JPS5947080B2 - sheet - Google Patents

Description

[Detailed description of the invention] The present invention relates to sheets.

More specifically, pulp particles made of a specific aromatic polyamide-imide are mixed with a specific proportion of short fibers having heat resistance,
The present invention relates to a sheet obtained by pressurizing and heating that has excellent heat resistance, electrical insulation, and improved mechanical properties, and in particular, a sheet suitable for electrical insulation. Conventionally, natural pulp is the most well-known pulp particle used in paper, and paper made from natural pulp is often used as electrically insulating paper.

However, paper made from natural pulp has a major drawback of lacking heat resistance, and is far from meeting the heat resistance required to reduce the size and weight of electrical equipment such as electric motors and transformers. Recently, pulp particles obtained from synthetic polymers have attracted attention as materials for electrically insulating paper because of their excellent heat resistance and electrical insulation properties. for example,
Japanese Patent Publication No. 11816 discloses that a compound selected from LiCl, LiBr, and CaCl2 is added to a solution of a certain type of aromatic polyamide in a ratio of 1 to 2 to the aromatic polyamide.
A method is described for producing an electrically insulating paper pulp by adding 0% by weight and then dispersing the solution in a precipitant. Although the paper made from the pulp-like material obtained by this method has excellent heat resistance, the dielectric breakdown voltage is still insufficient, and the mechanical properties and hygroscopicity cannot be said to be at a satisfactory level. . In addition, special public service No. 47-14761
Although the publication describes pulp-like particles made of asbestos fibers and aromatic polyamide, paper made from these pulp-like particles also does not have sufficient mechanical properties and electrical insulation properties, and therefore, As an electrically insulating paper that requires a high degree of reliability, its performance cannot necessarily be said to be sufficient.

Furthermore, Japanese Patent Publication No. 43-20421 discloses a high-temperature-resistant sheet-like structure suitable for electrical insulation consisting of an entangled mixture of granular mica and substantially unmelted aromatic polyamide fibrids. Are listed.

However, the sheet-like structure described herein also has insufficient mechanical properties and impregnability, especially as an electrical insulating material for electrical equipment that is to be made smaller and lighter. Furthermore, when producing such a sheet-like structure, the mica and fibrids separate, which makes the papermaking process extremely difficult. Furthermore, such a sheet-like structure has the disadvantage that the mica easily peels off due to friction. We have previously proposed Japanese Patent Application Laid-Open No. 48-1004 to overcome these shortcomings, i.e., to achieve the following.
No. 50, 30 to 90% by weight of mica particles and 50 to 10% by weight of a nitrogen-containing polyheterocyclic compound or its precursor. 20 to 80% by weight of pulp particles formed by covering and connecting the mica particles with a nitrogen-containing polyheterocyclic compound or a precursor thereof, and 80 to 20% by weight of short fibers are mixed, and then pressurized. We proposed a sheet that can be heated.

In JP-A-48-100450, aromatic polyamideimide is mentioned as one example of the nitrogen-containing polyheterocyclic compound.

The sheet made of aromatic polyamideimide described in JP-A No. 48-100450 has excellent heat resistance, impregnation properties, electrical insulation properties, moisture absorption resistance, etc., but its mechanical properties are still insufficient. . After that, the present inventor conducted further studies with the aim of improving the mechanical properties, within a range that does not impair the characteristics of aromatic polyamideimide. A solution of N-methyl-2-pyrrolidone of a specific aromatic polyamide-imide having more amide bonds than imide bonds, which is obtained by heat-reacting a carboxylic acid mixture in a specific proportion with a specific diisocyanate, is introduced into a precipitant. By precipitating it as fine particles, pulp particles with good paper-making properties are obtained. These pulp particles and short fibers are mixed in a specific ratio and heated under pressure to produce a sheet that has good heat resistance and impregnation properties. It not only has excellent electrical insulation properties, but also
The present invention was completed by discovering that the mechanical properties could be improved.

That is, the present invention is composed of 4,4'-bis(trimellitimido)diphenylmethane and/or 4,4'-bis(trimellitimido)diphenyl ether and isophthalic acid and/or terephthalic acid, and the composition thereof is as shown in FIG. Carboxylic acid mixture within the shaded range and 4.4'
- diphenylmethane diisocyanate and/or 4.4
20 to 95 parts by weight of pulp particles whose main resin component is aromatic polyamideimide obtained by heating reaction with '-diphenyl ether diisocyanate and 5 to 8 parts by weight of short fibers.
This sheet is made by mixing 0 parts by weight and pressurizing and heating.

In the present invention, the imidodicarboxylic acid used is 4.4
'-bis(trimellitimide) diphenylmethane and/or 4,4'-bis(trimellitimide) diphenyl ether, produced by the method described in, for example, Japanese Patent Publication No. 38-21500, Japanese Patent Publication No. 41-19302, etc. can do.

Furthermore, the diisocyanate used in the present invention is 4.4'-
diphenylmethane diisocyanate and/or 4.4
'-diphenyl ether diisocyanate, in particular 4,4'-diphenylmethane diisocyanate, is preferably used in the embodiments of the present invention.

In order to obtain the aromatic polyamide-imide used in the present invention, imidodicarboxylic acid and diisocyanate can be reacted in a molten state, but the imidodicarboxylic acid and the resulting aromatic polyamide-imide have a high melting point, Since the reaction may not proceed,
It is desirable to carry out the reaction in the presence of an inert organic polar solvent.

The reaction solvent should dissolve at least one, preferably both, of a carboxylic acid mixture consisting of imidodicarboxylic acid, isophthalic acid, and/or terephthalic acid and diisocyanate, and at the same time dissolve low polymers produced during the reaction with a sufficiently high molecular weight. The reaction solvent is required to be able to swell, preferably dissolve, at least to the extent that the activity is not lost until the aromatic polyamideimide is obtained. Examples of suitable reaction solvents include N-methyl-2-pyrrolidone, N-methyl-2-pyrrolidone, ．． N'
Examples include monodimethylacetamide, dimethylformamide, hexamethylphosphoramide, and the like. N-methyl-
2-pyrrolidone is particularly preferred. When polycondensation is carried out in the presence of an organic solvent, imidodicarboxylic acid and isophthalic acid and/or terephthalic acid are dissolved in the reaction solvent,
A preferred method is to then add diisocyanate. It is preferred that the carboxylic acid mixture and diisocyanate are reacted in an equimolar to an excess of about 10 mol % of the diisocyanate. The reaction temperature is preferably in the range of 100°C to 180°C, and carbon dioxide gas generated during the reaction must be sufficiently removed. After the completion of the reaction, the obtained polymer can be reprecipitated and separated by pouring the reaction mixture into a non-solvent, but if a uniform reaction solution is obtained at the end of the reaction, it can be used as it is or It is preferable to dilute it with a suitable solvent or add additives and use it as a stock solution for pulp production. When producing the polymer used in the present invention, the composition of the carboxylic acid mixture is
When the range is outside the shaded range in the figure, the low-weight polymer in the middle of the reaction will not dissolve in the reaction solvent, solid matter will precipitate, and the reaction will not proceed uniformly, resulting in a sufficiently high molecular weight polymer. becomes difficult.

For example, point A in Figure 1: 45 mol% imidodicarboxylic acid, 5 mol% isophthalic acid, 50 mol% terephthalic acid.
Areas where terephthalic acid exceeds 30 mol%, such as point B, i.e., imidodicarboxylic acid 10 mol%, isophthalic acid 8 mol%
Furthermore, in areas where isophthalic acid exceeds 75 mol%, such as 0 mol%, terephthalic acid 10 mol%, point C, imidodicarboxylic acid 5 mol%, isophthalic acid 70 mol%, terephthalic acid 25 mol%, etc. It is difficult to obtain a polymer with a sufficiently high molecular weight in a region of less than 10 mol%, and a sheet made from pulp particles produced using an aromatic polyamideimide obtained from a carboxylic acid mixture and a diisocyanate in this region is , the mechanical properties become unsatisfactory. Furthermore, undissolved substances are present, which often results in poor electrical insulation. Therefore, only when the composition of the carboxylic acid mixture is within the shaded range in FIG. 1 can a sheet with excellent mechanical properties be obtained. When producing pulp particles used in the present invention,
A method can be applied in which a polymer solution is introduced into a precipitant and precipitated as fine particles to form pulp particles.

The concentration of the polymer in the polymer solution varies depending on the type of polymer, the degree of polymerization of the polymer, etc., but is preferably approximately 2 to 15% by weight. Further, the solution may contain 1 to 10% by weight, preferably 3 to 9% by weight of water. Additionally, adding and mixing a minute solid inorganic substance that does not substantially react with or dissolve in the solution further improves the impregnation properties, heat resistance, flame resistance, and electrical properties of the sheet. The above is preferable. In this case, the solid inorganic substance is preferably mica, which has excellent electrical insulation and heat resistance, and furthermore, asbestos, glass flakes, quartz powder, talc, kaolin, alumina, calcium sulfate, etc. can be used. When a solid inorganic substance is mixed, the amount is 5 to 900% by weight, preferably 20 to 400% by weight of the polymer. Furthermore, two or more types of solid inorganic substances may be added and mixed at the same time. When mixing the solid inorganic substance described above into a solution, it is preferable to disperse it as uniformly as possible, and effective devices include Attritor (manufactured by Mitsui Miike Manufacturing Co., Ltd.) and T.K. Homomixer (manufactured by Tokushu Kikagaku Kogyo Co., Ltd.). It is. Next, as the precipitant used in producing the pulp particles used in the present invention, a liquid or solution that is miscible with the solvent of the polymer solution but is a non-solvent for the polymer is desirable.

When an organic solvent is used as the solvent for the polymer, the precipitant that can be used may be water alone, a water-organic solvent mixture, glycerin, a glycerin-water mixture, ethylene glycol, or a salt represented by the formula MXn. It may be an aqueous solution in which one or more of these are dissolved. The precipitant is stirred at high speed and operated to remove the solvent from the introduced solution and at the same time to produce a shearing or beating action.

In the present invention, the amount of pulp particles mixed with staple fibers should be 20-95% by weight based on the sheet.

If the amount of pulp particles is less than 20% by weight, the dielectric breakdown voltage and mechanical properties of the sheet will decrease, which is not preferable. In addition, if the amount of pulp particles is more than 95% by weight, impregnating property,
Both mechanical properties deteriorate. Paper made from pulp particles and short fibers is preferably made by a wet method using a fourdrinier or cylinder type paper making machine, similar to the conventional paper making from natural pulp. The short fibers used at this time may be any fibers that have good heat resistance, such as fibers made of aromatic polyamide (for example, Teijin Co., Ltd.'s Cornex I registered trademark).
Fibers made of aromatic polyamideimide (for example, Kermel, manufactured by Rhône-Poulenc, France) are suitable. Furthermore, short fibers made of inorganic compounds such as glass fibers can also be used. Also, two or more types of short fibers may be added and mixed at the same time. The fineness of short fibers is 0.5 to 10 deniers, especially 1.
A denier of 0 to 3.0 is preferred. Further, the length of the short fibers varies depending on the fineness of the short fibers, but is preferably 1 to 15 m and preferably 5 to 10 m and 7 n. After drying, the sheet obtained as described above can be imparted with excellent performance by heating under pressure using a hot press, a hot roll, or the like. The temperature during pressurization varies depending on the type of polymer, the type of short fibers, etc., but a temperature of 11°C to 350°C is appropriate. Like the temperature, the pressure varies depending on the type of polymer, etc., but
Desirably 0 kg/d or less. The sheet thus obtained is made up of uniformly dispersed pulp particles and short fibers,
Adhesion is sufficient, and it exhibits satisfactory mechanical properties and electrical insulation properties. The method for measuring the main measured values in the present invention will be explained below.

The present invention will be explained in detail with reference to Examples below.

Example 1 Preparation of polymer solution 4.4'-bis(trimellitimido)diphenylmenone 80 mol%, isophthalic acid 49 mol%, terephthalic acid 2
1 mole? A carboxylic acid mixture consisting of N-methyl-2-
The reaction was carried out in pyrrolidone with a 4.0 mol% excess of diisocyanate to obtain a solution containing 25% by weight of polyamideimide (logarithmic viscosity in N-methyl-2-pyrrolidone, 0.61).

(Solution A) Separately, 190 parts by weight of ion-exchanged water was added to 2350 parts by weight of N-methyl-2-pyrrolidone, and the particle size measured by the Andreasen pipette method was 400 to 100.
418 parts by weight of mica powder equivalent to 0 mesh was added, and then T. Stir with a K homomixer for 40 minutes to prepare N-methyl-
A mixed solution consisting of 2-pyrrolidone, water, and mica was obtained. (Mixed solution B) Next, 900 parts by weight of solution A were added to 2985 parts by weight of mixed solution B, and the mixture was stirred until it became homogeneous to obtain a solution to be used for precipitation. (Solution C) Preparation of precipitant 55 parts by weight of N-methyl-2-pyrrolidone and 45 parts by weight of water were mixed to prepare a precipitant.

Production of Pulp Particles A solution of CO is introduced into a conduit-stirring continuous precipitator, which consists of a combination of a stator with a battlement and a turbine blade-shaped rotor, and is equipped with a precipitant, a solution supply port, and a discharge port for the pulp particle slurry after precipitation. ．． 5kg/driver, precipitant 5kg/
The slurry of pulp particles was simultaneously supplied at a flow rate of 100 liters and taken out from the outlet.

At this time, the temperature of the precipitant was adjusted to 33°C, and the temperature of solution C was adjusted to 20°C. Also, the rotation speed of the rotor is 7100r. p. m. And so. The obtained pulp particle slurry was put into a centrifuge, and most of the precipitant was taken out as an f-liquid. Next, ion-exchanged water was supplied to perform thorough washing. Papermaking Pulp particles thus obtained 2.161 (solid content) and 7
It was cut into mm.

Aromatic polyamide fiber (manufactured by Teijin Co., Ltd., Cornex) 0.
When paper was made from an aqueous dispersion containing 54 g using a Tatsupi standard sheet machine, a sheet with good paper-making properties and good texture was obtained. This sheet was heated to 270℃ in 2001.
A paper having a thickness of 110 μm was obtained by hot pressing under the condition of <g/0IIL. The tensile strength of this paper was 5.4 kg/Udl and the elongation was 4.0%, which was good. Also, the dielectric breakdown strength is 2
It was 9Kv/Tnn. Further, this paper was immersed in silicone oil and left at 240°C for 1000 hours, but the tensile strength and elongation hardly changed and the heat resistance was good.

For comparison, an example in which the carboxylic acid mixture is different from that used in producing the pulp particles of the present invention is shown below. Comparative Example 1 The same procedure as in Example 1 was carried out except that a carboxylic acid mixture consisting of 33 mol% of 4.4'-bis(trimellitimido)diphenylmethane and 67 mol% of trimellitic anhydride was used, and a polyamide with a logarithmic viscosity of 0.7 was used. I got imide.

Then, N-methyl-2-pyrrolidone 67 was used as a precipitant.
Pulp particles were produced and paper was made in exactly the same manner as in Example 1, except that a mixed solution consisting of 33 parts by weight and 33 parts by weight of water was used.

Although the dielectric breakdown strength of the paper thus obtained was good,
The tensile strength and elongation were poor at 3.6 kg/1 and 1.3%, respectively, which were not at a satisfactory level. Examples 2 to 9 Pulp particles were obtained in the same manner as in Example 1, with various proportions of 4.4'-bis(trimellitimido)diphenylmethane, isophthalic acid, and terephthalic acid.

Paper was obtained from the pulp particles in the same manner as in Example 1. Table 1 shows the relationship between the composition of the carboxylic acid mixture and the tensile strength and elongation of the paper obtained. In either case, the dielectric breakdown strength is good at 27-30KV/Myn,
The mechanical properties are also good as shown in Table 1.

Comparative Example 2 An example in which the composition of the carboxylic acid mixture deviates from the shaded range in FIG. 1 is shown below for comparison.

A carboxylic acid mixture consisting of 55 mol% of 4.4'-bis(trimellitimido)diphenylmethane and 45 mol% of terephthalic acid and 4.4'-diphenylmethane diisocyanate were diisocyanate-treated in N-methyl-2-pyrrolidone. When the reaction was carried out in excess of 5 mol %, many fine undissolved substances were suspended.

After removing undissolved matter using a filter press, the logarithmic viscosity was measured and found to be 0.41. Pulp particles were produced in the same manner as in Example 1 except that the concentration of N-methyl-2-pyrrolidone in the precipitant was 60% by weight. There was a lot of leakage from the washed cloth, which was not desirable. Then,
Paper was obtained in the same manner as in Example 1, but the strength and elongation of this paper were 2.5 kg/1 and 0.9%, respectively, which were poor.

In addition, the dielectric breakdown strength was low at 2/Mm, probably due to undissolved substances that could not be removed by the filter press.

Comparative Example 3 Similar to Comparative Example 2, this is an example in which the composition of the carboxylic acid mixture deviates from the range shown by diagonal lines in FIG.

Polyamideimide ( A solution containing 25% by weight of viscosity (logarithmic viscosity 0.70) was obtained.

Next, pulp particles were obtained in the same manner as in Example 1 except that the concentration of N-methyl-2-pyrrolidone in the precipitant was 68%. Using these pulp particles, a paper having a thickness of 115 μm was obtained in the same manner as in Example 1. The tensile strength of this paper was 3.1 kg/Md, and the elongation was 1.4%, which were not at a satisfactory level. Example 10 4.4'-bis(trimellitimido)diphenylmethane 70 mol%, isophthalic acid 15 mol%, terephthalic acid 1
5 mol % of a carboxylic acid mixture and 4.4'-diphenylmethane diisocyanate are reacted in N-methyl-2-pyrrolidone in a 4.0 mol % excess of diisocyanate, followed by further N-methyl-2-pyrrolidone. diluted by adding polyamideimide (logarithmic viscosity 0.68) to 8.8
A solution containing % by weight was obtained.

(Solution A) On the other hand, as a precipitant, 61% by weight of N-methyl-2-pyrrolidone and 39% by weight of water were used. A mixed solution consisting of was prepared. (Coagulation value: 34) Pulp particles were then obtained in substantially the same manner as in Example 1. 1.62 g (solid content) of the thus obtained pulp particles and an aromatic polyamide fiber cut into 7 u pieces (1.5 denier Cornex fiber manufactured by Teijin)
1.08f! When paper was made from an aqueous dispersion containing the following using a Tatsupi standard sheet machine, a sheet with good paper-making properties and good texture was obtained.

This sheet at 270℃, 200kg/41177! A paper having a thickness of about 130 μm was obtained by hot pressing under the following conditions.

The performance of this paper was as follows, and all were excellent. Example 11 In Example 1, instead of 4.4'-bis(trimellitimido)diphenylmethane, 4.4'
Pulp particles were obtained in exactly the same manner as in Example 1, except that -bis(trimellitimide) diphenyl ether was used and 4,4'-diphenyl ether diisocyanate was used instead of 4,4'-diphenylmethane diisocyanate. .

When paper was made using these pulp particles in the same manner as in Example 1, the paper-making properties were good, with good water drainage from the paper-making wire mesh, and the resulting sheet had good texture. This sheet was hot pressed in the same manner as in Example 1, and the properties of the paper obtained were as follows, and all were satisfactory.

Example 12 Paper was made from an aqueous dispersion in which the pulp particles obtained in Example 1 and aromatic polyamide fibers cut to 7 mm (Teijin Co., Ltd. Cornex) were mixed in various proportions, and after drying, the mixture was heated at 270°C and 200k.
Paper was obtained by hot pressing under the conditions of g/d.

The performance of the obtained paper is shown in Table 2.

In the table, ▲B and c are sheets according to the present invention, and the tensile strength and elongation and dielectric breakdown voltage were good.

Boiling a is when the amount of pulp particles is small, and the dielectric breakdown voltage,
Tensile strength is poor.

Claims (1)

[Claims] 1 Carboxylic acid composed of 4.4'-bis(trimellitimide)diphenylmethane and/or 4.4'-bis(trimellitimide)diphenyl ether and isophthalic acid and/or terephthalic acid, the composition of which is within the shaded range in Figure 1. 20 to 95 parts by weight of pulp particles whose main resin component is aromatic polyamideimide obtained by subjecting an acid mixture to a heating reaction with 4.4'-diphenylmethane diisocyanate and/or 4.4'-diphenyl ether diisocyanate, and 5 parts by weight of short fibers. - 80 parts by weight are mixed together to make paper, and then heated under pressure.