JPS5912800B2 - sheet - Google Patents

Description

Detailed Description of the Invention Industrial Field of Application 5 The present invention is a method of producing heat-resistant and insulating oil obtained by mixing pulp-like particles made of aromatic polyamide-imide with specific fibers, forming a paper, and heating the mixture under pressure. This invention relates to a sheet with excellent impregnation properties and suitable for electrical insulation.

Prior Art 10 Conventionally, paper-like sheets made of pulp-like particles and short fibers called "fifrites" have been made of soft polymers such as polyvinyl acetate and polyvinyl chloride, or hard polymers such as aliphatic polyamides and aromatic polyamides. polymeric pulp particles;
A sheet made of 15 stable natural fibers or synthetic fibers is known (see Japanese Patent Publication No. 38-13912).

However, when these sheets are used for electrical insulation, their use is considerably limited due to their poor impregnability with insulating oil. In addition, sheets for electrical insulation containing a mixture of 10 to 90% by weight of mica particles and 90 to 10% by weight of pulp-like particles of aromatic polyamide,
90% by weight of pulp-like particles of aromatic polyamide and 10~
A paper-like material suitable for electrical insulation made of 85% by weight polyester staple fibers has also been proposed (Japanese Patent Publication No. 43
20421, Japanese Unexamined Patent Publication No. 47-23602, etc.), these paper sheets are excellent in heat resistance, dielectric breakdown voltage, etc., but impregnated with insulating oil are poor.

30 Object of the Invention The object of the present invention is to provide a sheet that has excellent heat resistance, electrical insulation, and impregnability, and is extremely excellent for electrical insulation.

Structure 35 of the Invention The present invention provides 20 to 95% by weight of pulp-like particles made of aromatic polyamideimide mainly consisting of repeating units represented by the general formula (where X represents -0- or a lower alkylene group); This sheet is suitable for electrical insulation and is made by mixing short fibers of aromatic polyester and/or inorganic fibers in an amount of 80 to 5% by weight, and forming the mixture under heating and pressure.

The "aromatic polyamideimide" in the present invention has the general formula:

(Here, R is →〈》-be》-, and X is -0
-, lower alkylene group) is 85
Refers to polyamideimide containing mol% or more.

Such aromatic polyamide-imide itself is conventionally known and can be produced by known methods, but to date, no consideration has been given to making aromatic polyamide-imide into pulp-like particles. Moreover, there was no knowledge regarding the performance of paper-like sheets using the pulp-like particles.

The main feature of the present invention is that it uses pulp-like particles of the above-mentioned aromatic polyamideimide, which is completely different from conventionally widely used aromatic polyamides (for example, polymetaphenylene isophthalamide). Unless pulp particles are used, the objectives of the present invention cannot be achieved. In other words, the above-mentioned sheets using pulp-like particles of aromatic polyamide-imide have much better impregnability with insulating oil than sheets using pulp-like particles of aromatic polyamide, and this is due to the properties of the polymer. It is considered that In order to produce pulp-like particles of aromatic polyamide-imide used in the present invention, a method can be applied in which a solution of the polymer is introduced into a precipitant and precipitated as fine particles to form pulp-like particles.

The solvent used in the production of the aromatic polyamide-imide solution includes water-soluble solvents that dissolve the polymer, such as inorganic solvents such as sulfuric acid, hydrogen fluoride, fuming sulfuric acid, chlorosulfuric acid, fluorosulfuric acid, and polyphosphoric acid, or N-methyl Organic solvents such as -2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulfoxide, hexamethylphosphoramide, and tetramethylurea are suitable. Two or more of the above solvents may be used in combination. Furthermore, a solvent system can be used in which the solubility of the polymer is increased by adding an inorganic salt such as lithium chloride or calcium chloride to the above-mentioned solvent.

The polymer concentration in the solution varies depending on the degree of polymerization of the aromatic polyamideimide, but is preferably about 2 to 15% by weight.

The precipitant used to form pulp particles in the present invention is preferably a liquid or solution that is miscible with the solvent of the polymer solution but is a non-solvent for the polymer.

Such precipitants include, for example, water, glycerin, ethylene glycol, glycerin mono-water mixture, ether, etc.
Examples include aqueous precipitants containing one or more inorganic salts, and preferred inorganic salts contained in the aqueous precipitants include calcium chloride, lithium chloride, aluminum chloride, potassium thiocyanate, and sodium acetate. Among them,
Calcium chloride monoaqueous precipitants are easy to handle;
It is particularly preferred because it is also inexpensive. When producing pulp-like particles, the precipitant is stirred at high speed to remove the solvent from the introduced polymer solution and at the same time impart a shearing action or a beating action to produce fine fifurls in the precipitated particles.

The pulp-like particles obtained as described above are mixed with short fibers and made into paper. In the present invention, the short fibers to be mixed with the pulp-like particles are made of aromatic polyester short fibers and/or inorganic compounds. Examples of short fibers include the following. (1) Short fibers made of aromatic polyester.

As the aromatic polyester, (a) polyethylene-2,
6-naphthalate and/or polyethylene-2,7-naphthalate copolyester containing 85 mol% or more of ethylene-2,6-naphthalate units and/or ethylene-2,7-naphthalate units (in this case, copolymerized polyester As a copolymerization component, a copolymerized polyester using an aromatic dicarboxylic acid as an acid component is preferably used.

)(c) Copolymerization containing polyethylene-2,6-naphthalate and/or polyethylene-2,7-naphthalate and ethylene-2,6-naphthalate and/or ethylene-2,7-naphthalate units at 85 mol% or more Mixed polyester containing polyester (d) Polyethylene terephthalate (v) Copolymerized polyester containing 85 mol% or more of ethylene terephthalate units (in this case, an aromatic dicarboxylic acid was used as the acid component as a copolymerization component of the copolymerized polyester) Copolymerized polyester is preferably used.

)(f) Polyethylene terephthalate and a copolymer containing 85 mol% or more of ethylene terephthalate units I)
The above-mentioned aromatic polyester short fibers of mixed polyester resin containing ester are produced by a conventional method, and preferably have a fineness of 0.5 to 10 de1 and a fiber length of 3 to 20 mm.

(2) Short fibers made of inorganic compounds Fibers made of inorganic compounds include glass fiber, asbestos fiber, rock wool, mineral wool, fused silica fiber, glassy silica fiber, carbon fiber, Setomono fiber, kaolin fiber, and hawkite. Fibers, kyanite fibers, boron-based fibers, magnesia fibers, etc., alumina, silicon nitride, etc. hosecars.

The short fibers mentioned above can be used alone or in combination of two or more.

In order to produce a paper-like sheet from the above-mentioned bulp-like particles and short fibers, it is preferable to produce the paper by a wet method using a fourdrinier or circular mesh paper machine, as in the case of conventional paper production from natural pulp. . In the present invention, the amount of pulp-like particles needs to be 20 to 95% by weight of the sheet, and 40 to 90% by weight is preferred.

Therefore, the required amount of short fibers is 5 to 80% by weight,
10 to 60% by weight is preferred. After the sheet thus obtained is dried, it can be made into an excellent synthetic paper by heating it under pressure using means such as a hot press or a hot roll. The temperature during pressurization varies somewhat depending on the crystallinity of the pulp particles and short fibers, the degree of polymerization, etc.
Crystal C to 3200C is suitable. The pressure to be applied varies somewhat depending on the crystallinity of the pulp particles and fibers, degree of polymerization, etc. as well as the temperature at the time of pressurization, but is preferably 200 kg/d or less.

Effects of the Invention The sheet obtained by the present invention has excellent heat resistance, electrical insulation, and impregnation properties, so it can not only be effectively used as electrical insulating paper, but also has excellent mechanical properties. It is also applied to applications such as building materials and structural materials.

Example Next, Examples and Comparative Examples of the present invention will be described in detail.

In addition, the main measured values in these examples are values measured by the following measuring method. Logarithmic viscosity ηInh: Measured in N-methyl-2-pyrrolidone at a concentration of 0.59/100 ml at 30°C.

Tensile strength and tensile elongation: Measured according to the method of JISP8113 and expressed in Kg/d and %.

Dielectric breakdown voltage: Measured using AC voltage according to the method of JISC-2111. Impregnating property: A sample of 10 mm diameter was
It was floated on No. S1 insulating oil and the time required for the insulating oil to permeate the entire surface was measured.

The shorter the time, the better the impregnating property. Example 1 Comparative example [Production of pulp-like particles] After dehydration by reacting trimellitic anhydride and 4,4'-diaminodiphenylmethane at a molar ratio of 2:1, trimellitic anhydride and 4,4' - Diphenylmethane diisocyanate is added in a molar ratio of 2:3 to contain 5 g of the resulting polyamideimide (log viscosity in N-methyl-2-pyrrolidone 0.7) in 959 N-methyl-2-pyrrolidone. A solution was obtained.

The solution was introduced into a 42% by weight aqueous calcium chloride solution in a homomixer with high speed stirring. [Production of sheet] The pulp-like particles were thoroughly washed, and 1.69 was dispersed in water to make an aqueous dispersion, and this and polyethylene-2,6-naphthalate fibers with a fineness of 2 de were cut into a length of 51 mm. An aqueous dispersion in which 0.49% of the short fibers were dispersed was mixed.

A web made from the mixed dispersion was dried on a 100-mesh stainless steel wire gauze, and the physical properties of the sheet after being left at 240° C. for one week were also good. <230℃
A paper-like sheet was obtained by hot pressing.

The results are shown in column A6l of Table 1. Also, add this to 24
Physical properties after being left at 0℃ for one week. /F62 column shows. For comparison, a sheet was made in the same manner using pulp-like particles and polymetaphenylene isophthalamide fibers (fineness 2de) produced in the same manner as described above, except that polymetaphenylene isophthalamide was used instead of the polyamideimide. Manufactured.

The results are shown in Table 1 as a comparative example, and it is clear that the products using conventional wholly aromatic polyamides require a long time for impregnation and have extremely poor impregnation properties. Example 2 Aqueous dispersions of the pulp particles of Example 1 and short fibers obtained by cutting polyethylene-2,6-naphthalate fibers into 5 mm lengths were mixed to form a paper, and heated and pressed in the same manner as in Example 1. I got a sheet.

The results are shown in Table 2. As is clear from Table 2, the products according to the present invention have good tensile strength and elongation, dielectric breakdown voltage, and impregnability.

Example 3 Polyethylene-2,6- with a fineness of 2de similar to Example 1
Naphthalate staple fiber (fiber length 511) 0.29, diameter 5
An aqueous dispersion containing 1.69 μ of the above pulp-like particles was mixed into an aqueous dispersion of 0.29 μ of glass fiber having a fiber length of 51 μ.

Claims (1)

[Claims] 1 General formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (However, R is ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼, and X represents -O- or a lower alkylene group) 20 to 95% by weight of pulp-like particles made of aromatic polyamideimide mainly consisting of the repeating unit shown above and 80 to 5% by weight of short fibers and/or inorganic fibers of aromatic polyester are mixed, paper is made, and the mixture is heated and pressed. A sheet suitable for electrical insulation.