JPS645071B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an insulating paint that uses a solvent with excellent solubility and low toxicity, and has good coating workability and cured film properties at high concentrations. Specifically, the present invention relates to an insulating coating material made by dissolving a polyesterimide resin and a curing agent in a specific solvent, and which is particularly useful as a wire enamel. Conventionally, polyester resin wire enamel has been used as a general-purpose wire enamel because of its well-balanced electrical, thermal, and mechanical properties. Recently, there has been a demand for smaller size and higher performance of electrical equipment, and with this, the required performance for wire enamel has also increased, and the demand for polyesterimide resin wire enamel with high heat resistance is increasing. On the other hand, from the viewpoint of resource conservation, various studies are being conducted to increase the concentration of insulating paints and to reduce the amount of solvents released into the atmosphere and burned. However, in the case of polyesterimide resin wire enamel, phenols such as phenol, cresol, and xylenol are used as solvents due to problems with the solubility of the resin, and from the viewpoint of painting workability and film properties, the viscosity of the enamel is usually 30%. 70~ as measured in °C
Since there is a restriction of 80 poise or less, the resin content in wire enamel is currently around 40% at most to satisfy that condition. A common method for increasing the resin content in wire enamel is to reduce the molecular weight of the resin. However, the properties of the wire enamel made in this way are not only considerably inferior to conventional products in terms of heat resistance and mechanical strength, but also the storage stability of wire enamel is known to be problematic. There is. In addition, a method of reducing or eliminating the solvent content in wire enamel and heating it in advance before use has been carried out on a trial basis to reduce the viscosity to an appropriate level for working.
There are many problems such as heating equipment, enamel supply method, thermal stability, painting workability, curing characteristics, etc., and it has not been fully put into practical use. Recently, wire enamels in which polyesterimide resins are dissolved in solvents other than phenols have been proposed. Phenols are highly irritating, and if they come into contact with the skin, there is a risk of inflammation, so extreme care must be taken when handling them. Attempts to dissolve in solvents other than phenols were made with an emphasis on safety as well as resource saving. For example, glycol ethers and dibasic acid lower alkyl esters are typical solvents, and wire enamels made with these solvents have a resin concentration of 50 to 60%.
%, which also meets the resource-saving objectives mentioned above. However, wire enamels made with such solvents are considerably inferior to conventional products in terms of paint workability and cured film properties, have difficulty in diluting the enamel with solvents, and furthermore have problems with the cured film properties over time. It has not been put into practical use due to many problems such as large changes. Under these circumstances, there has been a long-awaited development of a polyesterimide resin wire enamel with higher concentration and lower toxicity without impairing the painting workability and cured film properties of conventional products. As a result of intensive research in view of the current situation, the present inventors found that acetophenones are aromatic, have low toxicity, have excellent dissolving power for polyesterimide resin, can be highly concentrated, and are superior to conventional products. The present invention was completed based on the discovery that the coating workability and properties of the cured film were not impaired. The insulating paint of the present invention combines an aliphatic dihydric alcohol, a trihydric or higher polyhydric alcohol, an aromatic tribasic acid alone or both the tribasic acid and an aromatic dibasic acid, and an aromatic polyamine with a hydroxyl group. The equivalent ratio of carboxyl groups is 1.2/1 to 4.0/1, and the hydroxyl groups of the trivalent or higher polyhydric alcohol are 20 to 80 equivalent% of the total hydroxyl groups, and the carboxyl groups that participate in imide group formation are 20 to 80 equivalent% of the total carboxyl groups. 5~
The polyesterimide resin () and curing agent () obtained by reacting with a component ratio of 50 equivalent % are expressed by the general formula

[Formula] (In the formula, R represents a hydrogen atom, an alkyl group having 1 to 2 carbon atoms, or an alkoxy group) This is a characteristic feature. In addition, the imide equivalent % in the present invention is based on the British patent no.
It is based on the definition described in the specification of No. 1082181. Acetophenones in the present invention are compounds represented by the above general formula, such as acetophenone,
Methylacetophenone, ethyl acetophenone,
Examples include methoxyacetophenone, which can be used alone or in combination. Among these, acetophenone is the most preferred. In addition to acetophenone with a purity of 98% or more, crude acetophenone, which is a by-product during phenol synthesis, can also be used in sufficient quantities. The insulating coating of the present invention using acetophenones as a solvent, for example, polyesterimide resin wire enamel, uses phenols,
For example, the resin concentration can be increased by approximately 10% compared to conventional products that use cresol as a solvent. Furthermore, acetophenones can be used in combination with other solvents within a range that does not impair the effects of the present invention. Examples of other solvents include xylene, naphtha, xylenol, N-methylpyrrolidone, dimethylacetamide, dimethylformamide, cresol,
Examples include phenol, commercially available cresylic acid, γ-butyllactone, and glycol diether. Polyesterimide resin () in the present invention
is an aliphatic dihydric alcohol, a trihydric or higher polyhydric alcohol, an aromatic tribasic acid alone or both the tribasic acid and an aromatic dibasic acid, and an aromatic polyamine,
It can be prepared according to conventionally known procedures using the specified proportions as described above. The equivalent ratio of hydroxyl and carboxyl groups is
The reason for limiting the range to 1.2/1 to 4.0/1 is that if the number of hydroxyl groups is less than 1.2/1, the reaction rate will be extremely slow, making it impractical, and the molecular weight of the resin will become too large, making it difficult to dissolve in solvents. This is because if the number of hydroxyl groups is more than 4.0/1, the molecular weight of the resin becomes too small, the cured film becomes brittle, and sufficient properties cannot be obtained. The reason why we limited the hydroxyl groups of trihydric or higher polyhydric alcohols to 20 to 80 equivalent% of the total hydroxyl groups is that if it is less than 20 equivalent%, the crosslinking density of the resin is too small, resulting in slow curing and insufficient film strength. This is because if it exceeds 80 equivalent percent, it becomes too hard and has difficulty in flexibility. Considering the balance of resin reaction and properties of the cured film, the preferred equivalent ratio of hydroxyl groups to carboxyl groups is 1.5/
The ratio is 1 to 3.0/1, and the preferred ratio of the hydroxyl groups of the trivalent or higher polyhydric alcohol is 30 to 60 equivalent % of the total hydroxyl groups. Imide group formation in the polyesterimide resin () is achieved by reaction between an aromatic tribasic acid or its derivative and an aromatic polyamine. It is also effective to supply and react in the form of polyimide polycarboxylic acid. The carboxyl groups participating in the formation of imide groups account for 5 to 50 equivalent %, preferably 20 to 50 equivalent % of the total carboxyl groups. If it is less than 5 equivalent %, the amount of imide groups formed is too small and no heat resistance effect can be expected. For imide group formation, it is preferable to react at a ratio of 1 equivalent of the amino group of the aromatic polyamine to 1 mole of the aromatic tribasic acid or its derivative, but an excess of about 10% of the amino group is within the permissible range. . Examples of aliphatic dihydric alcohols used in preparing the polyesterimide resin () of the present invention include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, 1,4-
Examples include butanediol, 1,6-hexanediol, neopentyl glycol, N,N'-bishydroxyalkyl-5,5'-dimethylhydantoin, and the like. Among these, ethylene glycol is the most preferred. Examples of trivalent or higher polyhydric alcohols include trimethylolethane, trimethylolpropane, glycerin, pentaerythritate, diglycerin, tris(2-hydroxyethyl)isocyanurate, tris(2-hydroxypropyl)isocyanurate, 1, Examples include 3,5-trihydroxyethyl-2,4,6-hexahydrotriazine. From the viewpoint of heat resistance, tris (2-hydroxyethyl) isocyanurate)
is most preferred. Examples of aromatic tribasic acids include trimellitic acid, hemimellitic acid, benzophenone-3,4,
In addition to 4'-tricarboxylic acids, there may also be mentioned derivatives of these acids such as anhydrides, lower alkyl esters, lower glycol esters, etc., which act as tribasic acids during the preparation of polyesterimide resins. Among these, trimellitic anhydride is the most preferred. Examples of aromatic dibasic acids include terephthalic acid, isophthalic acid, benzophenone-4,4'-
Examples include not only dicarboxylic acids and 4,4'-biscarboxyethophenylpropane, but also lower alkyl esters and lower glycol esters of these acids, which are prepared as dibasic acids during the preparation of polyesterimide resin ().
Among these, terephthalic acid or its methyl ester is most preferred. Examples of aromatic polyamines include phenylene diamine, methylene dianiline, oxydianiline, diphenylsulfone-4,4'-diamine, diphenylpropane-4,4-diamine, diphenylene-3,3'-dimethyl-4, Examples include 4'-diamine, polymethylene polyaniline, and triaminobenzene. Among these, methylene dianiline is the most preferred. The curing agent (2) in the present invention speeds up curing during coating and baking of wire enamel and improves the physical and chemical properties of the coating film. There are no particular restrictions on such a hardening agent (), and various hardening agents can be used. For example, tetrabutyl titanate, tetraisopropyl titanate, tetraphenyl titanate, tetracresyl titanate,
Organotitanium compounds such as triethanolamine titanate, diethanolamine titanate, diacetylacetone titanate, and the like can be used. The organic titanium compound can be used in combination with formaldehyde condensates of phenols, blocked polyisocyanate compounds, or formaldehyde condensates of melamine, guanamine, hydantoin, and the like. Also, zinc naphthenate,
Metal salts of organic acids such as zinc octenoate, tin octenoate, cyclohexylsulfamic acid, P
- Combination use with organic acids such as toluenesulfonic acid is also possible. The insulating paint of the present invention is obtained by dissolving a polyesterimide resin () and a curing agent () in an acetophenone represented by the above general formula or a mixed solvent of the acetophenone and another solvent. There are no particular restrictions on the dissolution procedure; for example, acetophenones or a mixed solvent is added to and dissolved in the polyesterimide resin () in a hot molten state that has completed the reaction, and after cooling, it is mixed with a curing agent (); and curing agent () are added to and dissolved in acetophenones or a mixed solvent, or the polyesterimide resin () and curing agent () are separately dissolved in acetophenones or a mixed solvent, and the two are mixed later. It can be used as an insulating paint. For dissolution,
It can also be heated to a temperature of 50-250°C. or,
It is also possible to incorporate colorants and pigments. The insulating paint thus obtained can have a much higher resin content than conventional insulating paints using phenols as solvents. In addition to being fragrant and having low toxicity, it also has excellent coating workability and cured film properties, making it particularly useful as a wire enamel. It is also useful as an insulating coating for metal plates and other base materials. EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but these are merely examples, and the present invention is not limited to these Examples. In the following, all parts and % mean parts by weight and % by weight unless otherwise specified. moreover,
The following abbreviations are used below. EG = ethylene glycol DEG = diethylene glycol THEIC = tris(2-hydroxyethyl) isocyanurate GL = glycerin TPA = terephthalic acid MDA = methylene dianiline TMA = trimellitic anhydride TPT = tetraisopropyl titanate TBT = tetrabutyl titanate Resin reaction example A Capacity 2 with stirrer, thermometer and fractional condenser
EG175g, THEIC457g in the flask,
Prepare TPA344g, MDA156g, TMA303g,
Add 1.0 g of TBT as a catalyst, heat the flask with a mantle heater, raise the temperature of the contents to a maximum of 240°C while stirring, and distill the water produced by the esterification reaction and imidization reaction out of the reaction system. The reaction continued. The reaction system becomes completely transparent,
When 129 g (98% recovery) of water produced by the reaction was recovered, heating was stopped, and the reactant was transferred to a tin can, cooled and ground to obtain a polyesterimide resin. Example 1 600 g of the polyesterimide resin obtained in Resin Reaction Example A and 440 g of acetophenone were charged into a flask with a capacity of 2 equipped with a stirrer, a thermometer, and a cooling tube.
It was heated to 140°C to completely dissolve it. Then cool to 50 °C and make 50% of the phenol formaldehyde resin.
Add and mix 24 g of acetophenone solution and 48 g of 50% TPT acetophenone solution, and heat again at 120℃ for 2 hours.
After being subjected to heat treatment for an hour, it was passed through qualitative paper. The resulting insulating paint had a calculated resin content of 55%, an actual measured (2g, 200°C, 2hrs) resin content of 54.2%, and a viscosity of 54 poise at 30°C. Comparative Example 1 In a flask similar to Example 1, 600 g of the polyesterimide resin of Resin Reaction Example A and 658 g of m-p-cresol were charged and dissolved by heating to 140°C. After that, cool to 50℃, add 24g of 50% cresol solution of phenol formaldehyde resin and TPT.
Add 48g of 50% cresol solution and mix again.
After heat treatment at ℃ for 2 hours, it was filtered using qualitative paper. The obtained comparative insulating paint has a calculated resin content of 46% and an actual resin content (2g, 200℃, 2hrs) of 45.0
%, and the viscosity was 52 poise at 30°C. Resin reaction example B EG202g, THEIC350g, TPA360g,
Perform the same reaction as resin reaction example A except using 164 g of MDA and 317 g of TMA, and 136 g of water produced by the reaction.
(99% recovery) Upon collection, heating was stopped, the reactant was transferred to a tin can, cooled and pulverized to obtain a polyesterimide resin. Example 2 A flask similar to Example 1 was charged with 600 g of the polyesterimide resin obtained in Resin Reaction Example B, 387 g of acetophenone, and 50 g of p-methylacetophenone, heated to 140°C, dissolved, and then heated to 80°C to dissolve phenol formaldehyde. 48 g of a 50% acetophenone resin solution and 60 g of a 50% TPT acetophenone solution were added and mixed, and an insulating paint was obtained in the same manner as in Example 1. The actual resin content was 53% and the viscosity was 50.5 poise. Comparative example 2 600g of polyesterimide resin of resin reaction example B,
M, p-cresol 664g, phenol formaldehyde resin 50% cresol solution 48g, TPT
A comparative insulating paint was obtained in the same manner as in Example 1 except that 60 g of 50% cresol solution was used. The actual resin content was 43.8% and the viscosity was 52 poise. Resin reaction example C EG87g, DEG149g, THEIC460g, TPA220
The reaction was carried out in the same manner as in Resin Reaction Example A, except that g, MDA 200 g, and TMA 388 g were used, and the water produced by the reaction was
Heating was stopped when 118g (98% recovery) was collected.
The reaction product was transferred to a tin can, cooled and ground to obtain a polyesterimide resin. Example 3 An insulating paint was obtained in the same manner as in Example 1 using 600 g of the polyesterimide resin obtained in Resin Reaction Example C, 441 g of acetophenone, and 60 g of a 50% TBT acetophenone solution. The actual resin content is 52%.
The viscosity was 70 poise. Comparative Example 3 600 g of polyesterimide resin obtained in Resin Reaction Example C, 5% commercially available phenol, 40 cresol
%, cresylic acid 689 containing 55% xylenol
g, using 60 g of 50% cresylic acid solution in TBT,
A comparative insulating paint was obtained in the same manner as in Example 1.
The actual resin content was 42.3% and the viscosity was 67 poise. Resin reaction example D 298g of EG, 505g of TMA, and 1.4g of TBT were placed in a second flask equipped as in resin reaction example A.
After heating and stirring at 150℃ until it becomes transparent, GL42g,
Prepare 215 g of MDA and 162 g of TPA, and then react in the same manner as in resin reaction example A.
Heating was stopped when 126g (98% recovery) was collected.
After cooling to 180°C, 655 g of acetophenone was added and dissolved. Example 4 To the polyesterimide resin solution obtained in Resin Reaction Example D, 154 g of a 50% acetophenone solution of tetrabutyl titanate was added and mixed at 80°C, and the mixture was passed through qualitative paper to obtain an insulating paint. Actual resin content is 55%
The viscosity was 54 poise. Resin reaction example E Into the same flask as in resin reaction example A, add 265 g of EG,
455 g of TMA and 47 g of MDA were charged and reacted by heating at 160 to 190°C. After collecting 30g of reaction product water,
147 g of TPA, 294 g of THEIC, and 187 g of MDA were added and reacted in the same manner as in Example 1, and the reaction was stopped when a total of 170 g of reaction product water and azeotropic EG were recovered. The reaction product was transferred to a tin can, cooled and ground to obtain a polyesterimide resin. Example 5 An insulating paint was obtained in the same manner as in Example 1 using 600 g of the polyesterimide resin obtained in Resin Reaction Example E, 445 g of acetophenone, and 30 g of triethanolamine titanate. The actual resin content was 55% and the viscosity was 47 poise. Comparative Example 4 A comparative insulating paint was obtained in the same manner as in Example 1 using 600 g of the polyesterimide resin obtained in Resin Reaction Example E, 765 g of commercially available cresylic acid, and 30 g of triethanolamine titanate. The actual measured resin content is
42.5%, viscosity is 44 poise. Resin reaction example F EG159g, THEIC326g, GL115g, TPA612
The reaction was carried out in the same manner as in Resin Reaction Example A except that 105 g of TMA, 105 g of MDA, and 55 g of MDA were used, and heating was stopped when 150 g (98% recovery) of reaction product water was recovered. The reaction product was transferred to a tin can, cooled and ground to obtain a polyesterimide resin. Example 6 Polyesterimide resin obtained in Resin Reaction Example F
600g, acetophenone 635g, 50% acetophenone solution of phenol formaldehyde resin 72g,
A polyesterimide resin wire enamel was obtained by carrying out the same operation as in Example 1 using 60 g of a 50% solution of TPT in acetophenone. Actual resin content is 46
%, and the viscosity was 53 poise. Comparative Example 5 Polyesterimide resin obtained in Resin Reaction Example F
600g, 1010g of cresol, 72g of 50% cresol solution of phenolformadehyde resin, TPT.
A comparative insulating paint was obtained by carrying out the same operation as in Example 1 using 60 g of a 50% cresol solution. The actual resin content is 36% and the viscosity is 50 poise. Example 7 Insulating paint obtained in Examples 1 to 6 and Comparative Example 1
The comparative insulating paint obtained in steps 5 to 5 was baked onto a copper wire having a diameter of 1 mm to make an enamelled wire, and the wire characteristics of each wire were measured. The line drawing conditions are an effective furnace length of 3 m, 6
The coating was applied twice at a line speed of 6.5 m/min, and the testing and judgment methods were conducted in accordance with JIS C-3003 and 3214. The measurement results were as shown in Table 1.

[Table] As is clear from Table 1, the insulating paint of the present invention has properties equivalent to or superior to conventional products using phenols as solvents.
As is clear from the examples, the amount of solvent used can be reduced and the resin concentration can be increased compared to the conventional phenol solvent type, which is very beneficial from the viewpoint of resource saving. Furthermore, the insulating paint of the present invention has no irritating odor, is fragrant, and has low toxicity, making it easy to handle compared to conventional products that use phenols as the main solvent.

Claims (1)

[Claims] 1. An aliphatic dihydric alcohol, a trivalent or higher polyhydric alcohol, an aromatic tribasic acid alone or both the tribasic acid and an aromatic dibasic acid, and an aromatic polyamine,
The equivalent ratio of hydroxyl and carboxyl groups is
1.2/1 to 4.0/1, and the hydroxyl group of trihydric or higher polyhydric alcohol accounts for 20% of the total hydroxyl groups.
The polyesterimide resin () and the curing agent () obtained by reacting the carboxyl groups participating in imide group formation in a component proportion of ~80 equivalent% and 5 to 50 equivalent% of the total carboxyl groups are expressed by the general formula [Formula] (In the formula, R represents a hydrogen atom, an alkyl group having 1 to 2 carbon atoms, or an alkoxy group.) An insulating paint obtained by dissolving acetophenones represented by the following formula or a mixed solvent of the acetophenones and another solvent. 2. The insulating paint according to claim 1, wherein the acetophenone is acetophenone.