JPH0629380B2 - Manufacturing method of electrical insulation paint - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing an electrically insulating paint capable of coating baking at high speed and greatly improving the production efficiency of an enameled wire.

(Prior Art) High-speed paint baking for the purpose of speeding up the production of enameled wire and improving the productivity to reduce costs, as well as quickly responding to customer requests and improving services. It is desired to develop a polyester-based electric insulating paint for enamel wire (hereinafter simply referred to as electric insulating paint) that can be used.

When the conventional insulating paint is baked at high speed as it is, the curing degree of the coating film is insufficient, so that the properties such as cut-through temperature and abrasion resistance are degraded, and it is applied in multiple layers while the curing degree is insufficient. Due to repeated baking, the coating film partially softens and flows, causing foaming and unevenness, resulting in loss of surface smoothness.

If the baking oven temperature is raised, the degree of hardening rises, and the characteristics such as cut-through temperature and wear resistance fall within the acceptable range, but since the furnace temperature is high, the amount of volatile components during baking increases and the surface of the enamel wire increases. Foaming easily occurs. In addition, in order to raise the furnace temperature, extra energy is required, which is contrary to the purpose of cost reduction. In order to avoid such inconvenience, secondary resin such as polyamide resin, phenol resin, melamine resin is added to conventional insulating paint,
Attempts have been made to add a large amount of various metal salts having a catalytic action, but none have been obtained that satisfy both the characteristics and appearance of enameled wire.

(Problems to be Solved by the Invention) The present invention has been made to solve such problems, and the characteristics and appearance of the enameled wire are equal to or higher than those of the conventional product, and the coating baking speed is the same as that of the conventional product. It is an object of the present invention to provide a method for producing an electrically insulating coating which can be made 20 to 30% faster than the above.

(Means for Solving Problems) In the present invention, the polycarboxylic acid or its derivative and the polyhydric alcohol are trivalent or higher polyhydric alcohols in an amount of 50 equivalent% or more based on the total polyhydric alcohol, and the reaction rate of the carboxyl group is 70
%, The number average molecular weight in terms of polystyrene is more preferably 1500 in the presence of a catalyst.
The present invention relates to a method for producing an electrically insulating coating material in which a resin obtained by heating and reacting at 130 to 200 ° C. until dissolved in an organic solvent is dissolved in an organic solvent.

Examples of polycarboxylic acids are terephthalic acid, isophthalic acid, phthalic acid, trimellitic acid, pyromellitic acid, trimesic acid, bicyclo- [2,2,2] -oct- (7)-
En-2: 3: 5: 6-tetracarboxylic acid, 1,2,
3,4-butanetetracarboxylic acid, 1,2,3-butatricarboxylic acid, 1,2,4-butanetricarboxylic acid, adipic acid, succinic acid, sebacic acid and the like are mentioned and not particularly limited. Moreover, the diamine or aminocarboxylic acid which is an imidic acid-forming component and the tribasic acid anhydride may be added first, or may be added as a separately synthesized imidic acid. Derivatives of polycarboxylic acids refer to anhydrides, esters and chlorides of these acids.

Examples of polyhydric alcohols are ethylene glycol, propylene glycol, dipropylene glycol, 1,3-butanediol, 1,6-hexadiol, diethylene glycol, neopentyl glycol, glycerin, tris (2-hydroxyethyl isocyanurate) trimethylolpropane, Examples include trimethylolethane, pentaerythritol, and sorbitol.

The polyvalent carboxylic acid or its derivative and the polyhydric alcohol can be reacted by an ordinary method except the conditions described below, and there is no particular limitation. It is preferable to use a catalyst for the reaction, which allows the reaction to proceed in a short time.

When the polyhydric carboxylic acid or its derivative is reacted with the polyhydric alcohol, the polyhydric alcohol having a valence of 3 or more must be 50 equivalent% or more of the total polyhydric alcohol. If the amount of the trihydric or higher polyhydric alcohol is less than 50 equivalent%, the cross-linking density of the coating film after baking will be insufficient, and the properties such as cut-through temperature and abrasion resistance will be poor. Also, when the amount exceeds 80 equivalent%, the flexibility tends to decrease. Therefore, it is preferable to use trihydric or higher polyhydric alcohol in an amount of 80 equivalent% or less. Consider the cut-through temperature and the balance of flexibility. Then, it is particularly preferable to set it in the range of 55 to 65 equivalent%.

Equivalent ratio of hydroxyl group to carboxyl group (OH / COOH) is 1.1
0 to 1.40 is preferable, and 1.20 to 1.30 is particularly preferable. If it is less than 1.10, the molecular weight becomes too large in the first-step reaction, and it is difficult to make the molecular weight distribution uniform. If it exceeds 1.40, the amount of unreacted polyhydric alcohol remaining increases.

It is necessary to react with the polyhydric carboxylic acid or the polyhydric alcohol of its derivative until the reaction rate of the carboxyl group becomes 70% or more. If the reaction rate is less than 70%, the residual rate of unreacted polycarboxylic acid or its derivative and polyhydric alcohol is high, and the amount of low molecular weight oligomers is large, so that the characteristics of the enameled wire are not sufficient. Not only that, these low-molecular components volatilize during baking, making it easier to produce irregularities on the surface of the enamel wire. The reaction rate should be as high as possible, but there is a risk of gelation when the amount of trihydric or higher polyhydric alcohol used is large.
It is particularly preferably set to 0%.

The reaction rate of the carboxyl group can be determined by a well-known method by measuring the acid value and the amount of by-products such as water and alcohol.

When the reaction is complete, cool and add the solvent to dissolve. Examples of the solvent that can be used are xylenol, cresol, phenol, N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, xylene, and aromatic hydrocarbons (for example, Hysol 100 manufactured by Nippon Oil Co., Hisol. 150) and the like. Considering the conditions of 150 to 170 ° C., which is a particularly preferable reaction temperature described later, and cost, xylenol is used as a solvent,
Preference is given to using cresol, phenol and aromatic hydrocarbons having a boiling point above 150 ° C. As it is 13
Although it may be heated to 0 to 200 ° C., it takes time until the polystyrene-reduced number average molecular weight of the resin becomes 1500 to 1700, so it is preferable to add a catalyst. Titanium alcoholates such as tetrabutyl titanate and tetraisopropyl titanate are used as catalysts,
In addition to aluminum alcoholates such as aluminum isopropylate and aluminum butyrate, zirconium alcoholates, β derived from these compounds
Examples thereof include complexes with diketones and ketoesters, and these compounds are preferably added in an amount of 0.1 to 5% by weight, more preferably 1 to 3% by weight, based on the resin. If the addition amount is less than 0.1% by weight, the accelerated curing of the reaction is poor, and if it exceeds 5% by weight, the flexibility of the enamel wire tends to decrease. Although the content of the reaction that occurs when heated to 130 to 200 ° C is not clear enough,
As shown below, polyester resin reacts with metal alcoholate added as a catalyst, phenols added as a solvent, water in the system, etc., as the average molecular weight is reduced and the molecular weight distribution is averaged. It is presumed that When the metal alcoholate itself is reacting, it is outside the definition of a catalyst in a strict sense, but here, the metal alcoholate is broadly interpreted as a catalyst.

The reaction temperature is 130 to 200 ° C. If the temperature is lower than 130 ° C., the reaction rate for homogenizing the molecular weight distribution becomes extremely slow. Further, when the temperature exceeds 200 ° C., not only the molecular weight distribution becomes uniform, but also the opposite molecular weight increasing reaction occurs at the same time, so that the intended electrically insulating coating cannot be obtained. Considering these and the ease of controlling the reaction, 140 to 180 ° C is more preferable, and 150 to 170 ° C is particularly preferable.

At such a temperature, the polystyrene-equivalent number average molecular weight is 1
React until 500-1700. When the number average molecular weight exceeds 1700, unevenness is likely to occur on the surface of the menamel wire, and when it is less than 1500, the cut-through temperature and abrasion resistance decrease. The number average molecular weight is, for example, a column: gel pack, R420, R4 manufactured by Hitachi Chemical Co., Ltd.
30, R440; elution solvent: tetrahydrofuran; detector: differential refractometer; pressure: 40 kgf / cm ² , temperature: 350
The molecular weight distribution can be measured by liquid chromatography (HLC) under the conditions of ° C and a flow rate of 2.0 ml / min, and can be calculated by a conventional method using a separately prepared calibration curve of polystyrene. If a correlation curve between the solution viscosity of the resin and the number average molecular weight is prepared in advance, the reaction can be easily controlled by measuring the viscosity of the solution sampled from the reaction system. By the way, the HLC chromatogram of the resin before heat treatment has two main peaks, and the number average molecular weight is 2,000-2,500.
There is one main peak after heat treatment until it reaches 1500 to 1700, and the overall shape is much closer to the normal distribution as compared with before heat treatment. It is considered that since the molecular weight distribution is averaged in this way, curing uniformly occurs, and even if the coating is baked at high speed, no unevenness is generated on the surface of the enamel wire, and a smooth and uniform coating film is formed.

The electric insulating coating material thus obtained is used as it is, or is diluted with a solvent as described above for practical use.

Various additives may be added for the purpose of improving the curability of the electrically insulating paint during baking and the characteristics of the enameled wire. Examples of such additives include zinc naphthenate,
In addition to metal salts of organic acids such as zinc octenoate, cobalt naphthenate, iron octenoate, the aforementioned metal alcoholates such as titanium, aluminum, zirconium and their derivatives, melamine resin, phenol resin,
Examples of the resin include xylene resin, furan resin, epoxy resin and polyamide resin, and it is preferable to use melamine resin and phenol resin from the viewpoint of improving the heat discoloration of the enamel wire.

(Effects of the Invention) By using the electrically insulating coating material obtained by the production method of the present invention, it is possible to solve the above-mentioned problems and meet the recent strong demands of enamel cotton manufacturers.

(Examples) Hereinafter, the present invention will be described in more detail with reference to Examples.
It goes without saying that the invention is not limited to these examples.

Example 1 In a flask 3 equipped with a stirrer, a nitrogen inlet tube, a thermometer, and a condenser, 945 g of dimethyl terephthalate, 202 g of isophthalic acid, 257 g of glycerin, and ethylene glycol 2
After adding 12g and 0.95g of lead acetate and reacting at 170 ° C for 6 hours, the temperature was raised to 225 ° C over 3 hours. At this temperature, the amount of distillate was 292g (reaction rate = 82%, by-product). It was calculated from the amount of methanol and water produced, which was the same in the following Examples and Comparative Examples). Then, it was rapidly cooled and 1568 g of cresol was added.
1400 g of this solution was added to 12.5 g of tetrabutyl titanate, and the number average molecular weight was 1680 at 155 ° C.
The reaction was carried out by heating until (measured by the above method, the same applies to the following examples). Then xylene 33
3 g was added and diluted.

Example 2 In the same manner as in Example 1, 832 g of dimethyl terephthalate,
79% isophthalic acid, 211 g glycerin, 142 g ethylene glycol, 0.87 g lead acetate with a reaction rate of 79%
It was made to react until it became. Thereafter, 972 g of cresol and 14.6 g of tetrabutyl titanate were added, and the mixture was heated and reacted at 160 ° C. until the number average molecular weight became 1590. Furthermore, 432 g of Hisol 100, Hitachi Chemical Co., Ltd.
A phenol resin VP-51NY (1.0 g, manufactured) was added.

Example 3 In the same manner as in Example 1, 925 g of dimethyl terephthalate,
Glycerin (228 g), ethylene glycol (124 g) and lead acetate (0.93 g) were reacted until the reaction rate reached 76%. Then, 1210 g of cresol and 19 g of tetraisopropyl titanate were added and reacted at 165 ° C. until the number average molecular weight became 1510.
519 g, Hitachi Chemical Co., Ltd. melamine resin ML-5
1.0 g of 23 was added.

Comparative Example 1 The reaction rate of polyhydric alcohol and polybasic acid in Example 1 was 82.
After the reaction was completed to 1%, 1568 g of cresol was added to obtain a solution of 1400 g, which was diluted with 12.5 g of tetrabutyl titanate and 333 g of xylene.

Comparative Example 2 As an example of conventional products, WH-406 manufactured by Hitachi Chemical Co., Ltd.
Was used.

The coating materials of Examples 1 to 3 and Comparative Examples 1 and 2 were applied to a copper wire having a diameter of 0.2 mm by using a felt by a conventional method, and a furnace temperature of 40
Table 1 shows the characteristics of an enameled wire with a finished outer diameter of 0.242 mm obtained by repeating baking at 0/500 ° C. (inlet / outlet) 6 times.

1) Appearance evaluation, A: The surface is smooth and good, B: There are some irregularities but it is generally good, and C: The irregularities are extremely poor.

2) Others were evaluated according to JIS C 3003.

As shown in Table 1, when the electrical insulating coating obtained according to the present invention is used, various characteristics of the enamel wire,
The baking speed can be increased by 25 to 30% as compared with the case of using the conventional electric insulating paint or the paint that does not make the molecular weight distribution uniform without impairing the smoothness of the surface. It can greatly contribute to the rationalization of the manufacturing process.

Claims (1)

[Claims] 1. A polyhydric carboxylic acid or its derivative and a polyhydric alcohol are allowed to react until the reaction rate of a carboxyl group becomes 70% or more with trivalent or more polyhydric alcohol being 50 equivalent% or more of all polyhydric alcohols. Further preferably, the polystyrene reduced number average molecular weight is 1 in the presence of a catalyst.
A method for producing an electrically insulating coating material, which comprises dissolving a resin obtained by heating and reacting at 130 to 200 ° C. to 500 to 1700 in an organic solvent.