JPH0152407B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to unsaturated polyester varnish compositions that are cured by ultraviolet and microwave radiation.

Conventionally, when manufacturing resin-impregnated molded coils for electrical equipment, the coils are generally placed in a mold and resin is poured into the mold and hardened, or the coil is impregnated with the varnish and then heated and hardened to mold. .
However, recently, the need to streamline the insulating varnish treatment of coils has led to the development of new varnishing processes and insulating varnish materials.

That is, as such a varnish treatment process, there is a method using ultraviolet curing, and various studies are underway on quick-drying varnishes as insulating varnishes to be used. In this method, the varnish in the coil is cured by ultraviolet irradiation, but in this case, generally only the surface varnish is cured, and only a thin hardened layer of varnish is formed on the coil surface.

Therefore, if a small coil is used, the entire varnish can be sufficiently cured, but if a large coil is used, the following problems arise.

In the heating furnace for curing varnish, heat is absorbed by parts with large heat capacity, and a considerable amount of time is spent warming the varnish. Even if the varnish were to dry quickly, the time saving effect would be significant. will be reduced.

On the other hand, varnish curing treatment using microwave irradiation is being considered. As is well known, the internal heating method using microwaves is a very efficient heating means.

Microwaves are electromagnetic waves that occupy the range between radio waves and infrared waves, and have a frequency of 30MHz~
300GHz, the wavelength is 1 to 10 ^-3 m, but the frequency band that can be used industrially is regulated by the Radio Law.
In the frequency range of 2453-2454MHz.

The polymerizable resin is efficiently heated in such a heating curing furnace using microwave frequencies and can be cured in a short time. Therefore, various insulating varnishes for microwave heating curing are being developed, and unsaturated polyester insulating varnishes are generally used. It is said to be 20 minutes. That is, according to the curing method using microwave heating, the varnish treatment is
It is attracting much attention as an insulation treatment because it greatly shortens the insulation treatment process and has the effect of saving energy.

However, on the other hand, the reality is that the surface of the cured product remains sticky and there is a strong desire to improve its surface drying properties.

In order to improve the surface drying properties, the present inventors first cured the varnish layer on the coil surface by UV irradiation, and then cured the varnish on the entire coil by microwave heating, thereby achieving surprisingly good characteristics. The present invention was completed by discovering that a molded coil impregnated with resin can be obtained.

That is, the present invention consists of an unsaturated polyester prepolymer produced by a polycondensation reaction of glycols and polybasic acids, a radically polymerizable monomer of 25 to 90% in the total amount of varnish, and diallyl having a microwave heating effect of 15 to 90% of the total amount of varnish. An unsaturated polyester varnish composition consisting of phthalate and 3 to 30% of an ultraviolet polymerizable monomer, and an appropriate amount of two types of radical polymerization initiators, a thermal polymerization type and an ultraviolet polymerization type initiator. be.

In the present invention, the unsaturated polyester prepolymer is one obtained by polycondensation reaction of glycol, unsaturated polybasic acid, and saturated polybasic acid. Examples of unsaturated polybasic acids include maleic anhydride, fumaric acid,
Examples of saturated polybasic acids include citraconic acid and itaconic acid.Saturated polybasic acids include tetrachlorophthalic anhydride, hedic acid, tetrabromophthalic anhydride, phthalic anhydride, isophthalic acid, terephthalic acid, endomethylenetetrahydrophthalic anhydride, and tetrahydrophthalic anhydride. acids, hexahydrophthalic anhydride, succinic acid, adipic acid, azelaic acid, sebacic acid, etc.

In addition, as glycols, ethylene glycol, propylene glycol, butanediol 1.4,
Butanediol 1.3, butanediol 2.3, diethylene glycol, dipropylene glycol, triethylene glycol, pentanediol 1.5, hexanediol 1.6, neopentyl glycol,
2,2,4 trimethylpentanediol-1.3,
Hydrogenated bisphenol A, 2,2-di(4-hydroxypropoxyphenyl)propane, pentaerythritol diallyl ether, glycerin, trimethylene glycol, 2-ethyl-1,3-hexanediol, phenyl glycidyl ether, allyl glycidyl ether, etc. There is. By combining these glycols and polybasic acids, the amount of glycol is slightly increased in equivalent ratio (approximately 10% increase),
Polycondensation reaction is carried out at a temperature of 150 to 200℃ to increase the acid value.
A prepolymer of 50 or less is used as a varnish composition.

Next, as radical polymerizable monomers, styrene, vinyltoluene, α-methylstyrene, chlorostyrene, divinylbenzene, diallyl phthalate, triallyl cyanurate, N-vinylpyrrolidone, maleimide, vinyl acetate, methyl methacrylate, methyl acrylate , ethylene acrylate, etc. can be used, but diallyl phthalate has been found to have a particularly remarkable temperature-raising effect in microwave heating.

These monomers may be used alone or in combination of several types. In particular, it is recognized that the temperature of the diallyl phthalate monomer increases to about 110 to 120°C in about 10 seconds by microwave irradiation.

Such a temperature increase is not observed with ordinary styrene monomers, and in particular by adding the allyl phthalate to the unsaturated polyester prepolymer, an unsaturated polyester varnish with a remarkable heating effect as described above can be obtained.

Next, as the ultraviolet polymerization initiator in this invention, benzoin ethyl ether, benzophenone, t-butylanthraquinone, bromoacetophenone, Mihiraketone, di-t-butyl peroxide, azobisisobutyronitrile, thioxanthone derivative, benzoin, These include dibenzothiazolyl sulfide, carbon tetrabromide, and ferric ion compounds (citric acid/ferric ammonium).

Further, examples of ultraviolet polymerizable monomers include methacrylic esters and acrylic esters. Here, the methacrylic esters include methyl methacrylate, ethyl methacrylate, n-
Butyl methacrylate, isobutyl methacrylate, 2-ethylhexyl methacrylate, n-butoxyethyl methacrylate, isodecyl methacrylate, lauryl methacrylate, stearyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene Glycol dimethacrylate, polyethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, tetrahydrofurfuryl methacrylate, glycidyl methacrylate,
Tetraethylene glycol dimethacrylate,
1.3 butanediol dimethacrylate, 1.3 butylene glycol dimethacrylate, 1.4 butylene glycol dimethacrylate, 1.6 hexane glycol dimethacrylate, neopentyl glycol dimethacrylate, dipropylene glycol dimethacrylate, polypropylene glycol dimethacrylate, 2,2'-bis(4- Examples include methacryloxydiethoxyphenyl)propane and dicyclopentenyloxyethyl methacrylate.

Examples of acrylic esters include butoxyethyl acrylate, ethyl carbitol acrylate, methyl triglycol acrylate, stearyl acrylate, tetrahydrofurfuryl acrylate, benzyl acrylate, diethylene glycol diacrylate, neopentyl glycol diacrylate, 1.5 pentanediol diacrylate, 1.6 hexanediol diacrylate,
Trimethylolpropane triacrylate, pentaerythritol triacrylate, butyl acrylate, 2-ethylhexyl acrylate, glycidyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, dicyclopentenyloxyethyl acrylate, polyethylene glycol diacrylate, polypropylene glycol diacrylate rate, 2,
2'bis(4-acryloxy-propyloxyphenyl)propane, 2,2'bis(4-acryloxy-
Examples include diethoxyphenyl)propane.

Further, the above-mentioned photocurability can also be imparted to the above-mentioned unsaturated polyester varnish by adding an oligomer having a polyfunctional vinyl group. Such a photocurable oligomer already has a certain molecular weight by itself, and the amount of polymerization reaction necessary for curing and insolubilization is small, and physical properties such as viscosity can be adjusted in various ways as necessary, which is preferable.

Such photocurable oligomers include polyester acrylate, polyether acrylate,
Examples include polyurethane acrylate and epoxy acrylate.

The proportion of the unsaturated polyester prepolymer and the radically polymerizable monomer is 25 to 90%, preferably 40 to 60% (wt%, the same hereinafter) of the total amount of the varnish, and the viscosity must be low. If not, it is necessary to increase the amount of the monomer added. However, by adjusting the amount of the radically polymerizable monomer in accordance with the concentration of unsaturated groups in the unsaturated polyester prepolymer, a three-dimensional structure with excellent mechanical strength can be obtained from the resulting cured varnish.

Next, the above diacrylphthalate is added in an amount of 15 to 90% of the total amount of monomers, and the ultraviolet polymerizable monomer (or oligomer) is added in an amount of 3 to 30%.

Next, in the present invention, a heat polymerization type radical polymerization initiator peroxide is used as a polymerization initiator.
Among them, it is preferable to use two types with different half-lives.

For example, it is preferable to use two types of peroxides, benzoyl peroxide and dicumyl peroxide, because they have a considerable difference in half-life and can respond to the rapid temperature rise of the varnish caused by microwave irradiation. Furthermore, in the present invention, an ultraviolet polymerization initiator that generates radicals upon irradiation with ultraviolet light is added. These initiators are preferably of a heat polymerization type and an ultraviolet polymerization type in an amount of 0.1 to 3% each, preferably 1% each.

Specifically, in order to insulate the coil of a motor using the impregnated varnish according to the present invention, the coil is impregnated in the impregnated varnish, taken out, and irradiated with ultraviolet rays from a high-pressure mercury lamp while rotating the coil. Harden the varnish layer on the coil surface in 10 seconds to several minutes. By hardening the varnish on the coil surface, leakage of the varnish inside the coil can be prevented to some extent.

Next, the coil with only the surface layer hardened is placed in a microwave heating furnace and heated by microwaves for several minutes to several tens of minutes, so that the varnish inside the coil is sufficiently hardened and a resin-impregnated molded coil is obtained.

The present invention will be specifically explained below using examples.

(Example) 441 g of maleic anhydride, 75 g of succinic anhydride, 111 g of phthalic anhydride, 251 g of propylene glycol,
102 g of ethylene glycol and 175 g of diethylene glycol are mixed in a four-necked flask and reacted at around 120°C, and reflux is continued until a large amount of water is produced. While removing the produced water from the reaction system,
The reaction was carried out at ℃ for 2 to 3 hours, and the reaction was further continued until around a predetermined amount of dehydration to obtain an unsaturated polyester prepolymer having an acid value of 35. At the end of the reaction, add 0.1% hydroquinone, and when the temperature of the reactant drops below 80℃, add 200g of styrene and diallyl phthalate.
400 g and 50 g of neopentyl glycol diacrylate were added and stirred well to obtain an unsaturated polyester varnish with a solid content of about 60%.

To 100 parts of this varnish, 0.5 part of benzoyl peroxide, 0.5% of dicumyl peroxide, and 1.0 part of benizoin ethyl ether were added as polymerization initiators.

A stator coil of an electric motor, which is composed of an insulated conductor made of enamelled copper acid, an iron core made of a silicon steel plate, and an insulating base material made of aramid paper and polyester film, is impregnated with the above varnish and pulled up. While rotating, ultraviolet rays were irradiated for 5 minutes using a high-pressure mercury lamp. Next, the coil was placed in a 5 KW, 2450 MHz microwave heating furnace and irradiated for about 20 minutes to obtain a resin-impregnated molded coil. The obtained coil has a retention rate of impregnated varnish in the coil that is approximately 20% higher than that of a comparative example coil obtained by conventional insulation treatment, and also has excellent electrical and mechanical properties. It was hot. Regarding the above-mentioned varnish of the present invention, the general characteristics of the cured product obtained by curing it under the same conditions as the above-mentioned coil manufacturing conditions are (i) volume resistivity: 9.1×10 ¹⁵ Ω-cm;
(ii) Dielectric breakdown strength 4.3KV/0.1mm, (iii) Tensile strength 6.1
Kg/mm ² and these values were found to be almost the same as those of general unsaturated polyester resins.

Claims (1)

[Claims] 1. An unsaturated polyester prepolymer produced by a polycondensation reaction of glycols and polybasic acids, a radically polymerizable monomer of 25 to 90% of the total amount of varnish, and 15 to 90% of the total amount of varnish.
Consists of 90% diallyl phthalate, which has a microwave heating effect, and 3 to 30% ultraviolet polymerizable monomer, and also contains an appropriate amount of two types of radical polymerization initiators: thermal polymerization type and ultraviolet polymerization type initiators. An unsaturated polyester varnish composition.