Settlement-free and precipitation-free colored electrophoretic paint and preparation method thereof

Abstract

The invention provides a non-settling and non-precipitation colored electrophoretic coating and a preparation method thereof, and belongs to the technical field of electrophoretic coatings. The invention discloses a non-settling and non-precipitation colored electrophoretic coating which comprises the following components in parts by weight: 30-45 parts of waterborne polyurethane resin, 8-12 parts of polyether polyol, 2-4 parts of zinc dihydrogen phosphate, 5-20 parts of filler, 1-2.5 parts of a catalyst, 1-3 parts of a phthalate coupling agent, 8-20 parts of color paste and 5-30 parts of deionized water. The color paste is prepared from the following components in parts by weight: 15 to 35 parts of modified acrylic resin, 10 to 25 parts of azole silane modified pigment, 5 to 10 parts of cardanol polyoxyethylene ether and 20 to 40 parts of deionized water; the invention also provides a preparation method of the colored electrophoretic paint. The colored electrophoretic paint provided by the invention has excellent storage stability, and is free from precipitation; the cured coating has high hardness and high adhesive force, has excellent water resistance, wear resistance, chemical resistance, corrosion resistance and the like, is uniform in color, and prolongs the service life of the colored electrophoretic paint.

Description

Technical Field

[0001] The invention belongs to the technical field of electrophoretic coatings, and in particular relates to a non-sedimentation and non-precipitation colored electrophoretic coating and a preparation method thereof. Background Art

[0002] Electrophoretic coating is a water-based anti-corrosion coating with the advantages of high throwing power, high Coulomb efficiency, easy control of the coating process, and low pollution. It has been widely used in the automotive, hardware and electrical appliances, metal eyeglass frames, jewelry, medical equipment, toys and other industries. Cathodic electrophoretic coating is composed of water-soluble base resin, pigment, additive, neutralizer, etc., and is constructed by electrophoresis (i.e., electrodeposition, electrolysis, etc.). The base resins used in existing electrophoretic coatings are mainly epoxy resin, acrylic resin and polyurethane resin. Epoxy resin electrophoretic coating has excellent salt spray performance and deep hole throwing power, but poor weather resistance, easy to powder, resulting in peeling of the topcoat; acrylic resin electrophoretic coating has excellent weather resistance and anti-yellowing function, high transparency, but poor salt spray resistance; polyurethane resin electrophoretic coating has high transparency and good weather resistance, but general salt spray resistance. In addition, the stability of pigments in electrophoretic coatings and compatibility with resins in coatings have limited the development of colored electrophoretic coatings.

[0003] Waterborne polyurethane coating refers to a solution or emulsion formed by polyurethane dissolved or dispersed in water. The coating film formed has the characteristics of good adhesion, flexibility, wear resistance, excellent chemical corrosion resistance, and good electrical insulation performance. However, compared with solvent-based polyurethane, waterborne polyurethane coating has the disadvantages of poor water resistance, chemical resistance and solvent resistance, and low hardness.

[0004] At the same time, electrophoretic coatings have high requirements for pigments. High-performance organic pigments are usually used to make electrophoretic color pastes, such as phthalocyanines, condensed azos, quinacridones, benzimidazolone, anthraquinone ketones, isoindolinones and other pigments. The properties of the pigments in the color paste have an important influence on the performance of the coating. If the pigment particles are coarse and large, the prepared electrophoretic tank liquid will be unstable, and problems such as precipitation and floating color will occur, thus affecting the color, fastness, smoothness, density and uniformity of the coating. In order to make the pigments and fillers disperse evenly and stably in the electrophoretic coating color paste, it is often necessary to modify the pigments or resins.

[0005] Invention patent CN202011251258.0 discloses a weather-resistant colored electrophoretic coating and a preparation method thereof. The color paste in the colored electrophoretic coating includes a quaternary ammonium salt-modified acrylic resin, a polycarboxylate-modified pigment, a cosolvent, and deionized water. The emulsion includes a hydroxy acrylic resin, zirconium phosphate, a neutralizer, and deionized water. The quaternary ammonium salt-modified acrylic resin is prepared by reacting a quaternizing agent with an acrylic resin containing an epoxy group, so that the colored electrophoretic coating has excellent dispersibility, weather resistance, corrosion resistance, and storage stability. However, the water resistance and solvent resistance of the electrophoretic coating are average. Invention patent CN201810876141.8 discloses a polyurethane electrophoretic coating, wherein the polyurethane resin is prepared by reacting a) 10 to 40 parts of one or more of polypropylene glycol, polyethylene glycol, EO / PO block polyether polyol, EO / PO blended polyether polyol, adipic acid polyester polyol, polycarbonate polyol, and polytetrahydrofuran polyol with a molecular weight of 400 to 15,000 and an average functionality of 2 to 5, with b) 5 to 200 parts of polyisocyanate. The flexibility of the coating can be adjusted arbitrarily, and it has excellent corrosion resistance, adhesion and weather resistance. However, the pigment in the coating has poor stability, is easy to settle and precipitate, and has average water resistance and chemical resistance, which affects the appearance and service life of the colored electrophoresis. Summary of the invention

[0006] The purpose of the present invention is to provide a non-sedimentation and non-precipitation colored electrophoretic coating, which has excellent storage stability and is non-precipitation and non-precipitation; the cured coating has high hardness and high adhesion, excellent water resistance, wear resistance, chemical resistance, corrosion resistance, etc., the coating has uniform color, and the service life of the colored electrophoretic coating is extended.

[0007] In order to achieve the purpose of the present invention, the present invention provides a non-sedimentation and non-precipitation colored electrophoretic coating, comprising the following components in parts by weight: 30-45 parts of waterborne polyurethane resin, 8-12 parts of polyether polyol, 2-4 parts of zinc dihydrogen phosphate, 5-20 parts of filler, 1-2.5 parts of catalyst, 1-3 parts of phthalate coupling agent, 8-20 parts of color paste and 5-30 parts of deionized water.

[0008] The color paste comprises the following components in parts by weight: 15-35 parts of modified acrylic resin, 10-25 parts of azole silane modified pigment, 5-10 parts of cardanol polyoxyethylene ether and 20-40 parts of deionized water.

[0009] Furthermore, the preparation method of the waterborne polyurethane resin specifically comprises the following steps:

[0010] S1. Add polytrimethylene ether glycol and polypropylene glycol to a container, evacuate at 100-120°C for 0.5-1.5h, then release the vacuum and introduce nitrogen, cool to 50-60°C, add dibutyltin dilaurate, hexamethylene diisocyanate and dithioglycolic acid, and heat to 80-90°C for reaction for 2-4h to obtain a prepolymer;

[0011] P2. Add polytetrahydrofuran diol to the above prepolymer, continue to react at 80-90°C for 2-3h, then cool to 65-75°C, add terminal hydroxyl polydimethylsiloxane, keep warm for 3-6h or until the -NCO content is determined to be ≤0.1%, cool naturally and evacuate for 5-10min to obtain a waterborne polyurethane resin.

[0012] Furthermore, the molar ratio of -NCO in the hexamethylene diisocyanate to -OH in the polytrimethylene ether glycol is (1.5-2.5):1;

[0013] The amount of polypropylene glycol added is 12-20% of the total mass of hexamethylene diisocyanate and polytrimethylene ether glycol;

[0014] The amount of dibutyltin dilaurate added is 0.05-0.12% of the total mass of hexamethylene diisocyanate and polytrimethylene ether glycol;

[0015] The amount of dithioglycolic acid added is 10-15% of the total mass of the hexamethylene diisocyanate and polytrimethylene ether glycol;

[0016] The amount of the polytetrahydrofuran diol added is 2.0-2.8% of the total mass of the hexamethylene diisocyanate and the cardanol-based polyol;

[0017] The mass ratio of the terminal hydroxyl polydimethylsiloxane to the hexamethylene diisocyanate is 1:(0.3-0.5).

[0018] The colored electrophoretic coating of the present invention adopts waterborne polyurethane resin as base resin, reacts polytrimethylene ether glycol, dithioglycolic acid and hexamethylene diisocyanate under the action of dibutyltin dilaurate to obtain a prepolymer containing disulfide bonds, then adds polytetrahydrofuran diol for reaction, and finally adds terminal hydroxyl polydimethylsiloxane for end-capping. The introduction of dithioglycolic acid can not only improve the adhesion, wear resistance and water resistance of the electrophoretic coating, but also improve the stability of the electrophoretic coating system; the addition of polytetrahydrofuran diol not only increases the strength and toughness of the waterborne polyurethane resin, but also improves the viscosity, water resistance, solvent resistance, wear resistance and weather resistance of the coating of the present invention; the use of terminal hydroxyl polydimethylsiloxane for end-capping improves the stability of the pigment in the electrophoretic coating, is not easy to settle and is not easy to precipitate, and at the same time increases the compatibility with other components of the coating, thereby improving the adhesion, water resistance, corrosion resistance, wear resistance and solvent resistance of the coating of the present invention.

[0019] Furthermore, the polyether polyol is any one of PPG2000, PPG3000 or PPG4000. The addition of polyether polyol increases the interfacial bonding force between the components of the coating, improves the throwing power and adhesion of the coating, and ensures that the coating film of the present invention has higher hardness and toughness.

[0020] Furthermore, the filler is composed of organic bentonite and nano-montmorillonite in a mass ratio of (1.2-2.0): 1. By selecting fillers with specific proportions and components for combination, not only the hardness, adhesion, corrosion resistance and rheological properties of the coating of the present invention are improved, but also the anti-precipitation stability of the coating is increased to prevent the pigment from precipitating or precipitating in the coating.

[0021] Furthermore, the preparation method of the modified acrylic resin comprises the following steps:

[0022] P1. First, add 1 / 2 mass of tri-n-butyl borane to an appropriate amount of ethylene glycol butyl ether to dissolve completely, then add it to the reactor and heat it to 60-70℃;

[0023] P2. Weigh the acrylic monomer, polycarbodiimide and the remaining tri-n-butylborane according to the formula, mix them evenly, and then add them dropwise to the reactor at a uniform speed within 1 hour, control the reaction temperature at 70-80°C, keep warm for 2-4 hours, and then add alkylamide propyl polyhydroxy quaternary ammonium salt dropwise, the addition time is controlled within 30 minutes, and react for 2-4 hours;

[0024] P3. After the reaction is completed, the temperature of the reactor is lowered to 40°C, and aqueous ammonia is added while stirring for neutralization. The reaction is stirred for 15-25 minutes, and then cooled to room temperature to obtain a modified acrylic resin.

[0025] Furthermore, the modified acrylic resin is composed of the following raw materials in parts by weight: 82-90 parts of acrylic monomer, 10-20 parts of alkylamide propyl polyhydroxy quaternary ammonium salt, 2-5 parts of tri-n-butyl borane and 3-6 parts of polycarbodiimide.

[0026] Furthermore, the acrylic monomer is composed of the following monomers in parts by weight: 25-40 parts of methyl methacrylate, 16-24 parts of lauryl acrylate, 8-20 parts of acrylic acid, 20-28 parts of acetic anhydride and 3-5 parts of hydroxy acrylic acid.

[0027] The present invention is to prepare a prepolymer by polymerization of acrylic monomers under the action of polycarbodiimide and tri-n-butylborane, and then introduce alkylamide propyl polyhydroxy quaternary ammonium salt to react and prepare the prepolymer. The acrylic monomers in the present invention are composed of methyl methacrylate, lauryl acrylate, acrylic acid, acetic anhydride and hydroxy acrylic acid in a specific ratio, and hard monomers, soft monomers, functional monomers and hydroxyl-containing monomers are used in combination, while ensuring the high hardness, high toughness and high strength of acrylic resin, the adhesion, weather resistance, solvent resistance and corrosion resistance of acrylic resin are also improved; the type and proportion of the monomers are optimized, which is conducive to improving the crosslinking density of the coating, thereby increasing the hardness and wear resistance of the coating; the introduction of alkylamide propyl polyhydroxy quaternary ammonium salt improves the hardness and weather resistance of the coating, strengthens the internal cohesion and interface bonding force of the coating, can make the pigment better suspended in the coating system, and improves the stability of the coating system, but reduces the water resistance and solvent resistance of the present invention.

[0028] Furthermore, the azole silane modified pigment is prepared by uniformly mixing 5-10 parts of triazole silane compound, 3-6 parts of wetting agent TEGO and 84-92 parts of pigment, in parts by weight.

[0029] The present invention adopts triazole silane compounds to modify the pigment, thereby improving the dispersibility of the pigment in the coating and enhancing the interfacial bonding force between the pigment and other components of the coating, making it less likely to sink and precipitate, while improving the adhesion, weather resistance, corrosion resistance and water and solvent resistance of the present invention, and making the coating surface smooth and uniform in color.

[0030] The present invention also provides a method for preparing a non-sedimentation and non-precipitation colored electrophoretic coating, which specifically comprises the following steps:

[0031] (1) After adding polyether polyol and filler into a container and mixing, the mixture is stirred and dispersed for 1-2 hours under vacuum conditions at a temperature of 110° C. to 120° C. while dehydrating, and then the vacuum is released after the temperature is lowered to below 50° C.;

[0032] (2) then adding waterborne polyurethane resin and zinc dihydrogen phosphate, stirring for 10-20 minutes at room temperature and pressure;

[0033] (3) Then add the catalyst, phthalate coupling agent, color paste and deionized water in sequence, stir for 20-30 minutes, vacuum degassing for 5-10 minutes, and release the vacuum to obtain a colored electrophoretic coating without sedimentation or precipitation.

[0034] The present invention has achieved the following beneficial effects:

[0035] 1. The colored electrophoretic coating of the present invention is based on a waterborne polyurethane resin and is modified by adding dithioglycolic acid to ensure that the obtained coating has excellent mechanical properties, adhesion, weather resistance, wear resistance and corrosion resistance, while also improving the water resistance, solvent resistance and stability of the coating; the addition of polyether polyol can adjust the softness and hardness of the colored electrophoretic coating to make it have higher hardness and toughness, while improving the throwing power and adhesion of the coating and increasing the interface bonding force between the components of the coating; the addition of zinc dihydrogen phosphate improves the adhesion, wear resistance and corrosion resistance of the coating of the present invention, while not affecting the water resistance and solvent resistance of the present invention (experiments have shown that the zinc dihydrogen phosphate of the present invention has good adhesion and good corrosion resistance). The addition of zinc does not reduce the water resistance and solvent resistance of the coating); the addition of color paste, on the one hand, meets the requirements of different colors of the electrophoretic coating, and on the other hand, the modified pigment is compounded with modified acrylic resin, cardanol polyoxyethylene ether, etc., so that the pigment is evenly dispersed in the coating, and the interfacial bonding force between the pigment and each component of the coating is enhanced, so that the pigment can be better suspended in the coating system and the sedimentation phenomenon is reduced; the addition of fillers, catalysts, phthalate coupling and other ingredients makes the electrophoretic coating of the present invention have better stability, so that the pigment can be stably suspended in the coating system for a long time without sedimentation, thereby ensuring the color, fastness, smoothness and density of the coating film, and ensuring the use effect and service life of the electrophoretic coating.

[0036] 2. The raw materials selected in the present invention are environmentally friendly, low in cost, simple in preparation process, low in energy consumption, and do not contain volatile toxic substances, thus meeting the requirements of national environmental protection laws.

[0037] 3. The coating film made by the electrophoretic coating of the present invention is dense, uniform in color, has high adhesion, hardness, and mechanical strength, and has excellent water resistance, wear resistance, chemical resistance, corrosion resistance, etc. The pigment is evenly colored, which ensures the beauty of the coating and extends the service life of the colored electrophoretic coating. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] The non-sedimentation and non-precipitation colored electrophoretic coating and its preparation method of the present invention are described below in conjunction with specific embodiments.

[0040] Example 1

[0041] The preparation method of the non-sedimentation and non-precipitation colored electrophoretic coating of Example 1 is as follows:

[0042] (1) 8 parts of PPG2000 and 12 parts of filler were added to a container and mixed, and then stirred and dispersed for 2 hours under vacuum conditions at a temperature of 110°C while dehydrating, and then the vacuum was released after the temperature was lowered to below 50°C;

[0043] (2) then adding 30 parts of waterborne polyurethane resin and 3 parts of zinc dihydrogen phosphate, stirring at room temperature and pressure for 15 minutes;

[0044] (3) Then, 1.2 parts of dibutyltin dilaurate, 1.5 parts of phthalate coupling agent KR-12, 12 parts of color paste and 7 parts of deionized water were added in sequence, stirred for 30 minutes, and vacuum degassed for 10 minutes. After the vacuum was released, a colored electrophoretic coating without sedimentation or precipitation was obtained.

[0045] The preparation method of the above waterborne polyurethane resin is as follows:

[0046] 1 kg of polytrimethylene ether glycol and 175 g of polypropylene glycol are added to a container, and the container is evacuated at 110° C. for 1.5 hours, then the vacuum is released and nitrogen is introduced, the temperature is lowered to 60° C., 1 g of dibutyltin dilaurate, 252 g of hexamethylene diisocyanate and 150 g of dithioglycolic acid are added, and the temperature is raised to 90° C. for reaction for 3 hours to obtain a prepolymer; 27.5 g of polytetrahydrofuran diol is added to the prepolymer, the reaction is continued at 90° C. for 3 hours, then the temperature is lowered to 70° C., 75.6 g of terminal hydroxyl polydimethylsiloxane is added, the temperature is kept for 5 hours, naturally cooled and evacuated for 10 minutes to obtain a waterborne polyurethane resin.

[0047] The above-mentioned polytrimethylene ether glycol is selected from PO3G bio-based high-performance polyol of Guangzhou Haoyi New Materials, model H1000 (the models selected in the following embodiments or comparative examples are the same); dithioglycolic acid is provided by Shanghai Hansi Chemical (the models selected in the following embodiments or comparative examples are the same).

[0048] The color paste is composed of the following components in parts by weight: 16 parts of modified acrylic resin, 10 parts of azole silane modified pigment, 8 parts of cardanol polyoxyethylene ether and 20 parts of deionized water.

[0049] The preparation method of the modified acrylic resin is as follows:

[0050] First, 1.5 parts of tri-n-butylborane are added to an appropriate amount of ethylene glycol butyl ether to dissolve completely, and then added to a reactor and heated to 70°C; 85 parts of acrylic monomer, 4.6 parts of polycarbodiimide and 1.5 parts of tri-n-butylborane are mixed evenly, and then uniformly added to the reactor within 1 hour, the reaction temperature is controlled at 80°C, and the temperature is kept for 3 hours, and then 15 parts of alkylamide propyl polyhydroxy quaternary ammonium salt are added dropwise, the dropping time is controlled within 30 minutes, and the reaction is carried out for 4 hours; after the reaction is completed, the temperature of the reactor is lowered to 40°C, and ammonia water is added while stirring for neutralization, the reaction is stirred for 20 minutes, and the reaction is cooled to room temperature to obtain a modified acrylic resin.

[0051] The acrylic monomer is composed of the following monomers in parts by weight: 36 parts of methyl methacrylate, 22 parts of lauryl acrylate, 15 parts of acrylic acid, 24 parts of acetic anhydride and 3 parts of hydroxy acrylic acid.

[0052] The above-mentioned alkyl amide propyl polyhydroxy quaternary ammonium salt is selected from Ningbo Dongfang Yongning Chemical Industry, and the model is YN1232 (the model selected in the following embodiments or comparative examples is the same).

[0053] The above-mentioned azole silane modified pigment is prepared by mixing 9 parts of triazole silane compound, 5 parts of wetting agent TEGO and 86 parts of pigment (Permanent Red 1701 is selected, and the same type is selected in the following embodiments or comparative examples).

[0054] The preparation process of the above triazole silane compound is as follows: add 20% sodium carbonate solution to a mixed solution of 3-amino-5-ethyl-1,2,4-triazole and 100 mL of N-methylpyrrolidone at room temperature, heat to 60°C and stir for 1 hour, then add 3-chloropropyltriethoxysilane, stir at 80°C for 6 hours, and after the reaction is completed, cool to room temperature, filter, wash the filter cake with 2% NaHCO3 solution and deionized water until neutral, and dry to obtain the triazole silane compound; the molar ratio of 3-amino-5-ethyl-1,2,4-triazole, sodium carbonate solution and 3-chloropropyltriethoxysilane is 1:1:1. (The triazole silane compounds used in the following examples and comparative examples are the same as here, and will not be repeated below)

[0055] The wetting agent TEGO is selected from TEGO SURTEN W111 produced by Evonik (the same model is selected in the following embodiments or comparative examples).

[0056] The above-mentioned cardanol polyoxyethylene ether is selected from Shanghai Banggao Chemical (the types selected in the following embodiments or comparative examples are the same).

[0057] The filler is composed of organic bentonite and nano-montmorillonite in a mass ratio of 1.2:1. The organic bentonite is selected from Shanghai Wanzhao, model WSG-PN06 (the same model is selected in the following embodiments or comparative examples); the nano-montmorillonite is selected from Guangzhou Yifeng Chemical, model TY-710C (the same model is selected in the following embodiments or comparative examples).

[0058] Example 2

[0059] The preparation method of the non-sedimentation and non-precipitation colored electrophoretic coating of Example 2 is as follows:

[0060] (1) 12 parts of PPG2000 and 18 parts of filler were added to a container and mixed, and then stirred and dispersed for 2 hours under vacuum conditions at a temperature of 110°C while dehydrating, and then the vacuum was released after the temperature was lowered to below 50°C;

[0061] (2) then adding 45 parts of waterborne polyurethane resin and 4 parts of zinc dihydrogen phosphate, stirring for 15 minutes at room temperature and pressure;

[0062] (3) Then, 2 parts of dibutyltin dilaurate, 2.5 parts of phthalate coupling agent KR-12, 20 parts of color paste and 15 parts of deionized water were added in sequence, stirred for 30 minutes, vacuum degassed for 10 minutes, and the vacuum was released to obtain a colored electrophoretic coating without sedimentation or precipitation.

[0063] The preparation method of the above waterborne polyurethane resin is as follows:

[0064] 1 kg of polytrimethylene ether glycol and 255.6 g of polypropylene glycol were added to a container, and the mixture was evacuated at 110° C. for 1.5 hours. The vacuum was then released and nitrogen was introduced. The temperature was lowered to 60° C., 1.7 g of dibutyltin dilaurate, 420 g of hexamethylene diisocyanate and 213 g of dithioglycolic acid were added, and the temperature was raised to 90° C. for reaction for 3 hours to obtain a prepolymer. 39.8 g of polytetrahydrofuran diol was added to the prepolymer, and the reaction was continued at 90° C. for 3 hours. The temperature was then lowered to 70° C., 210 g of terminal hydroxyl polydimethylsiloxane was added, the mixture was kept warm for 5 hours, naturally cooled and evacuated for 10 minutes to obtain a waterborne polyurethane resin.

[0065] The color paste is composed of the following components in parts by weight: 35 parts of modified acrylic resin, 24 parts of azole silane modified pigment, 10 parts of cardanol polyoxyethylene ether and 36 parts of deionized water.

[0066] The composition and preparation method of the modified acrylic resin and azole silane modified pigment in this embodiment are the same as those in Embodiment 1, and specific reference is made to Embodiment 1.

[0067] The filler is composed of organic bentonite and nano-montmorillonite in a mass ratio of 2:1.

[0068] Example 3

[0069] The preparation method of the non-sedimentation and non-precipitation colored electrophoretic coating of Example 2 is as follows:

[0070] (1) Add 10 parts of PPG2000 and 15 parts of filler into a container and mix them. Then, under vacuum conditions at a temperature of 110°C, stir and disperse them while dehydrating for 2 hours. Then, cool the temperature to below 50°C and release the vacuum.

[0071] (2) then adding 42 parts of waterborne polyurethane resin and 3.8 parts of zinc dihydrogen phosphate, stirring at room temperature and pressure for 15 minutes;

[0072] (3) Then, 1.6 parts of dibutyltin dilaurate, 1.8 parts of phthalate coupling agent KR-12, 16 parts of color paste and 9.8 parts of deionized water were added in sequence, stirred for 30 minutes, and vacuum degassed for 10 minutes. After the vacuum was released, a colored electrophoretic coating without sedimentation or precipitation was obtained.

[0073] The preparation method of the above waterborne polyurethane resin is as follows:

[0074] 1 kg of polytrimethylene ether glycol and 240 g of polypropylene glycol are added to a container, and the container is evacuated at 110° C. for 1.5 hours, then the vacuum is released and nitrogen is introduced, the temperature is lowered to 60° C., 1.3 g of dibutyltin dilaurate, 336 g of hexamethylene diisocyanate and 160 g of dithioglycolic acid are added, and the temperature is raised to 90° C. for reaction for 3 hours to obtain a prepolymer; 33.4 g of polytetrahydrofuran diol is added to the prepolymer, the reaction is continued at 90° C. for 3 hours, then the temperature is lowered to 70° C., 134.4 g of terminal hydroxyl polydimethylsiloxane is added, the temperature is kept for 5 hours, naturally cooled and evacuated for 10 minutes to obtain a waterborne polyurethane resin.

[0075] The color paste is composed of the following components in parts by weight: 28 parts of modified acrylic resin, 19 parts of azole silane modified pigment, 10 parts of cardanol polyoxyethylene ether and 28 parts of deionized water.

[0076] The composition and preparation method of the modified acrylic resin and azole silane modified pigment in this embodiment are the same as those in Embodiment 1, and specific reference is made to Embodiment 1.

[0077] The filler is composed of organic bentonite and nano-montmorillonite in a mass ratio of 2:1.

[0078] Comparative Example 1

[0079] The components and preparation method of the colored electrophoretic coating of this comparative example are the same as those of Example 3, except that dithioglycolic acid is not added during the preparation of the waterborne polyurethane resin in this comparative example 1.

[0080] Comparative Example 2

[0081] The components and preparation method of the colored electrophoretic coating of this comparative example are the same as those in Example 3, except that ethylenediamine is used in this comparative example 2 to replace polytetrahydrofuran diol.

[0082] Comparative Example 3

[0083] The components and preparation method of the colored electrophoretic coating of this comparative example are the same as those of Example 3, except that the acrylic resin is not modified in this comparative example 3, that is, the acrylic resin is selected from the water-based acrylic resin AC-397 produced by Sansheng Chemical.

[0084] Comparative Example 4

[0085] The components and preparation method of the colored electrophoretic coating of this comparative example are the same as those of Example 3, except that no dialkylamidopropyl polyhydroxy quaternary ammonium salt is added during the preparation of the modified acrylic resin in this comparative example 4.

[0086] Comparative Example 5

[0087] The components and preparation method of the colored electrophoretic coating of this comparative example are the same as those of Example 3, except that the pigment in this comparative example 5 is not modified, that is, the pigment is directly added to the electrophoretic coating.

[0088] Comparative Example 6

[0089] The components and preparation method of the colored electrophoretic coating of this comparative example are the same as those in Example 3, except that the pigment in this comparative example 6 is modified with a silane coupling agent KH-550, that is, the silane-modified pigment is mixed with 9 parts of a silane coupling agent KH-550, 5 parts of a wetting agent TEGO and 86 parts of a pigment (Permanent Red 1701 is selected).

[0090] Comparative Example 7

[0091] The components and preparation method of the colored electrophoretic coating of this comparative example are the same as those of Example 3, except that the filler in this comparative example 7 is nano-montmorillonite.

[0092] Comparative Example 8

[0093] The components and preparation method of the colored electrophoretic coating of this comparative example are the same as those of Example 3, except that zinc dihydrogen phosphate is not added in this comparative example 8.

[0094] The colored electrophoretic coatings prepared in the above Examples 1-3 and Comparative Examples 1-8 were made into electrophoretic paint films, and the film making conditions were as follows: electrophoretic temperature 28°C, voltage 120V, electrophoretic time 3min, baking at 170°C for 30min after the electrophoresis, and film thickness 20μm. The properties of the formed paint films were tested respectively, and the test results are shown in Table 1 below.

[0095] Storage stability of colored electrophoretic coatings:

[0096] Desktop centrifuge test, test conditions: test temperature 25 ℃, speed 3000r / min, centrifugal time 30min, observe whether stratification and precipitation occur at the end of the test; if there is no stratification and precipitation, it is considered that the emulsion can be stably stored for more than 180 days.

[0097] Adhesion test: Tested in accordance with GB / T 9286-1998 "Scratch test for paint and varnish films";

[0098] Aging resistance: According to GB / T 1865-1997 test standard;

[0099] Salt spray resistance: tested according to GB / T1771-2007;

[0100] Acetone wiping resistance: tested according to GB / T 23989-2009;

[0101] Moisture and heat resistance: The samples were processed according to GB / T2423.50-2012, 85℃, 85% rh, 1000h, and the adhesion of the samples was tested after the double 85 test.

[0102] Table 1 Performance test results of colored electrophoretic coatings

[0103]

[0104]

[0105] It can be seen from the test results of Table 1 that the colored electrophoretic coating of the present invention has excellent anti-precipitation, adhesion, aging resistance, water resistance, high temperature resistance, solvent resistance, salt spray resistance, etc.; the use of the waterborne polyurethane resin of the present invention significantly improves the adhesion, water resistance and solvent resistance of the present invention; the use of the color paste of the present invention significantly improves the anti-precipitation, adhesion, aging resistance, water resistance, high temperature resistance, solvent resistance and salt spray resistance of the present invention; the use of the filler combination of the present invention can improve the anti-precipitation, adhesion and salt spray resistance of the present invention.

[0106] It is worth noting that in the embodiments of the present invention, only one specific component of each component is selected for analysis. In fact, other components or models not mentioned in the present invention can also be selected.

[0107] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0108] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A non-sedimentation and non-precipitation colored electrophoretic coating, characterized in that: The invention comprises the following components in parts by weight: 30-45 parts of waterborne polyurethane resin, 8-12 parts of polyether polyol, 2-4 parts of zinc dihydrogen phosphate, 5-20 parts of filler, 1-2.5 parts of catalyst, 1-3 parts of phthalate coupling agent, 8-20 parts of color paste and 5-30 parts of deionized water; The color paste comprises the following components in parts by weight: 15-35 parts of modified acrylic resin, 10-25 parts of azole silane modified pigment, 5-10 parts of cardanol polyoxyethylene ether and 20-40 parts of deionized water.

2. The non-sedimentation and non-precipitation colored electrophoretic coating according to claim 1, characterized in that: The preparation method of the waterborne polyurethane resin specifically comprises the following steps: S1. Add polytrimethylene ether glycol and polypropylene glycol to a container, evacuate at 100-120°C for 0.5-1.5h, then release the vacuum and introduce nitrogen, cool to 50-60°C, add dibutyltin dilaurate, hexamethylene diisocyanate and dithioglycolic acid, and heat to 80-90°C for reaction for 2-4h to obtain a prepolymer; P2. Add polytetrahydrofuran diol to the above prepolymer, continue to react at 80-90°C for 2-3h, then cool to 65-75°C, add terminal hydroxyl polydimethylsiloxane, keep warm for 3-6h or until the -NCO content is determined to be ≤0.1%, cool naturally and evacuate for 5-10min to obtain a waterborne polyurethane resin.

3. The non-sedimentation and non-precipitation colored electrophoretic coating according to claim 2, characterized in that: The molar ratio of -NCO in the hexamethylene diisocyanate to -OH in the polytrimethylene ether glycol is (1.5-2.5):1; The amount of polypropylene glycol added is 12-20% of the total mass of hexamethylene diisocyanate and polytrimethylene ether glycol; The amount of dibutyltin dilaurate added is 0.05-0.12% of the total mass of hexamethylene diisocyanate and polytrimethylene ether glycol; The amount of dithioglycolic acid added is 10-15% of the total mass of the hexamethylene diisocyanate and polytrimethylene ether glycol; The amount of the polytetrahydrofuran diol added is 2.0-2.8% of the total mass of the hexamethylene diisocyanate and the cardanol-based polyol; The mass ratio of the terminal hydroxyl polydimethylsiloxane to the hexamethylene diisocyanate is 1:(0.3-0.5).

4. The non-sedimentation and non-precipitation colored electrophoretic coating according to claim 1, characterized in that: The polyether polyol is any one of PPG2000, PPG3000 or PPG4000.

5. The non-sedimentation and non-precipitation colored electrophoretic coating according to claim 1, characterized in that: The filler is composed of organic bentonite and nano-montmorillonite in a mass ratio of (1.2-2.0):

1.

6. The non-sedimentation and non-precipitation colored electrophoretic coating according to claim 1, characterized in that: The preparation method of the modified acrylic resin comprises the following steps: P1. First, add 1 / 2 mass of tri-n-butyl borane to an appropriate amount of ethylene glycol butyl ether to dissolve completely, then add it to the reactor and heat it to 60-70℃; P2. Weigh the acrylic monomer, polycarbodiimide and the remaining tri-n-butylborane according to the formula, mix them evenly, and then add them dropwise to the reactor at a uniform speed within 1 hour, control the reaction temperature at 70-80°C, keep warm for 2-4 hours, and then add alkylamide propyl polyhydroxy quaternary ammonium salt dropwise, the addition time is controlled within 30 minutes, and react for 2-4 hours; P3. After the reaction is completed, the temperature of the reactor is lowered to 40°C, and aqueous ammonia is added while stirring for neutralization. The reaction is stirred for 15-25 minutes, and then cooled to room temperature to obtain a modified acrylic resin.

7. The non-sedimentation and non-precipitation colored electrophoretic coating according to claim 6, characterized in that: The modified acrylic resin is composed of the following raw materials in parts by weight: 82-90 parts of acrylic monomer, 10-20 parts of alkylamide propyl polyhydroxy quaternary ammonium salt, 2-5 parts of tri-n-butyl borane and 3-6 parts of polycarbodiimide.

8. The non-sedimentation and non-precipitation colored electrophoretic coating according to claim 7, characterized in that: The acrylic monomer is composed of the following monomers in parts by weight: 25-40 parts of methyl methacrylate, 16-24 parts of lauryl acrylate, 8-20 parts of acrylic acid, 20-28 parts of acetic anhydride and 3-5 parts of hydroxy acrylic acid.

9. The non-sedimentation and non-precipitation colored electrophoretic coating according to claim 1, characterized in that: The azole silane modified pigment is prepared by uniformly mixing 5-10 parts of triazole silane compound, 3-6 parts of wetting agent TEGO and 84-92 parts of pigment.

10. A method for preparing a non-sedimentation and non-precipitation colored electrophoretic coating according to any one of claims 1 to 9, characterized in that: The specific steps include: (1) After adding polyether polyol and filler into a container and mixing, the mixture is stirred and dispersed for 1-2 hours under vacuum conditions at a temperature of 110° C. to 120° C. while dehydrating, and then the vacuum is released after the temperature is lowered to below 50° C.; (2) then adding waterborne polyurethane resin and zinc dihydrogen phosphate, stirring for 10-20 minutes at room temperature and pressure; (3) Then add the catalyst, phthalate coupling agent, color paste and deionized water in sequence, stir for 20-30 minutes, vacuum degassing for 5-10 minutes, and release the vacuum to obtain a colored electrophoretic coating without sedimentation or precipitation.

Images