JPS6054339B2 - Method for producing aromatic copolyamide film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an aromatic copolyamide film having excellent performance, particularly excellent electrical insulation properties.

Paper obtained from aromatic polyamide has excellent heat resistance, mechanical performance, and electrical properties, as expected due to the rigidity of its molecular structure and intermolecular forces, and is often used in the rotation of large electric motors. It is used as an insulating material for children and stators, as well as a high-voltage wire covering material, but if it is made into a film with higher density, it is expected that an even higher performance electrical insulating material can be obtained.

By the way, as a method for producing an aromatic homopolyamide film, a dry or wet method is known in which an amide solvent dope is added with a salt such as calcium chloride or lithium chloride in order to increase the solubility of the polymer and the stability of the dope.

In the former method, the dope is formed into a film and brought into contact with a heated atmosphere or a heating plate to evaporate and remove the solvent; in the latter, the dope is formed into a film and immersed in a coagulation bath to extract and remove the solvent;
This is a way to make them leave. However, these methods have drawbacks in terms of the electrical insulation performance of the resulting film, as well as economic and technical disadvantages.

That is, in the former case, salts such as calcium chloride contained in the dope cannot be removed by heating alone (2), but are removed in the washing process with water, so electrical insulation is caused by the cavities formed in the film during desalination. It becomes inferior in quality. Furthermore, it is known that salts such as calcium chloride and amide solvents form complexes, which results in poor evaporation efficiency of the solvent and requires a long time to form a film. It is also difficult to remove. Furthermore, when considering industrial production, it is essential to recover the solvent from the washing wastewater. On the other hand, in the latter case, there is a problem in the selection of the coagulant.3 To obtain a film with excellent electrical and mechanical performance, special consideration must be given to the coagulant's coagulation ability, coagulation time, coagulation temperature, etc. be.

Furthermore, in solvent recovery, there is a problem of complex formation between salts such as calcium chloride and amide solvents, which requires special consideration. The present inventors have arrived at the present invention as a result of intensive research aimed at improving these drawbacks in the method for producing aromatic polyamide films.

That is, in the present invention, 90 to 20 mol% of all amide structural units are composed of poly m-phenylene isophthalamide, and the remaining 10 to 80 mol% is composed of substantially equimolar dicarboxylic acid and diamine units shown below. Intrinsic viscosity of 0.8 or more (concentration 0.5y/100ml in 96% sulfuric acid solvent)
5 (measured by C) and an amide solvent, and the inorganic salt content (relative to the polymer) is 0.5 (measured by C). A thin film is formed from a dope having a dope of less than 2% by weight, the thin film is heated to reduce the amount of residual solvent in the thin film (relative to the thin film, the same applies hereinafter) to 2% by weight or less, and then heat treatment is performed at a temperature of 150°C or higher. This is a method for producing an aromatic copolyamide film, which is characterized by carrying out a heat treatment at a temperature of 15 (degrees) or more after washing with water or washing with water.

(Dicarboxylic acid unit) However, [X: halogen, methyl group n: 0, 1 or 2] However, [Y: -CH2-, -C(CH3)2-,
-CO-, -SO2-, -S
O1 m: 0 or 1] (Diamine unit) However, [Z: halogen, methyl group 1: 0, 1 or 2] However, [W: -CF[2, -C(CH3)2-,
-CO-,-SO,-,-S
O- As a preferred example of the polymer used in the present invention, polym
- Polymers consisting of 90 to 20 mol% of phenylene isophthalamide units, and the remaining 10 to 80 mol% of poly p-phenylene isophthalamide and poly m-phenylene terephthalamide units, etc. can.

The polymer used in the present invention can be obtained by any known method.

For example, a method may be mentioned in which the corresponding diamine and dicarboxylic acid dichloride are subjected to low-temperature solution polymerization or interfacial polymerization. As a polymerization solvent, dimethylacetamide, N
- Single or mixed solvents such as amide solvents such as methylpyrrolidone, tetramethylurea and hexamethylphosphoramide, and halogenated hydrocarbons such as methylene chloride and chloroform can be used. At this time, an inorganic salt such as lithium chloride or calcium chloride may be added to the polymerization solvent. Further, the aromatic copolyamide used in the present invention may be either a random, regular or programmed copolyamide.

The polymer used in the present invention has an intrinsic viscosity of 0.8 or more, preferably 1 or more.

If the intrinsic viscosity is less than 0.8, the resulting film will have poor mechanical properties. Here, the intrinsic viscosity is 9 at 25℃.
It was determined from the value measured at a polymer concentration of 0.5y/100ml in 6% sulfuric acid. Dopes suitable for producing films by the method of the invention include dimethylacetamide, N-methylpyrrolidone, N-methylcaprolactam, tetramethylurea, hexamethylphosphoramide. It can be obtained by dissolving the above polymer in an amide solvent alone or in a mixed solvent. In this case, inorganic salts such as chlorides or bromides of calcium, lithium, strontium, magnesium, etc., may affect the solubility of the polymer used in the present invention. Since the stability of the dope and dope is good, there is no need to add it intentionally, but it is necessary to add 0.0% to the polymer. Addition is allowed if the amount is not more than 1% by weight, preferably not more than 0.1% by weight. If the inorganic salt is added in an amount exceeding 0.3% by weight, the resulting film will have poor electrical insulation properties and mechanical properties. Furthermore, as mentioned above, it is known that these salts and amide solvents form chains, and when amide solvents are removed by heating from a thin film formed from dope, the evaporation efficiency is poor and it takes a long time. However, it is difficult to completely remove the solvent. In addition, water washing takes a long time, resulting in poor film productivity. Furthermore, considering the above, it is obvious that there are disadvantages in solvent recovery as well.
When polymerization is carried out by adding the above-mentioned inorganic salt etc. to an amide solvent, the amount of salt added is 0.00% relative to the resulting polymer. If the amount is less than %, the polymerized dope can be used as it is or after being subjected to treatments such as concentration or dilution, as a dope for film forming.

However, if the amount of salt added exceeds 0.3% by weight, either isolate the polymer and prepare a new dope, or use other methods such as adding another salt to make the inorganic salt insoluble in the system. Therefore, it is necessary to remove it by Fuchibetsu etc. Furthermore, the content of inorganic salts generated when the polymerization dope is neutralized is 0.
Similar treatment is required when the amount exceeds 3% by weight. The concentration of the polymer in the dope used in the present invention varies depending on the degree of polymerization, composition, and type of solvent;
It is usually used at a concentration of 10 to 4%, preferably 15 to 2%.

If the polymer concentration is outside this range, moldability may be poor, the physical properties of the resulting molded product may be poor, and the dope viscosity may become too high or too low, making it difficult to mold, which is undesirable. To produce a film from the dope prepared in this way, first the dope is applied onto a smooth plate such as gas or a belt-like moving plate, or the dope is applied downward from the slit in a heated atmosphere such as nitrogen. After forming a thin film by an extrusion method or the like, the thin film is heated to reduce the amount of residual solvent in the film to 2 mass% or less.

Although the time required for evaporation of the solvent naturally varies depending on the type and concentration of the solvent removed, the heating temperature is required to be 80° C. or higher. However, if the temperature is above the boiling point of the solvent, the evaporation rate of the solvent becomes too fast, which tends to cause voids in the membrane, which is not preferable. If the amount of residual solvent in the thin film exceeds 2%,
The effect of subsequent heat treatment is poor.

Furthermore, when a thin film with a residual solvent amount exceeding 2% by volume is washed with water, the resulting film exhibits the generation of voids and whitening phenomenon, and its electrical insulation properties and mechanical performance are poor. Therefore, before the thin film formed from the dope is subjected to heat treatment or water washing treatment, it is necessary to reduce the residual solvent amount to 2% or less by heating. Even when the amount of residual solvent in the thin film before heat treatment is less than 2% by weight, the mechanical performance of the obtained film improves slightly as the amount of residual solvent decreases, but the time required for evaporation is longer and the productivity is inferior. Become. Therefore, unless particularly excellent mechanical performance is required, it is sufficient to keep the amount of residual solvent at 20% by weight or less. In addition, the amount of residual solvent is 2%
It is also effective to improve productivity by switching from evaporation removal of the solvent by heating to removal by washing with water, which has a high extraction rate of the solvent, at any point when the following occurs. The amount of residual solvent is 2
A strong film can be obtained by heat-treating the thin film whose saliva content is below %, or by heat-treating it after washing with water.

The heat treatment conditions should be determined depending on the type of polymer, the solvent and its residual amount, or the desired performance of the film, but the temperature must be 150°C or higher. Further, the heat treatment may be performed in one stage, but there is no problem even if the heat treatment is performed in multiple stages. As described above, according to the present invention, it is possible to economically produce a film having excellent electrical insulation and mechanical performance.

EXAMPLES Hereinafter, the present invention will be explained with reference to Examples, but the Examples are not intended to limit the scope of the present invention.

Comparative Example 1 m-Phenyldiamine obtained by interfacial polymerization with isophthalic acid chloride in advance
Phenylene isophthalamide (ηInhl.67) 1% by weight, calcium chloride 3% by weight, and dimethylacetamide 7%
A dope with a more uniform slag weight was prepared.

In this case, a uniform dope could not be obtained unless calcium chloride was added. Apply the above dope with an applicator for 20 minutes.
It was applied uniformly to a thickness of 300 μm on a hard glass plate with a normal angle of 0.0 μm.

Immediately, the glass plate was placed in an electric heating oven at 80 μC, and after one hour, the film was peeled off from the glass plate, and the amount of remaining solvent was measured. It was found that the weight was %. Then, the film was washed with running water for H hours, so that the amount of residual solvent in the film was 0.1% by weight, and the amount of residual calcium chloride was 0.
．． The amount was 0.05% by weight. After drying the film after washing with running water, it was subjected to heat treatment for stretching 1.4 times simultaneously in the vertical and horizontal directions using a simultaneous biaxial stretching machine for 2 minutes in an open air atmosphere at 235° C. under nitrogen atmosphere. The obtained film had a dielectric breakdown voltage of 183 kv/T.
Of (AST ■ sword 49-? method), tensile strength 17.1k
9/Tdl elongation of 40%.

Example 1 40 mol% m-phenylenediamine, 10 mol% p-phenylenediamine and 50 mol% isophthaloyl chloride
Poly m-phenylene/p-phenylene isophthalamide random copolymer with ηIrlFl of 1.84 (
80 mol% of poly m-phenylene isophthalamide units,
It consists of 20 mol% of poly p-phenylene isophthalamide units.

) was obtained. A uniform dope was obtained from 1% by weight of the above copolyamide and 81% by weight of dimethylacetamide, and was applied uniformly to a thickness of 300 μm on a glass plate in the same manner as in Comparative Example 1.

Immediately, the glass plate was placed in an oven at 80°C, and after 8 hours, the film was peeled off from the glass plate, and the amount of residual solvent was measured and found to be 17.5% by weight. Then, the film was subjected to a heat treatment for stretching 1.3 times in the vertical and horizontal directions at the same time for 2 minutes in a simultaneous biaxial stretching machine in an open air atmosphere at 235° C. under nitrogen atmosphere. The obtained film was colorless and transparent and had a dielectric breakdown voltage of 215 kV/W.
! It showed Ftl tensile strength of 18.8k9/Rdl elongation of 38%.

Example 2 m-phenylenediamine 50 mol%, isophthalic acid chloride 40 mol%, terephthalic acid chloride 10 mol%
Low temperature solution polymerization was carried out using N-methylpyrrolidone as a solvent.

After neutralizing the obtained polymerized dope by blowing ammonia gas into it, ammonium chloride produced as a by-product was separated. The resulting uniform dope contained a poly m-phenylene isophthalamide/terephthalamide polymer (consisting of 80 mol% poly m-phenylene isophthalamide units and 20 mol% poly m-phenylene isophthalamide units). ) and 0.05% by weight of ammonium chloride (0.29% based on the polymer). Further, the ηInh of the polymer was 1.94. The above dope was applied to a glass plate to a thickness of 450μ, and the glass plate was immediately placed in an open chamber at 95°C, and the film was peeled off after 1C, and the residual solvent rate was 17%. .

This was immersed in hot water at 80°C for 20 minutes and then dried.
Then, heat treatment was performed at 2500C for simultaneous 1.3x stretching in the vertical and horizontal directions using a simultaneous biaxial stretching machine, resulting in a dielectric breakdown voltage of 198.
kv/Twtl tensile strength 18.3k9/d1 elongation 35%
A colorless and transparent film was obtained. Comparative Example 2 A dope obtained in the same manner as in Example 2 was applied to a glass plate to a thickness of 450 μm, and the glass plate was immediately placed in an open chamber at 95° C., and the film was peeled off after 6 hours.

The amount of residual solvent in the film was 26.3%. This film was heat-treated to be simultaneously stretched 1.3 times in the vertical and horizontal directions using a simultaneous biaxial stretching machine at a temperature of 250°C. Film performance after heat treatment is dielectric breakdown voltage 138kv/film, tensile strength 12.5
The k9/Wltl elongation was as low as 42%. Example 3 A copolyamide of ηIrlFll.32 was obtained by low-temperature solution polymerization in hexamethylphosphoramide from 45 mol% of m-phenylenediamine, 5 mol% of 4,4''-diaminodiphenylmethane, and 50 mol% of isophthalic acid chloride. I got it.

The above copolyamide was once isolated and then dissolved in tetramethylurea to a polymer concentration of 2% by weight to prepare a uniform dope.

This dope was applied to a glass plate to a thickness of 350 μm, and the glass plate was immediately placed in an open room at 130°C and heated for 5 hours, and then 1. When the film was subjected to 3-fold stretching heat treatment, a colorless and transparent film having a dielectric breakdown voltage of 205 kV/R and a tensile strength of 18.1 K9/i1 and elongation % was obtained. Comparative Example 3 A dope prepared in the same manner as in Example 3 was applied to a glass plate to a thickness of 350 μm, and the glass plate was immediately placed in an open chamber at 130°C and heated for 5 hours, followed by simultaneous biaxial stretching at 120°C in an open chamber. However, it was possible to stretch the film in both the vertical and horizontal directions, and the film was then heat-treated for 3 minutes.

Claims (1)

[Claims] 1. 90 to 20 mol% of all amide structural units are poly-m-
consisting of phenylene isophthalamide, the remaining 10 to 80
Intrinsic viscosity of 0.8 or more (concentration 0.5 g/100 ml in 96% sulfuric acid solvent, measured at 25°C) composed of substantially equimolar mole % of the following dicarboxylic acid and diamine units
A thin film is formed from a dope consisting of a polyamide and an amide solvent with an inorganic salt content (based on the polymer) of 0.3% by weight or less, and the thin film is heated to determine the amount of residual solvent in the thin film (based on the polymer). (thin film) to 20% by weight or less, and then heated to 150°C.
1. A method for producing an aromatic copolyamide film, which comprises heat-treating at a temperature of 150° C. or higher, or washing with water and then heat-treating at a temperature of 150° C. or higher. (Dicarboxylic acid unit) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ However, [x: halogen, methyl group n: 0, 1 or 2] ▲There are mathematical formulas, chemical formulas, tables, etc.▼ However, [Y: -CH_2- , -C(CH_3)_2-
-CO-, -SO_2-, -SO-m: 0 or 1] diamine unit) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ However, [z: halogen, methyl group, 1: 0, 1 or 2] ▲ Numerical formula , chemical formulas, tables, etc. ▼ However, [w: CH_2-, -C(CH_3)_2-,
-CO-, -SO_2-, -SO- k: 0 or 1]