JP2953952B2 - Surface coated electromagnetic steel sheet for heat bonding and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface-coated electromagnetic steel sheet which is used after being punched, sheared, pressed and bonded by applying pressure and heat, and a method for producing the same.

[0002]

2. Description of the Related Art The characteristics required for a surface-coated electromagnetic steel sheet to be bonded by pressing and heating include pressure / heat bonding, blocking resistance, welding, punching, shearing, and the like.
Numerous examples include press workability and corrosion resistance. Numerous studies have been made to satisfy these requirements, and many proposals have been made regarding the coating composition of surface-coated electrical steel sheets for heat bonding. For example, Japanese Patent Publication No. 49-13318 discloses an adhesive magnetic steel sheet having a coating made of a thermoplastic epoxy resin and a benzoguanamine resin.
No. 8998 discloses a mixed resin of a thermoplastic resin and a thermosetting resin (a mixed resin of a phenoxy resin and a methanol-modified melamine resin, a mixed resin of a phenoxy resin and a benzoguanamine resin, a mixed resin of a phenoxy resin, a phenol resin and a melamine resin). JP-A-2-38042 discloses a surface-coated electromagnetic steel sheet having a coating composed of a thermoplastic acrylic resin, a thermosetting epoxy resin, and an epoxy resin curing agent. Have been.

[0003]

However, the surface-coated electromagnetic steel sheet for bonding obtained by the above-described method has good bonding strength at room temperature after bonding under pressure and heat, but does not always have sufficient bonding strength at high temperatures. It couldn't be said.
Alternatively, in order to obtain a sufficient high-temperature adhesive strength, the workability is poor, such as requiring a long bonding time or a heat treatment after the bonding. In particular,
In the coating disclosed in Japanese Patent Publication No. 49-13318,
As is clear from the examples, the adhesive strength at 130 ° C. is 1
8 kg / cm ² and 130 ° C. for bonding
Required a pressure lamination time of 24 hours. In Japanese Patent Publication No. 52-8998, a pressure lamination time of 3 hours at 200 ° C. was required to obtain a sufficient heat-resistant adhesive strength.
Further, in the coating disclosed in JP-A-2-38042, the adhesive strength at a high temperature is not described in the examples, but the inventors have performed additional tests and found that the adhesive strength at a high temperature of 130 ° C. or higher is low. It was standard.

An object of the present invention is to manufacture an electromagnetic steel sheet which is used as an iron core of a transformer or a motor and uses a surface film as an insulating film.
In order to achieve sufficient adhesive strength even when exposed to a high temperature environment of about ℃, and to achieve this adhesive property in a short time (about 1 minute) for lamination, and to improve workability. is there. It is still another object of the present invention to provide a surface-coated electromagnetic steel sheet for heat bonding which simultaneously satisfies other properties required for the surface coated electromagnetic steel sheet for adhesion, such as blocking resistance, and a method for producing the same.

[0005]

That is, in order to achieve the above object, the present invention provides (A) a glass transition point of 80 to
An acrylic resin having a functional group capable of reacting with an epoxy group in a molecule at 130 ° C. and (B) an epoxy resin having a melting point or a softening point of 70 to 140 ° C. as main components. B) The resin solid content weight ratio of the component is 95.
A surface-coated electrical steel sheet for heat bonding, having a mixed resin coating of / 5 to 70/30 and having a gelation rate (curing degree) of the mixed resin in a range of 10 to 90% by weight. I do. Further, an aqueous mixed solution in which the resin solid content weight ratio of the component (A) and the component (B) is 95/5 to 70/30 is applied, and the reaction between the component (A) and the component (B) is performed. Is baked at a sheet temperature of 150 to 350 ° C. so that the gelation rate (hardening degree) of the film after baking is in the range of 10 to 90 wt%. It is intended to provide a manufacturing method.

Here, the acrylic emulsion resin as the component (A) uses acrylic acid or methacrylic acid as one of the raw material monomers, and the dried film thickness of the film after baking is from 0.5 to 0.5%.
It is preferably 10 μm.

[0007]

The present invention will be described below in more detail. The substrate used in the present invention is an electromagnetic steel sheet. This electromagnetic steel sheet may be provided with an insulating coating in advance. In addition, as a substrate used in the present invention, in addition to a magnetic steel sheet, a mild steel sheet, a stainless steel sheet, and using any of a hot-rolled and a cold-rolled sheet of a special steel sheet, that is, without particularly limiting the base steel sheet, The effects of the present invention can be obtained. Further, the surface of these steel plates may be coated with metal plating such as Zn, Ni, Sn or Cr, or a metal alloy plating such as Zn-Ni, Zn-Fe or Zn-Cu. May be subjected to a chemical conversion treatment such as chromate and bond. As described above, the presence or absence of the coating on the steel sheet surface is not particularly limited. In the present invention, a resin solution having the following composition is applied to at least one surface of the magnetic steel sheet and baked to form a surface coating.

First, the aqueous resin mixture used in the present invention will be described. It is essential that the acrylic emulsion resin as the component (A) has a functional group in the molecule that reacts with an epoxy group in the epoxy emulsion resin described later. As the functional group -OH, -COOH,> NH, -NH 2, etc. are exemplified. Specific examples include alkyl ester monomers of acrylic acid, alkyl ester monomers of methacrylic acid, non-functional monomers such as styrene monomers, acrylic acid, methacrylic acid, hydroxyethyl methacrylate, hydroxypropyl methacrylate, tert-butyl methacrylate. A monomer mixture with a functional monomer such as aminoethyl, acrylamide, methacrylamide,
The glass transition point of the obtained acrylic resin is 80 to 130,
Preferably, it can be obtained by a usual emulsion polymerization method by appropriately combining them so as to be within a range of 90 to 120 ° C. Particularly preferred as functional monomers are acrylic acid and methacrylic acid.

The glass transition point of the acrylic resin is 80
If the temperature is lower than ℃, the resulting surface coating remains tacky,
When the coated steel sheet is wound up as a coil or stacked, a blocking phenomenon is likely to occur, which may damage the coating film, which is not preferable. On the other hand, when the glass transition point is higher than 130 ° C., since the melting and softening temperature is inevitably high, it is necessary to set the baking temperature high, and it is also necessary to increase the lamination bonding temperature. Workability may be reduced. In addition, the resulting coating may become brittle and reduce the adhesive strength at room temperature. The content of the functional monomer that reacts with the epoxy group is 3 to 20% by weight, preferably 4 to 10% by weight in the acrylic resin. If it is less than 3%, the reaction with the epoxy group becomes insufficient, and the adhesive strength at high temperatures may be low. If it is more than 20%, the stability may be lowered, for example, the viscosity of the emulsion may be increased.

The epoxy emulsion resin as the component (B) contains two or more epoxy groups in one molecule and has a melting point or softening point of 70 to 140, preferably 80 to 13
One at 0 ° C can be used. 70 ° C melting point or softening point
If it is less than 3, the blocking phenomenon is likely to occur, and the adhesive strength at a high temperature is low. If the temperature is higher than 140 ° C., the film formability may be poor or the adhesive strength may be reduced. Examples of the epoxy resin include bisphenol A type, halogenated bisphenol A type, novolak type, polyglycol type, and bisphenol F type. The epoxy resin has an epoxy equivalent of about 400
-3000, more preferably 800-2000. The epoxy emulsion resin can be produced as an aqueous emulsion by a usual forced emulsification method in the presence of an emulsifier. As the emulsifier used in the forced emulsification method, a polyoxyethylene alkylphenol ether-based nonionic surfactant, a polyoxyethylene polyoxypropylene block polyether or an adduct thereof with a diisocyanate compound may be used alone or as a blend. desirable.

It is essential that the coating component used in the present invention contains the above-mentioned components (A) and (B), and if necessary, a film-forming aid, a colored pigment having an insulating property, Pigments, antirust pigments or defoamers, surface conditioners,
What mixed various additives, such as a thickener, a pigment dispersing agent, and a preservative, may be used. Other cross-linking agents or reaction catalysts may be added in order to promote the cross-linking reaction alone or between the components. Further, a technique known in the art such as mixing or copolymerization of another aqueous resin may be used in combination for the purpose of modifying the resin.

The above components (A) and (B) may be used alone or in combination of a plurality of components of the same type. The mixing ratio of the components (A) and (B) is such that each resin solid content weight ratio is (A) / (B) = [(70) /
(30)] to [(95) / (5)], preferably [(8
0) / (20)] to [(90) / (10)]. If the mixing ratio is outside the above range, the adhesive strength will be low. Further, the resin solid content of each of the components (A) and (B) is preferably 20 to 20 in the mixed solution from the viewpoint of coating workability and the like.
Preferably, the proportion is 60%, more preferably 30 to 55% by weight.

As a method for applying the mixed liquid, a coating method such as a roll coater, a curtain flow coater, a spray coating or a squeeze coater can be used, and is not particularly limited. As a method of baking the mixed solution, a known baking furnace such as a hot-air drying furnace, an induction heating furnace, or a resistance heating furnace can be used, and is not particularly limited.

The dry film thickness of the film after application and baking of the mixed solution is preferably 0.5 to 10, more preferably 3 to 8 μm.
When the film thickness is less than 0.5 μm, the adhesive strength may not be reached (not reach the original value of the material constituting the film), and when the film thickness is more than 10 μm, the adhesive strength may not be attained. Saturation can be uneconomical and can cause problems such as easy blocking.

[0015] The baking temperature is 150 to 35 in the ultimate plate temperature.
0, more preferably 180 to 280 ° C. 150 ° C
If it is less than 1, the aqueous medium is insufficiently dried to cause blistering at the time of bonding, or the crosslinking reaction between the components (A) and (B) becomes insufficient (gelation rate is less than 10 wt%), so that the final The degree of successful cross-linking reaction rate is low, which may lead to insufficient adhesion strength. When the temperature is higher than 350 ° C., the crosslinking reaction is almost completed at the time of baking (gelation rate is 90 watts).
t%), does not melt at the time of lamination bonding, and may not be bonded. The preferred range of the gelation ratio of the film after baking is 20 to 85% by weight, more preferably 30 to 70% by weight.
wt%. For laminating and bonding a predetermined amount of the surface-coated electromagnetic steel sheet for heat bonding obtained by the production method of the present invention, a reached plate temperature of 150 to 350 ° C., preferably 180 to 30 ° C.
At 0 ° C., the pressure is ² to 100 kg / cm ^2, and 0.5 to 1
Sufficient adhesiveness can be obtained in 0 minutes.

[0016]

Next, the present invention will be specifically described based on examples. (Example 1) The mixture shown in Table 1 was applied to each bonding surface of two electromagnetic steel sheets (sheet thickness 0.5 mm, surface roughness Ra 0.18 μm) using a roll coater. The film was baked in a hot air drying oven for 60 seconds so as to become warm, and the film thickness after drying was adjusted to 5.0 μm. The laminated adhesive electromagnetic steel sheet for measuring the shear adhesive strength was prepared by laminating the adhesive surfaces of the electromagnetic steel sheets having the coatings formed thereon, and press-bonding with a pressure of 10 kg / cm ² at a heating temperature and a pressing time described in Table 2. Produced. The measurement of the shear adhesive strength was carried out by immediately applying the obtained laminated adhesive electromagnetic steel sheet to 2
The test was performed at a temperature of 3 ° C. and 150 ° C. Table 2 shows the measurement results of the shear adhesive strength. In addition, as an evaluation of the blocking property, the adhesive surfaces of the magnetic steel sheets on which the coatings were formed were overlapped with each other and aged at 80 ° C. for 2 days while maintaining the pressure at 200 kg / cm ² , and the shear adhesive strength at 23 ° C. (blocking test) Post-shear adhesive strength). Table 2 shows the results. In addition, the shear adhesive strength when the film thickness after drying was changed in Invention Example 2 was measured. Table 3 shows the results.

The degree of cure of the coating after baking and after lamination was evaluated by the gelation rate. The gelation ratio was calculated from the remaining amount after extracting the coated steel sheet after baking or the coated steel sheet peeled off after laminating with methyl ethyl ketone for 2 hours using a Soxhlet extractor. Table 2 shows the results. The gelation ratio of the coating of Invention Example 1 before baking was 0 wt%, and when baked at 200 ° C. for 1 hour and completely cured, it was 98 wt%, and the method of calculating the gelation ratio generally corresponds to the degree of curing. It was confirmed that. Gelation rate = (residual weight of coating after extraction / weight of coating before extraction)
× 100 (wt%)

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

[Table 3]

[0021]

[0022]

As is clear from the results in Table 2, the shear adhesive strength of the surface-coated electrical steel sheet for heat bonding of the present invention is due to the crosslinking reaction between the resin component (A) and the resin component (B). It is high at normal and high temperatures. Also, it has excellent blocking resistance. Further, high adhesive strength is achieved with a short lamination time. When the mixing ratio of the resin component (A) and the resin component (B) is in the range of 70/30 to 95/5, the adhesive strength is maximized. Further, high adhesive strength can be obtained when the gelation rate of the film after baking is in the range of about 10 to 90%. Furthermore, as is clear from Table 3, high adhesive strength and blocking resistance are achieved when the film thickness after drying is in the range of about 0.5 to 10 μm. In addition, by raising the baking temperature and prolonging the heating lamination time,
Since the adhesive strength at high temperature has been increased, it can be seen that the resin component before lamination and adhesion is still in an incomplete cross-linking reaction (gelation rate).

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI B05D 7/24 302 B05D 7/24 302U (56) References JP-A-2-208034 (JP, A) (58) Fields surveyed (Int.Cl. ⁶ , DB name) B32B 15/08 B05D 3/00 B05D 3/02 B05D 7/14 B05D 7/24

Claims (6)

(57) [Claims] (1) At least one surface of an electromagnetic steel sheet,
The main components are (A) an acrylic resin having a glass transition point of 80 to 130 ° C. and containing a functional group capable of reacting with an epoxy group in the molecule, and (B) an epoxy resin having a melting point or softening point of 70 to 140 ° C. And a mixed resin coating in which the weight ratio of the resin solids of the component (A) and the component (B) is 95/5 to 70/30, and the gelation ratio (curing degree) of the mixed resin is 10 to 90. A surface-coated electrical steel sheet for heat bonding, which is in the range of% by weight. 2. The surface-coated magnetic steel sheet for heat bonding according to claim 1, wherein at least one of the raw material monomers of the acrylic emulsion resin as the component (A) is acrylic acid or methacrylic acid. 3. A film having a dry thickness of 0.5 to 0.5 after baking.
The surface-coated electrical steel sheet for heat bonding according to claim 1 or 2, which has a thickness of 10 µm. 4. An at least one surface of an electromagnetic steel sheet, comprising: (A) an acrylic emulsion resin having a glass transition point of 80 to 130 ° C. and containing a functional group capable of reacting with an epoxy group in a molecule; and (B) An epoxy emulsion resin having a melting point or softening point of 70 to 140 ° C. as a main component, and a resin solid content ratio of the component (A) to the component (B) of 95/5 to 70/30.
An aqueous mixed solution is applied to form a coating film, and the ultimate plate temperature is in the range of 150 to 350 ° C. so that the gelation rate (hardening degree) of the coating after baking is in the range of 10 to 90 wt%. A method for producing a surface-coated electrical steel sheet for heat bonding, characterized by baking. 5. The method according to claim 4, wherein at least one of the raw material monomers of the acrylic emulsion resin as the component (A) is acrylic acid or methacrylic acid. 6. The dried film thickness of the film after baking is 0.5 to 0.5.
The method for producing a surface-coated electrical steel sheet for heat bonding according to claim 4 or 5, wherein the thickness is 10 µm.