JPS5910891B2 - Fully aromatic polyamide sheet-like molded product and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel wholly aromatic polyamide sheet-like molded product and a method for producing the same.

Conventionally, sheet-like molded products of wholly aromatic polyamide have been produced by a so-called dry method or wet method. The former is a method in which the solvent is removed by evaporation by contact with a heated atmosphere or a hot plate, and the latter is a method in which the solvent is extracted and removed by immersion in a coagulation bath. However, each of these methods has disadvantages in terms of economy, technology, and performance of the sheet-like molded product obtained. In other words, in the former case, there are technical difficulties in controlling the evaporation rate of the solvent, and when the heating temperature becomes high, the rapid vaporization of the solvent causes voids inside the sheet, resulting in extremely poor mechanical and electrical properties. You can only get what you get. However, if we attempt to obtain a sheet-like molded product with excellent properties by lowering the heating temperature to prevent this, the evaporation rate of the solvent will be slow, and molding will take a long time, which is an economic problem when considering industrialization. It has major drawbacks. On the other hand, in the latter case, the selection of the coagulant is a problem, and special consideration must be given to the coagulant's coagulation ability, coagulation time, coagulation temperature, etc. in order to obtain a sheet-like molded product with excellent mechanical and electrical performance. Even in this method, there are conflicting factors between performance and economy, and there are currently many issues that need to be resolved.

The present inventors conducted research to overcome the drawbacks of conventional sheet-like molded product production, and as a result, they arrived at the present invention.

That is, the present invention provides (1) a sheet-like molded product made of a wholly aromatic polyamide and having an electrical breakdown voltage of at least 150 KV/mm, and (2) a solution made of a wholly aromatic polyamide and an amide solvent, formed into a sheet shape, The sheet is dielectrically heated using high frequency waves with a frequency of 3 MC or higher, and the amount of residual solvent in the sheet (relative to the sheet, the same applies hereinafter).

) is reduced to 20% by weight or less, and then heated at 150° C. or higher under tension. 30 The wholly aromatic polyamide as used in the present invention refers to one whose main chain consists essentially of aromatic groups, which is composed of units represented by the following general formula.

In the formula, φ1 and φ2 are selected from the following group. =HN-φ1-NH-Co-φ2-Co and /35 or -HN=φ2-Co-Furthermore, the wholly aromatic polyamide referred to in the present invention contains 20 mol% of the polymerized structural units.
It also includes those in which the following consists of constitutional units other than the above-mentioned constitutional units.

The amide solvent used in the present invention refers to at least one compound selected from the following group, which is appropriately selected and used depending on the type of polymer. Furthermore, salts such as lithium chloride and calcium chloride may be added for the purpose of increasing the dissolving power for amide solvent κ and polymer K. N-y-dimethylacetamide, N-methylpyrrolidone, N-methylbiperidone, N-methylcabrolactam, N-N-N-Ntetramethylurea, N-N-N'-
N/-y-merhexamethylphosphoramide.

These amide solvents are also used as polymerization solvents for wholly aromatic polyamides in the present invention, so the polymer solution is prepared from the corresponding diamine and dicarboxylic acid halide or aminocarboxylic acid halide hydrochloride in these amide solvents. Although it can be obtained directly by low-temperature solution polymerization, the polymer obtained by low-temperature solution polymerization or interfacial polymerization is isolated and purified by pouring it into a non-solvent, and then these solvents (with a salt coexisting if necessary) are used. It can also be obtained by dissolving it in

However, if it takes a long time to redissolve the isolated polymer, it is convenient to select 20 mol % or less of other structural units to form a copolymer and shorten the dissolution time as described above. Examples of monomer components in this case include the following. Hexamethylenediamine, piperazine, 2,5-dimethylpiperazine, hydrazine hydrochloride,
4.4! -diaminodiphenylmethane, adipic acid chloride, cyclohexane-1,6-dicarboxylic acid chloride, P-P'-dichlorocarbonyldiphenyl. The concentration of the polymer in the solution in the present invention varies depending on the type of polymer used, the type of solvent, and the presence or absence of salt.
In general, it is preferably 10 to 20% by weight, and a solution viscosity of about 2000 poise is suitable. In order to obtain a sheet-like molded product by the method of the present invention, first the obtained solution is formed into a sheet-form, and then the sheet is heated at a frequency of 3MC.
Due to the above high frequency, the amount of residual solvent in the sheet is reduced to 20% by weight.
It is necessary to perform dielectric heating until the

That is, a solution consisting of a wholly aromatic polyamide and an amide solvent is applied onto a smooth surface, such as glass, in a manner that matches the polymer concentration in the solution and the desired thickness of the sheet, and this sheet-shaped molded product is formed. irradiate with high frequency.

Since wholly aromatic polyamides and amide solvents belong to so-called polar compounds (dielectrics), they absorb electrical energy in a high frequency electric field and generate heat, causing evaporation of the amide solvent. In this case, the frequency of the irradiated high frequency is at least 3
Must be MC. This is the product (
This seems to be related to the fact that the absorption power (absorbed power) increases rapidly at 3 MC or more.

Therefore, depending on the frequency and electric field strength (voltage),
Evaporation rate can be controlled. Although the preferred frequency can be appropriately selected and determined empirically depending on the solvent, the type of polymer, the intended thickness of the sheet, etc., the generally preferred frequency is 40 to 2450 MC. The present inventors discovered that by irradiating high frequency waves with a wavelength of 3 MC or more, the evaporation rate of the solvent was dramatically faster than in conventional heating plate contact or atmospheric heating, and surprisingly, the high frequency waves caused It has been found that by heating until the amount of residual solvent becomes 20% by weight, a sheet-like molded product with extremely high transparency can be easily obtained. This difference between the two heating methods is probably due to the difference in heating mechanism: heat propagation from the external surface and vibration of solvent molecules inside. In most cases, sheet-like molded products that have been subjected to high-frequency heating, or that have been subjected to high-frequency heating and then further removed of the solvent by a so-called dry method or wet method, have insufficient crystallization and orientation as they are, and do not have sufficient strength. Since the strength and elongation are insufficient and the elongation is too high, it is then necessary to heat the product to 150° C. or higher under tension in order to obtain a sheet-like molded product having the desired strength and elongation.

When heated, a sheet-like molded product usually shrinks by a few percent, so the sheet-like molded product is fixed to a frame or the like and stretched under tension, or stretched in the vertical, horizontal, or biaxial directions. The method of doing so is adopted. Heating may be carried out by hot plate contact, atmospheric heating, or high frequency heating, but especially when processing at a high temperature of 250° C. or higher, it is desirable to carry out in an inert gas such as nitrogen gas to prevent thermal deterioration. These heat treatment conditions are determined depending on the intended use of the sheet-like molded product, the type of polymer, the solvent and its remaining amount. According to the method of the present invention, sheets and films with excellent transparency, toughness, heat resistance, and electrical properties, particularly electrical insulation properties, can be economically produced. Electrical insulation performance can be evaluated by dielectric breakdown voltage, and JISC23
Measured based on l8: 150KVmw! The above items could be easily obtained by the method of the present invention.

By selecting the polymer, molding conditions, and heat treatment conditions within suitable ranges, it is possible to obtain a sheet-like molded product with a dielectric breakdown voltage of 250 K/u or more. The sheet-like molded product of the present invention having such a high dielectric breakdown voltage is particularly suitable as an insulating material for rotors and stators of large electric motors and the like which are exposed to high-voltage electric fields of several thousand volts or more, and as a high-voltage wire coating material. In general, the higher the voltage used, the more heat is generated, and sometimes the temperature of the material used can exceed 200°C, so if normal thermoplastic polymers are used in such applications, thermal decomposition or melting may occur. Because it happens,
For such purposes, polymer materials with a single ladder structure, such as so-called polyimide and polyamideimide, have been developed, but such polymers are generally expensive and the manufacturing process is complicated. Therefore, it is economically disadvantageous. In contrast, the wholly aromatic polyamide of the present invention is economically advantageous because it can be obtained from relatively inexpensive monomer raw materials. EXAMPLES The present invention will be explained in more detail by showing Examples and Comparative Examples below, but the present invention is not limited to the Examples.

Note that "parts" in the examples mean "parts by weight." Comparative example
1 m-phenylenediamine 64. purified by distillation according to the method described in Japanese Patent Publication No. 35-14399.
8 parts and 567.6 parts of anhydrous N-mer dimethylacetamide (water content 0.03%) distilled in the presence of barium oxide to 5807! Place it in a cylindrical glass container with an inner diameter of 70 mm and a height of 150 mm, and the clearance with the inner wall of the container is 311 mm under N2 air flow! Stir vigorously with a helical stirring rod.
After uniformly dissolving, the container was ice-cooled, and 121.8 parts of powdered isoptalol chloride was added so as not to exceed the internal temperature of 30°C.

Addition took approximately 2 minutes. After the addition, stirring was continued for 30 minutes at room temperature, and the reaction product gave a pale yellow viscous liquid. The reaction product contained 18% by weight of polym-phenylene isophthalamide. A portion of the reactant was taken out, a large amount of cold water was added under high speed stirring, the resulting precipitate was collected, dried, and
ηInh measured with an Ubbelod viscometer in -merged methylacetamide was 1.67. (C-0.5, 2
5. C) Add powdered calcium hydroxide to the remaining reactants22.
Two parts were added under cooling to neutralize, and then uniformly applied to a 200 ml square hard glass plate to a thickness of 300 μm using an applicator. The glass plate coated with the reactant was immediately placed in an electric oven at 80°C, and after 5 hours it was transferred to an oven adjusted to 120°C and dried for 10 hours.
Further drying at 200° C. for 8 hours yielded a transparent film with a thickness of 56 μm, which could be easily peeled off from the glass plate. The resulting film contained 9.2% by weight of N-mer dimethylacetamide. If the temperature in the oven was increased in a shorter period of time, foaming occurred inside the film and a uniform film could not be obtained.

Example 1 A glass plate coated with the reactant obtained in Comparative Example 1 in the same manner as in Comparative Example 1 was placed in a high frequency dryer with an output of 100 W, and
When irradiated with a high frequency electron beam of 40 MC for 3 minutes at 0 V and 5 minutes at 100 V, a transparent film containing 11.3% by weight of residual solvent was easily peeled off from the glass plate.

This film was thoroughly washed with water, dried, and then replaced with nitrogen.
The film obtained by simultaneously biaxially stretching 2 times in the vertical and horizontal directions using a simultaneous biaxial stretching machine (manufactured by Iwamoto Seisakusho) for 2 minutes in an oven at 5°C has a tensile strength of 18.2k9/M7 in the vertical direction.
It was a transparent film having a thickness of 7t, an elongation of 43%, and a dielectric breakdown voltage of 202K/Mm. Example 2 Polym-phenylene isophthalamide/
Terephthalamide, copolyamide (55/45) was isolated.

(ηInh=1.39) A homogeneous solution was prepared by mixing 100 parts of copolyamide, 3 parts of lithium chloride, and 385 parts of N-methylpyrrolidone in a N2 stream at room temperature for 20 minutes and at 60°C for 70 minutes. It was coated on a glass plate to a thickness of 450μ. Place the coated plate in a high frequency dryer and heat it at 72V for 4
The film was irradiated with a high frequency electron beam of 915 MC for 14 minutes at 100 V for 14 minutes to obtain a transparent film with a thickness of 90 μm and a residual solvent content of 17.7% by weight.

This was immersed in hot water at 80°C for 20 minutes, then dried.
Next, using the same equipment as in Example 1, simultaneous biaxial stretching was carried out at 220°C for 7 minutes to obtain a tensile strength of 20.
1kg/Ud, elongation 37%, breakdown voltage 191KV/
A transparent film having Mm was obtained. Examples 3 to 14 Each example shown in the table shows the film manufacturing conditions, mechanical properties, and dielectric breakdown voltage of the obtained film when a polymer other than the polymer shown in the above example is used. It is.

In all examples, the polymer was once isolated, then dissolved in a predetermined solvent and molded. [A]: Diamine [C]: Dicarboxylic acid chloride MPD: m-phenylenediamine PI: Piperazine DDPM: 4.4-diaminodiphenylmethane PPD:
p-phenylenediamine DDPE: 4,4'-diaminodiphenyl ether DDPS: 4,4'-diaminodiphenylsulfone DNAP: 2,6-diaminonaphthalene PABC: p-aminobenzoyl chloride hydrochloride IPC
l: Isophthaloyl chloride TPCl: Terephthaloyl chloride ADCl: Adipoyl chloride CHD: Cyclohexanedicarboxylic acid chloride DMAC
:N-N-dimethylacetamide NMP: N-methyl-
2-Pyrrolidone NMC: N-methyl-ε-caprolactam HMPA: Hexamethylphosphoramide TMU: Tetramethylurea (a) Measured in 96% sulfuric acid, C=0.5, 25°C (b)
Polymer concentration (%) vs. total solution (c) Salt concentration (%) vs. total solution (d) Simultaneous biaxial 2x stretching (e) Mixing ratio (volume)

Claims (1)

[Scope of Claims] 1. A sheet-like molded product made of wholly aromatic polyamide and having an electrical breakdown voltage of at least 150 KV/mm. 2 A solution consisting of a wholly aromatic polyamide and an amide solvent is formed into a sheet, and the sheet is dielectrically heated using high frequency waves with a frequency of 3 MC or higher to reduce the amount of residual solvent in the sheet (relative to the sheet) to 20% by weight or less. A method for producing a wholly aromatic polyamide sheet-like molded product, which comprises heating to 150° C. or higher under tension.