JPS6241410B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a resin-molded coil.

A conventionally widely used method for manufacturing resin molded coils is a method using a mold.
In this method, a coil is placed in a mold, impregnated with a resin such as epoxy resin (solvent-free varnish) and cured in a heating furnace, and then the mold is removed to obtain a resin-molded coil. be. Therefore, in this method, an expensive mold is used until the final stage of the coil manufacturing process, and a large number of molds must be prepared, which is extremely uneconomical.
This is particularly noticeable in the case of high-mix, low-volume production. Furthermore, molds must be released each time they are used, such as by applying a mold release agent, and there are many complicated operations such as disassembling and reassembling the molds, which can significantly reduce work efficiency. It was hot.

For this reason, there is a strong demand for the emergence of a method for rationally manufacturing resin-molded coils without using the above-mentioned molds. Attempts have been made to cover the coil, to melt and apply a solid substance such as wax to the coil, and to cure the resin while rotating the coil. All of these manufacturing methods attempt to deal with the problem of how to prevent resin from flowing out of the coil after impregnation, but each has the following drawbacks, and it has not been possible for them to be widely put into practical use. has not been reached yet. The reason is,
Among the characteristics of the resin used for coil impregnation casting, the limitations stem from the characteristics of low viscosity and long pot life, which are particularly required for processing surfaces. The point is that it cannot be prevented.

In other words, the resin used for coil impregnation casting is required to completely fill the minute voids in the structures made up of components such as electric wires and various thin insulation materials, and in a short period of time. It is important that there be. Furthermore, since it is intended to eliminate the need for molds, the coil to be treated is generally completely impregnated in a tank filled with a large amount of resin, and the resin used is suitable for stable work that can be used repeatedly. It is important that the product is made at a low temperature and has a long pot life. By the way, in order to lower the viscosity, there is a system that mixes a reactive diluent, but if a large amount of this reactive diluent is added, the properties of the cured product deteriorate, for example, it becomes brittle and cracks easily, and the heat distortion temperature This leads to unfavorable trends such as a decrease in Therefore, the viscosity is often reduced by not adding a diluent, or by adding only a small amount, and by heating the resin itself to a medium temperature. However, in this case, contradictory conditions regarding pot life are introduced, and the resin thickens in a short period of time, making it impossible to use it repeatedly. A curing accelerator is usually blended into the resin, but in order to avoid the above-mentioned situation, the system uses a reaction accelerator that has an accelerating effect at high temperatures. However, in such a system, the curing reaction of the resin naturally requires a high temperature and a long period of time, which, combined with the large heat capacity of the coil to be treated, significantly reduces the viscosity of the resin during heating and curing, which prevents the resin from leaking from the coil. This becomes extremely difficult to prevent, and even with the above-mentioned improvement measures, it is far from possible to completely prevent resin leakage.

This invention was made in order to eliminate the drawbacks of the conventional products as described above, and it is possible to use a mold by utilizing a resin blended and adjusted to have desired properties at each stage of the manufacturing process. It is an object of the present invention to provide a method for easily manufacturing a resin-molded coil in which resin does not leak from the impregnated coil without any process.

That is, to explain the properties of the resin used in this invention and the gist of the manufacturing process of a resin-molded coil using this resin, first, the properties of the resin are that it becomes easily liquefied when heated at medium temperature;
A photocurable resin is used that exhibits difficulty in fluidity or a semi-solid state at low temperatures below the medium temperature range (for example, room temperature range). Next, in the manufacturing process, the coil is impregnated with resin under medium temperature heating using an impregnating bath filled with the above resin (hereinafter referred to as process A), and then the resin is cooled to a low temperature range (hereinafter referred to as process B). Then, the surface layer is cured by ultraviolet irradiation (hereinafter referred to as step B'), and the entire resin is cured by further heating (hereinafter referred to as step C). Then, a resin molded coil is obtained.

Examples of resin compositions suitable for use in the present invention include epoxy resins that use solid acid anhydrides as curing agents at low temperatures, photocurable monomers or prepolymers, or mixtures of monomers and prepolymers. Add 15 to 45% by weight of In this case, a resin (solvent-free varnish) system that exhibits a low viscosity liquid state (for example, 10 poise or less at 100°C or lower) is required to meet the various properties required for resin molded coils, such as heat resistance, insulation resistance, strength, and abrasion resistance. If you evaluate it comprehensively in terms of its low price, etc., it can be cited as a typical product.

Next, this invention will be explained specifically and in detail. In step A, the resin composition may be one that becomes easily liquefied and has a low viscosity when heated to about 60 to 100°C, and the resin composition has good impregnation into the coil. Under these medium-temperature heating conditions, in terms of the lifespan of the resin in the storage tank, it is sufficient to use a curing accelerator for the resin component that has an accelerating effect at high temperatures. It's easy.

Next, in step B, since the resin has the above-mentioned characteristics, the entire resin is precipitated in the resin tank in the form of extremely fine particles as the acid anhydride, which is the hardening agent, is cooled. Because of this, the resin has a grease-like appearance, so even if the impregnated coil is taken out of the tank, leakage of the resin can be completely prevented. At this time, if necessary, the grease-like resin on the coil surface layer may be flattened evenly, or the adhered resin may be removed from areas where it is better not to have resin adhered (for example, the inner surface of the coil). Partial correction can be easily carried out because the situation is such that there is no resin leakage as described above.

Next, step B', which will be explained below, is inserted here. That is, the entire surface of the resin-impregnated coil that has gone through step B, including its surface and end surfaces, is irradiated with ultraviolet rays or the like to harden the surface. In this case, the coil surface is covered with a cloudy, grease-like resin, which has a frosted-glass appearance, and the photocurable component in the resin layer can be cured to a thickness of approximately 2 to 5 mm by UV irradiation. . After this light irradiation, the resin layer becomes in a state where the thermosetting epoxy resin component is trapped in the polymer of the photocurable component, and the appearance of the resin layer changes from a grease-like appearance to a hard leather-like or plastic-like appearance. Since the fluidity of the resin is further reduced, leakage or deformation of the resin is completely prevented.

Furthermore, the coil that has gone through this process B' is then processed through the next process C.
The resin is cured at high temperatures (for example, 130 to 150°C), but even at this time, leakage of the resin can be completely prevented.

In this way, the present invention provides a rational method for manufacturing resin-molded coils that solves the drawbacks of conventional methods by integrating the characteristics of the resin composition into a process that effectively utilizes the characteristics of the resin composition at each stage of the coil manufacturing process. It provides:

Next, each component of the resin system suitably used in this invention will be explained. As an epoxy resin,
Those having two or more oxirane rings in the molecule, such as dibricidyl ether of bisphenol A, alicyclic epoxy, novolac type epoxy, etc., and acid anhydrides that are solid at room temperature, such as phthalic anhydride, Tetrahydrophthalic anhydride, succinic anhydride, maleic anhydride, hexahydrophthalic anhydride, etc. are blended singly or in a mixed system. In addition, as curing accelerators, amine complexes of boron trifluoride, tri-(dimethylaminomethyl)phenol and its salts, tertiary amines such as α-methylbenzyldimethylamine, zinc octylate, octylic acid Salts or complexes of transition metals such as cobalt are usually added from 0.1 to 3 phr (for a given substance
The weight of the substance to be added per 100g) can be added. Photocurable monomers and/or prepolymers include compounds having one or more polymerizable unsaturated groups in the molecule, such as ethylene glycol di(meth)acrylic ester, propylene glycol di(meth)acrylic ester, and neopentyl glycol. Condensation of polyfunctional monomers with high boiling points and low viscosity, such as di(meth)acrylic ester and trimethylolpropane tri(meth)acrylate, alone or in a mixed system, and also with polyester polyol and (meth)acrylic acid. Prepolymers such as monomers and epoxy acrylates are used alone or in combination with the above monomers. Furthermore, a mixture of vinyl monomers such as alkyl (meth)acrylates (e.g. tridecyl, stearyl, etc.), glycidyl (meth)acrylate, mono(meth)acrylate of glycol, styrene, vinyltoluene, etc. with the above polyfunctional monomer or prepolymer. For example, it can be used in a system. Sensitizers added to these photocurable monomers and/or prepolymers include compounds that generate radicals when exposed to light in a specific wavelength range, such as carboxyl compounds such as benzoin methyl ether, benzoin ethyl ether, and benzoin isobutyl ether. ,
Quinone compounds such as anthraquinone, benzoquinone and naphthoquinone, and sulfide compounds such as diphenyl disulfide may be blended in an amount of usually 0.01 to 5% by weight.

Resins made from each of these compositions include the above acid anhydride-curable epoxy resin, a photocurable monomer and/or
or 15 to 45% by weight of prepolymer, preferably 20
It can be obtained by blending up to 35% by weight. In addition, if the blending amount of the monomer and/or prepolymer is small, the epoxy resin, which is the main ingredient, may leak when moving to the above-mentioned step C. This is not preferable because it makes the work such as rotating and curing the object complicated. vice versa,
If the amount of the above-mentioned monomer and/or prepolymer is too large, the resin system must be cooled to a considerably low temperature in Step B, for example, in order to thicken it to a grease-like state or make it semi-solid. First, in places such as high-temperature work environments, moisture condenses in the resin tank or on the objects to be treated, which is undesirable since it has an adverse effect on the curing characteristics. Therefore, the amount to be added may be determined from the above-mentioned blending range.

Next, a process for implementing this invention will be described. The resin tank is equipped with a heating and cooling function and a vacuum and pressurizing mechanism.
To enable rapid resin impregnation and cooling in step B. In addition, the light source for the light irradiation in step B' may be any source that efficiently generates ultraviolet rays, such as low-pressure mercury lamps, high-pressure or ultra-high-pressure mercury lamps, germicidal lamps, xenon lamps, and even sunlight. Can be done. The arrangement and number of these ultraviolet radiation sources can be adjusted as appropriate so that the entire surface of the object to be treated can be irradiated. In addition, photocuring can be achieved by attaching the workpiece to a rotating jig and irradiating it with light while rotating it, or by replacing the atmosphere with an inert gas such as carbon dioxide or nitrogen gas during the irradiation. This is preferable because it can be carried out effectively.

As described above, according to the present invention, the workpiece that has been impregnated with resin at medium temperature and then cooled to a low temperature range is impregnated and coated with a thixotropic grease-like resin, so it remains as it is. There is no resin leakage even if the coil is left alone, so it is easy to apply cosmetic measures to the treated object at this stage, such as flattening the surface to improve the finish of the coil, if necessary. . In addition, in the above light irradiation process, if the object to be treated is heavy, for example, the light source side may be transportable for light irradiation, or the entire object may be rotated as a system. Light irradiation is also possible. The workpiece that has undergone this light irradiation process is heated to a high temperature and transferred to the main curing process, but since the resin on the surface layer of the workpiece has already changed from a grease-like state to a solid state, the workpiece is rotated and dried. It is possible to carry out the main curing in a stationary state without performing any other steps, and it is possible to obtain a resin-molded coil.

An embodiment of this invention will be shown below.

Example 1 As a resin, an epoxy resin was prepared by homogeneously dissolving 80 phr of tetrahydrophthalic anhydride and 3 phr of zinc octylate in a low molecular weight bis A type epoxy resin (Epicote 828: Ciel Chemical trade name, the same applies hereinafter) by heating it to about 100°C. This epoxy resin is mixed with 25% by weight of trimethylolpropane triacrylate and 4% by weight of benzoin ethyl ether. This resin was a pale yellow, transparent liquid with a viscosity of 70 centipoise at 60°C, and when cooled to 30°C, it became a cloudy, cloudy grease with poor fluidity.

The raw coil was placed in a vacuum impregnation tank equipped with heating and cooling functions, then filled with the above resin and heated for 60 minutes.
After resin impregnation at a medium temperature of ~70°C, the impregnation tank was cooled and the coil was taken out when the temperature inside the tank reached approximately 30°C. This coil appeared to have its entire surface covered with a grease-like resin. Next, in order to remove the wavy wrinkles in the grease-like resin on the surface of the coil, the coil was attached to a rotating jig and gently rotated, while a spatula-shaped jig was applied to flatten the coil. During these steps, no resin leaked from the coil.

Next, the entire surface of the coil was irradiated with ultraviolet rays for 5 minutes at a distance of 15 cm under an ultra-high pressure mercury lamp with an output of 8 KW. The coil that has undergone this process has a surface layer of about 3 mm in solid phase, and has a pale yellowish-white, hard leather-like appearance. Next, when this coil was kept stationary in a heating furnace at 150°C and thermally cured for 10 hours, a good resin-molded coil was obtained with no problems such as resin leakage.

Example 2 40 phr of tetrahydrophthalic anhydride and hexahydrophthalic anhydride in Epicote 828 as resin
40phr and boron trifluoride monoethylamine 1phr 80
Mix an epoxy resin homogeneously dissolved by heating to ~90°C, and add 10% by weight of neopentyl glycol diacrylate and 15% by weight of epoxy acrylate (adduct of 1 mole of Epicote 828 and 2 moles of methacrylic acid) to this epoxy resin. % and 4% by weight of benzoin isobutyl ether was used.
This resin was a pale yellow transparent liquid with a viscosity of 100 centipoise at 60°C, and when cooled to 20°C it became cloudy and grease-like.

The first coil is placed in a vacuum impregnation tank equipped with heating and cooling functions, then filled with the above resin and impregnated with the resin at a medium temperature of 60 to 70°C. When the temperature reached approximately 20°C, the coil was removed, and the coil wrapped in grease-like resin was attached to a rotating jig and left stationary. Next, the second coil was treated with a resin in the same manner as the first coil, cooled, and taken out from the impregnation tank. The first one, which had been abandoned for a while,
No resin leakage was observed from the coil.

Next, these first and second coils were simultaneously irradiated with ultraviolet rays in the same manner as in Example 1, and further heat-cured to obtain a good resin-molded coil.

Comparative Example As a resin, a mixture of Epicote 828, 80 phr of liquid acid anhydride HN-2200 (trade name of Hitachi Chemical), and 1 phr of benzyldimethylamine was used. This resin has a viscosity of 80 centipoise at 75°C.
It was 950 centipoise at 25°C.

The raw coil was placed in the same resin impregnation tank as in Example 1, and vacuum impregnated with the resin at a medium temperature of 75°C.
When this coil was immediately removed from the impregnation bath, severe resin leakage occurred. Further, after impregnating at a medium temperature of 75°C as described above, the impregnation tank was cooled and the coil was removed when the temperature inside the tank reached 25°C, but resin leakage was still significant. When these coils were kept stationary in a heating furnace at 150°C and thermally cured, a large amount of resin leaked, and voids and voids were generated in the insulation structure.

Claims (1)

[Claims] 1. After impregnating a coil with a resin that becomes easily liquefied when heated at medium temperature, exhibits difficulty in flowing or semi-solid at low temperatures, and has photocurability in a tank while heating at medium temperature. . A method for producing a resin molded coil, which comprises cooling the resin to a low temperature range, then curing the surface layer by irradiating the coil taken out from the tank with ultraviolet rays, and further heating at a high temperature. 2. The resin is made by adding 15 to 45% by weight of a photocurable monomer or prepolymer to an epoxy resin using an acid anhydride that is solid at room temperature as a curing agent, and then adding a curing accelerator for the epoxy resin and the monomer or prepolymer. 2. The method for producing a resin molded coil according to claim 1, wherein a small amount of a sensitizer and a sensitizer are added to form a composition that exhibits a grease-like state at room temperature and a low-viscosity liquid state at medium temperature. 3. The resin is made by adding 15 to 45% by weight of a photocurable monomer and a prepolymer to an epoxy resin using an acid anhydride as a curing agent that is solid at room temperature, and then adding a curing accelerator for the epoxy resin and the monomer and prepolymer. 2. The method for producing a resin molded coil according to claim 1, wherein a small amount of a sensitizer and a sensitizer are added to form a composition that exhibits a grease-like state at room temperature and a low-viscosity liquid state at medium temperature.