Stock material or miscellaneous articles – Composite – Of fluorinated addition polymer from unsaturated monomers
Reexamination Certificate
1999-11-19
2002-11-05
Thibodeau, Paul (Department: 1773)
Stock material or miscellaneous articles
Composite
Of fluorinated addition polymer from unsaturated monomers
C428S422000, C428S473500, C427S393500
Reexamination Certificate
active
06475624
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a polyimide/fluororesin laminate, and an insulating tape for wire-winding obtained by processing the laminate into a tape form. More particularly, the present invention relates to a polyimide/fluororesin laminate, and an insulating tape for wire-winding being excellent in hydrolysis resistance. The polyinde/fluororesin laminate of the present invention is wound in a tape form around a conductor such as copper, and is used for a coil or a cable in a motor, a wire in an aircraft, or the like.
2. Description of Related Art
Polyimide has excellent properties such as electric insulation, heat resistance, and chemical resistance. A polyimide/fluororesin laminate, which is obtained by coating one or both surfaces of a polyimide film with fluororesin, is advantageously processed into a tape form and used for coating a conductor to produce a coated wire.
Especially, in recent years, electric devices are becoming more and more efficient and highly functional, leading to wide use of these electric devices under a high temperature and high humidity environment. Further, the amount of electric current through a wire is increasing, and the wire is often exposed to higher temperatures in accordance with heat generation.
Under these environments, however, there is a problem that the polyimide resin in the polyimide/fluororesin laminate undergoes hydrolysis, thereby decreasing the dielectric breakdown voltage of the coated portion.
SUMMARY OF THE INVENTION
The inventors of the present invention have made an eager research to solve the above-mentioned problems of the prior art and to provide a polyimide/fluororesin laminate being excellent in hydrolysis resistance and an insulating tape for wire-winding using the same. As a result, using a polyimide film having a high resistance to an environment of high temperature and high humidity, the inventors of the present invention have found out that a polyimide/fluororesin laminate and an insulating tape for wire-winding being excellent in hydrolysis resistance can be obtained. Further, the inventors have found out that a polyimide film containing at least one kind of an element selected from the group consisting of Al, Si, Ti, Mn, Fe, Co, Cu, Zn, Sn, Sb, Pb, and Bi has an excellent resistance to the environment of high temperature and high humidity, thereby completing the present invention.
A polyimide/fluororesin laminate according to the present invention comprises a polyimide film and a fluororesin layer and is characterized in that a retention of tear propagation resistance strength of the polyimide film after being exposed to 150° C. 100% RH environment for 12 hours is not less than 80% of the tear propagation resistance strength of the polyimide film before exposure.
Further, in the polyimide/fluororesin laminate according to the present invention, the polyimide film contains at least one kind of an element selected from the group consisting of Al, Si, Ti, Mn, Fe, Co, Cu, Zn, Sn, Sb, Pb, and Bi.
An insulating tape for wire-winding according to the present invention is obtained by processing a polyimide/fluororesin laminate of the invention into a tape form.
Since the polyimide/fluororesin laminate according to the present invention is made of polyimide having a high resistance to a high temperature and high humidity environment, it is excellent in hydrolysis resistance and, when the laminate is processed into a tape form and wound around a conductive wire, a coated wire being excellent in hydrolysis resistance is obtained. This provides an advantage that an insulating tape for wire-winding is provided which can be used for a coil or a cable in a motor, a wire in an aircraft, or the like, operating with no quality defect under a severe environment of high temperature and high humidity.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The term “gel film” as used herein in the present invention means a film in a partially cured or partially dried state in the reaction process of imidizing polyamic acid to form polyimide, in which the polyamic acid is mixed with the polyamide imidized, which has self-supporting properties. And the term “retention” in the present invention means a ratio of a tear propagation resistance strength of a polyimide film after being exposed to 150° C. 100% RH environment for 12 hours against the initial tear propagation resistance strength of the polyimide film before exposure.
The polyimide/fluororesin laminate according to the present invention is characterized in an excellent resistance to hydrolysis. In particular, it is a polyimide/fluororesin laminate being excellent in resistance to hydrolysis which is obtained by using a polyimide film having an excellent resistance under a high temperature and high humidity environment. Specifically, a polyimide film having a high retention of tear propagation resistance strength after being exposed to a high temperature and high humidity environment.
Hereafter, embodiments of the polyimide/fluororesin laminate according to the present invention will specifically be described.
First, explanation will be given on a polyimide film capable of being used in the polyimide/fluororesin laminate according to the present invention.
The polyimide film to be used in the present invention can be produced by a known method. Namely, it is produced by applying an organic solvent solution of polyamic acid, which is a precursor of the polyimide, onto a support by flow casting, and chemically or thermally imidizing the polyamic acid.
The polyamic acid as a precursor of the polyimide used in the present invention is typically produced by dissolving at least one kind of an aromatic acid dianhydride and at least one kind of diamine in substantially equimolecular ratios in an organic solvent and stirring the solution under a controlled temperature condition until the polymerization is completed.
Examples of suitable acid anhydrides for use in synthesis of the polyamic acid according to the present invention include pyromellitic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 3,3′,4,4′-biphenyltetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 2,2′, 3,3′-biphenyltetracarboxylic dianhydride, 3,3′4,4′-benzophenonetetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl)propane dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, 1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, bis(3,4-dicarboxyphenyl)ethane dianhydride, oxydiphthalic dianhydride, bis(3,4-dicarboxyphenyl)sulfone dianhydride, p-phenylenebis (trimellitic acid monoester acid anhydride), ethylenebis(trimellitic acid monoester acid anhydride), (bisphenol A)bis(trimellitic acid monoester acid anhydride), and analogs thereof.
Among these, the most suitable acid dianhydrides for use in the polyimide/fluororesin laminate according to the present invention are pyromellitic dianhydride, 3,3′4,4′-benzophenonetetracarboxylic dianhydride, 3,3′4,4′-biphenyltetracarboxylic dianhydride, and p-phenylenebis(trimellitic acid monoester acid anhydride). A single one of these or a mixture of these at an arbitrary ratio may be preferably used.
Examples of suitable diamines for use in synthesis of the polyamic acid according to the present invention include 4,4′-diaminodiphenylpropane, 4,4′-diaminodiphenylmethane, 3,3′-dimethylbenzidine, 3,3′-dimethoxybenzidine, 3,3′-dichlorobenzidine, 4,41-diaminodiphenyl sulfide, 3,3′-diaminodiphenylsulfone, 4,4′-diaminodiphenylsulfone, 4,4′-diaminodiphenyl ether, 1,5-diaminonaphthalene, 4,4′-diaminodiphenyldiethylsilane, 4,4′-diaminodiphenylsilane, 4,4′-diaminodiphenylethylphosphine oxide, 4,4′-diaminodiphenyl-N-methylamine, 4,4′-diaminodiphenyl-N-phenylamine, 1,4-diaminobenzene (p-phenylenediamine), 1,3-diaminobenzene, 1,2-diaminobenz
Akahori Kiyokazu
Nishinaka Masasru
Ono Kazuhiro
Kaneka Corporation
Thibodeau Paul
Zacharia Ramsey
LandOfFree
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