JP2574698B2 - Manufacturing method of laminated iron core - Google Patents

Description

The present invention relates to a method for manufacturing a laminated iron core. More specifically, the present invention relates to a method for manufacturing a laminated iron core used for electric equipment and the like.

<Conventional technology> Conventionally, iron cores used for electric appliances and the like first apply an insulating coating for reducing eddy current to an electromagnetic steel sheet,
A so-called unitary iron core is produced by punching or cutting the same, a large number of them are stacked, and then they are fixed by welding or an adhesive.

However, the method of fixing by welding has various problems such that the edge portion of the iron core is short-circuited, the insulating property is reduced, and the magnetic properties are deteriorated by thermal strain.
Also, in the method of fixing with an adhesive, it is necessary to apply an adhesive to each unit iron core, so that workability is extremely poor, and furthermore, since an insulating coating is applied, the adhesive strength is not sufficient. There were various problems such as not having.

Therefore, in recent years, a method of manufacturing a laminated iron core has been proposed in which an insulating coating film that develops an adhesive force by heating and pressing is applied to an electromagnetic steel sheet, and thus the welding or adhesive application step is omitted.

That is, an insulating coating composition that develops an adhesive force by heating and pressing to an electromagnetic steel sheet is applied and dried, and the obtained coated steel sheet is punched or cut, and a number of the obtained unit iron cores are stacked. Finally, this is a manufacturing method in which the unit iron cores are bonded by heating and pressure bonding.

<Problems to be solved by the invention> However, in this type of technical field, the manufacture of a coated steel sheet itself is performed by a steel sheet manufacturer, and the manufacture of a laminated iron core from the coated steel sheet is performed by an iron core manufacturer. There is a tendency for division of labor to be performed.

Therefore, after applying an insulating coating to the electromagnetic steel sheet and storing it for a long time, a laminated iron core will be manufactured.Therefore, during the storage period, rust occurs on the steel sheet, or a coated steel sheet is stacked, There are various problems, such as blocking when storing in a wound state.

In view of such circumstances, the present inventors have conducted intensive studies to solve the above-mentioned various problems, and as a result, it has been found that rusting and blocking hardly occur during storage of a coated steel sheet, and that the laminated iron having excellent adhesive strength by heat compression bonding. The present inventors have found a method for manufacturing a core and have reached the present invention.

<Means for Solving the Problems> That is, the present invention provides: (I) a thermoplastic acrylic resin emulsion having a glass transition temperature of 60 ° C. or higher; (B) an epoxy resin emulsion; And (D) a solubility in water (at 20 ° C.) of 20 g / 100 cc or less, and a solubility in water (at 20 ° C.) of 0.5 g / 100cc
A water-based heat-bonding insulating material containing the above-mentioned film-forming auxiliary as a main component, and wherein the resin solid content weight ratio of the component (A) and the component (B) is (70/30 to 95/5). A step of applying a coating composition; (II) a step of drying a coating film; (III) a step of forming a unit core having a desired shape from the obtained coated steel sheet; and (IV) stacking the unit core. And (V) a step of heating and pressurizing the stacked products, and a method of manufacturing a laminated iron core.

 Hereinafter, the present invention will be described in more detail.

First, the water-based heat-bonding insulating coating composition (hereinafter simply referred to as coating composition) used in the present invention will be described.

The thermoplastic acrylic resin emulsion as the component (A) is composed of an alkyl ester monomer of acrylic acid having 1 to 8 carbon atoms, an alkyl ester monomer of methacrylic acid having 1 to 8 carbon atoms, a styrene monomer or a mixture of these monomers. If necessary, a monomer mixture containing about 10 mol% or less of a functional group-containing monomer such as acrylic acid, methacrylic acid, or hydroxyethyl methacrylate is mixed with a glass transition temperature (hereinafter, Tg) of the obtained acrylic resin.
Are appropriately combined so as to be 60 ° C. or higher, and obtained by a usual emulsion polymerization method.

If the Tg is lower than the specific range, the resulting coating film remains tacky, for example, a blocking phenomenon is likely to occur when, for example, coated steel sheets are stacked, and the coating film may be damaged due to the phenomenon. So you should avoid it. In addition,
The upper limit of Tg varies depending on the type and amount of the film forming aid,
Usually, 150 ° C. or lower is preferable.

Next, the epoxy resin emulsion, which is the component (B),
It is blended to improve the adhesion of the coating film to the steel material, the rust-prevention force, and the like, and to strongly bond the unit iron cores when the laminated iron core is heated and pressed.

The epoxy resin referred to here is a liquid or solid at room temperature containing two or more epoxy groups in one molecule. Specifically, it is obtained by reacting a polyhydric alcohol or a polyhydric phenol with halohydrin, and includes bisphenol A type, halogenated bisphenol A type, novolak type, polyglycol type, bisphenol F type, epoxidized oil and the like. No.

The epoxy resin suitably has an epoxy equivalent of about 200 to 1,000. It is desirable to use a solid at room temperature in consideration of blocking resistance and the like. Specific commercial products include Epikote # 828, # 1001, # 1004, # 1007
(Trade name of Yuka Shell Epoxy Co., Ltd.); DER511-A8
0, 732 (trade names of Dow Chemical Co., Ltd.); YD-011, 00
1, 001Z, 012, 014; ST-5080, 5100; YDCN-701, 702, 7
03, 704; YDPN-638 (trade names, etc., manufactured by Toto Kasei Co., Ltd.) are typical examples.

The epoxy resin emulsion is produced by subjecting these epoxy resins to a usual forced emulsification method in the presence of an emulsifier. The emulsifier used is desirably a polyoxyethylene alkylphenol ether-based nonionic surfactant, a polyoxyethylene polyoxypropylene block polyether, or an adduct thereof with a diisocyanate compound, alone or as a blend.

Further, the amine-based epoxy resin curing agent, which is the component (C), does not cause gelation, thickening, etc. even when the coating composition is stored at room temperature, and when heated to about 200 to 500 ° C., Those which undergo a crosslinking reaction with the component (B) or cause a self-crosslinking reaction of the component (B) are suitable for use.

Examples of the curing agent that satisfies such conditions include dicyandiamide, amidoethylpiperazine, piperidine, a heterocyclic amine (for example, “Epomate” (trade name of Ajinomoto Co.)), hexamethylenetetramine, triethylamine, triethanolamine, Typical examples include 4'-methylenedianiline, triethylenediamine, imidazoles, imidazoline derivatives and the like.

The component (D), a film-forming aid, plasticizes the resin particles of the component (A) and the component (B) when applying the coating composition to form a coating film, and promotes fusion between the particles. Further, it is blended in order to form the coating film into a smooth coating film without repelling or the like.

By the way, it is known to mix various film-forming aids in an emulsion paint. However, the film-forming aid used in the present invention has a solubility of the film-forming aid in water (at 20 ° C.).
Is less than 20 g / 100 cc and the solubility of water in the film-forming auxiliary (at 20 ° C.) satisfies the condition of 0.5 g / 100 cc or more. did.

If a film-forming aid having a water solubility higher than the above range is used, the resulting coating film tends to have coating defects such as cissing, resulting in rust. If the solubility of water is smaller than the above range, the compatibility with other components is poor, the viscosity tends to be increased, the separation is apt to occur, and the storage stability is poor.

Further, it is particularly preferable that the film-forming auxiliary has a boiling point of 100 ° C. or higher.

Specific examples of such a film-forming aid include 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, butyl carbitol acetate, octylene glycol,
Representative examples include 3-methoxybutyl acetate, 2-ethylhexyl acetate, isobutyl alcohol, n-butyl alcohol, amyl alcohol, benzyl alcohol, pentyl alcohol, and mixtures thereof.

The coating composition used in the present invention comprises the above (A) to
A color pigment, an extender, an anti-corrosion pigment or an antifoaming agent containing a component (D) as a main component and further having an insulating property, if necessary;
It is a mixture of various additives such as a surface conditioner, a thickener, a pigment dispersant, and a preservative.

In the coating composition, the weight ratio of the resin solid components (A) and (B) is suitably (70/30 to 95/5).

When the component (B) is less than the above range, the crosslinking density is low and the cohesive force is small, so that the adhesive force to the electromagnetic steel sheet is weak. Conversely, when the component (B) is too large, the component (A) is relatively low. As a result, the bonding strength between the iron cores cannot be obtained by heating and pressing after stacking the unit iron cores.

The total resin solid content of the components (A) and (B) is blended at a ratio of about 20 to 50% by weight in the total coating composition in consideration of the coating workability and the original function as a coating film. It is appropriate to do.

Further, the compounding amount of the component (C) is such that the amino group in the component (C) is 0.8 to 1.2 with respect to 1 equivalent of the epoxy group in the component (B).
It is appropriate to mix them in equivalent amounts. In such a composition range, the crosslinking reaction sufficiently occurs by heating, and the original adhesive strength can be obtained.

The amount of the component (D) varies depending on the type and concentration of the resin, but is usually 1 to 30% by weight based on the total resin solid content of the components (A) and (B). It functions as an original film-forming aid without impairing the performance of the coating film.

Next, the method for manufacturing a laminated iron core of the present invention will be described in detail.

In the first application step (I), the coating composition is first applied to the surface of an electromagnetic steel sheet by means of a spray, a roll coater or the like so as to have a dry film thickness of about 4 to 10 μm.

Next, in the (II) coating film drying step, drying is performed at normal temperature, preferably by forced heating and drying under normal pressure.

The forced drying conditions vary depending on the type of each component of the coating composition, but it is generally appropriate to dry at a temperature of 100 to 250 ° C. for about 30 seconds to 20 minutes.

When dried, the components (B) and (C) may be completely cross-linked or partially cross-linked. The steel sheets coated in this way are wound, for example, into coils or stacked.

Next, the obtained coated steel sheet is subjected to a step (III).
That is, a desired unit iron core is manufactured by continuous punching or cutting by an electric equipment manufacturer or the like.

A predetermined number of the unit iron cores are further stacked (fourth step). Finally, the stacked products are heated and processed (step V) so that the unit iron cores are adhered to each other to produce a desired laminated iron core.

The bonding conditions in the step (V) differ depending on the size of the iron core and the like, but are usually 5 to 2000 kg / cm ^{2 at} a pressure and 200 to 300 ° C.
It is appropriate to heat-press for 10 to 200 seconds under the above conditions.
By heating and pressing in this manner, the component (A), which is a constituent component of the coating composition, is in a molten state, and the coating films of both layers are mixed at the interface, and as a result, the unit iron cores are firmly adhered to each other. Thus, a laminated iron core having a strong adhesive force can be obtained. By the way, at the time of thermocompression bonding, the components (B) and (C) also complete the crosslinking reaction and exert a reinforcing function between the unit iron cores.

<Effect of the Invention> In the present invention, a specific water-based heat-bonding insulating coating composition is used. Therefore, by simply applying to the electromagnetic steel sheet, a smooth coating film without repelling or the like can be obtained, and the obtained coating film has excellent corrosion resistance, water resistance, etc., and hardly causes blocking and the like of conventional coating materials. It has enough of the functions provided in Further, at any necessary time (in situ), the coated electromagnetic steel sheet is processed to form a unitary iron core having a desired shape, which is stacked, and then heated and pressed to develop a strong adhesive force. is there.

Therefore, unlike the conventional method, a welding step or an adhesive application step is not required, so that labor saving and cost reduction of the steps can be achieved, and the manufacturing method of the laminated iron core of the present invention has a very large practical value.

Hereinafter, the present invention will be described in more detail with reference to Examples.
In the examples, "parts" and "%" are shown on a weight basis.

[Thermoplastic Acrylic Resin Emulsion (A)] Emulsions (i) to (iv) were prepared from a monomer mixture having the composition shown in Table 1 in water by a usual emulsion polymerization method.

[Epoxy resin emulsion (B)] A commercially available epoxy resin emulsion shown in Table 2 was used.

[Water-based thermal bonding type insulating coating composition] The components having the formulations shown in Table 3 were stirred and mixed to prepare a coating composition. The numerical values in the table are "parts".

In Table 3, the solubility of component (D) in water (at 20 ° C.) (g / 100 cc) and the solubility of water in component (D) (20
(In ° C) [g / 100cc] is as follows.

Solubility in water Solubility in water Note 1) 4.2 11.7 Note 2) 6.5 3.7 Note 3) ∞ ∞ Note 4) 0.1>0.1> Note 5) 18 18 Note 6) 23 6.5 Examples 1 to 6 and Comparative examples 1 to 6 The coating composition shown in Table 3 was applied to the surface of an electromagnetic steel sheet (sheet thickness 0.5 mm, sheet width 960 mm) by roll coating so as to have a dry film thickness of about 5 μm, dried at 200 ° C. for 60 seconds, and wound around a coil.

The coated steel sheet thus obtained was punched into an E core with a steel die. Laminate E core, pressure 10kg / c
Hot pressing was performed for 70 seconds under the conditions of m ² and a temperature of 200 ° C. to produce a laminated iron core.

The coated steel sheet was tested for suitability during storage and adhesion when used as a laminated iron core by examining the coating film appearance, blocking resistance, salt spray resistance (corrosion resistance), and adhesion as follows. , And the results are shown in the lower column of Table 3.

Coating film appearance: The obtained coating film was visually judged. In addition, the case where there was no repelling, bubbles, crushing, streaks, clouding, etc., was smooth; the case where there was a coating film defect, such as repelling, was regarded as poor.

Blocking resistance: The coated surfaces of the coated steel sheet cut to 40 x 40 mm are overlapped, and a cushioning material and an aluminum plate are attached to the outside, and a pressure (10 kg / cm ² ) is applied with a vice,
After standing at 24 ° C. for 24 hours, the presence or absence of blocking was examined. In addition,
Good without blocking; poor with blocking.

Salt spray resistance: Tested based on JIS K5400. In addition, the case where there was no abnormality in the coating film was good; the case where spot rust and blisters occurred were evaluated as poor.

Adhesive strength (I): Coated steel sheet cut to 20 x 50 mm (the coated steel sheet wound on a coil was left at room temperature for one month) so that the overlap between the coated surfaces was 20 x 10 mm, and the pressure was applied. 10kg
At 70 ° C. for 70 seconds at 200 ° C./cm ² .

About the obtained adhesive, "Autograph S" manufactured by Shimadzu Corporation
-2000C ".

Adhesive strength (II): After the coated steel sheet was aged at 80 ° C. for 48 hours, it was heated and pressed in the same manner as in the method of the adhesive strength (I).
The shear adhesion was measured.

As is clear from Table 3, the coated electromagnetic steel sheet coated with the water-based heat-bonding insulating coating composition used in the present invention is:
The coating film appearance, blocking resistance, and corrosion resistance were good, and the adhesive strength after thermocompression bonding was excellent, and an excellent laminated iron core was obtained.

On the other hand, the comparative example using a thermoplastic acrylic resin emulsion having a Tg of less than 60 ° C. had poor blocking resistance.

In addition, the solubility in water is 20 g / 100 cc as a film-forming aid.
In Comparative Examples 2 and 6 using more than the film-forming aid, repelling occurred in the coating film, and spot rust occurred in a salt spray test.

In Comparative Example 3 using a film-forming aid having a water solubility of less than 0.5 g / 100 cc as a film-forming aid, the composition was thickened and separated during storage, and spot rust occurred in a salt spray test. Was.

In Comparative Example 4 in which the component (B) was excessive as the resin solid content ratio of the components (A) and (B), the adhesive strength after aging was significantly reduced.

Comparative Example 5, which did not contain the component (B), had poor adhesion.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Hideo Kobayashi 1 Kawasaki-cho, Chiba-shi, Chiba Kawasaki Steel Corporation In-house Research & Development Division (72) Inventor Tomoyuki Ichi 1 Kawasaki-cho, Chiba-shi, Chiba Kawasaki Steel In-house Technology Research Division (72) Inventor Yoshiaki Iida 1 Kawasaki-cho, Chiba City, Chiba Prefecture Kawasaki Steel Corporation In-company Technology Research Division (72) Inventor Katsio Sadayo 1 Kawasaki-machi Chiba City, Chiba Prefecture Kawasaki Steel Corporation Technology Research Division

Claims (1)

(57) [Claims] (I) A surface of a magnetic steel sheet, (A) a thermoplastic acrylic resin emulsion having a glass transition temperature of 60 ° C. or higher, (B) an epoxy resin emulsion, (C) an amine which reacts with the component (B) by heating. Epoxy resin curing agent, and (D) solubility in water (at 20 ° C.) is 20 g / 100 cc or less, and solubility in water (at 20 ° C.) of 0.5 g / 100 cc
A water-based heat-bonding insulating material containing the above-mentioned film-forming auxiliary as a main component, and wherein the resin solid content weight ratio of the component (A) and the component (B) is (70/30 to 95/5). A step of applying a coating composition; (II) a step of drying a coating film; (III) a step of forming a unit core having a desired shape from the obtained coated steel sheet; and (IV) stacking the unit core. And (V) heating and pressing the stacked products.