Bisphenol a epoxy-polyether amine hybrid matte electrophoretic paint emulsion and preparation method thereof

Abstract

This application relates to the field of waterborne cathodic electrophoretic coating technology, specifically disclosing a bisphenol A epoxy-polyetheramine composite matte electrophoretic emulsion and its preparation method. The bisphenol A epoxy-polyetheramine composite matte electrophoretic emulsion comprises the following raw materials in parts by weight: 30-40 parts E-51 epoxy resin, 8-10 parts bisphenol A, 9-11 parts bisphenol A polyoxyethylene ether, 0.08-0.12 parts benzylamine, 2.5-3.5 parts methylethanolamine, 0.8-1.2 parts diethylene glycolamine, and 2.5-3.5 parts ketimine. This application uses E-51 epoxy resin, bisphenol A, and bisphenol A polyoxyethylene ether as the matrix skeleton, and obtains an epoxy equivalent prepolymer after chain extension catalyzed by benzylamine. At the same time, toluene diisocyanate is reacted with diethylene glycol butyl ether, diethylene glycol ethyl ether, and trimethylolpropane polyoxyethylene ether to prepare a blocked crosslinking agent, thereby achieving a uniform internal matting effect without the addition of external matting powder.

Description

Technical Field

[0001] This application relates to the field of waterborne cathodic electrophoretic coating technology, and more specifically, to a bisphenol A epoxy-polyetheramine composite matte electrophoretic emulsion and its preparation method. Background Technology

[0002] Electrophoretic coating is a coating method that uses an external electric field to deposit charged resin particles suspended in water onto the surface of a workpiece. Cathodic electrophoretic coatings use epoxy resin, acrylic resin, etc. as the matrix, and after amination modification, the resin is endowed with cationicity. Under the action of a DC electric field, a film is deposited on the surface of the cathode workpiece, and after high-temperature baking and curing, a dense protective coating is formed. With the continuous improvement of the requirements for corrosion resistance and coating appearance of metal parts in high-end manufacturing fields such as marine engineering equipment, high-speed railway, and aerospace, the application demand of cathodic electrophoretic coatings in these fields is also increasing, especially for coating systems that have both excellent salt spray resistance and stable matte appearance.

[0003] Existing matte electrophoretic coating emulsions mostly achieve a matte effect by adding matting powder. This involves mixing the matting powder into the electrophoretic emulsion or color paste through high-speed dispersion or grinding. The matting powder particles form a micro-rough structure on the coating surface to scatter incident light, thereby reducing gloss. However, the added matting powder has a significant density difference from the resin matrix, making it prone to gravitational settling during emulsion storage. The introduction of matting powder also reduces the electrophoretic coating's penetration, easily leading to a thinner coating and higher gloss in the interior or recessed areas of the workpiece, resulting in unstable coating gloss. Summary of the Invention

[0004] To address the problem that existing matte photocoating emulsions tend to result in thinner coatings and higher gloss in the interior or recessed areas of workpieces, leading to unstable coating gloss, this application provides a bisphenol A epoxy-polyetheramine composite matte photocoating emulsion and its preparation method.

[0005] The bisphenol A epoxy-polyetheramine composite matte photophoretic emulsion and its preparation method provided in this application adopt the following technical solution: In the first aspect, this application provides a bisphenol A epoxy-polyetheramine composite matte photocoating emulsion, which adopts the following technical solution: The bisphenol A epoxy-polyetheramine composite matte photocoating emulsion comprises the following raw materials in parts by weight: 30-40 parts E-51 epoxy resin, 8-10 parts bisphenol A, 9-11 parts bisphenol A polyoxyethylene ether, 0.08-0.12 parts benzylamine, 2.5-3.5 parts methyl ethanolamine, 0.8-1.2 parts diethylene glycolamine, 2.5-3.5 parts ketimine, 1.2-1.8 parts polyetheramine, 1.2-1.8 parts polyether polyol, 14-16 parts toluene diisocyanate, 8-10 parts diethylene glycol butyl ether, 10-12 parts diethylene glycol ethyl ether, 1.8-2.2 parts trimethylolpropane polyoxyethylene ether, 1.5-2.5 parts methyl isobutyl ketone, 1.5-2.5 parts organic glacial acetic acid, and 140-160 parts deionized water.

[0006] By adopting the above technical solution, an epoxy equivalent prepolymer is obtained by using E-51 epoxy resin, bisphenol A, and bisphenol A polyoxyethylene ether as the matrix skeleton and then performing chain extension catalyzed by benzylamine. Simultaneously, a blocked crosslinking agent is prepared by reacting toluene diisocyanate with diethylene glycol butyl ether, diethylene glycol ethyl ether, and trimethylolpropane polyoxyethylene ether. This agent is stable at room temperature and deblocks and participates in crosslinking during the high-temperature curing stage, forming a microphase separation structure with the epoxy-amine resin system. This achieves a uniform internal matting effect without the addition of external matting powder, avoiding the storage sedimentation problem caused by density differences in matting powder. Furthermore, the crosslinking agent is dispersed at the molecular level within the resin matrix. In the grease, it will not block the electrophoretic deposition channels or interfere with the electric field distribution, thus maintaining high penetration. This ensures that the coating thickness and gloss in the interior and recessed areas of the workpiece are consistent with the surface. Methyl ethanolamine, diethylene glycolamine, and ketimine synergistically amination impart cationic water dispersibility to the resin and introduce latent curing crosslinking points. Polyetheramine and polyether polyol provide flexible segments to enhance adhesion and toughness, achieving a balance between storage stability, coating gloss uniformity, penetration, and coating mechanical properties. This solves the problem that existing matte electrophoretic paint emulsions tend to result in thinner coatings and higher gloss in the interior or recessed areas of the workpiece, leading to unstable coating gloss.

[0007] Preferably, it also includes 0.5-1 parts by weight of photoinitiator and 1.5-2.5 parts by weight of glycidyl methacrylate.

[0008] By adopting the above technical solution, glycidyl methacrylate is introduced into the resin system as a photosensitive graft monomer. The epoxy groups in its molecule can react with the active hydroxyl or amine groups on the resin chain to graft the photosensitive groups of acrylate onto the resin molecular chain. At the same time, a photoinitiator is added. After electrophoretic film formation, the grafted and modified resin can undergo rapid free radical polymerization of acrylate groups under ultraviolet light irradiation, so that the coating surface is pre-crosslinked and shaped. This ultraviolet pre-curing and subsequent thermal curing form a dual curing mechanism. Ultraviolet curing can reduce coating sagging and micro-defect formation during thermal curing, making the coating more dense and uniform, thereby further improving salt spray resistance, while not affecting the basic gloss and adhesion of the coating.

[0009] Preferably, it also includes a modified graphene predispersant, which is prepared by ultrasonically dispersing 0.3-0.8 parts by weight of graphene oxide, 50-70% of polyetheramine, and 5-10 parts by weight of deionized water for 30-60 minutes.

[0010] By adopting the above technical solution, non-covalent modification of graphene oxide with polyetheramine is used to improve the dispersion stability of graphene in aqueous resin system. After the modified graphene pre-dispersion is uniformly dispersed in the coating, the graphene nanosheets form a physical shielding network inside the coating, which prolongs the penetration path of corrosive media. Thus, without affecting the storage stability of the emulsion and the matte appearance of the coating, the salt spray resistance of the coating is further improved.

[0011] Preferably, the amine value of the ketimine is 200-300 mg KOH / g.

[0012] By adopting the above technical solution, the ketimine has good hydrolytic stability in the emulsion and can release primary amine groups in a timely manner during the thermosetting stage to participate in the crosslinking reaction of epoxy groups and isocyanate groups, effectively increasing the crosslinking point density and supplementing crosslinking sites.

[0013] Preferably, the polyether amine has a molecular weight of 1500-2500 and an amine value of 40-60 mg KOH / g, and the polyether polyol has a molecular weight of 800-1200 and a hydroxyl value of 100-120 mg KOH / g.

[0014] By adopting the above technical solution, polyetheramine has a moderate chain length and reactivity, which can provide sufficient flexibility for the coating without affecting the crosslinking density. The polyether polyol has good compatibility with the resin system, ensuring that an appropriate amount of reactive hydroxyl groups participate in crosslinking. The two work together to introduce flexible chain segments, reduce the internal stress of the coating, enhance the interfacial bonding force between the coating and the metal substrate, stabilize the adhesion of the coating, and maintain good hardness and salt spray resistance.

[0015] Secondly, this application provides a method for preparing a bisphenol A epoxy-polyetheramine composite matte photophoretic emulsion, using the following technical solution: A method for preparing a bisphenol A epoxy-polyetheramine composite matte photocoating emulsion, applicable to the above-mentioned bisphenol A epoxy-polyetheramine composite matte photocoating emulsion, includes the following steps: S1. Under nitrogen protection, toluene diisocyanate, diethylene glycol butyl ether, diethylene glycol ethyl ether, and trimethylolpropane polyoxyethylene ether are reacted at 70-85℃ until the isocyanate content is 0 to obtain a blocked crosslinking agent. S2. Add benzylamine to E-51 epoxy resin, bisphenol A, and bisphenol A polyoxyethylene ether at 110-130℃ to carry out chain extension reaction until the epoxy equivalent reaches 900-1500g / eq, forming a premix. S3. Cool the premix to 90-100℃, add methyl isobutyl ketone and blocking crosslinking agent, stir and mix to form a crosslinking mixture; S4. Add methyl monoethanolamine, diethylene glycolamine, and ketoimine in batches to the crosslinking mixture at 100-110℃, and keep the reaction at the temperature until the amine value is 30-50 mg KOH / g to form a heat-insulating material. S5. Add polyetheramine and polyether polyol to the insulation material, stir well to form a mixture; S6. Cool the mixture to 65-75℃, add organic glacial acetic acid to adjust the pH to 5.5-6.5, and add deionized water dropwise under high-speed shearing to perform reverse emulsification, thus completing the preparation.

[0016] By adopting the above technical solution, a blocked crosslinking agent is first prepared separately to avoid side reactions caused by direct contact between toluene diisocyanate and components containing active hydrogen, thus ensuring the purity and stability of the crosslinking agent. The epoxy equivalent of E-51 epoxy resin is controlled through chain extension reaction to ensure that the resin molecular weight is appropriate. The blocked crosslinking agent is physically mixed with epoxy premix to ensure that the crosslinking agent is uniformly dispersed in the resin. Amination reagents are added in batches and the amine value is controlled to meet the requirements of water dispersibility without excessive hydrophilicity affecting the water resistance of the coating. Polyetheramine and polyether polyol are added for physical toughening. By using the reverse emulsification method and controlling the pH value and shear conditions, a water-in-oil emulsion with uniform particle size and stable storage is obtained.

[0017] Preferably, in step S2, the chain extension reaction takes 2-2.5 hours; in step S4, the heat preservation reaction takes 2.0-2.5 hours.

[0018] By adopting the above technical solutions, the chain extension reaction and the amination ring-opening reaction can control the epoxy equivalent and amine value within the target range, ensuring the batch stability and performance consistency of the reaction products.

[0019] Preferably, in step S3, the stirring speed is 300-500 rpm and the time is 30-40 minutes. After the cross-linked mixture is formed, glycidyl methacrylate and photoinitiator are added, and the mixture is reacted at 90-100°C for 1-1.5 hours to graft the acrylate groups in glycidyl methacrylate onto the epoxy-amine resin molecular chain of the premix.

[0020] By adopting the above technical solution, after the crosslinking agent and resin are mixed evenly, glycidyl methacrylate is further added for photosensitive grafting modification, so that the epoxy group of glycidyl methacrylate reacts fully with the active hydroxyl or amine group on the resin chain, and the photosensitive group of acrylate is quantitatively grafted onto the resin molecular chain.

[0021] Preferably, in step S5, before adding polyetheramine and polyether polyol, the modified graphene predispersant is added to the insulation material, and then polyetheramine and polyether polyol are added. The stirring speed is 300-500 rpm and the stirring time is 30-60 minutes.

[0022] By adopting the above technical solution, the modified graphene pre-dispersion is added to the insulation material before adding the toughening component, so that the graphene nanosheets are fully wetted in the resin matrix. Then, polyetheramine and polyether polyol are added for blending, which ensures the synergistic dispersion effect of graphene, polyetheramine and polyether polyol in the resin and avoids agglomeration or uneven dispersion due to excessive local concentration.

[0023] Preferably, in step S6, the cooling rate is 1-3℃ / min, the drop rate of the deionized water is 5-10mL / min, and the shear rate is 1000-1500rpm.

[0024] By adopting the above technical solutions, the cooling rate is controlled to avoid local overheating or resin precipitation caused by excessively rapid cooling, ensuring that the mixture is in a suitable temperature and viscosity state before emulsification; controlling the deionized water droplet acceleration rate and shear rate can make the phase inversion process proceed smoothly, thereby obtaining a stable emulsion with uniform particle size and narrow distribution.

[0025] In summary, this application has the following beneficial effects: 1. This application uses E-51 epoxy resin, bisphenol A, and bisphenol A polyoxyethylene ether as the matrix framework. After chain extension catalyzed by benzylamine, an epoxy equivalent prepolymer is obtained. Simultaneously, toluene diisocyanate is reacted with diethylene glycol butyl ether, diethylene glycol ethyl ether, and trimethylolpropane polyoxyethylene ether to prepare a blocked crosslinking agent. This agent is stable at room temperature and deblocks and participates in crosslinking during the high-temperature curing stage, forming a microphase separation structure with the epoxy-amine resin system. This achieves a uniform internal matting effect without the addition of external matting powder, avoiding the problems caused by density differences in matting powder. The storage sedimentation problem is eliminated; at the same time, the crosslinking agent is dispersed in the resin at the molecular level, which will not block the electrophoretic deposition channels or interfere with the electric field distribution, thus maintaining high penetration. This ensures that the coating thickness and gloss in the interior and recessed areas of the workpiece are consistent with the surface. Methyl ethanolamine, diethylene glycolamine and ketimine synergistic amination imparts cationic water dispersibility to the resin and introduces latent curing crosslinking points. Polyetheramine and polyether polyol provide flexible segments to enhance adhesion and toughness, thus achieving a balance between storage stability, coating gloss uniformity, penetration and coating mechanical properties.

[0026] 2. This application uses a photoinitiator and glycidyl methacrylate to photosensitively graft the resin. After electrophoretic film formation, it is first pre-cured with ultraviolet light and then heat-cured to form a dual curing process of ultraviolet pre-curing and heat curing. The ultraviolet light initiates the rapid polymerization of acrylate groups, which enables the coating surface to cross-link and solidify in advance, reducing coating sagging and micro-defect formation during the heat curing process, making the coating more dense and uniform. Thus, without changing the basic gloss and adhesion of the coating, the salt spray resistance of the coating is further improved.

[0027] 3. This application uses a modified graphene predispersant prepared by predispersing graphene oxide with a portion of polyetheramine. The non-covalent modification of graphene oxide by polyetheramine improves the dispersion stability of graphene in the aqueous resin system. After the graphene nanosheets are uniformly dispersed in the coating, they form a physical shielding network, which prolongs the penetration path of corrosive media. Thus, without affecting the storage stability of the emulsion and the matte appearance of the coating, the salt spray resistance of the coating is further improved. Attached Figure Description

[0028] Figure 1 This is a flowchart of the preparation method of the bisphenol A epoxy-polyetheramine composite matte photophoretic emulsion provided in this application. Detailed Implementation

[0029] The present application will be further described in detail below with reference to the accompanying drawings and embodiments.

[0030] Technical Concept: Electrophoretic coating is a coating method that uses an external electric field to deposit charged resin particles suspended in water onto the surface of a workpiece. Cathodic electrophoretic coatings use epoxy resin as a matrix, which is amination modified to give the resin cationic properties. However, existing matte electrophoretic paint emulsions mostly achieve a matte effect by adding matting powder. Due to the large density difference between the matting powder and the resin matrix, it is prone to gravity sedimentation during emulsion storage. At the same time, the introduction of matting powder reduces the penetration of the electrophoretic coating, resulting in a thinner coating and higher gloss in the interior or recessed areas of the workpiece, causing unstable coating gloss.

[0031] Based on this, this application reacts toluene diisocyanate with mixed alcohol ethers to prepare a blocked crosslinking agent, which is then compounded with epoxy resin that has undergone chain extension and amination modification. This enables the formation of a microphase separation structure during the thermosetting stage, thereby obtaining a uniform and controllable matte coating without the addition of matting powder, while avoiding the sedimentation and reduced penetration caused by matting powder. Furthermore, the amination system is optimized by using methyl monoethanolamine, diethylene glycolamine, and ketimine for synergistic amination, introducing latent curing crosslinking points to enhance the crosslinking density of the coating. At the same time, polyetheramine and polyether polyol are added to provide flexible segments to improve the adhesion and toughness of the coating. In addition, photosensitive groups are grafted onto glycidyl methacrylate and combined with UV pre-curing to reduce micro-defects during the thermosetting process, and a physical shielding network is formed by polyetheramine-modified graphene oxide to further improve salt spray resistance. This solves the problem that existing matte photophoretic emulsions tend to result in thinner coatings and higher gloss in the interior or recessed areas of the workpiece, causing unstable coating gloss.

[0032] Unless otherwise specified, all experimental methods used below are conventional methods. All materials, reagents, methods, and instruments used, unless otherwise specified, are conventional materials, reagents, methods, and instruments in this field, which can be obtained commercially or prepared according to literature methods by those skilled in the art.

[0033] Raw material source: E-51 epoxy resin: epoxy equivalent 184-194 g / eq, industrial grade, purchased from Nantong Xingchen Synthetic Materials Co., Ltd.

[0034] Bisphenol A: Purity ≥99%, industrial grade, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0035] Bisphenol A polyoxyethylene ether: hydroxyl value 150-200 mg KOH / g, industrial grade, purchased from Haian Petrochemical Plant, Jiangsu Province.

[0036] Benzylamine: Purity ≥98%, industrial grade, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0037] Methylethanolamine: purity ≥99%, industrial grade, purchased from Dow Chemical Company.

[0038] Diethylene glycolamine: purity ≥98%, industrial grade, purchased from Huntsman Corporation, USA.

[0039] Ketoimine: Amine value 200-300 mg KOH / g, industrial grade, purchased from Shanghai Hanhong Technology Co., Ltd.

[0040] Polyetheramine: molecular weight 1500-2500, amine value 40-60 mg KOH / g, industrial grade, purchased from Huntsman.

[0041] Polyether polyols: molecular weight 800-1200, hydroxyl value 100-120 mg KOH / g, industrial grade, purchased from Shandong Lanxing Dongda Co., Ltd.

[0042] Toluene diisocyanate: a mixture of 2,4- and 2,6- isomers, purity ≥99.5%, industrial grade, purchased from BASF.

[0043] Diethylene glycol butyl ether: purity ≥99%, industrial grade, purchased from Dow Chemical Company.

[0044] Diethylene glycol ethyl ether: purity ≥99%, industrial grade, purchased from Dow Chemical Company.

[0045] Trimethylolpropane polyoxyethylene ether: hydroxyl value 150-200 mg KOH / g, industrial grade, purchased from Haian Petrochemical Plant, Jiangsu Province.

[0046] Methyl isobutyl ketone: purity ≥99%, industrial grade, purchased from Shanghai Lingfeng Chemical Reagent Co., Ltd.

[0047] Organic glacial acetic acid: purity ≥99.5%, industrial grade, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0048] Deionized water: conductivity ≤5 μS / cm, prepared in the laboratory.

[0049] Photoinitiator: 2-hydroxy-2-methyl-1-phenylpropanone, purity ≥99%, industrial grade, purchased from Tianjin Jiuri New Materials Co., Ltd.

[0050] Glycidyl methacrylate: purity ≥97%, industrial grade, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0051] Graphene oxide: 1-5 layers, sheet diameter 0.5-5 μm, oxygen content 30-40%, industrial grade, purchased from Suzhou CarbonFeng Graphene Technology Co., Ltd.

[0052] Preparation Example 1: Preparation of Modified Graphene Predispersion Take 0.3-0.8 parts by weight of graphene oxide, mix it with 50-70% of the total amount of polyetheramine and 5-10 parts by weight of deionized water, place it in an ultrasonic dispersion device, use an ultrasonic frequency of 20-40 kHz and a power of 200-500 W, disperse for 30-60 minutes to obtain a stable modified graphene predispersant. Specific preparation of Example 1: Take 0.55 g of graphene oxide, mix it with 0.9 g of polyetheramine and 7.5 g of deionized water, and disperse it for 45 minutes at an ultrasonic frequency of 40 kHz and a power of 300 W to obtain a modified graphene predispersant. Specific preparation of Example 2: Take 0.8 g of graphene oxide, mix it with 1.26 g of polyetheramine and 10 g of deionized water, and disperse it for 60 minutes at an ultrasonic frequency of 40 kHz and a power of 400 W to obtain a modified graphene predispersant. Specific preparation of Example 3: Take 0.3 g of graphene oxide, mix it with 0.6 g of polyetheramine and 5 g of deionized water, and disperse it for 30 minutes at an ultrasonic frequency of 40 kHz and a power of 250 W to obtain a modified graphene predispersant.

[0053] To better understand the above technical solutions, the technical solutions of the present invention will be clearly and completely described below in conjunction with embodiments.

[0054] The following is a further description with reference to the embodiments: Example 1: Please refer to the appendix Figure 1 Bisphenol A epoxy-polyetheramine composite matte photocoating emulsion comprises the following raw materials in parts by weight: 35 parts E-51 epoxy resin, 9 parts bisphenol A, 10 parts bisphenol A polyoxyethylene ether, 0.1 parts benzylamine, 3 parts methyl monoethanolamine, 1 part diethylene glycolamine, 3 parts ketimine, 1.5 parts polyetheramine, 1.5 parts polyether polyol, 15 parts toluene diisocyanate, 9 parts diethylene glycol butyl ether, 11 parts diethylene glycol ethyl ether, 2 parts trimethylolpropane polyoxyethylene ether, 2 parts methyl isobutyl ketone, 2 parts organic glacial acetic acid, and 150 parts deionized water.

[0055] It also includes 0.75 parts by weight of photoinitiator and 2 parts by weight of glycidyl methacrylate.

[0056] It also includes a modified graphene predispersant, which is prepared by ultrasonically dispersing 0.55 parts by weight of graphene oxide, 60% of the total amount of polyetheramine, and 7.5 parts by weight of deionized water for 45 minutes.

[0057] The amine value of ketimine is 250 mg KOH / g.

[0058] The molecular weight of polyetheramine is 2000 and the amine value is 50 mg KOH / g. The molecular weight of polyether polyol is 1000 and the hydroxyl value is 110 mg KOH / g.

[0059] A method for preparing a bisphenol A epoxy-polyetheramine composite matte photocoating emulsion, applicable to the above-mentioned bisphenol A epoxy-polyetheramine composite matte photocoating emulsion, includes the following steps: S1. Under nitrogen protection, toluene diisocyanate, diethylene glycol butyl ether, diethylene glycol ethyl ether, and trimethylolpropane polyoxyethylene ether are reacted at 77.5°C until the isocyanate content is 0 to obtain a blocked crosslinking agent. S2. E-51 epoxy resin, bisphenol A, and bisphenol A polyoxyethylene ether are added to benzylamine at 120°C to carry out chain extension reaction until the epoxy equivalent reaches 1200g / eq, forming a premix. The chain extension reaction took 2.25 hours. S3. Cool the premix to 95°C, add methyl isobutyl ketone and a blocking crosslinking agent, stir and mix to form a crosslinking mixture; The stirring speed was 400 rpm and the time was 35 minutes. After the cross-linked mixture was formed, glycidyl methacrylate and photoinitiator were added, and the mixture was reacted at 95°C for 1.25 hours to graft the acrylate groups in glycidyl methacrylate onto the epoxy-amine resin molecular chain of the premix. S4. Add methyl monoethanolamine, diethylene glycolamine, and ketoimine in batches to the crosslinking mixture at 105℃, and keep the reaction at this temperature until the amine value is 40 mg KOH / g to form a heat-insulating material. The heat preservation reaction time is 2.25 hours; S5. Add polyetheramine and polyether polyol to the insulation material, stir well to form a mixture; Before adding polyetheramine and polyether polyol, the modified graphene predispersant is added to the insulation material, and then polyetheramine and polyether polyol are added. The mixture is stirred at 400 rpm for 45 minutes.

[0060] S6. Cool the mixture to 70°C, add organic glacial acetic acid to adjust the pH to 6, and add deionized water dropwise under high-speed shearing to perform reverse emulsification and complete the preparation. The cooling rate was 2℃ / min, the drop rate of deionized water was 7.5mL / min, and the shear rate was 1250rpm.

[0061] Example 2: This example differs from Example 1 above in that: The bisphenol A epoxy-polyetheramine composite matte photocoating emulsion comprises the following raw materials in parts by weight: 40 parts E-51 epoxy resin, 10 parts bisphenol A, 11 parts bisphenol A polyoxyethylene ether, 0.12 parts benzylamine, 3.5 parts methyl ethanolamine, 1.2 parts diethylene glycolamine, 3.5 parts ketimine, 1.8 parts polyetheramine, 1.8 parts polyether polyol, 16 parts toluene diisocyanate, 10 parts diethylene glycol butyl ether, 12 parts diethylene glycol ethyl ether, 2.2 parts trimethylolpropane polyoxyethylene ether, 2.5 parts methyl isobutyl ketone, 2.5 parts organic glacial acetic acid, and 160 parts deionized water.

[0062] It also includes 1 part by weight of photoinitiator and 2.5 parts by weight of glycidyl methacrylate.

[0063] It also includes a modified graphene predispersant, which is prepared by ultrasonically dispersing 0.8 parts by weight of graphene oxide, 70% of the total amount of polyetheramine, and 10 parts by weight of deionized water for 60 minutes.

[0064] The amine value of ketimine is 300 mg KOH / g.

[0065] The molecular weight of polyetheramine is 2500 and the amine value is 60 mg KOH / g. The molecular weight of polyether polyol is 1200 and the hydroxyl value is 120 mg KOH / g.

[0066] A method for preparing a bisphenol A epoxy-polyetheramine composite matte photocoating emulsion, applicable to the above-mentioned bisphenol A epoxy-polyetheramine composite matte photocoating emulsion, includes the following steps: S1. Under nitrogen protection, toluene diisocyanate, diethylene glycol butyl ether, diethylene glycol ethyl ether, and trimethylolpropane polyoxyethylene ether are reacted at 85°C until the isocyanate content is 0 to obtain a blocked crosslinking agent. S2. E-51 epoxy resin, bisphenol A, and bisphenol A polyoxyethylene ether are added to benzylamine at 130°C to carry out chain extension reaction until the epoxy equivalent reaches 1500g / eq, forming a premix. The chain extension reaction took 2.5 hours. S3. Cool the premix to 100°C, add methyl isobutyl ketone and a blocking crosslinking agent, stir and mix to form a crosslinking mixture; The stirring speed was 500 rpm and the time was 40 minutes. After the cross-linked mixture was formed, glycidyl methacrylate and photoinitiator were added, and the mixture was reacted at 100°C for 1.5 hours to graft the acrylate groups in glycidyl methacrylate onto the epoxy-amine resin molecular chain of the premix. S4. Add methyl monoethanolamine, diethylene glycolamine, and ketoimine in batches to the crosslinked mixture at 110℃, and keep the reaction at this temperature until the amine value is 50 mg KOH / g to form a heat-insulating material. The heat preservation reaction time is 2.5 hours; S5. Add polyetheramine and polyether polyol to the insulation material, stir well to form a mixture; Before adding polyetheramine and polyether polyol, the modified graphene predispersant is added to the insulation material, and then polyetheramine and polyether polyol are added. The mixture is stirred at 500 rpm for 60 minutes.

[0067] S6. Cool the mixture to 75°C, add organic glacial acetic acid to adjust the pH to 6.5, and add deionized water dropwise under high-speed shearing to perform reverse emulsification and complete the preparation. The cooling rate was 3℃ / min, the drop rate of deionized water was 10mL / min, and the shear rate was 1500rpm.

[0068] Example 3: This example differs from Example 1 above in that: The bisphenol A epoxy-polyetheramine composite matte photocoating emulsion comprises the following raw materials in parts by weight: 30 parts E-51 epoxy resin, 8 parts bisphenol A, 9 parts bisphenol A polyoxyethylene ether, 0.08 parts benzylamine, 2.5 parts methyl ethanolamine, 0.8 parts diethylene glycolamine, 2.5 parts ketimine, 1.2 parts polyetheramine, 1.2 parts polyether polyol, 14 parts toluene diisocyanate, 8 parts diethylene glycol butyl ether, 10 parts diethylene glycol ethyl ether, 1.8 parts trimethylolpropane polyoxyethylene ether, 1.5 parts methyl isobutyl ketone, 1.5 parts organic glacial acetic acid, and 140 parts deionized water.

[0069] It also includes 0.5 parts by weight of photoinitiator and 1.5 parts by weight of glycidyl methacrylate.

[0070] It also includes a modified graphene predispersant, which is prepared by ultrasonically dispersing 0.3 parts by weight of graphene oxide, 50% of the total amount of polyetheramine, and 5 parts by weight of deionized water for 30 minutes.

[0071] The amine value of ketimine is 200 mg KOH / g.

[0072] The molecular weight of polyetheramine is 1500 and the amine value is 40 mg KOH / g. The molecular weight of polyether polyol is 800 and the hydroxyl value is 100 mg KOH / g.

[0073] A method for preparing a bisphenol A epoxy-polyetheramine composite matte photocoating emulsion, applicable to the above-mentioned bisphenol A epoxy-polyetheramine composite matte photocoating emulsion, includes the following steps: S1. Under nitrogen protection, toluene diisocyanate, diethylene glycol butyl ether, diethylene glycol ethyl ether, and trimethylolpropane polyoxyethylene ether are reacted at 70°C until the isocyanate content is 0 to obtain a blocked crosslinking agent. S2. E-51 epoxy resin, bisphenol A, and bisphenol A polyoxyethylene ether are added to benzylamine at 110°C to carry out chain extension reaction until the epoxy equivalent reaches 900g / eq, forming a premix. The chain extension reaction takes 2 hours. S3. Cool the premix to 90°C, add methyl isobutyl ketone and a blocking crosslinking agent, stir and mix to form a crosslinking mixture; The stirring speed was 300 rpm and the time was 30 minutes. After the cross-linked mixture was formed, glycidyl methacrylate and photoinitiator were added, and the mixture was reacted at 90°C for 1 hour to graft the acrylate groups in glycidyl methacrylate onto the epoxy-amine resin molecular chain of the premix. S4. Add methyl monoethanolamine, diethylene glycolamine, and ketoimine in batches to the crosslinking mixture at 100℃, and keep the reaction at this temperature until the amine value is 30 mg KOH / g to form a heat-insulating material. The heat preservation reaction time is 2 hours; S5. Add polyetheramine and polyether polyol to the insulation material, stir well to form a mixture; Before adding polyetheramine and polyether polyol, the modified graphene predispersant is added to the insulation material, and then polyetheramine and polyether polyol are added. The mixture is stirred at 300 rpm for 30 minutes.

[0074] S6. Cool the mixture to 65°C, add organic glacial acetic acid to adjust the pH to 5.5, and add deionized water dropwise under high-speed shearing to perform reverse emulsification and complete the preparation. The cooling rate was 1℃ / min, the drop rate of deionized water was 5mL / min, and the shear rate was 1000rpm.

[0075] Comparative Example 1: A matte photophoretic paint emulsion, prepared by the following method: By weight, 35 parts of E-51 epoxy resin and 9 parts of bisphenol A were added to benzylamine at 120℃ for chain extension reaction until the epoxy equivalent reached 1200 g / eq; the temperature was lowered to 100℃ and 2 parts of methyl isobutyl ketone, 3 parts of methyl ethanolamine, and 1 part of diethylene glycolamine were added and reacted at 105℃ until the amine value reached 40 mg KOH / g; 20 parts of commercially available blocked isocyanate crosslinking agent were added and stirred evenly; the temperature was lowered to 70℃ and 2 parts of organic glacial acetic acid were added to adjust the pH to 6.5; under high-speed shearing, 150 parts of deionized water were added dropwise for reverse emulsification to obtain the base emulsion; the base emulsion was mixed with silica matting powder at a mass ratio of 100:3 and dispersed at high speed for 30 minutes to obtain the matte photocoating emulsion.

[0076] Comparative Example 2: This comparative example differs from Example 1 above in that: Without adding toluene diisocyanate, diethylene glycol butyl ether, diethylene glycol ethyl ether, or trimethylolpropane polyoxyethylene ether, i.e., without preparing or adding any blocking crosslinking agent, the rest is the same as in Example 1.

[0077] Comparative Example 3: This comparative example differs from Example 1 above in that: No ketimine was added; otherwise, it was the same as in Example 1.

[0078] Comparative Example 4: This comparative example differs from Example 1 above in that: No polyetheramines and polyether polyols were added; otherwise, it was the same as in Example 1.

[0079] Comparative Example 5: This comparative example differs from Example 1 above in that: The amount of toluene diisocyanate used was 25 parts, and the amounts of diethylene glycol butyl ether, diethylene glycol ethyl ether, and trimethylolpropane polyoxyethylene ether were adjusted proportionally to 15 parts, 18 parts, and 3.5 parts, respectively. The rest was the same as in Example 1.

[0080] Comparative Example 6: This comparative example differs from Example 1 above in that: No modified graphene predispersant was added; otherwise, it was the same as in Example 1.

[0081] Comparative Example 7: This comparative example differs from Example 1 above in that: No photoinitiator or glycidyl methacrylate was added, i.e., no UV photosensitive grafting modification was performed; otherwise, it was the same as in Example 1.

[0082] Performance testing: Storage stability: Refer to GB / T 6753.3-1986, seal the emulsion in a glass bottle and store it at room temperature for 6 months, and observe whether there is any stratification, sedimentation or thickening; if there is no stratification, sedimentation or thickening after 6 months, it is qualified; otherwise, it is unqualified. Solid content: Refer to GB / T 1725-2007, weigh 1 to 2 grams of emulsion, bake at 120℃ for 1 hour, weigh the residue, and calculate the percentage of solid content; Particle size: The average particle size was measured at 25°C by diluting the emulsion to 0.1 to 0.5 g / L using a dynamic light scattering particle size analyzer. The unit is nanometers. Gloss: Referring to GB / T 9754-2007, the emulsion was prepared into an electrophoresis bath solution with a solid content of 11%, a pH value of 6.0, and a temperature of 30℃. Phosphated steel plate was used as the cathode, and stainless steel plate as the anode. Electrophoretic coating was performed at a voltage of 150 volts and a time of 2.5 minutes. After coating, the workpiece was removed, rinsed with deionized water, and then baked at 170℃ for 25 minutes for curing. The gloss of the coating was measured using a 60-degree gloss meter, with 5 points measured for each sample and the average value taken. Throwing power: The method is determined according to the tube method in HG / T 3952-2007 standard. The steel tube method is used. After coating, the coating thickness on the inner wall of the steel tube is measured. The throwing power is expressed as the percentage of the inner wall thickness to the outer wall thickness. The higher the value, the better the throwing power. Adhesion: Refer to GB / T 9286-1998, cross-cut test, cross-cut spacing is 1 mm, use 3M tape to peel off, rated from 0 to 5, with 0 being the best; Pencil hardness: Refer to GB / T 6739-2006, use Mitsubishi pencils, load capacity 750 grams; Salt spray resistance: Referring to GB / T 1771-2007, the coated steel plate was marked with a cross and placed in a salt spray chamber. A 5% sodium chloride solution was used at a temperature of 35℃ for continuous spraying. The width of rust spread on one side of the marked area was recorded after 1000 hours. The smaller the width, the better the salt spray resistance. The test results are shown in Table 1.

[0083] Table 1

[0084] As can be seen from Examples 1 to 3 and Comparative Examples 1 to 7, and Table 1, this application uses a toluene diisocyanate-based blocked crosslinking agent to construct an internal matte system. The microphase separation structure of epoxy resin and polyetheramine achieves uniform matte finish without the need for external matting powder, thus improving the storage stability of the emulsion. At the same time, it eliminates the interference of matting powder particles on the electrophoretic deposition electric field, resulting in stable and controllable coating gloss and maintaining a high level of penetration. In addition, after the blocked crosslinking agent is unblocked during the thermosetting stage, it fully crosslinks with the hydroxyl and amine groups on the resin to form a dense coating network. Combined with ketimine as a latent curing agent to supplement the crosslinking point density, and the toughening effect of flexible segments provided by polyetheramine and polyether polyol, the coating achieves excellent adhesion, suitable hardness, and excellent salt spray resistance while maintaining low gloss.

[0085] As can be seen from Examples 1 to 3 and Comparative Example 1, and Table 1, this application uses a toluene diisocyanate-based blocked crosslinking agent to construct an internal matting system, which can obtain a stable low-gloss coating without the need for external matting powder. This internal matting structure achieves light scattering through the microphase separation of the crosslinking agent and the epoxy amine resin, avoiding gloss fluctuations and decreased penetration caused by matting powder sedimentation. At the same time, the uniform distribution of the crosslinking agent improves the coating density and salt spray resistance.

[0086] Combining Example 1 and Comparative Example 2 with Table 1, it can be seen that the closed crosslinking agent can form an internal matte structure and ensure the crosslinking density of the coating. During the thermosetting stage, the crosslinking agent de-encapsulates and releases isocyanate groups to react with the hydroxyl and amine groups on the resin. Without this component, the coating cannot form a sufficient microphase separation structure, resulting in higher gloss, lower hardness, and significantly reduced corrosion resistance.

[0087] As can be seen from Example 1 and Comparative Example 3 and Table 1, ketimine, as a latent curing agent, can play a role in maintaining the mechanical properties and corrosion resistance of the coating. During the thermosetting process, ketimine hydrolyzes to generate primary amines, which participate in the crosslinking reaction of epoxy groups and isocyanate groups to supplement the crosslinking point density. When ketimine is lacking, the crosslinking network of the coating is incomplete, and the adhesion, hardness and salt spray resistance are significantly deteriorated.

[0088] As can be seen from Example 1 and Comparative Example 4, and Table 1, polyetheramine and polyether polyol, as toughening components, can improve the flexibility and interfacial adhesion of the coating. This component reduces the internal stress of the coating and enhances the adhesion between the coating and the metal substrate by introducing flexible segments. Without this component, the adhesion decreases and the coating becomes more brittle, and the salt spray resistance is also affected.

[0089] As can be seen from Example 1 and Comparative Example 5 and Table 1, the amount of toluene diisocyanate-based crosslinking agent needs to be controlled within a reasonable range. Excessive use will lead to over-crosslinking of the system, decreased emulsion storage stability, and damage to the compatibility between the crosslinking agent and the resin, resulting in uneven internal matte structure, increased gloss and reduced penetration.

[0090] As can be seen from Example 1 and Comparative Example 6, and Table 1, the addition of modified graphene predispersant can further enhance the physical shielding effect of the coating. The graphene nanosheets are uniformly dispersed in the coating to form a physical shielding layer, which physically blocks the corrosive medium and increases its permeation resistance, thereby improving the salt spray resistance without affecting the basic storage stability and matte appearance of the emulsion.

[0091] As can be seen from Example 1 and Comparative Example 7, and Table 1, the dual curing process of UV pre-curing and thermal curing can optimize the surface shaping effect of the coating. UV light initiates the rapid polymerization of acrylate groups, causing the coating surface to cross-link in advance, reducing sagging and micro-defect formation during thermal curing, thereby further improving salt spray resistance without changing the basic gloss and adhesion of the coating.

[0092] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A bisphenol A epoxy-polyetheramine composite matte photocoagulation emulsion, characterized in that, The raw materials include the following parts by weight: 30-40 parts of E-51 epoxy resin, 8-10 parts of bisphenol A, 9-11 parts of bisphenol A polyoxyethylene ether, 0.08-0.12 parts of benzylamine, 2.5-3.5 parts of methyl monoethanolamine, 0.8-1.2 parts of diethylene glycolamine, 2.5-3.5 parts of ketimine, 1.2-1.8 parts of polyetheramine, 1.2-1.8 parts of polyether polyol, 14-16 parts of toluene diisocyanate, 8-10 parts of diethylene glycol butyl ether, 10-12 parts of diethylene glycol ethyl ether, 1.8-2.2 parts of trimethylolpropane polyoxyethylene ether, 1.5-2.5 parts of methyl isobutyl ketone, 1.5-2.5 parts of organic glacial acetic acid, and 140-160 parts of deionized water.

2. The bisphenol A epoxy-polyetheramine composite matte photophoretic emulsion according to claim 1, characterized in that: It also includes 0.5-1 parts by weight of photoinitiator and 1.5-2.5 parts by weight of glycidyl methacrylate.

3. The bisphenol A epoxy-polyetheramine composite matte photocoating emulsion according to claim 1, characterized in that: It also includes a modified graphene predispersant, which is prepared by ultrasonically dispersing 0.3-0.8 parts by weight of graphene oxide, 50-70% of polyetheramine, and 5-10 parts by weight of deionized water for 30-60 minutes.

4. The bisphenol A epoxy-polyetheramine composite matte photocoating emulsion according to claim 1, characterized in that: The amine value of the ketimine is 200-300 mg KOH / g.

5. The bisphenol A epoxy-polyetheramine composite matte photocoating emulsion according to claim 1, characterized in that: The polyether amine has a molecular weight of 1500-2500 and an amine value of 40-60 mg KOH / g, and the polyether polyol has a molecular weight of 800-1200 and a hydroxyl value of 100-120 mg KOH / g.

6. A method for preparing a bisphenol A epoxy-polyetheramine composite matte photophoretic emulsion, characterized in that: The bisphenol A epoxy-polyetheramine composite matte photocoating emulsion according to any one of claims 1-5 comprises the following steps: S1. Under nitrogen protection, toluene diisocyanate, diethylene glycol butyl ether, diethylene glycol ethyl ether, and trimethylolpropane polyoxyethylene ether are reacted at 70-85℃ until the isocyanate content is 0 to obtain a blocked crosslinking agent. S2. Add benzylamine to E-51 epoxy resin, bisphenol A, and bisphenol A polyoxyethylene ether at 110-130℃ to carry out chain extension reaction until the epoxy equivalent reaches 900-1500g / eq, forming a premix. S3. Cool the premix to 90-100℃, add methyl isobutyl ketone and blocking crosslinking agent, stir and mix to form a crosslinking mixture; S4. Add methyl monoethanolamine, diethylene glycolamine, and ketoimine in batches to the crosslinking mixture at 100-110℃, and keep the reaction at the temperature until the amine value is 30-50 mg KOH / g to form a heat-insulating material. S5. Add polyetheramine and polyether polyol to the insulation material, stir well to form a mixture; S6. Cool the mixture to 65-75℃, add organic glacial acetic acid to adjust the pH to 5.5-6.5, and add deionized water dropwise under high-speed shearing to perform reverse emulsification, thus completing the preparation.

7. The method for preparing the bisphenol A epoxy-polyetheramine composite matte photophoretic emulsion according to claim 6, characterized in that: In step S2, the chain extension reaction takes 2-2.5 hours; in step S4, the heat preservation reaction takes 2.0-2.5 hours.

8. The method for preparing the bisphenol A epoxy-polyetheramine composite matte photophoretic emulsion according to claim 6, characterized in that: In step S3, the stirring speed is 300-500 rpm and the time is 30-40 minutes. After the cross-linked mixture is formed, glycidyl methacrylate and photoinitiator are added, and the mixture is reacted at 90-100℃ for 1-1.5 hours to graft the acrylate groups in glycidyl methacrylate onto the epoxy-amine resin molecular chain of the premix.

9. The method for preparing the bisphenol A epoxy-polyetheramine composite matte photophoretic emulsion according to claim 6, characterized in that: In step S5, before adding polyetheramine and polyether polyol, the modified graphene predispersant is added to the insulation material, and then polyetheramine and polyether polyol are added. The stirring speed is 300-500 rpm and the stirring time is 30-60 minutes.

10. The method for preparing the bisphenol A epoxy-polyetheramine composite matte photophoretic emulsion according to claim 6, characterized in that: In step S6, the cooling rate is 1-3℃ / min, the drop rate of the deionized water is 5-10mL / min, and the shear rate is 1000-1500rpm.

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