A zwitterionic waterborne epoxy resin and preparation method thereof, and a dispersion, preparation method thereof and application thereof

Abstract

The present invention belongs to the technical field of waterborne epoxy resin preparation, and discloses a zwitterionic waterborne epoxy resin and preparation method and a dispersion, preparation method and application. Disulfide carboxylic acid is prepared by mercapto-ene reaction, and then a zwitterionic waterborne epoxy resin with cation as sulfonium and anion as carboxylate is obtained by ring-opening reaction of thioether and epoxy resin. The structure of zwitterion solves the damage of free neutralizer ions to coating stability, coating adhesion and anticorrosion performance in traditional anionic and cationic waterborne coatings; at the same time, the adhesion of carboxylate ions to metal substrates can be better exerted, and the performance difficulties of traditional anionic modified waterborne epoxy resins can be solved. After adding water to form a dispersion, it can become a substitute for the mainstream non-ionic waterborne epoxy resins on the market, and can also be used as an auxiliary agent to further enhance the adhesion or anticorrosion performance of existing waterborne epoxy products on various metal substrates, and has a wide range of application prospects.

Description

Technical Field

[0001] The invention relates to the technical field of waterborne epoxy resins, and in particular to a zwitterionic waterborne epoxy resin and a preparation method thereof, and a dispersion, a preparation method thereof and an application thereof. Background Art

[0002] The water-based resins commonly used in the market can be divided into three categories according to the characteristics of the hydrophilic group: non-ionic, cationic and anionic. Among them, the non-ionic type mainly relies on polyoxyethylene ether as the hydrophilic structure. Although the polyether structure has no obvious benefit for metal corrosion protection, it has become the main technical route for water-based epoxy resins on the market due to its excellent adaptability to the formulation; cationic water-based resins are mostly weakly acidic, and have a narrow adaptability to substrates and coating formulations, and are mainly used in cathode electrophoretic coatings; anionic types not only have good particle stability and formulation adaptability by introducing carboxyl salts, but also have strong complexing ability of carboxyl / carboxylate on various metal surfaces such as iron, aluminum, and copper, which can theoretically significantly improve the adhesion and anti-corrosion performance of the coating to the metal substrate.

[0003] However, as the preferred epoxy resin system for metal anticorrosive primers, anionic water-based technology has some drawbacks that are difficult to resolve. The main factor is that a neutralizer must be introduced during the carboxyl ionization process. If alkali metal hydroxides and carbonates are used as neutralizers, there will undoubtedly be a large number of highly hydrophilic metal ions remaining in the paint film, causing problems. Therefore, the industry prefers to use volatile organic amines as neutralizers. However, most organic amine neutralizers have strong nucleophilicity. Using them in epoxy resins will lead to continuous ring-opening and consumption of epoxy groups during storage, resulting in a shortened shelf life and reduced coating performance.

[0004] Therefore, providing an epoxy resin with a long shelf life is of great significance to the development of epoxy resins. Summary of the invention

[0005] The purpose of the present invention is to provide a zwitterionic waterborne epoxy resin and a preparation method thereof, and a dispersion, a preparation method thereof and an application thereof, so as to solve the problems existing in the prior art.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a zwitterionic waterborne epoxy resin, wherein the cation is a sulfonium ion and the anion is a carboxylate ion;

[0008] The zwitterionic waterborne epoxy resin is prepared from the following raw materials in parts by weight:

[0009] 5 to 20 parts of mercapto compounds, 5 to 20 parts of olefinic compounds, 0.1 to 1 part of free radical initiator, 40 to 80 parts of epoxy resin, and 5 to 20 parts of solvent.

[0010] Preferably, in the above-mentioned zwitterionic waterborne epoxy resin, the thiol compound is one or two of thiol carboxylic acid and polythiol compound, and the olefinic compound is one or two of polyolefinic compound and olefinic unsaturated carboxylic acid;

[0011] When the thiol compound is a thiol carboxylic acid, the olefinic compound is a polyolefinic compound; when the thiol compound is a polyolefinic compound, the olefinic compound is an olefinic unsaturated carboxylic acid;

[0012] The mercaptocarboxylic acid is one or more of mercaptoacetic acid, 3-mercaptopropionic acid, 3-mercaptobenzoic acid, 3-mercaptoisobutyric acid, and 4-mercaptobenzoic acid; the polythiol compound is one or more of 1,2-ethanedithiol, 1,2-propylenethiol, 1,3-propylenethiol, 1,4-butylenethiol, 1,5-pentanedithiol, 1,6-hexanedithiol, 1,4-benzenedithiol, and m-dibenzyl mercaptan;

[0013] The polyolefin compound is one or more of 1,6-hexanediol diacrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tripropylene glycol diacrylate, tripropylene glycol diacrylate, ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, divinyl ether, and diallyl ether; and the olefinic unsaturated carboxylic acid is one or more of acrylic acid, methacrylic acid, and vinyl acetic acid.

[0014] Preferably, in the above-mentioned zwitterionic waterborne epoxy resin, the free radical initiator is one or more of azobisisobutyronitrile, azobisisovaleronitrile, azobisisoheptylnitrile, and dibenzoyl peroxide, and the solvent is one or more of isopropanol, acetone, butanone, diacetone alcohol, propylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol butyl ether, and diethylene glycol butyl ether.

[0015] Preferably, in the above-mentioned zwitterionic waterborne epoxy resin, the epoxy resin is one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, and phenolic epoxy resin, and the epoxy value of the epoxy resin is 0.40 to 0.53.

[0016] The present invention also provides a method for preparing a zwitterionic waterborne epoxy resin, comprising the following steps:

[0017] (1) mixing a thiol compound, an olefinic compound, a free radical initiator, and a solvent, and reacting the mixture to obtain a disulfide carboxylic acid solution;

[0018] (2) The epoxy resin is mixed with a disulfide carboxylic acid solution to react to obtain a zwitterionic waterborne epoxy resin.

[0019] Preferably, in the above-mentioned method for preparing a zwitterionic waterborne epoxy resin, the specific process of the reaction in step (1) is: heating to 50-80°C, keeping warm for 2-8 hours, and cooling to 30-40°C after the insulation is completed; the specific process of the reaction in step (2) is: heating to 60-80°C, keeping warm for 4-10 hours.

[0020] The present invention also provides a dispersion prepared from the following raw materials in parts by weight:

[0021] 40-60 parts of zwitterionic waterborne epoxy resin, 40-60 parts of water;

[0022] The present invention also provides a method for preparing a dispersion, comprising the following steps:

[0023] Water is added to the zwitterionic waterborne epoxy resin and mixed to obtain a zwitterionic waterborne epoxy resin dispersion.

[0024] Preferably, in the above-mentioned method for preparing a dispersion, the temperature of the water-adding and mixing is 50-70° C., and the water-adding and mixing further comprises dispersing at 30-50° C. for 30-90 minutes.

[0025] The invention also provides use of the dispersion in metal primer.

[0026] It can be seen from the above technical solution that compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The present invention utilizes an efficient thiol-ene "click chemistry" reaction mechanism, that is, a thiol compound of different structures is reacted with an olefin compound in the first step of a free radical initiator to obtain a disulfide carboxylic acid compound, which is then reacted with an excess of epoxy resin to obtain a sulfonium-carboxylate zwitterionic waterborne epoxy resin, which can be dispersed in water to form a stable dispersion for use in waterborne metal anticorrosive coatings, thereby further improving the adhesion or anticorrosion performance of existing waterborne epoxy products on various metal substrates.

[0028] (2) The hydrophilic group of the zwitterionic waterborne epoxy resin described in the present invention is a zwitterion in which a sulfonium cation and a carboxylate ion are combined on the same molecule, resulting in the following characteristics:

[0029] The surface of the resin particles dispersed in water is charged, with excellent physical stability, and can maintain hydrophilicity in a wide pH range from acidic to alkaline. Its adaptability to coating formulation systems is comparable to that of non-ionic waterborne epoxy resin systems.

[0030] In the resin structure, the carboxylate group is located at the outermost end of the side chain. Since there is no free paired cation, compared with the anionic carboxylate system neutralized by alkali, the lone pair of electrons of the carboxylate group in the present invention is in a "naked" state, and the adsorption and complexing ability on the metal surface is stronger, which can effectively improve the adhesion of the coating to various metal substrates; at the same time, the system does not contain any free hydrophilic ions or small molecules, so the coating has better water resistance;

[0031] Under high-temperature baking conditions, the sulfonium cations in the resin can form stable chemical bonds with metals such as iron and copper, further enhancing the adhesion and anti-corrosion performance of the coating on such metal surfaces. This property of sulfonium salts has been applied and verified in the field of cathodic electrophoretic coatings.

[0032] By selecting epoxy resins with different epoxy values ​​and controlling the ratio of the amount of epoxy group to the amount of thioether group, the hydrophilicity of the obtained zwitterionic waterborne epoxy resin can be adjusted to meet different application requirements. Therefore, the resin obtained in the present invention can be directly diluted with water to form a dispersion for use as a film-forming material for two-component waterborne epoxy coatings, and can also be used as an emulsifier and adhesion promoter for performance optimization of other types of waterborne coatings. DETAILED DESCRIPTION

[0033] The present invention provides a zwitterionic waterborne epoxy resin, wherein the cation is a sulfonium ion and the anion is a carboxylate ion;

[0034] The zwitterionic waterborne epoxy resin is prepared from the following raw materials in parts by weight:

[0035] 5 to 20 parts of mercapto compounds, 5 to 20 parts of olefinic compounds, 0.1 to 1 part of free radical initiator, 40 to 80 parts of epoxy resin, and 5 to 20 parts of solvent.

[0036] In the present invention, the mass fraction of the mercapto compound is preferably 5 to 20 parts, more preferably 5, 8, 10, 12, 15, 17 or 20 parts, and even more preferably 10, 12 or 15 parts.

[0037] In the present invention, the weight fraction of the olefinic compound is preferably 5 to 20 parts, more preferably 5, 8, 10, 12, 15, 17 or 20 parts, and more preferably 10, 12 or 15 parts.

[0038] In the present invention, the mass fraction of the radical initiator is preferably 0.1 to 1 part, more preferably 0.1, 0.3, 0.5, 0.7 or 1 part, and more preferably 0.3, 0.5 or 0.7 part.

[0039] In the present invention, the mass fraction of the epoxy resin is preferably 40 to 80 parts, more preferably 40, 45, 50, 55, 60, 65, 70, 75 or 80 parts, and more preferably 55, 60, 65 or 70 parts.

[0040] In the present invention, the mass fraction of the solvent is preferably 5 to 20 parts, more preferably 5, 7, 9, 12, 15, 17 or 20 parts, and even more preferably 12, 15 or 17 parts.

[0041] In the present invention, the thiol compound is preferably one or two of thiol carboxylic acid and polythiol compound, and more preferably thiol carboxylic acid; the olefin compound is preferably one or two of polyolefin compound and olefinic unsaturated carboxylic acid, and more preferably polyolefin compound;

[0042] When the thiol compound is a thiol carboxylic acid, the olefinic compound is preferably a polyolefinic compound; when the thiol compound is a polyolefinic compound, the olefinic compound is preferably an olefinic unsaturated carboxylic acid.

[0043] In the present invention, the mercaptocarboxylic acid is preferably one or more of thioglycolic acid, 3-mercaptopropionic acid, 3-mercaptobenzoic acid, 3-mercaptoisobutyric acid, and 4-mercaptobenzoic acid, and is further preferably one or more of thioglycolic acid, 3-mercaptopropionic acid, and 3-mercaptobenzoic acid, and is more preferably thioglycolic acid; the polythiol compound is preferably one or more of 1,2-ethanedithiol, 1,2-propylenethiol, 1,3-propylenethiol, 1,4-butanedithiol, 1,5-pentanedithiol, 1,6-hexanedithiol, 1,4-benzenedithiol, and m-dibenzyl mercaptan, and is further preferably one or more of 1,2-ethanedithiol, 1,2-propylenethiol, 1,3-propylenethiol, and 1,4-butanedithiol, and is more preferably one or two of 1,2-ethanedithiol and 1,2-propylenethiol;

[0044] The polyolefin compound is preferably one or more of 1,6-hexanediol diacrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tripropylene glycol diacrylate, tripropylene glycol diacrylate, ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, divinyl ether, and diallyl ether, and is further preferably one or more of triethylene glycol diacrylate, tripropylene glycol diacrylate, tripropylene glycol diacrylate, and ethylene glycol divinyl ether, and is more preferably one or two of tripropylene glycol diacrylate and tripropylene glycol diacrylate; the ethylenically unsaturated carboxylic acid is preferably one or more of acrylic acid, methacrylic acid, and vinyl acetic acid, and is further preferably one or two of acrylic acid and methacrylic acid, and is more preferably acrylic acid.

[0045] In the present invention, the free radical initiator is preferably one or more of azobisisobutyronitrile, azobisisovaleronitrile, azobisisoheptanenitrile, and dibenzoyl peroxide, further preferably one or more of azobisisobutyronitrile, azobisisovaleronitrile, and dibenzoyl peroxide, and more preferably one or two of azobisisovaleronitrile and dibenzoyl peroxide; the solvent is preferably one or more of isopropanol, acetone, butanone, diacetone alcohol, propylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol butyl ether, and diethylene glycol butyl ether, further preferably one or more of isopropanol, acetone, butanone, diacetone alcohol, propylene glycol methyl ether, and diethylene glycol butyl ether, and more preferably one or more of acetone, butanone, diacetone alcohol, and propylene glycol methyl ether.

[0046] In the present invention, the epoxy resin is preferably one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, and novolac epoxy resin, further preferably one or two of bisphenol A epoxy resin and bisphenol F epoxy resin, and more preferably bisphenol A epoxy resin; the epoxy value of the epoxy resin is preferably 0.40-0.53, further preferably 0.42, 0.44, 0.51, 0.53, and more preferably 0.44 or 0.51.

[0047] The present invention also provides a method for preparing a zwitterionic waterborne epoxy resin, comprising the following steps:

[0048] (1) mixing a thiol compound, an olefinic compound, a free radical initiator, and a solvent, and reacting the mixture to obtain a disulfide carboxylic acid solution;

[0049] (2) The epoxy resin is mixed with a disulfide carboxylic acid solution to react to obtain a zwitterionic waterborne epoxy resin.

[0050] In the present invention, the reaction in step (1) is carried out under a protective gas, and the protective gas is preferably one of nitrogen, helium, neon and argon, more preferably one of nitrogen, helium and neon, and more preferably nitrogen.

[0051] In the present invention, the specific process of the reaction in step (1) is preferably: heating to 50-80°C, keeping warm for 2-8h, and cooling to 30-40°C after the insulation is completed. It is further preferably: heating to 50, 55, 60, 65, 70, 75 or 80°C, keeping warm for 2, 3, 4, 5, 6, 7 or 8h, and cooling to 30, 32, 34, 36, 38 or 40°C after the insulation is completed. It is more preferably heating to 50, 55, 60, 65 or 70°C. The method is preferably characterized in that the temperature is raised to 60-80°C and the temperature is kept at 4-10 hours, more preferably the temperature is raised to 60, 62, 64, 66, 68, 70, 72, 74, 76, 78 or 80°C and the temperature is kept at 4, 5, 6, 7, 8, 9 or 10 hours, and more preferably the temperature is raised to 62, 64, 66, 68 or 70°C and the temperature is kept at 6, 7 or 8 hours.

[0052] The present invention also provides a dispersion prepared from the following raw materials in parts by weight:

[0053] 40-60 parts of zwitterionic waterborne epoxy resin, 40-60 parts of water;

[0054] In the present invention, the mass fraction of the zwitterionic waterborne epoxy resin is preferably 40 to 60 parts, more preferably 40, 42, 44, 46, 48, 50, 52, 54, 55, 58 or 60 parts, more preferably 46, 48, 50, 52, 54 or 55 parts.

[0055] In the present invention, the mass fraction of water is preferably 40 to 60 parts, more preferably 40, 42, 44, 46, 48, 50, 52, 54, 55, 58 or 60 parts, and more preferably 52, 54, 55, 58 or 60 parts.

[0056] The present invention also provides a method for preparing a dispersion, comprising the following steps:

[0057] Water is added to the zwitterionic waterborne epoxy resin and mixed to obtain a zwitterionic waterborne epoxy resin dispersion.

[0058] In the present invention, the temperature of adding water and mixing is preferably 50-70°C, more preferably 50, 53, 55, 57, 60, 62, 64, 67 or 70°C, more preferably 55, 57, 60, 62, 64 or 67°C; after the adding water and mixing, the mixture further comprises dispersing at 30-50°C for 30-90min, more preferably dispersing at 30, 33, 36, 38, 40, 42, 45, 47 or 50°C for 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85 or 90min, more preferably dispersing at 36, 38, 40, 42 or 45°C for 70, 75, 80, 85 or 90min.

[0059] The invention also provides use of the dispersion in metal primer.

[0060] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0061] Example 1

[0062] A method for preparing a zwitterionic waterborne epoxy resin A comprises the following steps:

[0063] 13 parts by weight of thioglycolic acid, 15 parts by weight of diethylene glycol diacrylate, 0.3 parts by weight of azobisisobutyronitrile and 14 parts by weight of propylene glycol methyl ether were added to a reaction kettle, mixed and dissolved evenly, and nitrogen was introduced into the reaction kettle, then the temperature was raised to 60° C. and kept warm for 4 hours, the time for heating to 60° C. was 20 minutes, and the temperature was lowered to 40° C. after the insulation was completed to obtain a disulfide carboxylic acid solution; 57 parts by weight of bisphenol A type epoxy resin with an epoxy value of 0.51 was further added to the reaction kettle, mixed evenly, and then the temperature was raised to 70° C. and kept warm for 8 hours to obtain a zwitterionic water-based epoxy resin A with a solid content of 86wt%, which can be directly used as an epoxy resin emulsifier.

[0064] A process for preparing a zwitterionic waterborne epoxy dispersion A comprises the following steps:

[0065] Take 41 parts by weight of the prepared zwitterionic waterborne epoxy resin A, heat it to 60°C, stir it at a speed of 500 rpm and uniformly add 59 parts by weight of pure water, add 59 parts by weight of pure water for 30 minutes, maintain the temperature at 45°C and continue stirring for 60 minutes to obtain a zwitterionic waterborne epoxy dispersion A with a solid content of 35wt%. The zwitterionic waterborne epoxy dispersion A has a transparent appearance and can be used as an adhesion promoter for waterborne epoxy coatings.

[0066] Example 2

[0067] A method for preparing a zwitterionic waterborne epoxy resin B comprises the following steps:

[0068] 8 parts by weight of thioglycolic acid, 10 parts by weight of 1,6-hexanediol diacrylate, 0.2 parts by weight of azobisisobutyronitrile and 10 parts by weight of ethylene glycol ethyl ether were added to a reaction kettle, mixed and dissolved evenly, and nitrogen was introduced into the reaction kettle, then the temperature was raised to 60° C. and kept warm for 4 hours, the time for heating to 60° C. was 20 minutes, and the temperature was lowered to 40° C. after the insulation was completed to obtain a disulfide carboxylic acid solution; 71 parts by weight of bisphenol A type epoxy resin with an epoxy value of 0.51 was continuously added to the reaction kettle, the temperature was raised to 75° C. and kept warm for 8 hours after stirring evenly, and a zwitterionic waterborne epoxy resin B with a solid content of 90wt% was obtained.

[0069] A method for preparing a zwitterionic waterborne epoxy dispersion B comprises the following steps:

[0070] Take 50 parts by weight of the above-prepared zwitterionic waterborne epoxy resin B, heat it to 60°C, stir it at a speed of 800rpm and uniformly add 50 parts by weight of pure water, add 50 parts by weight of pure water for 30min, maintain the temperature at 45°C and continue stirring for 60min to obtain a zwitterionic waterborne epoxy dispersion B with a solid content of 45wt%. The appearance of the zwitterionic waterborne epoxy dispersion B is milky white with blue light, and can be used as a two-component waterborne epoxy coating film-forming material.

[0071] Example 3

[0072] A method for preparing a zwitterionic waterborne epoxy resin C comprises the following steps:

[0073] 8 parts by weight of 3-mercaptopropionic acid, 6 parts by weight of diethylene glycol divinyl ether, 0.2 parts by weight of azobisisobutyronitrile, 4 parts by weight of isopropanol and 8 parts by weight of propylene glycol methyl ether were added to a reactor, mixed and dissolved evenly, and nitrogen was introduced into the reactor. The temperature was then raised to 60° C. and kept warm for 4 hours. The time for heating to 60° C. was 20 minutes. After the insulation was completed, the temperature was lowered to 40° C. to obtain a disulfide carboxylic acid solution. 73 parts by weight of bisphenol A epoxy resin with an epoxy value of 0.51 was continuously added to the reactor. After stirring evenly, the temperature was raised to 75° C. and kept warm for 8 hours to obtain a zwitterionic waterborne epoxy resin C with a solid content of 88wt%.

[0074] A method for preparing a zwitterionic waterborne epoxy dispersion C comprises the following steps:

[0075] Take 46 parts by weight of the zwitterionic waterborne epoxy resin C prepared in Example 3, heat to 60°C, stir at a speed of 1000 rpm and uniformly add 54 parts by weight of pure water, add 54 parts by weight of pure water for 30 minutes, maintain the temperature at 50°C and continue stirring for 90 minutes to obtain a zwitterionic waterborne epoxy dispersion C with a solid content of 40%. The zwitterionic waterborne epoxy dispersion C has an appearance of milky white with blue light and can be used as a two-component waterborne epoxy coating film-forming material.

[0076] Example 4

[0077] A method for preparing a zwitterionic waterborne epoxy resin D comprises the following steps:

[0078] 7 parts by weight of 3-mercaptopropionic acid, 7 parts by weight of triethylene glycol divinyl ether, 0.2 parts by weight of azobisisobutyronitrile and 10 parts by weight of ethylene glycol butyl ether were added to a reaction kettle, mixed and dissolved evenly, and nitrogen was introduced into the reaction kettle. The temperature was then raised to 60° C. and kept warm for 4 hours. The time for heating to 60° C. was 20 minutes. After the insulation was completed, the temperature was lowered to 40° C. to obtain a disulfide carboxylic acid solution. 76 parts by weight of bisphenol A epoxy resin with an epoxy value of 0.51 was further added to the reaction kettle. After stirring evenly, the temperature was raised to 70° C. and kept warm for 10 hours to obtain a zwitterionic waterborne epoxy resin D with a solid content of 90wt%.

[0079] A method for preparing a zwitterionic waterborne epoxy dispersion D comprises the following steps:

[0080] Take 40 parts by weight of the above-prepared zwitterionic waterborne epoxy resin D, heat it to 60°C, add 60 parts by weight of pure water at a uniform rate while stirring at a speed of 400 rpm, add 60 parts by weight of pure water for 30 minutes, maintain the temperature at 50°C and continue stirring for 90 minutes to obtain a zwitterionic waterborne epoxy dispersion D with a solid content of 35%. The appearance of the zwitterionic waterborne epoxy dispersion D is milky white with blue light, and can be used as a two-component waterborne epoxy coating film-forming material.

[0081] Example 5

[0082] A method for preparing a zwitterionic waterborne epoxy resin E comprises the following steps:

[0083] 6 parts by weight of 1,2-ethanedithiol, 9 parts by weight of acrylic acid, 0.3 parts by weight of azobisisobutyronitrile and 25 parts by weight of propylene glycol methyl ether were added into a reaction kettle, mixed and dissolved evenly, and nitrogen was introduced into the reaction kettle, and then the temperature was raised to 60°C and kept warm for 4 hours. The time for heating to 60°C was 20 minutes, and the temperature was lowered to 40°C after the insulation to obtain a disulfide carboxylic acid solution; 59 parts by weight of bisphenol A type epoxy resin with an epoxy value of 0.44 was further added into the reaction kettle, and the temperature was raised to 70°C and kept warm for 10 hours after stirring evenly to obtain a zwitterionic water-based epoxy resin E with a solid content of 75wt%, which can be directly used as an epoxy resin emulsifier.

[0084] A method for preparing a zwitterionic waterborne epoxy dispersion E comprises the following steps:

[0085] Take 40 parts by weight of the zwitterionic waterborne epoxy resin E prepared above, heat to 60°C, stir at a speed of 700rpm and uniformly add 60 parts by weight of pure water, add 60 parts by weight of pure water for 30 minutes, maintain the temperature at 50°C and continue stirring for 60 minutes to obtain a zwitterionic waterborne epoxy dispersion E with a solid content of 30wt%. The appearance of the zwitterionic waterborne epoxy dispersion E is translucent and can be used as an adhesion promoter for waterborne epoxy coatings.

[0086] Example 6

[0087] A method for preparing a zwitterionic waterborne epoxy resin F comprises the following steps:

[0088] 5 parts by weight of 1,4-butanedithiol, 6 parts by weight of acrylic acid, 0.2 parts by weight of azobisisobutyronitrile, 5 parts by weight of isopropanol and 10 parts by weight of propylene glycol methyl ether were added into a reactor, mixed and dissolved evenly, and nitrogen was introduced into the reactor. The temperature was then raised to 60° C. and kept warm for 4 hours. The time for heating to 60° C. was 20 minutes. After the insulation was completed, the temperature was lowered to 40° C. to obtain a disulfide carboxylic acid solution. 74 parts by weight of bisphenol A epoxy resin with an epoxy value of 0.44 was continuously added into the reactor. After stirring evenly, the temperature was raised to 75° C. and kept warm for 10 hours to obtain a zwitterionic waterborne epoxy resin F with a solid content of 85wt%.

[0089] A method for preparing a zwitterionic waterborne epoxy dispersion F comprises the following steps:

[0090] Take 35 parts by weight of the zwitterionic waterborne epoxy resin F prepared above, heat to 60°C, stir at a speed of 850rpm and uniformly add 65 parts by weight of pure water, add 65 parts by weight of pure water for 30 minutes, maintain the temperature at 60°C and continue stirring for 90 minutes to obtain a zwitterionic waterborne epoxy dispersion F with a solid content of 30wt%. The appearance of the zwitterionic waterborne epoxy dispersion F is milky white with blue light, and can be used as a two-component waterborne epoxy coating film-forming material.

[0091] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A zwitterionic waterborne epoxy resin, characterized in that: In the zwitterionic waterborne epoxy resin, the cation is a sulfonium ion and the anion is a carboxylate ion; The zwitterionic waterborne epoxy resin is prepared from the following raw materials in parts by weight: 5-20 parts of mercapto compounds, 5-20 parts of olefin compounds, 0.1-1 parts of free radical initiators, 40-80 parts of epoxy resins, and 5-20 parts of solvents; The thiol compound is one or two of thiol carboxylic acid and polythiol compounds, and the olefinic compound is one or two of polyolefinic compounds and olefinic unsaturated carboxylic acids; When the thiol compound is a thiol carboxylic acid, the olefinic compound is a polyolefinic compound; when the thiol compound is a polyolefinic compound, the olefinic compound is an olefinic unsaturated carboxylic acid; The mercaptocarboxylic acid is one or more of mercaptoacetic acid, 3-mercaptopropionic acid, 3-mercaptobenzoic acid, 3-mercaptoisobutyric acid, and 4-mercaptobenzoic acid; the polythiol compound is one or more of 1,2-ethanedithiol, 1,2-propylenethiol, 1,3-propylenethiol, 1,4-butylenethiol, 1,5-pentanedithiol, 1,6-hexanedithiol, 1,4-benzenedithiol, and m-dibenzyl mercaptan; The polyolefin compound is one or more of 1,6-hexanediol diacrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tripropylene glycol diacrylate, ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, divinyl ether, and diallyl ether; and the olefinic unsaturated carboxylic acid is one or more of acrylic acid, methacrylic acid, and vinyl acetic acid; The preparation method of zwitterionic waterborne epoxy resin comprises the following steps: (1) mixing a thiol compound, an olefinic compound, a free radical initiator, and a solvent, and reacting the mixture to obtain a disulfide carboxylic acid solution; (2) The epoxy resin is mixed with a disulfide carboxylic acid solution to react to obtain a zwitterionic waterborne epoxy resin.

2. The zwitterionic waterborne epoxy resin according to claim 1, characterized in that: The free radical initiator is one or more of azobisisobutyronitrile, azobisisovaleronitrile, azobisisoheptylnitrile, and dibenzoyl peroxide; the solvent is one or more of isopropanol, acetone, butanone, diacetone alcohol, propylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol butyl ether, and diethylene glycol butyl ether.

3. The zwitterionic waterborne epoxy resin according to claim 2, characterized in that: The epoxy resin is one or more of bisphenol A epoxy resin, bisphenol F epoxy resin and phenolic epoxy resin, and the epoxy value of the epoxy resin is 0.40-0.

53.

4. The method for preparing the zwitterionic waterborne epoxy resin according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) mixing a thiol compound, an olefinic compound, a free radical initiator, and a solvent, and reacting the mixture to obtain a disulfide carboxylic acid solution; (2) The epoxy resin is mixed with a disulfide carboxylic acid solution to react to obtain a zwitterionic waterborne epoxy resin.

5. The method for preparing the zwitterionic waterborne epoxy resin according to claim 4, characterized in that: The specific process of the reaction in step (1) is: heating to 50-80°C, keeping warm for 2-8h, and cooling to 30-40°C after the end of the insulation; The specific process of the reaction in step (2) is: heating to 60-80° C. and keeping warm for 4-10 hours.

6. A dispersion, characterized in that It is prepared from the following raw materials in parts by weight: 40-60 parts of zwitterionic waterborne epoxy resin, 40-60 parts of water; The zwitterionic waterborne epoxy resin is the zwitterionic waterborne epoxy resin according to any one of claims 1 to 3.

7. A method for preparing the dispersion according to claim 6, characterized in that The following steps are involved: Water is added to the zwitterionic waterborne epoxy resin and mixed to obtain a zwitterionic waterborne epoxy resin dispersion.

8. The method according to claim 7, characterized in that The temperature of the water adding and mixing is 50-70° C., and the water adding and mixing further comprises dispersing at 30-50° C. for 30-90 minutes.

9. Use of the dispersion according to claim 6 in metal primer.