Adhesive composition, article, and motor

Abstract

An adhesive composition according to the present invention contains a polymerizable monomer (A) and an elastomer (B), and is used for the adhesion to a zinc-containing metal. The polymerizable monomer (A) includes a monofunctional alkyl (meth)acrylate (A1) having an alicyclic structure, and has a tensile shear strength of 4.0 MPa or more and 10 MPa or less as measured by a prescribed procedure 1.

Description

Adhesive composition, article and motor

[0001] The present invention relates to an adhesive composition, an article and a motor.

[0002] Demand for in-vehicle motors for driving wheels of electric vehicles and hybrid vehicles has been expanding. Adhesives are used in motors for the purpose of fixing magnets. The adhesives are used, for example, for bonding a rotor and a magnet, bonding a stator of a motor and a magnet, and the like.

[0003] Examples of techniques related to adhesives for motors or adhesives for automobiles include those described in the following Patent Documents 1 to 3.

[0004] Patent Document 1 aims to provide a radical-curable resin composition that is excellent in adhesive strength to metal members such as magnets and can provide a cured product free from cracks or peeling even after a thermal cycle test required for in-vehicle components, which is characterized by comprising: component (A): a vinyl polymer having a terminal (meth)acrylic group; component (B): a radically polymerizable monomer selected from the group consisting of isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, adamantyl (meth)acrylate, acryloylmorpholine, dimethylacrylamide, and diethylacrylamide; component (C): a (meth)acrylate or (meth)acrylic acid having a phosphate group; component (D): a radical initiator, wherein the component (B) is contained in an amount of 5 to 140 parts by mass relative to 100 parts by mass of the component (A). A radical-curable resin composition as described above is disclosed therein.

[0005] Patent Document 2 describes a composition containing the following (A) to (D), which is intended for use as an adhesive used in automobile manufacturing: (A) urethane (meth)acrylate having a number average molecular weight of 5000 or more, in an amount of 40 to 75 parts by mass relative to 100 parts by mass of the total of (A) and (B); (B) a (meth)acrylic compound containing (B-1) a (meth)acrylate having no urethane bond and (B-2) (meth)acrylic acid in an amount of 15 to 25 parts by mass relative to 100 parts by mass of the total of (A) and (B); (C) a polymerization initiator; (D) a reducing agent.

[0006] Patent Document 3 describes a two-component adhesive comprising a first agent containing a free radical initiator and a second agent containing a reducing agent. This two-component adhesive contains a first monomer which is methyl methacrylate and a second monomer selected from the group consisting of methacrylic acid, aromatic polyols or their derivatives, polyfunctional (meth)acrylic acid adducts, and combinations thereof. The overlapping shear strength of the cured product of this two-component adhesive is 20 MPa or more at 25°C and 7 MPa or more at 120°C, the adhesive strength measured by a T-type peel test at 25°C is 2 kN / m or more, and the glass transition temperature is 130°C or higher.

[0007] Japanese Patent Publication No. 2017-186439, International Publication No. 2020 / 100832, Japanese Patent Publication No. 2016-155892

[0008] Motor adhesives are exposed to high-temperature environments in engine compartments and other locations. However, they may also be exposed to low-temperature environments when the motor is not operating or depending on the motor's operating environment. Furthermore, because a strong centrifugal force from the motor constantly applies tensile force, high adhesive strength is required even when heat is applied. However, with the increasing power output and rotational speed of motors leading to higher operating temperatures, motor adhesives require further improvement in adhesive strength against prolonged high temperatures.

[0009] The present invention has been made in view of the above circumstances, and aims to provide an adhesive composition with improved adhesive strength under long-term heat, as well as articles and motors using the adhesive composition.

[0010] The inventors diligently conducted research to achieve the above objectives. As a result, they discovered that it is effective to use a monofunctional alkyl (meth)acrylate (A1) having an alicyclic structure in an adhesive composition used for bonding to zinc-containing metals, and to control the adhesive composition so that it has a predetermined tensile shear strength, thus completing the present invention.

[0011] According to the present invention, the following adhesive compositions, articles, and motors are provided.

[0012] [1] An adhesive composition comprising a polymerizable monomer (A) and an elastomer (B), used for bonding to zinc-containing metals, wherein the polymerizable monomer (A) comprises a monofunctional alkyl (meth)acrylate (A1) having an alicyclic structure, and the tensile shear strength measured in the following procedure 1 is 4.0 MPa or more and 10 MPa or less. <Procedure 1> (1) Prepare an electro-galvanized magnet (25 mm × 50 mm × 3 mm) whose surface has been degreased with acetone, and a carbon steel plate (JIS G3141 (SPCC-SD, 25 mm × 100 mm × 1.5 mm) and bond them together using the adhesive composition under the following conditions i to obtain a laminate. (Condition i) - Thickness of the cured layer of the adhesive composition: 0.1 mm - Bonding area: 25 × 12.5 mm ２- Bonding atmosphere: 23±2℃, 50±10%RH - Curing conditions for adhesive composition: 23±2℃, 50±10%RH × 24hrs (2) Next, the obtained laminate is held in a heat shock tester, held at -20℃ for 45 minutes, then heated to 130℃, held at 130℃ for 45 minutes, and then cooled again to -20℃. This cycle is repeated 252 times. (3) After that, using a tensile tester, the tensile shear strength (MPa) of the bonding surface between the electro-galvanized magnet and the carbon steel sheet is measured under the conditions of 130℃, chuck distance of 100 mm, and tensile speed of 10 mm / min. [2] The adhesive composition according to [1], wherein the content of monofunctional alkyl (meth)acrylate (A1) having an alicyclic structure is 70 parts by mass or more and 99 parts by mass or less per 100 parts by mass of polymerizable monomer (A). [3] An adhesive composition according to [1] or [2], wherein the monofunctional alkyl (meth)acrylate (A1) having an alicyclic structure has an alicyclic structure with 3 to 12 carbon atoms. [4] An adhesive composition according to any one of [1] to [3], wherein the monofunctional alkyl (meth)acrylate (A1) having an alicyclic structure is one or two selected from isobornyl methacrylate and dicyclopentyl methacrylate. [5] An adhesive composition according to any one of [1] to [4], wherein the content of elastomer (B) is 25% by mass or more and 60% by mass or less based on the total amount of the adhesive composition. [6] An adhesive composition according to any one of [1] to [5], wherein elastomer (B) contains (meth)acrylonitrile-butadiene copolymer polymer (B1). [7] An adhesive composition according to any one of [1] to [6], which is a room-temperature curing type. [8] An adhesive composition according to any one of [1] to [7], wherein it is a two-component mixed adhesive composition. [9] An adhesive composition according to [8], wherein the exothermic peak time measured by the following procedure 2 is 15 minutes or more and 30 minutes or less. <Procedure 2> Mix 5 g each of the two components of the adhesive composition in an atmosphere of 25°C to start the reaction and measure the reaction temperature.The time taken from the start of the reaction until the reaction temperature reaches its maximum value is measured and defined as the exothermic peak time (minutes).

[10] An adhesive composition further comprising a polymerization initiator (C) in any one of [1] to [9].

[11] An adhesive composition further comprising a reducing agent (D) in any one of [1] to

[10] .

[12] An adhesive composition used in a motor in any one of [1] to

[13] .

[13] An adhesive composition used in a motor in the adhesive composition described in

[12] for fixing between a zinc-containing metal surface-plated magnet and a rotor, or between a zinc-containing metal surface-plated magnet and a stator.

[14] An article comprising a cured product made from an adhesive composition described in any one of [1] to

[13] .

[15] A motor comprising a cured product made from an adhesive composition described in any one of [1] to

[13] .

[0013] According to the present invention, it is possible to provide an adhesive composition that can improve the balance between initial adhesion and long-term heat resistance, as well as articles and motors using the adhesive composition.

[0014] Embodiments of the present invention will be described in detail below.

[0015] In this specification, the notation "X to Y" in descriptions of numerical ranges means X or greater and Y or less, unless otherwise specified. For example, "1 to 5 mass%" means "1 mass% or greater and 5 mass% or less."

[0016] In this specification, when a group (atomic group) is not specified as substituted or unsubstituted, it includes both unsubstituted and substituted groups. For example, "alkyl group" includes not only unsubstituted alkyl groups but also substituted alkyl groups. In this specification, "(meth)acrylic" represents a concept that includes both acrylic and methacrylic. The same applies to similar notations such as "(meth)acrylate". In this specification, the term "organic group" means an atomic group obtained by removing one or more hydrogen atoms from an organic compound, unless otherwise specified. For example, "monovalent organic group" refers to an atomic group obtained by removing one hydrogen atom from any organic compound.

[0017] In this specification, when a composition is in a two-part form consisting of a first agent and a second agent, the content of each component is preferably expressed as the content relative to the total of the first and second agents.

[0018] The composition of this embodiment is preferably an adhesive composition. The case where an adhesive composition is used will be described below.

[0019] <Adhesive Composition> The adhesive composition of this embodiment comprises a polymerizable monomer (A) and an elastomer (B), and is an adhesive composition used for bonding to zinc-containing metals, wherein the polymerizable monomer (A) contains a monofunctional alkyl (meth)acrylate (A1) having an alicyclic structure, and the tensile shear strength measured in the following procedure 1 is 4.0 MPa or more and 10 MPa or less. <Procedure 1> (1) Prepare an electro-galvanized magnet (25 mm × 50 mm × 3 mm) whose surface has been degreased with acetone, and a carbon steel plate (JIS G3141 (SPCC-SD, 25 mm × 100 mm × 1.5 mm) and bond them together using the adhesive composition under the following conditions i to obtain a laminate. (Condition i) ・Thickness of the cured layer of the adhesive composition: 0.1 mm ・Bonding area: 25 × 12.5 mm ２- Bonding atmosphere: 23±2℃, 50±10%RH - Curing conditions for adhesive composition: 23±2℃, 50±10%RH × 24hrs (2) Next, the obtained laminate is held in a heat shock tester and held at -20℃ for 45 minutes, then the temperature is raised to 130℃, then held at 130℃ for 45 minutes, and then the temperature is lowered again to -20℃. This cycle is repeated 252 times. (3) After that, the tensile shear strength (MPa) of the bonding surface between the electro-galvanized magnet and the carbon steel plate is measured using a tensile tester under the conditions of 130℃, chuck distance of 100 mm, and tensile speed of 10 mm / min.

[0020] This improves the balance between the initial adhesion and long-term heat resistance of the adhesive composition. The details of this reason are not clear, but it is thought to be as follows. For example, adhesives used in motors are exposed to high-temperature environments and subjected to strong tensile forces due to the miniaturization and increased power output of motors. Therefore, by using a monofunctional alkyl (meth)acrylate (A1) having an alicyclic structure, its bulky structure maintains appropriate elasticity even at high temperatures, and its low hygroscopicity suppresses corrosion caused by moisture at the interface with zinc-containing metals, thus providing adhesion to zinc-containing metals. Furthermore, regarding the tensile shear strength measured in step 1, by using an index based on a heat shock test that simulates the harsh operating environment of motors and deliberately controlling it to 10 MPa or less, excessive rigidity is avoided, and stress caused by the difference in thermal expansion between components during heat shock is mitigated, thereby allowing for a higher level of control over the balance between initial adhesion and long-term heat resistance.

[0021] Furthermore, "long-term heat resistance" refers to the intended use in high-temperature environments resulting from the miniaturization and increased output of motors, etc., and specifically, resistance to temperatures of 100°C to 150°C for 500 to 1000 hours.

[0022] (Tensile Shear Strength) The tensile shear strength measured in step 1 is 4.0 MPa or higher, preferably 4.5 MPa or higher, more preferably 4.7 MPa or higher, even more preferably 5.0 MPa or higher, and even more preferably 5.5 MPa or higher. By setting the tensile shear strength to be above the lower limit, a higher level of balance between initial adhesion and long-term heat resistance can be achieved. The tensile shear strength measured in step 1 is 10 MPa or lower, preferably 9 MPa or lower, and even more preferably 8 MPa or lower. By setting the tensile shear strength to be below the upper limit, good initial adhesion and long-term heat resistance can be obtained.

[0023] The tensile shear strength measured in step 1 can be achieved, for example, by adjusting the type and proportion of each component in the adhesive composition of this embodiment, the mixing order and method of each component, the formulation, etc. Specifically, examples include, but are not limited to, using a monofunctional alkyl (meth)acrylate (A1) having an alicyclic structure as the polymerizable monomer (A), adjusting the type and blending balance of the elastomer (B), or using a two-component mixture type.

[0024] (Characteristics) The adhesive composition of this embodiment may be a single-component type or a two-component type (a form in which two components filled in separate containers are mixed immediately before use).

[0025] When the adhesive composition of this embodiment is a two-part type, it is preferable to adjust the amounts of each component in the first and second components so that the adhesive composition after mixing the first and second components contains each component within a range of preferred content. For example, it is preferable that the polymerization initiator (C) and the reducing agent (D), described later, be separate agents. This helps to suppress unintended reactions of the adhesive composition of this embodiment. Furthermore, the various properties of the adhesive composition described herein relate to the adhesive composition after mixing the first and second components.

[0026] If the adhesive composition of this embodiment is a two-component mixture type, it is preferable that the exothermic peak time measured in the following procedure 2 is 15 minutes or more and 30 minutes or less. <Procedure 2> Mix 5 g each of the two components of the adhesive composition in an atmosphere of 25°C to start the reaction and measure the reaction temperature. Measure the time it takes from the start of the reaction until the reaction temperature reaches its highest value, and define this as the exothermic peak time (minutes).

[0027] More specifically, for example, in step 2, a thermocouple is inserted into the mixture of the two components of the adhesive composition immediately after mixing, and the temperature and time are recorded. In this embodiment, the adhesive composition undergoes a curing reaction upon contact between the two components, causing the temperature to rise, and then the temperature decreases after curing is complete. By keeping the exothermic peak time within the above numerical range, good curing characteristics can be obtained without requiring heating.

[0028] In step 2, the temperature at the peak of exothermic reaction is preferably 50°C to 80°C, and more preferably 55°C to 75°C.

[0029] The adhesive composition of this embodiment is room-temperature curing type. That is, it can be cured at an ambient temperature of 10°C to 40°C, preferably 15°C to 30°C.

[0030] Furthermore, the adhesive composition of this embodiment is preferably liquid at room temperature, and if it is a two-part type, it is preferable that both the first and second components are liquid.

[0031] The components included in the adhesive composition of this embodiment will be described below.

[0032] <Polymerizable Monomer (A)> The adhesive composition of this embodiment contains polymerizable monomer (A), which comprises monofunctional alkyl (meth)acrylate (A1) having an alicyclic structure. By using a monofunctional polymerizable monomer, the crosslinking density can be reduced compared to when a polyfunctional polymerizable monomer is used, making it easier to maintain appropriate elasticity. In addition, having an alicyclic structure improves flexibility and heat resistance.

[0033] A monofunctional alkyl (meth)acrylate (A1) having an alicyclic structure is a compound having one (meth)acryloyl group and having an alicyclic structure. The alicyclic structure is an alicyclic hydrocarbon in which at least three or more carbon atoms are linked in a ring, preferably having 3 to 12 carbon atoms, more preferably 4 to 10 carbon atoms, and preferably having a portion of the alicyclic structure substituted with an acrylic group.

[0034] Examples of monofunctional alkyl (meth)acrylates (A1) having an alicyclic structure include isobornyl methacrylate (isobornyl methacrylate) represented by the following formula (1) and dicyclopentyl methacrylate represented by the following formula (2). The alicyclic structure may be monocyclic, polycyclic, or cross-linked. Examples include cyclooalkyl groups (such as cyclohexyl groups), isobornyl groups, dicyclopentanyl groups, dicyclopentenyl groups, dicyclopentanyloxyethyl groups, tricyclodecanyl groups, and adamantyl groups. Among these, isobornyl groups and dicyclopentanyl groups having a polycyclic structure are preferred from the viewpoint of thermal shock resistance and adhesion to zinc-plated surfaces.

[0035]

[0036]

[0037] The content of the monofunctional alkyl (meth)acrylate having an alicyclic structure (A1) is preferably 70 parts by mass or more, more preferably 75 parts by mass or more, still more preferably 80 parts by mass or more, and even more preferably 85 parts by mass or more, relative to 100 parts by mass of the polymerizable monomer (A). By setting the content of the monofunctional alkyl (meth)acrylate (A1) to be equal to or more than the above lower limit, the balance between initial adhesiveness and long-term heat resistance can be improved. On the other hand, the content of the monofunctional alkyl (meth)acrylate having an alicyclic structure (A1) is preferably 99 parts by mass or less, more preferably 97 parts by mass or less, and still more preferably 95 parts by mass or less, relative to 100 parts by mass of the polymerizable monomer (A). By setting the content of the monofunctional alkyl (meth)acrylate (A1) to be equal to or less than the above upper limit, good initial adhesiveness and long-term heat resistance can be maintained.

[0038] In addition, the content of the monofunctional alkyl (meth)acrylate having an alicyclic structure (A1) in the adhesive composition of the present embodiment is preferably 40% by mass or more, more preferably 45% by mass or more, relative to the total mass of the adhesive composition. On the other hand, the content of the monofunctional alkyl (meth)acrylate having an alicyclic structure (A1) in the adhesive composition of the present embodiment is preferably 70% by mass or less, more preferably 60% by mass or less, relative to the total mass of the adhesive composition.

[0039] In addition, the polymerizable monomer (A) may comprise a polymerizable monomer (A) other than the monofunctional alkyl (meth)acrylate having an alicyclic structure (A1). Specific examples thereof include a highly polar monomer (A2) having a polar functional group and a carbon-carbon double bond, and phenoxyethyl (meth)acrylate.

[0040] The highly polar monomer (A2) may be a monofunctional monomer (a monomer having one carbon-carbon double bond) or a polyfunctional monomer (a monomer having a plurality of carbon-carbon double bonds), and is preferably a monofunctional monomer.

[0041] The polar functional groups of the highly polar monomer (A2) include carboxyl groups and hydroxyl groups, from the viewpoint of further improving interaction with components used in automobile manufacturing. Among these, hydroxyl groups are preferred from the viewpoint of maintaining chemical stability at high temperatures at the adhesive interface with zinc-containing metals and suppressing the decrease in adhesive strength after heat shock. On the other hand, although carboxyl groups have the effect of improving initial adhesion, they are reactive with the zinc layer, so it is preferable that they be substantially absent.

[0042] Specific examples of highly polar monomers (A2) include carboxyl group-containing monomers such as (meth)acrylic acid, fumaric acid, maleic acid, fumaric anhydride, and maleic anhydride; and hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate and 2-hydroxypropyl (meth)acrylate.

[0043] In particular, from the viewpoint of stability at the adhesive interface to zinc-containing metals, it is more preferable to include hydroxyalkyl (meth)acrylate, and even more preferably to include 2-hydroxypropyl methacrylate. That is, by selecting a hydroxyl group-containing (meth)acrylate as the highly polar monomer (A2) and substantially omitting carboxyl group-containing (meth)acrylate, it is possible to maintain high tensile shear strength even after harsh heat shock tests through a synergistic effect with the alicyclic structure (meth)acrylate (A1) without excessively degrading the zinc interface.

[0044] In the adhesive composition of the present embodiment, the content of the high-polarity monomer (A2) is preferably 2% by mass or more, more preferably 3% by mass or more, relative to the total mass of the adhesive composition. On the other hand, in the adhesive composition of the present embodiment, the content of the high-polarity monomer (A2) is preferably 20% by mass or less, more preferably 15% by mass or less, relative to the total mass of the adhesive composition. In addition, when the adhesive composition contains a hydroxyl group-containing (meth)acrylate, the content of the hydroxyl group-containing (meth)acrylate is preferably 1.0% by mass or more, more preferably 2.5% by mass or more, relative to the total mass of the adhesive composition. On the other hand, the content of the hydroxyl group-containing (meth)acrylate is preferably 12% by mass or less, more preferably 10% by mass or less, relative to the total mass of the adhesive composition.

[0045] In the adhesive composition of the present embodiment, the content of the polymerizable monomer (A) is preferably 40% by mass or more, more preferably 50% by mass or more, relative to the total mass of the adhesive composition. On the other hand, in the adhesive composition of the present embodiment, the content of the polymerizable monomer (A) is preferably 85% by mass or less, more preferably 80% by mass or less, and even more preferably 75% by mass or less, relative to the total mass of the adhesive composition.

[0046] The adhesive composition of the present embodiment may contain a phosphate group-containing monomer (A3) as an additional polymerizable monomer (A). The phosphate group-containing monomer (A3) includes monomers having a phosphate group and a (meth)acryloyl group, and specific examples thereof include 2-hydroxyethyl (meth)acrylate acid phosphate. The phosphate group-containing monomer (A3) has the effect of improving the initial adhesion to zinc-containing metals.

[0047] Furthermore, when a phosphate group-containing monomer (A3) is included, the content of the phosphate group-containing monomer (A3) is preferably 0.05% by mass or more, more preferably 1.0% by mass or more, based on the total amount of the adhesive composition. On the other hand, the content of the phosphate group-containing monomer (A3) is preferably 5.0% by mass or less, more preferably 3.0% by mass or less, based on the total amount of the adhesive composition. In this embodiment, by using a phosphate group-containing monomer (A3) in combination within the above range in a system mainly composed of a specific alicyclic structure (A1), it is possible to obtain the adhesion improvement effect of the phosphate group while suppressing the deterioration of the zinc interface even in harsh environments after heat shock and maintaining high adhesive strength.

[0048] <Elastomer (B)> The adhesive composition of this embodiment includes elastomer (B). Elastomer (B) preferably has soft segment units. The soft segment units preferably include one or more selected from the group consisting of diene structures, ethylene structures, propylene structures, isoprene structures, urethane structures, ethylene glycol structures, propylene glycol structures, silicone structures, and chloroprene structures, and more preferably include diene structures such as butadiene structures. The diene structures preferably include butadiene structures. In addition to soft segment units, elastomer (B) may also have hard segments. "Soft segments" represent flexible portions that exhibit rubber elasticity. "Hard segments" represent molecularly constrained portions that act as crosslinking points for crosslinked rubber to prevent plastic deformation.

[0049] The content of soft segment units in elastomer (B) is preferably 15% by mass or more and 90% by mass or less, and more preferably 25% by mass or more and 85% by mass or less, of the total elastomer (B).

[0050] The elastomer (B) containing a butadiene structure preferably contains a (meth)acrylonitrile-butadiene copolymer polymer (B1). Examples of the (meth)acrylonitrile-butadiene copolymer polymer (B1) include one or more selected from the group consisting of (meth)acrylonitrile-butadiene rubber, methyl (meth)acrylate-butadiene-styrene rubber, and methyl (meth)acrylate-butadiene-(meth)acrylonitrile-styrene rubber. In particular, the elastomer (B) preferably contains one or more selected from the group consisting of (meth)acrylonitrile-butadiene rubber and methyl (meth)acrylate-butadiene-(meth)acrylonitrile-styrene rubber. The (meth)acrylonitrile-butadiene rubber may or may not have (meth)acryloyl groups at its ends.

[0051] The content of (meth)acrylonitrile-butadiene copolymer polymer (B1) in the adhesive composition of this embodiment is preferably 80 parts by mass or more, more preferably 88 parts by mass or more, and even more preferably 90 parts by mass or more, when the total content of elastomer (B) is 100 parts by mass. By setting the content of elastomer (B) to above the lower limit, the balance between initial adhesion and long-term heat resistance can be improved. On the other hand, the content of (meth)acrylonitrile-butadiene copolymer polymer (B1) in the adhesive composition of this embodiment may be 100 parts by mass when the total content of elastomer (B) is 100 parts by mass. This provides good initial adhesion and long-term heat resistance.

[0052] The elastomer (B) content in the adhesive composition of this embodiment is preferably 25% by mass or more, more preferably 30% by mass or more, based on the total amount of the adhesive composition. On the other hand, the elastomer (B) content in the adhesive composition of this embodiment is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less, based on the total amount of the adhesive composition.

[0053] The adhesive composition of this embodiment preferably further contains the following components.

[0054] <Polymerization Initiator (C)> The adhesive composition of this embodiment preferably contains a polymerization initiator (C). The polymerization initiator (C) polymerizes the carbon-carbon double bond of the polymerizable monomer (A), thereby improving adhesion.

[0055] The polymerization initiator (C) preferably includes a thermal radical polymerization initiator. From the viewpoint of further improving reactivity, the thermal radical polymerization initiator preferably includes an organic peroxide, more preferably one or more selected from the group consisting of cumene hydroperoxide, paramentane hydroperoxide, tert-butyl hydroperoxide, diisopropylbenzene dihydroperoxide, methyl ethyl ketone peroxide, and tert-butyl peroxybenzoate, and even more preferably includes cumene hydroperoxide.

[0056] The content of the polymerization initiator (C) in the adhesive composition of this embodiment is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, even more preferably 1.0 part by mass or more, even more preferably 1.5 parts by mass or more, and preferably 20.0 parts by mass or less, more preferably 15.0 parts by mass or less, even more preferably 12.0 parts by mass or less, even more preferably 10.0 parts by mass or less, even more preferably 8.0 parts by mass or less, even more preferably 6.0 parts by mass or less, even more preferably 4.0 parts by mass or less, and even more preferably 3.0 parts by mass or less, when the total content of polymerizable monomer (A) and elastomer (B) is 100 parts by mass.

[0057] The content of polymerization initiator (C) in the adhesive composition of this embodiment is preferably 1.0% by mass or more, more preferably 2.0% by mass or more, and even more preferably 2.5% by mass or more, based on the total amount of the adhesive composition. On the other hand, the content of polymerization initiator (C) in the adhesive composition of this embodiment is preferably 6.0% by mass or less, more preferably 5.0% by mass or less, and even more preferably 4.0% by mass or less, based on the total amount of the adhesive composition.

[0058] <Reducing Agent (D)> The adhesive composition of this embodiment preferably contains a reducing agent (D). The adhesive composition of this embodiment can be further improved in curability by using a polymerization initiator (C) and a reducing agent (D) in combination. The reducing agent (D) may be any reducing agent that reacts with the polymerization initiator (C) to generate radicals. The reducing agent (D) preferably contains one or more selected from the group consisting of tertiary amines, thiourea derivatives, and transition metal salts, and more preferably contains a transition metal salt.

[0059] Examples of tertiary amines include one or more selected from the group consisting of triethylamine, tripropylamine, tributylamine, and N,N-dimethylparatoluidine. Examples of thiourea derivatives include one or more selected from the group consisting of 2-mercaptobenzimidazole, methylthiourea, dibutylthiourea, ethylenethiourea, acetyl-2-thiourea, benzoylthiourea, N,N-diphenylthiourea, N,N-diethylthiourea, N,N-dibutylthiourea, and tetramethylthiourea. Examples of transition metal salts include one or more selected from the group consisting of cobalt naphthenate, copper naphthenate, and vanadylacetylacetonate. The transition metal salt more preferably includes vanadylacetylacetonate.

[0060] The content of the reducing agent (D) in the adhesive composition of this embodiment is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, even more preferably 0.10 parts by mass or more, even more preferably 0.15 parts by mass or more, even more preferably 0.20 parts by mass or more, and preferably 10.0 parts by mass or less, more preferably 5.0 parts by mass or less, even more preferably 3.0 parts by mass or less, even more preferably 2.0 parts by mass or less, even more preferably 1.0 part by mass or less, and even more preferably 0.50 parts by mass or less, when the total content of polymerizable monomer (A) and elastomer (B) is 100 parts by mass.

[0061] The content of the reducing agent (D) in the adhesive composition of this embodiment is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and even more preferably 0.2% by mass or more, based on the total amount of the adhesive composition. On the other hand, the content of the reducing agent (D) in the adhesive composition of this embodiment is preferably 3.0% by mass or less, more preferably 2.0% by mass or less, and even more preferably 1.0% by mass or less, based on the total amount of the adhesive composition.

[0062] <Other Components> The adhesive composition of this embodiment may or may not contain other components other than those listed above.

[0063] (Paraffin) The adhesive composition of this embodiment may contain paraffin. As paraffin, for example, various types of paraffin can be used to expedite the hardening of the part in contact with air. Examples of paraffin include one or more selected from the group consisting of paraffin wax, microcrystalline wax, carnauba wax, beeswax, lanolin, whale wax, ceresin, and candelilla wax.

[0064] If the adhesive composition of this embodiment contains paraffin, it may contain only paraffin 1 or paraffin 2 or more. If the adhesive composition of this embodiment contains paraffin, the paraffin content in the adhesive composition of this embodiment is preferably 0.01 parts by mass or more and 3 parts by mass or less, and more preferably 0.1 parts by mass or more and 2 parts by mass or less, when the total content of polymerizable monomer (A) and elastomer (B) is 100 parts by mass.

[0065] (Stabilizers) The adhesive composition of this embodiment may contain various stabilizers from the viewpoint of further improving storage stability. Examples of stabilizers include phenolic antioxidants (e.g., 2,2'-methylenebis(4-methyl-6-t-butylphenol)), quinone compounds (e.g., p-benzoquinone, hydroquinone monomethyl ether), compounds known as polymerization inhibitors (e.g., amine polymerization inhibitors such as phenothiazine, citric acid, etc.), and stable radical-type compounds having stable radicals.

[0066] If the adhesive composition of this embodiment contains a stabilizer, the amount of stabilizer in the adhesive composition of this embodiment is preferably 0.001 parts by mass or more, more preferably 0.005 parts by mass or more, even more preferably 0.01 parts by mass or more, even more preferably 0.05 parts by mass or more, even more preferably 0.10 parts by mass or more, and even more preferably 5.0 parts by mass or less, more preferably 3.0 parts by mass or less, even more preferably 2.0 parts by mass or less, even more preferably 1.5 parts by mass or less, and even more preferably 1.0 part by mass or less, from the viewpoint of further improving storage stability while suppressing a decrease in the performance of the adhesive composition.

[0067] <Method for Manufacturing Adhesive Composition> In manufacturing the adhesive composition of this embodiment, it is preferable to appropriately adjust the mixing order and method of each component, rather than simply mixing the components as described above. In manufacturing the adhesive composition of this embodiment, it is particularly preferable that the polymerizable monomer (A) and the elastomer (B) are thoroughly mixed. For this reason, as shown in the examples below, it is preferable to first thoroughly and uniformly mix at least a portion of the polymerizable monomer (A) and at least a portion of the elastomer (B) at 50 to 80°C to form a mixture, and then add the other components to the mixture and stir. By doing so, it is believed that the polymerizable monomer (A) and the elastomer (B) will be thoroughly and uniformly mixed. The adhesive composition manufactured in this manner tends to satisfy the above-mentioned characteristics of the adhesive composition (elongation at break, tensile shear adhesive strength, etc.) more easily than adhesive compositions obtained by other manufacturing methods.

[0068] <Zinc-containing metals> The adhesive composition of this embodiment is suitably used for bonding to zinc-containing metals. Zinc-containing metals are alloys containing zinc as the main component, and are intended to be alloys with a zinc content of 50% or more. Examples include alloys of zinc with one or more metals selected from copper, aluminum, antimony, bismuth, gold, iron, lead, mercury, silver, tin, magnesium, cobalt, nickel, tellurium, and sodium.

[0069] <Applications> The adhesive composition of this embodiment can be suitably used as an adhesive for motors, and more specifically, it can be suitably used as an adhesive for fixing the magnets between the rotor or the magnets between the stator in a motor. In particular, it is suitable for magnets that have been surface-plated with zinc-containing metal. Furthermore, the motor can be used as a component of various machinery and equipment, transportation equipment, etc., and is suitable, for example, as a motor for automobile parts.

[0070] <Article> The article of this embodiment includes a cured product made from the adhesive composition of this embodiment. An article containing a cured product of the adhesive composition can be obtained by applying the adhesive composition of this embodiment to an article and curing it. The adhesive composition of this embodiment preferably cures without heating (at room temperature) and can bond articles (especially when it contains a polymerization initiator and a reducing agent). Of course, heating during the bonding of articles is not excluded.

[0071] <Motor> The motor of this embodiment includes a cured product made from the adhesive composition of this embodiment. The motor is not particularly limited, but is preferably one used in an environment exposed to rapid temperature changes, such as an in-vehicle motor for electric power steering, a drive motor, or a generator, or a servo motor for an industrial robot. The motor of this embodiment includes, for example, a magnet, a rotor, and a stator, and includes a cured product made from the adhesive composition of this embodiment between the magnet and the rotor and between the magnet and the stator. In this case, it is preferable that the space between the magnet and the rotor and between the magnet and the stator in the motor is fixed by the cured product made from the adhesive composition of this embodiment. A method for fixing the space between the magnet and the rotor is, for example, to fix the magnet in a slot in the rotor. A method for fixing the space between the magnet and the stator is, for example, to fix the magnet and the yoke. The magnet can be a ferrite magnet, a permanent magnet, etc. A permanent magnet can be a neodymium magnet, etc.

[0072] This specification primarily describes "adhesive compositions." However, the adhesive compositions described herein can also be used in fields other than adhesion, such as coatings and injection materials. In other words, the adhesive compositions described herein can also be used as compositions with no limited applications, curable compositions, or resin compositions. The compositions of this embodiment can be used, for example, as so-called adhesives, sealants, photosensitive resin layers, insulating resin layers, thermally conductive resin layers, coatings, etc.

[0073] The embodiments of the present invention have been described above, but these are illustrative examples of the present invention, and various other configurations can be adopted. Furthermore, the present invention is not limited to the embodiments described above, and modifications, improvements, etc., within the scope that can achieve the objectives of the present invention are included in the present invention. Reference embodiments are listed below. [1] An adhesive composition for use in bonding to zinc-containing metals, comprising a polymerizable monomer (A) and an elastomer (B), wherein the polymerizable monomer (A) comprises a monofunctional alkyl (meth)acrylate (A1) having an alicyclic structure, and the tensile shear strength measured in the following procedure 1 is 4.0 MPa or more and 10 MPa or less. <Procedure 1> (1) Prepare an electro-galvanized magnet (25 mm x 50 mm x 3 mm) whose surface has been degreased with acetone, and a carbon steel plate (JIS G3141 (SPCC-SD, 25 mm x 100 mm x 1.5 mm) and bond them together using the adhesive composition under the following conditions i to obtain a laminate. (Condition i) - Cured layer thickness of adhesive composition: 0.1 mm - Bonding area: 25 x 12.5 mm ２- Bonding atmosphere: 23±2℃, 50±10%RH - Curing conditions for adhesive composition: 23±2℃, 50±10%RH × 24hrs (2) Next, the obtained laminate is held in a heat shock tester, held at -20℃ for 45 minutes, then heated to 130℃, held at 130℃ for 45 minutes, and then cooled again to -20℃. This cycle is repeated 252 times. (3) After that, using a tensile tester, the tensile shear strength (MPa) of the bonding surface between the electro-galvanized magnet and the carbon steel sheet is measured under the conditions of 130℃, chuck distance of 100 mm, and tensile speed of 10 mm / min. [2] The adhesive composition according to [1], wherein the content of monofunctional alkyl (meth)acrylate (A1) having an alicyclic structure is 70 parts by mass or more and 99 parts by mass or less per 100 parts by mass of polymerizable monomer (A). [3] An adhesive composition according to [1] or [2], wherein the monofunctional alkyl (meth)acrylate (A1) having an alicyclic structure has an alicyclic structure with 3 to 12 carbon atoms. [4] An adhesive composition according to any one of [1] to [3], wherein the monofunctional alkyl (meth)acrylate (A1) having an alicyclic structure is one or two selected from isobornyl methacrylate and dicyclopentyl methacrylate. [5] An adhesive composition according to any one of [1] to [4], wherein the content of elastomer (B) is 25% by mass or more and 60% by mass or less based on the total amount of the adhesive composition. [6] An adhesive composition according to any one of [1] to [5], wherein elastomer (B) contains (meth)acrylonitrile-butadiene copolymer polymer (B1). [7] An adhesive composition according to any one of [1] to [6], which is a room-temperature curing type. [8] An adhesive composition according to any one of [1] to [7], wherein it is a two-component mixed adhesive composition. [9] An adhesive composition according to [8], wherein the exothermic peak time measured by the following procedure 2 is 15 minutes or more and 30 minutes or less. <Procedure 2> Mix 5 g each of the two components of the adhesive composition in an atmosphere of 25°C to start the reaction and measure the reaction temperature.The time taken from the start of the reaction until the reaction temperature reaches its maximum value is measured and this is defined as the exothermic peak time (minutes).

[10] An adhesive composition according to any one of [1] to [9], wherein the zinc-containing metal is a magnet surface-plated with the zinc-containing metal.

[11] An adhesive composition according to any one of [1] to

[10] , further comprising a polymerization initiator (C).

[12] An adhesive composition according to any one of [1] to

[11] , further comprising a reducing agent (D).

[13] An adhesive composition according to any one of [1] to

[12] , used in a motor.

[14] An adhesive composition according to

[13] , used to fix the space between the zinc-containing metal-plated magnet and the rotor, or between the zinc-containing metal-plated magnet and the stator of the motor.

[15] An article comprising a cured product made from the adhesive composition according to any one of [1] to

[13] .

[16] A motor comprising a cured product made from an adhesive composition according to any one of [1] to

[13] .

[17] A composition comprising a polymerizable monomer (A) and an elastomer (B), wherein the polymerizable monomer (A) comprises a monofunctional alkyl (meth)acrylate (A1) having an alicyclic structure, and the tensile shear strength measured in the following procedure 1 is 4.0 MPa or more and 10 MPa or less. <Procedure 1> (1) Prepare an electro-galvanized magnet (25 mm × 50 mm × 3 mm) whose surface has been degreased with acetone, and a carbon steel plate (JIS G3141 (SPCC-SD, 25 mm × 100 mm × 1.5 mm) and bond them together using the composition under the following conditions i to obtain a laminate. (Condition i) - Thickness of the cured layer of the composition: 0.1 mm - Bonding area: 25 × 12.5 mm. ２- Bonding atmosphere: 23±2℃, 50±10%RH - Curing conditions of composition: 23±2℃, 50±10%RH × 24hrs (2) Next, the obtained laminate is held in a heat shock tester and held at -20℃ for 45 minutes, then the temperature is raised to 130℃, then held at 130℃ for 45 minutes, and then the temperature is lowered again to -20℃. This cycle is repeated 252 times. (3) After that, the tensile shear strength (MPa) of the bonding surface between the electro-galvanized magnet and the carbon steel sheet is measured using a tensile tester under the conditions of 130℃, chuck distance of 100 mm, and tensile speed of 10 mm / min.

[0074] The present invention will be described more specifically below with reference to examples, but the present invention is not limited to these examples.

[0075] [1. Preparation of Adhesive Compositions] The adhesive compositions of the examples and comparative examples shown in Tables 1 and 2 were prepared by the following procedure. A stirring device equipped with stirring blades was used for mixing. First, the following raw materials were prepared, and polymerizable monomer (A), elastomer (B) (excluding "elastomer 3" described later), citric acid, and paraffin were mixed at 60-70°C in the first and second components respectively to dissolve elastomer (B) and obtain each mixture. The following day, elastomer 3, polymerization initiator (C), reducing agent (D), and the remaining additives were added to each obtained mixture and stirred, then degassed and filtered to prepare the first and second components, respectively. Both the first and second components were liquid. Subsequently, the first and second components were mixed in equal amounts to prepare each adhesive composition. Note that the "%" for each component in Tables 1 and 2 indicates "mass %".

[0076] (Raw Materials) <Polymerizable Monomer (A)> (High Polarity Monomer (A2)) ・Polymerizable Monomer 1: 2-Hydroxypropyl Methacrylate, "HPMA" manufactured by Kyoeisha (Aromatic ring-containing monofunctional monomer) ・Polymerizable Monomer 2: Phenoxyethyl Methacrylate, "PO" manufactured by Kyoeisha (Aromatic ring-containing polyfunctional monomer) ・Polymerizable Monomer 3: 2,2-Bis[4-(Methacroxypolymethylene)]phenyl]propane (EO 10 mol), "BPE-500" manufactured by Shin Nakamura Chemical Industry Co., Ltd. (Aliphatic monofunctional monomer) ・Polymerizable Monomer 4: 2-Ethylhexyl Methacrylate), "EHMA" manufactured by Kyoeisha (Monofunctional alkyl (meth)acrylate (A1) with an alicyclic structure) ・Polymerizable Monomer 5: Isobornyl Methacrylate, "IBX" manufactured by Kyoeisha ・Polymerizable Monomer 6: Dicyclopentyl Methacrylate, "FA-513M" manufactured by Hitachi Chemical Co., Ltd. (Polyfunctional monomers) • Polymerizable monomer 7: Dicyclopentyl dimethyl dimethacrylate, "NK Ester DCP", manufactured by Shin Nakamura Chemical Industry Co., Ltd. • Polymerizable monomer 8: Trimethylolpropane trimethacrylate, "NK Ester TMPT-M", manufactured by Shin Nakamura Chemical Industry Co., Ltd. (High polarity monomer (A2)) • Polymerizable monomer 9: Methacrylic acid, "AM", manufactured by Mitsubishi Gas Chemical Company

[0077] <Elastomer (B)> ・Elastomer 1: MBS resin, "KANE ACE B-513" manufactured by Kaneka Corporation ・Elastomer 2: Acrylonitrile butadiene rubber (acrylonitrile content 19.5% by mass, soft segment unit content 81% by mass) "N250SL" manufactured by JSR Corporation ・Elastomer 3: Liquid acrylonitrile butadiene rubber with methacryloyl groups at both ends (acrylonitrile content 18% by mass, soft segment unit content 82% by mass) "1300X33VTBNX LC" manufactured by CVC Corporation

[0078] <Polymerization Initiator (C)> Polymerization Initiator 1: Cumene Hydroperoxide, "K-90", manufactured by Nouryon Co., Ltd. <Reducing Agent (D)> Reducer 1: Vanadyl Acetyl Acetonate, "VO (AA)", manufactured by Shinko Chemical Industry Co., Ltd. <Others> Additive 1: Stabilizer, Citric Acid Additive 2: Paraffin Additive 3: Stabilizer, Parabenzoquinone Additive 4: Stabilizer, 2,2'-Methylenebis(6-tert-butyl-p-cresol) Additive 5: Stabilizer, Methoquinone Additive 6: Stabilizer, Phenothiazine Additive 7: Stabilizer, 2,4,6-Tris(2',5'-di-tert-butyl-4'-hydroxybenzyl)mesitylene (Phosphoric Acid-Containing Monomer (A3)) Additive 8: 2-Hydroxyethyl Methacrylate Acid Phosphate

[0079] [2. Measurement] The following measurements were performed using the obtained adhesive compositions. The results are shown in Tables 1 and 2.

[0080] ・Tensile shear strength <Procedure 1> (1) Prepare an electro-galvanized magnet (25 mm x 50 mm x 3 mm) whose surface has been degreased with acetone, and a carbon steel plate (JIS G3141 (SPCC-SD, 25 mm x 100 mm x 1.5 mm)). Using each adhesive composition, these were bonded together under the following conditions i to obtain a laminate. (Condition i) ・Thickness of the cured layer of the adhesive composition: 0.1 mm ・Bonding area: 25 x 12.5 mm ２ - Bonding atmosphere: 23±2℃, 50±10%RH - Curing conditions for adhesive composition: 23±2℃, 50±10%RH × 24hrs (2) Next, the obtained laminate was held in a heat shock tester and held at -20℃ for 45 minutes, then the temperature was raised to 130℃, then held at 130℃ for 45 minutes, and then the temperature was lowered again to -20℃. This cycle was repeated 252 times. (3) After that, the tensile shear strength (MPa) of the adhesive surface between the electro-galvanized magnet and the carbon steel sheet was measured using a tensile tester under the conditions of 130℃, a chuck distance of 100 mm, and a tensile speed of 10 mm / min. <Tensile Testing Machine> - Machine name: "AG-IC" manufactured by Shimadzu Corporation - Oven: "SEG-021H" manufactured by ESPEC Corporation <Heat Shock Conditions> - Machine name: "TSE-12-A" manufactured by ESPEC Corporation - Heating rate: 100°C / min - Cooling rate: 60°C / min

[0081] ・Exothermic peak time (minutes) <Procedure 2> In an atmosphere of 25°C, 5g each of the two components of the adhesive composition were mixed to start the reaction, and the reaction temperature was measured. The time taken from the start of the reaction until the reaction temperature reached its highest value was measured, and this was defined as the exothermic peak time (minutes). At the same time, the exothermic peak temperature (°C) was also confirmed. That is, in an atmosphere of 25°C, 5g each of the two components of the adhesive composition were prepared, and the following thermocouple was inserted into the mixed solution immediately after mixing, and the temperature and time were recorded. <Thermocouple> ・Manufacturer: Sato Keiryoki Co., Ltd., Product name: DK-K-BL-5m, Material: Polyethylene

[0082] [3. Evaluation] Initial adhesion and long-term heat resistance Initial adhesion and long-term heat resistance were evaluated according to the following procedure A. In both cases, a higher tensile shear strength (MPa) value indicates better performance. The results are shown in Tables 1 and 2. <Procedure A> (1) An electro-galvanized magnet (25 mm × 50 mm × 3 mm) with its surface degreased with acetone and a carbon steel plate (JIS G3141 (SPCC-SD, 25 mm × 100 mm × 1.5 mm) were prepared, and these were bonded together using the adhesive composition under the following conditions a to obtain a laminate. Condition a: Cured layer thickness of adhesive composition: 0.1 mm Bonding area: 25 × 12.5 mm ２ - Bonding atmosphere: 23±2℃, 50±10%RH - Curing conditions for adhesive composition: 23±2℃, 50±10%RH × 24hrs (2) The obtained laminate was tested using a tensile testing machine at 130℃, with a chuck distance of 100 mm and a tensile speed of 10 mm / min to measure the tensile shear strength (MPa) of the bonding surface between the electro-galvanized magnet and the carbon steel plate to evaluate the "initial adhesion". (3) Next, the obtained laminate was placed in an oven and held at 130℃ for 1000 hours. After that, the tensile shear strength (MPa) was measured in the same manner as in (2) above to evaluate the "long-term heat resistance".

[0083]

[0084]

[0085] This application claims priority based on Chinese application 202510381470.5 filed on 28 March 2025, and incorporates all of its disclosures herein.

Claims

1. An adhesive composition comprising a polymerizable monomer (A) and an elastomer (B), used for bonding to zinc-containing metals, wherein the polymerizable monomer (A) comprises a monofunctional alkyl (meth)acrylate (A1) having an alicyclic structure, and the tensile shear strength measured in the following procedure 1 is 4.0 MPa or more and 10 MPa or less. <Procedure 1> (1) Prepare an electro-galvanized magnet (25 mm x 50 mm x 3 mm) whose surface has been degreased with acetone, and a carbon steel plate (JIS G3141 (SPCC-SD, 25 mm x 100 mm x 1.5 mm) and bond them together using the adhesive composition under the following conditions i to obtain a laminate. (Condition i) - Thickness of the cured layer of the adhesive composition: 0.1 mm - Bonding area: 25 x 12.5 mm ２ - Bonding atmosphere: 23±2℃, 50±10%RH - Curing conditions for adhesive composition: 23±2℃, 50±10%RH × 24hrs (2) Next, the obtained laminate is held in a heat shock tester and held at -20℃ for 45 minutes, then the temperature is raised to 130℃, then held at 130℃ for 45 minutes, and then the temperature is lowered again to -20℃. This cycle is repeated 252 times. (3) After that, the tensile shear strength (MPa) of the bonding surface between the electro-galvanized magnet and the carbon steel plate is measured using a tensile tester under the conditions of 130℃, chuck distance of 100 mm, and tensile speed of 10 mm / min.

2. The adhesive composition according to claim 1, wherein the content of monofunctional alkyl (meth)acrylate (A1) having an alicyclic structure is 70 parts by mass or more and 99 parts by mass or less, based on the content of polymerizable monomer (A) per 100 parts by mass.

3. The adhesive composition according to claim 1 or 2, wherein the monofunctional alkyl (meth)acrylate (A1) having an alicyclic structure has an alicyclic structure with 3 to 12 carbon atoms.

4. An adhesive composition according to claim 1 or 2, wherein the monofunctional alkyl (meth)acrylate (A1) having an alicyclic structure is one or two selected from isobornyl methacrylate and dicyclopentyl methacrylate.

5. An adhesive composition according to claim 1 or 2, wherein the content of elastomer (B) is 25% by mass or more and 60% by mass or less based on the total amount of the adhesive composition.

6. An adhesive composition according to claim 1 or 2, wherein the elastomer (B) comprises a (meth)acrylonitrile-butadiene copolymer polymer (B1).

7. The adhesive composition according to claim 1 or 2, wherein the adhesive composition is a room-temperature curing type.

8. The adhesive composition according to claim 1 or 2, wherein the adhesive composition is a two-component mixed type.

9. The adhesive composition according to claim 8, wherein the exothermic peak time measured by the following procedure 2 is 15 minutes or more and 30 minutes or less. <Procedure 2> Mix 5 g each of the two components of the adhesive composition in an atmosphere of 25°C to start the reaction and measure the reaction temperature. Measure the time taken from the start of the reaction until the reaction temperature reaches its highest value, and define this as the exothermic peak time (minutes).

10. An adhesive composition according to claim 1 or 2, further comprising a polymerization initiator (C).

11. An adhesive composition according to claim 1 or 2, further comprising a reducing agent (D).

12. The adhesive composition according to claim 1 or 2, wherein the adhesive composition is used in a motor.

13. The adhesive composition according to claim 12, which is used to fix the motor between a magnet surface plated with a zinc-containing metal and a rotor, or between a magnet surface plated with a zinc-containing metal and a stator.

14. An article comprising a cured product made from the adhesive composition according to claim 1 or 2.

15. A motor comprising a cured product made from the adhesive composition according to claim 1 or 2.

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