JPH02142015A - Press board - Google Patents

Abstract

PURPOSE:To improve paper manufacturing property and obtain a press board useful for an insulating material for a transformer by making at least a part of aromatic polyamide short fibers not extended fibers and low oriented fibers and specifying mixing ratio of an aromatic polyamide pulp and aromatic polyamide short fibers and the thickness and bulk density of a press board. CONSTITUTION:In a press board comprised of an aromatic polyamide pulp and aromatic polyamide short fibers, at least a part of an aromatic polyamide short is a not extended fiber and/or low oriented fiber. The mixing ratio of the aromatic polyamide pulp is 5-19wt.% and the aromatic polyamide short fiber is 81-95wt.% and the thickness and bulk density of the press board are 0.5-50mm and 0.7-1.3g/cm<3>, respectively. In the case that the aromatic polyamide <5%, the strength of damp paper in paper manufacturing process is weak, its dielectric breakdown strength is low and in the case of >20%, paper manufacturing property as well as filtration property is bad. By this, a press board useful for an insulating material for a transformer with good paper manufacturing property and high quality same as a conventional one is obtained.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an insulating presspod used in oil-filled transformers such as mineral oil, gas insulated transformers such as sulfur hexafluoride gas, and molded transformers such as epoxy resin. It is something.

[Prior Art] Generally used transformers are oil-immersed transformers in which insulating oil, which is a cooling medium, is stored in each transformer to enhance insulation strength and cooling effect. When using a transformer indoors, mineral oil is a flammable oil, so a non-flammable transformer that does not use mineral oil is required from a disaster prevention perspective, and dry type transformers or non-flammable transformers have been used, but in 1972 The use of polychlorinated biphenyls as non-combustible oil was prohibited, and since then, [
1 Dry type transformers came to be mainly used, and molded transformers also came into use. Type H dry type transformers and molded transformers are used as non-combustible transformers, but the main insulation depends on the dielectric strength of the air, so the voltage is 3.
10MVA class is considered to be the limit in terms of capacity up to 0KV class. Therefore, 66KV class or higher or IOM V
Electrically negative gases such as sulfur hexafluoride gas have come to be used as an insulating medium for nonflammable transformers of class A or higher.

Incidentally, 1" class 1ifl immersion transformers, in which expensive silicone oil is used instead of polychlorinated biphenyl as the non-flammable oil, are also used for special purposes.

Cotton m is used as an insulation spacer for oil-immersed transformers.
A press board made of high quality vegetable fibers such as N, Kraft Valve, etc. is used. On the other hand, as a class 1 to 1 transformer, a special type, -4 no (
JP-A-54-41500) or spacers made of aromatic polyamide fibrids and high temperature resistant blocks (JP-A-60-209100) are used.

In general, the manufacturing method for the board used for the insulating spacer is to form a wet paper by wet papermaking and laminate any number of sheets of wet paper whose moisture content is adjusted to 50 to 95%. After that, for example, a method of dehydrating and drying under heat and pressure using a board machine manufactured by Weidmann of Switzerland and integrating it has been adopted, as disclosed in Japanese Patent Application Laid-Open No. 5441500 and the above-mentioned Japanese Patent Application Laid-Open No. 60-209100. This is the first stage II manufacturing method described in .

However, pressboards using aromatic polymers have the drawback of poor paper-making properties due to poor drainage properties because 20 to 95 percent of aromatic polymer valves are used.

As a result of intensive research to overcome the above-mentioned drawbacks, the present inventors found that if undrawn or low-oriented short fibers are used as part of the aromatic polyamide short fibers, the bulb density can be reduced to less than 20%. It was found that the paper-making properties were significantly improved, and the present invention was completed. .

[Object of the Invention] The object of the present invention is to improve the poor paper-making properties of conventional aromatic polyamide pressboard, to ensure the same quality as conventional aromatic polyamide pressboard, and to provide a material useful as an insulating material for transformers. The purpose is to provide a breath board.

[Configuration 1 of the Invention In other words, the present invention provides a pressboard made of aromatic polyamide pulp and aromatic polyamide short fibers, in which at least a part of the aromatic polyamide known fibers is undrawn fibers and/or low oriented fibers, and Polyamide pulp is 5-1
9% by weight, 95-81% by weight of aromatic polyamide short fibers
and the thickness of 0.5-50 mm is 0.7-L3g/cd
It is a pressboard characterized by having a bulk density of .

The aromatic polyamide used in the present invention is a conventionally known (ω condensation polyamidation of a dicarboxylic acid having an aromatic ring and a diamine having an aromatic ring) a condensation polyamide formed by condensing an aminocarboxylic acid having an aromatic ring. Examples include polyamides copolymerized with (C1 (Tayama) mentioned above).

N4M polyamide pulp is known, for example, from the Japanese Patent Publication No. 35
-11851@publication and Japanese Patent Publication No. 37-5732. Particularly preferred is poly(11-phenylene isophthalamide).

The aromatic polyamide fiber is preferably poly(m-phenylene isophthalamide). Regarding the form of the short fibers, it is preferable that the single fiber fineness is 20 deniers or less and the fiber length is in the range of 3 to 20 m.

If the content of aromatic polyamide pulp is less than 5%, the strength of the wet paper during paper making will be low, and the dielectric strength will be low. 20 again
If it exceeds %, drainage properties are poor and paper-making properties are poor.

When used as an insulating material for transformers, a thickness of at least 0.5M is required, and a board of uniform quality must be obtained since pressboard with a thickness exceeding 50M will result in poor heat transfer during hot press pressing. I can't. The bulk density is 0.1-1.
It is in the range of 3g/cd.

If it is less than 0.7 g/cd, the mechanical properties such as tensile strength and compressive strength will deteriorate, and it will not be possible to support the large compressive force applied to the insulating spacer in the event of a short-circuit accident in a transformer. Also, when punching into a suberner, the laminated paper layers tend to peel off. On the other hand, if it exceeds L3g/crA, the board becomes plastic-like and cracks occur when the spacer is hit wide, making it difficult to handle.

[Effects of the Invention] The pressboard obtained by the present invention has good paper-making properties as an insulating material for transformers, and is as excellent in quality as conventional products.

[Example] Hereinafter, the method for manufacturing a press board of the present invention will be described with reference to Examples.

Each measurement value in the examples was evaluated using the following method.

(1) Tsubo appearance: Measured according to JIS P8124.

(2119; JIS C2 using a micrometer
1115,2.

(3) Density: Measured according to JIS C2111 6.1.

(4) Tensile strength and elongation: Measured according to JIS C2111-7 using a constant speed extension type tensile tester.

(5) Paper-making property: The time required for 10 ρ of water to drain was measured using a Tarapi square hand paper machine.

Examples 1-4. Comparative Example 1 Polymetaphenylene isophthalamide was produced by the interfacial polymerization method described in Japanese Patent Publication No. 47-10863.

This polymer has an intrinsic viscosity (1, V) of 1.35 when measured by dissolving it in N-methyl-2-pyrrolidone, and does not contain any inorganic salts. This polymer was dissolved in N-methyl-2-pyrrolidone to a polymer concentration of 12.5% by weight. On the other hand, water was added to N-methyl-2-pyrrolidone to prepare an aqueous solution ('fA degree 30@hang%), which was used as a precipitant. Using this polymer solution and precipitant,
A valve was manufactured by the method described in the publication using the precipitation apparatus described in the publication. Using a pulper, a high-speed disintegrator, and a disc refiner, this valve is made into a slurry with a Canadian standard freeness of 11 degrees and 0.3%.
An aqueous slurry of 〇- was prepared. On the other hand, polymetaphenylene isophthalamide drawn yarn has a single yarn fineness of 2.0 denier m fiber length 6, OM staple fibers, polymethaphenylene isophthalamide undrawn yarn has a single yarn 1M111.5 denier fiber length 6. 0M short fiber, polymetaphenylene isophthalamide low oriented yarn, single yarn drawn at a drawing ratio of 2.4 times, single yarn fineness 2.6 denier, M length 13, oIllm yri
The fibers were disintegrated and dispersed using a pulper in a suitable combination of C according to the examples at a concentration of 1%. As the mica, calcined hard mica having a maximum grain size of 200 μm was prepared.

The above valve slurry, polymethphenylene isophthalamide staple fibers, and if necessary mica dispersion slurry were combined to prepare a uniform papermaking slurry.

Next, the paper slurry is made into paper using a Tarapi-type square hand-making machine, dried, and dried paper with a filling of about 85!7/TIt is made.
It's a good deal.

The obtained dry papers were piled up and heated at 280℃ for 5 minutes at 50kg/
A press board was created by hot-pressing using a hora 1-press at a blood pressure of ci.

Table 1 shows the quality of the obtained pressboard.

As a comparative example, the values of pressboard obtained by the conventional technique are shown.

Table: The pressboard of the present invention has good paper-making properties and is useful as an insulating material for transformers.

Patent applicant Teijin Kaisha Ltd.

Claims (1)

[Claims] In the pressboard made of aromatic polyamide pulp and aromatic polyamide short fibers, at least a part of the aromatic polyamide short fibers are undrawn fibers and/or low orientation fibers, and the aromatic polyamide pulp contains 5 to 19% by weight, Aromatic polyamide short fibers are 95 to 81% by weight and 0.5% by weight
A press board characterized in that it has a thickness of ~50 mm and a bulk density of 0.7 to 1.3 g/cm^3.