Steel sheet laminate production method, steel sheet laminate, and adhesive composition

Abstract

To addresses: a first problem of providing a steel sheet laminate production method with which it is possible to produce a steel sheet laminate having excellent adhesive strength, in which the curing speed of an adhesive is sufficiently quick and the time necessary for completing adhesion and forming the steel sheet laminate is short, and which provides good workability; and a second problem of producing a steel sheet laminate having excellent adhesive strength.SOLUTION: Provided is a steel sheet laminate production method that involves adhering steel sheets having applied thereto a primer containing a copper compound, by using a radically polymerizable adhesive composition containing (A) a radically polymerizable compound, (B) an organic peroxide, and (C) a phosphate ester compound having a radically polymerizable group. In the method, the amount of the phosphate ester compound (C) having a radically polymerizable group is not less than 0.055 parts by mass but less than 1 part by mass with respect to 100 parts by mass of the radically polymerizable compound (A).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing a steel sheet laminate, a steel sheet laminate, and an adhesive composition. [Background technology]

[0002] Steel sheet laminates, manufactured by laminating steel sheets, particularly electromagnetic steel sheets, are used in applications such as motor rotors and stators installed in various devices. Steel sheet laminates are typically assembled by caulking or welding. However, as laminated electromagnetic steel sheets become thinner, it has become necessary to address iron loss caused by stress concentration, strain concentration, and electrical short circuits between layers due to mechanical fastening. For this reason, a technology using an insulating adhesive to manufacture steel sheet laminates has attracted attention as a method for reducing iron loss by dispersing stress. Curable resins such as epoxy resin adhesives and curable acrylic adhesives are commonly used as adhesives. Among these, curable acrylic adhesives are often used when room-temperature curing is desired. Patent Document 1 describes the production of a steel sheet laminate using an anaerobic adhesive (a type of curing acrylic adhesive) and steel sheets whose surfaces have been coated with press processing oil containing copper soap as a curing accelerator. Patent Document 2 describes a method in which a pretreatment agent for accelerating the curing of an anaerobic adhesive containing a chelate compound of copper, vanadium, chromium, manganese, iron, titanium, nickel, or cobalt as an active ingredient is applied to a metal bolt / nut, and then an anaerobic adhesive containing a (meth)acrylate compound is applied to fix the bolt / nut. Patent Document 3 describes a method in which a curing accelerator for a (meth)acrylic curable composition containing a copper and / or vanadium chelate compound is applied to a metal bolt / nut, and then an anaerobic adhesive containing a (meth)acrylate compound is applied to fix the bolt / nut. Patent Document 4 describes a method in which an anaerobic adhesive composition containing an anaerobically polymerizable acrylic acid ester monomer, an organic peroxide, and a phosphoric acid compound having a (meth)acryloyl group is applied to the inner wall and / or shaft of a ring, and the shaft is inserted into the ring and fitted to be fixed. Patent Document 5 describes the use of a polymerizable adhesive composition containing a polymerizable olefinically unsaturated monomer compound, a phosphoric acid compound having at least one olefinically unsaturated group, and an organic peroxide for bonding steel to steel and aluminum to aluminum. Patent Document 6 discloses a composition comprising: (A) component: a radical polymerizable compound; (B) component: a radical polymerization initiator; and (C) component: a compound represented by the following formula (1) or (2): -OP(O)(OH)-O- (1) -OP(O)(OH)2···(2) The present invention discloses a radically polymerizable adhesive composition for bonding steel sheet laminates, which comprises a phosphoric acid ester compound having a group represented by the formula: [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-334648 [Patent Document 2] Special Publication No. 49-021093 [Patent Document 3] Japanese Patent Application Publication No. 60-179407 [Patent Document 4] Japanese Patent Application Publication No. 51-132234 [Patent Document 5] Japanese Unexamined Patent Publication No. 54-141826 [Patent Document 6] International Publication No. 2019 / 123885 Summary of the Invention [Problem to be solved by the invention]

[0004] The adhesive compositions described in Patent Documents 1 to 6 can produce steel sheet laminates with excellent adhesive strength, but they have insufficient curing speeds, and require a long time to complete adhesion and form a steel sheet laminate, resulting in poor workability. The problem to be solved by the present invention is to provide a method for producing a steel sheet laminate which can produce a steel sheet laminate having excellent adhesive strength, in which the adhesive has a sufficiently fast curing rate, the time required for completing bonding and forming the steel sheet laminate is short, and the method has good workability. Another problem that the present invention aims to solve is to provide an adhesive composition for steel sheet laminates, which can produce steel sheet laminates with excellent adhesive strength, has a sufficiently fast curing rate, requires a short time for completion of bonding and construction of a steel sheet laminate, and has good workability. [Means for solving the problem]

[0005] As a result of intensive research into solving the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by a method for producing a steel sheet laminate using a specific adhesive composition, and by the steel sheet laminate and specific adhesive composition obtained thereby, and have thus completed the present invention. Specifically, the following applies: [Item 1] A method for producing a steel sheet laminate in which steel sheets coated with a primer containing a copper compound are bonded using a radically polymerizable adhesive composition containing (A) a radically polymerizable compound, (B) an organic peroxide, and (C) a phosphate ester compound having a radically polymerizable group, wherein the amount of (C) the phosphate ester compound having a radically polymerizable group is 0.055 parts by mass or more but less than 1 part by mass per 100 parts by mass of the (A) radically polymerizable compound. [Item 2] A steel sheet laminate produced by the method described in Item 1. [Item 3] An adhesive composition for a steel sheet laminate that bonds steel sheets coated with a primer containing a copper compound, (A) a radical polymerizable compound, (B) an organic peroxide, and (C) a phosphate ester compound having a radical polymerizable group, An adhesive composition in which the amount of (C) the phosphate ester compound having a radical polymerizable group is 0.055 parts by mass or more and less than 1 part by mass per 100 parts by mass of (A) the radical polymerizable compound. [Effects of the Invention]

[0006] The present invention provides a method for producing a steel sheet laminate that can produce a steel sheet laminate with excellent adhesive strength, has a sufficiently fast curing rate of the adhesive, requires a short time to complete bonding and form the steel sheet laminate, and is easy to work with. The present invention also provides an adhesive composition for steel sheet laminates that can produce steel sheet laminates with excellent adhesive strength, has a sufficiently fast curing rate, requires a short time for completion of bonding and construction of a steel sheet laminate, and has good workability. The method for producing a steel sheet laminate and the adhesive composition for a steel sheet laminate according to the present invention can simplify the manufacturing process for a steel sheet laminate, can reduce iron loss in the steel sheet laminate, and contribute to improving the performance and reliability of motor rotors and stators. Therefore, they are extremely effective and can be applied in a wide range of fields, making them industrially useful. The adhesive composition for steel sheet laminates of the present invention exhibits excellent adhesive strength to steel sheets whose surfaces have been treated with punching oil, in particular to electrical steel sheets and cold-rolled steel sheets (SPCC-SD), and is capable of providing strong adhesion without removing the punching oil applied to the steel sheets in the manufacturing process for the steel sheet laminate, making it extremely useful from an industrial perspective. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic diagram of a manufacturing apparatus for a steel sheet stack according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0008] The method for producing a steel sheet laminate, the steel sheet laminate, and the adhesive composition of the present invention will be described in detail below. In this specification, "(meth)acrylic" means "acrylic" and "methacrylic", "(meth)acrylate" means "acrylate" and "methacrylate", and "(meth)acryloyl" means "acryloyl" and "methacryloyl", respectively.

[0009] [Manufacturing method for steel plate laminates] The method for producing a steel sheet laminate of the present invention involves bonding steel sheets coated with a primer containing a copper compound using a radical-polymerizable adhesive composition containing (A) a radical-polymerizable compound, (B) an organic peroxide, and (C) a phosphate ester compound having a radical-polymerizable group. The radical-polymerizable adhesive composition contains (C) a phosphate ester compound having a radical-polymerizable group in an amount of 0.055 parts by mass or more but less than 1 part by mass per 100 parts by mass of the (A) radical-polymerizable compound.

[0010] <Radical Polymerizable Adhesive Composition> ((A) Radical Polymerizable Compound) The radically polymerizable compound (A) contained in the radically polymerizable adhesive composition used in the method for producing a steel sheet laminate of the present invention is at least one selected from the group consisting of radically polymerizable monomers, radically polymerizable oligomers, and radically polymerizable polymers having a radically polymerizable functional group, particularly a radically polymerizable ethylenically unsaturated group. The radically polymerizable compound (A) is a radically polymerizable compound other than the phosphate ester compound (C) having a radically polymerizable group, which will be described later. Examples of the radically polymerizable functional group include a (meth)acryloyl group, a vinyl group, an allyl group, and a (meth)acrylamide group. Of these, a (meth)acryloyl group is preferred.

[0011] From the viewpoint of adhesive strength to steel sheets, particularly electromagnetic steel sheets, having a punching oil component applied to the surface thereof, it is preferable to use one or more radically polymerizable oligomers and / or radically polymerizable polymers as the (A) radically polymerizable compound. Furthermore, from the viewpoints of exhibiting superior adhesive strength to steel sheets such as cold-rolled steel sheets and electromagnetic steel sheets, adjusting the viscosity of the adhesive composition to facilitate easy handling, and preventing the adhesive from squeezing out when the steel sheets are laminated together, it is preferable to use one or more radically polymerizable oligomers and / or radically polymerizable polymers in combination with one or more radically polymerizable monomers.

[0012] {Radical polymerizable oligomer and / or radical polymer} Examples of the radically polymerizable oligomer and / or radically polymerizable polymer include one or more selected from the group consisting of urethane (meth)acrylate, epoxy (meth)acrylate, bisphenol alkylene oxide adduct (meth)acrylate, ether (meth)acrylate, ester (meth)acrylate, isoprene-based (meth)acrylate, hydrogenated isoprene-based (meth)acrylate, (meth)acrylic group-containing acrylic polymer, (meth)acrylic group-containing polyisobutylene, etc. Among these, it is preferable to use one or more selected from the group consisting of urethane (meth)acrylate, epoxy (meth)acrylate, bisphenol alkylene oxide adduct (meth)acrylate, and ether (meth)acrylate because of their excellent adhesive strength to cold-rolled steel sheets and / or electromagnetic steel sheets, and the high glass transition temperature of the cured product.

[0013] The urethane (meth)acrylate can be obtained by reacting at least a polyol component, a polyisocyanate component, and a compound having a (meth)acrylate group. The polyol component may include, for example, one or more polymer polyols selected from the group consisting of (hydrogenated) butadiene polyols, polycarbonate polyols, polyether polyols, polyester polyols, polyacrylate polyols (acrylic polyols), polyurethane polyols, and the like. As the polyisocyanate component, for example, one or more selected from the group consisting of aliphatic polyisocyanates (hexamethylene diisocyanate, etc.), alicyclic polyisocyanates (dicyclohexylmethane diisocyanate, isobornyl diisocyanate, etc.), aromatic polyisocyanates (toluene diisocyanate, diphenylmethane diisocyanate, etc.), and aromatic aliphatic polyisocyanates (xylylene diisocyanate, etc.) can be used. As the compound having a (meth)acrylate group, for example, one or more compounds selected from the group consisting of (meth)acrylate group-containing compounds having a group that reacts with an isocyanate group (hydroxyalkyl (meth)acrylate, acrylic acid, etc.) or isocyanate group-containing (meth)acrylate group-containing compounds can be used.

[0014] Examples of the urethane (meth)acrylate include one or more selected from the group consisting of urethane (meth)acrylates having a (hydrogenated) polybutadiene skeleton, urethane (meth)acrylates having a polycarbonate skeleton, urethane (meth)acrylates having a polyether skeleton, urethane (meth)acrylates having a polyester skeleton, urethane (meth)acrylates having a polyacrylate skeleton, urethane (meth)acrylates having a polyurethane skeleton, and urethane (meth)acrylates having a castor oil skeleton.

[0015] Epoxy (meth)acrylate can be obtained by reacting an epoxy resin with a (meth)acrylate compound having a functional group that reacts with an epoxy group. Examples of the epoxy resin include one or more selected from the group consisting of bisphenol-type epoxy resins (bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, etc.), phenol novolac-type epoxy resins, and epoxy resins such as terminal glycidyl ethers of alkylene oxide adducts of bisphenol-type epoxy resins. Examples of the (meth)acrylate compound having a functional group that reacts with an epoxy group include one or more compounds selected from the group consisting of (meth)acrylate compounds having a carboxyl group such as (meth)acrylic acid, and (meth)acrylate compounds having a hydroxyl group such as hydroxyethyl (meth)acrylate. Commercially available epoxy (meth)acrylates can be used, such as DICLITE (registered trademark) UE-8071-60BH, UE-8740, and UE-8410 (manufactured by DIC Corporation), Kayard R-115F (manufactured by Nippon Kayaku Co., Ltd.), HITAROID 7851 (manufactured by Showa Denko K.K.), Epoxy Ester 3000MK and 3000A (manufactured by Kyoeisha Chemical Co., Ltd.), Viscoat V#540 (manufactured by Osaka Organic Chemical Industry Co., Ltd.), EBECRYL 600, and EBECRYL 3700 (manufactured by Daicel-Allnex Corporation).

[0016] Examples of the bisphenol alkylene oxide adduct (meth)acrylate include those represented by the following formula (A): [ka] (In formula (A), R 11 is a hydrogen atom or a methyl group. R 12 is a hydrogen atom or a methyl group. A 1 is an alkylene group having 1 to 6 carbon atoms, and when there are a plurality of groups, they may be different from each other. A 2 is an alkylene group having 1 to 6 carbon atoms, and when there are a plurality of groups, they may be different from each other. X is a direct bond, -CH2-, -C(CH3)2-, -CH(CH3)-, -O-, -S-, -SO2-, -CO-, -CF2-, -C(CF3)2-, -C(Ph)2-, or -CH(Ph)- (Ph is a phenyl group). m is an integer of 0 or 1 or more. n is an integer of 0 or 1 or more. Examples of the compound include one or more compounds represented by the formula: For example, one or more compounds selected from the group consisting of (poly)ethoxy-modified bisphenol A di(meth)acrylate, (poly)propoxy-modified bisphenol A di(meth)acrylate, and the like. Among these, (poly)ethoxy-modified bisphenol A di(meth)acrylate is preferred, and in the compound represented by the above formula (A), R 11 is a hydrogen atom or a methyl group, and R 12 is a hydrogen atom or a methyl group, and A 1 and A 2 Particularly preferred are compounds in which is an alkylene group having 2 carbon atoms, X is -C(CH3)2-, and m+n (ie, ethoxy equivalent) is 1 to 40 (preferably 2 to 10).

[0017] {Radical polymerizable monomer} The radical polymerizable monomer is a compound having one or more radical polymerizable groups in the molecule, is not an oligomer or a polymer, and is a radical polymerizable compound other than the (C) phosphate ester compound having a radical polymerizable group, and is not particularly limited. For example, it may be one or more selected from the group consisting of monofunctional monomers, polyfunctional monomers, etc. Among these, it is preferable to include a monofunctional monomer having a functional group such as a hydroxyl group, a carboxyl group, an amino group, or a glycidyl group, since this allows the formation of a radical polymerizable adhesive composition for steel sheet laminates that has even better adhesion to steel sheets such as cold-rolled steel sheets and electromagnetic steel sheets and that forms a cured product with a high glass transition point.

[0018] Examples of monofunctional monomers include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, caprolactone-modified tetrahydrofurfuryl (meth)acrylate, cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, isobornyl (meth)acrylate, and benzyl (meth)acrylate. , phenyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, phenoxytetraethylene glycol (meth)acrylate, nonylphenoxyethyl (meth)acrylate, nonylphenoxytetraethylene glycol (meth)acrylate, methoxydiethylene glycol (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, butoxyethyl (meth)acrylate, butoxytriethylene glycol (

[0033] Examples of the hydroxyethyl (meth)acrylate include one or more selected from the group consisting of methyl methyl acrylate, ...Among these, from the viewpoint of even better adhesion to cold-rolled steel sheets and / or electromagnetic steel sheets and faster curing properties (short set time), one or more selected from the group consisting of dicyclopentanyl (meth)acrylate, isobornyl (meth)acrylate, benzyl (meth)acrylate, phenyl (meth)acrylate, phenoxyethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, etc. are preferred.

[0019] Examples of polyfunctional monomers include 1,3-butylene glycol di(meth)acrylate, 1,4-butylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexane glycol di(meth)acrylate, ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, ethylene oxide-modified neopentyl glycol di(meth)acrylate, propylene oxide-modified neopentyl glycol di(meth)acrylate, hydroxypivalic acid ester neopentyl glycol diacrylate, caprolactone-modified hydroxypivalic acid ester neopentyl glycol diacrylate, neopentyl glycol-modified trimethylolpropane di(meth)acrylate, stearic acid-modified pentaerythritol di(meth)acrylate, dicyclopentenyl di(meth)acrylate, ethylene oxide-modified dicyclopentenyl Di(meth)acrylate, di(meth)acryloyl isocyanurate, dimethyloltricyclodecane di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, ethylene oxide modified trimethylolpropane tri(meth)acrylate, propylene oxide modified trimethylolpropane tri(meth)acrylate, epichlorohydrin modified trimethylolpropane tri(meth)acrylate, epichlorohydrin modified glycerol tri(meth)acrylate

[0033] Examples of the acrylate include one or more selected from the group consisting of alkyl(meth)acrylate, tris(acryloyloxyethyl)isocyanurate, ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol monohydroxypenta(meth)acrylate, alkyl-modified dipentaerythritol pentaacrylate, dipentaerythritol hexa(meth)acrylate, and caprolactone-modified dipentaerythritol hexa(meth)acrylate.Among these, from the viewpoint of achieving even better adhesion to cold-rolled steel sheets and / or electromagnetic steel sheets and faster curing (short set time), it is preferable to use one or more selected from the group consisting of dicyclopentenyl di(meth)acrylate, ethylene oxide-modified dicyclopentenyl di(meth)acrylate, di(meth)acryloyl isocyanurate, dimethyloltricyclodecane di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, tris(acryloyloxyethyl)isocyanurate, ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol monohydroxypenta(meth)acrylate, and the like.

[0020] The amount of the radically polymerizable compound (A) blended is, for example, 90% by mass or more, preferably 95% by mass or more, and for example, 99% by mass or less, preferably 98% by mass or less, based on 100% by mass of the total amount of the radically polymerizable adhesive composition.

[0021] ((B) Organic peroxide) The (B) organic peroxide contained in the radical polymerizable adhesive composition used in the method for producing a steel sheet laminate of the present invention is intended to impart anaerobic curability and / or heat curability to the radical polymerizable adhesive composition. Examples of (B) organic peroxides include one or more selected from the group consisting of hydroperoxides such as cumene hydroperoxide, t-butyl hydroperoxide, p-menthane hydroperoxide, methyl ethyl ketone peroxide, cyclohexane peroxide, dicumyl peroxide, diisopropylbenzene hydroperoxide, and others, as well as ketone peroxides, diallyl peroxides, peroxy esters, etc. Among these, hydroperoxides are preferably used from the viewpoint of achieving even better reactivity and storage stability of the radically polymerizable adhesive composition for bonded steel sheet laminates.

[0022] From the viewpoint of excellent anaerobic curing properties, (B) organic peroxides are preferably those having a one-hour half-life temperature of 80° C. or higher, preferably 100° C. or higher, and 300° C. or lower, preferably 200° C. or lower. The one-hour half-life temperature is a value measured by thermal decomposition at a concentration of 0.1 mol / L of the organic peroxide in benzene. Examples of organic peroxides having a one-hour half-life temperature in the range of 80° C. to 300° C. include hydroperoxides. Specific examples of hydroperoxides include one or more selected from the group consisting of p-menthane hydroperoxide, diisopropylbenzene hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, cumene hydroperoxide, and t-butyl hydroperoxide.

[0023] The amount of the (B) organic peroxide blended is, for example, 0.05 parts by mass or more, preferably 0.1 parts by mass or more, and for example, 10 parts by mass or less, preferably 5 parts by mass or less, relative to 100 parts by mass of the (A) radical polymerizable compound. By blending the (B) organic peroxide in the range of 0.05 parts by mass or more and 10 parts by mass or less relative to 100 parts by mass of the (A) radical polymerizable compound, the adhesive strength of the radical polymerizable adhesive composition can be improved.

[0024] ((C) Phosphate ester compound having a radical polymerizable group) The (C) phosphate ester compound having a radical polymerizable group contained in the radical polymerizable adhesive composition used in the method for producing a steel sheet laminate of the present invention is a compound having a radical polymerizable functional group and a phosphate ester compound represented by the following formula (1) or (2): -OP(O)(OH)-O- (1) -OP(O)(OH)2···(2) The radical-polymerizable adhesive composition for steel sheet laminates exhibits a remarkable effect of providing a radical-polymerizable adhesive composition for steel sheet laminates that exhibits adhesive strength to steel sheets whose surfaces are covered with punching oil, by using the radical-polymerizable adhesive composition in combination with the radical-polymerizable compound (A) and the organic peroxide (B).

[0025] The (C) phosphoric acid ester compound having a radical polymerizable group is not particularly limited, and examples thereof include one or more compounds selected from the group consisting of 2-hydroxymethyl(meth)acrylate acid phosphate, 2-hydroxyethyl(meth)acrylate acid phosphate, 2-hydroxypropyl(meth)acrylate acid phosphate, ethylene oxide-modified di(meth)acrylate phosphoric acid, ethylene oxide-modified tri(meth)acrylate phosphoric acid, and caprolactone-modified ethylene oxide-modified di(meth)acrylate phosphoric acid.

[0026] The (C) phosphate ester compound having a radical polymerizable group may be synthesized or may be a commercially available product, such as one or more selected from the group consisting of Light Ester PA, P-1M, and P-2M (all manufactured by Kyoeisha Chemical Co., Ltd.), Kayamar PM-1 (manufactured by Nippon Kayaku Co., Ltd.), and JPA-514 (manufactured by Johoku Chemical Industry Co., Ltd.).

[0027] The amount of the (C) phosphate ester compound having a radical polymerizable group blended is 0.055 parts by mass or more but less than 1 part by mass per 100 parts by mass of the (A) radical polymerizable compound, preferably 0.06 parts by mass or more, more preferably 0.065 parts by mass or more, even more preferably 0.07 parts by mass or more, and preferably 0.8 parts by mass or less, more preferably 0.7 parts by mass or less. By adjusting the blending amount of (C) the phosphate ester compound having a radical polymerizable group to 0.055 parts by mass or more but less than 1 part by mass per 100 parts by mass of (A) the radical polymerizable compound, the adhesive strength to steel plate (tensile shear adhesive strength based on JIS K 6850 (1999)) can be increased to 2.0 N / mm 2 Furthermore, the set time (defined in the examples) can be less than 300 seconds, preferably less than 250 seconds, and more preferably less than 180 seconds. If the amount of (C) phosphate ester compound having a radical polymerizable group is 1 part by mass or more, the tensile shear bond strength will be high and the adhesiveness will be excellent, but the setting time will be long and the curing rate may be slow. If the amount is less than 0.055 parts by mass, the setting time will be short and the curing rate will be fast, but the tensile shear bond strength will be low and the adhesiveness may be poor.

[0028] ((D) Anaerobic curing catalyst) The radically polymerizable adhesive composition used in the method for producing a steel sheet laminate of the present invention preferably further contains (D) an anaerobic curing catalyst. (D) The anaerobic curing catalyst may be one or more compounds selected from the group consisting of imide compounds, amine compounds, azole compounds, mercaptan compounds, hydrazine compounds, etc. Among these, imide compounds are preferred from the viewpoint of improving anaerobic curing properties.

[0029] The imide-based compound is represented by the following formula (3) or (4): -CONHCO- (3) -CONHSO2- (4) or a salt thereof. Examples of the imide-based compound include one or more selected from the group consisting of o-benzoic acid sulfimide (saccharin), succinimide, phthalimide, and salts thereof (particularly alkali metal salts such as sodium and potassium).

[0030] Examples of the amine compound include one or more compounds selected from the group consisting of heterocyclic secondary amines such as 1,2,3,4-tetrahydroquinoline and 1,2,3,4-tetrahydroquinaldine, heterocyclic tertiary amines such as quinoline, methylquinoline, quinaldine and quinoxalinephenazine, and aromatic tertiary amines such as N,N-dimethyl-anisidine and N,N-dimethylaniline.

[0031] Examples of the azole compound include one or more selected from the group consisting of 1,2,4-triazole, oxazole, oxadiazole, thiadiazole, benzotriazole, hydroxybenzotriazole, benzoxazole, 1,2,3-benzothiadiazole, and 3-mercaptobenzotriazole.

[0032] Examples of the mercaptan compound include one or more compounds selected from the group consisting of linear mercaptans such as n-dodecyl mercaptan, ethyl mercaptan, and butyl mercaptan.

[0033] Examples of the hydrazine compound include 1-acetyl-2-phenylhydrazine, 1-acetyl-2-(p-tolyl)hydrazine, 1-benzoyl-2-phenylhydrazine, 1-(1',1',1'-trifluoro)acetyl-2-phenylhydrazine, 1,5-diphenyl-carbohydrazine, 1-formyl-2-phenylhydrazine, 1-acetyl-2-(p-bromophenyl)hydrazine, 1-acetyl-2-(p-nitrophenyl)hydrazine, 1-acetyl-2-(p-methoxyphenyl)hydrazine, 1-acetyl-2-(2'-phenylethylhydrazine), p-nitrophenylhydrazine, p-trisulfonylhydrazide, 1-acetyl-2-methylhydrazine, 1-phenylsemicarbazide, 2-phenyl-t-butylcarbazate, succinic acid di(phenylhydrazide), and the like.

[0034] The amount of the (D) anaerobic curing catalyst is not particularly limited, as long as it does not impair the properties of the radical-polymerizable adhesive composition, such as ease of handling, adhesive strength, rapid curing, and storage stability. It is, for example, 0.1 parts by mass or more, preferably 0.5 parts by mass or more, and for example, 5 parts by mass or less, preferably 3 parts by mass or less, per 100 parts by mass of the (A) radical-polymerizable compound. By setting the amount of the (D) anaerobic curing catalyst to be in the range of 0.1 parts by mass or more and 5 parts by mass or less, per 100 parts by mass of the (A) radical-polymerizable compound, the radical-polymerizable adhesive composition can be made excellent in anaerobic curing properties and storage stability.

[0035] ((E) Storage stabilizer) The radically polymerizable adhesive composition used in the method for producing a steel sheet laminate of the present invention preferably further contains (E) a storage stabilizer, such as one or more selected from the group consisting of polymerization inhibitors (radical scavengers, metal chelating agents), antioxidants, etc.

[0036] Examples of the polymerization inhibitor include one or more metal chelating agents selected from the group consisting of ethylenediaminetetraacetic acid, its di-sodium salt, its tetra-sodium salt, oxalic acid, acetylacetone, o-aminophenol, and the like; one or more quinone compounds selected from the group consisting of hydroquinone, benzoquinone, hydroquinone monomethyl ether, β-naphthoquinone, 2-methoxy-1,4-naphthoquinone, methylhydroquinone, hydroquinone monomethyl ether, mono-tert-butylhydroquinone, 2,5-di-tert-butylhydroquinone, p-benzoquinone, 2,5-diphenyl-p-benzoquinone, 2,5-di-tert-butyl-p-benzoquinone, and the like; pentaerythritol tetrakis(3-(3,5-ditert-butyl)-4-benzoquinone; Examples of the compound include one or more hindered phenol compounds selected from the group consisting of N-methyl-N-nitrosoaniline, N-nitrosodiphenylamine, N-nitrosophenylhydroxyamine aluminum salt, and the like; hindered amine compounds; one or more nitrosamine compounds selected from the group consisting of N-methyl-N-nitrosoaniline, N-nitrosodiphenylamine, N-nitrosophenylhydroxyamine aluminum salt, and the like; phosphorus compounds such as triphenyl phosphite; and one or more compounds selected from the group consisting of phenothiazine, N-isopropyl-N'-phenyl-p-phenylenediamine, diethylhydroxylamine, sulfur, t-butylcatechol, potassium triiodide, and the like.

[0037] The amount of the storage stabilizer (E) to be added is not particularly limited and can be, for example, 7 parts by mass or less, preferably 0.001 to 5 parts by mass, per 100 parts by mass of the (meth)acrylic polymerizable monomer (A).

[0038] ((F) Other ingredients) The radically polymerizable adhesive composition used in the method for producing a steel sheet laminate of the present invention may contain (F) other components in addition to (A) the radically polymerizable compound, (B) the organic peroxide, (C) the phosphate ester compound having a radically polymerizable group, (D) the anaerobic curing catalyst, and (E) the storage stabilizer, as long as the functions of the adhesive composition, such as curability and the adhesiveness of the cured product, are not impaired. Examples of (F) other components include one or more selected from the group consisting of organic fillers (elastomers, thermoplastic resins, thermosetting resins, etc.), inorganic fillers, silane coupling agents, cure rate modifiers, plasticizers, antifoaming agents, heavy metal deactivators, adhesives and / or tackifiers, antioxidants, light stabilizers, reinforcing agents, colorants, flame retardants, rust inhibitors, dispersants, thixotropic agents, anti-precipitation agents, antioxidants, ultraviolet absorbers, fragrances, and the like.

[0039] Examples of organic fillers include one or more selected from the group consisting of polyethylene, polypropylene, polyamide, cross-linked acrylic, cross-linked polystyrene, polyester, polyvinyl alcohol, polyvinyl butyral, polycarbonate, epoxy resin, various rubbers and elastomers (diene-based rubbers, olefin-based elastomers, urethane-based elastomers, silicone-based elastomers, etc.).

[0040] Examples of inorganic fillers include one or more selected from the group consisting of glass, silica, alumina, mica, ceramics, calcium carbonate, aluminum nitride, carbon powder, kaolin clay, dried clay minerals, dried diatomaceous earth, and the like.

[0041] The silane coupling agent is used as an adhesion promoter. Examples of the silane coupling agent include one or more selected from the group consisting of γ-chloropropyltrimethoxysilane, octenyltrimethoxysilane, glycidoxyoctyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine, N-phenyl-γ-aminopropyltrimethoxysilane, γ-(meth)acryloxypropyltrimethoxysilane, γ-(meth)acryloxypropyltriethoxysilane, γ-isocyanatepropyltriethoxysilane, γ-ureidopropyltriethoxysilane, and p-styryltrimethoxysilane.

[0042] (Properties of the radically polymerizable adhesive composition or its cured product) {Tensile shear adhesive strength} The tensile shear adhesive strength of the radical polymerizable adhesive composition of the present invention is, for example, 2.0 N / mm or more, preferably 3.0 N / mm 2 The tensile shear bond strength can be measured by the method described in the Examples below.

[0043] {Set Time} The setting time of the radically polymerizable adhesive composition of the present invention is, for example, less than 300 seconds, preferably less than 250 seconds, and more preferably less than 180 seconds. The setting time can be obtained by the method described in the Examples below.

[0044] {glass transition temperature} The glass transition point of the cured product of the radically polymerizable adhesive composition of the present invention is, for example, 60° C. or higher, preferably 70° C. or higher, from the viewpoint of the heat resistance of the steel sheet laminate. The glass transition temperature can be determined, for example, by the following method.

[0045] A mixture of 100 parts by mass of the radically polymerizable adhesive composition and 0.3 parts by mass of the primer described below is poured between two PET films spaced 1 mm apart to produce a cured product. A sample measuring 10 mm wide x 40 mm long is cut out from the obtained cured product, and measurement is performed using a Seiko Instruments Inc. DMS6100 in a tensile mode at a temperature range of 25°C to 350°C, a heating rate of 5°C / min, and a frequency of 1 Hz to determine the peak value of tanδ, which is taken as the glass transition point.

[0046] {viscosity} The viscosity of the radically polymerizable adhesive composition used in the method for producing a steel sheet laminate of the present invention is not particularly limited, and from the viewpoints of ease of handling and prevention of extrusion during adhesion, it can be, for example, 0.01 Pa s or more, preferably 0.05 Pa s or more, and more preferably 0.5 Pa s or more, and can be, for example, 50 Pa s or less, preferably 30 Pa s or less, and more preferably 15 Pa s or less. The viscosity can be adjusted by a viscosity adjusting method known in the adhesive field, such as blending a viscosity adjuster (thixotropic agent). The viscosity can be obtained, for example, by putting 100 g of the radically polymerizable adhesive composition into a bottle, discharging it into a measuring cup, and measuring it using a Brookfield viscometer (manufactured by Toki Sangyo Co., Ltd.) at 25°C and a rotation speed of 60 rpm.

[0047] (Method of manufacturing adhesive composition) The method for producing the radical polymerizable adhesive composition used in the method for producing the steel sheet laminate of the present invention is not particularly limited. For example, the composition can be produced by adding predetermined amounts of at least (A) the radical polymerizable compound, (B) the organic peroxide, and (C) the phosphate ester compound having a radical polymerizable group to a mixing vessel in any order and mixing them.

[0048] For mixing, a mixing device such as a mixer (rotating / revolving mixer, planetary mixer, etc.), a tumbler, a stirrer, an agitator, a mechanical homogenizer, an ultrasonic homogenizer, a high-pressure homogenizer, a shaker, a V-type blender, or a Nauta mixer can be used, and it is preferable to use a mixer. The mixing conditions are not particularly limited. The temperature conditions can be, for example, 0°C or higher, preferably 10°C or higher, and can be, for example, 100°C or lower, more preferably 70°C or lower. The mixing time can be, for example, 1 minute or longer, preferably 5 minutes or longer, and can be, for example, 10 hours or shorter, preferably 5 hours or shorter.

[0049] <Primer containing copper compounds> The primer used in the method for producing the steel sheet laminate of the present invention contains a copper compound. The primer may contain, in addition to the copper compound, oil, solvent, rust inhibitor, preservative, and the like.

[0050] Examples of the copper compound include one or more compounds selected from the group consisting of copper salts of carboxylic acids such as copper neodecanoate, copper 2-ethylhexanoate, copper naphthenate, copper octenoate, copper hexanoate, copper propionate, and copper 2,4-pentadionate (copper acetylacetonate); copper complexes such as ethylenediamine copper and propylenediamine copper; and the like.

[0051] As the oil, punching oil, mineral oil, synthetic oil, animal or vegetable oil, etc. can be used. In the present invention, since the step of punching steel sheets into a desired shape and the step of laminating the punched steel sheets to form a steel sheet laminate are carried out consecutively, it is preferable that the primer contains punching oil. By including punching oil, it is possible to prevent the occurrence of galling, seizure, etc. during various processing of the steel sheets.

[0052] The solvent may be one or more organic solvents and / or water. The organic solvent is not particularly limited. For example, it may be one or more selected from the group consisting of aliphatic hydrocarbon organic solvents having 5 to 40 carbon atoms (hexane, heptone, paraffin, etc.); alicyclic hydrocarbon solvents having 5 to 20 carbon atoms; aromatic hydrocarbon solvents having 6 to 20 carbon atoms (benzene, toluene, xylene, ethylbenzene, indene, etc.); alcohol solvents having 1 to 10 carbon atoms (methanol, ethanol, propanol, isopropanol, hexanol, etc.); ketone solvents having 3 to 20 carbon atoms (acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, etc.); ether solvents having 2 to 20 carbon atoms (tetrahydrofuran, diethyl ether, dioxane, ethyl cellosolve, propylene glycol monomethyl ether, etc.); and ester solvents having 2 to 20 carbon atoms (methyl acetate, ethyl acetate, butyl acetate, etc.).

[0053] The composition of the primer is not particularly limited. The copper compound is, for example, 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and for example, 15.0% by mass or less, preferably 10.0% by mass or less, and more preferably 8.0% by mass or less, when the total amount of the primer is taken as 100% by mass. The oil is, for example, 20.0% by mass or more, preferably 25.0% by mass or more, more preferably 30.0% by mass or more, and for example, 80.0% by mass or less, preferably 70.0% by mass or less, and more preferably 60.0% by mass or less, when the total amount of the primer is taken as 100% by mass. The solvent is used in an amount such that the total amount becomes 100% by mass.

[0054] <Steel plate> The steel sheet used in the method for producing the steel sheet laminate of the present invention is not particularly limited. Various steel sheets can be used depending on the application, etc. In the present invention, steel sheets that are distributed in a rolled state can be used as they are without degreasing.

[0055] Examples of steel sheets include various iron steel sheets. Among these, cold-rolled steel sheets, electromagnetic steel sheets, etc. are preferably used. In the present invention, the electromagnetic steel sheets are preferably steel sheets that are used mainly for components such as rotors and stators of motors, taking advantage of the electromagnetic properties of the steel sheets.

[0056] The thickness of the steel plate is not particularly limited and can be determined appropriately depending on the application, etc. For example, it is 0.01 mm or more, preferably 0.1 mm or more, and for example, 5 mm or less, preferably 3 mm or less, more preferably 1 mm or less. In addition, the thickness of the cured product of the radical polymerizable adhesive composition layer in the steel plate laminate is not particularly limited.

[0057] The shape of the steel sheets to be laminated is not particularly limited. In the present invention, it is preferable to form a steel sheet laminate by laminating steel sheets punched into a predetermined shape from a strip-shaped steel sheet to which the radical polymerizable adhesive composition and a primer have been applied. In particular, the magnetic steel sheet laminate can be formed by laminating, for example, two or more, preferably five or more, strip-shaped magnetic steel sheets punched into a predetermined shape.

[0058] (Steel plate laminate manufacturing equipment) FIG. 1 shows an embodiment of a steel sheet stack manufacturing apparatus used in the method for manufacturing a steel sheet stack according to the present invention. In FIG. 1 , in a steel plate laminate manufacturing apparatus 1, a steel strip 3 is unwound from a steel strip roll 2. A primer containing punching oil is applied to one side of the steel strip 3 by a primer application device 4A, and an adhesive is applied to the other side of the steel strip 3 by an adhesive application device 4B. After that, the steel strip 3 is introduced into a press molding device 5. In the press molding device 5, by providing inner diameter / hole / slot punching punch units 6A, 6B, 6C, 6D, and 6E as needed, it is possible to perform one or more of the punching processes of inner diameters, holes, slots, etc. on the steel strip 3. The order of the punching processes of inner diameters, holes, slots, etc. is not particularly limited. After the punching processes of inner diameters, holes, slots, etc., the steel strip 3 is punched into a steel plate laminate forming member by an outer diameter punching punch unit 7 in the press molding device 5. The punched steel plate laminate forming members are stored in a steel plate laminate forming member storage and holding section 8, and the primer layer and adhesive layer come into contact with each other to bond the steel plate laminate forming members one by one, and a predetermined number of sheets are stacked and bonded together to produce a steel plate laminate 9. The obtained steel plate laminate 9 is taken out from the steel plate laminate forming member storage and holding section 8. If necessary, heat treatment may be carried out using a thermostatic bath, far-infrared heater, or the like, for the purpose of heating to ensure curing of the adhesive. The heating conditions at this time may be, for example, a temperature of 40°C or higher and 300°C or lower, and a time of 10 minutes to 5 hours.

[0059] In the steel plate laminate manufacturing apparatus 1 in Figure 1, a primer and an adhesive are simultaneously applied to the strip steel plate 3 by a primer application device 4A and an adhesive application device 4B, but the adhesive application device 4B can be provided upstream of the outer diameter punching section 7 (at any position before the outer diameter punching is performed). In the steel plate laminate manufacturing apparatus 1 in Figure 1, the surfaces of each punch section 6A, 6B, 6C, 6D, 6E, and 7 that punch out the strip steel plate 3 and the surfaces of the components that make up the conveying line for the strip steel plate 3 may be subjected to a surface treatment (anti-adhesion treatment) to prevent the primer and / or radical polymerizable adhesive composition applied to the strip steel plate 3 from adhering. In the steel plate laminate manufacturing apparatus 1, it is preferable to use a primer containing punching oil in order to improve the workability of the punching process and prevent galling, seizure, and the like.

[0060] 1, punching units 6A, 6B, 6C, 6D, and 6E are provided as punching units for punching inner diameters / holes / slots, etc., but the number of punching units can be increased or decreased as needed. For example, the number of punching units can be increased to improve punching accuracy. 1, the positions of the primer applicator 4A and the adhesive applicator 4B are not particularly limited. The primer applicator 4A can also be provided below the strip-shaped steel plate 3. In the steel sheet laminate manufacturing apparatus 1 shown in Fig. 1, the coating method in the primer coating device 4A and the adhesive coating device 4B is not particularly limited, and examples thereof include one or more coating methods including roller coating, dispense coating, spray coating, inkjet coating, dipping, brush coating, etc. In the steel plate stack manufacturing apparatus 1 shown in Figure 1, instead of unwinding a strip steel plate 3 from a strip steel plate roll 2, a steel plate that has been pre-formed into a predetermined shape can be continuously supplied to manufacture a steel plate stack.

[0061] [Steel plate laminate] The steel sheet laminate of the present invention is obtained by the [method for producing a steel sheet laminate]. In the present invention, the steel sheet laminate is preferably formed using electrical steel sheets coated with a primer containing a copper compound and a radically polymerizable adhesive composition, or the steel sheet laminate is preferably formed using electrical steel sheets punched into a predetermined shape from a strip steel sheet.

[0062] The thickness of the steel sheets used in the steel sheet laminate is not particularly limited, and is, from the viewpoint of the need for thinner steel sheet laminates in line with the miniaturization of motors and the like, in the range of, for example, 0.01 mm or more, preferably 0.1 mm or more, and for example, 3.0 mm or less, preferably 1.0 mm or less. The thickness of the adhesive layer (cured product of the radically polymerizable adhesive composition) when the steel sheet laminate is constructed is not particularly limited, and is, for example, 0.1 μm or more, preferably 0.5 μm or more, and for example, 1000 μm or less, preferably 500 μm or less. The number of stacked steel sheets is not particularly limited, and is, for example, 2 or more, preferably 3 or more, and is, for example, 5000 or less, for example, 3000 or less, for example, 1000 or less, or for example, 800 or less.

[0063] In the steel sheet laminate of the present invention, particularly in the steel sheet laminate using electrical steel sheets, the cured adhesive layer functions as an insulating layer and also as a buffer layer for the stress of the steel sheets. When the steel sheet laminate of the present invention is used in the rotor, stator, etc. of a motor, it is possible to reduce current loss, stress concentration, and stress distortion, making it possible to form a highly efficient, high-performance, and highly reliable motor.

[0064] A motor using the steel sheet laminate of the present invention as a core of a rotor and / or stator, etc., can be used as one or more types of motor selected from the group consisting of automobile drive motors, motors for adjusting the focus of cameras, drive motors for hard disks, motors built into computers, mobile terminals, mobile phones, etc.

[0065] [Adhesive composition] The adhesive composition according to the present invention is an adhesive composition for a steel sheet laminate for bonding steel sheets coated with a primer containing a copper compound, (A) a radical polymerizable compound, (B) an organic peroxide, and (C) a phosphate ester compound having a radical polymerizable group, The adhesive composition comprises (C) a phosphoric acid ester compound having a radical polymerizable group in an amount of 0.055 parts by mass or more and less than 1 part by mass per 100 parts by mass of (A) the radical polymerizable compound. The adhesive composition, primer, and steel sheet are the same as those described in the <Radical polymerizable adhesive composition>, <Primer containing a copper compound>, and <Steel sheet> sections of the above [Method for producing a steel sheet laminate].

[0066] The adhesive composition of the present invention is useful for bonding various steel sheets, such as cold-rolled steel sheets and electrical steel sheets, to produce steel sheet laminates. When bonding steel sheets together, particularly when bonding steel sheets having coatings containing punching oil and copper compounds formed on their surfaces, the adhesive composition can significantly shorten the set time (the time it takes for the bonded steel sheets to become fixed and immobile). The set time can be measured using the method described in the Examples below, and can be, for example, less than 300 seconds, preferably less than 250 seconds, and more preferably less than 180 seconds. In a steel sheet laminate produced using the adhesive composition of the present invention, particularly a steel sheet laminate using electrical steel sheets, the cured adhesive layer functions as an insulating layer and also functions as a buffer layer for the stress of the steel sheets. Therefore, when the steel sheet laminate is used in a rotor, stator, etc. of a motor, current loss, stress concentration, and stress distortion can be reduced, making it possible to form a highly efficient, high-performance, and highly reliable motor. [Example]

[0067] The present invention will be specifically described with reference to the following examples, but the present invention is not limited to these examples. In each example, unless otherwise specified, "parts" means "parts by mass" and "%" means "% by mass." In addition, all descriptions relating to blending ratios in the tables are in "parts by mass."

[0068] [Constituents of adhesive composition] In the Examples and Comparative Examples shown in Tables 1 to 3, the components of the adhesive compositions are as follows. EP-MA: epoxy methacrylate (a mixture of 60% by mass of epoxy methacrylate and 40% by mass of HEMA) (manufactured by DIC Corporation, "UE-8071-60BH") BPA-MA: ethylene oxide adduct of bisphenol A (approximately 2.6 moles) dimethacrylate (Kyoeisha Chemical Co., Ltd., "Light Ester BP-2EMK") PUA1: Polyurethane (meth)acrylate oligomer (Mitsubishi Chemical Corporation, "Shiko UV-1700") PUA2: Polyurethane (meth)acrylate oligomer (Mitsubishi Chemical Corporation, "Shiko UV-3700B") HEMA: Hydroxyethyl methacrylate IBXMA: Isobornyl methacrylate TCDDA: dimethylol-tricyclodecane diacrylate CHPO: Cumene hydroperoxide PM1: Monofunctional phosphate monomer (Kyoeisha Chemical Co., Ltd., "Light Ester P-1M") PM2: Polyfunctional phosphate monomer (Kyoeisha Chemical Co., Ltd., "Light Ester P-2M") SAC: Saccharin (anaerobic catalyst) EDTA2Na: Ethylenediaminetetraacetic acid disodium salt (stabilizer)

[0069] [Adhesive property evaluation] <Preparation of test steel plates> A cold-rolled steel sheet having a thickness of 0.5 mm conforming to JIS G 3141 was cut to a size of 25 mm width x 100 mm length (W25mm x L100mm) to prepare a cold-rolled steel sheet for testing. Test electrical steel sheets were prepared in the same manner as in the preparation of test cold-rolled steel sheets, except that a 0.25 mm thick electrical steel sheet (thin Hi-X Core 25HX1500, manufactured by Nippon Steel Corporation) was used instead of the cold-rolled steel sheet.

[0070] <Primer preparation> 0.6 parts of a 60% toluene solution of copper neodecanoate, 49.4 parts of ethanol, and 50 parts of sheet metal punching oil (manufactured by Nippon Kogyo Oil Co., Ltd., "G-6338F") were mixed in a glass container to obtain a primer.

[0071] <Cold-rolled steel sheet tensile shear adhesive strength> Two cold-rolled steel sheets were prepared for testing. One sheet was sprayed with 0.018 ml of primer and left to dry at 25°C for 3 hours. The other sheet was coated with 0.03 ml of adhesive with a spatula, and the primer-coated surface and adhesive-coated surface were bonded together so that the bonding area was 25 mm wide x 12.5 mm long. The two test pieces were then compressed in an air press for 200 seconds and removed to prepare a test piece (corresponding to a steel sheet laminate). The prepared test pieces were aged in an environment of 23°C for 24 hours and then pulled at a pulling rate of 0.5 mm / min using a universal tensile tester, and the tensile shear adhesive strength (N / mm2) of the cold-rolled steel sheet was obtained based on JIS K 6850 (1999).

[0072] <Cold-rolled steel sheet set time> Two cold-rolled steel sheets for testing were prepared, each measuring 25 mm wide and 100 mm long. 0.018 ml of primer was sprayed onto one end of one of the cold-rolled steel test sheets in the longitudinal direction, and the sheet was left to dry at 25°C for 3 hours. 0.03 ml of adhesive was applied with a spatula to one end of the other cold-rolled steel plate in the longitudinal direction. Immediately after applying the adhesive, the primer-coated surface and adhesive-coated surface of the test cold-rolled steel sheet were bonded together so that the bonding area was 25 mm wide x 12.5 mm long. Thereafter, the two bonded cold-rolled steel sheets for testing were pressed with an air press for a predetermined time and then removed to prepare a test piece (corresponding to a steel sheet laminate). Immediately after preparing the test specimens, one of the test cold-rolled steel plates was fixed in place, a 5 kg weight was hung from the other test cold-rolled steel plate, and a tensile shear load was applied parallel to the adhesive surface. It was then visually confirmed whether the adhesive joint of the test specimens had fractured. The time from when the test piece was pressed with the air press to when the pressure was released was defined as the air press time, and the air press time when the bonded surface of the test piece no longer broke was defined as the set time. The weight was hung for 10 seconds. For example, if the test piece is compressed with an air press for 20 seconds, removed, and then a 5 kg weight is hung immediately after preparation, the bonded surface of the test piece will break; on the other hand, if the test piece is compressed with an air press for 30 seconds, removed, and then a 5 kg weight is hung immediately after preparation, the set time will be 30 seconds if the bonded surface of the test piece does not break.

[0073] <Tensile shear adhesive strength of electrical steel sheets> Two test electrical steel sheets were prepared, each measuring 25 mm wide and 100 mm long. 0.018 ml of primer was sprayed onto one end of one of the test electrical steel sheets in the longitudinal direction, and the sheet was left to dry at 25°C for 3 hours. 0.03 ml of adhesive was applied with a spatula to one end of the other test electromagnetic steel sheet in the longitudinal direction. Immediately after applying the adhesive, the primer-coated surface and adhesive-coated surface of the test magnetic steel sheet were bonded together so that the bonding area was 25 mm wide x 12.5 mm long. Thereafter, the two bonded test magnetic steel sheet laminates were compressed with an air press for 200 seconds and then removed to prepare test specimens. The prepared test specimen was cured in an environment of 23°C for 24 hours, and then pulled in a direction parallel to the adhesive surface at a pulling speed of 0.5 mm / min using a universal tensile testing machine to measure the tensile shear adhesive strength of the magnetic steel sheet (N / mm 2 ) was obtained based on JIS K 6850 (1999).

[0074] <Electromagnetic steel sheet setting time> Two test electrical steel sheets were prepared, each measuring 25 mm wide and 100 mm long. 0.018 ml of primer was sprayed onto one end of one of the cold-rolled steel test sheets in the longitudinal direction, and the sheet was left to dry at 25°C for 3 hours. 0.03 ml of adhesive was applied with a spatula to one end of the other cold-rolled steel plate in the longitudinal direction. Immediately after applying the adhesive, the primer-coated surface and adhesive-coated surface of the test electromagnetic steel sheet were bonded together so that the bonding area was 25 mm wide x 12.5 mm long. Thereafter, the two bonded test magnetic steel sheet laminates were pressed with an air press for a predetermined time and then removed to prepare test specimens. Immediately after preparing the test specimens, one of the test cold-rolled steel plates was fixed in place, a 5 kg weight was hung from the other test cold-rolled steel plate, and a tensile shear load was applied parallel to the adhesive surface. It was then visually confirmed whether the adhesive joint of the test specimens had fractured. The time from when the test piece was pressed with the air press to when the pressure was released was defined as the air press time, and the air press time when the bonded surface of the test piece no longer broke was defined as the set time. The weight was hung for 10 seconds. For example, if a test piece is compressed with an air press for 20 seconds, removed, and then a 5 kg weight is hung immediately after preparation, the bonded surface of the test piece will break; on the other hand, if a test piece is compressed with an air press for 30 seconds, removed, and then a 5 kg weight is hung immediately after preparation, the bonded surface of the test piece will not break, and the set time will be 30 seconds.

[0075] [Examples 1 to 5] Each component shown in Table 1 was taken in the amount (parts by mass) shown in Table 1 and mixed in a glass container to prepare an adhesive composition. The adhesive composition thus obtained was used to measure the cold-rolled steel sheet tensile shear bond strength, cold-rolled steel sheet set time, and electrical steel sheet tensile shear bond strength and electrical steel sheet set time. The results are also shown in Table 1.

[0076] [Examples 6 to 12] Each component shown in Table 2 was taken in the amount (parts by mass) shown in Table 2 and mixed in a glass container to prepare an adhesive composition. The resulting adhesive composition was used to measure the tensile shear adhesive strength and set time of the cold-rolled steel sheet. The results are shown in Table 2.

[0077] [Comparative Examples 1 to 7] Each component shown in Table 3 was taken in the amount (parts by mass) shown in Table 3 and mixed in a glass container to prepare an adhesive composition. The adhesive composition thus obtained was used to measure the tensile shear adhesive strength and the set time of the cold-rolled steel sheet. The results are shown in Table 3.

[0078] [Table 1]

[0079] [Table 2]

[0080] [Table 3]

[0081] Examples 1 to 5 in Table 1 and Examples 6 to 12 in Table 2 show that the method for producing a steel sheet laminate and the radically polymerizable adhesive composition of the present invention exhibit excellent tensile shear bond strength and fast curing properties (set time of less than 300 seconds) when used to form a steel sheet laminate using steel sheets (cold-rolled steel sheets and electromagnetic steel sheets) having punching oil on their surfaces.

[0082] Comparative Examples 1 to 7 in Table 3 show that when a steel sheet laminate is formed using steel sheets (cold-rolled steel sheets and electromagnetic steel sheets) having punching oil on their surfaces, the manufacturing method for a steel sheet laminate and the radical-polymerizable adhesive composition of the present invention are not satisfactory in terms of tensile shear bond strength and / or fast curing properties (set time of less than 300 seconds) because the blending amount of (C) the phosphate ester compound having a radical-polymerizable group is outside the range of the present invention. [Explanation of symbols]

[0083] 1. Steel plate laminate manufacturing equipment, 2. Steel strip roll 3 Steel strips 4A Primer Coating Device 4B Adhesive application device 5 Press molding equipment 5A Press molding device upper part 5B Press molding device bottom 6A, 6B, 6C, 6D, 6E Punching part for punching inner diameter / hole / slot etc. 7. Outer diameter punching section 8. Steel plate stack forming member storage and holding section 9 Steel plate laminate

Claims

1. A method for producing a steel sheet laminate, comprising bonding steel sheets coated with a primer containing a copper compound using a radical-polymerizable adhesive composition containing (A) a radical-polymerizable compound, (B) an organic peroxide, and (C) a phosphate ester compound having a radical-polymerizable group, wherein the amount of (C) the phosphate ester compound having a radical-polymerizable group is 0.055 parts by mass or more and less than 1 part by mass per 100 parts by mass of the (A) radical-polymerizable compound.

2. A steel sheet stack produced by the method of claim 1.

3. An adhesive composition for a steel sheet laminate that bonds steel sheets coated with a primer containing a copper compound, comprising: (A) a radically polymerizable compound, (B) an organic peroxide, and (C) a phosphate ester compound having a radically polymerizable group, An adhesive composition, in which the amount of (C) the phosphate ester compound having a radical polymerizable group is 0.055 parts by mass or more and less than 1 part by mass per 100 parts by mass of (A) the radical polymerizable compound.

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