Coating composition for electromagnetic steel sheet, electromagnetic steel sheet, laminated core, and rotary electric machine

Abstract

An electromagnetic steel sheet for a laminated core is an electromagnetic steel sheet having an insulating coating film (3) on a surface of a base steel sheet (2), the insulating coating film (3) being formed by applying an electromagnetic steel sheet coating composition that is compounded with an epoxy resin, a first curing agent composed of a phenol-aldehyde resin including a phenol skeleton having either or both of an alkyl group and an alkoxy group, and a second curing agent selected from one or more of a phenol-aldehyde resol resin and a phenol novolak resin, in specific proportions.

Description

TECHNICAL FIELD

[0001] The present application relates to a coating composition for an electromagnetic steel sheet, an electromagnetic steel sheet, a laminated core, and a rotating electric machine. This application claims priority based on Japanese Patent Application No. 2020-104248 filed on June 17, 2020, and the contents thereof are incorporated herein. BACKGROUND

[0002] As a core used for a rotating electric machine, a laminated core in which a plurality of electromagnetic steel sheets are joined to and laminated with each other is known. As a joining method of the electromagnetic steel sheets to each other, riveting or welding is known. However, in the riveting or welding, the magnetic characteristics (core loss) of the electromagnetic steel sheets are easily deteriorated due to mechanical strain or thermal strain at the time of processing.

[0003] As a joining method other than the riveting or welding, for example, a method of bonding the electromagnetic steel sheets to each other is known, the electromagnetic steel sheets being formed with an insulating film having a bonding ability on a surface (Patent Literature 1). Since the bonding using the insulating film does not impart mechanical strain or thermal strain, the core loss is more excellent than that of the riveting or welding. The volume change of the epoxy resin is less, and the heat resistance and the oil resistance, chemical resistance are excellent, and as an adhesive for bonding the electromagnetic steel sheets to each other, the epoxy resin is more excellent (Patent Literatures 2 and 3).

[0004] PRIOR ART DOCUMENTS

[0005] PATENT LITERATURES

[0006] Patent Literature 1: Japanese Patent Application Laid-Open No. 2017-011863

[0007] Patent Literature 2: Japanese Patent Application Laid-Open No. 2000-173816

[0008] Patent Literature 3: International Publication No. 2004 / 070080 SUMMARY

[0009] PROBLEMS TO BE SOLVED BY THE INVENTION

[0010] In recent years, further improvement of the efficiency of the electric machine is required, and further reduction of the core loss is required. For the reduction of the core loss, thinning of the electromagnetic steel sheet is powerful. However, with the decrease in the thickness of the sheet, the Young's modulus of the steel sheet decreases, and thus stress strain as a cause of deterioration of the core loss is required not to be imparted to the steel sheet. Although the epoxy resin is excellent in heat resistance, it is hard and low in toughness, and thus stress strain is imparted to the steel sheet due to curing at the time of bonding, and thus when the steel sheet is thinned, it becomes a cause of deterioration of the core loss.

[0011] Further, in a drive motor of an electric automobile or the like, a high temperature is generated at the time of driving, and thus further heat resistance is required.

[0012] As a method of improving heat resistance, there is a method of adding a phenol aldehyde resin. However, a resin excellent in heat resistance is hard at normal temperature, and can impart a large stress to a laminated core, thus deteriorating magnetic characteristics. On the other hand, a resin having a proper hardness around normal temperature becomes soft at high temperature, and thus is poor in heat resistance. For these reasons, it is difficult to achieve both excellent magnetic characteristics and excellent heat resistance, which means that a sufficient adhesive strength can be maintained even in a state exposed to high temperature at the time of driving.

[0013] An object of the present application is to provide a coating composition for an electromagnetic steel sheet capable of achieving both magnetic characteristics of a laminated core and heat resistance in which an adhesive strength of electromagnetic steel sheets to each other can be maintained even in a high temperature state at the time of driving, an electromagnetic steel sheet using the same, a laminated core, and a rotary electric machine.

[0014] Technical means for solving the technical problem

[0015] The present application has the following solutions.

[0016] [1] The coating composition for an electromagnetic steel sheet according to one aspect of the present application contains: an epoxy resin; a first curing agent composed of a phenol aldehyde resin containing a phenol skeleton having either one or both of an alkyl group and an alkoxy group having 2 or more carbon atoms; and a second curing agent selected from one or more of a phenol aldehyde resol resin and a phenol novolak resin; and the content of the first curing agent is 5 parts by mass or more and 150 parts by mass or less with respect to 100 parts by mass of the epoxy resin.

[0017] [2] In the coating composition for an electromagnetic steel sheet according to the above [1], the first curing agent can be composed of a phenol aldehyde resin containing a phenol skeleton having either one or both of an alkyl group having 2 or more carbon atoms and an alkoxy group having 2 or more carbon atoms.

[0018] [3] In the coating composition for an electromagnetic steel sheet according to the above [1] or [2], the total content of the first curing agent and the second curing agent can be 5 parts by mass or more and 155 parts by mass or less with respect to 100 parts by mass of the epoxy resin.

[0019] [4] In the coating composition for an electromagnetic steel sheet according to any one of the above [1] to [3], the curing shrinkage can be 15% or less.

[0020] [5] The electromagnetic steel sheet according to one aspect of the present application has an insulating film on a surface, and the insulating film contains the coating composition for an electromagnetic steel sheet according to any one of the above [1] to [4].

[0021] [6] In a laminated core according to one aspect of the present invention, a plurality of the electromagnetic steel sheets according to the above-mentioned [5] are laminated and bonded to each other.

[0022] [7] A rotary electric machine according to one aspect of the present invention includes the laminated core according to the above-mentioned [6].

[0023] Effects of Invention

[0024] According to the above-mentioned aspect of the present invention, it is possible to provide a coating composition for electromagnetic steel sheets that can balance the magnetic properties of a laminated core and the heat resistance of the bonding strength of electromagnetic steel sheets to each other even in a high-temperature state at the time of driving, an electromagnetic steel sheet using the same, a laminated core, and a rotary electric machine. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is a cross-sectional view of a rotary electric machine provided with the laminated core of the first embodiment of the present invention.

[0026] Figure 2 is a side view of the laminated core shown in Figure 1

[0027] Figure 3 is an A-A cross-sectional view of Figure 2

[0028] Figure 4 is a top view of a raw material for forming the laminated core shown in Figure 1

[0029] Figure 5 is a B-B cross-sectional view of Figure 4

[0030] Figure 6 is an enlarged view of the C portion of Figure 5

[0031] Figure 7 is a side view of a manufacturing apparatus for manufacturing the laminated core shown in Figure 1 DETAILED DESCRIPTION

[0032] Hereinafter, with reference to the drawings, a laminated core according to one embodiment of the present invention, a rotary electric machine provided with the laminated core, and a raw material for forming the laminated core will be described. In the present embodiment, as the rotary electric machine, a motor, specifically, an alternating-current motor, more specifically, a synchronous motor, and still more specifically, a permanent-magnet-excited motor are exemplified. Such a motor is preferably used in an electric vehicle or the like, for example.

[0033] ​​​​​​Furthermore, for numerical ranges enclosed in “~”, both the lower and upper limits are included within that range. Values ​​expressed as “less than” or “more than” are not included in the numerical range.

[0034] (Rotary motor 10)

[0035] like Figure 1 As shown, the rotary motor 10 includes a stator 20, a rotor 30, a housing 50, and a rotating shaft 60. The stator 20 and the rotor 30 are housed within the housing 50.

[0036] The stator 20 is fixed inside the housing 50.

[0037] In this embodiment, the rotary motor 10 is an inner rotor type with the rotor 30 located radially inside the stator 20. However, the rotary motor 10 can also be an outer rotor type with the rotor 30 located outside the stator 20. Furthermore, in this embodiment, the rotary motor 10 is a 12-pole, 18-slot three-phase AC motor. However, the number of poles, slots, and phases can be appropriately changed.

[0038] The rotary motor 10, for example, can rotate at a speed of 1000 rpm by applying an excitation current of 10 A effective value and 100 Hz to each phase.

[0039] The stator 20 includes a stator adhesive laminated iron core (hereinafter referred to as stator core) 21 and windings not shown.

[0040] The stator core 21 includes an annular core back 22 and a plurality of teeth 23. Hereinafter, the direction of the central axis O of the stator core 21 (or core back 22) is referred to as the axial direction, the radial direction (the direction orthogonal to the central axis O) of the stator core 21 (or core back 22) is referred to as the radial direction, and the circumferential direction (the direction around the central axis O) of the stator core 21 (or core back 22) is referred to as the circumferential direction.

[0041] When viewed from above along the axial direction, the back of the core 22 is formed into a ring shape.

[0042] Multiple teeth 23 protrude radially inward from the inner circumference of the back of the core 22 (along the radial direction towards the central axis O of the back of the core 22). The teeth 23 are arranged at equal angular intervals circumferentially. In this embodiment, 18 teeth 23 are provided at a central angle of 20 degrees centered on the central axis O. The teeth 23 are formed to be identical in shape and size. Therefore, the teeth 23 have the same thickness dimension.

[0043] The winding is wound around the tooth portion 23. The winding can be either concentrated or distributed.

[0044] The rotor 30 is arranged radially inside the stator 20 (stator core 21). The rotor 30 includes a rotor core 31 and a plurality of permanent magnets 32.

[0045] The rotor core 31 is formed into an annular shape, coaxially arranged with the stator 20. The rotating shaft 60 is disposed within the rotor core 31. The rotating shaft 60 is fixed to the rotor core 31.

[0046] Multiple permanent magnets 32 are fixed to the rotor core 31. In this embodiment, two permanent magnets 32 form one magnetic pole. Multiple sets of permanent magnets 32 are arranged at equal angular intervals along the circumference. In this embodiment, 12 sets (24 in total) of permanent magnets 32 are arranged at a central angle of 30 degrees centered on the central axis O.

[0047] In this embodiment, an embedded magnet type motor is used as the permanent magnet excitation type motor.

[0048] Multiple through holes 33 are formed in the rotor core 31, extending axially through the rotor core 31. The multiple through holes 33 are arranged corresponding to the configuration of multiple permanent magnets 32. Each permanent magnet 32 ​​is fixed to the rotor core 31 in a state where it is disposed within its corresponding through hole 33. The fixing of each permanent magnet 32 ​​to the rotor core 31 can be achieved, for example, by bonding the outer surface of the permanent magnet 32 ​​to the inner surface of the through hole 33 using an adhesive. Alternatively, as a permanent magnet excitation type motor, a surface magnet type motor may be used instead of an embedded magnet type.

[0049] Both the stator core 21 and the rotor core 31 are laminated cores. For example, the stator core 21 is as follows: Figure 2 As shown, it is formed by stacking multiple electromagnetic steel plates 40 along the stacking direction.

[0050] Furthermore, the stacking thickness (along the entire length of the central axis O) of both the stator core 21 and the rotor core 31 is, for example, set to 50.0 mm. The outer diameter of the stator core 21 is, for example, set to 250.0 mm. The inner diameter of the stator core 21 is, for example, set to 165.0 mm. The outer diameter of the rotor core 31 is, for example, set to 163.0 mm. The inner diameter of the rotor core 31 is, for example, set to 30.0 mm. However, these values ​​are merely examples, and the stacking thickness, outer diameter, or inner diameter of the stator core 21, and the stacking thickness, outer diameter, or inner diameter of the rotor core 31, are not limited to these values. Here, the inner diameter of the stator core 21 is based on the front end of the teeth 23 in the stator core 21. That is, the inner diameter of the stator core 21 is the diameter of the virtual circle inscribed in the front ends of all the teeth 23.

[0051] The electromagnetic steel plates 40 that form the stator core 21 and the rotor core 31 are, for example, formed by... Figures 4-6 The raw material 1 shown is formed by punching or other processing. The raw material 1 is an electromagnetic steel sheet that serves as the base material for the electromagnetic steel sheet 40. Examples of raw material 1 include strip steel sheets or cut plates.

[0052] In the description of the laminated iron core, the following description will focus on raw material 1. Additionally, in this specification, the strip-shaped steel sheet that serves as the base material for the electromagnetic steel sheet 40 is sometimes referred to as raw material 1. Sometimes, the steel sheet formed by punching raw material 1 into a shape used in the laminated iron core is referred to as electromagnetic steel sheet 40.

[0053] (raw material 1)

[0054] Raw material 1, for example, is wound in Figure 7 The steel coil 1A shown is processed in its original state. In this embodiment, non-oriented electromagnetic steel sheet is used as raw material 1. JIS C 2552:2014 non-oriented electromagnetic steel sheet can be used as the non-oriented electromagnetic steel sheet. However, oriented electromagnetic steel sheet can also be used instead of non-oriented electromagnetic steel sheet as raw material 1. In this case, JIS C 2553:2019 oriented electromagnetic steel sheet can be used. Furthermore, JIS C 2558:2015 non-oriented thin electromagnetic steel strip or oriented thin electromagnetic steel strip can be used.

[0055] The upper and lower limits of the average plate thickness t0 of raw material 1 are also taken into account when raw material 1 is used as electromagnetic steel plate 40, and are set as follows, for example.

[0056] As the thickness of raw material 1 decreases, its manufacturing cost increases. Therefore, considering the manufacturing cost, the lower limit of the average plate thickness t0 of raw material 1 is 0.10 mm, preferably 0.15 mm, and more preferably 0.18 mm.

[0057] On the other hand, while manufacturing costs improve when raw material 1 is too thick, eddy current losses increase and core losses deteriorate when raw material 1 is used as electromagnetic steel plate 40. Therefore, considering core losses and manufacturing costs, the upper limit of the average plate thickness t0 of raw material 1 is 0.65 mm, preferably 0.35 mm, and more preferably 0.30 mm.

[0058] For example, 0.20 mm can be used to satisfy the above-mentioned range of average plate thickness t0 of raw material 1.

[0059] Furthermore, the average plate thickness t0 of raw material 1 includes not only the thickness of the base steel plate 2 (described later) but also the thickness of the insulating film 3. Moreover, the method for measuring the average plate thickness t0 of raw material 1 is, for example, according to the following method. For example, when raw material 1 is wound into a steel coil 1A, at least a portion of raw material 1 is unwound into a flat plate shape. In the unwound flat raw material 1, a predetermined position in the length direction of raw material 1 is selected (e.g., a position 10% of the total length of raw material 1 from its end edge in the length direction). At this selected position, raw material 1 is divided into 5 regions along its width direction. The plate thickness of raw material 1 is measured at 4 points that serve as the boundaries of these 5 regions. The average plate thickness at these 4 points can be taken as the average plate thickness t0 of raw material 1.

[0060] The upper and lower limits of the average plate thickness t0 of the raw material 1 can also be used as the upper and lower limits of the average plate thickness t0 of the electromagnetic steel plate 40. Furthermore, the method for measuring the average plate thickness t0 of the electromagnetic steel plate 40 is, for example, the following method: The lamination thickness of the laminated core is measured at four locations (i.e., every 90 degrees centered on the central axis O) at equal intervals along the circumference.

[0061] Divide the measured thickness at the four locations by the number of electromagnetic steel sheets 40 being stacked to calculate the thickness of each sheet. The average thickness of the four locations can be taken as the average thickness t0 of the electromagnetic steel sheet 40.

[0062] like Figure 5 and Figure 6 As shown, raw material 1 includes base material steel plate 2 and insulating film 3.

[0063] In raw material 1, both sides of the strip-shaped base steel plate 2 are covered with an insulating film 3. In this embodiment, most of the raw material 1 is formed from the base steel plate 2, and an insulating film 3 is laminated on the surface of the base steel plate 2. The insulating film 3 is thinner than the base steel plate 2.

[0064] Regarding the chemical composition of the base steel plate 2, as shown below, it contains 2.5% to 4.5% Si by mass. Furthermore, by setting the chemical composition within this range, the yield strength of the raw material 1 (electromagnetic steel plate 40) can be set, for example, to be 380 MPa or more and 540 MPa or less.

[0065] Si: 2.5%–4.5%

[0066] Al: 0.001%–3.0%

[0067] Mn: 0.05%~5.0%

[0068] Remaining components: Fe and impurities

[0069] When raw material 1 is used as the electromagnetic steel sheet 40, the insulating film 3 provides insulation between adjacent electromagnetic steel sheets 40 in the stacking direction. Furthermore, in this embodiment, the insulating film 3 has adhesive properties, bonding adjacent electromagnetic steel sheets 40 in the stacking direction. The insulating film 3 can be a single layer or a multilayer structure. More specifically, for example, the insulating film 3 can be a single layer possessing both insulation and adhesive properties, or a multilayer structure comprising a lower insulating film with excellent insulation properties and an upper insulating film with excellent adhesive properties. Additionally, the term "adhesive properties of the insulating film 3" in this embodiment refers to the ability to exhibit an adhesive strength exceeding a predetermined value under predetermined temperature conditions in a laminate composed of multiple electromagnetic steel sheets 40 stacked with the insulating film 3 sandwiched between them.

[0070] In this embodiment, the insulating film 3 covers both sides of the base steel plate 2 without gaps, covering the entire surface. However, to ensure the aforementioned insulation performance or adhesion, a portion of the insulating film 3 may not completely cover both sides of the base steel plate 2 without gaps. In other words, a portion of the insulating film 3 may be intermittently disposed on the surface of the base steel plate 2. However, to ensure insulation performance, both sides of the base steel plate 2 need to be covered by the insulating film 3 so that the entire surface is not exposed. Specifically, when the insulating film 3 does not have a lower insulating film with excellent insulation performance, but is a single layer with both insulation performance and adhesion, the insulating film 3 needs to be formed without gaps covering the entire surface of the base steel plate 2. In contrast, when the insulating film 3 is composed of multiple layers including a lower insulating film with excellent insulation performance and an upper insulating film with excellent adhesion, in addition to forming both the lower and upper insulating films across the entire surface of the base steel plate 2 without gaps, forming the lower insulating film across the entire surface of the base steel plate without gaps and intermittently setting the upper insulating film can also take into account both insulation performance and adhesion.

[0071] The coating composition constituting the lower insulating film is not particularly limited, and for example, general treatment agents such as chromic acid treatment agents and phosphate treatment agents can be used.

[0072] The insulating film 3 with adhesive properties is made of a coating composition for coating electromagnetic steel sheets, which contains epoxy resin, a first curing agent, and a second curing agent.

[0073] Before the heating and pressing during the manufacturing of laminated iron cores, the insulating film composed of the coating composition for electromagnetic steel sheets is in an uncured or semi-cured state (stage B). Due to the heating during the heating and pressing process, a curing reaction occurs, resulting in adhesive ability. The coating composition for electromagnetic steel sheets can be used to form a single-layer insulating film or to form an upper insulating film disposed on a lower insulating film.

[0074] As the epoxy resin, any general epoxy resin can be used; specifically, any epoxy resin having two or more epoxy groups per molecule can be used without particular restrictions. Examples of such epoxy resins include bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenolic resin, cresol-phenolic resin, triphenylmethane type epoxy resin, alicyclic epoxy resin, glycidyl ester type epoxy resin, glycidylamine type epoxy resin, hydantoin type epoxy resin, isocyanurate type epoxy resin, acrylic modified epoxy resin (epoxy acrylate), phosphorus-containing epoxy resin, and their halides (brominated epoxy resins, etc.) or hydrides. One type of epoxy resin can be used alone, or two or more types can be used in combination.

[0075] Relative to the total mass of the coating composition for the electromagnetic steel sheet, the epoxy resin content is preferably 30-90% by mass, more preferably 40-80% by mass, and even more preferably 50-70% by mass. When the epoxy resin content is above the lower limit mentioned above, the adhesive strength of the electromagnetic steel sheet 40 can be further improved. When the epoxy resin content is below the upper limit mentioned above, the stress and strain of the electromagnetic steel sheet 40 can be further suppressed.

[0076] The first curing agent is composed of a phenolic resin, which contains a phenolic backbone having either or both of alkyl and alkoxy groups. The phenolic resin of the first curing agent may contain only an alkyl-containing phenolic backbone, an alkoxy-containing phenolic backbone, or any one of an alkyl and alkoxy-containing phenolic backbone, or may contain two or more of these groups. The phenolic resin of the first curing agent may be either phenolic or methylform.

[0077] As the first curing agent, one type can be used alone or in combination with two or more types.

[0078] In the first curing agent, the alkyl group in the phenolic skeleton can be either straight-chain or branched.

[0079] The lower limit for the number of carbon atoms in the alkyl group of the phenolic skeleton is preferably 2, and more preferably 4. When the number of carbon atoms in the alkyl group is above the lower limit, it is easier to suppress the deterioration of the magnetic properties of the laminated iron core.

[0080] The upper limit for the number of carbon atoms in the alkyl group of the phenolic skeleton is preferably 20, more preferably 12. When the number of carbon atoms in the alkyl group is below the upper limit, the curing time of the epoxy resin can be shortened.

[0081] As a phenolic resin containing a phenolic skeleton having alkyl groups, examples of phenolic resins include those having either or both of the constituent units represented by the following formula (a-1) (hereinafter also referred to as constituent unit (a-1)) and the constituent units represented by the following formula (a-2) (hereinafter also referred to as constituent unit (a-2)).

[0082]

Chemical Formula 1

[0083]

[0084] In the above formula (a-1), R 1 It can be a hydrogen atom, methyl, ethyl, phenyl, or trifluoromethylphenyl. R 2 It is an alkyl group with 1 to 20 carbon atoms. x is an integer from 1 to 3. In formula (a-2), R 3 and R 4 It can be a hydrogen atom, methyl, ethyl, phenyl, or trifluoromethylphenyl. R 5 It is an alkyl group with 1 to 20 carbon atoms. y is 1 or 2.

[0085] In addition, the "*" in formulas (a-1) and (a-2) indicates the bonding site with the adjacent constituent unit, which bonds with a hydrogen atom when it does not bond with the adjacent constituent unit in the constituent unit located at the end of the polymer chain.

[0086] As R 1 From the perspective of manufacturing cost, hydrogen atoms are preferred.

[0087] From the perspective of crosslinking density, x is preferably 1 to 3.

[0088] As R 2 Preferably, the alkyl group has 2 to 20 carbon atoms, and more preferably, it has 2 to 12 carbon atoms.

[0089] As a constituent unit (a-1), the following constituent unit is preferred: having a -CH(R) group at either the ortho or para position of the phenolic skeleton. 1 The basis denoted by )-* has -R at the interposition. 2 The radical (alkyl) is indicated.

[0090] The phenolic resin of the first curing agent may contain one or more constituent units (a-1).

[0091] As R 3 and R4 From the perspective of manufacturing cost, hydrogen atoms are preferred.

[0092] From the perspective of crosslinking density, 1 to 3 is preferred for y.

[0093] As R 5 Preferably, the alkyl group has 2 to 20 carbon atoms, and more preferably, it has 2 to 12 carbon atoms.

[0094] As a constituent unit (a-2), the following constituent units are preferred: two or more having -CH(R) groups selected from the ortho and para positions of the phenolic skeleton. 3 The base represented by )-* and the base represented by -CH(R) 4 The group represented by )-OH has a -R group at the meta position. 5 The radical (alkyl) is indicated.

[0095] The phenolic resin of the first curing agent may contain one or more constituent units (a-2).

[0096] In the first curing agent, the alkoxy groups in the phenolic skeleton can be either straight-chain or branched.

[0097] The lower limit for the number of carbon atoms in the alkoxy group of the phenolic skeleton is preferably 2. When the number of carbon atoms in the alkoxy group is above the lower limit, the curing time of the epoxy resin can be shortened.

[0098] The upper limit for the number of carbon atoms in the alkoxy group of the phenolic skeleton is preferably 20, more preferably 12. When the number of carbon atoms in the alkoxy group is below the upper limit, it is easier to suppress the decrease in adhesive strength.

[0099] As a phenolic resin containing a phenolic skeleton having an alkoxy group, examples include phenolic resins having a constituent unit represented by the following formula (a-3) (hereinafter also referred to as constituent unit (a-3)).

[0100]

Chemical Formula 2

[0101]

[0102] In equation (a-3), R 6 and R 7 It can be a hydrogen atom, methyl, ethyl, phenyl, or trifluoromethylphenyl. R 8 It is an alkoxy group with 1 to 20 carbon atoms. R 9 It consists of hydrogen atoms or alkyl groups having 1 to 20 carbon atoms. z is 1 or 2.

[0103] In addition, the "*" in formula (a-3) indicates the bonding site with the adjacent constituent unit, which bonds with a hydrogen atom when it does not bond with the adjacent constituent unit in the constituent unit located at the end of the polymer chain.

[0104] As R 6 and R 7 From the perspective of reactivity with epoxy resin, hydrogen atoms are preferred.

[0105] From the perspective of crosslinking density, z is preferably 1 to 3.

[0106] As R 8 Preferably, the alkoxy group has 2 to 20 carbon atoms, and more preferably, it has 2 to 12 carbon atoms.

[0107] As R 9 Preferably, it is an alkyl group with 2 to 20 hydrogen atoms or carbon atoms, and more preferably, it is an alkyl group with 2 to 12 hydrogen atoms or carbon atoms.

[0108] As a constituent unit (a-3), the following constituent units are preferred: two or more having -CH(R) groups selected from the ortho and para positions of the phenolic skeleton. 6 The base represented by )-* and the base represented by -CH(R) 7 )-R 8 The base represented has -R at the interposition. 9 The radical (hydrogen atom or alkyl group) is indicated.

[0109] The phenolic resin of the first curing agent may contain one or more constituent units (a-3).

[0110] The phenolic resin used as the first curing agent is preferably a phenolic resin composed of any one or more of the constituent units (a-1) to (a-3), and more preferably an alkylphenolic resin composed of any one or both of the constituent units (a-1) and (a-2), or an alkoxyphenolic resin composed of the constituent unit (a-3). These phenolic resins are advantageous in terms of film-forming properties.

[0111] The lower limit of the weight average molecular weight (Mw) of the phenolic resin in the first curing agent is preferably 1000, more preferably 2000. When the Mw of the phenolic resin is above the lower limit, the activation period when it is applied as a treatment solution can be ensured.

[0112] The upper limit of the Mw of the phenolic resin in the first curing agent is preferably 20,000, more preferably 15,000. When the Mw of the phenolic resin is below the said upper limit, the risk of gelation is lower when it is applied to the steel sheet as a treatment solution.

[0113] In addition, Mw can be determined using polystyrene as a standard material by size-exclusion chromatography (SEC) as described in JIS K7252-1:2008.

[0114] The manufacturing method of the phenolic resin of the first curing agent is not particularly limited, and known methods can be used.

[0115] As specific examples, alkylphenolic resins composed of constituent unit (a-1) can be manufactured, for example, by polycondensation of alkylphenols with aldehydes in the presence of an acid catalyst (oxalic acid, hydrochloric acid, sulfonic acid, etc.). Alkylphenolic resins containing constituent unit (a-2) can be manufactured, for example, by polycondensation of phenols with aldehydes in the presence of an alkaline catalyst (sodium hydroxide, ammonia, amine, etc.) (methyl phenolic resinification reaction). Alkoxyphenolic resins containing constituent unit (a-3) can be manufactured, for example, by adding the alkane group (-CH(R) of constituent unit (a-2) to the alkylphenolic resin containing constituent unit (a-2) after obtaining the alkylphenolic resin containing constituent unit (a-2). 4 It is manufactured by alkoxylation of )-OH).

[0116] Alkylphenols are not particularly limited in type, and examples include methylphenol (e.g., o-methylphenol), ethylphenol (e.g., o-ethylphenol), propylphenol (e.g., p-propylphenol, p-isopropylphenol), butylphenol (e.g., p-butylphenol, p-sec-butylphenol), nonylphenol (e.g., p-nonylphenol), dodecylphenol (e.g., p-dodecylphenol), dimethylphenol (e.g., 2,3-dimethylphenol), diethylphenol (e.g., 2,3-diethylphenol), dibutylphenol (e.g., 2,6-di-sec-butylphenol), and trimethylphenol (e.g., 2,3,4-trimethylphenol). Alkylphenols can be used alone or in combination with two or more other types.

[0117] As aldehydes, they are not particularly limited; examples include formaldehyde, acetaldehyde, benzaldehyde, and salicylaldehyde. Aldehydes can be used alone or in combination with two or more.

[0118] Alcohols used for alkoxylation are not particularly limited, and examples include primary alcohols (methanol, ethanol, n-butanol, 1-nonanol, etc.), secondary alcohols (2-hexanol, 3-hexanol, 1-heptanol, 2-heptanol, 2-nonanol, etc.), and tertiary alcohols (tert-butanol, 2-methyl-2-butanol, etc.). One type of alcohol can be used alone, or two or more can be used in combination.

[0119] The content of the first curing agent in the coating composition for electromagnetic steel sheets is 5 parts by weight or more and 150 parts by weight or less relative to 100 parts by weight of epoxy resin. When the content of the first curing agent is above the lower limit, a laminated iron core with excellent magnetic properties can be obtained. When the content of the first curing agent is below the upper limit, a laminated iron core with excellent heat resistance can be obtained.

[0120] The lower limit of the content of the first curing agent is preferably 10 parts by mass or more, more preferably 12 parts by mass or more. The upper limit of the content of the first curing agent is preferably 140 parts by mass or less, more preferably 130 parts by mass or less.

[0121] The second curing agent is one or more selected from phenolic methyl resin and phenolic varnish resin. Neither the phenolic methyl resin nor the phenolic varnish resin used as the second curing agent has alkyl or alkoxy groups on its phenolic backbone.

[0122] As a second curing agent, phenolic methyl resin can be used alone, phenolic varnish resin can be used alone, or phenolic methyl resin and phenolic varnish resin can be used together.

[0123] The total content of the first curing agent and the second curing agent in the coating composition for electromagnetic steel sheets is preferably 10 to 155 parts by weight relative to 100 parts by weight of epoxy resin. When the total content of the first curing agent and the second curing agent is within the aforementioned range, it is easier to balance magnetic properties and heat resistance. If the total content of the first curing agent and the second curing agent is less than the lower limit, there is a risk that the polymerization reaction of the epoxy resin may be inhibited, leading to a deterioration in high-temperature strength. Furthermore, if the total content of the first curing agent and the second curing agent exceeds the upper limit, there is a risk that the hardness of the cured product may become excessively high, resulting in a deterioration in magnetic properties.

[0124] The lower limit of the total content of the first curing agent and the second curing agent is preferably 20 parts by mass or more, more preferably 40 parts by mass or more, and even more preferably 45 parts by mass or more. The upper limit of the total content of the first curing agent and the second curing agent is preferably 130 parts by mass or less, more preferably 100 parts by mass or less.

[0125] Based on setting the total content of the first curing agent and the second curing agent within the aforementioned range, the lower limit of the content of the second curing agent is preferably 5 parts by mass or more, more preferably 10 parts by mass or more. The upper limit of the content of the second curing agent is preferably 60 parts by mass or less, more preferably 40 parts by mass or less.

[0126] The coating composition for electromagnetic steel sheets may also contain components other than epoxy resin, the first curing agent, and the second curing agent. Examples of such components include acrylic resin, curing agents other than the first and second curing agents, curing accelerators (curing catalysts), emulsifiers, and defoamers. Furthermore, from the viewpoint of ensuring adhesive strength, the coating composition for electromagnetic steel sheets does not contain inorganic fillers such as silica, alumina, or glass.

[0127] As other ingredients, one type can be used alone, or two or more types can be used together.

[0128] The term "acrylic resin" is not particularly limited. Examples of monomers used in acrylic resins include, for instance, unsaturated carboxylic acids such as acrylic acid and methacrylic acid, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, n-butyl isobutyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl methacrylate, and hydroxypropyl methacrylate. Furthermore, the term "methacrylate" refers to either acrylate or methacrylate. One type of acrylic resin can be used alone, or two or more types can be used in combination.

[0129] Acrylic resins can also contain constituent units derived from monomers other than acrylic acid monomers. Examples of such monomers include ethylene, propylene, and styrene. These monomers can be used individually or in combination of two or more.

[0130] The glass transition point (Tg point) of acrylic resin is not particularly limited, but the lower limit is preferably -40°C, more preferably -20°C. The upper limit of the Tg point of acrylic resin is preferably 80°C, more preferably 50°C.

[0131] When the coating composition for electromagnetic steel sheets contains acrylic resin, the content of acrylic resin is not particularly limited; for example, it can be set to 1% by mass or less and 50% by mass relative to the total amount of epoxy resin and acrylic resin. The same applies when it contains acrylic-modified epoxy resin or acrylic monomer.

[0132] When using acrylic resin, it can also be used as an acrylic-modified epoxy resin obtained by grafting acrylic resin onto epoxy resin. Alternatively, it can be included as a monomer forming acrylic resin in a coating composition for electromagnetic steel sheets.

[0133] Other curing agents include latent epoxy resin curing agents that initiate the curing reaction upon heating. Specifically, examples include aromatic polyamines, acid anhydrides, dicyandiamide, boron trifluoride-amine complexes, and organic hydrazides. These other curing agents can be used alone or in combination of two or more.

[0134] Regarding the content of other curing agents in the coating composition for electromagnetic steel sheets, it is preferably 20 parts by weight or less, and more preferably 10 parts by weight or less, relative to 100 parts by weight of epoxy resin.

[0135] Generally, when ensuring bond strength at high temperatures, epoxy resin adhesives with excellent heat resistance have a large Young's modulus near room temperature, which can impose stress on the steel plate and degrade magnetic properties (core loss). On the other hand, when the resin composition is set to have moderate strength near room temperature, the heat resistance will decrease.

[0136] In this embodiment, the phenolic resin used as the first curing agent, which has either or both of alkyl and alkoxy groups, is of low elasticity. By combining such a first curing agent with a second curing agent and incorporating it into the epoxy resin, the excessive increase in the elastic modulus of the insulating film is suppressed. As a result, the stress imparted to the steel plate is reduced, thus obtaining a laminated iron core with excellent magnetic properties. Furthermore, since phenolic resin has excellent heat resistance, the heat resistance is also improved by combining the first and second curing agents. Thus, both magnetic properties and heat resistance can be achieved.

[0137] The curing shrinkage rate of the coating composition for electromagnetic steel sheets is preferably 15% or less, more preferably 12% or less, even more preferably 10% or less, and particularly preferably 8% or less. When the curing shrinkage rate is below the aforementioned upper limit, it is easy to reduce the stress imposed on the steel sheet and to obtain a laminated iron core with excellent magnetic properties.

[0138] In addition, regarding the curing shrinkage rate, it is determined by the change in film thickness according to JIS K6941.

[0139] The insulating film 3 can be formed, for example, by coating an electromagnetic steel sheet with a coating composition onto the surface of a base steel sheet and then drying and sintering it.

[0140] The lower limit of the sintering temperature is preferably 120°C or higher, more preferably 140°C or higher. The upper limit of the sintering temperature is preferably 200°C or lower, more preferably 180°C or lower. When the temperature is above the lower limit, the coating composition for the electromagnetic steel sheet will adhere sufficiently to the electromagnetic steel sheet, and peeling will be suppressed. When the temperature is below the upper limit, the curing of the epoxy resin can be suppressed, and the adhesive ability of the coating composition for the electromagnetic steel sheet can be maintained.

[0141] The lower limit of the sintering time is preferably 5 seconds or more, more preferably 10 seconds or more. The upper limit of the sintering time is preferably 60 seconds or less, more preferably 30 seconds or less. When the sintering time is above the lower limit, the coating composition for the electromagnetic steel sheet will adhere sufficiently to the electromagnetic steel sheet, and peeling will be suppressed. When the sintering time is below the upper limit, the curing of the epoxy resin can be suppressed, and the adhesive ability of the coating composition for the electromagnetic steel sheet can be maintained.

[0142] Considering that raw material 1 is used as electromagnetic steel plate 40, the upper and lower limits of the average thickness t1 of insulating film 3 can also be set as follows, for example.

[0143] When raw material 1 is used as electromagnetic steel plate 40, the average thickness t1 (thickness of each single electromagnetic steel plate 40 (raw material 1)) of insulating film 3 is adjusted to ensure the insulation performance and adhesion between the electromagnetic steel plates 40 that are stacked together.

[0144] In the case of a single-layer insulating film 3, the average thickness t1 of the insulating film 3 as a whole (the thickness of the electromagnetic steel plate 40 (raw material 1)) can be set to, for example, 1.5 μm or more and 8.0 μm or less.

[0145] In the case of a multilayer insulating film 3, the average thickness of the lower insulating film can be set to, for example, 0.3 μm or more and 2.5 μm or less, preferably 0.5 μm or more and 1.5 μm or less. The average thickness of the upper insulating film can be set to, for example, 1.5 μm or more and 8.0 μm or less.

[0146] Furthermore, regarding the method for measuring the average thickness t1 of the insulating film 3 in raw material 1, the thickness of the insulating film 3 at multiple locations can be calculated using the same consideration method as the average thickness t0 of raw material 1, and then obtained as the average of their thicknesses.

[0147] The upper and lower limits of the average thickness t1 of the insulating film 3 in the raw material 1 can also be used as the upper and lower limits of the average thickness t1 of the insulating film 3 in the electromagnetic steel plate 40.

[0148] Furthermore, the method for measuring the average thickness t1 of the insulating film 3 in the electromagnetic steel plate 40 is, for example, according to the following measurement method. For example, the electromagnetic steel plate 40 located on the outermost side in the stacking direction (the electromagnetic steel plate 40 whose surface is exposed in the stacking direction) among a plurality of electromagnetic steel plates forming a laminated core is selected. On the surface of the selected electromagnetic steel plate 40, a predetermined radial position is selected (for example, the exact midpoint between the inner and outer peripheries of the electromagnetic steel plate 40). At the selected position, the thickness of the insulating film 3 of the electromagnetic steel plate 40 is measured at four locations (i.e., every 90 degrees centered on the central axis O) spaced equally along the circumferential direction. The average value of the measured thicknesses at the four locations can be used as the average thickness t1 of the insulating film 3.

[0149] Furthermore, the reason for measuring the average thickness t1 of the insulating film 3 in the outermost electromagnetic steel plate 40 located in the stacking direction is that the insulating film 3 is made in such a way that the thickness of the insulating film 3 hardly changes at the stacking position of the electromagnetic steel plate 40 along the stacking direction.

[0150] Electromagnetic steel plate 40 is manufactured by punching the raw material 1 described above, and the electromagnetic steel plate 40 is used to manufacture the laminated iron core (stator iron core 21 or rotor iron core 31).

[0151] (Layering method for laminated iron cores)

[0152] Now, let's return to the explanation of laminated iron cores.

[0153] Multiple electromagnetic steel plates 40 forming the stator core 21 Figure 3 As shown, it is laminated by an insulating film 3.

[0154] Adjacent electromagnetic steel plates 40 in the stacking direction are bonded together by an insulating film 3 covering their entire surface. In other words, the surface of the electromagnetic steel plate 40 facing the stacking direction (hereinafter referred to as the first surface) forms the bonding region 41a covering its entire surface. However, adjacent electromagnetic steel plates 40 in the stacking direction may not be bonded together covering their entire surface. In other words, the bonding region 41a and the non-bonded region (not shown) may coexist on the first surface of the electromagnetic steel plate 40.

[0155] In this embodiment, the plurality of electromagnetic steel plates forming the rotor core 31 are made of Figure 1 The riveted parts 42 (pins) shown are fixed to each other. However, the multiple electromagnetic steel plates forming the rotor core 31 can also have a laminated structure fixed by the insulating film 3, just like the stator core 21.

[0156] Alternatively, the stator core 21 and rotor core 31, etc., can be formed by so-called rotary stacking.

[0157] (Manufacturing method of laminated iron core)

[0158] The stator core 21 is, for example, used as... Figure 7 The manufacturing apparatus 100 shown is used to manufacture the core. Hereinafter, when describing the manufacturing method, the manufacturing apparatus 100 (hereinafter referred to as manufacturing apparatus 100) will be described first.

[0159] In the manufacturing apparatus 100, raw material 1 is fed from steel coil 1A (coil) in the direction of arrow F and is punched multiple times by dies arranged on each worktable, gradually forming the shape of an electromagnetic steel sheet 40. Then, the punched electromagnetic steel sheets 40 are stacked and heated while being pressurized. As a result, adjacent electromagnetic steel sheets 40 in the stacking direction are bonded together by the insulating film 3 (that is, the portion of the insulating film 3 located in the bonding area 41a exerts its adhesive ability), and the bonding is completed.

[0160] like Figure 7 As shown, the manufacturing apparatus 100 includes a multi-stage punching station 110. The punching station 110 can be two-stage or three-stage or more. Each punching station 110 includes: a die 111 disposed below the raw material 1; and a punch 112 disposed above the raw material 1.

[0161] The manufacturing apparatus 100 also includes a stacking station 140 located downstream of the downstream blanking station 110. The stacking station 140 includes a heating device 141, an outer peripheral blanking die 142, a heat insulation component 143, an outer peripheral blanking punch 144, and a spring 145.

[0162] The heating device 141, the outer peripheral blanking die 142, and the heat insulation member 143 are arranged below the raw material 1. On the other hand, the outer peripheral blanking punch 144 and the spring 145 are arranged above the raw material 1. In addition, reference numeral 21 indicates the stator core.

[0163] In the manufacturing apparatus 100 having the configuration described above, firstly, from the steel coil 1A along... Figure 7 The raw material 1 is sequentially fed out in the direction of arrow F. Then, for this raw material 1, it undergoes sequential punching processing at multi-stage punching stations 110. Through these punching processes, for raw material 1, a product is obtained. Figure 3 The shape of the electromagnetic steel plate 40 shown is that it has an iron core back 22 and multiple teeth 23. However, at this point in time, it has not been punched at all, so it proceeds to the next process in the direction of arrow F.

[0164] Then, finally, the raw material 1 is fed to the stacking station 140, punched by the outer peripheral punching punch 144, and stacked with high precision. During this stacking, the electromagnetic steel sheet 40 is subjected to a certain pressure due to the spring 145. By repeating the punching process and the stacking process as described above in sequence, a predetermined number of electromagnetic steel sheets 40 can be stacked. Furthermore, the stacked iron core formed by stacking the electromagnetic steel sheets 40 in this way is heated to a temperature of 200°C, for example, by the heating device 141. Through this heating, the insulating film 3 of adjacent electromagnetic steel sheets 40 is bonded to each other (bonding process).

[0165] The conditions for the bonding process are not particularly limited. For example, the heating temperature in the bonding process is preferably 120 to 250°C. The heating time in the bonding process is affected by the size of the laminated core or the heating method, but is preferably, for example, 30 seconds to 120 minutes. Alternatively, the insulating films 3 can be bonded together by applying pressure to the laminate. The pressure and time for applying pressure to the laminate are preferably, for example, 2 to 300 MPa and 30 seconds to 120 minutes.

[0166] Alternatively, the heating device 141 may not be disposed in the outer peripheral blanking die 142. That is, the electromagnetic steel plates 40 stacked in the outer peripheral blanking die 142 may be removed from the outer peripheral blanking die 142 before bonding. In this case, the heat insulation member 143 may not be present in the outer peripheral blanking die 142. Furthermore, in this case, the electromagnetic steel plates 40 to be bonded may be clamped and held from both sides in the stacking direction using a clamp (not shown) before being conveyed or heated.

[0167] Through the above processes, the stator core 21 is completed.

[0168] As explained above, in this invention, an insulating film is formed on the surface of an electromagnetic steel sheet using a coating composition comprising epoxy resin, a first curing agent, and a second curing agent in a specific ratio. This allows for the simultaneous achievement of excellent magnetic properties (core loss) of the laminated core and excellent heat resistance, maintaining the bonding strength between the electromagnetic steel sheets even at high temperatures during operation.

[0169] Furthermore, the technical scope of the present invention is not limited to the described embodiments, and various modifications can be made without departing from the spirit of the present invention.

[0170] The shape of the stator core is not limited to the form shown in the embodiment. Specifically, it can be designed arbitrarily according to the desired characteristics of the rotating motor, such as the outer and inner diameters of the stator core, the stack thickness, the number of slots, the circumferential and radial dimensional ratio of the teeth, and the radial dimensional ratio of the teeth to the back of the core.

[0171] In the rotor of the described embodiment, two permanent magnets 32 in a group form one magnetic pole, but the present invention is not limited thereto. For example, one permanent magnet 32 ​​may form one magnetic pole, or three or more permanent magnets 32 may form one magnetic pole.

[0172] In the above embodiments, a permanent magnet excitation type motor is used as an example of the rotary motor 10. However, the structure of the rotary motor 10 is not limited to this, as illustrated below. Furthermore, various known structures not illustrated below can also be adopted.

[0173] In the above embodiments, a permanent magnet excitation type motor was described as an example of the rotary motor 10, but the present invention is not limited thereto. For example, the rotary motor 10 may also be a reluctance type motor or an electromagnet excitation type motor (winding excitation type motor).

[0174] In the above embodiments, a synchronous motor was described as an example of an AC motor, but the present invention is not limited thereto. For example, the rotary motor 10 may also be an induction motor.

[0175] In the above embodiment, an AC motor was used as an example of a rotary motor 10, but the present invention is not limited thereto. For example, the rotary motor 10 may also be a DC generator.

[0176] In the above embodiment, an electric motor was described as an example of a rotary motor 10, but the present invention is not limited thereto. For example, the rotary motor 10 may also be a generator.

[0177] Furthermore, the constituent elements in the embodiments can be appropriately replaced with well-known constituent elements without departing from the spirit of the invention. In addition, the modified examples can be appropriately combined.

[0178] Example

[0179] Hereinafter, the effects of one aspect of the present invention will be specifically described according to an embodiment. However, the conditions in the embodiment are merely examples of conditions adopted to confirm the feasibility and effects of the present invention, and the present invention is not limited to the following description. Various conditions can be adopted by the present invention as long as they do not depart from the spirit of the present invention and achieve the purpose of the present invention.

[0180] [raw material]

[0181] The raw materials used in the examples are shown below.

[0182] (Epoxy resin)

[0183] E1: Bisphenol A type epoxy resin

[0184] E2: Bisphenol F type epoxy resin

[0185] E3: Triphenylmethane type epoxy resin

[0186] (First curing agent)

[0187] A1: Alkylphenol resin (constituent unit (a-1), R) 1 Hydrogen atom, R 2 (Meso): -(CH2)3CH3, x=1, Mw=7000)

[0188] A2: Alkylphenol resin (constituent unit (a-1), R) 1 Hydrogen atom, R 2 (Meta): -(CH2)8CH3, x=2, Mw=3000)

[0189] A3: Alkoxyphenol resin (constituent unit (a-3), R) 6 Hydrogen atom, R 7 Hydrogen atom, R 8 (Meta): -ortho C(CH3)2-CH2CH3, z=1, R 9 (Hydrogen atom, Mw = 14000)

[0190] (Second curing agent)

[0191] H1: Phenolic resin (stage A)

[0192] H2: Phenolic varnish resin

[0193] (Curing agent (comparison object))

[0194] B1: Diaminodiphenylmethane

[0195] (Combining agents)

[0196] M1: Acrylic resin (Methyl methacrylate: Isobutyl acrylate: Styrene: 2-ethylhexyl acrylate (molar ratio = 40:20:20:10, glass transition temperature: 32℃)

[0197] M2: Acrylic resin (methyl methacrylate units: n-butyl acrylate units (molar ratio) = 55:45, glass transition temperature: 10℃)

[0198] [Magnetic properties]

[0199] Rectangular electromagnetic steel sheets (single sheets) with dimensions of 55mm × 55mm were cut from the electromagnetic steel strips in each example. Ten electromagnetic steel sheets were stacked and bonded together under the conditions of steel sheet temperature of 200℃, pressure of 10MPa, and pressing time of 1 hour to produce a laminated iron core. For the obtained laminated iron core, the magnetic properties of the single sheet in the rolling direction and in the direction perpendicular to the rolling direction were measured according to the single sheet magnetic measurement method of JIS C2556 (2015), and the average value of their values ​​was used as the magnetic property. In addition, as a magnetic property (magnetism) and as an iron loss, "W10 / 400 (W / kg)" was evaluated. "W10 / 400" is the iron loss at a frequency of 400Hz and a maximum magnetic flux density of 1.0T.

[0200] [Adhesion strength]

[0201] Two rectangular electromagnetic steel sheets (single sheets) with a width of 30 mm and a length of 60 mm were cut from the electromagnetic steel strips in each example. Next, an electromagnetic steel sheet coating composition was applied to the surface, and the front ends (30 mm wide x 10 mm long) were overlapped and pressurized to produce a sample for testing. The pressurization conditions were set as follows: steel sheet temperature 200°C, pressure 10 MPa, and pressurization time 1 hour.

[0202] For the obtained samples, the tensile speed was set to 2 mm / min under an atmosphere temperature of 25℃ or 150℃. The maximum load (N) until peeling was measured, and the value obtained by dividing the maximum load (N) by the bonded area was taken as the bond strength (MPa).

[0203] [Curing shrinkage rate]

[0204] Electromagnetic steel sheet coating compositions were applied to the surface of each example of electromagnetic steel strip, and the curing shrinkage rate was measured. The curing shrinkage rate was measured according to JIS K 6941, based on changes in film thickness.

[0205] [determination]

[0206] For each case, the following criteria were used for evaluation. Furthermore, lower iron loss indicates that the stress and strain imparted to the electromagnetic steel sheet are more suppressed. The measurement and evaluation results are shown in Table 2. Values ​​outside the scope of the invention are underlined in the table.

[0207] [Benchmark]

[0208] "Good": The bond strength at 25°C is ≥5.0 MPa, the bond strength at 150°C is ≥1.0 MPa, and the magnetic property is less than 12.0 W / kg. Furthermore, regarding the magnetic property, it is more preferable to have a magnetic property of ≤11.5 W / kg.

[0209] "Poor": The bonding strength at 25℃ is less than 5.0MPa, the bonding strength at 150℃ is less than 1.0MPa, or the magnetic properties are above 12.0W / kg.

[0210] [Example 1]

[0211] The base steel sheet used was a non-oriented electromagnetic steel sheet with a thickness of 0.25 mm and a width of 100 mm, containing Si: 3.0%, Mn: 0.2%, Al: 0.5% by mass, with the remainder consisting of Fe and impurities.

[0212] The components shown in Table 1 were mixed to prepare a coating composition for electromagnetic steel sheets. The obtained coating composition for electromagnetic steel sheets was coated onto the surface of a base steel sheet and sintered at 160°C for 20 seconds, thereby obtaining an electromagnetic steel strip with an insulating film having an average thickness of 3 μm.

[0213] [Examples 2-8, Comparative Examples 1-8]

[0214] Except for changes to the composition and sintering conditions of the coating composition for the electromagnetic steel sheet, as shown in Table 1, electromagnetic steel strips were obtained in the same manner as in Example 1.

[0215] The composition and sintering conditions of the coating compositions for each example of electromagnetic steel sheet are shown in Table 1. The evaluation results of the magnetic properties (magnetism) and bond strength for each example are shown in Table 2.

[0216] Table 1

[0217]

[0218] Table 2

[0219]

[0220] As shown in Table 2, in Examples 1 to 8, which are obtained by combining epoxy resin, first curing agent and second curing agent in a specific ratio, sufficient bonding strength is ensured even at 150°C. In addition to excellent heat resistance, the magnetic properties are also relatively good.

[0221] On the other hand, in Comparative Examples 1 and 6 which do not contain the first curing agent, Comparative Examples 2 to 5 where the content of the first curing agent is outside the scope of the present invention, and Comparative Examples 7 and 8 which do not contain the second curing agent, it is impossible to simultaneously achieve both heat resistance and magnetic properties.

[0222] Industrial availability

[0223] According to the present invention, both the heat resistance and magnetic properties of the laminated iron core can be achieved. Therefore, it has great industrial applicability.

[0224] Explanation of reference numerals in the attached figures

[0225] 1…Raw materials, 2…Base steel plate, 3…Insulating film, 10…Rotating motor, 20…Stator, 21…Stator core, 40…Electromagnetic steel plate.

Claims

1. A coating composition for electromagnetic steel sheets, comprising an epoxy resin, a first curing agent, and a second curing agent, wherein the first curing agent is composed of a phenolic resin having a phenolic skeleton having any one or both of alkyl and alkoxy groups, and the second curing agent is one or more selected from phenolic methyl resins and phenolic varnish resins. The content of the first curing agent is between 5 and 150 parts by weight relative to 100 parts by weight of epoxy resin. The total content of the first curing agent and the second curing agent is between 10 and 155 parts by weight relative to 100 parts by weight of the epoxy resin.

2. The coating composition for electromagnetic steel sheets as described in claim 1, wherein, The first curing agent is composed of a phenolic resin, which contains a phenolic skeleton having any one or both of an alkyl group having 2 or more carbon atoms and an alkoxy group having 2 or more carbon atoms.

3. The coating composition for electromagnetic steel sheets as described in claim 1 or 2, wherein, The curing shrinkage rate is less than 15%.

4. An electromagnetic steel sheet having an insulating film on its surface, the insulating film comprising the coating composition for electromagnetic steel sheets as described in any one of claims 1 to 3.

5. A laminated iron core, wherein, Multiple electromagnetic steel plates as described in claim 4 are stacked and bonded together.

6. A rotary electric motor comprising the laminated iron core as described in claim 5.

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