Low temperature curing high throw power cathodic electrophoretic coating, its preparation method and application

Abstract

The application discloses a low-temperature curing high-wetting cathodic electrophoretic paint in the field of automobile coating materials and a preparation method and application thereof. The paint is composed of various components such as epoxy resin, fluorosilicon copolymer type epoxy modifier and polyamine base siloxane-acrylic hybrid, and the performance is improved through the synergistic effect of two new modifiers. The fluorosilicon copolymer type epoxy modifier takes bisphenol A epoxy resin as a skeleton, introduces fluorine-containing alkyl and siloxane groups, and is prepared through ultraviolet light reaction to reduce surface energy and promote low-temperature crosslinking. The polyamine base siloxane-acrylic hybrid takes siloxane as a core, is bridged with isocyanate and polyamine base, and is enhanced in crosslinking density and water solubility. During the preparation of the paint, the two modifiers are mixed with epoxy resin, solvent and the like, and the paint is prepared through dispersion and dilution. The paint can be cured at low temperature, uniform thick film is obtained in the inner cavity of complex workpieces, the paint has excellent corrosion resistance and adhesion, and is suitable for efficient and environment-friendly coating of automobile bodies and parts.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of automobile coating materials, in particular to a low-temperature curing high-spread cathodic electrophoretic paint and a preparation method and application thereof. BACKGROUND

[0002] As one of the core technologies in the field of automobile coating, cathodic electrophoretic paint has long occupied the mainstream position of automobile body and parts coating due to its high spread, uniform film thickness and excellent corrosion resistance. Traditional cathodic electrophoretic paint needs to go through a high-temperature curing process in application, usually to complete the crosslinking reaction in a high-temperature environment. This process not only significantly increases the production energy consumption, but also easily causes thermal deformation of metal workpieces. Especially for complex automobile parts, thermal stress concentration may cause coating cracking or adhesion loss, limiting its further promotion in precision and lightweight automobile manufacturing.

[0003] The coating quality of complex workpieces is another key indicator to measure the performance of cathodic electrophoretic paint. Due to the complex structure and narrow inner cavity of automobile door hinges, wheel covers and other parts, the electric field distribution is uneven during the electrophoresis process, and the anion of the resin cannot effectively migrate to the inner cavity surface, resulting in an inner cavity film thickness generally less than 10 microns, which cannot form an effective protective barrier. Although the traditional technology attempts to improve the electrophoresis behavior by adding surfactants, excessive use will weaken the chemical adhesion between the resin and the metal substrate. Some modification methods can improve the spread, but it is difficult to simultaneously solve the contradiction between curing temperature and corrosion resistance, and the comprehensive performance of the coating is limited.

[0004] In view of the above problems, the industry focuses on the modification of cathodic electrophoretic paint, but the existing technology still has significant bottlenecks. As the main chain material of cathodic electrophoretic paint, epoxy resin needs to rely on high-activity modifiers for low-temperature crosslinking. Traditional modifiers are mostly designed with single functional groups (such as containing only fluorine or silicon elements), which are difficult to achieve multiple goals such as reducing surface energy to promote low-temperature curing, enhancing interface adhesion to improve spread, and improving corrosion resistance. In addition, the existing modification process often involves complex chemical reaction conditions or expensive raw materials, resulting in increased production cost of the paint, which is difficult to meet the needs of large-scale industrial application. Therefore, developing a new modified compound with low-temperature crosslinking activity, high spread promotion function and comprehensive corrosion resistance has become a key direction to break through the performance bottleneck of cathodic electrophoretic paint. SUMMARY

[0005] The present application relates to the technical field of automobile coating materials, in particular to a low-temperature curing high-spread cathodic electrophoretic paint and a preparation method and application thereof.

[0006] The present application achieves the above-mentioned purposes through the following technical solutions:

[0007] A low-temperature curing high-wet-solubility cathode electrophoretic paint, comprising the following raw materials in parts by weight:

[0008] epoxy resin: 500-600 parts by weight;

[0009] fluorosilicon copolymer type epoxy modifier: 100-150 parts by weight;

[0010] polyamine-based siloxane-acrylic hybrid: 50-80 parts by weight;

[0011] glycol butyl ether: 200-250 parts by weight;

[0012] dimethyl sulfoxide: 50-80 parts by weight;

[0013] titanium white: 150-200 parts by weight;

[0014] talc: 80-120 parts by weight;

[0015] organic bentonite: 20-30 parts by weight;

[0016] antifoaming agent: 3-5 parts by weight;

[0017] polyether-modified polydimethylsiloxane: 2-3 parts by weight;

[0018] deionized water: 200-250 parts by weight;

[0019] The preparation method of the fluorosilicon copolymer type epoxy modifier comprises the following steps: A1, dissolving bisphenol A epoxy resin in dimethylbenzene, and stirring and dissolving under heating to 120-122℃; sequentially adding perfluorooctyl acrylate and γ-glycidyl ether oxygen propyl trimethoxysilane; A2, adding 2,4,6-trimethylbenzoyl-diphenyl phosphine oxide and N,N-dimethyl aniline, and reacting under ultraviolet light irradiation under nitrogen protection; and performing vacuum distillation after the reaction is completed.

[0020] According to the preferred embodiment of the present application, the epoxy resin is purchased from Bluestar Chemical Co., Ltd., and the model is E-44 (bisphenol A type epoxy resin, epoxy value 0.44 eq / 100g).

[0021] According to the preferred embodiment of the present application, the bisphenol A epoxy resin is purchased from Balin Petrochemical Co., Ltd., and the model is E-20 (bisphenol A type epoxy resin, epoxy value 0.2 eq / 100g).

[0022] According to the preferred embodiment of the present application, the dimethylbenzene is purchased from Sinopec Shanghai Petrochemical Co., Ltd., and the model is AR grade industrial dimethylbenzene (purity ≥ 99%).

[0023] According to the preferred embodiment of the present application, the perfluorooctyl acrylate is purchased from Zhejiang Juhua Group Fluorine Chemical Co., Ltd., with model number FAC-8 (perfluorooctyl acrylate, carbon number C8).

[0024] According to the preferred embodiment of the present application, the γ-glycidoxypropyltrimethoxysilane is purchased from Hubei Wuda Silicone New Material Co., Ltd., with model number KH-560 (γ-glycidoxypropyltrimethoxysilane).

[0025] According to the preferred embodiment of the present application, the 2,4,6-trimethylbenzoyl-diphenyl phosphine oxide is purchased from Beijing Yingli Science and Technology Development Co., Ltd., with model number TPO-L (photoinitiator, purity ≥ 98%).

[0026] According to the preferred embodiment of the present application, the N,N-dimethylaniline is purchased from Jiangsu Feixing Chemical Co., Ltd., with model number DMA (N,N-dimethylaniline, purity ≥ 99%).

[0027] According to the preferred embodiment of the present application, the ethylene glycol butyl ether is purchased from Jiangsu Yida Chemical Co., Ltd., with model number BCS (ethylene glycol monobutyl ether, purity ≥ 99.5%).

[0028] According to the preferred embodiment of the present application, the dimethyl sulfoxide is purchased from Liaoning Aoke Chemical Co., Ltd., with model number DMSO (dimethyl sulfoxide, purity ≥ 99.9%).

[0029] According to the preferred embodiment of the present application, the titanium white powder is purchased from Longbai Group Co., Ltd., with model number BLR-996 (rutile titanium white powder, TiO2 content ≥ 96%).

[0030] According to the preferred embodiment of the present application, the talc powder is purchased from Liaoning Aihai Talc Co., Ltd., with model number AH-325 (talc powder, particle size ≤ 5 μm).

[0031] According to the preferred embodiment of the present application, the organic bentonite is purchased from Zhejiang Fenghong New Material Co., Ltd., with model number BENTON-38 (organically modified bentonite, gum price ≥ 70 mL / 15 g).

[0032] According to the preferred embodiment of the present application, the defoaming agent is purchased from Jiangsu Sixin Interface Agent Technology Co., Ltd., with model number SX-088 (water-based silicone defoaming agent, solid content ≥ 95%).

[0033] According to the preferred embodiment of the present application, the polyether-modified polydimethylsiloxane is purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., with model number PEG-2000 (polyether-modified polydimethylsiloxane, HLB value 8-10).

[0034] According to the preferred embodiment of the present application, the deionized water is purchased from the enterprise self-made deionized water (conductivity ≤ 10 μS / cm, metal ion content ≤ 1 ppb).

[0035] In the present application, the synthesis of fluorosilicone copolymer type epoxy modifier takes bisphenol A epoxy resin as the starting material. First, the solvent is dissolved to form a uniform system, which lays the foundation for the subsequent introduction of functional groups. The epoxy group (-CH(O)CH-) on the molecular chain of bisphenol A epoxy resin has high reactivity and can copolymerize with fluorine-containing monomers and silane groups under elevated temperature conditions. The double bond (-C=C-) in perfluorooctyl acrylate is activated under ultraviolet light initiation and forms a covalent bond with the ring-opening reaction of the epoxy group, introducing a long-chain fluorocarbon structure (-C6F 13 ) into the epoxy resin skeleton; at the same time, the siloxane group (-Si-O-Si-) of γ-glycidyl ether oxypropyl trimethoxysilane is hydrolyzed to generate hydroxyl (-OH) and condenses with the epoxy group to form a stable siloxane bond (-Si-O-C-). The nitrogen protection environment avoids the quenching of oxygen on the free radical reaction, and the photoinitiator (2,4,6-trimethylbenzoyl-diphenyl phosphine oxide) decomposes to generate free radicals after absorbing ultraviolet light energy, accelerating the addition reaction of double bond and epoxy group. After the reaction is completed, the solvent is removed by reduced pressure distillation to obtain a copolymer type epoxy modifier containing fluorocarbon chain and siloxane segment. The long fluorocarbon chain of the modifier gives the coating low surface energy characteristics, reduces the resistance of resin particles to the metal surface; the siloxane segment reduces the activation energy required for curing through the hydrogen bonding of the hydroxyl group with the epoxy group, creating conditions for low temperature curing.

[0036] According to the preferred embodiment of the present application, in step A1, the mass ratio of bisphenol A epoxy resin to xylene is 1: (2-2.2).

[0037] According to the preferred embodiment of the present application, in step A2, the amount of 2,4,6-trimethylbenzoyl-diphenyl phosphine oxide is 2-4% of the mass of the epoxy resin; the amount of N,N-dimethyl aniline is 1-2% of the mass of the epoxy resin; the wavelength of ultraviolet light irradiation is 365-370 nm, the power is 500-520 W, and the reaction time is 4-6 h.

[0038] According to the preferred embodiment of the present application, the preparation method of the polyamine-based siloxane-acrylic hybrid body comprises: B1, dissolving the terminal hydroxyl polydimethylsiloxane and isophorone diisocyanate in N,N-dimethyl formamide; heating to 70-72℃ to generate terminal isocyanate group; B2, cooling to 50-52℃, adding hydroxyethyl acrylate to cap the reaction, obtaining an intermediate; then adding polyethylene polyamine and reacting at 80-82℃, and removing unreacted amines under reduced pressure.

[0039] According to the preferred embodiment of the present application, the terminal hydroxyl polydimethylsiloxane is purchased from Hubei Xingfa Organic Silicon New Material Co., Ltd., and the model is XH-201 (terminal hydroxyl polydimethylsiloxane, molecular weight 2000-3000).

[0040] According to the preferred embodiment of the present application, the isophorone diisocyanate is purchased from Wanhua Chemical Group Co., Ltd., and the model is WANNATE 8012 (isophorone diisocyanate, purity ≥ 99.5%).

[0041] According to the preferred embodiment of the present application, the N,N-dimethylformamide is purchased from Jiangsu Feixing Chemical Co., Ltd., and the model is DMF-99.9 (N,N-dimethylformamide, industrial grade high purity, moisture content ≤ 0.05%).

[0042] According to the preferred embodiment of the present application, the hydroxyethyl acrylate is purchased from Wanhua Chemical Group Co., Ltd., and the model is WANLITE HEA-100 (hydroxyethyl acrylate, purity ≥ 99.0%).

[0043] According to the preferred embodiment of the present application, the polyethylene polyamine is purchased from Jiangsu Feixing Chemical Co., Ltd., and the model is DETA-80 (polyethylene polyamine, diethylene triamine content ≥ 80%).

[0044] In the present application, the preparation of the amine group siloxane-acrylic hybrid uses a step-by-step addition reaction; the hydroxyl group (-OH) of the terminal hydroxyl polydimethylsiloxane (PDMS-OH) and the isocyanate group (-NCO) of the isophorone diisocyanate (IPDI) undergo nucleophilic addition reaction to generate an intermediate (PDMS-NCO) with a terminal isocyanate group (-NCO); in this process, the carbon atom of the isocyanate group is attacked by the hydroxyl oxygen atom to form a stable carbamate bond (-NH-CO-O-). Subsequently, hydroxyethyl acrylate (HEA) is added, and its hydroxyl group reacts with the remaining isocyanate group to form an intermediate (PDMS-HEA) containing an acrylic segment (-CH2=CHCOO-), avoiding excessive hydrolysis of the isocyanate group. Finally, polyethylene polyamine (DETA) is added, and the amine group (-NH2) reacts with the unreacted isocyanate group in the intermediate to form a urea bond (-NH-CO-NH-), forming a "siloxane-polyurethane-acrylic" hybrid structure. In this structure, the polyamine group (-NH2) acts as a high-efficiency crosslinking point, which can undergo ring-opening reaction with the epoxy group of the epoxy resin at low temperature to form a dense crosslinking network; the siloxane segment reduces the surface energy of the coating and improves the penetration power; the acrylic segment enhances the water solubility, ensuring the stability of the coating during the electrophoresis process.

[0045] According to the preferred embodiment of the present application, in step B1, the reaction time is 2-4 h.

[0046] According to the preferred embodiment of the present application, the time of the end-capping reaction in step B2 is 1-2h; the reaction time at 80-82℃ is 3-4h.

[0047] The present application also provides a preparation method of the low-temperature curing high throwing power cathodic electrophoretic paint, and the steps include:

[0048] S1, mixing fluorosilicon copolymer type epoxy modifier with epoxy resin, adding ethylene glycol butyl ether and dimethyl sulfoxide, and stirring at 80-82℃; adding polyamine-siloxane-acrylic hybrid, and reacting at 60-62℃;

[0049] S2, adding titanium dioxide, talc, organic bentonite, defoaming agent, and polyether modified polydimethylsiloxane, dispersing at high speed, diluting with deionized water to obtain slurry, and filtering.

[0050] In the preparation process of the present application, the mixing reaction of the fluorosilicon copolymer type epoxy modifier and the epoxy resin is a key step. The epoxy groups in the modifier and the epoxy groups in the epoxy resin form an interpenetrating network structure through an oxygen bridge (-O-), and at the same time, the fluorocarbon chain and the siloxane chain in the modifier migrate to the surface of the paint, reducing the surface tension of the system. The polyamine groups in the polyamine-siloxane-acrylic hybrid crosslink with the epoxy groups in the epoxy resin to form a three-dimensional network structure, significantly improving the crosslinking density of the coating. In the dispersion stage, the pigments such as titanium dioxide and talc are uniformly suspended by the dispersion effect of the organic bentonite, and the defoaming agent and the leveling agent improve the application performance of the paint. After dilution, the water-based paint formed in the electrophoresis process, the negatively charged resin particles (due to the dissociation of carboxyl groups) migrate to the metal workpiece, the low surface energy of the fluorocarbon chain reduces the resistance of the particle migration, and the electric field distribution in the complex cavity area is more uniform, so that a uniform film layer is deposited on the surface of the cavity. In the curing stage, the crosslinking reaction of the epoxy groups and the amine groups is quickly completed under low temperature (120-150℃), and the silanol (-Si-OH) generated by the hydrolysis of siloxane condenses with the hydroxyl groups (-OH) on the metal surface to form a siloxane bond (-Si-O-M-), enhancing the adhesion of the coating to the substrate; the hydrophobicity of the fluorocarbon chain hinders the penetration of water vapor, and the polyamine crosslinking network reduces the porosity of the coating, finally forming a high throwing power, excellent corrosion resistance cathodic electrophoretic coating.

[0051] According to the preferred embodiment of the present application, in step S1, the stirring time at 80-82℃ is 2-3h; the reaction time at 60-62℃ is 1-2h.

[0052] According to the preferred embodiment of the present application, in step S2, the rotation speed of high-speed dispersion is 10000-12000rpm, and the time is 30-40min; the filter screen aperture for filtering is 100-110 mesh.

[0053] The application further provides application of the low-temperature curing high-wet-through cathodic electrophoretic paint or the low-temperature curing high-wet-through cathodic electrophoretic paint prepared by the preparation method to an automobile.

[0054] The application has the following advantages:

[0055] In the application, the fluorosilicon copolymer type epoxy modifier takes bisphenol A epoxy resin as a skeleton, introduces fluorine-containing alkyl and siloxane groups: the siloxane group is hydrolyzed to generate hydroxyl in the curing process, forms a hydrogen bond with the epoxy group, greatly reduces the reaction activation energy, and enables the curing temperature to be reduced to 120-150 DEG C; the fluorine-containing alkyl reduces the surface energy of the coating, and promotes the migration of the resin particles to the metal surface. The polyamine-siloxane-acrylic hybrid takes siloxane as a core, and the acrylic acid is bridged with the polyamine group through the isocyanate, wherein the polyamine group acts as a high-efficiency crosslinking agent, can rapidly react with the epoxy group at low temperature, forms a dense crosslinking network, and avoids the problem of loose film layer caused by incomplete crosslinking of the traditional low-temperature coating. The synergistic effect of the two realizes efficient and complete crosslinking of the coating at low temperature, and solves the contradiction between "low-temperature curing" and "high crosslinking density" in the traditional process.

[0056] The improvement of the wet-through power of complex workpieces is another core advantage of the application. The uneven distribution of the electric field in the traditional electrophoresis process makes it difficult for the resin particles to migrate to the inner cavity surface of the components such as automobile door hinges and wheel covers due to the complex structure and narrow inner cavity, resulting in insufficient film thickness. In the application, the fluorine-containing alkyl of the fluorosilicon copolymer type epoxy modifier has extremely low surface energy, can reduce the contact angle of the coating with the metal surface to below 40 DEG, and significantly reduces the particle migration resistance; the acrylic acid segment of the polyamine-siloxane-acrylic hybrid enhances the water solubility and ion stability of the coating, and the charged particles are more uniformly dispersed and migrate more smoothly in the electrophoresis process.

[0057] The comprehensive performance of the coating of the application also realizes a qualitative leap. The fluorine-containing segment and the siloxane group of the fluorosilicon copolymer type epoxy modifier synergistically form a double protection: the hydrophobicity of the fluorocarbon chain reduces water vapor permeation, the siloxane reacts with the hydroxyl on the metal surface to generate a siloxane bond, and the adhesion between the coating and the substrate is enhanced; the dense network formed by the crosslinking of the polyamine group and the epoxy group of the polyamine-siloxane-acrylic hybrid reduces the porosity of the coating and hinders the penetration of corrosion media. DETAILED DESCRIPTION

[0058] The following detailed description is only used to further illustrate the application, and cannot be understood as limiting the protection scope of the application. Those skilled in the art can make some non-essential improvements and adjustments to the application according to the above application content.

[0059] I. EXAMPLE

[0060] Example 1

[0061] Firstly, the fluorosilicon copolymer type epoxy modifier was prepared: 100 g of bisphenol A epoxy resin was taken into a beaker, 210 g of dimethylbenzene was added, magnetic stirring was started and the temperature was raised to 121 °C, and stirring was continued until the bisphenol A epoxy resin was completely dissolved; 18 g of perfluorooctyl acrylate and 7 g of γ-glycidyl ether oxygen propyl trimethoxysilane were sequentially added to the solution, and stirring was continued for 10 minutes to uniformly mix the three; then 3 g of 2, 4, 6-trimethylbenzoyl-diphenyl phosphine oxide and 1.5 g of N, N-dimethyl aniline were added to the solution, the beaker was transferred to a nitrogen protection device, ultraviolet light irradiation (wavelength 365 nm, power 500 W) was started, the reaction temperature was maintained at 121 °C, and the reaction was carried out for 5 hours; after the reaction was completed, the solution was transferred to a reduced pressure distillation device, and the dimethylbenzene was removed by distillation at 50 °C and -0.09 MPa, and the fluorosilicon copolymer type epoxy modifier was collected.

[0062] Then, the polyamine-based siloxane-acrylic hybrid was prepared: 100 g of hydroxyl-terminated polydimethylsiloxane (molecular weight 2500) was taken into a three-necked flask with stirring device and thermometer, 174 g of isophorone diisocyanate was added, and 200 g of N, N-dimethylformamide was added as a solvent, stirring was started, and the temperature was raised to 71 °C, and the temperature was maintained for 3 hours to generate an isocyanate-terminated intermediate; the reaction system was cooled to 51 °C, 15 g of hydroxyethyl acrylate was added, and the reaction was continued for 1 hour to complete the capping to obtain the intermediate; 60 g of polyethylene polyamine was added to the intermediate, the temperature was raised to 81 °C, and the reaction was carried out for 3.5 hours, after which the unreacted polyethylene polyamine was removed by reduced pressure distillation, and the polyamine-based siloxane-acrylic hybrid was collected.

[0063] Finally, the low-temperature curing high-wetting power cathodic electrophoretic paint was prepared: 120 g of the fluorosilicon copolymer type epoxy modifier prepared above and 550 g of epoxy resin (E-44) were taken into a high-speed mixer, stirring was started, and 220 g of ethylene glycol butyl ether and 60 g of dimethyl sulfoxide were added, the temperature was raised to 81 °C, and stirring was carried out for 2.5 hours; 60 g of the polyamine-based siloxane-acrylic hybrid was added to the mixed system, the temperature was reduced to 61 °C, and the reaction was carried out for 1.5 hours; then 170 g of titanium white, 100 g of talc, 25 g of organic bentonite, 4 g of defoaming agent, and 2.5 g of polyether modified polydimethylsiloxane were sequentially added to the system, a high-speed disperser was started, and the dispersion was carried out at a speed of 11000 rpm for 35 minutes; after the dispersion was completed, deionized water was added to dilute the solid content to 48% (mass fraction), the mixture was filtered through a 105 mesh filter screen to remove impurity particles, and finally the low-temperature curing high-wetting power cathodic electrophoretic paint was obtained.

[0064] Example 2

[0065] The specific implementation is the same as example 1, except that the preparation of the fluorosilicon copolymerized epoxy modifier: take the bisphenol A epoxy resin 120 g is dissolved in 250 g of xylene, heated to 122 ℃ stirring to dissolve; sequentially add perfluoro octyl acrylate 22 g and γ-glycidyl ether oxygen propyl trimethoxysilane 9 g, stirring uniform; add 2,4,6-trimethyl benzoyl-diphenyl phosphine oxide 4 g and N,N-dimethyl aniline 2 g, under the protection of nitrogen, with 368 nm wavelength, 510 W power ultraviolet light irradiation reaction 5.5 h; remove xylene by distillation under reduced pressure, to obtain fluorosilicon copolymerized epoxy modifier.

[0066] The preparation of polyamine based siloxane-acrylic hybrid: take the end hydroxyl polydimethylsiloxane 120 g and isophorone diisocyanate 209 g is dissolved in N,N-dimethyl formamide 240 g, heated to 72 ℃ reaction 3.5 h to generate end isocyanate intermediate; cooling to 52 ℃, add hydroxyethyl acrylate 18 g to cap reaction 1.5 h, to obtain intermediate; add polyethylene polyamine 70 g at 82 ℃ for 3.5 h, remove unreacted amine under reduced pressure, to obtain polyamine based siloxane-acrylic hybrid.

[0067] The preparation of low temperature curing high penetration cathode electrophoretic coating: fluorosilicon copolymerized epoxy modifier 140 g and epoxy resin 600 g are mixed, add ethylene glycol butyl ether 250 g and dimethyl sulfoxide 70 g, heated to 82 ℃ stirring 3 h; add polyamine based siloxane-acrylic hybrid 70 g, reaction at 62 ℃ for 2 h; add titanium dioxide 200 g, talc 120 g, organic bentonite 30 g, defoaming agent 5 g, polyether modified polydimethylsiloxane 3 g, high speed dispersion for 40 min at 12000 rpm, dilute to 50% solid with deionized water, filter through 110 mesh screen to obtain the coating.

[0068] Example 3

[0069] The specific implementation is the same as example 1, except that the preparation of the fluorosilicon copolymerized epoxy modifier: take the bisphenol A epoxy resin 120 g is dissolved in 250 g of xylene, heated to 122 ℃ stirring to dissolve; sequentially add perfluoro octyl acrylate 22 g and γ-glycidyl ether oxygen propyl trimethoxysilane 9 g, stirring uniform; add 2,4,6-trimethyl benzoyl-diphenyl phosphine oxide 4 g and N,N-dimethyl aniline 2 g, under the protection of nitrogen, with 368 nm wavelength, 510 W power ultraviolet light irradiation reaction 5.5 h; remove xylene by distillation under reduced pressure, to obtain fluorosilicon copolymerized epoxy modifier.

[0070] Preparation of polyamine-silicone-acrylic hybrid: hydroxyl-terminated polydimethylsiloxane 110 g and isophorone diisocyanate 220 g were dissolved in N,N-dimethylformamide 220 g, and the mixture was heated to 71 °C and reacted for 3.2 h to form an isocyanate-terminated intermediate; the temperature was lowered to 51 °C, and hydroxyethyl acrylate 16 g was added to cap the intermediate and reacted for 1.2 h; polyvinyl polyamine 65 g was then added, and the mixture was heated to 81 °C and reacted for 3.8 h; unreacted amine was removed by reduced pressure to obtain the polyamine-silicone-acrylic hybrid.

[0071] Preparation of low-temperature curing high-sag cathodic electrophoretic paint: fluorosilicone copolymer type epoxy modifier 130 g and epoxy resin 580 g were mixed, and ethylene glycol butyl ether 230 g and dimethyl sulfoxide 65 g were added; the mixture was heated to 81 °C and stirred for 2.8 h; polyamine-silicone-acrylic hybrid 65 g was added, and the mixture was reacted at 61 °C for 1.8 h; titanium dioxide 180 g, talc 110 g, organic bentonite 28 g, defoaming agent 4.5 g, and polyether-modified polydimethylsiloxane 2.8 g were added, and the mixture was dispersed at 11500 rpm for 38 min; deionized water was added to dilute the mixture to a solid content of 49%, and the mixture was filtered through a 108-mesh screen to obtain the paint.

[0072] Comparative Example 1

[0073] The specific implementation was the same as in Example 1, except that the polyamine-silicone-acrylic hybrid was prepared as follows: the procedure of Example 1 was used to obtain 60 g of the polyamine-silicone-acrylic hybrid. The low-temperature curing high-sag cathodic electrophoretic paint was prepared as follows: epoxy resin 550 g and polyamine-silicone-acrylic hybrid 60 g were mixed, and ethylene glycol butyl ether 220 g and dimethyl sulfoxide 60 g were added; the mixture was heated to 81 °C and stirred for 2.5 h; titanium dioxide 170 g, talc 100 g, organic bentonite 25 g, defoaming agent 4 g, and polyether-modified polydimethylsiloxane 2.5 g were added, and the mixture was dispersed at 11000 rpm for 35 min; deionized water was added to dilute the mixture to a solid content of 48%, and the mixture was filtered through a 105-mesh screen to obtain the paint (without fluorosilicone copolymer type epoxy modifier).

[0074] Comparative Example 2

[0075] The specific implementation is the same as example 1, except that the preparation of the fluorosilicone copolymer epoxy modifier: the same as example 1 step, 120 g of fluorosilicone copolymer epoxy modifier is obtained. Preparation of low-temperature curing high-wetting cathodic electrophoretic paint: mix 550 g of epoxy resin with 120 g of fluorosilicone copolymer epoxy modifier, add 220 g of ethylene glycol butyl ether and 60 g of dimethyl sulfoxide, and stir at 81°C for 2.5h; add 170 g of titanium white, 100 g of talc, 25 g of organic bentonite, 4 g of defoaming agent, and 2.5 g of polyether modified polydimethylsiloxane, and disperse at 11000 rpm for 35 min; dilute with deionized water to a solid content of 48%, filter through a 105 mesh filter to obtain the paint (without polyamine-silicone-acrylic hybrid).

[0076] Comparative example 3

[0077] The specific implementation is the same as example 1, except that the preparation of the fluorosilicone copolymer epoxy modifier: the same as example 1 step, 120 g of fluorosilicone copolymer epoxy modifier is obtained. Preparation of low-temperature curing high-wetting cathodic electrophoretic paint: mix 550 g of epoxy resin with 120 g of fluorosilicone copolymer epoxy modifier, add 220 g of ethylene glycol butyl ether and 60 g of dimethyl sulfoxide, and stir at 81°C for 2.5h; add 170 g of titanium white, 100 g of talc, 25 g of organic bentonite, 4 g of defoaming agent, and 2.5 g of polyether modified polydimethylsiloxane, and disperse at 11000 rpm for 35 min; dilute with deionized water to a solid content of 48%, filter through a 105 mesh filter to obtain the paint (without polyamine-silicone-acrylic hybrid).

[0078] II. Performance test

[0079] The insulating material prepared in the above examples 1-3 and comparative examples 1-3 is tested for performance according to the following method:

[0080] 1. Curing temperature test: take a 50mm x 100mm x 0.2mm tin plate, evenly coat the paint on the surface of the tin plate with a wire bar applicator (dry film thickness 20-25μm), and place it in a constant temperature oven. Start timing from 120°C, every 10°C is a test point, and record the lowest temperature at which the coating is completely cured (not sticky, pencil hardness ≥H).

[0081] 2. Wetting power test (Ford box method): prepare a Ford box model with an inner cavity size of 50mm x 50mm x 10mm (stainless steel material), coat the paint on the outer surface of the model (dry film thickness 25-30μm), and take out the model after curing according to the paint curing conditions. Measure the film thickness of the four sides and the top of the inner cavity with a vernier caliper, and take the average value as the inner cavity film thickness.

[0082] 3. Corrosion resistance test (neutral salt spray test): according to GB / T 10125-2012 standard, the cured coating test piece (size 150 mm x 70 mm x 0.2 mm, film thickness 25-30 μm) was placed in a salt spray chamber, and the test conditions were 5% NaCl solution (pH 6.5-7.2), temperature 35±2℃, continuous spraying. The time of rust (red rust) appearing on the surface of the coating was observed, and the time of the first rust appearing was recorded.

[0083] 4. Adhesion test (crosshatch method): according to ISO 2409 standard, a 1 mm x 1 mm square grid (10 x 10 grids) was drawn on the surface of the cured coating with a crosshatch tool (spacing 1 mm), and was pasted with 3M 600 type adhesive tape. After tearing off, the square grid was observed for falling off. Rating standard: 0 level (no falling off), 1 level (≤5% falling off), 2 level (5%-15% falling off), 3 level (15%-35% falling off), 4 level (35%-65% falling off), 5 level (>65% falling off).

[0084] 5. Pencil hardness test (GB / T 6739-2006): using a Mitsubishi pencil hardness tester, the surface of the coating was drawn from 9B to 9H in turn (load 7.5 N, 5 times per second), and the hardest pencil model that did not scratch the surface of the coating was recorded (such as 2H indicating that 2H pencil did not scratch, 3H pencil scratched).

[0085] 6. Performance test results:

[0086] Table 1: Performance test results of each example and comparative example

[0087]

[0088] As can be seen from Table 1, examples 1-3 effectively solve the problems of high energy consumption, uneven film thickness in inner cavity of complex workpiece and poor corrosion resistance of existing cathodic electrophoretic coating by the synergistic effect of two modifiers. From the performance test results, the curing temperature (125-130℃) of examples 1-3 is significantly lower than that of the comparative examples (178-195℃), indicating that the siloxane groups in the fluorosilicone copolymer epoxy modifier and the polyamine groups in the polyamine-based siloxane-acrylic hybrid body synergistically reduce the curing activation energy, achieve low-temperature curing and greatly reduce energy consumption; the inner cavity film thickness (16.2-18.5μm) is much higher than that of the comparative examples (8.2-10.5μm), which is due to the fluorocarbon chain in the fluorosilicone copolymer epoxy modifier reducing the surface energy to promote the migration of the resin to the inner cavity, and the acrylic segment in the polyamine-based siloxane-acrylic hybrid body enhancing the water solubility and electrophoretic stability, which together improve the film thickness uniformity in the inner cavity of complex workpiece; the salt spray corrosion time (3500-4000h) is significantly longer than that of the comparative examples (1500-2000h), which is due to the hydrophobicity of the fluorosilicon chain hindering water vapor penetration, the reaction of siloxane and hydroxyl groups on the metal surface to form siloxane bond to enhance the bonding force, and the dense network formed by the crosslinking of polyamine groups to reduce the pores of the coating, which together improve the corrosion resistance. In addition, the adhesion (0 level) and pencil hardness (2H) of examples 1-3 are better than those of the comparative examples, further verifying the improvement of the modified agent on the comprehensive performance of the coating.

[0089] The above-described examples only express several embodiments of the present application, and the description is more specific and detailed, but it should not be understood as limiting the scope of the present patent. It should be noted that for ordinary skilled in the art, without departing from the concept of the present application, several modifications and improvements can be made, which are within the scope of protection of the present application.

Claims

1. A low temperature cure, high throw power cathodic electrodepositable coating characterized in that, The raw materials include the following by weight: Epoxy resin: 500-600 parts by weight; Fluorine-silicon copolymer type epoxy modifier: 100-150 parts by weight; Polyamine-siloxane-acrylic hybrid: 50-80 parts by weight; Ethylene glycol butyl ether: 200-250 parts by weight; Dimethyl sulfoxide: 50-80 parts by weight; Titanium white powder: 150-200 parts by weight; Talc: 80-120 parts by weight; Organic bentonite: 20-30 parts by weight; Defoaming agent: 3-5 parts by weight; Polyether modified polydimethylsiloxane: 2-3 parts by weight; Deionized water: 200-250 parts by weight; The preparation method of the fluorine-silicon copolymer type epoxy modifier includes: A1, dissolving bisphenol A epoxy resin in xylene, stirring and dissolving under heating to 120-122℃; sequentially adding perfluoro octyl acrylate and γ-glycidyl ether oxygen propyl trimethoxysilane; A2, adding 2,4,6-trimethylbenzoyl-diphenyl phosphine oxide and N,N-dimethyl aniline, and reacting under ultraviolet light irradiation under nitrogen protection; after the reaction is completed, distillation under reduced pressure; the preparation method of the polyamine-siloxane-acrylic hybrid includes: B1, dissolving hydroxyl-terminated polydimethylsiloxane and isophorone diisocyanate in N,N-dimethylformamide; reacting under heating to 70-72℃ to generate isocyanate end groups; B2, cooling to 50-52℃, adding hydroxyethyl acrylate to cap the reaction, obtaining an intermediate; then adding polyethylene polyamine, and reacting under 80-82℃, and removing unreacted amines under reduced pressure.

2. The low temperature cure, high throw power cathodic electrodepositioa coating of claim 1 wherein, In step A1, the mass ratio of bisphenol A epoxy resin to xylene is 1: (2-2.2).

3. The low temperature cure, high throw power cathodic electrodeposition coating of claim 1, wherein, In step A2, the amount of 2,4,6-trimethylbenzoyl-diphenyl phosphine oxide is 2-4% of the mass of the epoxy resin; the amount of N,N-dimethyl aniline is 1-2% of the mass of the epoxy resin; the wavelength of the ultraviolet light irradiation is 365-370nm, the power is 500-520W, and the reaction time is 4-6h.

4. The low temperature cure, high throw power cathodic electrodeposition coating of claim 1, wherein, In step B1, the reaction time is 2-4h.

5. The low temperature cure, high throw power cathodic electrodeposition coating of claim 1, wherein, In step B2, the capping reaction time is 1-2h; the reaction time under 80-82℃ is 3-4h.

6. A process for the preparation of a low temperature cured high throw power cathodic electrodeposition coating according to any one of claims 1 to 5, characterized by the steps It includes: S1, mixing the fluorine-silicon copolymer type epoxy modifier with the epoxy resin, adding ethylene glycol butyl ether and dimethyl sulfoxide, and stirring under heating to 80-82℃; adding the polyamine-siloxane-acrylic hybrid, and reacting under 60-62℃; S2, adding titanium white powder, talc, organic bentonite, defoaming agent, polyether modified polydimethylsiloxane, high-speed dispersing, diluting with deionized water to obtain a slurry, and filtering.

7. The production method according to claim 6, characterized by, In step S1, the stirring time under heating to 80-82℃ is 2-3h; the reaction time under 60-62℃ is 1-2h.

8. The preparation method according to claim 6, characterized in that, In step S2, the high-speed dispersion speed is 10000-12000rpm, and the time is 30-40min; the filter screen aperture for filtering is 100-110 mesh.

9. Use of a low temperature cured high build cathodic electrocoat according to any one of claims 1 to 5 or a low temperature cured high build cathodic electrocoat prepared according to the process of any one of claims 6 to 8, characterized in that, The application of the low-temperature curing high-swimming force cathode electrophoretic paint on automobiles.

Images