Water-borne epoxy resin silicon steel sheet rapid curing self-adhesion coating

Abstract

The invention provides a water-borne epoxy resin silicon steel sheet rapid curing self-adhesion coating, and relates to the technical field of curing coatings. The coating is prepared from water-borne epoxy resin emulsion, ureido pyrimidone modified epoxy resin, gold nanorod and silicon dioxide core-shell particles, silane modified carbon nanohorns, a cationic photoinitiator, a microencapsulated diaminodiphenylmethane curing agent, deionized water, propylene glycol methyl ether acetate and auxiliaries. The ureido pyrimidone modified epoxy resin, the gold nanorod and silicon dioxide core-shell particles, the silane modified carbon nanohorns and the microencapsulated diaminodiphenylmethane curing agent are added into the coating, so that the curing time of the coating is prolonged, meanwhile, a multi-layer stacked structure is formed after the coating is cured, and the adhesive force between the coating and a base material is improved.

Description

Technical Field

[0001] This invention relates to the field of curing coating technology, and more particularly to a water-based epoxy resin self-adhesive coating for rapid curing of silicon steel sheets. Background Technology

[0002] Silicon steel sheets, as the core material of motor cores, have a decisive impact on the energy efficiency and lifespan of motors due to their surface insulating coating. Waterborne epoxy resins, with their low volatile organic compound (VOC) characteristics, have become the mainstream alternative to traditional solvent-based coatings. However, existing waterborne systems exhibit two major drawbacks in practical applications:

[0003] Insufficient curing efficiency: Surface drying time at room temperature generally exceeds 30 minutes, and complete curing requires more than 2 hours, which cannot meet the rhythm requirements of modern high-speed stamping production lines. Weak interfacial bonding: The adhesion strength between the coating and the silicon steel sheet is low, and interlayer delamination easily occurs under high-frequency vibration conditions of the motor, leading to increased core noise and reduced energy efficiency. These defects severely restrict the application and promotion of water-based coatings in the field of high-performance motors.

[0004] To overcome these bottlenecks, the industry has tried various technical approaches, but all have significant shortcomings. Photocuring systems: While achieving surface drying within minutes, the high light-blocking properties of silicon steel sheets lead to incomplete curing of the underlying layer, resulting in soft interlayers in the coating and delamination failure after long-term use. Latent curing agents: Microencapsulation technology can extend shelf life, but the release temperature is often higher than 140℃, exceeding the safe heat treatment window of silicon steel sheets and causing degradation of the substrate's magnetic properties. Nano-reinforcement modification: Adding inorganic nanoparticles can improve strength, but poor dispersion stability causes coating uniformity problems, leading to stress concentration cracks in localized areas. In summary, existing water-based epoxy resin self-adhesive coatings have long curing times and low adhesive strength. Summary of the Invention

[0005] This invention provides a water-based epoxy resin self-adhesive coating for rapid curing of silicon steel sheets, which solves the technical problems of long curing time and low adhesion strength to the substrate in the prior art of water-based epoxy resin self-adhesive coatings.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] A waterborne epoxy resin rapid-curing self-adhesive coating for silicon steel sheets comprises a waterborne epoxy resin emulsion, ureidopyrimidinone modified epoxy resin, gold nanorods@silica core-shell particles, silane-modified carbon nanohorns, a cationic photoinitiator, microencapsulated diaminodiphenylmethane curing agent, deionized water, propylene glycol methyl ether acetate, and additives.

[0008] Preferably, the self-adhesive coating comprises, by weight, 40-50 parts of waterborne epoxy resin emulsion, 12-18 parts of ureidopyrimidinone modified epoxy resin, 0.3-0.8 parts of gold nanorods@silica core-shell particles, 2.0-3.0 parts of silane-modified carbon nanohorns, 1.0-1.5 parts of cationic photoinitiator, 7-10 parts of microencapsulated diaminodiphenylmethane curing agent, 20-25 parts of deionized water, 2-5 parts of propylene glycol methyl ether acetate, and 1.6-3 parts of additives.

[0009] Preferably, the additives, by weight, include 0.5-1.0 parts of leveling agent, 0.3-0.8 parts of defoamer, and 0.8-1.2 parts of thickener.

[0010] Preferably, the epoxy equivalent of the aqueous epoxy resin emulsion is 200-220 g / eq.

[0011] The preparation method of a water-based epoxy resin rapid-curing self-adhesive coating for silicon steel sheets according to the present invention includes the following steps:

[0012] S1. Dissolve 2-amino-4-hydroxy-6-methylpyrimidine in toluene, add hexamethylene diisocyanate, heat and react to remove toluene, and obtain a yellow viscous liquid; mix bisphenol A epoxy resin and toluene, dehydrate, add the yellow viscous liquid and dibutyltin dilaurate, then pour into n-hexane to precipitate, dry, and obtain ureidopyrimidinone modified epoxy resin;

[0013] S2. Add HAuCl4·3H2O and hexadecyltrimethylammonium bromide to water to obtain mixture 1, and add sodium borohydride to obtain seed solution;

[0014] S3. Mix hexadecyltrimethylammonium bromide, HAuCl4·3H2O and silver nitrate and dissolve them in water to obtain mixture 2. Then add ascorbic acid and mix to obtain growth solution.

[0015] S4. The seed solution and growth solution are mixed, allowed to stand, and then centrifuged and washed to obtain gold nanorods;

[0016] S5. Disperse gold nanorods in CTAB aqueous solution to obtain mixture 3, add tetraethyl orthosilicate, stir, centrifuge and wash to obtain Au@SiO2 particles, disperse Au@SiO2 particles in anhydrous ethanol, add 3-mercaptopropyltrimethoxysilane, reflux, centrifuge and dry to obtain gold nanorods@silica core-shell particles.

[0017] S6. Mix the waterborne epoxy emulsion with water, add silane-modified carbon nanoparticles and ureidopyrimidinone-modified epoxy resin and stir.

[0018] S7. Under light-protected conditions, add a mixture of gold nanorods@silica core-shell particles and propylene glycol methyl ether acetate, then add microencapsulated diaminodiphenylmethane curing agent and cationic photoinitiator;

[0019] S8. After adding the additives, stir and filter to obtain the self-adhesive coating.

[0020] Preferably, the bisphenol A epoxy resin, 2-amino-4-hydroxy-6-methylpyrimidine, and hexamethylenetetramine in S1

[0021] The mass ratio of dibutyltin dilaurate to butyltin dilaurate is 400-405:936-940:107-109:0.2-0.3.

[0022] Preferably, the molar concentration of HAuCl4·3H2O in the mixture 1 in S2 is 0.01-0.012M.

[0023] Preferably, the molar concentration of hexadecyltrimethylammonium bromide in mixtures 1, 2 and 3 is 0.1-0.12 M.

[0024] Preferably, the mass concentration of gold nanorods in the mixture 3 in S5 is 0.4-0.6 g / L.

[0025] Preferably, the mass ratio of tetraethyl orthosilicate to gold nanorods in S5 is 0.7-0.9:1.

[0026] Preferably, the preparation method of the microencapsulated diaminodiphenylmethane curing agent includes:

[0027] (1) Pour the PVA aqueous solution into the molten DDM, homogenize, and obtain DDM solution;

[0028] (2) Dissolve dopamine hydrochloride in water, then pour DDM solution into it and place in a constant temperature water bath;

[0029] (3) Add propyl zirconate, react, then centrifuge, wash and dry to obtain microencapsulated diaminodiphenylmethane curing agent.

[0030] Preferred method for preparing silane-modified carbon nano-angles;

[0031] (1) Add carbon nanoparticles to concentrated nitric acid, react, cool, and dilute with deionized water;

[0032] (2) Then, carboxylated carbon nanoparticles are obtained by centrifugation, washing, and drying;

[0033] (3) The carboxylated carbon nanoparticles were mixed with thionyl chloride and reacted. Then the mixture was centrifuged, washed and dried to obtain the acyl chloride modified product.

[0034] (4) The acyl chloride modified product was mixed with toluene, and γ-glycidoxypropyltrimethoxysilane was added. The mixture was reacted, and then centrifuged, washed and dried to obtain silane-modified carbon nanoparticles.

[0035] The self-adhesive coating of this invention has an ultra-fast curing mechanism based on third-order energy-space synergy.

[0036] A light-to-thermal energy conversion layer (gold nanorods@silica) is constructed where free electrons on the surface of the gold nanorods oscillate collectively under a light field, converting photon energy into high-density hot electrons. These hot electrons are then converted into lattice thermal energy within picoseconds via electron-phonon coupling, achieving a transient light-to-thermal conversion. The thermal explosion trigger mechanism involves local hotspot temperatures exceeding the glass transition point of the microcapsule wall material, causing polymer chain segment movement and thawing. Internal pressure induces a brittle-to-ductile transition in the wall material, resulting in millisecond-level explosion and release of the curing agent. Mesoporous silica forms molecular-level reaction cages, confining epoxy groups and the amine curing agent within a nanoscale space. Ureidinone forms tetradentate dimers to construct a supramolecular cross-linked network, enabling rapid curing.

[0037] The self-adhesive coating of this invention exhibits good adhesion. The small curvature of the carbon nanotube pyramid apex leads to localized stress concentration under contact pressure; the pointed tip pierces the oxide layer of the metal surface and embeds itself into the substrate to form a physical anchor. The carbon cone surface has nanoscale roughness, forming a geometrical engagement with the micropores on the surface of the silicon steel sheet. GPTMS silane forms Si-OM covalent bonds on the surface of the metal hydroxyl group through hydrolysis-condensation; the catechol groups in the polydopamine layer form Fe with iron ions. 3+ -Catechol five-membered ring chelates enhance coordination bonds and improve adhesion to the substrate. After film formation, the adhesive layer consists of a multi-layered stack of nano-angle anchoring layers, UPy transition layers, and epoxy matrix layers. The nano-angle anchoring layers provide rigid support to resist shear deformation; the UPy transition layers dissipate energy through hydrogen bond dissociation; and the epoxy matrix layers absorb impact energy during plastic deformation. This multi-layered stacking effectively improves adhesion to the steel sheet surface.

[0038] The solution of the present invention has at least the following advantages compared with the prior art:

[0039] The coating of this invention incorporates ureidopyrimidinone-modified epoxy resin, gold nanorods@silica core-shell particles, silane-modified carbon nanohorns, and microencapsulated diaminodiphenylmethane curing agent to increase the curing time of the coating. At the same time, after the coating is cured, it forms a multi-layered stacked structure, which improves the adhesion between the coating and the substrate. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the present invention will be clearly and completely described below in conjunction with the technical solutions of the embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0041] The waterborne epoxy resin emulsion is from Guangzhou JITAI Chemical Co., Ltd., JT-EP2300200-220 (customizable), with a solid content of 50% and a narrow particle size distribution (D50=150nm).

[0042] The preparation method of microencapsulated diaminodiphenylmethane curing agent can refer to the following steps;

[0043] Step 1: DDM emulsification

[0044] Add 410 grams of DDM to the reactor, purge with nitrogen for protection, and heat to 90°C to melt it into a liquid.

[0045] Take 5 grams of PVA (PVA1788) and add it to 1 liter of deionized water. Stir and dissolve at 80°C, then cool to 40°C for later use.

[0046] Turn on the stirring in the reactor (300 rpm) and slowly pour the PVA aqueous solution into the molten DDM (complete the addition within 10 minutes).

[0047] The mixture was transferred to a high-pressure homogenizer and circulated three times at 80 MPa pressure to obtain a milky white emulsion (particle size 2.6 micrometers).

[0048] Step 2: Wall Material Deposition

[0049] Preparation of dopamine-Tris solution:

[0050] Dissolve 10 grams of dopamine hydrochloride in 500 ml of deionized water, and adjust the pH to 8.5 with Tris powder.

[0051] Pour the DDM solution into the dopamine solution and place it in a 40°C constant temperature water bath.

[0052] Start stirring at 200 rpm and add propyl zirconate dropwise at a rate of 1.7 ml per hour (total 20 ml, over 12 hours) using a peristaltic pump.

[0053] The solution gradually changes from brown to dark black (indicating the formation of polydopamine).

[0054] Step 3: Post-processing

[0055] Pour the reaction solution into a centrifuge tube, centrifuge at 3000 rpm for 10 minutes, and discard the supernatant.

[0056] Wash the precipitate in sequence:

[0057] First application: 200 ml of ammonia / ethanol mixture (1:1 volume ratio)

[0058] Second and third times: 200 ml of anhydrous ethanol each time.

[0059] The wet microcapsules were laid flat on a tray and dried in a vacuum oven at 40°C for 2 hours to obtain 495 grams of dried microencapsulated diaminodiphenylmethane curing agent.

[0060] Detailed preparation method of silane-modified carbon nano-angles;

[0061] Step 1: Carboxylation treatment (strong oxidation to open pores)

[0062] Take 800g of raw carbon nanoparticles (average diameter 80nm, purity >95%) and place them in a 5L three-necked flask. Add 24L of 68% concentrated nitric acid. Install a condenser and a tail gas absorption device (using 10% sodium hydroxide solution to absorb NOx gas). Turn on the oil bath and heat to 120℃, then turn on the stirring (300 rpm) and maintain a vigorous reflux state for 6 hours.

[0063] After the reaction is complete, allow it to cool naturally to below 60°C. Transfer the reaction solution to a 50-liter plastic container and dilute with 240 liters of deionized water. Centrifuge at 8000 rpm for 15 minutes and discard the supernatant. Repeat the "wash-centrifugation" process until the pH of the supernatant reaches 6 (approximately 8 times). Transfer the precipitate to a stainless steel tray and dry it in an 80°C vacuum drying oven for 24 hours to obtain carboxylated carbon nanoparticles (COOH-CNH).

[0064] Step 2: Acyl chloride reaction (conversion of active groups)

[0065] The dried COOH-CNH was placed in a vacuum drying oven and dehydrated at 100°C for 12 hours (vacuum degree -0.1 MPa). The dehydrated COOH-CNH was then transferred to a 10-liter pressure-resistant reactor, and 16 liters of anhydrous thionyl chloride (SOCl2) were added. The reactor was sealed, and nitrogen was purged three times to replace the air. The stirring was started (400 rpm), and the oil bath temperature was raised to 70°C and maintained for 24 hours.

[0066] After the reaction was complete, the temperature was lowered to 45°C, and the unreacted thionyl chloride was recovered by distillation using a rotary evaporator (water bath temperature 45°C, vacuum degree -0.1 MPa). The residue was washed three times with anhydrous diethyl ether (5 liters each time), centrifuged, and dried under vacuum at 40°C to obtain the acyl chloride-modified product (COCl-CNH).

[0067] Step 3: Silane grafting (covalent bond fixation)

[0068] Add all of the COCl-CNH to a 20-liter glass reactor, then inject 8 liters of anhydrous toluene. Perform ultrasonic dispersion (800W power, 20mm probe diameter) for 30 minutes to form a homogeneous suspension.

[0069] Add 240 g of γ-glycidoxypropyltrimethoxysilane (GPTMS), and install a water separator and condenser. Heat the oil bath to 110°C, start stirring (350 rpm), and reflux under nitrogen protection for 8 hours. During this period, sample the system every 2 hours to detect the moisture content (Kal Fischer method control ≤200 ppm).

[0070] The reaction solution was cooled to 50°C and then centrifuged (6000 rpm × 10 min). The precipitate was washed sequentially with the following solvents:

[0071] Toluene: 5 liters × 1 time (to remove physically adsorbed silanes)

[0072] Acetone: 5 liters x 2 times (to remove oligomers)

[0073] Ethanol: 5 liters × 1 time (dehydration)

[0074] The washed product was dried in a vacuum drying oven at 60°C for 48 hours to obtain silane-modified carbon nanoparticles.

[0075] The thickener is 2-hydroxyethyl ether cellulose, CAS No.: 9004-62-0.

[0076] The defoamer is polydimethylsiloxane with a molecular weight of 2000 Da.

[0077] Example 1

[0078] A waterborne epoxy resin rapid-curing self-adhesive coating for silicon steel sheets comprises, by weight, 40 parts of waterborne epoxy resin emulsion (epoxy equivalent of 200 g / eq), 12 parts of ureidopyrimidinone modified epoxy resin, 0.3 parts of gold nanorods@silica core-shell particles, 2.0 parts of silane-modified carbon nanohorns, 1.0 part of diphenyliodonium hexafluorophosphate, 7 parts of microencapsulated diaminodiphenylmethane curing agent, 20 parts of deionized water, 2 parts of propylene glycol methyl ether acetate, 0.5 parts of polyether-modified siloxane BYK-333, 0.3 parts of polydimethylsiloxane, and 0.8 parts of 2-hydroxyethyl ether cellulose.

[0079] A method for preparing a water-based epoxy resin silicon steel sheet rapid-curing self-adhesive coating in this embodiment includes the following steps:

[0080] S1. Dissolve 2-amino-4-hydroxy-6-methylpyrimidine in toluene (feed ratio 5g:1000mL), stir at 60℃ to dissolve, add hexamethylene diisocyanate dropwise, heat to 80℃ and react for 4h, remove toluene by vacuum distillation to obtain a yellow viscous liquid; mix bisphenol A epoxy resin and toluene (feed ratio 5g:1000mL), dehydrate at 110℃ under reduced pressure for 1h, cool to 75℃, add all of the yellow viscous liquid and dibutyltin dilaurate, react under nitrogen protection for 5h at 75℃; pour the reaction solution into 5000mL of n-hexane to precipitate, and vacuum dry (60℃ / 24h) to obtain ureidylpyrimidinone modified epoxy resin;

[0081] The mass ratio of bisphenol A epoxy resin (EEW=210), 2-amino-4-hydroxy-6-methylpyrimidine, hexamethylene diisocyanate and dibutyltin dilaurate is 400:936:107:0.2;

[0082] S2. Add HAuCl4·3H2O and hexadecyltrimethylammonium bromide to water to obtain mixture 1. The molar concentration of HAuCl4·3H2O in mixture 1 is 0.01M. Add sodium borohydride to obtain seed solution. The molar ratio of sodium borohydride to HAuCl4·3H2O is 5:1.

[0083] S3. Mix hexadecyltrimethylammonium bromide, HAuCl4·3H2O and silver nitrate in a molar ratio of 10:1:0.10 and dissolve them in water to obtain mixture 2. Add ascorbic acid, with a molar ratio of ascorbic acid to HAuCl4·3H2O of 1.8:1, and mix well to obtain the growth solution.

[0084] S4. The seed solution and growth solution are mixed at a volume ratio of 1:800, and the mixture is allowed to stand at 25°C for 10 hours. After centrifugation and washing with ethanol, gold nanorods are obtained.

[0085] S5. Gold nanorods were dispersed in an aqueous solution of CTAB (hexadecyltrimethylammonium bromide) to obtain mixture 3, in which the mass concentration of gold nanorods was 0.4 g / L. Sodium hydroxide was added to adjust the pH to 10.0, and tetraethyl orthosilicate was added dropwise. The mass ratio of tetraethyl orthosilicate to gold nanorods was 0.7:1. The mixture was stirred at 35°C for 3 hours, centrifuged, and washed with ethanol to obtain Au@SiO2 particles. The Au@SiO2 particles were dispersed in anhydrous ethanol (the ratio of Au@SiO2 particles to anhydrous ethanol was 1 g:10 mL), and 3-mercaptopropyltrimethoxysilane (MPTES) was added (the mass ratio of MPTES to gold nanorods was 0.6:1). The mixture was refluxed at 55°C for 3 hours, centrifuged, and dried to obtain gold nanorod@silica core-shell particles.

[0086] The molar concentration of hexadecyltrimethylammonium bromide in mixtures 1, 2, and 3 described above is 0.1 M.

[0087] S6. Mix the aqueous epoxy emulsion with deionized water (half the mass of the aqueous epoxy emulsion). Add silane-modified carbon nanoparticles and ureidopyrimidinone-modified epoxy resin and stir to mix.

[0088] S7. Under light-protected conditions, add the mixture of gold nanorods@silica core-shell particles and propylene glycol methyl ether acetate, stir evenly, then add microencapsulated diaminodiphenylmethane curing agent and cationic photoinitiator, and mix evenly.

[0089] S8. After adding the additives, stir evenly and filter to obtain the self-adhesive coating.

[0090] Example 2

[0091] A waterborne epoxy resin rapid-curing self-adhesive coating for silicon steel sheets comprises, by weight, 45 parts of waterborne epoxy resin emulsion (epoxy equivalent of 210 g / eq), 16 parts of ureidopyrimidinone modified epoxy resin, 0.5 parts of gold nanorods@silica core-shell particles, 2.5 parts of silane-modified carbon nanohorns, 1.2 parts of diphenyliodonium hexafluorophosphate, 8 parts of microencapsulated diaminodiphenylmethane curing agent, 22 parts of deionized water, 3 parts of propylene glycol methyl ether acetate, 0.7 parts of polyether-modified siloxane BYK-333, 0.5 parts of polydimethylsiloxane, and 1 part of 2-hydroxyethyl ether cellulose.

[0092] A method for preparing a water-based epoxy resin silicon steel sheet rapid-curing self-adhesive coating in this embodiment includes the following steps:

[0093] S1. Dissolve 2-amino-4-hydroxy-6-methylpyrimidine in toluene (feed ratio 5g:1000mL), stir at 62℃ to dissolve, add hexamethylene diisocyanate dropwise, heat to 82℃ and react for 5h, remove toluene by vacuum distillation to obtain a yellow viscous liquid; mix bisphenol A epoxy resin and toluene (feed ratio 5g:1000mL), dehydrate at 115℃ under reduced pressure for 1.2h, cool to 78℃, add (all) of the yellow viscous liquid and dibutyltin dilaurate, react under nitrogen protection for 5.5h at 78℃; pour the reaction solution into 5000mL of n-hexane to precipitate, and vacuum dry (60℃ / 24h) to obtain ureidylpyrimidinone modified epoxy resin;

[0094] The mass ratio of bisphenol A epoxy resin (EEW=210), 2-amino-4-hydroxy-6-methylpyrimidine, hexamethylene diisocyanate and dibutyltin dilaurate is 403:938:108:0.25;

[0095] S2. Add HAuCl4·3H2O and hexadecyltrimethylammonium bromide to water to obtain mixture 1. The molar concentration of HAuCl4·3H2O in mixture 1 is 0.011M. Add sodium borohydride to obtain seed solution. The molar ratio of sodium borohydride to HAuCl4·3H2O is 6:1.

[0096] S3. Mix hexadecyltrimethylammonium bromide, HAuCl4·3H2O and silver nitrate in a molar ratio of 11:1:0.12 and dissolve them in water to obtain mixture 2. Add ascorbic acid, with a molar ratio of ascorbic acid to HAuCl4·3H2O of 1.9:1, and mix well to obtain the growth solution.

[0097] S4. The seed solution and growth solution are mixed at a volume ratio of 1:850, and the mixture is allowed to stand at 28°C for 12 hours. After centrifugation and washing with ethanol, gold nanorods are obtained.

[0098] S5. Gold nanorods were dispersed in CTAB aqueous solution to obtain mixture 3, in which the mass concentration of gold nanorods was 0.5 g / L. Sodium hydroxide was added to adjust the pH to 11, and tetraethyl orthosilicate was added dropwise. The mass ratio of tetraethyl orthosilicate to gold nanorods was 0.8:1. The mixture was stirred at 38°C for 4 hours, centrifuged, and washed with ethanol to obtain Au@SiO2 particles. The Au@SiO2 particles were dispersed in anhydrous ethanol (the ratio of Au@SiO2 particles to anhydrous ethanol was 1 g:10 mL), and 3-mercaptopropyltrimethoxysilane (MPTES) was added (the mass ratio of MPTES to gold nanorods was 0.6:1). The mixture was refluxed at 60°C for 4 hours, centrifuged, and dried to obtain gold nanorod@silica core-shell particles.

[0099] The molar concentration of hexadecyltrimethylammonium bromide in mixtures 1, 2, and 3 is 0.11 M.

[0100] S6. Mix the aqueous epoxy emulsion with deionized water (half the mass of the aqueous epoxy emulsion) until homogeneous. Add silane-modified carbon nanoparticles and ureidopyrimidinone-modified epoxy resin and stir until homogeneous.

[0101] S7. Under light-protected conditions, add the mixture of gold nanorods@silica core-shell particles and propylene glycol methyl ether acetate, stir evenly, then add microencapsulated diaminodiphenylmethane curing agent and cationic photoinitiator, and mix evenly.

[0102] S8. After adding the additives, stir evenly and filter to obtain the self-adhesive coating.

[0103] Example 3

[0104] A waterborne epoxy resin rapid-curing self-adhesive coating for silicon steel sheets comprises, by weight, 50 parts of waterborne epoxy resin emulsion (epoxy equivalent of 220 g / eq), 18 parts of ureidopyrimidinone modified epoxy resin, 0.8 parts of gold nanorods@silica core-shell particles, 3.0 parts of silane-modified carbon nanohorns, 1.5 parts of diphenyliodonium hexafluorophosphate, 10 parts of microencapsulated diaminodiphenylmethane curing agent, 25 parts of deionized water, 5 parts of propylene glycol methyl ether acetate, 1.0 part of polyether-modified siloxane BYK-333, 0.8 parts of polydimethylsiloxane, and 1.2 parts of 2-hydroxyethyl ether cellulose.

[0105] A method for preparing a water-based epoxy resin silicon steel sheet rapid-curing self-adhesive coating in this embodiment includes the following steps:

[0106] S1. Dissolve 2-amino-4-hydroxy-6-methylpyrimidine in toluene (feed ratio 5g:1000mL), stir at 65℃ to dissolve, add hexamethylene diisocyanate dropwise, heat to 85℃ and react for 6h, remove toluene by vacuum distillation to obtain a yellow viscous liquid; mix bisphenol A epoxy resin and toluene (feed ratio 5g:1000mL), dehydrate at 120℃ under reduced pressure for 1.5h, cool to 80℃, add (all) of the yellow viscous liquid and dibutyltin dilaurate, react under nitrogen protection for 6h at 80℃; pour the reaction solution into 5000mL of n-hexane to precipitate, and vacuum dry (60℃ / 24h) to obtain ureidylpyrimidinone modified epoxy resin;

[0107] The mass ratio of bisphenol A epoxy resin (EEW=210), 2-amino-4-hydroxy-6-methylpyrimidine, hexamethylene diisocyanate and dibutyltin dilaurate is 405:940:109:0.3;

[0108] S2. Add HAuCl4·3H2O and hexadecyltrimethylammonium bromide to water to obtain mixture 1. The molar concentration of HAuCl4·3H2O in mixture 1 is 0.012M. Add sodium borohydride to obtain seed solution. The molar ratio of sodium borohydride to HAuCl4·3H2O is 7:1.

[0109] S3. Mix hexadecyltrimethylammonium bromide, HAuCl4·3H2O and silver nitrate in a molar ratio of 12:1:0.15 and dissolve them in water to obtain mixture 2. Add ascorbic acid, with a molar ratio of ascorbic acid to HAuCl4·3H2O of 2.2:1, and mix well to obtain the growth solution.

[0110] S4. The seed solution and growth solution are mixed at a volume ratio of 1:900, and the mixture is allowed to stand at 30°C for 14 hours. After centrifugation and washing with ethanol, gold nanorods are obtained.

[0111] S5. Gold nanorods were dispersed in CTAB aqueous solution to obtain mixture 3, in which the mass concentration of gold nanorods was 0.6 g / L. Sodium hydroxide was added to adjust the pH to 10.0, and tetraethyl orthosilicate was added dropwise. The mass ratio of tetraethyl orthosilicate to gold nanorods was 0.9:1. The mixture was stirred at 45°C for 5 hours, centrifuged, and washed with ethanol to obtain Au@SiO2 particles. The Au@SiO2 particles were dispersed in anhydrous ethanol (the ratio of Au@SiO2 particles to anhydrous ethanol was 1 g:10 mL), and 3-mercaptopropyltrimethoxysilane (MPTES) was added (the mass ratio of MPTES to gold nanorods was 0.6:1). The mixture was refluxed at 65°C for 5 hours, centrifuged, and dried to obtain gold nanorod@silica core-shell particles with a mass concentration of 0.6 g / L.

[0112] The molar concentration of hexadecyltrimethylammonium bromide in mixtures 1, 2, and 3 is 0.12 M.

[0113] S6. Mix the aqueous epoxy emulsion with deionized water (half the mass of the aqueous epoxy emulsion) until homogeneous. Add silane-modified carbon nanoparticles and ureidopyrimidinone-modified epoxy resin and stir until homogeneous.

[0114] S7. Under light-protected conditions, add the mixture of gold nanorods@silica core-shell particles and propylene glycol methyl ether acetate, stir evenly, then add microencapsulated diaminodiphenylmethane curing agent and cationic photoinitiator, and stir evenly.

[0115] S8. After adding the additives, stir evenly and filter to obtain the self-adhesive coating.

[0116] Comparative Example 1

[0117] This comparative example is the same as Example 1, except that in this comparative example, gold nanorods@silica core-shell particles are replaced in equal amounts with ureidopyrimidinone modified epoxy resin.

[0118] Comparative Example 2

[0119] This comparative example is the same as Example 1, except that the silane-modified carbon nano-angles are replaced with carbon nano-angles.

[0120] Comparative Example 3

[0121] This comparative example is the same as Example 1, except that the mass concentration of gold nanorods in the mixture 3 described in S5 in this comparative example is 0.2 g / L.

[0122] Comparative Example 4

[0123] This comparative example is the same as Example 1, except that Au@SiO2 particles are used in this comparative example instead of gold nanorods@silica core-shell particles in Example 1. Specifically, S5 in this comparative example is as follows: gold nanorods are dispersed in an aqueous solution of CTAB (hexadecyltrimethylammonium bromide) to obtain mixture 3, the mass concentration of gold nanorods in mixture 3 is 0.4 g / L, sodium hydroxide is added to adjust the pH to 10.0, and tetraethyl orthosilicate is added dropwise. The mass ratio of tetraethyl orthosilicate to gold nanorods is 0.7:1. The mixture is stirred at 35°C for 3 hours, centrifuged, and washed with ethanol to obtain Au@SiO2 particles.

[0124] The surface drying time of the coatings in Examples 1-3 and Comparative Examples 1-4 was determined. The test method was based on the national standard GB / T 1728. The test results are shown in Table 1.

[0125] Table 1 Surface drying time of each group of coatings / s

[0126] It can be seen that the coating of the present invention has a short surface drying time and can achieve fast drying.

[0127] The coatings from Examples 1-3 and Comparative Examples 1-4 were used to test the bonding strength of silicon steel sheets according to the international standard ISO4587. The test results are shown in Table 2.

[0128] Table 2. Adhesion strength of silicon steel sheets for each group of coatings

[0129] It can be seen that the coating of the present invention has better adhesion to the substrate.

[0130] The test data from Comparative Example 1 and Comparative Example 1 show that replacing the gold nanorods@silica core-shell particles with ureidopyrimidinone-modified epoxy resin deteriorates the coating performance. This is because the gold nanorods@silica core-shell particles possess nanoscale effects and good dispersibility, acting as "nanofillers" to accelerate molecular motion and cross-linking reactions in the coating system, while enhancing the physical connections within the coating (such as hydrogen bonds and mechanical interlocking). After removal, the system lacks the catalytic and reinforcing effects of nanoparticles, leading to a decrease in curing rate (prolonged surface drying time), weakened internal forces within the coating, and reduced adhesive strength.

[0131] The test data from Comparative Example 1 and Comparative Example 2 show that replacing the silane-modified carbon nanoparticles with unmodified carbon nanoparticles degrades the coating performance. Silane-modified carbon nanoparticles, through silane groups (such as alkoxy groups), can chemically react with the hydroxyl and epoxy groups of waterborne epoxy resins, achieving chemical bonding with the resin matrix and improving the dispersibility of the carbon nanoparticles in the waterborne system. Unmodified carbon nanoparticles lack active groups on their surface, have poor compatibility with the resin, and are prone to aggregation, leading to defects within the coating, decreased curing uniformity (slightly prolonged surface drying time), weakened mechanical reinforcement, and significantly reduced adhesive strength.

[0132] In Comparative Example 3, the mass concentration of gold nanorods in mixture 3 was 0.2 g / L (lower than 0.4 g / L in Example 1). The concentration of the gold nanorods@silica core-shell particle precursor (gold nanorods) was reduced, ultimately decreasing the actual content of core-shell particles in the coating. When the concentration of gold nanorods@silica core-shell particles is insufficient, their catalytic effect on the curing reaction (such as promoting cross-linking on the nanoparticle surface) and physical reinforcing effect are weakened. On the one hand, the curing rate decreases, leading to a longer surface drying time; on the other hand, the number of nanoscale reinforcing points inside the coating decreases, resulting in reduced overall mechanical properties and decreased adhesive strength.

[0133] Comparative Example 4 used Au@SiO2 particles (without MPTES modification). The core-shell particles lacked 3-mercaptopropyltrimethoxysilane (MPTES) modification, and their surfaces lacked thiol (-SH) and methoxy (-OCH3) groups. MPTES modification introduces thiol groups (which bind to the gold nanorod core, enhancing core-shell structure stability) and methoxy groups (which react with the hydroxyl / epoxy groups of epoxy resin, improving compatibility with the resin matrix) onto the Au@SiO2 particle surface. The unmodified Au@SiO2 particles exhibited weak interfacial bonding with the resin, easily forming "islands" in the coating, leading to hindered molecular cross-linking during curing (prolonged surface drying time) and decreased interfacial adhesion strength between the coating and the silicon steel sheet.

[0134] Each comparative study disrupted the synergistic effect of "catalysis-reinforcement-compatibility" in the coating system by altering key components (nanoparticle type, concentration, surface modification) or raw material modification state, resulting in prolonged surface drying time and reduced adhesive strength. This indicates that the concentration and surface modification of gold nanorods@silica core-shell particles, as well as the chemical compatibility of silane-modified carbon nanoangles, are key factors in ensuring rapid curing and high adhesive strength of the coating.

[0135] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. The scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A water-based epoxy resin rapid-curing self-adhesive coating for silicon steel sheets, characterized in that, It includes waterborne epoxy resin emulsion, ureidopyrimidinone modified epoxy resin, gold nanorods@silica core-shell particles, silane-modified carbon nanohorns, cationic photoinitiator, microencapsulated diaminodiphenylmethane curing agent, deionized water, propylene glycol methyl ether acetate, and additives.

2. The water-based epoxy resin rapid-curing self-adhesive coating for silicon steel sheets according to claim 1, characterized in that, The self-adhesive coating comprises, by weight, 40-50 parts of waterborne epoxy resin emulsion, 12-18 parts of ureidopyrimidinone modified epoxy resin, 0.3-0.8 parts of gold nanorods@silica core-shell particles, 2.0-3.0 parts of silane-modified carbon nanohorns, 1.0-1.5 parts of cationic photoinitiator, 7-10 parts of microencapsulated diaminodiphenylmethane curing agent, 20-25 parts of deionized water, 2-5 parts of propylene glycol methyl ether acetate, and 1.6-3 parts of additives.

3. The water-based epoxy resin silicon steel sheet rapid-curing self-adhesive coating according to claim 1, characterized in that, The additives, by weight, include 0.5-1.0 parts of leveling agent, 0.3-0.8 parts of defoamer, and 0.8-1.2 parts of thickener.

4. The water-based epoxy resin silicon steel sheet rapid-curing self-adhesive coating according to claim 1, characterized in that, The epoxy equivalent of the aqueous epoxy resin emulsion is 200-220 g / eq.

5. The water-based epoxy resin rapid-curing self-adhesive coating for silicon steel sheets according to claim 1, characterized in that, The preparation method of the self-adhesive coating includes the following steps: S1. Dissolve 2-amino-4-hydroxy-6-methylpyrimidine in toluene, add hexamethylene diisocyanate, heat and react to remove toluene, and obtain a yellow viscous liquid; mix bisphenol A epoxy resin and toluene, dehydrate, add the yellow viscous liquid and dibutyltin dilaurate, then pour into n-hexane to precipitate, dry, and obtain ureidopyrimidinone modified epoxy resin; S2. Add HAuCl4·3H2O and hexadecyltrimethylammonium bromide to water to obtain mixture 1, and add sodium borohydride to obtain seed solution; S3. Mix hexadecyltrimethylammonium bromide, HAuCl4·3H2O and silver nitrate and dissolve them in water to obtain mixture 2. Then add ascorbic acid and mix to obtain growth solution. S4. The seed solution and growth solution are mixed, allowed to stand, and then centrifuged and washed to obtain gold nanorods; S5. Disperse gold nanorods in CTAB aqueous solution to obtain mixture 3, add tetraethyl orthosilicate, stir, centrifuge and wash to obtain Au@SiO2 particles, disperse Au@SiO2 particles in anhydrous ethanol, add 3-mercaptopropyltrimethoxysilane, reflux, centrifuge and dry to obtain gold nanorods@silica core-shell particles. S6. Mix the waterborne epoxy emulsion with water, add silane-modified carbon nanoparticles and ureidopyrimidinone-modified epoxy resin and stir. S7. Under light-protected conditions, add a mixture of gold nanorods@silica core-shell particles and propylene glycol methyl ether acetate, then add microencapsulated diaminodiphenylmethane curing agent and cationic photoinitiator; S8. After adding the additives, stir and filter to obtain the self-adhesive coating.

6. The water-based epoxy resin silicon steel sheet rapid-curing self-adhesive coating according to claim 5, characterized in that, The mass ratio of bisphenol A epoxy resin, 2-amino-4-hydroxy-6-methylpyrimidine, hexamethylene diisocyanate and dibutyltin dilaurate in S1 is 400-405:936-940:107-109:0.2-0.

3.

7. The water-based epoxy resin rapid-curing self-adhesive coating for silicon steel sheets according to claim 5, characterized in that, The molar concentration of HAuCl4·3H2O in the mixture 1 described in S2 is 0.01-0.012M.

8. The water-based epoxy resin rapid-curing self-adhesive coating for silicon steel sheets according to claim 5, characterized in that, The molar concentration of hexadecyltrimethylammonium bromide in mixtures 1, 2, and 3 is 0.1-0.12 M.

9. The water-based epoxy resin silicon steel sheet rapid-curing self-adhesive coating according to claim 5, characterized in that, The mass concentration of gold nanorods in the mixture 3 described in S5 is 0.4-0.6 g / L.

10. The water-based epoxy resin silicon steel sheet rapid-curing self-adhesive coating according to claim 5, characterized in that, The mass ratio of tetraethyl orthosilicate to gold nanorods in S5 is 0.7-0.9:1.

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