Stock material or miscellaneous articles – Composite – Of polyester
Patent
1999-05-06
2000-04-25
Acquah, Samuel A.
Stock material or miscellaneous articles
Composite
Of polyester
428458, 4284735, 428480, 428626, 4174101, 181403, 156 51, 156 56, 174107, 174110R, 174119R, 174120R, 174110SR, 174137R, B32B 2706, H01B 1700
Patent
active
060542241
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to polyester films and to composite films for electrical insulation. More particularly, the present invention relates to a polyester film and to a composite film which are used for insulation of compressor motors in cooling systems such as refrigerators and air conditioners, are used for a variety of electrical insulation, contains reduced amounts of oligomers, improves set stability after assembly, facilitates confirmation of set assembly by being colored, and improves machinability and processability, and can reduce leakage of current.
BACKGROUND ART
Polyester films having high intrinsic viscosity have been conventionally used to reduce oligomers, and terminal blocking agents have been used to improve hydrolysis resistance of the polyester films.
Although various heat-resistant films have been used to simultaneously satisfy the above properties, the films still have some problems, such as increased cost, difficult set assembly, unsatisfactory stability after set, and insufficient machinability and processability.
Japanese Patent Application Laid-Open No. 9-100363 discloses a heat-resistant, low-dielectric plastic insulating film having voids and a dielectric constant lower than a particular value. The film has a low dielectric constant to reduce leakage power dissipation in an insulating section caused by high-frequency trends of instruments. Low oligomer contents and ready set assembly when the film is used in electrical insulation, however, are not taken into consideration, and thus the film is not durable in practice. Japanese Patent Application Laid-Open No. 5-194773 discloses a polyester film having a specified apparent density and a tensile modulus, but use of the film in electrical insulation has not been suggested.
These electrical insulating films have the following problems. oils causing lower levels of environmental pollution are being used. Further reduction in oligomers have been awaited in order to achieve this. results in increased costs. machinability and processability (in thermoforming and slit bending processing), insufficient stability after set assembly (such as displacement and being loose), and insufficient visibility. current.
It is an object of the present invention to solve these problems.
DISCLOSURE OF INVENTION
The present invention provides an electrical insulating polyester film having an apparent density of 1.37 to 0.85 g/cm.sup.3 and a tensile modulus of 2.0 to 4.5 GPa. The present invention also provides an electrical insulating polyester film having the above characteristics and a dielectric constant of 2.2 to 3.0.
The present invention further provides an electrical insulating composite film comprising a heat-resistant film laminated on at least one face of the polyester film, the heat-resistant film having heat resistance higher than that of the polyester film.
The present invention further provides an insulating system in which the electrical insulating polyester film or the electrical insulating composite film is used for electrical insulation in an environment comprising a refrigerating medium of partially-hydrogenated halogenated hydrocarbon as a primary component and a polar oil, and an hermetic-type compressor comprising a motor in which the insulating system is used for insulating an exciting coil.
BEST MODE FOR CARRYING OUT THE INVENTION
Polyester used in a polyester film of the present invention is a crystalline thermoplastic resin composition which is polymerized by esterification, and such polyester is obtained by polycondensation of a dicarboxylic acid component and a glycol component.
Examples of dicarboxylic acid components used include terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid, cyclohexane dicarboxylic acid, and diphenylethane dicarboxylic acid. Examples of glycol components used include ethylene glycol, propylene glycol, tetramethylene glycol, and cyclohexane dimethanol. Among these, preferable acid components are terephthalic acid and naphthalene-2,6-dicarboxylic acid, and
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Tetrahedron Lett., (month unavailable) 1967, pp. 961-62.
Aoki Seizo
Deguchi Yukichi
Nagai Itsuo
Acquah Samuel A.
Miller Austin R.
Toray Industries Inc.
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