Adhesive coated magnets, magnet assemblies and electrical devices

Abstract

The present invention relates to an adhesive-coated magnet, a magnet assembly, and an electric device. The magnet includes a magnetic substrate and an adhesive coating, the adhesive coating being applied to at least a portion of the outer surface of the magnetic substrate. The adhesive coating is obtained by applying an adhesive composition, the adhesive composition including a base resin and an expansion agent, the expansion agent being located near the magnetic substrate in the adhesive coating, and the height of the expansion agent distribution is 50% or less of the cross-sectional thickness of the adhesive coating. The adhesive-coated magnet of the present invention has excellent adhesion.

Description

[Technical Field]

[0001] The present invention relates to the field of polymeric materials, and in particular to adhesive coated magnets, magnet assemblies, and electrical devices. [Background technology]

[0002] As permanent magnet motors are widely used in new energy vehicles, motor magnet assembly is one of the key processes in the production of new energy vehicles. A fastening method that can achieve a higher bonding force between the magnet and the core in the motor is a technical issue that needs to be resolved as soon as possible.

[0003] Currently, it is common to apply an adhesive to the magnet and / or core, then bond the magnet and core together and cure the adhesive to form a hardened adhesive coating between the magnet and core. The bonding strength between the adhesive coating and magnet, the bonding strength between the adhesive and core, and the strength of the adhesive itself are all important factors that affect the bonding strength between the magnet and core.

[0004] For example, CN102934329A discloses a motor rotor that includes a rotor core, a permanent magnet, and a rotor shaft, in which the permanent magnet is fixed with a resin material filled between the inner wall of a permanent magnet insertion hole in the rotor core and the side surface of the permanent magnet, thereby achieving adhesion between the magnet and the rotor core.

[0005] As another example, CN106824730A discloses that a powder coating made from a thermosetting bisphenol A type epoxy polyester resin powder, p-toluenesulfonylhydrazide expanding agent, and dimethylimidazole curing agent is applied to the surface of a magnet, intermediately cured at 70 to 120°C, inserted into a motor slot, and finally cured at 120 to 200°C, thereby achieving adhesion between the magnet and the slot.

[0006] As another example, Patent Document No. JP2007174872A discloses that a resin that is solid at room temperature is used, and in order to improve the impact resistance of the adhesive sheet, a foamed resin sheet is produced by adding a foaming agent to the resin, resulting in a cured material containing bubbles inside. By using a foamed resin sheet instead of a liquid adhesive, problems such as adhesive leakage, uneven adhesive application, and adhesive deformation or peeling can be overcome, and assembly efficiency and processing accuracy can be improved.

[0007] However, the bond strength between the magnet and the core in conventional motors needs to be further improved. Summary of the Invention

[0008] This Summary section is provided to introduce in simplified form concepts that are described in detail in the Detailed Description section below. This Summary section is not intended to identify key features or required features of the claimed technical solution, nor is it intended to be used to limit the scope of the claimed technical solution.

[0009] In a first aspect, the present invention provides an adhesive-coated magnet, the magnet comprising a magnetic substrate and an adhesive coating, the adhesive coating being applied to at least a portion of the outer surface of the magnetic substrate, the adhesive coating being obtained by applying an adhesive composition comprising a base resin and an expansion agent, the expansion agent being proximate the magnetic substrate in the adhesive coating, and the height of the expansion agent distribution being 50% or less of the cross-sectional thickness of the adhesive coating.

[0010] In a second aspect, the present invention provides a magnet assembly including a magnet and a core, with an adhesive layer between the magnet and the core obtained by heat-curing an adhesive coating at 150 to 200°C, the adhesive layer obtained by heat-curing having expanded bubbles near the magnetic substrate, and the height of the distribution of the expanded bubbles being 80% or less of the cross-sectional thickness of the adhesive layer obtained by heat-curing.

[0011] In a third aspect, the present invention provides an electrical device comprising the magnet assembly described above.

[0012] By using the above technical means, the present invention uses a magnet with an adhesive coating to improve the adhesion between the adhesive layer and the core after expansion.

[0013] Other features and advantages of the present invention are described in detail in the detailed description section below. [Brief explanation of the drawings]

[0014] These and other features, advantages, and aspects of embodiments of the present invention will become more apparent with reference to the following specific embodiments in conjunction with the drawings, which are to be understood as being schematic and in which components and elements are not necessarily drawn to scale.

[0015] [Figure 1] 1 is a schematic diagram of an adhesive coated magnet before and after expansion. [Figure 2] 1 is an electron microscope photograph of the cross-sectional structure of the adhesive coating of the magnet of Example 1 before expansion. [Figure 3] 1 is an electron microscope photograph of the cross-sectional structure of the adhesive coating of the magnet of Example 1 after expansion. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Although the drawings show several embodiments of the present invention, it should be understood that the present invention can be realized in various forms and should not be construed as being limited to the embodiments described herein, but rather, these embodiments are provided for a more thorough and complete understanding of the present invention. It should be understood that the drawings and embodiments of the present invention are for illustrative purposes only and are not intended to limit the protection scope of the present invention.

[0017] It should be understood that the steps recited in the method embodiments of the present invention may be performed in various orders and / or in parallel, and that method embodiments may include additional steps and / or omit performing steps as shown, and the scope of the present invention is not limited in this respect.

[0018] The present invention provides an adhesive-coated magnet, comprising a magnetic substrate and an adhesive coating, the adhesive coating being applied to at least a portion of the outer surface of the magnetic substrate, the adhesive coating being obtained by applying an adhesive composition comprising a base resin and an expansion agent, the expansion agent being located near the magnetic substrate in the adhesive coating, and the height of the expansion agent distribution being 50% or less of the cross-sectional thickness of the adhesive coating.

[0019] Optionally, the deposition method includes at least one of dip coating, blade coating, brush coating, roll coating, stamp coating, or spray coating.

[0020] Optionally, the adhesive coating is obtained by pre-curing the adhesive composition after application, the pre-curing temperature being 40-90°C.

[0021] Optionally, the adhesive composition is in the form of a powder, a liquid, a cloudy liquid, or the like.

[0022] Optionally, the swelling agent is at least one of expandable microspheres, diazoaminobenzene, ammonium polyphosphate, azodicarbonamide, ammonium carbonate, and sodium bicarbonate.

[0023] Optionally, according to one embodiment of the present invention, the expansion agent is concentrated in the middle and lower portions of the adhesive coating and is close to the surface of the magnetic substrate, ensuring that the expansion spaces having the bubble form formed during the expansion of the adhesive coating are as far away as possible from contact with the core, increasing the contact area between the base resin in the adhesive coating and the core, and improving the bonding strength between the adhesive layer and the core after expansion.

[0024] Optionally, the adhesive coating has a thickness of 80-150 μm, a softening point of 60-80° C., and an expansion rate of 80%-200%.

[0025] According to one embodiment of the present invention, after the adhesive coating expands without pressure, the expansion space (height of the expanded bubbles) having the bubble shape formed during the expansion of the adhesive coating becomes closer to the magnetic substrate, and the base resin in the adhesive coating accumulates more on the side farther from the magnetic substrate, which has been fully proven to improve the adhesion of the adhesive coating.

[0026] Optionally, the content of the swelling agent is 0.5 to 20 parts by weight based on 100 parts by weight of the base resin.

[0027] Optionally, the expansion agent is a coated expandable microsphere, which comprises uncoated expandable microspheres and a coating layer covering the outer surface of the uncoated expandable microspheres. The uncoated expandable microspheres comprise a polymer shell and an expandable matrix encapsulated in the polymer shell. The coating layer comprises a coating resin and a heavy inorganic filler embedded in the coating resin. The particle size of the uncoated expandable microspheres is 3 to 30 μm. The coating resin is a thermoplastic resin having a softening point of 40 to 100°C, preferably at least one of acrylic resin, polysulfone resin, and melamine formaldehyde resin. The particle size of the heavy inorganic filler is 0.5 to 30 μm, and the compressed density is 3.1 to 7.8 g / cm. 3The heavy inorganic filler comprises at least one of a carbonate, a phosphate, a polyphosphate, a metal oxide, and a non-metallic compound, wherein the carbonate is preferably at least one of calcium carbonate, magnesium carbonate, and zinc carbonate, the phosphate is preferably at least one of calcium phosphate and sodium phosphate, the polyphosphate is preferably at least one of calcium polyphosphate and aluminum polyphosphate, the metal oxide is preferably at least one of aluminum oxide, rare earth oxide, and triiron tetroxide, and the non-metallic compound is preferably at least one of silicon dioxide, silicon nitride, and silicon carbide.

[0028] Optionally, the content of the coating resin is 0.1 to 1.8 parts by weight and the content of the heavy inorganic filler is 1 to 15 parts by weight, relative to 1 part by weight of the uncoated expandable microspheres.

[0029] By increasing the density of coated expandable microspheres with a heavy inorganic filler, the coated expandable microspheres are concentrated in the lower and middle portions of the adhesive coating due to gravity, closer to the surface of the magnetic substrate. The liquid alkane filled in the polymer shell of conventional uncoated expandable microspheres has a low density and is generally uniformly suspended throughout the adhesive coating. Coated expandable microspheres are obtained by mixing uncoated expandable microspheres with a heavy inorganic filler, and the density of the expandable microspheres is adjusted by controlling the density range of the heavy inorganic filler. As the density increases, the volume increases relatively and the buoyancy decreases, causing the coated expandable microspheres to concentrate in the lower and middle portions of the adhesive composition. Before applying the adhesive composition to the magnetic substrate, the adhesive composition is stirred to ensure that the coated expandable microspheres are more uniformly dispersed in the adhesive composition. After applying the adhesive composition to the magnetic substrate, the coated expandable microspheres settle and concentrate in the lower and middle portions of the adhesive coating due to gravity during the standing and pre-curing process. This ensures that the bubble-shaped expansion space formed during the expansion of the adhesive coating is as far away as possible from contact with the core, increasing the contact area between the base resin in the adhesive coating and the core, and improving the bonding strength between the adhesive layer and the core after expansion.

[0030] Optionally, the expandable microspheres can be prepared by mixing uncoated expandable microspheres, a heavy inorganic filler, and a coating resin, followed by spray-drying the mixture at a temperature of 40-60°C for 0.1-2 minutes.

[0031] In the present invention, by adding a coating resin to uncoated expandable microspheres and a heavy inorganic filler, the coating resin exerts its mediating and adhesive effects, allowing the heavy inorganic filler to completely adhere to the surface of the polymer shell of the uncoated expandable microspheres. Furthermore, by producing the coated expandable microspheres using a spray drying method, separation of the heavy inorganic filler and the uncoated expandable microspheres can be further prevented.

[0032] Optionally, the base resin comprises a thermosetting resin and a thermoplastic resin, and the weight ratio of the thermoplastic resin to the thermosetting resin is 1:1-10, preferably 1:2-8. The thermosetting resin is at least one of an epoxy resin, a hydroxyacrylic resin, and a polyurethane resin. The epoxy resin is any one of a bisphenol A epoxy resin, a bisphenol F epoxy resin, and a bisphenol S epoxy resin. Preferably, the epoxy resin is an acrylic acid-modified epoxy resin, and more preferably, an acrylic acid-modified aqueous bisphenol S epoxy resin. The thermoplastic resin is at least one of an acrylic resin, a polysulfone resin, and a melamine formaldehyde resin.

[0033] Optionally, the acrylic acid modifying group in the acrylic acid modified epoxy resin includes acrylic acid carboxyl monomers, acrylic acid hydroxy monomers, and other monomers. The acrylic carboxyl monomer contains either an acrylic acid group, a methylene succinic acid group, or a methacrylic acid group. The acrylic hydroxy monomer contains either a glycidyl methacrylate group or a methyl methacrylate group. The other monomer contains either a hydroxymethylacrylamide group or a styrene group.

[0034] Optionally, the adhesive composition further comprises reinforcing resin particles, the reinforcing resin particles comprising a light inorganic filler, a highly adhesive resin and a dispersible resin attached to the light inorganic filler, and a filler gas encapsulated in the highly adhesive resin and the dispersible resin.

[0035] Optionally, the reinforcing resin particles are obtained by mixing a light inorganic filler, a high adhesive resin, a dispersing resin and a solvent to obtain a mixture, and spray drying the mixture.

[0036] Optionally, the light inorganic filler is at least one of fumed silica and fumed alumina. The highly adhesive resin is at least one of β-hydroxyethyl acrylate resin, hydantoin epoxy resin, and tripolyphosphazene epoxy resin. The dispersible resin is a thermoplastic resin having a softening point of 40 to 100°C, and is preferably at least one of acrylic resin, methacrylic resin, polysulfone resin, melamine formaldehyde resin, and polyolefin resin. The filler gas is at least one of air, nitrogen, carbon dioxide, hydrogen, and helium.

[0037] Optionally, the particle size of the reinforcing resin particles is 0.5 to 30 μm. The content of the high adhesive resin is 1 to 8 parts by weight, and the content of the dispersing resin is 1 to 10 parts by weight, relative to 1 part by weight of the light inorganic filler.

[0038] Optionally, the specific surface area of ​​the light inorganic filler is 150~400m 2 / g, and the compressed density is 0.02 to 0.20 g / cm 3 The molecular weight of the β-hydroxyethyl acrylate resin is 5,000 to 50,000 daltons, and preferably 10,000 to 21,000 daltons.

[0039] In the present invention, the addition of light inorganic fillers such as fumed silica and / or fumed alumina allows the high affinity and surface tension of the light inorganic fillers to sufficiently adsorb and fix the highly adhesive resin to the reinforced resin particles, and their low density allows the overall density of the reinforced resin particles to be sufficiently reduced. The addition of a filler gas allows the reinforced resin particles to overcome the effects of gravity during heating and increase their buoyancy. The synergistic effect of the light inorganic filler and the filler gas allows the reinforced resin particles to concentrate vertically and distribute uniformly horizontally on the surface of the adhesive coating, and further float during heating, overcoming the effects of gravity and partial inhibition by the base resin.

[0040] In the present invention, by adding a highly adhesive resin, the adhesive strength of the reinforcing resin particles can be effectively increased, and the collapse of the expansion space can be prevented.

[0041] Optionally, according to one embodiment of the present invention, the content of the reinforcing resin particles is 1-15 parts by weight relative to 100 parts by weight of the base resin.

[0042] Optionally, according to one embodiment of the present invention, the weight ratio of thermoplastic resin to thermosetting resin is 1:1-10, preferably 1:2-8.

[0043] Optionally, according to one embodiment of the present invention, the adhesive composition further comprises an additive, and the additive is at least one of a leveling agent, an anti-settling agent, a dispersant, an anti-foaming agent, a curing agent, a coalescing agent, and a medium inorganic filler. The leveling agent is at least one of a silicone oil leveling agent and an organosiloxane leveling agent. The content of the additive is 1 to 9 parts by weight per 100 parts by weight of the base resin. The anti-settling agent is at least one of a silica anti-settling agent and an organic bentonite anti-settling agent. The anti-foaming agent is at least one of a polysiloxane anti-foaming agent and a fatty acid ester anti-foaming agent. The dispersing agent is at least one of a magnesium stearate dispersant and a sodium oleate dispersant. The coalescing agent is at least one of an ethylene glycol butyl ether coalescing agent and a propylene glycol butyl ether coalescing agent. The curing agent is at least one of a phenolic resin curing agent and an aliphatic polyamine curing agent, and the aliphatic polyamine curing agent is at least one of ethylenediamine, diethylenetriamine, and triethylenetetramine. The particle size of the medium-weight inorganic filler is 0.5 to 30 μm, and the compressed density is 2.1 to 3.0 g / cm. 3 and preferably at least one of calcium oxide, zinc oxide, calcium carbonate, and inorganic fibers, and the inorganic fibers are at least one of carbon fibers, metal fibers, and glass fibers.

[0044] The present invention further provides a magnet assembly, which includes the above-mentioned magnet and a core, and has an adhesive layer between the magnet and the core obtained by thermally curing an adhesive coating at 150 to 200°C. The shear strength of the adhesive coating is 1 to 15 MPa at room temperature and 1 to 10 MPa at high temperatures of 120 to 180°C.

[0045] Optionally, the adhesive layer obtained by heat curing has expanded bubbles near the magnetic substrate, and the height of the expanded bubbles is 80% or less of the cross-sectional thickness of the adhesive layer obtained by heat curing. It has been well proven that after the adhesive coating expands in the absence of pressure, the expanded spaces (height of the expanded bubbles) having the bubble morphology formed during the expansion of the adhesive coating are closer to the magnetic substrate, and the base resin in the adhesive coating accumulates more on the side farther from the magnetic substrate, thereby improving the adhesion of the adhesive coating.

[0046] The present invention further provides an electric device, which includes the magnet assembly described above.

[0047] The present invention will now be described in more detail with reference to the following examples. Unless otherwise specified, all raw materials used in the examples are commercially available.

[0048] In the following examples and comparative examples of the present invention, the test methods for the samples are as follows.

[0049] Expansion rate test conditions: The magnet with adhesive coating is heated to 180°C for 30 minutes without pressure (when not assembled with the core), and the change in thickness of the adhesive coating is recorded. Here, expansion rate (%) = (thickness of adhesive coating after expansion - thickness of adhesive coating before expansion) / thickness of adhesive coating before expansion.

[0050] Neutral salt spray test conditions: 35°C, NaCl aqueous solution concentration (5±0.5)%, pH 6.5~7.2, spray NaCl aqueous solution to form salt mist, which is then attached to the magnet product under test, and record the time when rust begins to appear on the magnet surface.

[0051] Shear strength test conditions: GB / T7124-2008 (Determination of adhesive tensile shear strength (rigid material vs. rigid material)).

[0052] Oil resistance test conditions: NdFeB magnet products are completely immersed in transmission oil at 150°C, and the magnet surface is observed for rust, swelling, peeling, etc. The time when the coating on the magnet surface begins to change is recorded and the performance of the magnet coating is measured. If there is no effect, this time is considered the oil resistance time.

[0053] Example 1 Preparation of coated expandable microspheres: One part by weight of uncoated expandable microspheres (particle size 5-15 μm) was dissolved in a heavy inorganic filler (calcium polyphosphate, particle size 20-30 μm, compressed density 3.14 g / cm) under the condition that the solvent was ethanol. 3 ) and 0.5 parts by weight of a coating resin (acrylic resin) to obtain a mixture, which was then spray-cooled and dried at 60°C for 1 minute to obtain coated expandable microspheres.

[0054] Preparation of adhesive composition: 80 parts by weight of acrylic acid-modified aqueous bisphenol S-type epoxy resin (molecular weight 20,000 daltons, modifying groups selected from itaconic acid, acrylic acid, hydroxymethylacrylamide, and glycidyl methacrylate, and initiator dibenzoyl peroxide) was mixed with 20 parts by weight of aqueous acrylic resin, 8 parts by weight of coated expandable microspheres, 1 part by weight of phenolic resin curing agent, 0.2 part by weight of organosiloxane leveling agent, and 0.2 part by weight of ethylene glycol butyl ether film-forming agent in a water-based solvent at a stirring speed of 500 rpm to obtain an adhesive composition.

[0055] As shown in FIG. 1, the adhesive composition was applied to a magnetic substrate (NdFeB magnet) by brush coating and allowed to stand at 50° C. for 20 minutes for pre-curing, resulting in an adhesive coating with a thickness of 100 μm.

[0056] A silicon steel core was assembled to the adhesive coating and heat cured at 200° C. to obtain a magnet assembly designated Sample 1.

[0057] When the cross-sectional structure of the adhesive coating of the magnet of this example was observed with an electron microscope, it was found that the expansion agent in the adhesive coating was located near the magnetic substrate, and the height of the expansion agent distribution was less than 50% of the cross-sectional thickness of the adhesive coating, as shown in Figure 2.

[0058] The adhesive coating of the magnet of this example was allowed to expand freely at 200°C in an unpressurized state (without the core attached), and its cross-sectional structure was then observed under an electron microscope. As shown in Figure 3, it was found that the adhesive layer obtained by heat curing had expanded bubbles near the magnetic substrate, and that the height of the distribution of the expanded bubbles was less than 80% of the cross-sectional thickness of the adhesive layer obtained by heat curing.

[0059] Example 2 Preparation of coated expandable microspheres: One part by weight of uncoated expandable microspheres (particle size 5-15 μm) was dissolved in aluminum polyphosphate (particle size 0.2-5 μm, compressed density 3.2 g / cm), a heavy inorganic filler, under the condition that the solvent was ethanol. 3 The mixture was then spray-dried at 60°C for 1 minute to obtain coated expandable microspheres.

[0060] Preparation of adhesive composition: 80 parts by weight of acrylic acid-modified aqueous bisphenol F epoxy resin (molecular weight 20,000 daltons, modifying groups selected from itaconic acid, acrylic acid, hydroxymethylacrylamide, and glycidyl methacrylate, and initiator dibenzoyl peroxide) was mixed with 20 parts by weight of aqueous acrylic resin, 12 parts by weight of coated expandable microspheres, 1 part by weight of phenolic resin curing agent, 0.2 part by weight of organosiloxane leveling agent, and 0.2 part by weight of ethylene glycol butyl ether film-forming agent in a water-based solvent at a stirring speed of 500 rpm to obtain an adhesive composition.

[0061] The adhesive composition was applied to a magnetic substrate (NdFeB magnet) by stamp coating and allowed to stand at 50° C. for 20 minutes for pre-curing, resulting in an adhesive coating with a thickness of 60 μm.

[0062] A silicon steel core was assembled to the adhesive coating and heat cured at 200° C. to obtain a magnet assembly designated Sample 2.

[0063] Example 3 Preparation of reinforced resin particles: A light inorganic filler (fumed silica, specific surface area 150 m) was added under the condition that the solvent was ethanol. 2 / g, compressed density 0.05g / cm 3 One part by weight of the cellulose acetate copolymer was mixed with 3 parts by weight of a highly adhesive resin (β-hydroxyethyl acrylate resin, molecular weight 21,000 daltons) and 7 parts by weight of a dispersible resin (acrylic resin, softening point 45°C). During mixing, a filler gas (air) was introduced at a rate of 1 ml / min and the stirring speed was set to 500 rpm to obtain a mixture. The mixture was spray-dried at a temperature of 40°C for 0.1 minutes to obtain reinforced resin particles.

[0064] Preparation of adhesive composition: Under conditions where the solvent was water, 75 parts by weight of an acrylic acid-modified aqueous epoxy resin (molecular weight 20,000 daltons, modifying groups being itaconic acid, acrylic acid, hydroxymethylacrylamide, and glycidyl methacrylate, and the initiator being dibenzoyl peroxide) was mixed with 15 parts by weight of an aqueous acrylic resin, 5 parts by weight of reinforcing resin particles, 1 part by weight of uncoated expandable microspheres (particle size 5-15 μm), 1 part by weight of a phenolic resin curing agent, 0.2 parts by weight of an organosiloxane leveling agent, and 0.2 parts by weight of an ethylene glycol butyl ether film-forming agent, and the mixture was stirred at 500 rpm to obtain an adhesive composition.

[0065] The adhesive composition was applied to a NdFeB magnetic substrate by brush coating and allowed to stand at 50° C. for 20 minutes to pre-cure, resulting in a magnet having an adhesive coating with a thickness of 100 μm.

[0066] A silicon steel core was assembled to the adhesive coating and heat cured at 200° C. to obtain a magnet assembly designated Sample 3.

[0067] Example 4 Preparation of reinforced resin particles: A light inorganic filler (fumed silica, specific surface area 150 m) was added under the condition that the solvent was ethanol. 2 / g, compressed density 0.05g / cm 3 One part by weight of the cellulose acetate copolymer was mixed with 4 parts by weight of a highly adhesive resin (β-hydroxyethyl acrylate resin, molecular weight 21,000 daltons) and 7 parts by weight of a dispersible resin (acrylic resin, softening point 45°C). During mixing, a filler gas (air) was introduced at a rate of 8 ml / min and the stirring speed was set to 100 rpm to obtain a mixture. The mixture was spray-dried at 60°C for 2 minutes to obtain reinforced resin particles.

[0068] Preparation of adhesive composition: Under conditions where the solvent was water, 70 parts by weight of an acrylic acid-modified aqueous epoxy resin (molecular weight 20,000 daltons, modifying groups being itaconic acid, acrylic acid, hydroxymethylacrylamide, and glycidyl methacrylate, and the initiator being dibenzoyl peroxide) was mixed with 20 parts by weight of an aqueous acrylic resin, 8 parts by weight of reinforcing resin particles, 3 parts by weight of uncoated expandable microspheres (particle size 5 to 20 μm), 1 part by weight of a phenolic resin curing agent, 0.5 parts by weight of an organosiloxane leveling agent, and 1 part by weight of an ethylene glycol butyl ether film-forming agent, and the mixture was stirred at 100 rpm to obtain an adhesive composition.

[0069] The adhesive composition was applied to a NdFeB magnetic substrate by dip coating and allowed to stand at 50° C. for 20 minutes to pre-cure, yielding a magnet having an adhesive coating with a thickness of 100 μm.

[0070] A silicon steel core was assembled to the adhesive coating and heat cured at 200° C. to obtain a magnet assembly designated Sample 4.

[0071] Example 5 Preparation of reinforced resin particles: A light inorganic filler (fumed silica, specific surface area 150 m) was added under the condition that the solvent was ethanol.2 / g, compressed density 0.05g / cm 3 One part by weight of the cellulose acetate copolymer was mixed with 3 parts by weight of a highly adhesive resin (β-hydroxyethyl acrylate resin, molecular weight 21,000 daltons) and 7 parts by weight of a dispersible resin (acrylic resin, softening point 45°C). During mixing, a filler gas (air) was introduced at a rate of 1 ml / min and the stirring speed was set to 500 rpm to obtain a mixture. The mixture was spray-dried at a temperature of 40°C for 0.1 minutes to obtain reinforced resin particles.

[0072] Preparation of coated expandable microspheres: One part by weight of uncoated expandable microspheres and aluminum polyphosphate (particle size 0.2-5 μm, compressed density 3.5 g / cm) were mixed in an ethanol solvent. 3 5 parts by weight of the acrylic resin (softening point: 40°C) were mixed with 0.5 parts by weight of the acrylic resin (softening point: 40°C) at a stirring speed of 500 rpm to obtain a mixture, which was then spray-dried at 60°C for 1 minute to obtain coated expandable microspheres.

[0073] Preparation of adhesive composition: 70 parts by weight of acrylic acid-modified aqueous epoxy resin (molecular weight 20,000 daltons, modifying groups selected from itaconic acid, acrylic acid, hydroxymethylacrylamide, and glycidyl methacrylate, and an initiating group selected from dibenzoyl peroxide) was mixed with 20 parts by weight of aqueous acrylic resin, 5 parts by weight of reinforcing resin particles, 10 parts by weight of coated expandable microspheres, 1 part by weight of phenolic resin curing agent, 0.2 part by weight of organosiloxane leveling agent, and 0.2 part by weight of ethylene glycol butyl ether film-forming agent in a water-based solvent at a stirring speed of 500 rpm to obtain an adhesive composition.

[0074] The adhesive composition was applied to a NdFeB magnetic substrate by brush coating and allowed to stand at 50° C. for 20 minutes to pre-cure, resulting in a magnet having an adhesive coating with a thickness of 120 μm.

[0075] A silicon steel core was assembled to the adhesive coating and heat cured at 200° C. to obtain a magnet assembly designated Sample 5.

[0076] Comparative Example 1 An adhesive composition was obtained by mixing 80 parts by weight of an acrylic acid-modified aqueous epoxy resin (molecular weight 20,000 daltons, modifying groups selected from itaconic acid, acrylic acid, hydroxymethylacrylamide, and glycidyl methacrylate, and an initiator selected from dibenzoyl peroxide) with 20 parts by weight of an aqueous acrylic resin, 1.7 parts by weight of uncoated expandable microspheres, 1 part by weight of a phenolic resin curing agent, 0.2 parts by weight of an organosiloxane leveling agent, and 0.2 parts by weight of an ethylene glycol butyl ether film-forming agent, using water as the solvent, and stirring at 500 rpm.

[0077] The adhesive composition was applied to a magnetic substrate (NdFeB magnet) by brush coating and allowed to stand at 50° C. for 20 minutes to pre-cure, resulting in an adhesive coating with a thickness of 100 μm.

[0078] A silicon steel core was assembled to the adhesive coating and heat cured at 200° C. to obtain a magnet assembly, designated Comparative Sample 1.

[0079] Comparative Example 2 The method was the same as in Example 1, except that no coating resin was added to the coated expandable microspheres.

[0080] The adhesive composition was applied to a magnetic substrate (NdFeB magnet) by brush coating and allowed to stand at 50° C. for 20 minutes to pre-cure, resulting in an adhesive coating with a thickness of 100 μm.

[0081] A silicon steel core was assembled to the adhesive coating and heat cured at 200° C. to obtain a magnet assembly, designated Comparative Sample 2.

[0082] Comparative Example 3 The method was the same as in Example 3, except that no fumed silica was added to the reinforcing resin particles.

[0083] The adhesive composition was applied to a NdFeB magnetic substrate by brush coating and allowed to stand at 50° C. for 20 minutes to pre-cure, resulting in a magnet having an adhesive coating with a thickness of 100 μm.

[0084] A silicon steel core was assembled to the adhesive coating and heat cured at 200° C. to obtain a magnet assembly, designated Comparative Sample 3.

[0085] Comparative Example 4 The method was the same as in Example 3, except that the β-hydroxyethyl acrylate resin in the reinforcing resin particles was changed to an acrylic resin.

[0086] The adhesive composition was applied to a NdFeB magnetic substrate by brush coating and allowed to stand at 50° C. for 20 minutes to pre-cure, resulting in a magnet having an adhesive coating with a thickness of 100 μm.

[0087] A silicon steel core was assembled to the adhesive coating and heat cured at 200° C. to obtain a magnet assembly, designated Comparative Sample 4.

[0088] Table 1 shows the treatment conditions and test results for the samples of Examples 1 to 5 and Comparative Examples 1 to 4.

[0089] TIFF2025536280000002.tif100170

[0090] According to the data in Table 1, by comparing the Examples and Comparative Examples, it was found that when the adhesive composition contained the expandable microspheres of the present invention, the coated resin, and the reinforcing resin particles, the expansion rate of the adhesive coating was basically able to maintain its original expansion force even after two months of storage, and the shear strength of the adhesive layer at room temperature and 160°C was better, with the shear strength at 160°C being particularly pronounced.

[0091] Although the preferred embodiments of the present invention have been described in detail above with reference to the drawings, the present invention is not limited to the specific contents of the above embodiments. Various simple modifications can be made to the technical means of the present invention within the scope of the technical idea of ​​the present invention, and all of these simple modifications fall within the scope of protection of the present invention.

[0092] It should be noted that each of the specific technical features described in the above specific embodiments can be combined in any suitable manner unless there is a contradiction, and in order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0093] Furthermore, various embodiments of the present invention can be arbitrarily combined, and as long as they are not contrary to the spirit of the present invention, they should also be considered as part of the disclosure of the present invention.

Claims

1. 1. A magnet with an adhesive coating, comprising: the magnet includes a magnetic substrate and an adhesive coating, the adhesive coating being applied to at least a portion of an outer surface of the magnetic substrate, the adhesive coating being obtained by applying an adhesive composition; The adhesive composition includes a base resin and an expanding agent, 1. A magnet with an adhesive coating, wherein the expansion agent is located in the adhesive coating near the magnetic substrate, and the distribution height of the expansion agent is 50% or less of the cross-sectional thickness of the adhesive coating.

2. 2. The magnet according to claim 1, wherein the adhesive coating has a thickness of 80 to 150 μm, a softening point of 60 to 80° C., and an expansion coefficient of 80% to 200%.

3. 2. The magnet according to claim 1, wherein the content of said expanding agent is 0.5 to 20 parts by weight per 100 parts by weight of said base resin.

4. the expansion agent is coated expandable microspheres, the coated expandable microspheres comprising uncoated expandable microspheres and a coating layer covering the outer surfaces of the uncoated expandable microspheres, the uncoated expandable microspheres comprising a polymer shell and an expandable matrix encapsulated in the polymer shell, and the coating layer comprising a coating resin and a heavy inorganic filler embedded in the coating resin; the uncoated expandable microspheres have a particle size of 3 to 30 μm; The coating resin is a thermoplastic resin having a softening point of 40 to 100°C, and is preferably at least one of acrylic resin, polysulfone resin, and melamine formaldehyde resin. The particle size of the heavy inorganic filler is 0.5 to 30 μm, and the compressed density is 3.1 to 7.8 g / cm. ３ 2. The magnet of claim 1 , wherein the heavy inorganic filler comprises at least one of carbonate, phosphate, polyphosphate, metal oxide, and non-metal compound, the carbonate is preferably at least one of calcium carbonate, magnesium carbonate, and zinc carbonate, the phosphate is preferably at least one of calcium phosphate and sodium phosphate, the polyphosphate is preferably at least one of calcium polyphosphate and aluminum polyphosphate, the metal oxide is preferably at least one of aluminum oxide, rare earth oxide, and triiron tetroxide, and the non-metal compound is preferably at least one of silicon dioxide, silicon nitride, and silicon carbide.

5. 5. The magnet according to claim 4, wherein the content of the coating resin is 0.1 to 1.8 parts by weight and the content of the heavy inorganic filler is 1 to 15 parts by weight, relative to 1 part by weight of the uncoated expandable microspheres.

6. the base resin comprises a thermosetting resin and a thermoplastic resin, and the weight ratio of the thermoplastic resin to the thermosetting resin is 1:1 to 10, preferably 1:2 to 8; the thermosetting resin is at least one of an epoxy resin, a hydroxyacrylic resin, and a polyurethane resin, the epoxy resin being any one of a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, and a bisphenol S type epoxy resin, and preferably the epoxy resin is an acrylic acid-modified epoxy resin; The magnet according to claim 1 , wherein the thermoplastic resin is at least one of an acrylic resin, a polysulfone resin, and a melamine formaldehyde resin.

7. The acrylic acid-modified group in the acrylic acid-modified epoxy resin includes acrylic acid carboxyl monomer, acrylic acid hydroxy monomer, and other monomers; the acrylic carboxyl monomer contains any one of an acrylic acid group, a methylene succinic acid group, and a methacrylic acid group; the acrylic hydroxy monomer contains either a glycidyl methacrylate group or a methyl methacrylate group; The magnet according to claim 6 , wherein the other monomer contains either a hydroxymethylacrylamide group or a styrene group.

8. The magnet according to any one of claims 1 to 7, wherein the adhesive composition further comprises reinforcing resin particles, the reinforcing resin particles comprising a light inorganic filler, a highly adhesive resin and a dispersible resin adhered to the light inorganic filler, and a filler gas enclosed in the highly adhesive resin and the dispersible resin.

9. The magnet according to claim 8, wherein the light inorganic filler is at least one of fumed silica and fumed alumina, the high-adhesion resin is at least one of β-hydroxyethyl acrylate resin, hydantoin epoxy resin, and tripolyphosphazene epoxy resin, the dispersing resin is a thermoplastic resin having a softening point of 40 to 100°C, preferably at least one of acrylic resin, methacrylic resin, polysulfone resin, melamine formaldehyde resin, and polyolefin resin, and the filler gas is at least one of air, nitrogen, carbon dioxide, hydrogen, and helium.

10. The magnet according to claim 8, wherein the particle size of the reinforcing resin particles is 0.5 to 30 μm, the content of the high adhesive resin is 1 to 8 parts by weight, and the content of the dispersible resin is 1 to 10 parts by weight, relative to 1 part by weight of the light inorganic filler.

11. The specific surface area of ​​the light inorganic filler is 150 to 400 m ２ / g, and the compressed density is 0.02 to 0.20 g / cm ３ 9. The magnet according to claim 8, wherein the molecular weight of the β-hydroxyethyl acrylate resin is 5,000 to 50,000 daltons, preferably 10,000 to 21,000 daltons.

12. 9. The magnet according to claim 8, wherein the content of said reinforcing resin particles is 1 to 15 parts by weight per 100 parts by weight of said base resin.

13. 2. The magnet according to claim 1, wherein the adhesive coating is obtained by pre-curing an adhesive composition after application, and the pre-curing temperature is 40 to 90°C.

14. 1. A magnet assembly comprising: The magnet assembly includes a magnet and a core, and has an adhesive layer between the magnet and the core obtained by thermally curing an adhesive coating at 150 to 200°C; A magnet assembly, characterized in that the adhesive layer obtained by heat curing has expanded bubbles near the magnetic substrate, and the height of the distribution of the expanded bubbles is 80% or less of the cross-sectional thickness of the adhesive layer obtained by heat curing.

15. An electric device, characterized in that the electric device includes a magnet assembly according to claim 14.

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