JP2000212504A - Coating film for coil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating film for coil coating use having excellent adhesivity and thermal shock resistance, etc., suitable for effectively preventing the damage of a rotor coil of e.g. a power tool motor caused by foreign material. SOLUTION: The objective coating film for coil coating use is produced by curing a composition containing an epoxy component composed of (A) 50-100 wt.% of a bisphenol-type epoxy resin and (B) 0-50 wt.% of a urethane-modified epoxy resin having chelate-forming property and, based on 100 pts.wt. of A+B, (C) 3-15 pts.wt. of a latent curing agent such as dicyandiamide, (D) 0.5-10 pts.wt. of a cure accelerator such as toluenebisdimethylurea, (E) 1-200 pts.wt. of an inorganic filler such as calcium carbonate and (F) 3-10 pts.wt. of a thixotropic agent such as fine silica powder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating film for coil coating comprising a cured product of an epoxy resin composition.
In particular, the present invention relates to a one-pack type coating film for coil coating having excellent adhesiveness and thermal shock resistance suitable for effectively preventing a rotor coil such as a motor for a power tool from being damaged by a foreign substance. .

[0002]

2. Description of the Related Art Conventionally, as a method for preventing a rotor coil such as a motor for a power tool from being damaged by a foreign substance, for example, a coil is impregnated with a resin after winding a band-like member capable of impregnating the resin. Then, in order to fix the belt-shaped member to the coil, and to prevent the mold from collapsing due to the method of solidifying the coil and the resin impregnation of the coil, the thixotropic adhesive is partially adhered to the coil. And a method of hardening the coil by impregnation (all methods disclosed in Japanese Patent Application Laid-Open No. 8-322178) are known.

However, in the former method, the band-shaped member is difficult to handle, the workability is poor, and it is difficult to sufficiently impregnate the coil with the resin after winding the band-shaped member. There are drawbacks such as difficulty in hardening uniformly. On the other hand, the latter method has a disadvantage that the adhesion between the thixotropic adhesive and the coil is not always sufficient, and that the thixotropic adhesive easily falls off the coil while the rotor coil is rotating.

[0004]

Under such circumstances, the present invention is particularly suitable for effectively preventing a rotor coil such as a motor for a power tool from being damaged by foreign matter. The object of the present invention is to provide a coil coating film having excellent adhesiveness, thermal shock resistance and the like.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies on a coating film for coil coating having excellent adhesiveness and thermal shock resistance, and as a result, have found that bisphenol type epoxy resin,
An epoxy resin composition containing a urethane-modified epoxy resin having a chelate-forming ability, a latent curing agent, a curing accelerator, an inorganic filler, and a thixotropic agent at a predetermined ratio, particularly a one-pack type cured product, has the above-mentioned object. Found that it could conform to
Based on this finding, the present invention has been completed.

That is, the present invention provides an epoxy resin component comprising (A) 50 to 100% by weight of a bisphenol type epoxy resin and (B) 0 to 50% by weight of a urethane-modified epoxy resin having a chelate-forming ability, and 100% by weight thereof. Per part, (C) 3 to 15 parts by weight of a latent curing agent, (D) 0.5 to 10 parts by weight of a curing accelerator, (E) 1 to 20 parts of an inorganic filler.
An object of the present invention is to provide a coating film for coil coating comprising a cured product of a composition containing 0 parts by weight and (F) 3 to 10 parts by weight of a thixotropic agent.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The coating film for coil coating of the present invention comprises a cured product of an epoxy resin composition containing the following components. As the bisphenol-type epoxy resin of the component (A) in the above composition, for example, one or more arbitrary ones are selected from bisphenol A-type epoxy resin, bisphenol F-type epoxy resin, bisphenol AD-type epoxy resin and the like. Can be used. In particular, the epoxy equivalent is in the range of 170 to 300, and the viscosity at a temperature of 25 ° C is 8,000 to 2
It is preferable to use a 000 centipoise liquid bisphenol A epoxy resin alone or in combination of two or more. Also, unless the object of the present invention is impaired,
If desired, the bisphenol-type epoxy resin may be replaced with a novolak-type epoxy resin or a polyfunctional epoxy resin having an amino group at 50% by weight or less. Further, a reactive diluent having an epoxy group such as monoglycidyl ether may be used in combination with the bisphenol-type epoxy resin at a ratio of 30% by weight or less.

On the other hand, as the component (B), a liquid urethane-modified epoxy resin having a chelate-forming ability which is optionally used includes, for example, tolylene diisocyanate,
By reacting a diisocyanate compound such as isophorone diisocyanate, diphenylmethane diisocyanate, dimethylhexamethylene diisocyanate with a bisphenol-type epoxy resin such as a bisphenol A-type epoxy resin having at least one hydroxyl group in one molecule and a bisphenol F-type epoxy resin. When a urethane-modified epoxy resin is produced, a polyol having a polyaminocarboxylic acid group such as ethylenediaminetetraacetic acid, a condensed phosphoric acid skeleton, or the like is reacted.

By mixing such a urethane-modified epoxy resin having a chelate-forming ability, it is possible to prevent the thixotropy of the epoxy resin composition from changing over time.
The urethane-modified epoxy resin having chelating ability may be used alone or in combination of two or more.

In the present invention, the mixing ratio of the former (A) component bisphenol type epoxy resin and the (B) component urethane-modified epoxy resin having chelate forming ability is as follows:
The component (A) is 50 to 100% by weight, and the component (B) is 50% by weight.
It must be in the range of 0% by weight. When the amount of the component (B) exceeds 50% by weight, the heat resistance of the coating film decreases, and the viscosity of the composition increases, resulting in poor handleability. In consideration of the time-dependent change in the thixotropic properties of the composition, the viscosity, and the heat resistance of the coating film, the mixing ratio of the component (A) to the component (B) is 60 to 80% by weight of the component (A). Preferably, component B) is in the range of 40 to 20% by weight.

In the composition according to the present invention, examples of the latent curing agent used as the component (C) include dicyandiamide, urea compounds, organic acid hydrazide compounds, polyamine salt compounds, amine adduct compounds and the like. And any one or more of them can be selected and used, but dicyandiamide is preferred because it is easy to handle and easily available.

The compounding amount of the latent curing agent of the component (C) is 3 to 15 parts by weight based on the amount of the epoxy resin component, that is, 100 parts by weight of the total of the former component (A) and the component (B). Must be within the range. If the amount is less than 3 parts by weight, the curing speed of the composition is low, and if it exceeds 15 parts by weight, the coating film may be brittle. Considering the curing speed and the physical properties of the coating film, the preferred amount of the component (C) is in the range of 4 to 11 parts by weight.

In the composition according to the present invention, the curing accelerator used as the component (D) is, for example, one or more of urea compounds, phosphine compounds, imidazole compounds and the like. Although it can be selected and used, toluene bisdimethylurea and methylenediphenylbisdimethylurea are preferred from the viewpoint of the rapid curing property of the composition and the heat resistance of the coating film.

The compounding amount of the curing accelerator of the component (D) is as follows:
The amount of the epoxy resin component, that is, 0.5 to 1 based on 100 parts by weight of the total amount of the components (A) and (B)
It must be in the range of 0 parts by weight. If this amount is 0.
If the amount is less than 5 parts by weight, the curing rate may be low and the heat resistance of the coating film may be insufficient. If the amount is more than 10 parts by weight, the storage stability of the composition is reduced. Considering the curing speed, heat resistance of the coating film and storage stability of the composition, this (D)
The preferred amount of the components is in the range of 1 to 6 parts by weight.

In the composition according to the present invention, the inorganic filler used as the component (E) includes, for example, calcium carbonate, silica, alumina, aluminum hydroxide, magnesium oxide, talc, mica, clay and the like.
One or more of them can be selected and used, but calcium carbonate is preferred from the viewpoint of economy and ease of handling such as cutting properties of the coating film. The calcium carbonate is not particularly limited, and any of precipitated calcium carbonate, heavy calcium carbonate, light calcium carbonate and the like can be used.

Advantageously, the inorganic filler has an average particle size of usually 0.5 to 35 μm, preferably 1 to 10 μm, in view of the viscosity of the composition and the dischargeability of the dispenser. The compounding amount of the inorganic filler of the component (E) is 1 to 20 with respect to the amount of the epoxy resin component, that is, 100 parts by weight of the total amount of the components (A) and (B).
It must be in the range of 0 parts by weight. If the amount is less than 1 part by weight, a coating film having good heat radiation properties, heat resistance and curing shrinkage properties cannot be obtained, and if it exceeds 200 parts by weight, the viscosity of the composition becomes high and the handleability deteriorates. Considering the properties of the coating film and the viscosity of the composition, the preferred amount of the component (E) is in the range of 30 to 100 parts by weight.

In the composition according to the present invention, the thixotropic agent used as the component (F) may be, for example, one or two kinds of arbitrary ones from among particulate silica, particulate alumina, particulate calcium carbonate and the like. More than one kind can be selected and used, but from the viewpoint of the sagging prevention ability of the composition, particulate silica is preferred. The thixotropic agent has an average particle diameter of usually from 0.005 to 10 μm, preferably from 0.01 to 1 μm, from the viewpoint of anti-sagging ability.

The compounding amount of the thixotropic agent of the component (F) is in the range of 3 to 10 parts by weight based on the amount of the epoxy resin component, that is, 100 parts by weight of the total amount of the components (A) and (B). It is necessary to be. If the amount is less than 3 parts by weight, the composition will not sufficiently exhibit sagging resistance, and if it exceeds 10 parts by weight, the viscosity of the composition will increase and the handleability will deteriorate. Considering the anti-sagging property and the viscosity of the composition, the preferred amount of the component (F) is in the range of 4 to 7 parts by weight.

The epoxy resin composition according to the present invention may contain, if necessary, various conventional additives such as a flexibility-imparting agent, a flame retardant, a fire-extinguishing agent, as long as the object of the present invention is not impaired. A foaming agent, a surfactant, a coloring agent and the like can be added. The method for preparing this composition is not particularly limited, and the components (A), (B), (C), and (D)
It can be prepared by homogeneously mixing the components, the component (E), the component (F), and various additives used as desired at predetermined ratios.

The coating film for coil coating of the present invention comprises a cured product of the epoxy resin composition thus prepared, and can be formed, for example, as follows. That is, the epoxy resin composition according to the present invention is impregnated into a rotor coil of a motor for a power tool or the like with an epoxy resin composition for coil impregnation or the like, and the entire coil is coated thereon using a dispenser or the like. Is applied and cured by heating to form a desired coating film. The application of the epoxy resin composition according to the present invention may be performed before or after the epoxy resin composition for coil impregnation is cured by heating. The type of the epoxy resin composition for coil impregnation and the like are not particularly limited, but from the viewpoint of ease of handling and adhesiveness with the epoxy resin composition for coil coating according to the present invention, the epoxy resin composition and the Similar ones, for example, dicyandiamide-curable epoxy resin compositions are preferred. On the other hand, an acid anhydride-curable two-part epoxy resin composition conventionally used as a liquid epoxy resin composition for coil impregnation has excellent coil impregnation, but has a short pot life and is two-part. Therefore, there is a problem that the adhesiveness with the epoxy resin composition for coil coating according to the present invention is not sufficient. By using an epoxy resin composition comprising a bisphenol-type epoxy resin, dicyandiamide, a urea compound, or the like as the coil resin epoxy resin composition, the coil resin epoxy resin composition and the coil coating epoxy resin composition according to the present invention are used. Can be applied and cured in the same process, and the working process can be simplified.

[0021]

The epoxy resin composition used for forming the coating film for coil coating according to the present invention has appropriate thixotropic properties, fast curing properties, and storage stability. It can be applied and used so as to cover the entire coil. The formed coating film has excellent adhesiveness to the coil and excellent thermal shock resistance, and does not fall off even if a foreign object collides during rotation of the rotor coil. It is suitable for preventing damage.

[0022]

Next, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples. The composition and the cured product (150 ° C., 1
The physical properties of (curing under the conditions of time) were evaluated by the following methods.

(1) Viscosity Measured at 25 ° C. using a rotational viscometer in accordance with JIS K 6838 and JIS K 7117, and evaluated according to the following criteria in consideration of workability. ：: 100 poise or more and less than 3000 poise ×: less than 100 poise and 3000 poise or more (2) Heat resistance A cured sample (15 mm × 5 mm × 5 mm) is subjected to a thermomechanical measurement (TMA) device 4010 manufactured by Seiko Denshi Kogyo Co., Ltd. from room temperature to 250 While the temperature was raised to 5 ° C. at a rate of 5 ° C./min, the coefficient of linear expansion at each temperature was determined. Those having a glass transition temperature of 120 ° C. or higher have good heat resistance. ：: 120 ° C. or more Δ: 100 to less than 120 ° C. ×: less than 100 ° C. (3) Adhesion 100 mm × 25 mm according to JIS K 6850
A sample composition was applied to a × 1.6 mm mild steel sheet so as to have a single overlap of 12.5 mm, and a mild steel sheet of the same dimensions was pressed thereon, cured at 150 ° C. for 1 hour, and then at room temperature. It was left in an atmosphere, and the tensile shear adhesive strength was measured in a normal temperature atmosphere, and evaluated according to the following criteria. Good: Tensile shear adhesive strength is 2 kgf / mm ² or more. (4) Curability According to JIS C 2105, 0.4 cc of a composition is placed on a hot plate at 150 ° C., and the time until gelation is measured. Was evaluated according to the following criteria. Good: less than 150 seconds for gelation time (5) Storage stability The initial viscosity and the viscosity of the composition after storage at 25 ° C. for 30 days were measured, and determined according to the following criteria. Its value is the initial value 2
If it is less than twice, the storage stability is good. ：: Less than twice the initial value ×: More than twice the initial value (6) Thixotropic 3 ゜ × R using an EHD type viscometer manufactured by Tokyo Keiki Co., Ltd.
With 14 cones, 0.5 rpm (η ₁ ) and 2.5 rpm
The viscosity after 5 minutes at 25 ° C. of rpm (η ₂ ) was determined,
The value obtained by dividing calculated in viscosity of 0.5 rpm (eta ₁₎ the viscosity of 2.5rpm (η _2), and evaluated according to the following criteria. ：: η ₁ / η ₂ is 1.4 or more ×: η ₁ / η ₂ is less than 1.4

The specific contents of each component used are shown below. (1) Bisphenol A type epoxy resin “Epicoat 82” manufactured by Yuka Shell Epoxy
8 ", epoxy equivalent 187 (2) Urethane-modified epoxy resin capable of forming chelate Asahi Denka Kogyo Co., Ltd., trade name" ADEKA EPU-78-11 "(3) Dicyandiamide Yuka Shell Epoxy Co., Ltd., trade name" DICY # 15 ",
Average particle size: 7 to 10 μm (4) Methyltetrahydrophthalic anhydride manufactured by Shin Nippon Rika Co., Ltd., trade name “Licacid MT-500” (5) Methylene diphenylbismethylurea ACI Japan Co., Ltd., trade name “Omicure” 52 "(6) Calcium carbonate manufactured by Bihoku Powder Chemical Industry Co., Ltd., trade name" Softon 1800 ", average particle size 1.25 [mu] m (7) Fine particle silica manufactured by Nippon Aerosil Co., Ltd., trade name" Aerosil R-20 "
2 ", average particle size 0.014 μm

Examples 1 to 5, Comparative Examples 1 to 4 Epoxy resin compositions having the compositions shown in Tables 1 and 2 were prepared, and their physical properties were evaluated, as well as the physical properties of cured products. The results are shown in Tables 1 and 2.

[0026]

[Table 1]

[0027]

[Table 2]

Claims (3)

[Claims] 1. A bisphenol type epoxy resin (A)
An epoxy resin component comprising 0 to 100% by weight and (B) 0 to 50% by weight of a urethane-modified epoxy resin capable of forming a chelate, and (C) 3 to 15 parts by weight of a latent curing agent per 100 parts by weight thereof; (D) curing accelerator 0.5 to 10
Parts by weight, (E) 1 to 200 parts by weight of an inorganic filler and (F)
A coil coating film comprising a cured product of a composition containing 3 to 10 parts by weight of a thixotropic agent. 2. A coating film for coil coating, wherein the curing accelerator of the component (D) is at least one selected from toluenebisdimethylurea and methylenediphenylbisdimethylurea. 3. The coating film for coil coating according to claim 1, wherein the inorganic filler as the component (E) is calcium carbonate.