JPS5837142B2 - Method for producing wholly aromatic polyamide film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a wholly aromatic polyamide film.

Aromatic polyamides have been actively developed for use in this field because of their high heat resistance and excellent electrical properties.

Since fully aromatic polyamides are infusible and cannot be melt-molded, they are generally formed by wet molding or dry molding from a dove obtained by dissolving them in an amide solvent as described below.

However, when a film is formed by a wet molding method or a dry molding method, there are the following disadvantages in terms of economy, technology, and performance of the obtained film.

In other words, in the former case, the problem is the selection of coagulant;
Even if special consideration is given to the coagulation power, coagulation time, coagulation temperature, etc. of the coagulant, the resulting film is still opaque and has the disadvantage that it is difficult to obtain a film with excellent mechanical and electrical performance.

In addition, the latter is a method in which the solvent is evaporated and removed by contact with a heated atmosphere or a hot plate, but the commonly used amide solvents have a high boiling point of around <200°C and have a large latent heat of vaporization, so it is difficult to dry. The drawback is that it requires a long time at a fairly high temperature.

Therefore, there are almost no transparent films made of wholly aromatic polyamides on the market at present, and only insulating papers made from Fiplid and fibers obtained by wet spinning exist as electrical insulating materials.

However, it is difficult for insulating paper to maintain its insulating function in an electric field of several thousand ports.

The present inventors have arrived at the present invention as a result of intensive studies aimed at improving the above-mentioned drawbacks in a method for producing a film made of wholly aromatic polyamide.

That is, in the present invention, a thin film is formed from a solution consisting of a wholly aromatic polyamide and an amide solvent, and when the thin film is dried with hot air to produce a film, the amount of residual solvent (relative to the thin film, hereinafter the same) is determined.

) is dried until it has a weight of 30 φ or less, and then washed with water.

The wholly aromatic polyamide as used in the present invention refers to one whose main chain consisting of units represented by the following general formula consists essentially of aromatic groups.

In the formula, φ1 and φ2 are selected from the following group.

-HN-φ, -NH-CO-φ2-co- and/or -HN-φ2-CO-? In addition, the wholly aromatic polyamide referred to in the present invention includes those in which 20 moles φ or less of the polymer constitutional units consist 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, and is appropriately selected and used depending on the type of polymer.

N,N'-dimethylacetamide, N-methyl(2)pyrrolidone, N-methylpiperidone, N-methylprolactam, N,N,N',N'-tetramethylurea, N,
N,N',N',N',N'-hexamethylphosphoramide.

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. It can be obtained directly by low temperature solution polymerization method.

In the present invention, the solution produced by the low-temperature solution polymerization method as described above can also be used as it is as a dove for film production.

In this case, C a (OH) 2 , L 1 0 H, M
g (OH) 2 , A I (OH) a, Zn (
Since hydroxides such as OH)2 can be used, CaCl, LiC
Salts such as ltAlcl3 and ZnC12 are inevitably contained in the dove.

The presence of the above-mentioned salts contained in the dove is extremely effective in improving the stability of the solution and the solubility of the polymer.

That is, it is useful for preventing dope from gelling and film from becoming opaque during film production.

However, if it contains salts, which are electrolytes, the electrical insulation properties deteriorate, so in order to obtain a film with excellent electrical insulation performance, it is necessary to remove these types by washing the film with water.

The concentration of the polymer in the molding dope used in the present invention varies depending on the type of polymer and solvent used, but is generally preferably 10 to 20% by weight.

To produce a film by the method of the present invention, first, the obtained dope is cast into a thin film, and the film surface is blown with hot air to evaporate the solvent, so that the remaining solvent amount is 30% by weight or less, preferably 25% by weight. When the weight reaches below the weight limit, drying with hot air is terminated, and the remaining solvent, salts, monomers, etc. are removed and purified by subsequent washing with water.

Hot air drying of a highly viscous liquid in the form of a thin film with hundreds of voids or more is a lapse rate drying process, so if the amount of residual solvent exceeds 30% by weight, the drying rate becomes extremely low.

Further, a semi-dry film in which the amount of residual solvent is 30% by weight or less, preferably 25% by weight or less, will no longer become opaque even when immersed in water or other liquid coagulation baths.

Therefore, at any point when the amount of residual solvent becomes 30 wt.φ or less, preferably 25 wt. It becomes possible to produce excellent films in a short time.

In order to manufacture films continuously, a thin film of molding tope is cast on the surface of a moving roller or an endless steel belt to match the thickness of the desired film, and hot air is blown onto the film surface. When the solvent is evaporated and the remaining solvent amount is 30% by weight or less, preferably 25% by weight or less, the thin film thus obtained is peeled off from the surface of the roller or endless steel belt, washed with water, and dried if necessary. By doing so, a continuous film that is transparent and has excellent electrical insulation properties can be easily obtained.

The film obtained as described above from which the solvent has been removed can be put to practical use as it is, but it may be heat-treated or hot-stretched if necessary.

For example, by heat-treating the obtained film at 150° C. or higher under tension, a film having desired strength and elongation can be produced.

Since the film undergoes many contractions upon heating, it is preferable that the heat treatment be carried out by heating the film to a tension of 1 F, or by stretching the film in the vertical direction, in the horizontal direction, or in both the vertical and horizontal directions.

Heating may be done by any method such as hot plate heating, atmospheric heating, infrared heating, or microwave heating, but in particular, when processing at a high temperature of 250°C or higher, it is performed in an inert gas such as nitrogen gas to prevent thermal deterioration. This is desirable.

These heat treatment conditions are determined depending on the use of the film, the type of polymer, etc.

According to the method of the present invention, a film with excellent transparency, toughness, heat resistance, electrical properties, especially electrical insulation properties can be produced continuously and economically.

Electrical insulation performance can be evaluated by dielectric breakdown voltage, J
150kV measured according to IS C 2518
/Xi or more can be easily obtained by the method of the present invention.

Furthermore, by selecting the polymer, molding conditions, and heat treatment conditions within suitable ranges, the dielectric breakdown voltage can be increased to 250 kV/a.
It is also possible to scale film over m.

The film obtained by the method of the present invention, which has such a high dielectric breakdown voltage, is particularly suitable as an insulating material for rotors and stators of large electric motors, etc. that are exposed to high-voltage electric fields of several thousand volts or more, and as a high-voltage wire coating material. There is.

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. Therefore, so-called polyimide/polyamide-imide-based polymer materials with a ladder structure have been developed for such purposes, but such polymers are generally expensive and the manufacturing process is difficult. This is economically disadvantageous because it also becomes complicated.

In contrast, the wholly aromatic polyamide film obtained by the method of the present invention is economically advantageous because it can be obtained from relatively inexpensive monomers and 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, distilled and purified according to the method described in Japanese Patent Publication No. 35-14399,
8 parts of anhydrous N,d-dimethylacetamide distilled in the presence of barium oxide 5 6 7. 6 parts and 580rI
Place the powder in a cylindrical glass container with an inner diameter of 70 mmφ and a height of 150 mm in a N2 gas flow with a helical stirring rod having a clearance of 3 mm from the inner wall of the container to uniformly dissolve the powder. Isophthaloyl chloride 121
．． 8 parts were added while being careful not to allow the internal temperature to exceed 30°C.

Addition took approximately 2 minutes.

After adding isophthaloyl chloride, stirring was continued at room temperature for 30 minutes, and the reaction product became a pale yellow viscous liquid.

The reaction product thus obtained contained 18 weight portions of polym-phenylene isophthalamide.

A portion of the reactant taken out was dropped into a mixer containing a large amount of cold water while stirring vigorously, and the resulting precipitate was dried.
25°C in N,N'-dimethylacetamide, concentration 0.5
, i/7100mA'C" ηinh was 154, which was determined from the value measured using an Uherode viscometer.

22.2 parts of powdered calcium hydroxide was added to the remaining reaction product under cooling to neutralize it to obtain a film-forming dope.

This dope was uniformly coated to a thickness of 300 μm on a 200 nm square hard glass plate using an ablator.

After putting the glass plate coated with the dope in a hot air circulation dryer at 100°C and drying it for 20 minutes, a part of the film was cut off to measure the amount of remaining solvent, and most of the remaining film was put in water at room temperature to determine the remaining solvent and content. Salts, monomers, etc. were removed by washing with water.

After washing with water for 60 minutes, the film became completely white and opaque.

After washing the film, dry it and fix it on the frame at 300℃.
Although it was heat treated for 2 minutes, the appearance did not change.

Note that the amount of residual solvent before washing with water was 37% by weight.

The strength of the obtained film was 7Kg/tnri, and the elongation was 8.
In Section 7, the dielectric breakdown voltage was 30 kV/ram.

Example 1 The same dove used in Comparative Example 1 was applied to a glass plate in exactly the same manner as in Comparative Example 1, and after drying for 15 minutes in a hot air circulation dryer at 130°C, Comparative Example l
In the same manner as above, the amount of residual solvent was measured and scouring was performed by washing with water.

The amount of residual solvent was 24.2 weight cakes.

The resulting film had very high transparency and an excellent appearance.

The film thus obtained was further heated at 300°C for 2 minutes.
When heat treated in a N2 stream, the strength was 1 5.3k.
y/rat, elongation 79.3 yen, dielectric breakdown voltage 196k■
/B film was obtained.

゛Examples 2 to 6 and Comparative Examples 2 to 6 Each example shown in Table 1 shows the film manufacturing conditions and the mechanical performance and dielectric breakdown voltage of the obtained film.

In each case, after drying with hot air, washing and scouring were performed with warm water of 30 to 50°C.

[A]: Diamine [C]. Dicarboxylic acid chloride MPD: m-phenylenediamine DDPM: 4,4-aminodiphenylmethane PA
BC: P-aminobenzoyl chloride hydrochloride IPC: Isophthaloyl chloride TPC: Terephthaloyl chloride DMAC: N,N'-dimethylacetamide NMP:
N-Methyl-2-pyrrolidone TMU: Tetramethylurea (a) C=0.5 in 96% sulfuric acid, measured at 25°C (b)
Polymer concentration (weight) vs. total solution Example 7 The dope used in Comparative Example 1 was used when the slit width of the T die was 0.
．． 12mm and length 500j! It was discharged from a slit of m at a discharge rate of 3 Qcc/min, and was uniformly cast to a thickness of 125 μ on an endless steel belt running at 50 CIIL/min. Sprayed and dried for 10 minutes.

At the end of drying, the film was peeled off from the endless steel belt, a portion of it was sampled, and the amount of remaining solvent was measured, and it was found to be 12.3% by weight.

Immediately introduce most of the other parts into the washing tank and rinse with 40'C hot water for 3 minutes.
The film was washed for 0 minutes, then dried, and then subjected to continuous heat treatment at a constant length in a heat treatment machine at 320°C to obtain a 26 μm thick film with excellent transparency.

The obtained film had a strength of 15-7k9/mm, an elongation of 50%, and a dielectric breakdown voltage of 245 kV/xi.

Example 8 A film treated under the same conditions as Example 7 until washing and drying was subjected to hot stretching treatment at 320° C. by 1.2 times in the vertical, horizontal, and biaxial directions at the same time to obtain a film with an elongation of 18μ. .

The strength in the vertical direction is 22.3k! 9/yxti, elongation is 4
3%, horizontal strength 21.0~/d, elongation 51%
The dielectric breakdown voltage was 260 kV/d, and the film was extremely transparent.

Example 9 The dope used in Example 5 had a diameter loocIrL and a length of 5.
Thickness of 30 m with Keysa on the surface of the casting drum.
0μ, and hot air at 145℃ was applied to the cast film surface in parallel flow for 2 hours.
The film was sprayed for 0 minutes, dried, and then continuously peeled off.

The amount of residual solvent in this film was 18.8 weight cakes.

Subsequently, it was washed in warm water at 50° C. for 30 minutes, then dried and heat-treated at 300° C. for 3 minutes.

The obtained film had a strength of 20.3 kg/xi, an elongation of 68 m, a dielectric breakdown voltage of 193 k/Rm, and a film with good transparency and a thickness of 55 μm.

Claims (1)

[Claims] 1 A thin film is formed from a solution consisting of a wholly aromatic polyamide and an amide solvent, and the thin film is dried with hot air to produce a film. A method for producing a wholly aromatic polyamide film, which is characterized by washing with water.