The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jan. 06, 1998
Filed:
May. 17, 1996
Atsuko Ueda, Aichi, JP;
Tetsuo Matsumoto, Nara, JP;
Nippon Ester Co., Ltd., Okazaki, JP;
Abstract
A process for producing a polyester film is disclosed, which comprises melt-mixing from 3 to 12 parts by weight of a master polymer comprising a poly(alkylene terephthalate) which contains from 0.3 to 3 wt % inorganic lubricant and has an intrinsic viscosity of 0.5 or higher with from 97 to 88 parts by weight of a poly(alkylene terephthalate) containing no inorganic lubricant and having an intrinsic viscosity of 0.5 or higher, and forming the resulting mixture into a film by the electrostatic casting method. The master polymer is obtained by a process comprising adding to a poly(alkylene terephthalate) oligomer having an average degree of polymerization of 10 or lower an alkylene glycol slurry of an inorganic lubricant and specific amounts of a potassium compound and a phosphorus compound, depolymerizing the oligomer, subsequently adding specific amounts of antimony trioxide and germanium dioxide, and then effecting polycondensation. By this process, a polyester film having an excellent color tone can be produced with a high producibility and a high operation efficiency.