung Heum
Park Sang Bong
Acquah Samuel A.
Kolon Industries Inc.
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