JP2613725B2 - Manufacturing method of surface coated electrical steel sheet for bonding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a surface-coated electromagnetic steel sheet for bonding by pressing and heating after punching or shearing.

[0002]

2. Description of the Related Art Generally, when a non-oriented electrical steel sheet is used for an iron core of an electric device such as a motor or a transformer,
After forming an insulating film on the steel sheet surface in advance on the steel sheet prepared through a predetermined process, continuously punching or shearing, laminating, further welding, caulking, fixing with an adhesive, and forming an iron core Things.

[0003] However, the method of fixing by caulking or welding has the problems that the insulating properties between the steel sheets are reduced, and the magnetic properties are deteriorated by mechanically or thermally introduced strain. Further, in the method of fixing with an adhesive, it is necessary to apply the adhesive to each piece of small iron, and therefore, there is a problem that a large amount of time and labor is required, resulting in poor work efficiency.

[0004] Therefore, an insulating film exhibiting adhesiveness by pressurizing and heating is coated and dried in advance at the steel plate stage, punched or sheared, laminated, and then fixed by pressing and heating to form an iron core. Technology has been proposed. As such an iron core manufacturing technique, Japanese Patent Publication No. 55-9815 discloses a treatment liquid obtained by adding a water-soluble styrene-maleic acid copolymer to an acrylic resin emulsion, and forming an incompletely baked adhesive film on the steel sheet surface. Forming techniques have been proposed.

[0005]

[Problems to be solved by the invention]
The technique disclosed in Japanese Patent No. 9815 has a problem that a strong odor is generated at the time of coating and drying. That is, according to Japanese Patent Publication No. 55-9815, when an adhesive film in an incompletely baked state is formed on the surface of a steel sheet with a treatment liquid obtained by adding a water-soluble styrene-maleic acid copolymer to an acrylic resin emulsion, styrene- Ammonia and a water-soluble amine are used to make the maleic acid copolymer water-soluble. Thereafter, the ammonia is dispersed and scattered during heating and drying. Therefore, when drying, a strong ammonia smell is generated, and there is a problem on the hygiene of workers.

Moreover, the processing solution disclosed in Japanese Patent Publication No. 55-9815 has problems in solution stability and film stability.
That is, when the styrene-maleic acid copolymer is made water-soluble, it is necessary to use ammonia, a water-soluble amine, or the like, but by using these, the treatment liquid becomes alkaline. However, the acrylic resin emulsion is unstable to alkalinity, and the treatment liquid increases in viscosity with time or separates and aggregates, making it difficult to apply. Therefore, it is necessary to apply and dry the prepared processing solution promptly, and when the coating operation is delayed, it is difficult to apply, and the coating workability is poor.

Further, there are various steps such as slitting and punching between the application of the adhesive insulating film to the electromagnetic steel sheet and the production of the laminated iron core. In many cases, if the stability of the film is poor, the curing reaction proceeds, and finally there is a problem that the adhesive ability is lost and the production of the iron core becomes impossible.

The present invention has been made as a result of intensive studies on the above-mentioned problems, and by suppressing the use of ammonia and a water-soluble amine, the odor during coating and drying is suppressed. An object of the present invention is to provide a method for producing a surface-coated steel sheet having extremely high stability and film stability, capable of long-term storage, and maintaining excellent adhesive strength. By carrying out the method of the present invention, no odor is generated during the coating and drying of the adhesive film, the treatment liquid is extremely stable, the coating workability is good, and after the coating and drying, the film has good stability and can be stored for a long time. It is possible to manufacture a surface coated steel sheet for bonding having excellent bonding ability by applying pressure and heating.

[0009]

Means of the present invention for solving the above problems are as follows. In other words, the production of a surface-coated electrical steel sheet for adhesion characterized by uniformly applying a mixture mainly composed of an acrylic modified epoxy resin emulsion preliminarily blended with a latent curing agent onto a steel sheet surface and baking it in an incomplete state. Is the way.

Hereinafter, the contents of the present invention will be described in detail. The acrylic modified epoxy resin emulsion pre-blended with a latent curing agent used in the present invention is an epoxy resin, after blending a latent curing agent, and then chemically reacting the acrylic resin to form an epoxy resin and a latent curing agent. After coating around the mixture of the above, an emulsion was obtained.

The term "epoxy resin" as used herein refers to a resin which is liquid at room temperature, preferably solid, and has two or more epoxy groups in a monomer, and specifically includes bisphenol A type, bisphenol F type, and bisphenol AD. Type,
There are naphthalene type, phenol novolak type, orthocresol novolak type, glycidyl ester type, alicyclic type and the like.

A latent curing agent to be blended with an epoxy resin is a curing agent which is used when a normal epoxy resin curing agent has a pot life of only several hours to several days after the curing reaction proceeds immediately after mixing. On the other hand, a latent curing agent is one that is stable during mixing with an epoxy resin for several months and has a pot life of several months. In order to cure the epoxy resin using such a latent curing agent, the curing reaction is started by physically or chemically stimulating the mixed system such as heating, humidification, and pressurization. Usually, in order to cure, it is common to heat to a predetermined temperature.

Specific latent curing agents include dicyandiamide, melamine, organic acid dihydrazide, amine imide, ketamine, tertiary amine salts, imidazole salts, boron trifluoride amine salts, microcapsule curing agents, molecular sieve curing Agents and the like.

The term "microcapsule type curing agent" as used herein means a normal curing agent encapsulated in a microcapsule formed of casein or the like, and the epoxy resin and the curing agent are broken by breaking the microcapsule by heating or pressing. Are mixed and the curing reaction proceeds.

Further, a molecular sieve type curing agent is a substance in which a curing agent is adsorbed on the surface of an adsorptive compound such as a molecular sieve, and by heating and humidifying, adsorbed molecules are released, and the curing reaction is promptly performed. Let it progress.

In the present invention, although not generally classified as a latent curing agent, a mixed system with an epoxy resin can be stored for a long time at room temperature, and the curing reaction proceeds by heating. For this reason, block isocyanates, melamine resins, urea resins, resole-type phenol resins, acrylic resins, nylons, xylene resins and the like can also be used.

In the present invention, it is not always necessary for the reaction to be completely unreacted, and the curing reaction may proceed to some extent as long as the incompletely reacted state is chemically stabilized.

Further, in the present invention, an acrylic resin is modified into a mixed system of the epoxy resin and the epoxy resin curing agent. The term "modification" used herein means that an acrylic resin is chemically bonded to the surface of a mixture of an epoxy resin and an epoxy resin curing agent. As the acrylic resin to be subjected to such modification, one or two or more of methacrylic acid, methacrylic acid ester, acrylic acid, acrylic acid ester, styrene, vinyl acetate and the like are polymerized or copolymerized. Thereafter, the above compound is emulsified. There is no particular limitation on the method of emulsification, and an emulsion obtained by a normal emulsification method or a self-dispersion type acrylic resin may be used.

The processing solution of the present invention may contain various additives such as a film-forming aid, a coloring pigment, a glass forming agent, a dispersibility improver, and an antifoaming agent, in addition to the above compounds.

The mixing ratio of the epoxy resin and the latent epoxy resin curing agent greatly varies depending on the type of the epoxy resin and the type of the curing agent. 10 parts by weight is suitable, and the amount of the denatured acrylic resin is suitably 0.05 to 2 parts by weight based on 1 part by weight of the epoxy resin. Within such a composition range, a treatment liquid having good stability of the liquid and excellent in various film properties after coating and drying can be obtained.

Next, the method of applying and drying the treatment liquid is as follows.
First, a predetermined amount of a treatment liquid is applied to the surface of a steel sheet with a roll coater or the like, and is dried at room temperature or under heat. However, in the present invention, it is essential to bake incompletely, and usually, 100 ° C or more.
It is industrially preferable to dry at a furnace temperature of 300 ° C. for 10 seconds to 90 seconds. The incompletely baked state mentioned here means that there is no stickiness or blocking, and the material is sheared.
After lamination, it is a state of bonding by heating under pressure.

[0022] Next an insulating layer weight formed on the surface of the steel sheet is not particularly limited, sufficient adhesion can not be obtained is less than 4g / m ² ~12g / m ² range is appropriate and 4g / m ^2, whereas If it exceeds 12 g / m ² , the space factor is inferior, which is not preferable.

In the present invention, since the styrene-maleic acid copolymer is not used and the epoxy resin is used,
No intense odor is generated during coating and drying, and an extremely favorable working environment can be obtained. Furthermore, when a conventional epoxy resin is used, the potable life of the processing liquid is short due to the progress of the curing reaction from the time of mixing the curing agent,
Once mixed, the liquid must be used up at most for one day, usually several hours, which has been a major obstacle in the actual production process. Is greatly prolonged, and furthermore, the stability of the treatment liquid is greatly improved by the acryl modification, and extremely good coating workability can be obtained.

[0024] Further, due to the acryl modification, the film does not change over time even in an incompletely baked state, and the adhesive strength is not reduced, and the film is less likely to cause blocking or the like. Although the reason for this has not been elucidated in detail, a chemically stable acrylic resin component exists on the film surface or between each unreacted epoxy resin and the latent curing agent mixture, and forms one type of barrier layer. Therefore, it is presumed that it functions to make it less affected by external factors such as outside air and light.

[0025]

Next, examples of the present invention and comparative examples will be described.
Electromagnetic steel sheet (sheet thickness 0.5 mm, surface roughness Ra 0.20 μm)
Each of the following treatment liquids was applied to the surface of, squeezed by a rubber roll, and baked in a drying oven set at 150 ° C. for 60 seconds to make the adhesion amount 7 g / m ² .

Example 1 100 parts by weight of water 40 parts by weight of an acrylic modified epoxy resin emulsion mixed with a 20% latent curing agent

Example 2 Water 100 parts by weight 20% latent curing agent-mixed acrylic modified epoxy resin emulsion 40 parts by weight Methyl ethyl ketone 5 parts by weight

Comparative Example 1 Water 100 parts by weight 50% acrylic resin emulsion 40 parts by weight Styrene-maleic acid copolymer 20 parts by weight

Comparative Example 2 Water 100 parts by weight 50% acrylic resin emulsion 40 parts by weight 50% epoxy resin emulsion 40 parts by weight Amine epoxy curing agent 4 parts by weight

Table 1 shows the results of the above Examples and Comparative Examples.

[0031]

[Table 1]

As is clear from Table 1, according to the present example, the adhesive has the same excellent adhesive strength as before, has no ammonia smell at the time of coating and drying, has good liquid stability, and has good An electromagnetic steel sheet having an adhesive electric insulating film which did not change over time was obtained.

[0033]

As described in detail above, according to the method of the present invention, the odor and the stability of the liquid during coating and drying are extremely good.
An electromagnetic steel sheet having an electrical insulating film for adhesion excellent in various film properties is obtained, since the film after application and drying hardly undergoes aging or blocking.

Claims (1)

(57) [Claims] 1. An adhesive-coated surface-coating electromagnetic coating, characterized in that a mixture mainly composed of an acrylic modified epoxy resin emulsion containing a latent curing agent in advance is uniformly applied to the surface of a steel sheet and baked in an incomplete state. Steel plate manufacturing method.