JPS59102479A - Formation of resin insulation film for electrical iron sheet - Google Patents

Abstract

PURPOSE:To obtain an excellent insulation film having good blanking quality without generating malodor during the work by coating a treating liquid prepd. by compounding a specific amt. of a water soluble melamine resin with a PE resin dispersion contg. a specific ratio of a carboxylic group on the surface of an electrical iron sheet and drying the same by heating. CONSTITUTION:A carboxylated PE resin dispersion contg. 3-20mol% carboxyl group is compounded therein with 10-30pts.wt. a water soluble melamine resin in terms of a solid content basing on 100pts.wt. said dispersion in terms of a solid content, thereby preparing a water soluble resin treating liquid. Such treating liquid is coated on the surface of an electrical iron sheet and is dried by heating, whereby a resin insulation film is formed. Said treating liquid is coated preferably at 0.5-8mu sticking thickness of the film after the drying by heating, and the drying is accomplished preferably in a temp. range of 150-200 deg.C. The film is thus formed at a relatively low temp. without generating offensive smell in the stage of coating and drying.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides advantages of resin-based insulation coatings for electric iron plates, which do not generate bad odor during shadow lines and are also excellent in film form FM and later punching workability. The purpose of this paper is to propose a new formation method.

For iron cores for electrical equipment such as motors, generators, and transformers, an insulating film is first formed on the surface of a steel plate to prevent eddy currents, then punched into a predetermined shape, and then a large number of them are laminated and the entire side surface is covered. Can be assembled by TIG welding or bolting.

Electrical iron plates used as iron cores for motors and the like are always punched into a predetermined shape, so they are strongly required to have excellent punching properties.

It is known that the punchability of this electric iron plate is greatly influenced by the properties of the insulating film coated on its surface, and can be greatly improved by the use of organic resins. For example, the punchability of electric iron plates coated with inorganic coatings such as phosphates and chromates is about 100,000 punches per polishing of the mold, while the number of punches per polishing of the mold is about 7'. (In the case of a chromate-resin coating, good punchability of about 1.5 million times can be obtained.) Known examples include phenol, epoxy, polyester, acrylic, and styrene.

Conventionally, organic films were formed by applying and baking a resin treatment solution using an organic solvent as a solvent, but since the organic solvent constantly evaporates, it has a strong odor and poses health and safety problems, especially when baked. In some cases, a large amount of the solvent gasifies, so a hot air oven type oven is required for baking, and moreover, sufficient consideration must be given to the treatment of exhaust gas.

In this regard, water-bath terive or water emulsion type resin treatment solutions that do not contain any organic solvent have been proposed, but the coatings produced using these solutions are not satisfactory in terms of hardness, water resistance, and solvent resistance. No results were obtained.

This invention advantageously solves the above-mentioned problems.The application and baking of the treatment liquid does not generate any odor during operation, and furthermore, it has excellent punching workability after film formation, and furthermore, it has excellent interlayer resistance and The purpose of the present invention is to propose an advantageous method for forming an insulating coating for electric iron plates that is comparable to conventional coatings in terms of adhesion, corrosion resistance, oil resistance, solvent resistance, hardness, etc.

As a result of intensive research aimed at achieving the above object, the inventors discovered that an aqueous resin treatment solution prepared by adding melamine resin to a carboxylated polyethylene resin dispersion is advantageously suitable as a coating solution. It was discovered that when a processing liquid was used, baking could be completed at a relatively low temperature compared to the conventional method, and this invention was developed based on this new knowledge.

S'lx Wachiko's invention is that the surface of an electric iron plate is coated with a carboxylated polyethylene resin dispersion containing 3 to 20 mol% of carboxyl groups, with a solid content of 1Ω.
00 parts by weight of water-soluble melamine resin as solid content
The solution to the above problem is to apply an aqueous resin treatment liquid mixed in a proportion of 0 to 80 parts by weight and then heat dry it. The thickness is preferably about 0.5 to 8 .mu.m, and the heat drying temperature is preferably in the range of 150 to 200"O.

This invention will be specifically explained below.

Now, regarding the carboxylated polyethylene resin tispersion, which is an essential component of the treatment liquid in this invention, if the carboxyl group is less than 3 mol%, it is difficult to emulsion polymerize the polyethylene resin, and the adhesion to the iron plate deteriorates. ,
On the other hand, if the amount exceeds 20 mol%, coating properties such as corrosion resistance and water resistance will deteriorate, so 3 to 2
It is necessary to contain carboxyl fund in the range of 0 mol%.

Further, the water-soluble melamine resin used in combination must be blended in a proportion of 10 to 80 parts by weight as a solid content per 100 parts by weight of solids in the polyethylene resin dispersion. This is because if the blending ratio is less than 10 parts by weight, it is difficult to obtain sufficient coating hardness and scratches are likely to occur, whereas if it exceeds 30 parts by weight, the coating becomes brittle and the punching performance deteriorates.

Next, the aqueous resin treatment liquid whose ingredients have been adjusted to the above-mentioned proportions is applied to the surface of the electric iron plate, but the application method is not particularly limited, and may include a roll coater method, a dipping method, etc. Any existing method can be used.

Next, a heat treatment is performed to form a film, and the heating and drying temperature at this time only needs to be about 120"0, which is the board temperature. Therefore, in the temperature range of 150-200"
Processing at a low temperature of about 60 seconds, preferably 180 degrees centigrade, is sufficient. In this regard, when forming a conventional resin coating, it was necessary to bake at a high temperature of about 450 υ in order to fully demonstrate its performance as an insulating coating.

The thickness of the coating after drying varies depending on the grade of the electric iron plate and the use of the electrical equipment, but it is preferably about 0.5 to 8 μm.

Regarding polyethylene resins, for example, ethylene-vinyl acetate emulsions and polyethylene waxes have been known, but these have poor solvent resistance, and when powdered resins are used, they do not have a uniform processing solution. This made uniform application difficult.

・ In this respect, polyethylene dispersions do not have the above-mentioned problems, and since such resin treatment liquids do not use organic solvents but use water as a solvent, they do not emit any odor during application and drying, and can be easily removed. In addition to being easy to handle, it also has the advantage of requiring low drying temperatures.

The use of such a water-soluble polyethylene resin as a component for forming an organic insulating film has never been considered, and this invention is the first attempt to do so.

Next, examples of the present invention will be described together with comparative examples.

Example 1 A carboxylated polyethylene resin dispersion containing t-12 mol% of carboxyl groups, a 1' water-soluble melamine resin, and a total solid weight of 1' water-soluble melamine resin were applied to the surface of an electric iron plate (equivalent to 850) with a plate thickness of 0.5 yt+m. Ratio: 100:
An aqueous resin treatment solution added and blended at a ratio of 15% was applied, and then heated and dried at 180°C for 60 seconds to form an organic film with a thickness of 2.1μm on the surface of the iron plate.
.

Table 1 shows the results of examining the percent properties of the obtained coatings.

Example 2 A carboxylated polyethylene resin dispersion containing 8 mol% of curloxyl groups and a water-soluble melamine resin were each placed on the surface of the same electric iron plate as used in Example 1 at a solid content weight ratio of 100. : Apply an aqueous resin treatment solution added at a ratio of 20%, and then heat at 180°C.
After heating and drying the syllables for 260 seconds, 2.
An organic film with a thickness of 0 μm was formed.

Table 1 also shows the results of examining the properties of the obtained coating.

Comparative Example 1 A treatment solution consisting only of a carboxylated polyethylene resin dispersion containing 12 mol% of carboxyl fund was applied to the surface of the same iron plate as used in the example, and
It was dried at 0.degree. C. for 60 seconds to form an organic film with a thickness of 2.1 .mu.m.

The results of various properties of the obtained coating are also listed in Table 1.

Comparative Example 2 A phenolic solvent-based resin was applied to the surface of the same iron plate as used in the example, and baked at 450°O and SO for seconds to obtain an organic film with a thickness of 2.2 μm. The results of investigating the properties of the obtained coatings are also listed in Table 1.

Of the four experimental examples that were submerged, in the case of Example 1゜2 and Comparative Example 1, no odor was emitted during coating and drying, but in the case of Comparative Example 2, the volatilization of the solvent (.) caused no odor. This significantly worsened the working environment.

・As is clear from the results shown in Table 1, in Comparative Example 1, which did not contain any melamine resin in the aqueous treatment liquid, although no odor was generated during coating formation, the coating had a soft hardness of about 2B. Therefore, it is easily scratched and has poor interlayer resistance, oil resistance, and solvent resistance. --Comparative Example 2 using a universal solvent was inferior in punching workability, and moreover, coating and baking produced odor during work, significantly deteriorating the work environment.

In contrast, in Examples 1 and 2 according to the present invention, no odor was generated at all during application and drying of the treatment liquid, and insulating coatings with excellent coating properties were obtained.

As described above, according to the present invention, it is possible to obtain an insulating coating that satisfies not only punching workability but also other required properties.

Furthermore, since the resin treatment liquid according to the present invention is water-based, unlike conventional ones that use organic solvents, it is easy to handle, does not generate odor during application and drying, and is lower temperature than conventional ones. It is also advantageous in terms of energy saving, since it is possible to form a film in the same manner.

Patent applicant: Kawasaki Steel Corporation

Claims (1)

[Scope of Claims] L A water-soluble melamine resin is added to the surface of an electric iron plate as a solid content of 10% by weight of a carboxylated polyethylene resin dispersion containing 3 to 20% by mole of carboxyl groups in total, based on the solid content ioo parts by weight of the dispersion. A method for forming a resin-based insulating coating for an electric iron plate, which comprises applying an aqueous resin treatment liquid mixed in a proportion of ~30 parts by weight, and then heating and drying. a The coating amount of the aqueous resin treatment liquid is 0.5 to 8 μm″r in film adhesion thickness after heating and drying: a method according to claim 1 & a patent in which the heating and drying temperature is in the range of 150 to 200°C Claims 1 and 2 refer to the method described in 2.