Acetoacetic acid esterified water-borne epoxy resin as well as preparation method and application thereof

Abstract

The invention discloses acetoacetic acid esterified water-borne epoxy resin in the technical field of epoxy resin, and the acetoacetic acid esterified water-borne epoxy resin is prepared from the following raw materials in parts by weight: 3-8% of an emulsifier, 0-25% of an epoxy compound, 40-60% of acetoacetic acid esterified epoxy resin, 0-10% of a solvent and 30-50% of deionized water. The problems that an existing waterborne epoxy system is insufficient in chemical resistance, an epoxy-amine system is slowly cured in a low-temperature and high-humidity environment, and the construction efficiency is affected are solved, multifunctional resin with dual reaction activity is created, and waterborne epoxy resin with the environment-friendly advantage is obtained by emulsifying the multifunctional resin through an emulsifier of a special structure.

Description

Technical Field

[0001] This invention relates to the field of epoxy resin technology, and particularly to an acetoacetic acid esterified waterborne epoxy resin. Background Technology

[0002] With increasingly stringent global environmental regulations and a growing emphasis on sustainable development, the coatings industry is undergoing a significant transformation from traditional solvent-based systems to environmentally friendly ones. Waterborne epoxy resins, with their advantages of low VOC (volatile organic compound) content, non-toxicity, odorlessness, and safe application, have become an important development direction in industrial protective coatings, automotive, marine, and architectural coatings. However, traditional waterborne epoxy resins suffer from limitations such as slightly inferior chemical resistance and water resistance after curing, as well as insufficient high-temperature mechanical properties, which to some extent restricts their application in harsh environments.

[0003] To overcome these bottlenecks, chemical modification has become a key approach to improving the performance of waterborne epoxy resins. Acetoacetate modification technology has emerged, which introduces acetoacetate groups into the epoxy resin molecular chain, endowing the resin with new properties. This active group can participate in the epoxy-amine curing and crosslinking reaction, and can also undergo ketone-enol tautomerism, bringing greater molecular design flexibility and synergistic crosslinking ability to the resin system.

[0004] Both CN202111588674.2 and CN202210894041.4 use acetoacetate compounds to react with hydroxyl groups to prepare raw materials for the preparation of biodegradable and remodelable bulk-cured epoxy materials. This is because the enamine bond formed by the reaction of acetoacetate groups with primary amines has dynamic reversibility at high temperatures, which is the core of realizing the dynamic covalent bond characteristics such as material degradation and remodeling. In addition, both patents use low-equivalence epoxy resins, with epoxy equivalents below 300, because high-equivalence epoxy resins containing long chains are not conducive to dynamic processing.

[0005] This invention primarily utilizes the esterification reaction between the hydroxyl groups of an epoxy resin with an epoxy equivalent greater than 300 and a carboxyl-containing acetoacetate derivative (such as ethyl acetoacetate) under the action of a catalyst, grafting the acetoacetate groups onto the epoxy resin molecular chain as side groups or end groups. The goal of this invention is to prepare a high-performance, structurally stable waterborne epoxy resin. It utilizes the acetoacetate group as a means to improve the resin's waterborne adaptability and provide additional crosslinking sites, ultimately aiming to form a stronger and more durable conventional covalent crosslinking network. Its main purpose is for subsequent formulation of waterborne coatings, the performance of which is ultimately reflected in the coating film. The acetoacetate-modified epoxy resin exhibits excellent compatibility and stability during the waterborne process, effectively improving the film's density and crosslinking density. This not only significantly enhances the coating's water resistance, salt spray resistance, and corrosion resistance but also strengthens its adhesion and mechanical strength. These modified resins have been successfully applied in high-performance industrial primers, coil coatings, and electronic insulating coatings, meeting the market demand for high-end products that combine environmental friendliness with excellent durability.

[0006] The technology of acetoacetate-modified epoxy resin has powerfully promoted the functionalization and high-performance development of waterborne epoxy resins, providing a key material foundation for the development of a new generation of green high-performance coatings, and meeting the dual needs of the industry for green transformation and quality upgrading.

[0007] This resin can be widely used in industrial heavy-duty anti-corrosion coatings with extremely demanding requirements (such as ships, containers, and bridge steel structures), high-performance industrial primers, coil coatings, and electronic packaging insulating coatings, with broad market prospects.

[0008] In summary, the core innovation of this patent lies in a novel molecular modification strategy with higher atom economy. Through this strategy, a new waterborne epoxy resin platform technology is created that integrates self-emulsification, double crosslinking, high performance, and multifunctionality, solving several key technical bottlenecks in the current field of waterborne epoxy coatings. Summary of the Invention

[0009] To address the shortcomings of existing technologies, this invention provides an acetoacetic acid esterified waterborne epoxy resin, its preparation method, and its application. It solves the problems of insufficient chemical resistance in existing waterborne epoxy systems and slow curing of epoxy-amine systems under low temperature and high humidity conditions, which affects construction efficiency. Through innovative molecular design and a novel synthetic route, acetoacetic acid ester groups are efficiently introduced into the epoxy resin skeleton in the form of ester bonds while retaining epoxy groups, thus creating a multifunctional resin with dual reactivity. Furthermore, emulsification with a specially structured emulsifier yields an environmentally friendly waterborne epoxy resin.

[0010] The objective of this invention is achieved as follows: An acetoacetic acid esterified waterborne epoxy resin is prepared from raw materials comprising the following parts by weight: 3-8% emulsifier, 0-25% epoxy compound, 40-60% acetoacetic acid esterified epoxy resin, 0-10% solvent, and 30-50% deionized water.

[0011] Furthermore, the emulsifier is prepared by reacting aryl dialdehyde with polyacetoacetate, wherein the molar ratio of the total aldehyde groups of the aryl dialdehyde to the total acetoacetate groups of the polyacetoacetate is ≤1:1.5; the reaction steps are as follows: after mixing and stirring the aryl dialdehyde and the catalyst in a solvent for 10-30 minutes, the polyacetoacetate is added and mixed evenly, and the material is reacted at 30-60℃ for 6-10 hours; the emulsifier contains the following structure: or .

[0012] Furthermore, the aryl dialdehyde is one or a combination of 2,6-naphthyldicarboxaldehyde, terephthalaldehyde, 4,4'-oxobisbenzaldehyde, 2,5-dimethylterephthalaldehyde, 4,4'-sulfobisbenzaldehyde, o-phthalaldehyde, 9,10-anthracenedicarboxaldehyde, isophthalaldehyde, and 4,4-biphenyldicarboxaldehyde.

[0013] Furthermore, the solvent includes dioxane, tetrahydrofuran, acetone, xylene, isopropanol, benzyl alcohol, propylene glycol methyl ether, propylene glycol ethyl ether, ethylene glycol propyl ether, ethylene glycol butyl ether, diethylene glycol butyl ether, and other alcohol ether solvents well known to those skilled in the art; the catalyst is one or a mixture of two of hexahydropyridine, triethylamine, and N,N-dimethylethanolamine, and is used in an amount of 0.1 to 1% by weight of the aryl dialdehyde.

[0014] Furthermore, the polyether acetoacetate structure contains an average of 2-3 acetoacetate groups, an average of 50-150 ethoxy groups, and 0-18 propoxy groups; it is prepared by the acetoacetyl esterification reaction of polyether polyol, wherein the molar ratio of the total hydroxyl groups of the polyether polyol to the total acetoacetate groups of the acetoacetyl esterification reagent is ≤1:1.15; the reaction steps are as follows: dissolving the polyether polyol and the acetoacetyl esterification reagent in an organic solvent, reacting at 100-140℃ for 6-10 hours, and removing the residual alcohol and acetoacetyl esterification reagent under reduced pressure to obtain the corresponding polyether acetoacetate; the small molecule alcohol generated during the reaction is removed in a timely manner.

[0015] Furthermore, the acetoacetic acid esterification agent is one or more of diketene, ethyl acetoacetate, propyl acetoacetate, tert-butyl acetoacetate, pentyl acetoacetate, or heptyl acetoacetate.

[0016] Furthermore, the epoxy compound is an aliphatic epoxy resin and / or an aromatic epoxy resin, containing an average of 1.8 to 2 epoxy functional groups in its structure, and an epoxy equivalent of 320 to 1700 g / eq.

[0017] Furthermore, the acetoacetate-esterified epoxy resin structure contains an average of 1.8-2 epoxy functional groups and 0.4-10 acetoacetate ester groups. It is prepared by acetoacetate esterification of aliphatic epoxy resins and / or aromatic epoxy resins. The preparation method is similar to the acetoacetate esterification process of the polyether polyol described in claim 6, and is within the understanding of those skilled in the art. A representative structural formula is as follows: .

[0018] A method for preparing an acetoacetate-esterified waterborne epoxy resin involves mixing an emulsifier, solvent, epoxy compound, and / or acetoacetate-esterified epoxy resin in a dispersion tank and heating the mixture to 70-85°C. Deionized water is then added dropwise for emulsification. During emulsification, the system is stably maintained at 50-70°C. The dropping rate of the deionized water is 2-5 drops / s, and the shear rate is 2000-4000 r / min. After emulsification, the remaining water is added to dilute the resin. The overall epoxy equivalent of the acetoacetate-esterified waterborne epoxy resin is 400-6000 g / eq, the overall acetoacetate ester group equivalent is 600-4000 g / eq, and the solid content is 45-65%.

[0019] An application of an acetoacetic acid-esterified waterborne epoxy resin in two-component waterborne epoxy coatings and adhesives.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. A hybrid epoxy resin containing both epoxy and acetoacetate groups was prepared via an esterification condensation pathway. This method avoids the consumption of epoxy groups, maximizes the utilization of the resin's functional groups, and offers more precise molecular design and higher efficiency compared to the direct ring-opening addition route via epoxy groups.

[0021] 2. Dual Crosslinking Network: The epoxy groups retained in the resin undergo a classic epoxy-amine addition polymerization reaction with the waterborne amine curing agent, forming a robust three-dimensional network. The introduced acetoacetate groups undergo a low-temperature Michael addition reaction with the primary amine groups in the amine curing agent and coordinate crosslink with polyvalent metal ions (such as Zn²⁺, Ca²⁺) in the formulation. This dual crosslinking mechanism significantly improves the crosslinking density, solving the fundamental problem of low crosslinking density and difficult curing under high temperature and humidity conditions inherent in traditional waterborne epoxy resins.

[0022] 3. The dual crosslinking network (covalent bonds + coordination bonds) significantly improves the crosslinking density and compactness of the coating, giving the coating excellent water resistance, salt spray resistance (>1000 hours) and chemical resistance (especially alkali resistance).

[0023] 4. The Michael addition reaction of acetoacetate and primary amine can proceed rapidly at low temperatures, effectively overcoming the problem of slow curing of epoxy-amine systems at low temperatures and improving construction efficiency.

[0024] 5. The introduction of acetoacetate groups endows the coating with strong metal chelating ability, resulting in stronger adhesion to the substrate (especially metal substrate) and outstanding anti-corrosion performance.

[0025] 6. Cured coatings have potential dynamic properties: Enamine bonds (Michael addition products) and coordination bonds are reversible under certain conditions (such as heat and acid), providing a material basis for the development of remodelable and repairable smart epoxy coatings and expanding application scenarios. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0027] Figure 1 This is the infrared absorption spectrum of acetoacetic acid esterified epoxy resin.

[0028] The figure shows K2 at 3455.7 cm. -1 The disappearance of the hydroxyl peak at E20 indicates that the hydroxyl group in E20 underwent an exchange reaction with the ester group in t-BAA.

[0029] Figure 2 Epoxy resin esterified with acetoacetate 1 H NMR spectrum.

[0030] As can be observed from the figure, the hydroxyl peak at 5.35 ppm disappears, while the methylene peak (4.27 ppm) of the hydroxyl group in the epoxy resin transforms into a methylene peak (5.44 ppm) linked to the ester group. Furthermore, the acetoacetic acid esterified epoxy resin shows a methyl peak of the acetoacetate ester group at 2.16 ppm and a methylene peak of the acetoacetyl group at 3.78 ppm, indicating that an exchange reaction occurred between the acetoacetic acid compound and the epoxy resin. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Example 1 A method for preparing an acetoacetic acid esterified waterborne epoxy resin includes the following steps: Step 1: First, dissolve the polyether polyol and acetoacetic acid esterification reagent in an organic solvent, react at 120°C for 7 hours under nitrogen protection, and remove the alcohol by simultaneous distillation. Remove the residual alcohol and acetoacetic acid esterification reagent by vacuum distillation to obtain acetoacetic acid polyether ester compound intermediates S1-S4. The raw materials and amounts are listed in Table 1.

[0033] Step 2: The aryl dialdehyde and the catalyst are mixed and stirred in an organic solvent for 10-30 minutes, then polyether acetoacetate is added and mixed evenly. The mixture is reacted at 30-60℃ for 6 hours to obtain emulsifiers Y1-Y4. The raw materials and dosages are listed in Table 2.

[0034] Table 1. Polyether Acetate Formulation Table 2 Emulsifier Formulation Example 2 Epoxy resin and acetoacetic acid esterification reagent were dissolved in an organic solvent, reacted as described above, and then distilled under reduced pressure to obtain acetoacetic acid esterified epoxy resins K1~K5. The epoxy equivalent was determined according to GB / T 4612-2008.

[0035] Table 3. Formulation of acetoacetic acid epoxy resin Example 3 The emulsifier K, solvent, epoxy compound and / or acetoacetate-esterified epoxy resin S prepared in Example 1 were added to a dispersion tank according to the amounts shown in Table 3. The mixture was heated to 70-85°C, and deionized water was added dropwise for emulsification. During the emulsification process, the system was stably maintained at 50-70°C, the drop rate of deionized water was 2-5 drops / s, and the shear rate was 2000-4000 r / min. After emulsification, the remaining water was added to dilute the mixture to obtain acetoacetate-esterified waterborne epoxy resin. The overall epoxy equivalent, acetoacetate ester group equivalent and solid content of the obtained epoxy resin are also listed in Table 4.

[0036] Table 4 Formulation of waterborne acetoacetic acid esterified epoxy resin The waterborne epoxy resin prepared in Example 3 and the commercially available AQUAER-3012 waterborne epoxy resin (an emulsion of BPA-type solid epoxy resin with an epoxy equivalent of 1060, produced by Jiangsu Fuqisen) were prepared according to Table 2 to prepare component A. Then, they were mixed with AQUAC-3100 epoxy curing agent (Jiangsu Fuqisen) diluted with propylene glycol methyl ether at a molar ratio of (epoxy group + acetoacetate group) to amine hydrogen of 1:0.8 to form a paint film. The paint film was then sprayed onto polished tinplate and cold-rolled steel plate to prepare a paint film. After the paint film was applied, it was allowed to stand and level for 30 minutes and then placed in an 80°C oven to cure for 2 hours. Performance tests were conducted after 24 hours of placement. The test results were performed according to the following methods or standards: cross-cut adhesion test, GB / T 9286-1998; paint film pencil hardness, GB / T 1731-1993; water resistance at 40℃, GB / T 1733-1993; neutral salt spray resistance, GB / T 1771-2007; paint film impact resistance, GB / T1973-1993; viscosity of waterborne epoxy resin at 25℃ was determined using an NDJ-1 rotational viscometer. Film-forming property test method at 5℃: After leveling the cold-rolled steel sheet with the varnish at room temperature for 30 minutes, it was placed in a 5℃ low-temperature chamber and left for 24 hours. The coating condition was then observed.

[0037] The test results are shown in Table 5.

[0038] Table 4: Formulation of Component A of Waterborne Epoxy Coatings Table 5: Test Results of Waterborne Epoxy Coatings The comparative results show that this invention, through innovative molecular design, efficiently introduces acetoacetate groups into the epoxy resin backbone in the form of ester bonds, while cleverly retaining the epoxy groups, thus creating a multifunctional resin with dual reactivity. Using a self-made emulsifier containing aromatic rings and other components with good compatibility with acetoacetate-esterified epoxy, an acetoacetate-modified waterborne epoxy resin is prepared via phase inversion. Compared with existing technologies, it has the following advantages: To address the issues of insufficient chemical resistance in existing waterborne epoxy systems and slow curing of epoxy-amine systems under low temperature and high humidity conditions, which affects construction efficiency, a waterborne epoxy resin with environmental advantages is obtained by emulsifying it with a specially structured emulsifier.

[0039] The beneficial effects of this invention are as follows: 1. Hybrid epoxy resins containing both epoxy and acetoacetate groups are prepared via an esterification condensation pathway. The number of acetoacetate groups incorporated into the epoxy resin can be effectively controlled by selecting the appropriate raw materials.

[0040] 2. As can be seen from the comparative examples, the crosslinking density is greatly improved after the crosslinking reaction between acetoacetate and amine is increased. The introduction of acetoacetate groups endows the coating with strong metal chelating ability, increases the adhesion of the coating to the metal substrate, and solves the problems of low crosslinking density and difficult curing under high temperature and high humidity conditions of traditional waterborne epoxy resins.

[0041] In summary, the acetoacetate-based waterborne epoxy resin prepared by this invention represents a breakthrough in the structural design and application of the matrix epoxy resin and emulsifier compared to the existing bisphenol A type waterborne epoxy resin system. The corresponding waterborne epoxy coating also exhibits better low-temperature curing properties and chemical resistance.

[0042] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. An acetoacetic acid esterified waterborne epoxy resin, characterized in that, The acetoacetate-esterified waterborne epoxy resin is prepared from the following raw materials in parts by weight: 3-8% emulsifier, 0-25% epoxy compound, 40-60% acetoacetate-esterified epoxy resin, 0-10% solvent, and 30-50% deionized water.

2. The acetoacetic acid esterified waterborne epoxy resin according to claim 1, characterized in that, The emulsifier is prepared by reacting aryl dialdehyde with polyacetoacetate, wherein the molar ratio of the total aldehyde groups of the aryl dialdehyde to the total acetoacetate groups of the polyacetoacetate is ≤1:1.5; the reaction steps are as follows: the aryl dialdehyde and the catalyst are mixed and stirred in a solvent for 10-30 minutes, then polyacetoacetate is added and mixed evenly, and the material is reacted at 30-60℃ for 6-10 hours; the emulsifier contains the following structure: or .

3. The acetoacetic acid esterified waterborne epoxy resin according to claim 2, characterized in that, The aryl dialdehyde is one or a combination of 2,6-naphthyldicarboxaldehyde, terephthalaldehyde, 4,4'-oxobisbenzaldehyde, 2,5-dimethylterephthalaldehyde, 4,4'-sulfobisbenzaldehyde, o-phthalaldehyde, 9,10-anthracenedicarboxaldehyde, isophthalaldehyde, and 4,4-biphenyldicarboxaldehyde.

4. An acetoacetic acid-esterified waterborne epoxy resin according to any one of claims 1-3, characterized in that, The solvents include dioxane, tetrahydrofuran, acetone, xylene, isopropanol, benzyl alcohol, propylene glycol methyl ether, propylene glycol ethyl ether, ethylene glycol propyl ether, ethylene glycol butyl ether, diethylene glycol butyl ether, and other alcohol ether solvents well known to those skilled in the art; the catalyst is one or a mixture of two of hexahydropyridine, triethylamine, and N,N-dimethylethanolamine, and is used in an amount of 0.1 to 1% by weight of the aryl dialdehyde.

5. An acetoacetic acid-esterified waterborne epoxy resin according to any one of claims 1-3, characterized in that, The polyether acetoacetate structure contains an average of 2-3 acetoacetate groups, an average of 50-150 ethoxy groups, and 0-18 propoxy groups. It is prepared by the acetoacetyl esterification reaction of a polyether polyol, wherein the molar ratio of the total hydroxyl groups of the polyether polyol to the total acetoacetate groups of the acetoacetate esterification reagent is ≤1:1.

15. The reaction steps are as follows: the polyether polyol and the acetoacetate esterification reagent are dissolved in an organic solvent and reacted at 100-140℃ for 6-10 hours. The residual alcohol and acetoacetate esterification reagent are removed under reduced pressure to obtain the corresponding polyether acetoacetate. Small molecule alcohols generated during the reaction are removed in a timely manner.

6. The acetoacetic acid esterified waterborne epoxy resin according to claim 5, characterized in that, The acetoacetic acid esterification reagent is one or more of diketene, ethyl acetoacetate, propyl acetoacetate, tert-butyl acetoacetate, pentyl acetoacetate, or heptyl acetoacetate.

7. An acetoacetic acid esterified waterborne epoxy resin according to any one of claims 1-3, characterized in that, The epoxy compound is an aliphatic epoxy resin and / or an aromatic epoxy resin, with an average of 1.8 to 2 epoxy functional groups in its structure and an epoxy equivalent of 320 to 1700 g / eq.

8. An acetoacetic acid esterified waterborne epoxy resin according to any one of claims 1-3, characterized in that, The acetoacetate-esterified epoxy resin described herein contains an average of 1.8 to 2 epoxy functional groups and 0.4 to 10 acetoacetate ester groups. It is prepared via an acetoacetate esterification reaction of aliphatic epoxy resins and / or aromatic epoxy resins. The preparation method is similar to the acetoacetate esterification process of the polyether polyol described in claim 6, and is within the understanding of those skilled in the art. A representative structural formula is as follows: 。 9. A method for preparing an acetoacetic acid esterified waterborne epoxy resin as described in any one of claims 1-8, characterized in that, The emulsifier, solvent, epoxy compound, and / or acetoacetate-esterified epoxy resin are mixed in a dispersion tank and heated to 70-85°C. Deionized water is added dropwise for emulsification. During emulsification, the system is stably maintained at 50-70°C. The dropping rate of deionized water is 2-5 drops / s, and the shear rate is 2000-4000 r / min. After emulsification, the remaining water is added to dilute the emulsified water. The overall epoxy equivalent of the acetoacetate-esterified waterborne epoxy resin is 400-6000 g / eq, the overall acetoacetate ester group equivalent is 600-4000 g / eq, and the solid content is 45-65%.

10. An application of the acetoacetic acid esterified waterborne epoxy resin as described in any one of claims 1-8, characterized in that, Used in two-component waterborne epoxy coatings and adhesives.

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