Sulfonic acid type water-borne epoxy resin and preparation method thereof as well as water-borne anti-corrosion coating and preparation method thereof

Abstract

The invention discloses sulfonic acid type water-borne epoxy resin and a preparation method thereof as well as water-borne anticorrosive paint and a preparation method thereof. The preparation method of the sulfonic acid type water-borne epoxy resin comprises the following steps: adding epoxy resin and dicarboxylic acid into a reaction container, adding a catalyst, keeping the temperature at 100-130 DEG C until the acid value of a system is less than 3mgKOH / g, and cooling to below 50 DEG C to obtain carboxylic acid chain-extended epoxy resin; the preparation method comprises the following steps: dissolving carboxylic acid chain-extended epoxy resin with a mixed solvent, adding sulfamic acid and a neutralizer, raising the temperature to 55-65 DEG C, keeping the temperature for 0.8-1.2 hours, raising the temperature to 85-95 DEG C within 1.8-2.2 hours, keeping the temperature to react until the solution is transparent, and adding deionized water for emulsifying to obtain the sulfonate type water-borne epoxy resin dispersion, namely the sulfonic acid type water-borne epoxy resin. The water-borne epoxy resin is small in viscosity and good in storage stability and has the advantages of being good in salt mist resistance and corrosion resistance.

Description

Technical Field

[0001] The present invention relates to the field of waterborne epoxy resins, and in particular to a sulfonic acid type waterborne epoxy resin and a preparation method thereof, and a waterborne anti-corrosion coating and a preparation method thereof. Background Art

[0002] Currently, there are three main methods for water-based epoxy resins, both domestically and internationally: mechanical methods, phase inversion methods with external emulsifiers, and chemically modified self-emulsifiers. The first two methods involve adding external emulsifiers to produce waterborne epoxy emulsions, resulting in larger particle sizes. The inclusion of emulsifiers also reduces the water resistance of the coating, limiting their application. The chemically modified self-emulsifier method introduces hydrophilic groups or components into the epoxy resin molecular chain through epoxy ring-opening or free radical-induced grafting reactions, causing self-emulsification to produce a waterborne epoxy emulsion. This emulsion achieves nanometer-scale particle sizes, excellent storage stability, and high application value. Currently, the hydrophilic components commonly used in waterborne epoxy resins are mostly non-ionic compounds containing carboxylates and ammonium salts. These waterborne epoxy resins suffer from high viscosity, poor storage stability, and poor corrosion resistance. For example, Chinese invention patent application CN107603410A synthesizes an intermediate through an esterification reaction between polyethylene glycol and a phthalic anhydride derivative. This intermediate is then used in a ring-opening polymerization reaction with an epoxy resin to produce a nonionic reactive emulsifier with excellent emulsification for the epoxy resin. This is then combined with a phase inversion method to thoroughly premix the nonionic reactive emulsifier and epoxy resin, followed by the dropwise addition of deionized water and a defoamer, ultimately producing a stable water-based epoxy resin emulsion. However, the addition of the epoxy nonionic emulsifier exceeds 15-20%, resulting in a viscosity exceeding 10,000 mPa·s, poor storage stability, and poor chemical and corrosion resistance of the coating. Chinese invention patent application CN102432773A uses a polymerized monomer as a dispersion medium, reacting the epoxy resin with acrylic acid in the presence of tetrabutylammonium bromide to produce an epoxy acrylic acid monomer. The epoxy acrylate monomer is then pre-emulsified with other monomers, and then a semi-continuous seeded emulsion polymerization method is used to copolymerize the epoxy acrylate monomer and other monomers to prepare a water-based epoxy acrylate graft composite emulsion. This process uses the comonomer as the solvent dispersion medium for the first-step esterification reaction between the epoxy resin and the acrylic acid. It also serves as the monomer for the second-step copolymerization reaction. The organic solvent from the first step is not removed by vacuum distillation, thus avoiding the impact of residual solvent on product properties. The epoxy acrylate graft composite emulsion has a high grafting rate, can improve the compatibility of epoxy resin and acrylic resin, and enhance the coating's water resistance, adhesion, and salt spray resistance. It can be widely used in metal coatings and architectural coating materials. This water-based epoxy resin combines the properties of epoxy resin and polyacrylic acid resin, but has the following disadvantages: low conversion rate of acrylic acid monomer, difficulty in removing residual acrylic acid monomer, long reaction time, complex process, and the presence of acrylic acid copolymer in the water-based resin system. Due to the uneven composition, the corrosion resistance of the coating is reduced, and the proportion of epoxy resin is low. Chinese invention patent application CN110498933A discloses a self-emulsifying water-based epoxy emulsion and its preparation method.The preparation method first mixes a monofunctional primary amine, a polyether, and a reactive diluent, reacting at 60-80°C to synthesize an amino-terminated polyether with multiple hydrophilic segments. This is then reacted with an epoxy resin in a water bath at 60-80°C for 2-3 hours, neutralized with glacial acetic acid, and a self-emulsifying epoxy resin with a viscosity between 5938 and 8783 mPa·s is prepared. This patent actually prepares a cationic waterborne epoxy resin, which can flocculate when compounded with anionic resins, increasing the production and management costs of waterborne resin coatings. All of these waterborne epoxy resins suffer from excessive viscosity, poor storage stability, and the corrosion resistance of the waterborne coatings needs to be further improved. Summary of the Invention

[0003] In order to overcome the above-mentioned shortcomings and deficiencies of the prior art, the purpose of the present invention is to provide a method for preparing a sulfonic acid-type water-based epoxy resin, which first extends the epoxy resin chain, then reacts with aminosulfonic acid to introduce hydrophilic sulfonic acid groups into the epoxy resin molecules, and then directly emulsifies into water, thereby solving the problems of high viscosity and poor storage stability of water-based epoxy resins. At the same time, the amount of hydrophilic groups or emulsifiers added to the resin is reduced, the residual hydrophilic substances in the coating film are reduced, and its anti-corrosion properties such as salt spray resistance are improved.

[0004] Another object of the present invention is to provide a sulfonic acid type water-based epoxy resin prepared by the preparation method of the sulfonic acid type water-based epoxy resin.

[0005] Another object of the present invention is to provide a method for preparing a water-based anti-corrosion coating.

[0006] Another object of the present invention is to provide a water-based anti-corrosion coating prepared by the above-mentioned preparation method of the water-based anti-corrosion coating.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] The present invention provides a method for preparing a sulfonic acid type waterborne epoxy resin, comprising the following steps:

[0009] (1) Chain extension reaction of epoxy resin: epoxy resin and dicarboxylic acid are added to a reaction vessel at a molar ratio of epoxy group to carboxyl group of 8:1-4, a catalyst is added, the reaction vessel is heated at 100-130°C until the acid value of the system is less than 3 mgKOH / g, and the temperature is then lowered to below 50°C to obtain a carboxylic acid chain-extended epoxy resin;

[0010] (2) Preparation of water-based epoxy resin: The carboxylic acid-extended epoxy resin obtained in step (1) is dissolved in a mixed solvent of ethylene glycol butyl ether and ethanol, aminosulfonic acid and a neutralizing agent are added, the system temperature is raised to 55-65°C, and the temperature is kept warm for 0.8-1.2 hours, then the temperature is raised to 85-95°C within 1.8-2.2 hours, and the temperature is kept warm until the system becomes transparent. Deionized water is added within 3-15 minutes while stirring at a speed of 500-2000 rpm and the mixture is emulsified for 0.8-1.2 hours to obtain a sulfonate-type water-based epoxy resin dispersion, i.e., a sulfonic acid-type water-based epoxy resin.

[0011] Preferably, the aminosulfonic acid is one of aminopropanesulfonic acid, aminoethanesulfonic acid and aminobenzenesulfonic acid.

[0012] Preferably, the epoxy resin is one of 1,4-butanediol diglycidyl ether, E51, E44, E20, E12 and E06.

[0013] Preferably, the dicarboxylic acid is one of succinic acid, glutaric acid, adipic acid and sebacic acid.

[0014] Preferably, the catalyst is one of tetraethylammonium bromide, tetrabutylammonium bromide and triphenylphosphine; and its usage is 0.2-0.5% of the mass of the dicarboxylic acid.

[0015] Preferably, the neutralizing agent is one of triethylamine, N,N-dimethylcyclohexylamine, and N,N-dimethylethanolamine.

[0016] The present invention also provides a sulfonic acid type water-based epoxy resin, which is prepared by the preparation method of the sulfonic acid type water-based epoxy resin.

[0017] Preferably, the sulfonic acid type waterborne epoxy resin has a solid content of 40%-50%, a viscosity of 300-1000 mPa·s, an epoxy equivalent of 500-1000 g / equivalent, and a storage stability of 1 year at room temperature.

[0018] The present invention also provides a method for preparing a water-based anti-corrosion coating. The sulfonic acid-type water-based epoxy resin and the water-based epoxy curing agent are added according to a molar ratio of epoxy group to active hydrogen of 1:1, stirred for 15 to 25 minutes to disperse evenly, and deionized water is added to adjust the solid content to prepare the water-based anti-corrosion coating.

[0019] The present invention also provides a water-based anti-corrosion coating, which is prepared by the preparation method of the water-based anti-corrosion coating; the neutral salt spray resistance time of the white paint coating prepared by using the water-based anti-corrosion coating is more than 550 hours.

[0020] Preferably, in the mixed solvent, the volume ratio of ethylene glycol butyl ether to ethanol is 4:1-4.

[0021] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0022] (1) The preparation method of the sulfonic acid type water-based epoxy resin of the present invention first extends the chain of the epoxy resin, then reacts with aminosulfonic acid to introduce hydrophilic sulfonic acid groups into the epoxy resin molecules, and then directly emulsifies into water, thereby solving the problems of high viscosity and poor storage stability of the water-based epoxy resin. At the same time, the amount of hydrophilic groups or emulsifiers added to the resin is reduced, the residual hydrophilic substances in the coating film are reduced, and its anti-corrosion properties such as salt spray resistance are improved.

[0023] (2) The sulfonic acid type waterborne epoxy resin of the present invention introduces a strong ionic group, sulfonic acid group, into the epoxy molecule. Sulfonate is a salt of strong acid and strong base, has strong hydrophilic ability, and requires a small amount of hydrophilic monomer. The coating containing the sulfonate has excellent adhesion to the substrate, effectively improving the water resistance and corrosion resistance of the two-component waterborne epoxy system coating. The strong ionic group, sulfonic acid group, enhances the zeta potential (ζ) of the "double electric layer" of the latex particles, enhances the electrostatic force between the colloid particles, and improves the repulsive force between the colloid particles, which can effectively improve the storage stability of the sulfonate type waterborne epoxy dispersion, and is more conducive to the preparation of a sulfonate type waterborne epoxy dispersion with a high solid content. In addition, the sulfonate type waterborne epoxy dispersion has good compatibility with other resins, additives, pigments, and fillers, further improving the corrosion resistance of the waterborne epoxy coating.

[0024] (3) Carboxylate-type waterborne epoxy resins in the prior art are easily hydrolyzed to produce carboxylic acid, which catalyzes the degradation of waterborne epoxy dispersions and affects storage stability. The sulfonic acid-type waterborne epoxy resins of the present invention have excellent storage stability compared to them. Waterborne epoxy dispersions containing polyoxyethylene segments in the prior art are affected by the molecular weight of the compound containing the polyoxyethylene segment. When the molecular weight is small, the hydrophilicity is poor, and when the molecular weight increases, the hydrophilicity is enhanced, but the viscosity of the product increases accordingly, resulting in poor fluidity, which limits the final application of the product. The sulfonic acid-type waterborne epoxy resins of the present invention have lower viscosity compared to them. In a preferred embodiment, the viscosity can be 300-600mPa·s. Compared with non-ionic and carboxylic acid-type waterborne epoxy resin emulsion competitors, the waterborne coating prepared using the sulfonic acid-type waterborne epoxy resin of the present invention has good mechanical stability and storage stability, and excellent anti-corrosion performance, and can be widely used in the preparation of anti-corrosion coatings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a Fourier infrared spectrum of the sulfonate-type waterborne epoxy dispersion in Example 1 of the present invention.

[0026] Figure 2 This is the H-NMR spectrum of the sulfonate-type waterborne epoxy dispersion in Example 1 of the present invention. DETAILED DESCRIPTION

[0027] The present invention will be further described in detail below with reference to the examples, but the embodiments of the present invention are not limited thereto.

[0028] In the following examples, the testing process is as follows:

[0029] Coating performance test: The surface drying time of the coating was measured according to GB / T 1728-1979 (89); the gloss of the coating was measured according to GB / T 1743-1979 (89); the pencil hardness of the coating was measured according to GB / T 6739-2006; the abrasion resistance of the coating was measured according to GB / T 23988-2009; the adhesion of the coating was measured according to GB / T 1720-2020; the water resistance of the coating was measured according to GB / T 5209-1985; the alkali resistance of the coating was measured according to GB / T 1763-1979; the acid resistance of the coating was measured according to GB / T 9274-1988; the epoxy equivalent was measured according to ASTM D1652; the neutral salt spray resistance time was measured according to GB / T 1771-2007.

[0030] Example 1

[0031] This embodiment provides a method for preparing a sulfonic acid type waterborne epoxy resin, comprising the following steps:

[0032] (1) Chain extension reaction of epoxy resin: In a three-necked flask equipped with a thermometer and a condenser, epoxy resin E51 and succinic acid were added to a four-necked flask at a molar ratio of epoxy group to carboxyl group of 8:1. A catalyst, tetraethylammonium bromide, was added. The reaction was kept at 130°C for 4 h until the acid value of the system was less than 3 mgKOH / g. The reaction was then cooled to below 50°C to obtain a carboxylic acid-chain-extended epoxy resin.

[0033] (2) Preparation of water-based epoxy resin: The above epoxy resin was dissolved in a mixed solvent of ethylene glycol butyl ether and ethanol (volume ratio of 4:1), aminoethanesulfonic acid and neutralizing agent triethylamine were added, the system temperature was raised to 60°C, kept warm for 1 hour, then raised to 90°C within 2 hours, kept warm and reacted until the system became transparent, deionized water was added within 15 minutes under stirring at 2000 rpm and emulsified for 1 hour to obtain a sulfonate-type water-based epoxy dispersion, i.e., a sulfonic acid-type water-based epoxy resin.

[0034] The properties of the sulfonic acid type waterborne epoxy resin are: solid content of 42%; viscosity of 500mPa·s, epoxy value of 700g / equivalent, and storage stability at room temperature for 1 year.

[0035] Preparation of water-based epoxy varnish: Sulfonic acid-type water-based epoxy resin and curing agent were evenly mixed in a molar ratio of epoxy to active hydrogen of 1:1, and then brushed on the board. After drying at room temperature for 7 days, the test properties are listed in Table 1. Comparison with water-based epoxy varnishes prepared with water-based epoxy resin Banco2060 and water-based curing agent Banco901 of Banghe Chemical Co., Ltd. and water-based epoxy emulsion WE319 and water-based curing agent GH109 of Zhuhai Jili Chemical Co., Ltd. is also listed in Table 1.

[0036] Table 1 Properties of waterborne epoxy varnish

[0037] Performance indicators Example 1+Banco901 Banco2060+Banco901 WE319+GH109 Surface drying time (min) 50 90 60 Glossiness (60°) 106 98 104 Pencil hardness 3H 2H 2H Adhesion (grade) 0 1 1 Abrasion resistance (750g / 500r) 0.003 0.037 0.022 Water resistance (7d) pass pass pass Alkali resistance (20% NaOH, 5d) pass 3 days of blistering 3 days of blistering <![CDATA[Acid resistance (10% H2SO4, 3d)]]> pass 36h foaming 36h foaming

[0038] Figure 1 This is the infrared spectrum of the waterborne epoxy resin prepared in Example 1. -1 The infrared peak corresponds to the stretching vibration peak of CH, which is a typical characteristic peak of the epoxy group of epoxy resin, 1509cm -1 The infrared peak at 821 cm corresponds to the stretching vibration of C=C in the aromatic ring, which is the characteristic peak of E51. -1 This peak corresponds to the out-of-plane bending vibration of CH in the aromatic ring, which further confirms the existence of the aromatic ring structure. -1 , 1096cm -1 and 949cm -1 The stretching vibration peaks corresponding to CO (epoxy group), COC (ether bond) and asymmetric stretching vibration of epoxy group are characteristic peaks of epoxy resin, indicating the presence of epoxy group. Figure 2The nuclear magnetic hydrogen spectrum of the water-based epoxy resin prepared in Example 1 shows that the chemical shifts of 6.73ppm and 6.41ppm correspond to the hydrogen atoms on the aromatic rings, the chemical shift of 3.62ppm corresponds to the methylene hydrogen atoms in the epoxy group, the chemical shift of 2.75ppm may correspond to another methylene hydrogen atom in the epoxy group, the chemical shifts of 2.24ppm and 2.12ppm correspond to the methyl hydrogen atoms on the benzene ring, and the chemical shift of 1.71ppm corresponds to the methylene hydrogen atoms on the aliphatic chain. This shows that the water-based epoxy resin containing sulfonate was successfully prepared. The higher epoxy content in Example 1 also makes the cross-linking density of the cured product larger and the paint film more dense, so the gloss, hardness and wear resistance are better, but also because Example 1 needs to consume more curing agent when compounded with the curing agent, the alkalinity of the system is enhanced, which affects the acid resistance of the paint film. Compared with the emulsions on the market, the paint film performance has its own advantages. When there are high requirements for hardness and wear resistance, such as some warehouse floors where heavy forklifts will drive, and good comprehensive performance is required, especially excellent chemical resistance, Example 1 can be used. The product of Example 1 was used to prepare a white primer, and the neutral salt spray resistance of the primer was tested. It was found that the neutral salt spray resistance time of the water-based epoxy resin coating in this embodiment can reach 600 hours. The water-based epoxy white primer prepared using the water-based epoxy resin Banco2060 and water-based curing agent Banco901 of Banghe Chemical Co., Ltd. and the water-based epoxy emulsion WE319 and water-based curing agent GH109 of Zhuhai Jili Chemical Co., Ltd. has a neutral salt spray resistance time of less than 500 hours, indicating that the water-based epoxy resin prepared by the present invention has excellent corrosion resistance. Compared with Chinese invention patent application CN107603410A, this patent first prepares epoxy non-ionic emulsifier and emulsifies epoxy resin at a temperature of 60-80°C. The addition amount of non-ionic emulsifier is more than 10%, and the product viscosity is high, which is mainly used for floor coatings; while the addition amount of hydrophilic sulfonate in this patent is less than 5%, and the viscosity is lower than 500CP, which has simple process and good product performance; Chinese invention patent application CN102432773A first reacts epoxy resin to prepare vinyl-containing epoxy resin, and then copolymerizes it with acrylic monomer. Because vinyl epoxy resin is a large molecular vinyl (bifunctional) monomer, the conversion rate is not high. Finally, it is necessary to reduce the pressure to remove the residual acrylic monomer. The preparation process is complicated, and the addition amount of epoxy resin component is not high, which will reduce the adhesion of the resin coating as a primer. The present invention uses a reasonably priced and environmentally friendly sulfonate material to produce a water-based epoxy resin coating through a simple method. The coating exhibits excellent adhesion and chemical resistance, and can be widely used in the production of water-based, environmentally friendly, corrosion-resistant coatings or industrial paints. Chinese invention patent application CN110498933A prepares a cationic epoxy resin emulsion, but most water-based resins used in coatings are anionic, making them immiscible with other resins, significantly limiting their application.The water-based epoxy resin prepared by this patent can be physically miscible with commonly used water-based resins, has good versatility, and has broad application prospects in water-based anti-corrosion coatings.

[0039] Example 2

[0040] This embodiment provides a method for preparing a sulfonic acid type waterborne epoxy resin, comprising the following steps:

[0041] (1) Chain extension reaction of epoxy resin: In a three-necked flask equipped with a thermometer and a condenser, 1,4-butanediol diglycidyl ether and adipic acid were added to a four-necked flask at a molar ratio of epoxy group to carboxyl group of 8:2. A catalyst, tetrabutylammonium bromide, was added. The reaction mixture was kept at 120°C for 4 h until the acid value of the system was less than 3 mgKOH / g. The reaction mixture was then cooled to below 50°C to obtain a carboxylic acid chain-extended epoxy resin.

[0042] (2) Preparation of water-based epoxy resin: The above epoxy resin was dissolved in a mixed solvent of ethylene glycol butyl ether and ethanol (volume ratio of 4:1), aminopropanesulfonic acid and neutralizing agent N,N-dimethylcyclohexylamine were added, the system temperature was raised to 55°C, kept warm for 1.2 hours, then raised to 95°C within 2.2 hours, kept warm and reacted until the system became transparent, deionized water was added within 3 minutes under stirring at 500 rpm and emulsified for 0.8 hours to obtain a sulfonate-type water-based epoxy dispersion, i.e., a sulfonic acid-type water-based epoxy resin.

[0043] The properties of the sulfonic acid type waterborne epoxy resin are: solid content of 50%; viscosity of 300mPa·s, epoxy equivalent of 1000g / equivalent, and storage stability at room temperature for 1 year.

[0044] Preparation of water-based epoxy varnish: Sulfonic acid-type water-based epoxy resin and curing agent were evenly mixed in a molar ratio of epoxy to active hydrogen of 1:1, and then brushed on the board. After drying at room temperature for 7 days, the test properties are listed in Table 2. Comparison with water-based epoxy varnishes prepared with water-based epoxy resin Banco2060 and water-based curing agent Banco901 of Banghe Chemical Co., Ltd. and water-based epoxy emulsion WE319 and water-based curing agent GH109 of Zhuhai Jili Chemical Co., Ltd. is also listed in Table 2.

[0045] Table 2 Properties of waterborne epoxy varnish

[0046] Performance indicators Example 2+Banco901 Banco2060+Banco901 WE319+GH109 Surface drying time (min) 60 90 60 Glossiness (60°) 115 98 104 Pencil hardness HB 2H 2H Adhesion (grade) 0 1 1 Abrasion resistance (750g / 500r) 0.004 0.037 0.022 Water resistance (7d) pass pass pass Alkali resistance (20% NaOH, 5d) pass 3 days of blistering 3 days of blistering <![CDATA[Acid resistance (10% H2SO4, 3d)]]> pass 36h foaming 36h foaming

[0047] Example 3

[0048] This embodiment provides a method for preparing a sulfonic acid type waterborne epoxy resin, comprising the following steps:

[0049] (1) Chain extension reaction of epoxy resin: In a three-necked flask equipped with a thermometer and a condenser, epoxy resin E44 and adipic acid were added to a four-necked flask at a molar ratio of epoxy group to carboxyl group of 8:1.5. Triphenylphosphine was added as a catalyst. The reaction mixture was kept at 120°C for 4 h until the acid value of the system was less than 3 mgKOH / g. The reaction mixture was then cooled to below 50°C to obtain a carboxylic acid chain-extended epoxy resin.

[0050] (2) Preparation of water-based epoxy resin: The above epoxy resin was dissolved in a mixed solvent of ethylene glycol butyl ether and ethanol (volume ratio of 4:1), and aminoethanesulfonic acid and a neutralizing agent N,N-dimethylethanolamine were added. The system temperature was raised to 55°C and kept warm for 1 hour. Then, the temperature was raised to 90°C within 2 hours and kept warm to react until the system became transparent. Deionized water was added within 10 minutes under stirring at 1500 rpm and emulsified for 1 hour to obtain a sulfonate-type water-based epoxy dispersion, i.e., a sulfonic acid-type water-based epoxy resin.

[0051] The properties of the sulfonic acid type waterborne epoxy resin are: solid content 40.0%; viscosity 533mPa·s, epoxy value 687g / equivalent, and storage stability at room temperature for 1 year.

[0052] Preparation of water-based epoxy varnish: Sulfonic acid-type water-based epoxy resin and curing agent were evenly mixed in a molar ratio of epoxy to active hydrogen of 1:1, and then brushed on the board. After drying at room temperature for 7 days, the test properties are listed in Table 3. Comparison with water-based epoxy varnishes prepared with water-based epoxy resin Banco2060 and water-based curing agent Banco901 of Banghe Chemical Co., Ltd. and water-based epoxy emulsion WE319 and water-based curing agent GH109 of Zhuhai Jili Chemical Co., Ltd. is also listed in Table 3.

[0053] Table 3 Properties of waterborne epoxy varnish

[0054] Performance indicators Example 3+Banco901 Banco2060+Banco901 WE319+GH109 Surface drying time (min) 52 90 60 Gloss (60°) 107 98 104 Pencil hardness 3H 2H 2H Adhesion (grade) 0 1 1 Abrasion resistance (750g / 500r) 0.007 0.037 0.022 Water resistance (7d) pass pass pass Alkali resistance (20% NaOH, 5d) pass 3 days of blistering 3 days of blistering <![CDATA[Acid resistance (10% H2SO4, 3d)]]> pass 36h foaming 36h foaming

[0055] Example 4

[0056] This embodiment provides a method for preparing a sulfonic acid type waterborne epoxy resin, comprising the following steps:

[0057] (1) Chain extension reaction of epoxy resin: In a three-necked flask equipped with a thermometer and a condenser, epoxy resin E20 and sebacic acid were added to a four-necked flask at a molar ratio of epoxy group to carboxyl group of 8:2. A catalyst, tetrabutylammonium bromide, was added. The reaction was kept at 120°C for 4 h until the acid value of the system was less than 3 mgKOH / g. The reaction was then cooled to below 50°C to obtain a carboxylic acid chain-extended epoxy resin.

[0058] (2) Preparation of water-based epoxy resin: The above epoxy resin was dissolved in a mixed solvent of ethylene glycol butyl ether and ethanol (volume ratio of 4:1), aminopropanesulfonic acid and neutralizing agent N, N-dimethylcyclohexylamine were added, the system temperature was raised to 60 ° C, kept warm for 1 hour, and then raised to 90 ° C within 2 hours, kept warm and reacted until the system became transparent, deionized water was added within 15 minutes under stirring at 1000 rpm and emulsified for 1 hour to obtain a sulfonate-type water-based epoxy dispersion, that is, a sulfonic acid-type water-based epoxy resin.

[0059] The properties of the sulfonic acid type waterborne epoxy resin are: solid content 46.6%; viscosity 554mPa·s, epoxy value 640g / equivalent, and storage stability at room temperature for 1 year.

[0060] Preparation of water-based epoxy varnish: Sulfonic acid-type water-based epoxy resin and curing agent were evenly mixed in a molar ratio of epoxy to active hydrogen of 1:1, and then brushed on the board. After drying at room temperature for 7 days, the test properties are listed in Table 4. Comparison with water-based epoxy varnishes prepared with water-based epoxy resin Banco2060 and water-based curing agent Banco901 of Banghe Chemical Co., Ltd. and water-based epoxy emulsion WE319 and water-based curing agent GH109 of Zhuhai Jili Chemical Co., Ltd. is also listed in Table 4.

[0061] Table 4 Properties of waterborne epoxy varnish

[0062] Performance indicators Example 4+Banco901 Banco2060+Banco901 WE319+GH109 Surface drying time (min) 51 90 60 Glossiness (60°) 105 98 104 Pencil hardness 3H 2H 2H Adhesion (grade) 0 1 1 Abrasion resistance (750g / 500r) 0.005 0.037 0.022 Water resistance (7d) pass pass pass Alkali resistance (20% NaOH, 5d) pass 3 days of blistering 3 days of blistering <![CDATA[Acid resistance (10% H2SO4, 3d)]]> pass 36h foaming 36h foaming

[0063] Example 5

[0064] This embodiment provides a method for preparing a sulfonic acid type waterborne epoxy resin, comprising the following steps:

[0065] (1) Chain extension reaction of epoxy resin: In a three-necked flask equipped with a thermometer and a condenser, epoxy resin E12 and adipic acid were added to a four-necked flask at a molar ratio of epoxy group to carboxyl group of 8:3. A catalyst, tetrabutylammonium bromide, was added. The reaction was kept at 130°C for 4 h until the acid value of the system was less than 3 mgKOH / g. The reaction was then cooled to below 50°C to obtain a carboxylic acid chain-extended epoxy resin.

[0066] (2) Preparation of water-based epoxy resin: The above epoxy resin was dissolved in a mixed solvent of ethylene glycol butyl ether and ethanol (volume ratio of 4:2), aminobenzenesulfonic acid and neutralizing agent N, N-dimethylcyclohexylamine were added, the system temperature was raised to 60 ° C, kept warm for 1 hour, and then raised to 90 ° C within 2 hours, kept warm and reacted until the system became transparent, deionized water was added within 15 minutes under stirring at 2000 rpm and emulsified for 1 hour to obtain a sulfonate-type water-based epoxy dispersion, i.e., a sulfonic acid-type water-based epoxy resin.

[0067] The properties of the sulfonic acid type waterborne epoxy resin are: solid content 45%; viscosity 535mPa·s, epoxy value 733g / equivalent, and storage stability at room temperature for 1 year.

[0068] Preparation of water-based epoxy varnish: Sulfonic acid-type water-based epoxy resin and curing agent were evenly mixed in a molar ratio of epoxy to active hydrogen of 1:1, and then brushed on the board. After drying at room temperature for 7 days, the test properties are listed in Table 5. Comparison with water-based epoxy varnishes prepared with water-based epoxy resin Banco2060 and water-based curing agent Banco901 of Banghe Chemical Co., Ltd. and water-based epoxy emulsion WE319 and water-based curing agent GH109 of Zhuhai Jili Chemical Co., Ltd. is also listed in Table 5.

[0069] Table 5 Properties of waterborne epoxy varnish

[0070] Performance indicators Example 5+Banco901 Banco2060+Banco901 WE319+GH109 Surface drying time (min) 48 90 60 Gloss (60°) 106 98 104 Pencil hardness 3H 2H 2H Adhesion (grade) 0 1 1 Abrasion resistance (750g / 500r) 0.003 0.037 0.022 Water resistance (7d) pass pass pass Alkali resistance (20% NaOH, 5d) pass 3 days of blistering 3 days of blistering <![CDATA[Acid resistance (10% H2SO4, 3 days)]]> pass 36h foaming 36h foaming

[0071] Example 6

[0072] This embodiment provides a method for preparing a sulfonic acid type waterborne epoxy resin, comprising the following steps:

[0073] (1) Chain extension reaction of epoxy resin: In a three-necked flask equipped with a thermometer and a condenser, epoxy resin E06 and succinic acid were added to a four-necked flask at a molar ratio of epoxy group to carboxyl group of 8:3. A catalyst, tetrabutylammonium bromide, was added. The reaction was kept at 125°C for 4 h until the acid value of the system was less than 3 mgKOH / g. The reaction was then cooled to below 50°C to obtain a carboxylic acid chain-extended epoxy resin.

[0074] (2) Preparation of water-based epoxy resin: The above epoxy resin was dissolved in a mixed solvent of ethylene glycol butyl ether and ethanol (volume ratio of 4:1.5), aminobenzenesulfonic acid and neutralizing agent N, N-dimethylcyclohexylamine were added, the system temperature was raised to 60 ° C, kept warm for 1 hour, and then raised to 90 ° C within 2 hours, kept warm and reacted until the system became transparent, deionized water was added within 15 minutes under stirring at 2000 rpm and emulsified for 1 hour to obtain a sulfonate-type water-based epoxy dispersion, that is, a sulfonic acid-type water-based epoxy resin.

[0075] The properties of the sulfonic acid waterborne epoxy resin are: solid content 44%; viscosity 525mPa·s, epoxy value 658g / equivalent, and storage stability at room temperature for 1 year.

[0076] Preparation of water-based epoxy varnish: Sulfonic acid-type water-based epoxy resin and curing agent were evenly mixed in a molar ratio of epoxy to active hydrogen of 1:1, and then brushed on the board. After drying at room temperature for 7 days, the test properties are listed in Table 6. Comparison with water-based epoxy varnishes prepared with water-based epoxy resin Banco2060 and water-based curing agent Banco901 of Banghe Chemical Co., Ltd. and water-based epoxy emulsion WE319 and water-based curing agent GH109 of Zhuhai Jili Chemical Co., Ltd. is also listed in Table 6.

[0077] Table 6 Properties of waterborne epoxy varnish

[0078] Performance indicators Example 6+Banco901 Banco2060+Banco901 WE319+GH109 Surface drying time (min) 54 90 60 Glossiness (60°) 109 98 104 Pencil hardness 3H 2H 2H Adhesion (grade) 0 1 1 Abrasion resistance (750g / 500r) 0.006 0.037 0.022 Water resistance (7d) pass pass pass Alkali resistance (20% NaOH, 5d) pass 3 days of blistering 3 days of blistering <![CDATA[Acid resistance (10% H2SO4, 3 days)]]> pass 36h foaming 36h foaming

[0079] Example 7

[0080] This embodiment provides a method for preparing a sulfonic acid type waterborne epoxy resin, comprising the following steps:

[0081] (1) Chain extension reaction of epoxy resin: In a three-necked flask equipped with a thermometer and a condenser, epoxy resin E06 and sebacic acid were added to a four-necked flask at a molar ratio of epoxy group to carboxyl group of 8:1. The catalyst tetrabutylammonium bromide was added and the reaction was kept at 130°C for 4 h until the acid value of the system was less than 3 mgKOH / g. The reaction was then cooled to below 50°C to obtain a carboxylic acid chain-extended epoxy resin.

[0082] (2) Preparation of water-based epoxy resin: The above epoxy resin was dissolved in a mixed solvent of ethylene glycol butyl ether and ethanol (volume ratio of 4:2), aminobenzenesulfonic acid and neutralizing agent N, N-dimethylcyclohexylamine were added, the system temperature was raised to 60 ° C, kept warm for 1 hour, and then raised to 90 ° C within 2 hours, kept warm and reacted until the system became transparent, deionized water was added within 15 minutes under stirring at 2000 rpm and emulsified for 1 hour to obtain a sulfonate-type water-based epoxy dispersion, i.e., a sulfonic acid-type water-based epoxy resin.

[0083] The properties of the sulfonic acid type waterborne epoxy resin are: solid content 48.3%; viscosity 575mPa·s, epoxy value 746g / equivalent, and storage stability at room temperature for 1 year.

[0084] Preparation of water-based epoxy varnish: Sulfonic acid type water-based epoxy resin and curing agent were evenly mixed in a molar ratio of epoxy to active hydrogen of 1:1 and then brushed on the board. After drying at room temperature for 7 days, the test performance was listed in Table 7. Comparison with water-based epoxy varnish prepared with water-based epoxy resin Banco2060 and water-based curing agent Banco901 of Banghe Chemical Co., Ltd. and water-based epoxy emulsion WE319 and water-based curing agent GH109 of Zhuhai Jili Chemical Co., Ltd. is also listed in Table 7.

[0085] Table 7 Properties of waterborne epoxy varnish

[0086] Performance indicators Example 7+Banco901 Banco2060+Banco901 WE319+GH109 Surface drying time (min) 45 90 60 Gloss (60°) 107 98 104 Pencil hardness 3H 2H 2H Adhesion (grade) 0 1 1 Abrasion resistance (750g / 500r) 0.003 0.037 0.022 Water resistance (7d) pass pass pass Alkali resistance (20% NaOH, 5d) pass 3 days of blistering 3 days of blistering <![CDATA[Acid resistance (10% H2SO4, 3 days)]]> pass 36h foaming 36h foaming

[0087] Example 8

[0088] This embodiment provides a method for preparing a sulfonic acid type waterborne epoxy resin, comprising the following steps:

[0089] (1) Chain extension reaction of epoxy resin: In a three-necked flask equipped with a thermometer and a condenser, epoxy resin E44 and glutaric acid were added to a four-necked flask at a molar ratio of epoxy group to carboxyl group of 8:1.2. Tetrabutylammonium bromide as a catalyst was added. The reaction was kept at 120°C for 4 h until the acid value of the system was less than 3 mgKOH / g. The reaction was then cooled to below 50°C to obtain a carboxylic acid chain-extended epoxy resin.

[0090] (2) Preparation of water-based epoxy resin: The above epoxy resin was dissolved in a mixed solvent of ethylene glycol butyl ether and ethanol (volume ratio of 4:1.5), and aminopropanesulfonic acid and a neutralizing agent N, N-dimethylcyclohexylamine were added. The system temperature was raised to 60°C and kept warm for 1 hour. Then, the temperature was raised to 90°C within 2 hours and kept warm to react until the system became transparent. Deionized water was added within 15 minutes under stirring at 2000 rpm and emulsified for 1 hour to obtain a sulfonate-type water-based epoxy dispersion, i.e., a sulfonic acid-type water-based epoxy resin.

[0091] The properties of the sulfonic acid type waterborne epoxy resin are: solid content 43.3%; viscosity 511mPa·s, epoxy value 702g / equivalent, and storage stability at room temperature for 1 year.

[0092] Preparation of water-based epoxy varnish: Sulfonic acid-type water-based epoxy resin and curing agent were evenly mixed in a molar ratio of epoxy to active hydrogen of 1:1, and then brushed on the board. After drying at room temperature for 7 days, the test properties are listed in Table 8. Comparison with water-based epoxy varnishes prepared with water-based epoxy resin Banco2060 and water-based curing agent Banco901 of Banghe Chemical Co., Ltd. and water-based epoxy emulsion WE319 and water-based curing agent GH109 of Zhuhai Jili Chemical Co., Ltd. is also listed in Table 8.

[0093] Table 8 Properties of waterborne epoxy varnish

[0094]

[0095]

[0096] The waterborne epoxy resin white paints prepared in Examples 1 to 8 were cured with the curing agent Banco 901, and the neutral salt spray resistance test of the white paint coatings was tested. The test results are shown in Table 9.

[0097] Table 9 Test results of central salt spray resistance of waterborne epoxy white paint

[0098]

[0099] As shown in Table 9, the coating prepared by the present invention has good neutral salt spray resistance of more than 550 hours after curing, which is better than the neutral salt spray resistance of water-based epoxy white paints prepared by water-based epoxy resin Banco2060 and water-based curing agent Banco901 of Banghe Chemical Co., Ltd. and water-based epoxy emulsion WE319 and water-based curing agent GH109 of Zhuhai Jili Chemical Co., Ltd. Compared with the patent with announcement number CN104388912B, which uses modified emulsification under high temperature conditions and a cumbersome preparation process, and the patent with announcement number CN109486361B, which uses expensive graphene oxide and a complex preparation process, the present invention uses a moderately priced and environmentally friendly sulfonate material to prepare a water-based epoxy resin coating by a simple method. The coating has excellent corrosion resistance, wear resistance, and chemical resistance, and can be widely used in the preparation of anti-corrosion water-based environmentally friendly coatings or industrial paints.

[0100] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for preparing a sulfonic acid type waterborne epoxy resin, characterized in that: The following steps are involved: (1) Chain extension reaction of epoxy resin: epoxy resin and dicarboxylic acid are added to a reaction vessel at a molar ratio of epoxy group to carboxyl group of 8:1-4, a catalyst is added, the reaction vessel is heated at 100-130°C until the acid value of the system is less than 3 mgKOH / g, and the temperature is then lowered to below 50°C to obtain a carboxylic acid chain-extended epoxy resin; (2) Preparation of water-based epoxy resin: The carboxylic acid-extended epoxy resin obtained in step (1) is dissolved in a mixed solvent of ethylene glycol butyl ether and ethanol, aminosulfonic acid and a neutralizing agent are added, the system temperature is raised to 55-65°C, and the temperature is kept warm for 0.8-1.2 hours, then the temperature is raised to 85-95°C within 1.8-2.2 hours, and the temperature is kept warm until the system becomes transparent. Deionized water is added within 3-15 minutes while stirring at a speed of 500-2000 rpm and the mixture is emulsified for 0.8-1.2 hours to obtain a sulfonate-type water-based epoxy resin dispersion, i.e., a sulfonic acid-type water-based epoxy resin.

2. The method for preparing a sulfonic acid type waterborne epoxy resin according to claim 1, wherein The aminosulfonic acid is one of aminopropanesulfonic acid, aminoethanesulfonic acid and aminobenzenesulfonic acid.

3. The method for preparing a sulfonic acid type waterborne epoxy resin according to claim 1, wherein The epoxy resin is one of 1,4-butanediol diglycidyl ether, E51, E44, E20, E12 and E06.

4. The method for preparing a sulfonic acid type waterborne epoxy resin according to claim 1, wherein The dicarboxylic acid is one of succinic acid, glutaric acid, adipic acid and sebacic acid.

5. The method for preparing the sulfonic acid type waterborne epoxy resin according to claim 1, wherein The catalyst is one of tetraethylammonium bromide, tetrabutylammonium bromide and triphenylphosphine; and its usage is 0.2-0.5% of the mass of the dicarboxylic acid.

6. The method for preparing a sulfonic acid type waterborne epoxy resin according to claim 1, wherein The neutralizing agent is one of triethylamine, N,N-dimethylcyclohexylamine and N,N-dimethylethanolamine.

7. A sulfonic acid type waterborne epoxy resin, characterized in that The sulfonic acid type waterborne epoxy resin is prepared by the preparation method of any one of claims 1 to 6.

8. The sulfonic acid type waterborne epoxy resin according to claim 7, characterized in that The solid content is 40%-50%; the viscosity is 300-1000mPa·s, the epoxy equivalent is 500-1000g / equivalent, and the storage stability at room temperature is 1 year.

9. A method for preparing a water-based anti-corrosion coating, characterized in that: The sulfonic acid waterborne epoxy resin and the waterborne epoxy curing agent according to claim 7 or 8 are added in a molar ratio of epoxy group to active hydrogen of 1:1, stirred for 15 to 25 minutes to disperse evenly, and deionized water is added to adjust the solid content to prepare a waterborne anti-corrosion coating.

10. Water-based anti-corrosion coating, characterized in that: The white paint coating prepared by the preparation method of the water-based anti-corrosion coating according to claim 9 has a neutral salt spray resistance time of more than 550 hours.

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