Preparation method and coating of multi-self-crosslinking waterborne epoxy ester resin with formaldehyde self-purification and extremely low VOC (volatile organic compound)

Abstract

The invention relates to the field of coatings, in particular to a preparation method of multi-self-crosslinking waterborne epoxy ester resin with a formaldehyde self-purification function and an extremely low VOC (volatile organic compound) and a coating of the waterborne epoxy ester resin. The waterborne epoxy ester has multiple self-crosslinking modes, a coating film can continuously purify formaldehyde in air in the using process, and the waterborne epoxy ester does not contain any cosolvent and is extremely low in VOC. Main raw materials of the water-based resin comprise vegetable oil fatty acid, acetylcarboxylic acid, epoxy resin, a catalyst, triethylamine, a hydrazide compound, an emulsifier and deionized water. Epoxy ester is prepared from vegetable oil fatty acid, acetylcarboxylic acid and epoxy resin under the catalysis of a catalyst, and then waterborne epoxy ester is prepared through an external emulsification process. When the resin is used for preparing a coating, not only are the fullness and gloss of conventional water-based epoxy ester ensured, but also the drying performance and the tolerance performance are further improved. The coating prepared from the resin is particularly suitable for coating various base materials in the indoor environment, is environment-friendly and can purify indoor air.

Description

Technical Field

[0001] This invention relates to the field of coatings, and more particularly to a method for preparing a waterborne epoxy ester resin with multiple self-crosslinking properties, self-purifying formaldehyde, and extremely low VOC, and the coating thereof. Background Technology

[0002] While traditional solvent-based epoxy ester resins possess excellent overall performance, their high solvent content results in the release of volatile organic compounds into the atmosphere during construction and drying processes. This not only pollutes the environment but also increases the consumption of non-renewable petrochemical resources. Water, with its advantages of being non-toxic, non-flammable, inexpensive, and renewable, can replace organic solvents, reducing emissions and costs while improving the safety of production and construction personnel. With increasing environmental awareness, many researchers have shifted their focus to environmentally friendly waterborne epoxy esters.

[0003] Waterborne epoxy esters use water as a solvent, which can significantly reduce VOC emissions and reduce environmental pollution and harm to the human body. However, most waterborne epoxy ester coatings have the following performance defects: (1) In order to solve the problems of early durability and drying, acrylic monomers are often introduced for modification, but the introduction of acrylic monomers reduces the gloss and fullness of the paint film; (2) Xylene is often used as a solvent in the epoxy ester synthesis process and then removed by vacuum, but a small amount of xylene is still easily left behind. In addition, most waterborne epoxy esters on the market at present require the use of 20-30wt% hydrophilic solvents such as ethylene glycol monobutyl ether as co-solvents, and the VOC of the coating system is still relatively high. Summary of the Invention

[0004] To address the problems existing in the background technology, this invention proposes a method for preparing a waterborne epoxy ester resin with multiple self-crosslinking properties, self-purifying formaldehyde, and extremely low VOCs, comprising the following steps:

[0005] S1. Vegetable oil fatty acids, acetylcarboxylic acid, epoxy resin and catalyst are reacted at 90-120℃ until the acid value is <10mg KOH / g to obtain epoxy ester.

[0006] S2. Cool the epoxy ester prepared in step S1 to 60-90℃, stir and add triethylamine with an epoxy ester acid value of 100%, stir for 30 min-1 h to mix evenly, add an appropriate amount of emulsifier and stir evenly; add deionized water dropwise, then cool to room temperature and add acyl hydrazine compound, stir for 30 min-1 h to obtain waterborne epoxy ester resin.

[0007] Preferably, the weight ratio of each material in step S1 is: vegetable oil fatty acid: acetylcarboxylic acid: epoxy resin: catalyst = 40-50 wt%: 0-10 wt%: 50-60 wt%: 0-0.5 wt%.

[0008] Preferably, the weight ratio of each material in step S2 is epoxy ester: emulsifier: water = 40-50 wt%: 2-8 wt%: 50-60 wt%; the amount of triethylamine added is the weight required to neutralize the acid value of the epoxy ester to 100%; and the molar amount of the acyl hydrazine compound is 51-100% of the molar amount of acetocarboxylic acid.

[0009] Preferably, the vegetable oil fatty acids are one or a mixture of two or more of linseed oil fatty acids, soybean oil fatty acids, cottonseed oil fatty acids, sunflower seed oil fatty acids, tall oil fatty acids, dehydrated castor oil fatty acids, or tung oil fatty acids; the acetocarboxylic acid is one or a mixture of two or more of acetyl C1-C8 carboxylic acids; the epoxy resin is one or a mixture of two or more of E51, E44, E42, E21, or E20; and the catalyst is one or a mixture of two or more of tetraethylammonium bromide, N,N-dimethylbenzylamine, or triphenylphosphine.

[0010] Preferably, the emulsifier is an anionic emulsifier and a nonionic emulsifier, wherein the anionic emulsifier is one or a mixture of two or more of Maxemul 7203 or Maxemul 7201, and the nonionic emulsifier is one or a mixture of two or more of Maxemul 7101 or Maxemul 7102; the acylhydrazine compound is one or a mixture of two or more of oxalate dihydrazine, malonate dihydrazine, succinate dihydrazine, glutarate dihydrazine, adipic acid dihydrazine, cyclohexanedicarboxylic acid dihydrazine, azelaic acid dihydrazine, or sebacate dihydrazine.

[0011] This invention further proposes a waterborne epoxy ester resin coating with multiple self-crosslinking properties, self-purifying formaldehyde, and extremely low VOC. During the film-forming process, as triethylamine volatilizes, the waterborne epoxy ester resin changes from a neutral environment to an acidic environment, and the carbonyl group of acetyl C1-C8 carboxylic acid undergoes self-crosslinking with the acylhydrazine group; the acylhydrazine compound reacts with formaldehyde in the air, irreversibly fixing the formaldehyde in the polymer structure.

[0012] Preferably, during preparation, the above-mentioned waterborne epoxy ester resin, dispersant, drier, wetting agent and color paste are dispersed and mixed evenly at high speed, and a thickener is added to adjust the viscosity and an antifoaming agent is added to remove foam to obtain the coating.

[0013] Preferably, the weight ratio of the materials is as follows: waterborne epoxy resin: water: dispersant: wetting agent: color paste: drying agent: thickener: defoamer = 10-50%: 20-50%: 0.5-1.5%: 0.2-0.5%: 10-50%: 0.1-4%: 0.2-2%: 0.1-0.5%.

[0014] Preferably, the dispersant is at least one of BYK-191, BYK-190, and Orotan 681; the wetting agent is at least one of Surfynol TG, Surfynol AD01, Triton CF-10, and Tego 270; the defoamer is at least one of BYK-022, BYK-011, BYK-093, Tego 822, and Tego 902w; the thickener is at least one of Rheolate299, Acrysol RM-8W, Acrysol RM-12W, and Acrysol RM-5000; and the drying agent is one or more of environmentally friendly water-based iron drying agents, water-based cobalt drying agents, water-based iron, cobalt, and manganese composite drying agents, and their complexes.

[0015] Compared with the prior art, the present invention has the following beneficial technical effects:

[0016] 1. Acid-triggered self-crosslinking: During film formation, the evaporation of the amine neutralizer causes the system to change from neutral to acidic, triggering a highly efficient self-crosslinking reaction between the acetoacetate groups and the hydrazide groups. This significantly compensates for the slow drying caused by oxygen absorption, accelerating drying and early hardening, while maintaining the inherent high gloss and fullness of epoxy esters.

[0017] 2. Formaldehyde Capture and Structural Reinforcement: An excess of hydrazide groups is precisely controlled. During the coating's service life, the excess hydrazide continuously captures formaldehyde from the air, undergoing an irreversible reaction to fix the formaldehyde within the polymer network. This not only achieves air purification but also further enhances the long-term crosslinking density and performance of the coating.

[0018] 3. Intrinsically environmentally friendly process: The synthesis process adopts a solvent-free method (eliminating xylene) and an external emulsification method (requiring no co-solvents such as ethylene glycol monobutyl ether). The only source of VOC in the resin is triethylamine required for neutralization, and its VOC content is far lower than that of existing water-soluble epoxy ester resins.

[0019] Therefore, the resin in this invention integrates three core advantages: rapid curing (self-crosslinking), air purification (formaldehyde capture), and ultra-low VOC. Its drying properties and initial resistance are superior to conventional waterborne epoxy ester resin coatings, making it particularly suitable for indoor coating applications with high requirements for environmental protection and air quality. Detailed Implementation

[0020] Example 1: This example proposes a method for preparing a waterborne epoxy ester resin with multiple self-crosslinking properties, self-purifying formaldehyde, and extremely low VOCs. The steps are as follows:

[0021] In a 1L four-necked flask equipped with a stirrer and thermometer, 199.5g of soybean oil fatty acid, 227.28g of E44 epoxy resin, 34.85g of levulinic acid, and 1.15g of tetraethylammonium bromide were added. The mixture was reacted at 100℃ until the acid value reached 9mgKOH / g to obtain an epoxy ester. The epoxy ester was then cooled to 80℃, and 7.5g of triethylamine, required to neutralize the acid value to 100%, was added. Then, 20g of anionic surfactant Maxemul 7201 (Croda) and 20g of nonionic surfactant Maxemul 7101 (Croda) were added, and the mixture was stirred for 30 minutes. 523.6g of deionized water was added dropwise over a period of 2 hours. After the addition was complete, the mixture was cooled to room temperature, and 31.4g of adipic acid dihydrazide was added. The mixture was filtered, packaged, and the aqueous epoxy ester resin was obtained. The VOC content of this waterborne epoxy ester resin is only 7.17g / L, and it can theoretically purify 1.81g of formaldehyde.

[0022] The raw material composition of the coatings formulated with the above-mentioned waterborne epoxy ester resin is shown in the table below:

[0023]

[0024]

[0025] Example 2: This example proposes a method for preparing a waterborne epoxy ester resin with multiple self-crosslinking properties, self-purifying formaldehyde, and extremely low VOCs. The steps are as follows:

[0026] In a 1L four-necked flask equipped with a stirrer and thermometer, 228g of linseed oil fatty acid, 227.28g of E44 epoxy resin, 23.22g of levulinic acid, and 1.2g of triphenylphosphine were added. The mixture was reacted at 110℃ until the acid value reached 8mgKOH / g to obtain an epoxy ester. The epoxy ester was then cooled to 90℃, and 6.9g of triethylamine, required to neutralize the acid value to 100%, was added. Then, 28.8g of anionic surfactant Maxemul 7201 and 19.2g of nonionic surfactant Maxemul 7101 were added, and the mixture was stirred for 30 minutes. 546.86g of deionized water was added dropwise over a period of 2 hours. After the addition was complete, the mixture was cooled to room temperature, and 26.13g of adipate dihydrazide was added. The mixture was filtered and packaged to obtain an aqueous epoxy ester resin. The VOC content of this waterborne epoxy ester resin is only 6.32g / L. The resin can theoretically purify 3g of formaldehyde when it is completely coated into a film.

[0027] The raw material composition of the coatings formulated with the above-mentioned waterborne epoxy ester resin is shown in the table below:

[0028]

[0029]

[0030] Example 3: This example proposes a method for preparing a waterborne epoxy ester resin with multiple self-crosslinking properties, self-purifying formaldehyde, and extremely low VOCs. The steps are as follows:

[0031] In a 1L four-necked flask equipped with a stirrer and thermometer, 228g of tall oil fatty acid, 196g of E51 epoxy resin, 23.22g of levulinic acid, and 1.12g of tetraethylammonium bromide were added. The mixture was reacted at 110℃ until the acid value reached 8mgKOH / g to obtain an epoxy ester. The epoxy ester was then cooled to 90℃, and 6.47g of triethylamine, required to neutralize the acid value to 100%, was added. Then, 22g of anionic surfactant Maxemul 7203 and 22.8g of nonionic surfactant Maxemul 7101 were added, and the mixture was stirred for 30 minutes. 518.05g of deionized water was added dropwise over a period of 2 hours. After the addition was complete, the mixture was cooled to room temperature, and 31.35g of adipate dihydrazide was added. The mixture was filtered and packaged to obtain an aqueous epoxy ester resin. The VOC content of this waterborne epoxy ester resin is only 6.24g / L. When the resin is completely coated into a film, it can theoretically purify 4.8g of formaldehyde.

[0032] The raw material composition of the coatings formulated with the above-mentioned waterborne epoxy ester resin is shown in the table below:

[0033]

[0034]

[0035] The performance of the waterborne epoxy ester resin coatings in Examples 1, 2, and 3 was compared with that of conventional waterborne epoxy esters on the market. The results are shown in the table below:

[0036]

[0037] Based on the above tables and the problems of slow drying and slow hardness increase of traditional water-based epoxy esters, this invention provides an innovative solution with the following advantages:

[0038] 1. Acid-triggered self-crosslinking: During film formation, the evaporation of the amine neutralizer causes the system to change from neutral to acidic, triggering a highly efficient self-crosslinking reaction between the acetoacetate groups and the hydrazide groups. This significantly compensates for the slow drying caused by oxygen absorption, accelerating drying and early hardening, while maintaining the inherent high gloss and fullness of epoxy esters.

[0039] 2. Formaldehyde Capture and Structural Reinforcement: An excess of hydrazide groups is precisely controlled. During the coating's service life, the excess hydrazide continuously captures formaldehyde from the air, undergoing an irreversible reaction to fix the formaldehyde within the polymer network. This not only achieves air purification but also further enhances the long-term crosslinking density and performance of the coating.

[0040] 3. Intrinsically environmentally friendly process: The synthesis process adopts a solvent-free method (eliminating xylene) and an external emulsification method (requiring no co-solvents such as ethylene glycol monobutyl ether). The only source of VOC in the resin is triethylamine required for neutralization, and its VOC content is far lower than that of existing water-soluble epoxy ester resins.

[0041] Therefore, the resin in this invention integrates three core advantages: rapid curing (self-crosslinking), air purification (formaldehyde capture), and ultra-low VOC. Its drying properties and initial resistance are superior to conventional waterborne epoxy ester resin coatings, making it particularly suitable for indoor coating applications with high requirements for environmental protection and air quality.

[0042] The embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for preparing a waterborne epoxy ester resin with multiple self-crosslinking properties, self-purifying formaldehyde, and extremely low VOCs, characterized in that, Includes the following steps: S1. Vegetable oil fatty acids, acetylcarboxylic acid, epoxy resin and catalyst are reacted at 90-120℃ until the acid value is <10mg KOH / g to obtain epoxy ester. S2. Cool the epoxy ester prepared in step S1 to 60-90℃, stir and add triethylamine with an epoxy ester acid value of 100%, stir for 30 min-1 h to mix evenly, add an appropriate amount of emulsifier and stir evenly; add deionized water dropwise, then cool to room temperature and add acyl hydrazine compound, stir for 30 min-1 h to obtain waterborne epoxy ester resin.

2. The method for preparing the waterborne epoxy ester resin with multiple self-crosslinking properties, self-purifying formaldehyde, and extremely low VOC according to claim 1, characterized in that, The weight ratio of each material in step S1 is as follows: vegetable oil fatty acid: acetylcarboxylic acid: epoxy resin: catalyst = 40-50 wt%: 0-10 wt%: 50-60 wt%: 0-0.5 wt%.

3. The method for preparing the waterborne epoxy ester resin with multiple self-crosslinking properties, self-purifying formaldehyde, and extremely low VOCs according to claim 2, characterized in that, The weight ratio of each material in step S2 is epoxy ester: emulsifier: water = 40-50 wt%: 2-8 wt%: 50-60 wt%; the amount of triethylamine added is the weight required to neutralize the acid value of the epoxy ester to 100%; the molar amount of acyl hydrazine compound is 51-100% of the molar amount of acetocarboxylic acid.

4. The method for preparing the waterborne epoxy ester resin with multiple self-crosslinking properties, self-purifying formaldehyde, and extremely low VOCs according to claim 3, characterized in that, The fatty acids in the vegetable oil are one or a mixture of two or more of the following: linseed oil fatty acids, soybean oil fatty acids, cottonseed oil fatty acids, sunflower seed oil fatty acids, tall oil fatty acids, dehydrated castor oil fatty acids, or tung oil fatty acids. The acetocarboxylic acid is one or a mixture of two or more acetyl C1-C8 carboxylic acids; the epoxy resin is one or a mixture of two or more E51, E44, E42, E21 or E20; The catalyst is one or a mixture of two or more of tetraethylammonium bromide, N,N-dimethylbenzylamine, or triphenylphosphine.

5. The method for preparing the waterborne epoxy ester resin with multiple self-crosslinking, self-purifying formaldehyde, and extremely low VOC according to claim 4, wherein the emulsifier is anionic emulsifier and nonionic emulsifier, wherein the anionic emulsifier is one or a mixture of two or more of Maxemul 7203 or Maxemul 7201, and the nonionic emulsifier is one or a mixture of two or more of Maxemul 7101 or Maxemul 7102; The acylhydrazide compound is one or a mixture of two or more of the following: oxalate dihydrazide, malonate dihydrazide, succinate dihydrazide, glutarate dihydrazide, adipic acid dihydrazide, cyclohexane dicarboxylic acid dihydrazide, azelaic acid dihydrazide, or sebacate dihydrazide.

6. The waterborne epoxy ester resin coating with multiple self-crosslinking properties, self-purifying formaldehyde, and extremely low VOC content as described in any one of claims 1-5, characterized in that... During the film-forming process of the coating, as triethylamine volatilizes, the waterborne epoxy ester resin changes from a neutral environment to an acidic environment, and the carbonyl group of acetyl C1-C8 carboxylic acid undergoes self-crosslinking with the acylhydrazine group; the acylhydrazine compound reacts with formaldehyde in the air, irreversibly fixing the formaldehyde in the polymer structure.

7. The coating according to claim 6, characterized in that, During preparation, the above-mentioned waterborne epoxy ester resin, dispersant, drier, wetting agent and color paste are dispersed and mixed evenly at high speed, and thickener is added to adjust the viscosity and defoamer to remove foam to obtain the coating. During the coating film formation process, as triethylamine volatilizes, the waterborne epoxy ester resin changes from a neutral environment to an acidic environment, and the carbonyl group of acetyl C1-C8 carboxylic acid undergoes self-crosslinking with the acylhydrazine group; the acylhydrazine compound reacts with formaldehyde in the air, irreversibly fixing the formaldehyde in the polymer structure.

8. The coating according to claim 7, characterized in that, The weight ratio of materials used is as follows: waterborne epoxy resin: water: dispersant: wetting agent: color paste: drying agent: thickener: defoamer = 10-50%: 20-50%: 0.5-1.5%: 0.2-0.5%: 10-50%: 0.1-4%: 0.2-2%: 0.1-0.5%.

9. The coating according to claim 8, characterized in that, The dispersant is at least one of BYK-191, BYK-190, and Orotan681; the wetting agent is at least one of Surfynol TG, Surfynol AD01, Triton CF-10, and Tego 270; the defoamer is at least one of BYK-022, BYK-011, BYK-093, Tego 822, and Tego 902w; the thickener is at least one of Rheolate 299, Acrysol RM-8W, Acrysol RM-12W, and Acrysol RM-5000; and the drying agent is one or more of the following: environmentally friendly water-based iron drying agent, water-based cobalt drying agent, water-based iron, cobalt, and manganese composite drying agent, and their complexes.

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