Cationic aqueous dispersion emulsion containing N, N-dimethyl semicarbazide modified epoxy resin as well as preparation method and application of cationic aqueous dispersion emulsion

Abstract

The invention relates to a cationic aqueous dispersion emulsion containing N, N-dimethyl semicarbazide modified epoxy resin, which is prepared from the following components in parts by weight: 50 to 70 parts of organic acid modified epoxy resin, 10 to 35 parts of low-temperature blocked isocyanate curing agent, 2 to 10 parts of amine compound, 0.5 to 8 parts of solvent A, 0.5 to 3 parts of defoaming agent, 100 to 200 parts of pure water and 0.5 to 5 parts of acid. According to the cationic aqueous dispersion emulsion containing the N, N-dimethyl semicarbazide modified epoxy resin, the aliphatic blocked isocyanate is added for blocking, so that the risk of yellowing of a coating film in the baking process is reduced. An electrophoretic coating prepared from the cationic aqueous dispersion emulsion is environmentally friendly and healthy and does not contain heavy metal tin compounds, and a coating film has the advantages of being good in anti-yellowing performance, high in hardness, excellent in appearance and the like. The invention also relates to a preparation method and application of the cationic aqueous dispersion emulsion containing the N, N-dimethyl semicarbazide modified epoxy resin.

Description

Technical Field

[0001] The invention relates to the technical field of coatings, and in particular to a cationic aqueous dispersion emulsion containing N,N-dimethylaminourea modified epoxy resin, and a preparation method and application thereof. Background Art

[0002] Traditional electrophoretic coatings will yellow to varying degrees during the baking process, affecting the appearance. For double-layer coatings, if powder coating is applied on the electrophoretic surface, the baking of the powder coating will cause the workpiece area that is not sprayed on the electrophoretic part to turn yellow seriously, resulting in a large color difference and affecting the overall quality of the product.

[0003] In the prior art, the above-mentioned problem is generally solved by adding an anti-yellowing agent to the coating formula. For example, as mentioned in Example 20 of patent US5817732, a compound HN-130 containing a semicarbazide group is added to the non-aqueous formula, and then sprayed. Although this is applicable in the spray system, it is very risky and has a poor effect in the electrophoretic system. Since the production of electrophoretic products is completely different from topcoat and powder coating, its coating process generally contains the steps of surface treatment electrophoresis UF three-way washing, pure water washing, drying and baking. The anti-yellowing agent added in the traditional method mainly exists in a non-ionic state, which will be completely washed away during the washing stage, not only failing to achieve the anti-yellowing effect, but also causing abnormal adhesion, appearance, acid and alkali resistance and salt spray resistance of the coating film. At the same time, the deposition in the UF cleaning tank will cause defects in the electrophoretic wet film during the spraying process. Therefore, in order to achieve cross-linking and curing, the traditional electrophoretic coating market often adopts the method of adding a large amount of organic tin to solve the above-mentioned problems, but this method will bring very serious pollution.

[0004] In view of the above reasons, in order to respond to the country's call for the "Blue Sky Defense War" and at the same time lead the coatings industry to develop in a green and environmentally friendly direction, the field urgently needs to develop an environmentally friendly electrophoretic coating that is free of heavy metal tin and has excellent anti-yellowing effect to solve the problems faced in the existing coatings technology field. Summary of the invention

[0005] Based on the above facts, the purpose of the present invention is to provide a cationic aqueous dispersion emulsion containing N,N-dimethylaminourea modified epoxy resin, which does not contain heavy metal tin, modifies hydrogenated epoxy resin by N,N-dimethylaminourea, and carries out chain growth and chain termination by a composite method of symmetrical carboxylic diacids and monocarboxylic acids, thereby ensuring surface leveling and fullness during the system coating film formation process. The cationic aqueous dispersion emulsion has excellent anti-yellowing performance and can meet environmental protection requirements at the same time. The present invention also relates to a preparation method and application of the above-mentioned cationic aqueous dispersion emulsion containing N,N-dimethylaminourea modified epoxy resin.

[0006] The first aspect of the present invention provides a cationic aqueous dispersion emulsion containing N,N-dimethylaminourea modified epoxy resin, and its components include, by weight:

[0007]

[0008] Organic acid modified epoxy resin

[0009] In the present invention, the organic acid-modified epoxy resin comprises the following components in parts by weight:

[0010]

[0011] The preparation of the organic acid-modified epoxy resin comprises the following steps:

[0012] S1: Add epoxy resin and solvent B to a three-necked flask equipped with a stirrer, a condenser, and a thermometer, turn on the heating, slowly drop N,N-dimethylaminourea during the heating process, stop heating when the temperature rises to 120°C, and keep warm for 1 hour;

[0013] S2: Add an alkaline catalyst into the flask, continue heating to 140° C., add organic acid A and organic acid B, maintain the temperature between 140-150° C. for reaction for 1-3 hours, and when the epoxy equivalent is 1300±10 g / equivalent at the reaction endpoint, the organic acid-modified epoxy resin is obtained.

[0014] Epoxy resin

[0015] In the present invention, the epoxy equivalent of the epoxy resin is 600-800 g / equivalent.

[0016] In some embodiments of the present invention, the epoxy resin is selected from one or more of hydrogenated bisphenol A epoxy resin and hydrogenated bisphenol F epoxy resin; further, the epoxy resin is selected from a combination of hydrogenated bisphenol A epoxy resin and hydrogenated bisphenol F epoxy resin with different molecular weights.

[0017] In some preferred embodiments of the present invention, the epoxy resin is hydrogenated bisphenol A epoxy resin. Hydrogenated bisphenol A epoxy resin has stable output and higher cost performance.

[0018] N,N-Dimethylaminourea

[0019] In the present invention, the N,N-dimethylaminourea is reacted in a slow reaction branching manner. After the branching is successful, an aliphatic blocked isocyanate is used as the resin curing system to prevent the problem of yellowing of the coating surface caused by the formation of NOx due to chain breakage of the resin system during high temperature and over-baking. By adopting a method of simultaneous chain growth and chain termination, a good long-chain and short-chain composite is achieved, making the coating plump and having a higher hardness.

[0020] Organic acids A and B

[0021] In the present invention, the organic acid A and the organic acid B may be organic acid monomers known to those skilled in the art as raw materials for synthetic resins, and may be acids with one or more unsaturated double bonds.

[0022] In some embodiments of the present invention, the organic acid A is a dicarboxylic acid organic acid for chain growth, and the organic acid B is a chain termination. Specifically, the organic acid A is selected from one or more of adipic acid, oxalic acid, malonic acid, and succinic acid, and the organic acid B is selected from one or more of formic acid, acetic acid, octanoic acid, and isooctanoic acid.

[0023] Solvent B

[0024] In the present invention, the solvent B is selected from one or more of alcohol solvents and alcohol ether solvents.

[0025] Specifically, the alcohol solvent includes but is not limited to isopropanol, n-butanol, isobutanol, n-hexanol, isooctyl alcohol, ethylene glycol or propylene glycol; the alcohol ether solvent includes but is not limited to ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol butyl ether, ethylene glycol hexyl ether, diethylene glycol butyl ether, ethylene glycol isooctyl ether, propylene glycol methyl ether or propylene glycol phenyl ether.

[0026] Basic catalyst

[0027] In the present invention, the alkaline catalyst includes but is not limited to N,N-dimethylbenzylamine, triethylamine, dimethylaminopropylamine, dimethylaminobutylamine, diethylaminopropylamine, triethanolamine, and tetramethylammonium chloride.

[0028] Low temperature blocked isocyanate curing agent

[0029] In the present invention, the low-temperature blocked isocyanate curing agent comprises the following components in parts by weight:

[0030]

[0031]

[0032] The preparation of the low-temperature blocked isocyanate curing agent comprises the following steps:

[0033] S1: In a four-necked flask with a condenser and nitrogen protection, add isocyanate and some inert solvent, and heat to 30°C;

[0034] S2: Add low-temperature sealing agent dropwise into the flask, the temperature is controlled at 50±3°C during the addition process, and the NCO equivalent is controlled at 230-270 g / mol;

[0035] S3: Add solvent C into the flask, raise the temperature to 90°C after the addition, and keep it at 90±3°C for 1 hour, and control the NCO equivalent to >42000 g / mol;

[0036] S4: adding the remaining inert solvent into the flask and controlling the solid content to be 80±2% to obtain the low-temperature blocked isocyanate curing agent.

[0037] It should be noted that in the present invention, the low-temperature blocked isocyanate curing agent is blocked with an aliphatic ether alcohol blocking agent, and the isocyanate group equivalent is greater than 42000 g / mol. The preparation process does not use a catalyst containing heavy metal tin, and the prepared low-temperature blocked isocyanate curing agent does not contain heavy metal tin, which is more environmentally friendly.

[0038] Isocyanate

[0039] In some embodiments of the present invention, the isocyanate is selected from one or more of aliphatic polyisocyanates and alicyclic polyisocyanates.

[0040] Specifically, the aliphatic polyisocyanate includes but is not limited to 1,4-butyl diisocyanate or hexamethylene diisocyanate; the alicyclic polyisocyanate includes but is not limited to 1,3-cyclopentane diisocyanate, 1,4-cyclohexane diisocyanate or isophorone diisocyanate.

[0041] Inert solvent

[0042] In some embodiments of the present invention, the inert solvent is selected from one or more of methyl isobutyl ketone, acetone, and tetrahydrofuran.

[0043] Low temperature sealant

[0044] In some embodiments of the present invention, the low-temperature sealing agent is an aliphatic substance with active hydrogen.

[0045] Specifically, the low-temperature sealing agent is selected from one or more of ethylene glycol, propylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol butyl ether, ethylene glycol hexyl ether, diethylene glycol butyl ether, propylene glycol methyl ether, and isooctyl alcohol.

[0046] Solvent C

[0047] In some embodiments of the present invention, the solvent C is selected from one or more of ethylene glycol monomethyl ether, ethylene glycol, isooctyl alcohol, and propylene glycol.

[0048] Amine compounds

[0049] In the present invention, the amine compound is selected from one or more of diethanolamine, ketimine, methyldiethanolamine, diethylenetriamine, di-n-butylamine and triethanolamine.

[0050] Solvent A

[0051] In the present invention, the solvent A is selected from one or more of ethylene glycol, propylene glycol phenyl ether, ethylene glycol butyl ether, and propylene glycol.

[0052] The second aspect of the present invention provides a method for preparing the cationic aqueous dispersion emulsion containing N,N-dimethylaminourea modified epoxy resin according to the first aspect of the present invention, comprising the following steps:

[0053] (1) Preparation of amine-modified epoxy resin polymer

[0054] S1: Add an organic acid-modified epoxy resin to a three-necked flask equipped with a stirrer, a condenser, and a thermometer, and when the temperature drops to 90° C., add an amine compound, a low-temperature blocked isocyanate curing agent, and solvent A;

[0055] S2: heating the mixture to 105-110° C. and keeping the temperature for 1-3 hours to obtain the amine-modified epoxy resin polymer.

[0056] (2) Preparation of cationic aqueous dispersion emulsion

[0057] S1: adding part of pure water and acid into the dropping kettle, adjusting the acid value to 50-70 mgKOH / g, and obtaining acid water;

[0058] S2: stirring the amine-modified epoxy resin polymer at a high speed of 800-1000 rpm, and adding a defoaming agent under stirring;

[0059] S3: Keep stirring, add acid water to the amine-modified epoxy resin polymer, and control the dropping speed to ensure that the dropping time is 1 hour;

[0060] S4: After the dropwise addition is completed, stirring is performed at a speed of 800-1000 rpm for 60 minutes, the remaining pure water is added twice, and high-speed dispersion is continued at 30° C. for 2 hours. The cationic aqueous dispersion emulsion containing the N,N-dimethylaminourea modified epoxy resin is obtained by filtering.

[0061] In some embodiments of the present invention, the acid in the preparation process is selected from one or more organic acids or inorganic acids, the organic acid is preferably one or more of acetic acid, aminosulfonic acid, formic acid, lactic acid, and citric acid, and the inorganic acid is preferably nitric acid.

[0062] The third aspect of the present invention provides an application of the cationic aqueous dispersion emulsion containing N,N-dimethylaminourea modified epoxy resin according to the first aspect of the present invention, wherein the application is embodied as an anti-yellowing electrophoretic coating, and the components thereof comprise, by weight:

[0063] 40-50 parts of cationic aqueous dispersion containing N,N-dimethylaminourea modified epoxy resin

[0064] Color paste 9-10 parts

[0065] 40-80 parts of pure water

[0066] The total content of the above components is 100 parts.

[0067] Specifically, the preparation of the anti-yellowing electrophoretic coating comprises the following steps:

[0068] The cationic aqueous dispersion emulsion containing N,N-dimethylaminourea modified epoxy resin, color paste and pure water are mixed and stirred evenly to obtain the anti-yellowing electrophoretic coating.

[0069] The beneficial effects of the present invention are as follows:

[0070] The cationic aqueous dispersion emulsion containing N,N-dimethylaminourea modified hydrogenated epoxy resin provided by the present invention is blocked by adding aliphatic blocked isocyanate after amine modification, thereby reducing the risk of yellowing of the coating during baking, and solving the problem of increased color difference caused by baking with topcoat or powder coating. At the same time, the present invention uses a symmetrical structure several times during the preparation process, so that chain extension and chain termination are carried out simultaneously, and the reference of long and short chains ensures the improvement of the hardness of the coating and also improves the fullness of the coating. There is no artificial addition of heavy metal organotin substances in the preparation process of the entire invention, which is environmentally friendly and healthy, and has good stability. During storage at 40°C for 4 weeks, no abnormal phenomena such as precipitation and emulsion decomposition occur, which can meet the requirements of the coating for export to the European Union or domestic high-standard enterprises. DETAILED DESCRIPTION

[0071] In order to more clearly illustrate the present invention, the present invention is further described below in conjunction with specific examples and comparative examples. It should be understood by those skilled in the art that the content specifically described below is illustrative rather than restrictive, and should not be used to limit the scope of protection of the present invention. The experimental methods used in the following examples and comparative examples are conventional methods unless otherwise specified, and the raw materials and reagents used are products that can be purchased from conventional commercial channels unless otherwise specified.

[0072] The above technical scheme is described below in conjunction with specific examples. In the case where the purpose of the present invention is illustrated and explained by the following examples, the components of the composition are explained in parts by weight as a general standard. Unless otherwise specified, for the sake of simplicity, the "parts" described in the examples of the present invention and the comparative examples have the same meaning as parts by weight.

[0073] Example 1: Cationic aqueous dispersion emulsion 1 containing N,N-dimethylaminourea modified hydrogenated epoxy resin

[0074] The cationic aqueous dispersion emulsion 1 containing N,N-dimethylaminourea modified hydrogenated epoxy resin of the present invention is prepared according to Table 1 and the following steps:

[0075] Table 1 Formula of cationic aqueous dispersion emulsion 1 containing N,N-dimethylaminourea modified hydrogenated epoxy resin

[0076]

[0077] (1) Preparation of 1738.9 g of amine-modified epoxy resin polymer

[0078] S1: Add 1028.1g of organic acid-modified epoxy resin to a three-necked flask equipped with a stirrer, a condenser and a thermometer (purchased from Shanghai Gaoxin Chemical Glass Co., Ltd. or Collings Company), and when the temperature drops to 90°C, add 55.2g of diethanolamine (purchased from Tianjin CITIC Kaitai Chemical Co., Ltd., purity 98%), 60.3g of ketimine (purchased from Nippon Paint (China) Co., Ltd.), and 575.8g of low-temperature blocked isocyanate curing agent, and rinse the kettle wall with 19.5g of ethylene glycol butyl ether;

[0079] S2: heating the mixture to 105-110° C. and keeping the temperature for 2 hours to obtain the amine-modified epoxy resin polymer.

[0080] (2) Preparation of cationic aqueous dispersion emulsion

[0081] S1: Add 1139.2g of pure water and 30.05g of acetic acid into the dropping kettle, adjust the acid value to 50-70mgKOH / g, and obtain acid water;

[0082] S2: The amine-modified epoxy resin polymer was stirred at a high speed of 800-1000 rpm, and 23.5 g of Airase 5700 silicone water-based defoamer (purchased from Evonik Specialty Chemicals (Shanghai) Co., Ltd.) was added under stirring;

[0083] S3: keep stirring, add acid water to the amine-modified epoxy resin polymer, and control the dropping speed to ensure that the dropping time is 1 hour;

[0084] S4: After the dropwise addition is completed, the mixture is stirred at a speed of 800-1000 rpm for 60 min, 432.1 g and 1412.5 g of pure water are added twice, and high-speed dispersion is continued at 30° C. for 2 hours. The cationic aqueous dispersion emulsion 1 containing the N,N-dimethylaminourea modified epoxy resin is obtained by filtration.

[0085] It should be noted that the technical indicators of the cationic aqueous dispersion emulsion 1 containing N,N-dimethylaminourea modified epoxy resin prepared in the above steps are: solid content 36±2%, particle size ≤90nm, and pH controlled at 6.3±0.3.

[0086] The preparation process and related parameters of the 1028.1 g organic acid-modified epoxy resin are as follows:

[0087] S1: Add 644.1g of hydrogenated bisphenol A epoxy resin (the starting epoxy equivalent of the epoxy resin is 600-750 g / equivalent) and 45.5g of ethylene glycol butyl ether (purchased from J&K Technology Co., Ltd., purity 99.5%) to a three-necked flask equipped with a stirrer, a condenser and a thermometer (purchased from Shanghai Gaoxin Chemical Glass Co., Ltd. or Collings), turn on the heating, slowly add 298.5g of N,N-dimethylaminourea (purchased from Wuhan Shuer Biotechnology Co., Ltd.), raise the temperature to 120°C, stop heating, and keep warm for 1h;

[0088] S2: Add 0.1g N,N-dimethylbenzylamine (purchased from Tianjin CITIC Kaitai Chemical Co., Ltd., purity 98%) into the flask, continue heating to 140°C, add 22g adipic acid (purchased from Tai'an Jiaye Biotechnology Co., Ltd.) and 17.9g isooctanoic acid, maintain the temperature at 140-150°C, react for 1-3 hours, and the epoxy equivalent detected at the reaction endpoint is 1300±10 g / equivalent, which is qualified, and the organic acid modified epoxy resin is obtained.

[0089] The preparation process and related parameters of the 575.8 g low-temperature blocked isocyanate curing agent are as follows:

[0090] S1: In a four-necked flask with a condenser and nitrogen protection (purchased from Shanghai Gaoxin Chemical Glass Co., Ltd. or Collings), add 274.6g of isophorone diisocyanate (purchased from Wanhua Chemical Group Co., Ltd.) and 63.7g of methyl isobutyl ketone (purchased from Jinan Century Tongda Chemical Co., Ltd.), and heat to 30°C;

[0091] S2: 149.1 g of ethylene glycol blocking agent (purchased from Nantong Yida Chemical Co., Ltd.) was added dropwise into the flask, the temperature was controlled at 50 ± 3 °C, and the NCO equivalent was controlled at 230-270 g / mol;

[0092] S3: 71.5 g of ethylene glycol butyl ether (purchased from Jinan Century Tongda Chemical Co., Ltd.) was added to the flask. After the addition, the temperature was raised to 90° C. and kept at 90±3° C. for 1 hour. The NCO equivalent was measured to be 123240 g / mol, and the result was >42000 g / mol;

[0093] S4: 16.9 g of methyl isobutyl ketone (purchased from Jinan Century Tongda Chemical Co., Ltd.) was added into the flask, and the solid content was controlled at 80±2% to obtain the low-temperature blocked isocyanate curing agent.

[0094] Example 2: Cationic aqueous dispersion emulsion 2 containing N,N-dimethylaminourea modified hydrogenated epoxy resin

[0095] The cationic aqueous dispersion emulsion 2 containing N,N-dimethylaminourea modified hydrogenated epoxy resin of the present invention is prepared according to Table 2 and the following steps:

[0096] Table 2 Formula of cationic aqueous dispersion emulsion 2 containing N,N-dimethylaminourea modified hydrogenated epoxy resin

[0097]

[0098] (1) Preparation of 1626 g of amine-modified epoxy resin polymer

[0099] S1: Add 998.5g of organic acid-modified epoxy resin to a three-necked flask equipped with a stirrer, a condenser and a thermometer (purchased from Shanghai Gaoxin Chemical Glass Co., Ltd. or Collings Company), and when the temperature drops to 90°C, add 42.3g of methyldiethanolamine (purchased from Tianjin CITIC Kaitai Chemical Co., Ltd., purity 98%), 52.1g of ketimine (purchased from Nippon Paint (China) Co., Ltd.), and 515.3g of low-temperature blocked isocyanate curing agent, and rinse the kettle wall with 17.8g of ethylene glycol butyl ether;

[0100] S2: heating the mixture to 105-110° C. and keeping the temperature for 2 hours to obtain the amine-modified epoxy resin polymer.

[0101] (2) Preparation of cationic aqueous dispersion emulsion

[0102] S1: Add 1002.2g of pure water and 19.85g of acetic acid into the dropping kettle, adjust the acid value to 50-70mgKOH / g, and obtain acid water;

[0103] S2: The amine-modified epoxy resin polymer was stirred at a high speed of 800-1000 rpm, and 15.7 g of Airase 5700 silicone water-based defoamer (purchased from Evonik Specialty Chemicals (Shanghai) Co., Ltd.) was added under stirring;

[0104] S3: Keep stirring, add acid water to the amine-modified epoxy resin polymer, and control the dropping speed to ensure that the dropping time is 1 hour;

[0105] S4: After the dropwise addition is completed, the mixture is stirred at a speed of 800-1000 rpm for 60 min, 375.1 g and 1432.4 g of pure water are added twice, and high-speed dispersion is continued at 30° C. for 2 hours. The cationic aqueous dispersion emulsion 2 containing N,N-dimethylaminourea-modified epoxy resin is obtained by filtration.

[0106] It should be noted that the technical indicators of the cationic aqueous dispersion emulsion 2 containing N,N-dimethylaminourea modified epoxy resin prepared in the above steps are: solid content 36±2%, particle size ≤90nm, and pH controlled at 6.3±0.3.

[0107] The preparation process and related parameters of the 998.5 g organic acid-modified epoxy resin are as follows:

[0108] S1: Add 631.4 g of hydrogenated bisphenol A epoxy resin (the starting epoxy equivalent of the epoxy resin is 600-750 g / equivalent) and 50.1 g of ethylene glycol butyl ether (purchased from J&K Technology Co., Ltd., purity 99.5%) to a three-necked flask equipped with a stirrer, a condenser, and a thermometer (purchased from Shanghai Gaoxin Chemical Glass Co., Ltd. or Collings), turn on the heating, slowly add 262.3 g of N, N-dimethylaminourea (purchased from Wuhan Shuer Biotechnology Co., Ltd.), raise the temperature to 120°C, stop heating, and keep warm for 1 hour;

[0109] S2: Add 0.1g N,N-dimethylbenzylamine (purchased from Tianjin CITIC Kaitai Chemical Co., Ltd., purity 98%) into the flask, continue heating to 140°C, add 33.9g adipic acid (purchased from Tai'an Jiaye Biotechnology Co., Ltd.) and 20.7g acetic acid, maintain the temperature at 140-150°C, react for 1-3 hours, and the epoxy equivalent detected at the reaction endpoint is 1300±10 g / equivalent, which is qualified, and the organic acid modified epoxy resin is obtained.

[0110] The preparation process and related parameters of the 515.3 g low-temperature blocked isocyanate curing agent are as follows:

[0111] S1: In a four-necked flask with a condenser and nitrogen protection (purchased from Shanghai Gaoxin Chemical Glass Co., Ltd. or Collings), add 250.6g of hexamethylene diisocyanate (purchased from Jinan Hongwang Chemical Co., Ltd.) and 54.4g of methyl isobutyl ketone (purchased from Jinan Century Tongda Chemical Co., Ltd.), and heat to 30°C;

[0112] S2: 129.9 g of propylene glycol blocking agent (purchased from Nantong Yida Chemical Co., Ltd.) was added dropwise into the flask, the temperature was controlled at 50 ± 3 ° C, and the NCO equivalent was controlled at 230-270 g / mol;

[0113] S3: 62.3 g of ethylene glycol isooctyl ether (purchased from Jiangsu Yida Chemical Co., Ltd.) was added to the flask. After the addition, the temperature was raised to 90° C. and kept at 90±3° C. for 1 hour. The NCO equivalent was measured to be 156320 g / mol, which was >42000 g / mol.

[0114] S4: Add 18.1 g of methyl isobutyl ketone (purchased from Jinan Century Tongda Chemical Co., Ltd.) into the flask, and control the solid content to 80±2% to obtain the low-temperature blocked isocyanate curing agent.

[0115] Comparative Example 1: Emulsion 1 as a comparative example

[0116] Emulsion 1 as a comparative example was prepared according to Table 3 and the following steps:

[0117] Table 3 Formula of emulsion 1 as comparative example

[0118]

[0119]

[0120] (1) Preparation of amine-modified epoxy resin polymer 1936.3 g

[0121] S1: Add 1184.2g of organic acid-modified epoxy resin to a three-necked flask equipped with a stirrer, a condenser and a thermometer (purchased from Shanghai Gaoxin Chemical Glass Co., Ltd. or Collings Company), and when the temperature drops to 90°C, add 53g of diethanolamine (purchased from Tianjin CITIC Kaitai Chemical Co., Ltd., purity 98%) and 60g of ketimine (purchased from Nippon Paint (China) Co., Ltd.); add 613g of low-temperature blocked isocyanate curing agent, and rinse the kettle wall with 26.1g of ethylene glycol butyl ether;

[0122] S2: heating the mixture to 105-110° C. and keeping the temperature for 2 hours to obtain the amine-modified epoxy resin polymer.

[0123] (2) Preparation of cationic aqueous dispersion emulsion

[0124] S1: Add 1013.2g of pure water and 20.05g of acetic acid into the dropping kettle, adjust the acid value to 50-70mgKOH / g, and obtain acid water;

[0125] S2: The amine-modified epoxy resin polymer was stirred at a high speed of 800-1000 rpm, and 14.5 g of Airase 5700 silicone water-based defoamer (purchased from Evonik Specialty Chemicals (Shanghai) Co., Ltd.) was added under stirring;

[0126] S3: Keep stirring, add acid water to the amine-modified epoxy resin polymer, and control the dropping speed to ensure that the dropping time is 1 hour;

[0127] S4: After the dropwise addition was completed, the mixture was stirred at a speed of 800-1000 rpm for 60 min, 406.1 g and 1211.5 g of pure water were added twice, and high-speed dispersion was continued at 30° C. for 2 hours. The emulsion 1 as a comparative example was obtained by filtration.

[0128] It should be noted that the technical indicators of the emulsion 1 as a comparative example prepared in the above steps are: solid content 36±2%, particle size ≤90nm, and pH controlled at 6.3±0.3.

[0129] The preparation process and related parameters of the 1184.2 g organic acid-modified epoxy resin are as follows:

[0130] S1: Add 1068.1 g of hydrogenated bisphenol A epoxy resin (the starting epoxy equivalent of the epoxy resin is 600-750 g / equivalent) and 60.2 g of ethylene glycol butyl ether (purchased from J&K Technology Co., Ltd., purity 99.5%) into a three-necked flask equipped with a stirrer, a condenser and a thermometer (purchased from Shanghai Gaoxin Chemical Glass Co., Ltd. or Collings), and start heating;

[0131] S2: Add 0.1g N,N-dimethylbenzylamine (purchased from Tianjin CITIC Kaitai Chemical Co., Ltd., purity 98%) into the flask, continue heating to 140°C, add 55.8g isooctanoic acid (purchased from Tai'an Jiaye Biotechnology Co., Ltd.), maintain the temperature at 140-150°C, react for 1-3 hours, and the epoxy equivalent detected at the reaction endpoint is 1300±10 g / equivalent, which is qualified, and the organic acid modified epoxy resin is obtained.

[0132] The preparation process and related parameters of the 613g low-temperature blocked isocyanate curing agent are as follows:

[0133] S1: In a four-necked flask with a condenser and nitrogen protection (purchased from Shanghai Gaoxin Chemical Glass Co., Ltd. or Collings), add 298g of hexamethylene diisocyanate (purchased from Jinan Hongwang Chemical Co., Ltd.) and 64.7g of methyl isobutyl ketone (purchased from Jinan Century Tongda Chemical Co., Ltd.), and heat to 30°C;

[0134] S2: 154.5 g of propylene glycol blocking agent (purchased from Nantong Yida Chemical Co., Ltd.) was added dropwise into the flask, the temperature was controlled at 50 ± 3 ° C, and the NCO equivalent was controlled at 230-270 g / mol;

[0135] S3: 74.1 g of ethylene glycol isooctyl ether (purchased from Jiangsu Yida Chemical Co., Ltd.) was added to the flask. After the addition, the temperature was raised to 90° C. and kept at 90±3° C. for 1 hour. The NCO equivalent was measured to be 156320 g / mol, which was >42000 g / mol.

[0136] S4: Add 21.8 g of methyl isobutyl ketone (purchased from Jinan Century Tongda Chemical Co., Ltd.) into the flask, and control the solid content to 80±2% to obtain the low-temperature blocked isocyanate curing agent.

[0137] It should be noted that N,N-dimethylaminourea was not used in this comparative example, and dicarboxylic acid type acid was not added for chain extension, which is not within the scope of the present invention, and is therefore only comparative example 1. The emulsion prepared as described above has the problems of poor yellowing resistance, roughness, low hardness, and water resistance, salt spray resistance, acid resistance and alkali resistance that are not up to standard.

[0138] Comparative Example 2: Emulsion 2 as a comparative example

[0139] Emulsion 2 as a comparative example was prepared according to the formula and preparation steps of comparative example 1, except that the preparation process and related parameters of the 1184.2 g organic acid-modified epoxy resin were as follows:

[0140] S1: Add 1068.1 g of hydrogenated bisphenol A epoxy resin (the starting epoxy equivalent of the epoxy resin is 600-750 g / equivalent) and 60.2 g of ethylene glycol butyl ether (purchased from J&K Technology Co., Ltd., purity 99.5%) into a three-necked flask equipped with a stirrer, a condenser and a thermometer (purchased from Shanghai Gaoxin Chemical Glass Co., Ltd. or Collings), and start heating;

[0141] S2: Add 0.1g N,N-dimethylbenzylamine (purchased from Tianjin CITIC Kaitai Chemical Co., Ltd., purity 98%) into the flask, continue heating to 140°C, add 30.8g adipic acid (purchased from Tai'an Jiaye Biotechnology Co., Ltd.) and 25g isooctanoic acid (purchased from Tai'an Jiaye Biotechnology Co., Ltd.), maintain the temperature at 140-150°C, react for 1-3 hours, and the epoxy equivalent detected at the reaction endpoint is 1300±10 g / equivalent, which is qualified, and the organic acid modified epoxy resin is obtained.

[0142] It should be noted that, based on Comparative Example 1, Comparative Example 2 adds a dicarboxylic acid type acid for chain extension, and still does not use N,N-dimethylaminourea, which is not within the scope of the present invention, and is therefore only Comparative Example 2. The emulsion prepared as described above has the problems of poor yellowing resistance, roughness, low hardness, and water resistance, salt spray resistance, acid resistance, and alkali resistance that do not meet the standards.

[0143] Comparative Example 3: Emulsion 3 as a comparative example

[0144] Emulsion 3 as a comparative example was prepared according to Table 4 and the following steps:

[0145] Table 4: Formula of emulsion 3 as comparative example

[0146]

[0147] (1) Preparation of 1738.9 g of amine-modified epoxy resin polymer

[0148] S1: Add 1028.1g of Nippon's traditional product FDR-5601 to a three-necked flask equipped with a stirrer, a condenser, and a thermometer (purchased from Shanghai Gaoxin Chemical Glass Co., Ltd. or Collings Company), and when the temperature drops to 90°C, add 55.2g of diethanolamine (purchased from Tianjin CITIC Kaitai Chemical Co., Ltd., purity 98%), 60.3g of ketimine (purchased from Nippon Paint (China) Co., Ltd.), and 575.8g of low-temperature blocked isocyanate curing agent, and rinse the kettle wall with 19.5g of ethylene glycol butyl ether;

[0149] S2: heating the mixture to 105-110° C. and keeping the temperature for 2 hours to obtain the amine-modified epoxy resin polymer.

[0150] (2) Preparation of cationic aqueous dispersion emulsion

[0151] S1: Add 1139.2g of pure water and 30.05g of acetic acid into the dropping kettle, adjust the acid value to 50-70mgKOH / g, and obtain acid water;

[0152] S2: The amine-modified epoxy resin polymer was stirred at a high speed of 800-1000 rpm, and 23.5 g of Airase 5700 silicone water-based defoamer (purchased from Evonik Specialty Chemicals (Shanghai) Co., Ltd.) was added under stirring;

[0153] S3: keep stirring, add acid water to the amine-modified epoxy resin polymer, and control the dropping speed to ensure that the dropping time is 1 hour;

[0154] S4: After the dropwise addition was completed, the mixture was stirred at a speed of 800-1000 rpm for 60 min, 432.1 g and 1412.5 g of pure water were added twice, and high-speed dispersion was continued at 30° C. for 2 hours. The emulsion 3 as the comparative example was obtained by filtration.

[0155] The preparation process and related parameters of the 575.8 g low-temperature blocked isocyanate curing agent are the same as those in Example 1.

[0156] It should be noted that the technical indicators of the emulsion 3 prepared as a comparative example in the above steps are: solid content 36±2%, particle size ≤90nm, and pH controlled at 6.3±0.3. In this comparative example, Nippon's traditional product FDR-5601 is used as the main resin for emulsion design. It does not use N,N-dimethylaminourea, selects bisphenol A epoxy resin, and does not add dicarboxylic acid acid for chain growth. It is not within the scope of the present invention, so it is only comparative example 3. The emulsion prepared as described above has poor anti-yellowing performance, roughness, low hardness, and water resistance, salt spray resistance, acid resistance and alkali resistance are not up to standard.

[0157] The emulsions obtained in Examples 1-2 and Comparative Examples 1-3 were tested according to the following parameters and steps:

[0158] S1: 40 parts of the emulsions obtained in the above-mentioned Examples 1-2 and Comparative Examples 1-3 were respectively mixed with 10 parts of color paste (ACECRON 2500F-1WHITE produced by Nippon Paint Industrial Coatings (Shanghai) Co., Ltd.) and 50 parts of pure water to obtain an electrophoretic coating;

[0159] S2: The electrophoretic coatings are all cathodic electrophoretic coatings, which are placed in an electrophoretic tank for aging for 16-24 hours;

[0160] S3: After aging, the blade operation voltage is controlled to 120V, the tank liquid temperature is controlled to 30°C, and electrophoresis is performed for 3 minutes;

[0161] S4: The coating films obtained by electrophoresis were baked at 160° C. for 20 min (plate surface) to obtain a white dry film;

[0162] S5: The obtained white dry films were tested for performance, and the data are shown in Table 5.

[0163] Table 5 Main performance test results of Examples 1-2 and Comparative Examples 1-3

[0164]

[0165] The results in Table 5 above show that the coating formed by the cationic aqueous dispersion emulsion containing N,N-dimethylaminourea modified epoxy resin provided by the present invention has excellent high temperature resistance and yellowing resistance, no gloss loss, no fading problems, smooth coating, and hardness meets the requirements. In Comparative Example 1, since N,N-dimethylaminourea is not used, and dicarboxylic acid type acid is not added for chain growth, the electrophoretic coating formed by the prepared emulsion has poor yellowing resistance, roughness, low hardness, and water resistance, salt spray resistance, acid resistance and alkali resistance are not up to standard. Comparative Example 2 does not use N,N-dimethylaminourea, and the electrophoretic coating formed by the prepared emulsion also has poor yellowing resistance and roughness. Problems; Comparative Example 3 uses Nippon's traditional product FDR-5601 as the main resin for emulsion design, and the anti-yellowing performance is very poor, rough, low hardness, and water resistance, salt spray resistance, acid resistance and alkali resistance are not up to standard.

[0166] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the protection scope of the present invention.

Claims

1. A cationic aqueous dispersion emulsion containing N,N-dimethylaminourea modified epoxy resin, which comprises, by weight:

2. The cationic aqueous dispersion emulsion containing N,N-dimethylaminourea modified epoxy resin according to claim 1, characterized in that: The organic acid-modified epoxy resin comprises the following components in parts by weight:

3. The cationic aqueous dispersion emulsion containing N,N-dimethylaminourea modified epoxy resin according to claim 2, characterized in that: The epoxy resin is selected from one or more of hydrogenated bisphenol A epoxy resin and hydrogenated bisphenol F epoxy resin with an epoxy equivalent of 600-800 g / equivalent; Preferably, the epoxy resin is selected from a combination of hydrogenated bisphenol A epoxy resin and hydrogenated bisphenol F epoxy resin having different molecular weights; more preferably, the epoxy resin is hydrogenated bisphenol A epoxy resin; the organic acid A and the organic acid B are selected from acids having one or more unsaturated double bonds; Preferably, the organic acid A is a dicarboxylic acid organic acid, selected from one or more of adipic acid, oxalic acid, malonic acid, and succinic acid, and the organic acid B is selected from one or more of formic acid, acetic acid, octanoic acid, and isooctanoic acid; The solvent B is selected from one or more of alcohol solvents and alcohol ether solvents; preferably, the alcohol solvent includes but is not limited to isopropanol, n-butanol, isobutanol, n-hexanol, isooctyl alcohol, ethylene glycol or propylene glycol, and the alcohol ether solvent includes but is not limited to ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol butyl ether, ethylene glycol hexyl ether, diethylene glycol butyl ether, ethylene glycol isooctyl ether, propylene glycol methyl ether or propylene glycol phenyl ether; The alkaline catalyst includes N,N-dimethylbenzylamine, triethylamine, dimethylaminopropylamine, dimethylaminobutylamine, diethylaminopropylamine, triethanolamine, and tetramethylammonium chloride.

4. The cationic aqueous dispersion emulsion containing N,N-dimethylaminourea modified epoxy resin according to claim 2 or 3, characterized in that: The preparation of the organic acid-modified epoxy resin comprises the following steps: S1: Add epoxy resin and solvent B to a three-necked flask equipped with a stirrer, a condenser, and a thermometer, turn on the heating, slowly drop N,N-dimethylaminourea during the heating process, stop heating when the temperature rises to 120°C, and keep warm for 1 hour; S2: Add an alkaline catalyst into the flask, continue heating to 140° C., add organic acid A and organic acid B, maintain the temperature between 140-150° C. for reaction for 1-3 hours, and when the epoxy equivalent is 1300±10 g / equivalent at the reaction endpoint, the organic acid-modified epoxy resin is obtained.

5. The cationic aqueous dispersion emulsion containing N,N-dimethylaminourea modified epoxy resin according to claim 1, characterized in that: The low-temperature blocked isocyanate curing agent comprises the following components in parts by weight:

6. The cationic aqueous dispersion emulsion containing N,N-dimethylaminourea modified epoxy resin according to claim 5, characterized in that: The isocyanate is selected from one or more of aliphatic polyisocyanates and alicyclic polyisocyanates; preferably, the aliphatic polyisocyanate includes but is not limited to 1,4-butyl diisocyanate or hexamethylene diisocyanate, and the alicyclic polyisocyanate includes but is not limited to 1,3-cyclopentane diisocyanate, 1,4-cyclohexane diisocyanate or isophorone diisocyanate; The inert solvent is selected from one or more of methyl isobutyl ketone, acetone, and tetrahydrofuran; The low-temperature sealing agent is an aliphatic substance with active hydrogen, preferably one or more selected from ethylene glycol, propylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol butyl ether, ethylene glycol hexyl ether, diethylene glycol butyl ether, propylene glycol methyl ether, and isooctyl alcohol; The solvent C is selected from one or more of ethylene glycol monomethyl ether, ethylene glycol, isooctyl alcohol, and propylene glycol.

7. The cationic aqueous dispersion emulsion containing N,N-dimethylaminourea modified epoxy resin according to claim 5 or 6, characterized in that: The preparation of the low-temperature blocked isocyanate curing agent comprises the following steps: S1: In a four-necked flask with a condenser and nitrogen protection, add isocyanate and some inert solvent, and heat to 30°C; S2: Add low-temperature sealing agent dropwise into the flask, the temperature is controlled at 50±3°C during the addition process, and the NCO equivalent is controlled at 230-270 g / mol; S3: Add solvent C into the flask, raise the temperature to 90°C after the addition, and keep it at 90±3°C for 1 hour, and control the NCO equivalent to >42000 g / mol; S4: adding the remaining inert solvent into the flask and controlling the solid content to be 80±2% to obtain the low-temperature blocked isocyanate curing agent.

8. The cationic aqueous dispersion emulsion containing N,N-dimethylaminourea modified epoxy resin according to claim 1, characterized in that: The amine compound is selected from one or more of diethanolamine, ketimine, methyldiethanolamine, diethylenetriamine, di-n-butylamine, and triethanolamine; the solvent A is selected from one or more of ethylene glycol, propylene glycol phenyl ether, ethylene glycol butyl ether, and propylene glycol; the acid is selected from one or more of organic acids or inorganic acids, and the organic acid is preferably selected from one or more of acetic acid, aminosulfonic acid, formic acid, lactic acid, and citric acid, and the inorganic acid is preferably nitric acid.

9. A method for preparing a cationic aqueous dispersion emulsion containing N,N-dimethylaminourea modified epoxy resin as claimed in any one of claims 1 to 8, comprising the following steps: (1) Preparation of amine-modified epoxy resin polymer S1: Add an organic acid-modified epoxy resin to a three-necked flask equipped with a stirrer, a condenser, and a thermometer, and when the temperature drops to 90° C., add an amine compound, a low-temperature blocked isocyanate curing agent, and solvent A; S2: heating to 105-110° C. and keeping the temperature for 1-3 hours to obtain the amine-modified epoxy resin polymer; (2) Preparation of cationic aqueous dispersion emulsion S1: adding part of pure water and acid into the dropping kettle, adjusting the acid value to 50-70 mgKOH / g, and obtaining acid water; S2: stirring the amine-modified epoxy resin polymer at a high speed of 800-1000 rpm, and adding a defoaming agent under stirring; S3: Keep stirring, add acid water to the amine-modified epoxy resin polymer, and control the dropping speed to ensure that the dropping time is 1 hour; S4: After the dropwise addition is completed, stirring is performed at a speed of 800-1000 rpm for 60 minutes, the remaining pure water is added twice, and high-speed dispersion is continued at 30° C. for 2 hours. The cationic aqueous dispersion emulsion containing the N,N-dimethylaminourea modified epoxy resin is obtained by filtering.

10. An anti-yellowing electrophoretic coating, comprising, by weight: 40-50 parts of cationic aqueous dispersion containing N,N-dimethylaminourea modified epoxy resin Color paste 9-10 parts 40-80 parts of pure water The total content of the above components is 100 parts; it is characterized in that, The preparation method of the anti-yellowing electrophoretic coating comprises the following steps: mixing the cationic aqueous dispersion emulsion containing N,N-dimethylaminourea modified epoxy resin according to any one of claims 1 to 8, a color paste and pure water, and stirring evenly to obtain the anti-yellowing electrophoretic coating.

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