JP2937734B2 - Method for producing surface-coated electrical steel sheet for heat 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 magnetic steel sheet which is used by being punched, sheared, pressed, bonded after being pressed and heated.

[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 steel sheet coated with a mixed surface resin composed of a thermoplastic acrylic resin, an epoxy resin and an epoxy resin curing agent. .

[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 Japanese Patent Publication No. 49-13318, as is clear from the examples, the adhesive strength at 130 ° C. is 18 kg / cm ² , and a pressure lamination time of 24 hours at 130 ° C. is required for bonding. Was. 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. JP-A-2-380
No. 42 does not describe the adhesive strength under high temperature,
According to the test of the present inventors, at 150 ° C., no adhesiveness was exhibited.

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.
It exhibits sufficient adhesive strength even when exposed to a high temperature environment of about ℃, and achieves this adhesive property in a short time (about 1 minute) for lamination, and furthermore, has an adhesive property such as blocking resistance. An object of the present invention is to provide a method for producing a surface-coated electrical steel sheet for heat bonding, which simultaneously satisfies other characteristics required for the surface-coated electrical steel sheet.

[0005]

That is, the present invention provides (A) a glass transition point of at least 80 to 150 ° C. on at least one surface of an electrical steel sheet, wherein —OH, —COOH,
> NH, -NH _2, and> acrylic resin emulsion of the active functional group selected from the group consisting of CH ₂ containing at least one or more, (B) an aqueous solution or emulsion of the epoxy resin and / or phenolic resin, and (C) An aqueous mixed solution containing an aqueous blocked isocyanate compound as a main component, which reacts with the component (A) or both the components (A) and (B) by dissociation of the blocking group by heating, is applied. B) Component and the above (C)
The gelation rate (curing degree) of the coating after baking is 1 when the reaction with the components
An object of the present invention is to provide a method for producing a surface-coated magnetic steel sheet for heat bonding, which is baked so as to be in a range of 0 to 90%.

Here, the weight ratio A / B of the solid components A and B is preferably 50/50 to 95/5.
The dried film thickness of the film after baking is preferably 0.5 to 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 any of a hot-rolled sheet and a cold-rolled sheet of a special steel sheet, that is, the base steel sheet is not particularly limited. The effect 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. The acrylic resin emulsion as the component (A), -OH in the _{molecule, -COOH,> NH, -NH 2} ,
And any containing an active functional group selected from the group consisting of> CH ₂ . 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. The glass transition point of the acrylic resin obtained as a result of mixing the monomer mixture with a functional monomer such as aminoethyl is 80 to 15
It can be obtained by a usual emulsion polymerization method by appropriately combining them so as to be within the range of 0 ° C.

If the glass transition point is lower than 80 ° C., the resulting surface coating film will remain sticky, and a blocking phenomenon will easily occur when the coated steel sheet is wound or stacked as a coil. It is not preferable because the coating film may be damaged. On the other hand, when the glass transition point is higher than 150 ° C., the temperature for melting and softening is inevitably high, so that it is necessary to set the baking temperature high, and it becomes difficult to control the reaction of the component (C) described later. In addition to the above, it is necessary to increase the lamination bonding temperature, which lowers the workability, which is not preferable.

The component (B) may be either an epoxy resin or a phenol resin, or both. The resin may be in the form of an aqueous solution or an emulsion. The epoxy resin contains two or more epoxy groups in one molecule, and can be used in a liquid state at room temperature, preferably in a solid state. For example, bisphenol A type, halogenated bisphenol A type, novolak type, polyglycol type, bisphenol F type, epoxidized oil and the like can be mentioned. The epoxy resin emulsion can be produced by a usual forced emulsification method of these epoxy resins in the presence of an emulsifier. As the phenol resin, a general-purpose novolak-type or resol-type water-soluble phenol resin or a phenol resin emulsion can be used.

In the aqueous blocked isocyanate compound (C), the blocking group is dissociated by heating during baking and lamination bonding, and the component (A) or (B)
Any substance can be used as long as it reacts with an active functional group contained in the molecule of the component to form a crosslink. However, in the present invention, since the cross-linking reaction is controlled to be incomplete at the time of baking (gelation rate: 10 to 90%), the dissociation temperature of the block group is significantly lower than the baking temperature. Is not preferred. In addition, it is desirable to completely dissociate to form a cross-linking bond during lamination bonding. The preferred range of the dissociation temperature is 120 to 200 ° C. As the blocking group, alcohols, ε-caprolactam,
Phenol, oxime and the like can be used.

The amount of component (C) is preferably around the stoichiometric amount of the active functional groups of components (A) and (B).
If it is excessively mixed, an odor may be generated when welding an intermediate product obtained by laminating and bonding coated steel sheets. (C) A preferable range of the compounding amount is -50 to + 400% of the stoichiometric amount.

It is essential that the coating component used in the present invention contains the above-mentioned components (A), (B) and (C), and if necessary, further has a film-forming aid and an insulating property. It may be a compound containing various additives such as a coloring pigment, an extender pigment, a rust preventive pigment or an antifoaming agent, a surface conditioner, a thickener, a pigment dispersant, and a preservative. Other cross-linking agents or reaction catalysts may be added to promote the cross-linking reaction between the components. Further, a technique known to those skilled in the art such as mixing and copolymerization of another aqueous resin may be used for the purpose of modifying the resin. (A)
Each of the components (C) to (C) may use a plurality of components of the same type.

The mixing ratio of each of the resin components (A) and (B) is not particularly limited.
(A) / (B) = [(50) / (50)] to [(95)
/ (5)]. When the amount of the component (A) is less than the above range, the cohesive strength is reduced due to a decrease in the crosslinking density and an insufficient mixing ratio of the resin component having a high glass transition point, so that the adhesive strength at high temperatures is reduced. Conversely, when the component (A) is more than the above range, the adhesive strength at high temperatures is improved,
Due to the brittle mechanical properties of the component (A), the adhesive strength at room temperature may decrease. (A),
The resin solid content of the component (B) is preferably 20 to 60% by weight in the mixed solution from the viewpoint of coating workability and the like.

As a method for applying the mixed liquid, a coating method such as a roll coater, a curtain flow coater, a spray coating, and 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 mixture is preferably 0.5 to 10 μm. 0.5 μm thick
If the thickness is less than 10 μm, the adhesive strength may not be achieved. If the thickness is more than 10 μm, the adhesive strength may be saturated, which may be uneconomical and may cause blocking. May occur.

The baking temperature is 150 to 450 in the ultimate plate temperature.
C is desirable. When the temperature is lower than 150 ° C., the aqueous medium is insufficiently dried to cause blistering at the time of adhesion, or the progress of the crosslinking reaction is insufficient (gelation rate is less than 10%), thereby causing blocking or ultimately. Inadequate achievement of a high crosslinking reaction rate may result in insufficient adhesion strength. When the temperature exceeds 450 ° C., the crosslinking reaction is almost completed at the time of baking (gelation rate exceeds 90%),
At the time of lamination bonding, it no longer melts and may not be bonded. The preferred range of the gelation rate of the film after baking is 30.
To 85%, more preferably 50 to 80%.

[0018]

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 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 superimposed on each other, and after being aged at 80 ° C. for 2 days while maintaining the pressure at 200 kg / cm ² , the shear adhesive strength at 23 ° C. was measured. .
Table 2 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%, and the coating was baked at 200 ° C. for 1 hour.
When it was completely cured, it was 98%, and it was confirmed that the method of calculating the gelation rate generally corresponded to the degree of curing. Gelation rate = residual weight of coating after extraction / weight of coating before extraction x 1
00 (%)

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

As is clear from Table 2, the shear adhesive strength of the surface-coated magnetic steel sheet for heat bonding of the present invention is at a high level at normal temperature and high temperature. Also, it has excellent blocking resistance. Further, high adhesive strength is achieved with a short lamination time. In addition, by raising the baking temperature and prolonging the heating lamination time,
Since the gelation rate of the coating and the adhesive strength at high temperatures are increased, it is understood that the resin component before lamination and bonding is still in an incomplete cross-linking reaction (gelation rate).

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI B05D 7/14 B05D 7/14 H B29C 59/00 B29C 59/00 E C09D 133/02 C09D 133/02 163/00 163/00 175/04 175/04 // B32B 15/08 B32B 15/08 GB29K 33:00 63:00 (56) References JP-A-60-38069 (JP, A) JP-A-6-57177 (JP, A JP-A-4-367766 (JP, A) JP-A-62-146985 (JP, A) JP-A-54-103433 (JP, A) JP-A-3-157414 (JP, A) 158079 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) B05D 7/24 301-303 B05D 3/02 B05D 7/14 B29C 59/00 C09D 133/02 C09D 163/00 C09D 175/04

Claims (3)

(57) [Claims] (1) At least one surface of an electromagnetic steel sheet has: (A) a glass transition point of 80 to 150 ° C.,
OH, -COOH,> NH, -NH 2, and> CH ₂
An acrylic resin emulsion containing at least one or more active functional groups selected from the group consisting of: (B) an aqueous solution or emulsion of an epoxy resin and / or a phenol resin; and (C) a block group dissociated by heating to form the above (A) )) Or an aqueous mixed solution containing an aqueous blocked isocyanate compound as a main component which reacts with both the components (A) and (B), and coats the components (A) and (B) with the component (C). The gelation rate (curing degree) of the coating after baking is 10
A method for producing a surface-coated electrical steel sheet for heat bonding, characterized in that it is baked so as to be in the range of 90%. 2. The solid content weight ratio of component A and component B, A / B.
The method for producing a surface-coated electromagnetic steel sheet for heat bonding according to claim 1, wherein the ratio is 50/50 to 95/5. 3. The dried film thickness after baking is 0.5 to 10 μm.
The method for producing a surface-coated electromagnetic steel sheet for heat bonding according to claim 1 or 2, wherein m is m.