High-temperature-resistant adhesive for motor iron core punching sheet and preparation method of high-temperature-resistant adhesive

Abstract

The invention discloses a high-temperature-resistant adhesive for a motor iron core punching sheet and a preparation method of the high-temperature-resistant adhesive, and the high-temperature-resistant adhesive comprises the following components in parts by mass: 60-80 parts of solid polyfunctional novolac epoxy resin; 5 to 15 parts of polyurethane modified epoxy resin; 5 to 15 parts of solid bisphenol A epoxy resin; 5-20 parts of a heat-resistant thermoplastic resin; 1 to 4 parts of a silane coupling agent; 2-8 parts of a filler; 4-10 parts of a curing agent; 0.05 to 0.2 part of an accelerant; the solvent is used for dissolving and mixing the components; according to the high-temperature-resistant adhesive for the motor iron core punching sheet, an organic-inorganic toughening mode is combined, three kinds of organic resin including polyurethane modified epoxy resin, solid bisphenol A type epoxy resin and heat-resistant thermoplastic resin are adopted, and an inorganic filler is used in a matched mode, so that the solid polyfunctional epoxy resin is subjected to toughening modification. According to the technical scheme, the problem that high toughness and high temperature resistance are difficult to consider under the condition that an existing motor iron core punching sheet adopts a modified epoxy adhesive to improve the toughness and peel strength of the adhesive is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of high temperature resistant epoxy adhesives, but is not limited thereto, and in particular to a high temperature resistant adhesive for motor core punching sheets and a preparation method thereof. Background Art

[0002] At present, the motor core is made of silicon steel sheets, which are stacked during core manufacturing. In order to avoid the increase of eddy current loss caused by short circuit between the core punching sheets, the surface of the punching sheets needs to be insulated, usually by coating the surface with high-impedance insulating materials. The coating material should not only have good adhesion, insulation, corrosion resistance, oil resistance and heat resistance, but also have good processing properties.

[0003] The insulating materials coated on the surface of the punching sheets are divided into two categories: insulating paint and insulating adhesive. The punching sheets coated with insulating paint do not have self-adhesive properties and need to be fastened and assembled into an iron core by welding, riveting, bolting, etc., and the above fastening methods are all local point fixation of the iron core, the connection force is not high, and it will also damage the insulating coating; while the insulating adhesive is a self-adhesive coating, which can bond the stacked punching sheets to each other. This method does not damage the insulating coating, the bonding between the punching sheets is reliable, and it has more development prospects.

[0004] Existing insulating adhesives for motor core punching sheets mainly include modified phenolic, modified bismaleimide and modified epoxy adhesives. Existing modified epoxy adhesives for motor core punching sheets use toughening methods to improve the toughness and peel strength of the adhesive, but its heat resistance is lower than 180°C. Although there are modified epoxy adhesive products with a temperature resistance of more than 180°C, their toughness is poor or the processability does not meet the requirements for bonding motor core punching sheets. Summary of the invention

[0005] Purpose of the present invention: In order to solve the above-mentioned technical problems, the embodiments of the present invention provide a high temperature resistant adhesive for motor core punching sheets and a preparation method thereof, so as to solve the problem that it is difficult to achieve both high toughness and high temperature resistance when the existing motor core punching sheets use modified epoxy adhesives to improve the toughness and peel strength of the adhesive.

[0006] Technical solution of the present invention: In a first aspect, an embodiment of the present invention provides a high temperature resistant adhesive for motor core punching sheets, wherein the components of the high temperature resistant adhesive for motor core punching sheets include:

[0007] 60-80 parts of solid multifunctional phenolic epoxy resin;

[0008] 5 to 15 parts of polyurethane modified epoxy resin;

[0009] 5 to 15 parts of solid bisphenol A epoxy resin;

[0010] 5 to 20 parts of heat-resistant thermoplastic resin;

[0011] 1 to 4 parts of silane coupling agent;

[0012] 2 to 8 parts of filler;

[0013] 4 to 10 parts of curing agent;

[0014] 0.05-0.2 parts of accelerator;

[0015] and a solvent for dissolving and mixing the above components;

[0016] Among them, the high temperature resistant adhesive for motor core punching sheets adopts three organic resins, namely polyurethane modified epoxy resin, solid bisphenol A epoxy resin, and heat-resistant thermoplastic resin, by combining organic-inorganic toughening methods, and uses an inorganic filler in combination to toughen and modify the solid multifunctional epoxy resin.

[0017] Optionally, in the high temperature resistant adhesive for motor core punching sheets as described above, the solid multifunctional epoxy resin includes at least one of the following: phenol novolac epoxy resin, o-cresol novolac epoxy resin, epoxy resorcinol formaldehyde resin, bisphenol A novolac epoxy resin;

[0018] The epoxy value of the solid multifunctional epoxy resin ranges from 0.50 to 0.60.

[0019] Optionally, in the high temperature resistant adhesive for motor core punching sheets as described above, the polyurethane modified epoxy resin is obtained by chemically grafting a tough polyurethane to an epoxy resin molecular chain, and the grafted epoxy resin contains a urethane flexible soft segment, which is used to improve the brittleness of the multifunctional resin;

[0020] The epoxy value of the polyurethane modified epoxy resin ranges from 0.30 to 0.45.

[0021] Optionally, in the high temperature resistant adhesive for motor core punching sheets as described above,

[0022] The solid bisphenol A epoxy resin has a flexible long chain segment, which is used to improve the brittleness of the multifunctional resin and the film-forming property of the adhesive after surface drying;

[0023] The epoxy value of the solid bisphenol A epoxy resin ranges from 0.03 to 0.17.

[0024] Optionally, in the high temperature resistant adhesive for motor core punching sheets as described above,

[0025] The heat-resistant thermoplastic resin is a hydroxyl-terminated polyethersulfone resin, the glass transition temperature of which is not less than 200° C., and is used to improve the brittleness of the multifunctional resin and the film-forming property of the adhesive after surface drying.

[0026] Optionally, in the high temperature resistant adhesive for motor core punching sheets as described above,

[0027] The silane coupling agent comprises: an organic functional group and a silane alkoxy group; wherein the organic functional group has compatibility or reactivity with organic matter, and the silane alkoxy group has the property of reacting with a metal interface;

[0028] After the silane coupling agent is hydrolyzed, a bond is formed between the adhesive interface and the metal interface to promote interface fusion, thereby improving the adhesion of the adhesive on the metal interface.

[0029] Optionally, in the high temperature resistant adhesive for motor core punching sheets as described above,

[0030] The filler is a nanometer-level inorganic powder, and the filler includes at least one of mica powder and white carbon black, and is used to achieve a synergistic strengthening and toughening effect on the high-temperature resistant adhesive.

[0031] Optionally, in the high temperature resistant adhesive for motor core punching sheets as described above, the curing agent is a heat-activated latent curing agent, and a dicyandiamide curing agent is selected; the curing agent is cured and cross-linked with the epoxy resin under heating conditions;

[0032] The accelerator is selected from at least one of the following: imidazole derivatives, substituted urea, and is used to increase the reaction rate;

[0033] The solvent is selected from at least one of the following organic solvents: acetone, N-methylpyrrolidone, dimethylformamide, dimethylacetamide; after the solvent is added, the solid content of the adhesive reaches 30% to 50%, which is convenient for construction operation and has an important influence on the processability of the adhesive.

[0034] In a second aspect, an embodiment of the present invention further provides a method for preparing a high temperature resistant adhesive for a motor core punching sheet, which is used to prepare a high temperature resistant adhesive for a motor core punching sheet as described in any one of the above items, and the preparation method comprises:

[0035] Step 1, crushing solid multifunctional epoxy resin and solid bisphenol A epoxy resin and putting them into a reaction kettle;

[0036] Step 2, heating the reactor to 110° C. and keeping the temperature for 30 to 60 minutes until the solid inside is completely softened;

[0037] Step 3, adding solvent to the reaction kettle and stirring for 30 to 60 minutes until the resin is completely dissolved to a uniform state;

[0038] Step 4, adding a heat-resistant thermoplastic resin into the reaction kettle and stirring for 30 to 60 minutes until the resin is completely dissolved into a uniform state;

[0039] Step 5, after the reaction kettle is cooled to 80°C, add the polyurethane modified epoxy resin and continue stirring for 30min to 60min until all components are evenly mixed;

[0040] Step 6, adding fillers to the reactor and stirring for 2 h to 4 h until the added fillers are evenly dispersed;

[0041] Step 7: After the reaction kettle is cooled to 20° C. to 30° C., add the silane coupling agent, curing agent and accelerator, and stir for 1 h to 2 h until the components are evenly mixed.

[0042] Optionally, in the method for preparing the high temperature resistant adhesive for motor core punching sheets as described above, the preparation method of the polyurethane modified epoxy resin added in step 5 comprises:

[0043] Step 51, evacuate the liquid bisphenol A epoxy resin and polypropylene glycol (PPG) at 110° C. to 130° C. for 2 h to 4 h, cool to room temperature and store in a desiccator; wherein the epoxide value of the liquid bisphenol A epoxy resin is 0.50 to 0.60;

[0044] Step 52, weighing an appropriate amount of 4,4'-diphenylmethane diisocyanate (MDI) and pretreated PPG (n(-NCO) / n(-OH)=2:1) ​​and adding them to a reaction kettle, stirring and heating to 40°C to 60°C, stirring for 20min to 30min under the protection of inert gas, heating to (80±5)°C, and continuing to keep warm and stir for 1h to 2h to obtain a terminal isocyanate polyurethane prepolymer;

[0045] Step 53, weighing an appropriate amount of terminal isocyanate polyurethane prepolymer and pretreated liquid bisphenol A epoxy resin, adding them into a reaction kettle, stirring and heating to 80° C. to 100° C., reacting for 2 h to 4 h under the protection of inert gas, to obtain the polyurethane modified epoxy resin required for the preparation of the adhesive; wherein the mass ratio of the liquid bisphenol A epoxy resin is 20:100;

[0046] The pretreatment method of the filler added in step 6 includes:

[0047] Step 61, weigh an appropriate amount of filler and put it into an electric oven, heat it to 100° C. and dry it for 1 h to 2 h, cool it to room temperature and store it in a desiccator;

[0048] Step 62, pour the dried filler into a high-speed mixer, add a silane coupling agent solution with a mass fraction of 20% after atomization under stirring at a speed of (1500-2000) r / min, stir for 30-60 minutes and then take it out; wherein the ratio of the silane coupling agent solution is isopropanol: xylene = 1:1;

[0049] Step 63, drying the treated filler at 110° C. to 120° C. for 2 h to 4 h, cooling to room temperature and storing in a desiccator for later use.

[0050] Beneficial effects of the present invention: The embodiment of the present invention provides a high-temperature resistant adhesive for motor core punching sheets and a preparation method thereof. By combining organic-inorganic toughening methods, three tough organic resins (including polyurethane-modified epoxy resin, solid bisphenol A epoxy resin and heat-resistant thermoplastic resin (such as terminal hydroxyl polyether sulfone resin)) and an inorganic filler are used to toughen and modify solid multifunctional epoxy resin to prepare a high-toughness, high-temperature resistant adhesive for motor core punching sheets, which is expected to be used in the manufacture of motor cores in the fields of aerospace and new energy vehicles. The technical solution provided by the embodiment of the present invention has the following beneficial effects:

[0051] 1. The embodiment of the present invention is directed to a solid multifunctional epoxy resin with a high degree of crosslinking and high brittleness after curing. The flexible soft segments of urethane grafted on the polyurethane-modified epoxy resin, the flexible long segments in the solid bisphenol A epoxy resin, the good toughness of the terminal hydroxyl polyether sulfone resin, and the synergistic strengthening and toughening properties of inorganic nanoparticles are used to toughen and modify the epoxy resin. A heat-activated latent curing agent is used to develop an adhesive for motor core punching sheets that has the characteristics of high temperature resistance and high toughness.

[0052] 2. The softening points of the solid multifunctional epoxy resin, solid bisphenol A epoxy resin and terminal hydroxyl polyether sulfone resin used in the high temperature resistant adhesive prepared by the present invention are all higher than 60°C, the film-forming property of the adhesive layer after drying is good, the epoxy resin has a strong bonding force with the metal interface so that the adhesive layer has good adhesion, the terminal hydroxyl polyether sulfone resin makes the adhesive layer have good flexibility, the adhesive has good processability, and is easy to construct and transport;

[0053] 3. The room temperature peel strength of the high temperature resistant adhesive prepared by the present invention is not less than 1.6N / mm, the room temperature tensile shear strength is not less than 23MPa, and the 200°C tensile shear strength is not less than 15.5MPa. After being immersed in 4050 aviation lubricating oil at 180°C for 96 hours, the room temperature tensile shear strength is not less than 20MPa, and the strength retention rate can reach 90%. It has good toughness, bonding strength, heat resistance and oil resistance. DETAILED DESCRIPTION

[0054] To make the purpose, technical solution and advantages of the present invention more clear, the embodiments of the present invention will be described in detail below. It should be noted that the embodiments and features in the embodiments of the present application can be combined with each other arbitrarily without conflict.

[0055] As described in the above background technology, insulating adhesives are self-adhesive coatings and have a bright future in the manufacture of motor cores.

[0056] The existing insulating adhesives for motor core punching sheets are mainly of the following types: modified phenolic adhesives, modified bismaleimide adhesives and modified epoxy adhesives. The following are the descriptions of the above types of insulating adhesives:

[0057] (1) Modified phenolic insulation adhesives are based on phenolic resin (PF), which are generally modified with silicone to improve their heat resistance, or modified with nitrile or acetal to improve their toughness. Among them, phenolic-acetal insulation adhesives have low cost and good durability, but their curing reaction is a polycondensation reaction, which will precipitate more volatiles, resulting in loose adhesive layers, and the use temperature is limited to 80℃~120℃; phenolic-nitrile insulation adhesives have poor low-temperature toughness and poor fluidity, and the long-term use temperature can reach 150℃; phenolic-acetal-organic silicone adhesives can be used at a temperature of up to 200℃ for a long time, but their toughness is poor.

[0058] (2) Modified bismaleimide insulation adhesive is based on bismaleimide resin (BMI), which is generally modified with allyl compounds, polysulfone, cyanate to improve its toughness, or modified with epoxy to improve its adhesion. The long-term use temperature of modified bismaleimide insulation adhesive can reach 204°C and the short-term use temperature can reach 232°C. It has excellent electrical properties, but poor toughness and film-forming properties.

[0059] (3) Modified epoxy insulating adhesive is based on epoxy resin (EP), which is generally modified with acetal, polyamide, polysulfone to improve adhesion and toughness, or modified with phenolic to improve heat resistance. Modified epoxy adhesive is a major type of adhesive for motor core punching. A lot of research has been conducted at home and abroad on adhesives for motor core punching. Typical adhesives for core punching include: 1175, the T-peel strength of the adhesive is greater than 1N / mm, the shear strength is greater than 5MPa, and the heat resistance grade is 180℃. For example, Chinese patent CN100506929C discloses a water-based self-adhesive coating for electrical steel, the main components of which are water-based epoxy resin emulsion and curing agent, etc., and the coating has good toughness after curing, but the heat resistance level does not exceed 180°C; for another example, Chinese patent CN105131750 discloses an environmentally friendly self-adhesive coating for electrical steel, the main components of which are water-soluble acrylic resin, water-based epoxy resin and dicyandiamide, etc., and the coating has good toughness but poor heat resistance (≤180°C); for another example, Sanyou (Tianjin) Polymer Technology Co., Ltd. has developed a high peel strength structural adhesive with the brand name SY-248, the main components of which are R139 epoxy resin, nitrile-modified epoxy resin, polyurethane-modified epoxy resin and dicyandiamide, etc., and the T-peel strength is not less than 6.0N / mm, but the heat resistance is poor, and the tensile shear strength at 150°C is only 6.2MPa.

[0060] However, the existing modified epoxy adhesive for motor core punching sheets adopts a toughening method to improve the toughness and peel strength of the adhesive, but its heat resistance is lower than 180°C. Although there are modified epoxy adhesive products with a temperature resistance of more than 180°C, their toughness is poor or the processability does not meet the requirements for bonding motor core punching sheets.

[0061] When the motor is working normally, the working environment of the core assembly is complex and it is subjected to various stresses, mainly mechanical stress (vibration, impact, etc.), electromagnetic stress, thermal stress, etc. In order to avoid the core being subjected to complex stresses during operation and resulting in bonding failures such as punching and loosening of sheets, higher requirements are placed on the comprehensive performance of the insulating adhesive, and an insulating adhesive with good toughness, good adhesion and high temperature resistance is required.

[0062] In order to solve the above problems and based on the requirements for the performance of high-temperature resistant insulating adhesives used in motor core assemblies, an embodiment of the present invention provides a high-temperature resistant adhesive for motor core punching sheets and a preparation method thereof. The present invention aims to develop an epoxy adhesive that is resistant to high temperatures and has high peel strength and shear strength, which has high toughness and bonding strength while achieving good heat resistance.

[0063] The present invention provides the following specific embodiments which can be combined with each other. The same or similar concepts or processes may not be described in detail in some embodiments.

[0064] The embodiment of the present invention provides a high temperature resistant adhesive for motor core punching sheets, the adhesive has high toughness and high temperature resistance, and the high temperature resistant adhesive comprises, by mass:

[0065] 100 parts by mass of epoxy resin;

[0066] 100-110 parts by mass of a curing agent;

[0067] 0.6-0.8 mass parts of accelerator;

[0068] 400-5508 parts by mass of thermally conductive filler;

[0069] 15 to 308 parts by mass of a toughening agent;

[0070] And a solvent for dissolving and mixing the above components.

[0071] The high temperature resistant adhesive for motor core punching sheets provided in an embodiment of the present invention adopts three organic resins, namely polyurethane modified epoxy resin, solid bisphenol A type epoxy resin, and heat-resistant thermoplastic resin, by combining organic-inorganic toughening methods, and uses an inorganic filler in combination to toughen and modify the solid multifunctional epoxy resin.

[0072] In one implementation of the embodiment of the present invention, the solid multifunctional epoxy resin includes at least one of the following: phenol novolac epoxy resin, o-cresol novolac epoxy resin, epoxy resorcinol formaldehyde resin, bisphenol A novolac epoxy resin, etc.

[0073] In this implementation, it is recommended to select an epoxy value range of 0.50 to 0.60. Compared with bisphenol A epoxy resin, solid multifunctional epoxy resin has high functionality, and its epoxy value range is 0.50 to 0.60, which can provide more cross-linking points and easily form a highly cross-linked three-dimensional structure. It has excellent heat resistance and mechanical strength, electrical insulation and corrosion resistance, but it is brittle after curing, and the toughness can be improved by toughening modification.

[0074] In one implementation of the embodiment of the present invention, the polyurethane modified epoxy resin is recommended to have an epoxy value range of 0.30 to 0.45. In this implementation, the polyurethane modified epoxy resin is obtained by chemically grafting a tough polyurethane to an epoxy resin molecular chain, and the grafted epoxy resin contains a urethane flexible soft segment, which is used to improve the brittleness of the multifunctional resin.

[0075] In one implementation of the present invention, the recommended epoxy value range of the solid bisphenol A epoxy resin is 0.03 to 0.17. In this implementation, the solid bisphenol A epoxy resin has a flexible long chain segment, which is used to improve the brittleness of the multifunctional resin and the film-forming property of the adhesive after surface drying.

[0076] In one implementation of the present invention, the heat-resistant thermoplastic resin is a hydroxy-terminated polyethersulfone resin having a glass transition temperature of not less than 200° C., and is used to improve the brittleness of the multifunctional resin and the film-forming property of the adhesive after surface drying.

[0077] In one implementation of the embodiment of the present invention, the silane coupling agent includes: an organic functional group and a silaneoxy group; wherein the organic functional group has compatibility or reactivity with organic matter, and the silaneoxy group has the property of reacting with a metal interface.

[0078] In this implementation, after the silane coupling agent is hydrolyzed, a bond is formed between the adhesive interface and the metal interface to promote interface fusion, thereby improving the adhesion of the adhesive on the metal interface.

[0079] In one implementation of the embodiment of the present invention, the filler is a nano-scale inorganic powder, and the recommended filler includes at least one of mica powder and white carbon black, which is used to achieve synergistic reinforcement and toughening effects on the high temperature resistant adhesive.

[0080] In one implementation of an embodiment of the present invention, the curing agent is a heat-activated latent curing agent, and a dicyandiamide curing agent is recommended; this type of curing agent cures and cross-links with the epoxy resin under heating conditions to form a highly cross-linked three-dimensional structure, so that the adhesive has high strength and high temperature resistance.

[0081] In one implementation of the embodiment of the present invention, the accelerator is selected from at least one of the following: an imidazole derivative, a substituted urea, and is used to increase the reaction rate;

[0082] In one implementation of the embodiment of the present invention, the solvent is selected from at least one of the following organic solvents: acetone, N-methylpyrrolidone, dimethylformamide, dimethylacetamide; the selected solvent has good solubility for each component of the adhesive, so that the high temperature resistant adhesive is mixed evenly, the viscosity is reduced, the fluidity is improved, and good construction processability is obtained. In a specific implementation, after the solvent is added, the solid content of the adhesive reaches 30% to 50%, which is convenient for construction operation and has an important influence on the processability of the adhesive.

[0083] Based on the high temperature resistant adhesive for motor core punching sheets provided by the above embodiments of the present invention, the embodiments of the present invention further provide a method for preparing the high temperature resistant adhesive for motor core punching sheets, the preparation method is used to prepare the high temperature resistant adhesive for motor core punching sheets provided by any of the above embodiments, the preparation method comprising:

[0084] Step 1, crushing solid multifunctional epoxy resin and solid bisphenol A epoxy resin and putting them into a reaction kettle;

[0085] Step 2, heating the reactor to 110° C. and keeping the temperature for 30 to 60 minutes until the solid inside is completely softened;

[0086] Step 3, adding solvent to the reaction kettle and stirring for 30 to 60 minutes until the resin is completely dissolved to a uniform state;

[0087] Step 4, adding a heat-resistant thermoplastic resin into the reaction kettle and stirring for 30 to 60 minutes until the resin is completely dissolved into a uniform state;

[0088] Step 5, after the reaction kettle is cooled to 80°C, add the polyurethane modified epoxy resin and continue stirring for 30min to 60min until all components are evenly mixed;

[0089] Step 6, adding fillers to the reactor and stirring for 2 h to 4 h until the added fillers are evenly dispersed;

[0090] Step 7: After the reaction kettle is cooled to 20° C. to 30° C., add the silane coupling agent, curing agent and accelerator, and stir for 1 h to 2 h until the components are evenly mixed.

[0091] In one implementation of the embodiment of the present invention, the preparation method of the polyurethane-modified epoxy resin added in the above step 5 includes:

[0092] Step 51, evacuate the liquid bisphenol A epoxy resin and polypropylene glycol (PPG) at 110° C. to 130° C. for 2 h to 4 h, cool to room temperature and store in a desiccator; wherein the epoxide value of the liquid bisphenol A epoxy resin is 0.50 to 0.60;

[0093] Step 52, weighing an appropriate amount of 4,4'-diphenylmethane diisocyanate (MDI) and pretreated PPG (n(-NCO) / n(-OH)=2:1) ​​and adding them to a reaction kettle, stirring and heating to 40°C to 60°C, stirring for 20min to 30min under the protection of inert gas, heating to (80±5)°C, and continuing to keep warm and stir for 1h to 2h to obtain a terminal isocyanate polyurethane prepolymer;

[0094] Step 53, weighing an appropriate amount of terminal isocyanate polyurethane prepolymer and pretreated liquid bisphenol A epoxy resin, adding them into a reaction kettle, stirring and heating to 80°C to 100°C, reacting for 2h to 4h under the protection of inert gas, to obtain the polyurethane modified epoxy resin required for the preparation of the adhesive; wherein the mass ratio of the liquid bisphenol A epoxy resin is 20:100.

[0095] In one implementation of the embodiment of the present invention, the pretreatment method of the filler added in step 6 above includes:

[0096] Step 61, weigh an appropriate amount of filler and put it into an electric oven, heat it to 100° C. and dry it for 1 h to 2 h, cool it to room temperature and store it in a desiccator;

[0097] Step 62, pour the dried filler into a high-speed mixer, add a silane coupling agent solution with a mass fraction of 20% after atomization under stirring at a speed of (1500-2000) r / min, stir for 30-60 minutes and then take it out; wherein the ratio of the silane coupling agent solution is isopropanol: xylene = 1:1;

[0098] Step 63, drying the treated filler at 110° C. to 120° C. for 2 h to 4 h, cooling to room temperature and storing in a desiccator for later use.

[0099] The high temperature resistant adhesive for motor core punching sheets provided by the embodiment of the present invention and the preparation method thereof, by combining organic-inorganic toughening methods, uses three tough organic resins (including polyurethane modified epoxy resin, solid bisphenol A epoxy resin and heat-resistant thermoplastic resin (for example, terminal hydroxyl polyether sulfone resin)) and an inorganic filler to toughen and modify the solid multifunctional epoxy resin to prepare a high-toughness, high-temperature resistant adhesive for motor core punching sheets, which is expected to be applied in the manufacture of motor cores in the fields of aerospace and new energy vehicles. The technical solution provided by the embodiment of the present invention has the following beneficial effects:

[0100] 1. The embodiment of the present invention is directed to a solid multifunctional epoxy resin with a high degree of crosslinking and high brittleness after curing. The flexible soft segments of urethane grafted on the polyurethane-modified epoxy resin, the flexible long segments in the solid bisphenol A epoxy resin, the good toughness of the terminal hydroxyl polyether sulfone resin, and the synergistic strengthening and toughening properties of inorganic nanoparticles are used to toughen and modify the epoxy resin. A heat-activated latent curing agent is used to develop an adhesive for motor core punching sheets that has the characteristics of high temperature resistance and high toughness.

[0101] 2. The softening points of the solid multifunctional epoxy resin, solid bisphenol A epoxy resin and terminal hydroxyl polyether sulfone resin used in the high temperature resistant adhesive prepared by the present invention are all higher than 60°C, the film-forming property of the adhesive layer after drying is good, the epoxy resin has a strong bonding force with the metal interface so that the adhesive layer has good adhesion, the terminal hydroxyl polyether sulfone resin makes the adhesive layer have good flexibility, the adhesive has good processability, and is easy to construct and transport;

[0102] 3. The room temperature peel strength of the high temperature resistant adhesive prepared by the present invention is not less than 1.6N / mm, the room temperature tensile shear strength is not less than 23MPa, and the 200°C tensile shear strength is not less than 15.5MPa. After being immersed in 4050 aviation lubricating oil at 180°C for 96 hours, the room temperature tensile shear strength is not less than 20MPa, and the strength retention rate can reach 90%. It has good toughness, bonding strength, heat resistance and oil resistance.

[0103] The following is a schematic illustration of the implementation of the method for preparing the high temperature resistant adhesive for motor core punching sheets provided by the embodiment of the present invention through some specific implementation examples.

[0104] Implementation Example 1:

[0105] This implementation example 1 provides a high temperature resistant adhesive for motor core punching sheets, specifically a high toughness, high temperature resistant epoxy adhesive.

[0106] The components of the high temperature resistant adhesive in Example 1 are prepared by weight from 70 parts of bisphenol A novolac epoxy resin, 15 parts of polyurethane modified epoxy resin, 5 parts of E12 epoxy resin, 15 parts of terminal hydroxyl polyether sulfone resin, 2 parts of white carbon black, 4 parts of dicyandiamide, 0.1 parts of 2-methylimidazole, 1.5 parts of KH-560 silane coupling agent and 100 parts of a mixed solvent.

[0107] Implementation Example 2:

[0108] This implementation example 2 provides a high temperature resistant adhesive for motor core punching sheets, specifically a high toughness, high temperature resistant epoxy adhesive.

[0109] The components of the high temperature resistant adhesive in Example 2 are made of 70 parts of bisphenol A novolac epoxy resin, 15 parts of polyurethane modified epoxy resin, 5 parts of E12 epoxy resin, 15 parts of terminal hydroxyl polyether sulfone resin, 5 parts of white carbon black, 4 parts of dicyandiamide, 0.1 parts of 2-methylimidazole, 1.5 parts of KH-560 silane coupling agent and 100 parts of mixed solvent in parts by mass.

[0110] As shown in Table 1 below, the mass fractions and properties of the adhesives used for domestic core punching sheets and the adhesives of the comparative examples and implementation examples of the present invention are shown.

[0111] Table 1 Comparison of mass fractions and properties of various adhesives

[0112]

[0113] The specific conditions of the existing adhesive for core punching sheets and the adhesive for comparative examples and implementation examples of the present invention are shown in Table 1. As can be seen from Table 1, Comparative Example 1 only uses polyurethane modified epoxy resin for toughening, and the T-peel strength is low; Comparative Example 2 uses polyurethane modified epoxy resin and E12 epoxy resin for toughening, and the T-peel strength is slightly improved; Comparative Example 3 uses polyurethane modified epoxy resin, E12 epoxy resin and terminal hydroxyl polyether sulfone resin for toughening, and the peel strength is increased to 1.24N / mm, but the tensile shear strength at 200℃ is less than 10MPa, and then white carbon black is used for synergistic strengthening and toughening. After adding nano inorganic particles to Implementation Examples 1 and Implementation Examples 2, the toughness is increased to 1.66N / mm~2.0N / mm, and the tensile shear strength at 200℃ is greater than 15MPa, and the tensile shear strength at room temperature after oil resistance is greater than 20MPa. Compared with room temperature, the strength retention rate is greater than 89% (Implementation Example 2 can reach 97%).

[0114] The toughness, bonding strength and heat resistance of the insulating adhesive prepared in the embodiment of the present invention are better than those of the adhesive 1175; In addition, the experimental study found that, compared with the two existing adhesives in Table 1, the film-forming property, processability and toughness of the insulating adhesive developed by the present invention after surface drying are better than those of bismaleimide adhesives, and the toughness and bonding strength are better than those of phenolic-acetal-silicone adhesives.

[0115] In summary, considering toughness, bonding strength and heat resistance, the insulating adhesive developed by the present invention has better performance and has broad market application value.

[0116] Although the embodiments disclosed in the present invention are as above, the contents are only embodiments adopted to facilitate understanding of the present invention and are not intended to limit the present invention. Any technician in the field to which the present invention belongs can make any modifications and changes in the form and details of implementation without departing from the spirit and scope disclosed in the present invention, but the patent protection scope of the present invention shall still be subject to the scope defined in the attached claims.

Claims

1. A high temperature resistant adhesive for motor core punching, characterized in that: The components of the high temperature resistant adhesive for motor core punching sheets include, by mass: 60-80 parts of solid multifunctional phenolic epoxy resin; 5 to 15 parts of polyurethane modified epoxy resin; 5 to 15 parts of solid bisphenol A epoxy resin; 5 to 20 parts of heat-resistant thermoplastic resin; 1 to 4 parts of silane coupling agent; 2 to 8 parts of filler; 4 to 10 parts of curing agent; 0.05-0.2 parts of accelerator; and a solvent for dissolving and mixing the above components; Among them, the high temperature resistant adhesive for motor core punching sheets adopts three organic resins, namely polyurethane modified epoxy resin, solid bisphenol A epoxy resin, and heat-resistant thermoplastic resin, by combining organic-inorganic toughening methods, and uses an inorganic filler in combination to toughen and modify the solid multifunctional epoxy resin.

2. The high temperature resistant adhesive for motor core punching sheets according to claim 1, characterized in that: The solid multifunctional epoxy resin includes at least one of the following: phenol novolac epoxy resin, o-cresol novolac epoxy resin, epoxy resorcinol formaldehyde resin, bisphenol A novolac epoxy resin; The epoxy value of the solid multifunctional epoxy resin ranges from 0.50 to 0.

60.

3. The high temperature resistant adhesive for motor core punching sheets according to claim 1, characterized in that: The polyurethane modified epoxy resin is obtained by chemically grafting a tough polyurethane to the epoxy resin molecular chain. The grafted epoxy resin contains a urethane flexible soft segment, which is used to improve the brittleness of the multifunctional resin. The epoxy value of the polyurethane modified epoxy resin ranges from 0.30 to 0.

45.

4. The high temperature resistant adhesive for motor core punching sheets according to claim 1, characterized in that: The solid bisphenol A epoxy resin has a flexible long chain segment, which is used to improve the brittleness of the multifunctional resin and the film-forming property of the adhesive after surface drying; The epoxy value of the solid bisphenol A epoxy resin ranges from 0.03 to 0.

17.

5. The high temperature resistant adhesive for motor core punching sheets according to claim 1, characterized in that: The heat-resistant thermoplastic resin is a hydroxyl-terminated polyethersulfone resin, the glass transition temperature of which is not less than 200° C., and is used to improve the brittleness of the multifunctional resin and the film-forming property of the adhesive after surface drying.

6. The high temperature resistant adhesive for motor core punching sheets according to claim 1, characterized in that: The silane coupling agent comprises: an organic functional group and a silane alkoxy group; wherein the organic functional group has compatibility or reactivity with organic matter, and the silane alkoxy group has the property of reacting with a metal interface; After the silane coupling agent is hydrolyzed, a bond is formed between the adhesive interface and the metal interface to promote interface fusion, thereby improving the adhesion of the adhesive on the metal interface.

7. The high temperature resistant adhesive for motor core punching sheets according to claim 1, characterized in that: The filler is a nanometer-level inorganic powder, and the filler includes at least one of mica powder and white carbon black, and is used to achieve a synergistic strengthening and toughening effect on the high-temperature resistant adhesive.

8. The high temperature resistant adhesive for motor core punching sheets according to claim 1, characterized in that: The curing agent is a heat-activated latent curing agent, and a dicyandiamide curing agent is selected; the curing agent is cured and cross-linked with the epoxy resin under heating conditions; The accelerator is selected from at least one of the following: imidazole derivatives, substituted urea, and is used to increase the reaction rate; The solvent is selected from at least one of the following organic solvents: acetone, N-methylpyrrolidone, dimethylformamide, dimethylacetamide; after the solvent is added, the solid content of the adhesive reaches 30% to 50%, which is convenient for construction operation and has an important influence on the processability of the adhesive.

9. A method for preparing a high temperature resistant adhesive for motor core punching sheets, characterized in that: Used for preparing a high temperature resistant adhesive for motor core punching sheets according to any one of claims 1 to 8, the preparation method comprising: Step 1, crushing solid multifunctional epoxy resin and solid bisphenol A epoxy resin and putting them into a reaction kettle; Step 2, heating the reactor to 110° C. and keeping the temperature for 30 to 60 minutes until the solid inside is completely softened; Step 3, adding solvent to the reaction kettle and stirring for 30 to 60 minutes until the resin is completely dissolved to a uniform state; Step 4, adding a heat-resistant thermoplastic resin into the reaction kettle and stirring for 30 to 60 minutes until the resin is completely dissolved into a uniform state; Step 5, after the reaction kettle is cooled to 80°C, add the polyurethane modified epoxy resin and continue stirring for 30min to 60min until all components are evenly mixed; Step 6, adding fillers to the reactor and stirring for 2 h to 4 h until the added fillers are evenly dispersed; Step 7: After the reaction kettle is cooled to 20° C. to 30° C., add the silane coupling agent, curing agent and accelerator, and stir for 1 h to 2 h until the components are evenly mixed.

10. The method for preparing a high temperature resistant adhesive for motor core punching sheets according to claim 9, characterized in that: The preparation method of the polyurethane modified epoxy resin added in step 5 comprises: Step 51, evacuate the liquid bisphenol A epoxy resin and polypropylene glycol (PPG) at 110° C. to 130° C. for 2 h to 4 h, cool to room temperature and store in a desiccator; wherein the epoxide value of the liquid bisphenol A epoxy resin is 0.50 to 0.60; Step 52, weighing an appropriate amount of 4,4'-diphenylmethane diisocyanate (MDI) and pretreated PPG (n(-NCO) / n(-OH)=2:1) ​​and adding them to a reaction kettle, stirring and heating to 40°C to 60°C, stirring for 20min to 30min under the protection of inert gas, heating to (80±5)°C, and continuing to keep warm and stir for 1h to 2h to obtain a terminal isocyanate polyurethane prepolymer; Step 53, weighing an appropriate amount of terminal isocyanate polyurethane prepolymer and pretreated liquid bisphenol A epoxy resin, adding them into a reaction kettle, stirring and heating to 80° C. to 100° C., reacting for 2 h to 4 h under the protection of inert gas, to obtain the polyurethane modified epoxy resin required for the preparation of the adhesive; wherein the mass ratio of the liquid bisphenol A epoxy resin is 20:100; The pretreatment method of the filler added in step 6 includes: Step 61, weigh an appropriate amount of filler and put it into an electric oven, heat it to 100° C. and dry it for 1 h to 2 h, cool it to room temperature and store it in a desiccator; Step 62, pour the dried filler into a high-speed mixer, add a silane coupling agent solution with a mass fraction of 20% after atomization under stirring at a speed of (1500-2000) r / min, stir for 30-60 minutes and then take it out; wherein the ratio of the silane coupling agent solution is isopropanol: xylene = 1:1; Step 63, drying the treated filler at 110° C. to 120° C. for 2 h to 4 h, cooling to room temperature and storing in a desiccator for later use.

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