Self-curing waterborne epoxy resin and coating

Abstract

The invention belongs to the technical field of epoxy resin, and particularly relates to self-curing water-borne epoxy resin and coating. The self-curing water-borne epoxy resin comprises epoxy resin, bisphenol A, an accelerant, a ring-opening agent, a diluent, a neutralizer and semi-closed isocyanate; wherein the weight part ratio of the epoxy resin to the bisphenol A is (3.60-3.70): 1: 1, and the accelerant is dodecylphenol and N, N-dimethylaminopropylamine; the diluent is one or more of methanol ether, ethyl alcohol ether and butyl alcohol ether; the neutralizer is one or two of acetic acid and lactic acid; in the semi-closed isocyanate, the mass fraction of free NCO is 1%-40%. According to the self-curing water-borne epoxy resin and the coating, the self-curing water-borne epoxy resin and the coating which are environmentally friendly, high in corrosion resistance and convenient to construct are synthesized, and the preparation method is simple and efficient.

Description

Technical Field

[0001] The invention belongs to the technical field of epoxy resins, and in particular relates to a self-curing waterborne epoxy resin and a coating. Background Art

[0002] Waterborne epoxy resin system refers to a resin system with a certain number of hydrophilic groups on the molecular chain. Its hydrophobic resin chain segments can obtain a certain degree of hydrophilicity through the hydrophilic groups, and can be dispersed in water in the form of single molecules or molecular oligomers to form a transparent aqueous solution, and form a three-dimensional network structure under the action of a curing agent. This type of compound uses water as a solvent, which can reduce the amount of organic solvents used and the pollution caused to the environment.

[0003] Among epoxy resins, bisphenol A epoxy resin is a good synthetic raw material. Bisphenol A epoxy resin can be combined with various curing agents and additives. The cured product has stable performance, good adhesion, strong corrosion resistance and good chemical resistance. Its disadvantages are poor toughness and poor heat resistance. When the epoxy resin and the curing agent are cured, a highly cross-linked three-dimensional network structure will be formed, which is easy to cause defects such as silver streaks and stress concentration phenomena. After adding thermoplastic resin, when the matrix is ​​impacted, the thermoplastic resin undergoes ductile deformation and absorbs destructive energy, thereby increasing the toughness of the epoxy resin. Methods for improving heat resistance include introducing new structures into the main chain resin to increase the cross-linking density of the cured product, or adding rigid groups to the resin to increase the rigidity of the polymer skeleton structure, so that the molecules are restricted when rotating, thereby improving heat resistance.

[0004] Curing agent is an important component in the application of epoxy resin. The difference in solubility parameters between epoxy resin and curing agent seriously affects the compatibility, curing speed and performance of the coating. Waterborne epoxy curing agent modification usually uses polyamine as raw material, and adjusts its solubility parameters to match that of epoxy resin, making it water-dispersible and containing similar structures to epoxy resin.

[0005] Chinese invention patent application CN112341899A discloses a single-component heat-curable water-based epoxy resin. This technology puts alcohol into a reaction kettle, heats and dissolves it evenly, then adds a catalyst into the kettle for reaction, adds the product obtained by the reaction, an epoxy-containing emulsifier, and an epoxy resin into an emulsifying kettle, heats and disperses them evenly, and drips deionized water into the emulsifying kettle to obtain the product under high shear force. This product does not toughen the epoxy resin, which affects the flexibility of the coating, and has low corrosion resistance, water resistance of only greater than or equal to 160h, and anti-corrosion performance needs to be improved.

[0006] Chinese invention patent CN200910063609.2 discloses a water-based epoxy resin anticorrosive coating and its preparation method. This technology applies siloxane to the modification of water-based epoxy resin, which can heat self-curing and increase the flexibility of the resin. The obtained product is neutralized at room temperature with a neutralizer in an amount equal to the molar amount of the carboxyl group for 15 minutes, and then a certain amount of aminosiloxane is added in a 55°C water bath for constant temperature reaction for 60 minutes. The neutralized carboxyl group is an alkaline substance, and the entire system is alkaline. The added aminosiloxane will be unstable and easily hydrolyzed, affecting the product quality.

[0007] Therefore, the existing technology needs to be improved. Summary of the invention

[0008] In order to solve the above problems in the prior art, the present invention provides a self-curing waterborne epoxy resin and coating, synthesizes environmentally friendly, highly anti-corrosive and easy-to-construct self-curing waterborne epoxy resin and coating, and the preparation method is simple and efficient.

[0009] In order to achieve the above object, the main technical solutions adopted by the present invention include:

[0010] According to a first aspect of the present invention: a self-curing waterborne epoxy resin comprises an epoxy resin, bisphenol A, an accelerator, a ring opener, a diluent, a neutralizer and a semi-blocked isocyanate;

[0011] in:

[0012] The weight ratio of epoxy resin to bisphenol A is 3.60-3.70:1:

[0013] The accelerators are dodecylphenol and N,N-dimethylaminopropylamine;

[0014] The diluent is one or two of alcohol ethers and ketones;

[0015] The neutralizing agent is one or both of acetic acid and lactic acid;

[0016] In semi-blocked isocyanate, the mass fraction of free NCO is 1%-40%.

[0017] Furthermore, the amount of dodecylphenol used is 15%-25% of the total weight of the epoxy resin, bisphenol A and the diluent, the amount of N,N-dimethylaminopropylamine used is 0.1%-0.5% of the total weight of the epoxy resin, bisphenol A and the diluent; and the amount of the diluent used is 25%-35% of the total weight of the epoxy resin and bisphenol A.

[0018] Furthermore, the ring-opening agent is diethanolamine and polyamide, and the molar ratio of diethanolamine to polyamide is (0.7-0.8): (0.2-0.3).

[0019] Furthermore, the preparation of the self-curing waterborne epoxy resin comprises the following steps:

[0020] S1: Place a four-necked flask equipped with a condenser, a stirrer, and a thermometer in a constant temperature oil bath, add epoxy resin, bisphenol A, and dodecylphenol, stir and heat to 120-125°C, and after bisphenol A is completely dissolved, drop N,N-dimethylaminopropylamine, control the system temperature at 130-150°C, keep warm for 1.5-4h, then cool to 100°C, add diluent, and obtain a chain-extended epoxy resin;

[0021] S2: adding diethanolamine dropwise to the chain-extended epoxy resin, and maintaining the temperature at 50-70° C. for 2-4 hours to obtain a diethanolamine-modified epoxy resin;

[0022] S3: adding polyamide to diethanolamine modified epoxy resin at 100° C. for 0.4-0.5 h, and reacting at constant temperature for 2-3 h to obtain polyamide modified epoxy resin;

[0023] S4: adding the semi-blocked isocyanate to the polyamide-modified epoxy resin at 50-70° C. at a dropping speed of 3-5 s / drop, and keeping the temperature for reaction for 30 min-1 h to obtain a semi-blocked isocyanate-grafted epoxy resin;

[0024] S5: adding the neutralizing agent dropwise to the semi-blocked isocyanate grafted epoxy resin at 50-70° C., and reacting at the temperature for 10-30 minutes to obtain a self-curing waterborne epoxy resin.

[0025] Further, the weight ratio of the chain-extended epoxy resin to diethanolamine is 8.79-8.84:1;

[0026] The amine value of the polyamide is 240-300 mmol / g.

[0027] Furthermore, the molar ratio of the neutralizing agent to the ring-opening agent is 0.48-0.52:1.

[0028] Further, the semi-blocked isocyanate comprises an isocyanate, a catalyst, a solvent and a blocking agent;

[0029] The isocyanate is one or both of toluene diisocyanate and diphenylmethane diisocyanate;

[0030] The catalyst is dibutyltin dilaurate;

[0031] The solvent is one or more of butanone, n-butanol, and methyl isobutyl ketone;

[0032] The sealing agent is one or both of ethylene glycol ethyl ether and diethylene glycol ethyl ether.

[0033] Further, the preparation of semi-blocked isocyanate comprises the following steps:

[0034] Place isocyanate, catalyst and solvent in a four-necked flask equipped with a condenser, a stirrer and a thermometer, stir and heat to 38-40°C, keep warm for 20-30 minutes, then add the blocking agent to the reaction system through a constant pressure dropping funnel, heat to 45-60°C, keep warm for 1-1.5 hours to obtain semi-blocked isocyanate.

[0035] Furthermore, the molar ratio of isocyanate to blocking agent is 1:1.05-1.8.

[0036] According to a second aspect of the present invention, a self-curing waterborne epoxy resin coating comprises the self-curing waterborne epoxy resin described above, and also comprises a pigment and a filler;

[0037] The preparation of the self-curing waterborne epoxy resin coating comprises the following steps: mixing and dispersing the self-curing waterborne epoxy resin, pigment and filler to obtain the self-curing waterborne epoxy resin coating.

[0038] The beneficial effects of the present invention are:

[0039] (1) By introducing polyamide resin, it can play a toughening role; by semi-blocked isocyanate modification, polyurethane curing groups are introduced to make the coating have high corrosion resistance; the resin prepared by the scheme of the present invention only needs to be packaged in a single component, which is convenient for storage and construction;

[0040] (2) After coating with the coating of the present invention, a 20 μm thick coating film is baked at 160° C. for 0.2 h, and the coating hardness is H, the impact strength is greater than 50 cm, the flexibility is level 0, the coating can withstand hot water for a long time, and the neutral salt spray resistance test exceeds 1000 h. DETAILED DESCRIPTION

[0041] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below through specific implementation methods.

[0042] In order to illustrate the scheme and technical advancement of the present invention, the technical scheme and technical application designed are as follows:

[0043] According to a first aspect of the present invention, a self-curing waterborne epoxy resin comprises an epoxy resin, bisphenol A, an accelerator, a ring opener, a diluent, a neutralizer and a semi-blocked isocyanate;

[0044] in:

[0045] The weight ratio of epoxy resin to bisphenol A is 3.60-3.70:1:

[0046] The accelerators are dodecylphenol and N,N-dimethylaminopropylamine;

[0047] The diluent is one or two of alcohol ethers and ketones;

[0048] The neutralizing agent is one or both of acetic acid and lactic acid;

[0049] In semi-blocked isocyanate, the mass fraction of free NCO is 1%-40%.

[0050] In the present invention, (1) the weight ratio of epoxy resin to bisphenol A is preferred. The reason is that if more bisphenol A is used in the epoxy chain extension, the average molecular weight of the epoxy resin after chain extension will be too large, and the excessive viscosity of the system will affect the subsequent ring-opening reaction; if less bisphenol A is used, the average molecular weight of the epoxy resin after chain extension will be too small, affecting the final curing and cross-linking of the coating, and further affecting the corrosion resistance and other properties of the coating. (2) Since the present technical solution uses diethanolamine and polyamide for two-step ring opening (described later), and the ring opening rate of diethanolamine is preferably more than 70%, in the diethanolamine-modified epoxy resin molecule, either the epoxy groups at both ends are ring-opened or only one end of the epoxy groups is not ring-opened. When polyamide is further used for ring opening, only the unopened epoxy groups in the diethanolamine-modified epoxy resin molecule will be ring-opened; after the ring opening of diethanolamine and polyamide, only a small amount of single-end epoxy groups in the polyamide-modified epoxy resin are not ring-opened, so the addition of semi-blocked isocyanate can only react with the unopened epoxy groups, and no strong curing and cross-linking reaction will occur. The self-curing waterborne epoxy resin prepared by the present technical solution can be packaged as a single component and stably stored. (3) As described in (2) above, the mass fraction of free NCO in the semi-blocked isocyanate is preferably 1%-40%, and the effect of single-component packaging and stable storage with the matrix resin can be achieved without the need for fully blocked isocyanate.

[0051] Through the technical solution of the present invention, the introduction of polyamide resin can play a toughening role; through semi-blocked isocyanate modification, polyurethane curing groups are introduced to make the coating highly corrosion-resistant; the resin prepared through the solution of the present invention only needs single-component packaging, which is convenient for storage and construction.

[0052] Preferably, the amount of dodecylphenol is 15%-25% of the total weight of the epoxy resin, bisphenol A and the diluent, the amount of N,N-dimethylaminopropylamine is 0.1%-0.5% of the total weight of the epoxy resin, bisphenol A and the diluent; the amount of the diluent is 25%-35% of the total weight of the epoxy resin and bisphenol A.

[0053] Preferably, the ring-opening agent is diethanolamine and polyamide, and the molar ratio of diethanolamine to polyamide is (0.7-0.8): (0.2-0.3). Diethanolamine and polyamide are selected for two-step ring opening (described later), and the ring opening rate of diethanolamine is preferably more than 70%, so that in the diethanolamine-modified epoxy resin molecule, either the epoxy groups at both ends are ring-opened or only one end of the epoxy group is not ring-opened. When polyamide is further used for ring opening, only the unopened epoxy groups in the diethanolamine-modified epoxy resin molecule will be ring-opened, and the excessive viscosity of the system caused by unlimited grafting will not occur.

[0054] Preferably, the preparation of the self-curing waterborne epoxy resin comprises the following steps:

[0055] S1: Place a four-necked flask equipped with a condenser, a stirrer, and a thermometer in a constant temperature oil bath, add epoxy resin, bisphenol A, and dodecylphenol, stir and heat to 120-125°C, and after bisphenol A is completely dissolved, drop N,N-dimethylaminopropylamine, control the system temperature at 130-150°C, keep warm for 1.5-4h, then cool to 100°C, add diluent, and obtain a chain-extended epoxy resin;

[0056] S2: adding diethanolamine dropwise to the chain-extended epoxy resin, and maintaining the temperature at 50-70° C. for 2-4 hours to obtain a diethanolamine-modified epoxy resin;

[0057] S3: adding polyamide to diethanolamine modified epoxy resin at 100° C. for 0.4-0.5 h, and reacting at constant temperature for 2-3 h to obtain polyamide modified epoxy resin;

[0058] S4: adding the semi-blocked isocyanate to the polyamide-modified epoxy resin at 50-70° C. at a dropping speed of 3-5 s / drop, and keeping the temperature for reaction for 30 min-1 h to obtain a semi-blocked isocyanate-grafted epoxy resin;

[0059] S5: adding the neutralizing agent dropwise to the semi-blocked isocyanate grafted epoxy resin at 50-70° C., and reacting at the temperature for 10-30 minutes to obtain a self-curing waterborne epoxy resin.

[0060] Preferably, the weight ratio of the chain-extended epoxy resin to diethanolamine is 8.79-8.84:1;

[0061] The amine value of the polyamide is 240-300 mmol / g.

[0062] Preferably, the molar ratio of the neutralizer to the ring-opener is 0.48-0.52:1. By designing the molar dosage ratio of the neutralizer to the ring-opener, the neutralizer can react with the amino group in the self-curing waterborne epoxy resin to produce an acid-base neutralization reaction to improve the hydrophilicity of the self-curing waterborne epoxy resin. Too much neutralizer can easily lead to excessive hydrophilicity of the system, which is not conducive to the emulsification of the resin; too little neutralizer can easily lead to poor hydrophilicity of the system, which in turn makes the resin poorly water-soluble, affecting the stability and construction performance of the coating.

[0063] Preferably, the semi-blocked isocyanate comprises an isocyanate, a catalyst, a solvent and a blocking agent;

[0064] The isocyanate is one or both of toluene diisocyanate and diphenylmethane diisocyanate;

[0065] The catalyst is dibutyltin dilaurate;

[0066] The solvent is one or more of butanone, n-butanol, and methyl isobutyl ketone;

[0067] The sealing agent is one or both of ethylene glycol ethyl ether and diethylene glycol ethyl ether.

[0068] Preferably, the preparation of semi-blocked isocyanate comprises the following steps:

[0069] Place isocyanate, catalyst and solvent in a four-necked flask equipped with a condenser, a stirrer and a thermometer, stir and heat to 38-40°C, keep warm for 20-30 minutes, then add the blocking agent to the reaction system through a constant pressure dropping funnel, heat to 45-60°C, keep warm for 1-1.5 hours to obtain semi-blocked isocyanate.

[0070] Preferably, the molar ratio of isocyanate to blocking agent is 1:1.05-1.8. The molar ratio of isocyanate to blocking agent allows the blocking agent to react with the isocyanate (N=C=O, i.e., NCO group) in the isocyanate and the reaction can achieve 60%-99% of the NCO groups being blocked to form a stable -NHCO- structure, which is convenient for mixing and storage with the resin system.

[0071] According to a second aspect of the present invention, a self-curing waterborne epoxy resin coating comprises the self-curing waterborne epoxy resin described above, and also comprises a pigment and a filler;

[0072] The preparation of the self-curing waterborne epoxy resin coating comprises the following steps: mixing and dispersing the self-curing waterborne epoxy resin, pigment and filler to obtain the self-curing waterborne epoxy resin coating.

[0073] Through the above technical scheme, after coating with the coating of the present invention, a 20 μm thick coating film is baked at 160°C for 0.2h, the coating hardness is H, the impact strength is greater than 50cm, the flexibility is level 0, the coating can withstand hot water for a long time, and the neutral salt spray resistance test exceeds 1000h.

[0074] Embodiment 1:

[0075] A self-curing waterborne epoxy resin, the preparation of which comprises the following steps:

[0076] S1: Place a four-necked flask equipped with a condenser, a stirrer, and a thermometer in a constant temperature oil bath, add epoxy resin, bisphenol A, and dodecylphenol, stir and heat to 120-125°C, and after bisphenol A is completely dissolved, drop N,N-dimethylaminopropylamine, control the system temperature at 130-150°C, keep warm for 1.5-4h, then cool to 100°C, add diluent, and obtain a chain-extended epoxy resin;

[0077] S2: adding diethanolamine dropwise to the chain-extended epoxy resin, and maintaining the temperature at 50-70° C. for 2-4 hours to obtain a diethanolamine-modified epoxy resin;

[0078] S3: adding polyamide to diethanolamine modified epoxy resin at 100° C. for 0.4-0.5 h, and reacting at constant temperature for 2-3 h to obtain polyamide modified epoxy resin;

[0079] S4: adding the semi-blocked isocyanate to the polyamide-modified epoxy resin at 50-70° C. at a dropping speed of 3-5 s / drop, and keeping the temperature for reaction for 30 min-1 h to obtain a semi-blocked isocyanate-grafted epoxy resin;

[0080] S5: adding the neutralizing agent dropwise to the semi-blocked isocyanate grafted epoxy resin at 50-70° C., and reacting at the temperature for 10-30 minutes to obtain a self-curing waterborne epoxy resin.

[0081] The preparation of semi-blocked isocyanate comprises the following steps:

[0082] Place isocyanate, catalyst and solvent in a four-necked flask equipped with a condenser, a stirrer and a thermometer, stir and heat to 38-40°C, keep warm for 20-30 minutes, then add the blocking agent to the reaction system through a constant pressure dropping funnel, heat to 45-60°C, keep warm for 1-1.5 hours to obtain semi-blocked isocyanate.

[0083] Preparation method of self-curing waterborne epoxy resin coating:

[0084] The preparation of the self-curing waterborne epoxy resin coating comprises the following steps: mixing and dispersing the self-curing waterborne epoxy resin, pigment and filler to obtain the self-curing waterborne epoxy resin coating.

[0085] The weight ratio of epoxy resin to bisphenol A is 3.60:1, the diluent is ethylene glycol butyl ether, the neutralizer is acetic acid, the mass fraction of free NCO in the semi-blocked isocyanate is 1%, the amount of dodecylphenol is 25% of the total weight of the epoxy resin, bisphenol A and the diluent, the amount of N,N-dimethylaminopropylamine is 0.1% of the total weight of the epoxy resin, bisphenol A and the diluent; the amount of the diluent is 25% of the total weight of the epoxy resin and bisphenol A, the molar ratio of diethanolamine to polyamide is 0.7:0.3, the weight ratio of extended chain epoxy resin to diethanolamine is 8.84:1, the amine value of the polyamide is 240 mmol / g, the molar ratio of the neutralizer to the ring opener is 0.5:1, the isocyanate is diphenylmethane diisocyanate, the solvent is butanone, the blocking agent is ethylene glycol ethyl ether, and the molar ratio of isocyanate to the blocking agent is 1:1.05.

[0086] Embodiment 2:

[0087] Different from Example 1, this embodiment adopts: the weight ratio of epoxy resin to bisphenol A is 3.65:1, the diluent is ethylene glycol butyl ether and butanone, the neutralizer is acetic acid and lactic acid, the mass fraction of free NCO in the semi-blocked isocyanate is 40%, the amount of dodecylphenol is 15% of the total weight of the epoxy resin, bisphenol A and the diluent, the amount of N, N-dimethylaminopropylamine is 0.3% of the total weight of the epoxy resin, bisphenol A and the diluent; the amount of the diluent is The total weight of epoxy resin and bisphenol A is 30%, the molar ratio of diethanolamine to polyamide is 0.75:0.25, the weight ratio of extended chain epoxy resin to diethanolamine is 8.79:1, the amine value of polyamide is 270mmol / g, the molar ratio of neutralizer to ring opener is 0.48:1, the isocyanate is toluene diisocyanate, the solvent is butanone and n-butanol, the blocking agent is ethylene glycol ethyl ether and diethylene glycol ethyl ether, and the molar ratio of isocyanate to blocking agent is 1:1.8.

[0088] Embodiment 3:

[0089] Different from Example 1, this embodiment adopts: the weight ratio of epoxy resin to bisphenol A is 3.70:1, the diluent is butanone, the neutralizer is lactic acid, the mass fraction of free NCO in the semi-blocked isocyanate is 20%, the amount of dodecylphenol is 20% of the total weight of epoxy resin, bisphenol A and diluent, the amount of N,N-dimethylaminopropylamine is 0.5% of the total weight of epoxy resin, bisphenol A and diluent; the amount of diluent is The molar ratio of the amount of the polyamide is 35%, the molar ratio of the diethanolamine to the polyamide is 0.8:0.2, the weight ratio of the extended epoxy resin to the diethanolamine is 8.82:1, the amine value of the polyamide is 300mmol / g, the molar ratio of the neutralizer to the ring-opener is 0.52:1, the isocyanate is toluene diisocyanate and diphenylmethane diisocyanate, the solvent is butanone, n-butanol and methyl isobutyl ketone, the blocking agent is diethylene glycol ethyl ether, and the molar ratio of the isocyanate to the blocking agent is 1:1.65.

[0090] The self-curing waterborne epoxy resin coatings prepared in Example 1, Example 2 and Example 3 were stored in iron cans, and the coatings were taken for coating tests:

[0091] (1) The self-curing water-based epoxy resin coating of Example 1 is applied to the inner cavity of the radiator, the self-curing water-based epoxy resin coating of Example 2 is applied to the inner wall of the heating pipe, and the self-curing water-based epoxy resin coating of Example 3 is applied to the inner wall of the water tank. The coating steps are as follows:

[0092] Surface treatment: Thoroughly remove foreign matter such as oil and rust on the surface of the substrate, and perform phosphating treatment to improve the adhesion and corrosion resistance of the coating.

[0093] Painting steps: inject the paint into the radiator, heating pipe and water tank manually or mechanically, pour out the remaining paint later, wait for the surface to dry naturally, and then put it into the oven or drying tunnel for drying at 100℃ for 20min; then paint according to the above steps, and dry at 160℃ for 40min to obtain the coating.

[0094] The coating was tested and the test results are shown in Table 1.

[0095] Table 1

[0096]

[0097] (2) The self-curing waterborne epoxy resin coatings of Example 1, Example 2 and Example 3 were applied on the phosphating test panels, and the coating steps were as follows:

[0098] Surface treatment: Thoroughly remove foreign matter such as oil and rust on the surface of the test plate, and perform phosphating treatment to improve the adhesion and corrosion resistance of the coating.

[0099] Coating steps: apply the coating to the phosphating test plate by dipping or spraying. After the surface is naturally dry, send it into an oven or drying tunnel for drying at 160°C for 20 minutes to obtain a coating.

[0100] The coating was tested and the test results are shown in Table 2.

[0101] Table 2

[0102]

[0103]

[0104] By performing storage stability test and coating test on the self-curing waterborne epoxy resin coatings of Example 1, Example 2 and Example 3:

[0105] 1. From the storage conditions of Examples 1 to 3, it can be seen that the coating is in a uniform liquid or thick fluid after stirring without agglomeration, and the storage state of the coating in the container is stable.

[0106] 2. It can be seen from Table 1 and Table 2 that the coatings of Examples 1 to 3 have good anti-corrosion performance regardless of whether they are used for internal or external anti-corrosion.

[0107] In summary, through the technical solution of the present invention, a self-curing waterborne epoxy resin and coating which are environmentally friendly, highly anti-corrosive and easy to construct are synthesized, and the preparation method is simple and efficient.

[0108] Finally, it should be noted that the above-described embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some or all of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A self-curing waterborne epoxy resin, characterized in that: Including epoxy resin, bisphenol A, accelerator, ring opener, diluent, neutralizer and semi-blocked isocyanate; in: The weight ratio of epoxy resin to bisphenol A is 3.60-3.70:1: The accelerators are dodecylphenol and N,N-dimethylaminopropylamine; The diluent is one or two of alcohol ethers and ketones; The neutralizing agent is one or both of acetic acid and lactic acid; In semi-blocked isocyanate, the mass fraction of free NCO is 1%-40%.

2. A self-curing waterborne epoxy resin according to claim 1, characterized in that: The dosage of dodecylphenol is 15%-25% of the total weight of epoxy resin, bisphenol A and diluent, the dosage of N,N-dimethylaminopropylamine is 0.1%-0.5% of the total weight of epoxy resin, bisphenol A and diluent; the dosage of diluent is 25%-35% of the total weight of epoxy resin and bisphenol A.

3. A self-curing waterborne epoxy resin according to claim 2, characterized in that: The ring-opening agent is diethanolamine and polyamide, and the molar ratio of diethanolamine to polyamide is (0.7-0.8): (0.2-0.3).

4. A self-curing waterborne epoxy resin according to claim 3, characterized in that: The preparation of self-curing waterborne epoxy resin includes the following steps: S1: Place a four-necked flask equipped with a condenser, a stirrer, and a thermometer in a constant temperature oil bath, add epoxy resin, bisphenol A, and dodecylphenol, stir and heat to 120-125°C, and after bisphenol A is completely dissolved, drop N,N-dimethylaminopropylamine, control the system temperature at 130-150°C, keep warm for 1.5-4h, then cool to 100°C, add diluent, and obtain a chain-extended epoxy resin; S2: adding diethanolamine dropwise to the chain-extended epoxy resin, and maintaining the temperature at 50-70° C. for 2-4 hours to obtain a diethanolamine-modified epoxy resin; S3: adding polyamide to diethanolamine modified epoxy resin at 100° C. for 0.4-0.5 h, and reacting at constant temperature for 2-3 h to obtain polyamide modified epoxy resin; S4: adding the semi-blocked isocyanate to the polyamide-modified epoxy resin at 50-70° C. at a dropping speed of 3-5 s / drop, and keeping the temperature for reaction for 30 min-1 h to obtain a semi-blocked isocyanate-grafted epoxy resin; S5: adding the neutralizing agent dropwise to the semi-blocked isocyanate grafted epoxy resin at 50-70° C., and reacting at the temperature for 10-30 minutes to obtain a self-curing waterborne epoxy resin.

5. A self-curing waterborne epoxy resin according to claim 4, characterized in that: The weight ratio of the chain-extended epoxy resin to diethanolamine is 8.79-8.84:1; The amine value of the polyamide is 240-300 mmol / g.

6. A self-curing waterborne epoxy resin according to claim 5, characterized in that: The molar ratio of the neutralizer to the ring-opener is 0.48-0.52:

1.

7. A self-curing waterborne epoxy resin according to claim 6, characterized in that: Semi-blocked isocyanate includes isocyanate, catalyst, solvent and blocking agent; The isocyanate is one or both of toluene diisocyanate and diphenylmethane diisocyanate; The catalyst is dibutyltin dilaurate; The solvent is one or more of butanone, n-butanol, and methyl isobutyl ketone; The sealing agent is one or both of ethylene glycol ethyl ether and diethylene glycol ethyl ether.

8. A self-curing waterborne epoxy resin according to claim 7, characterized in that: The preparation of semi-blocked isocyanate comprises the following steps: Place isocyanate, catalyst and solvent in a four-necked flask equipped with a condenser, a stirrer and a thermometer, stir and heat to 38-40°C, keep warm for 20-30 minutes, then add the blocking agent to the reaction system through a constant pressure dropping funnel, heat to 45-60°C, keep warm for 1-1.5 hours to obtain semi-blocked isocyanate.

9. A self-curing waterborne epoxy resin according to claim 8, characterized in that: The molar ratio of isocyanate to blocking agent is 1:1.05-1.

8.

10. A self-curing waterborne epoxy resin coating, characterized in that: A self-curing waterborne epoxy resin comprising any one of claims 1 to 9, further comprising a pigment and a filler; The preparation of the self-curing waterborne epoxy resin coating comprises the following steps: mixing and dispersing the self-curing waterborne epoxy resin, pigment and filler to obtain the self-curing waterborne epoxy resin coating.

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