阅读说明：本技术 一种水性环氧固化剂、其制备方法及应用和水性环氧涂料 (Water-based epoxy curing agent, preparation method and application thereof, and water-based epoxy coating ) 是由 邓煜东 闫磊 于 2021-10-29 设计创作，主要内容包括：本申请实施例提供一种水性环氧固化剂、其制备方法及应用和水性环氧涂料,涉及水性环氧涂料领域。本申请以亚胺和甲醛为原料制备一种水性环氧固化剂。本申请提供的水性环氧固化剂可催化水性环氧乳液中环氧基与环氧基之间进行开环固化,添加的水性环氧固化剂的质量为水性环氧乳液的质量的0.5～1％。利用本申请提供的水性环氧固化剂,能有效解决按照活泼氢当量与环氧当量的配比来添加大量的环氧固化剂的问题,从而降低制备水性环氧涂料的成本。(The embodiment of the application provides a water-based epoxy curing agent, a preparation method and application thereof and a water-based epoxy coating, and relates to the field of water-based epoxy coatings. The water-based epoxy curing agent is prepared from imine and formaldehyde. The waterborne epoxy curing agent provided by the application can catalyze the epoxy groups in the waterborne epoxy emulsion to perform ring-opening curing, and the mass of the added waterborne epoxy curing agent is 0.5-1% of that of the waterborne epoxy emulsion. By utilizing the waterborne epoxy curing agent provided by the application, the problem that a large amount of epoxy curing agent is added according to the ratio of active hydrogen equivalent to epoxy equivalent can be effectively solved, so that the cost for preparing the waterborne epoxy coating is reduced.)

1. The waterborne epoxy curing agent is characterized by being prepared by adding 30 parts by weight of formaldehyde solution and/or formaldehyde polymer into 44-1000 parts by weight of imine for reaction.

2. The waterborne epoxy curing agent of claim 1, wherein the imine has the general structural formula:

wherein n is more than or equal to 0, R is H or alkyl with the chain length of C1-5, R¹、R²The imine is selected from one or more compounds with the structural general formula, and the imine is independently alkyl with a chain length of C1-10.

3. The aqueous epoxy curing agent of claim 1 or 2, wherein the imine comprises at least one selected from the group consisting of ethyleneimine, cyclobutylimine, tetrahydropyrrole, piperidine, cyclohexylimine, dimethylamine, diethylamine, dipropylamine, dibutylamine, dipentylamine, dihexylamine, and diheptylamine.

4. The waterborne epoxy curing agent according to claim 1, wherein the formaldehyde comprises at least one selected from the group consisting of 1-40% by mass of an aqueous formaldehyde solution and paraformaldehyde solids.

5. The waterborne epoxy curing agent according to claim 1, wherein the molar ratio of the formaldehyde to the imine is 1:1 to 3.

6. A method for preparing the aqueous epoxy hardener as set forth in any one of claims 1 to 5, comprising the steps of: adding the formaldehyde solution and/or the formaldehyde polymer into the imine for reaction.

7. The preparation method of the water-based epoxy curing agent as claimed in claim 6, wherein the temperature of the imine is controlled to be 0-20 ℃, then the formaldehyde solution and/or the formaldehyde polymer is added into the imine, the temperature is controlled to be 0-15 ℃ in the adding process, and then the reaction is carried out at 20-25 ℃.

8. Use of the aqueous epoxy hardener as claimed in any of claims 1 to 5 as a hardener for aqueous epoxy coatings.

9. A water-borne epoxy paint, which is characterized by mainly comprising a water-borne epoxy emulsion and the water-borne epoxy curing agent as claimed in any one of claims 1 to 5.

10. The water-based epoxy coating material according to claim 9, wherein the amount of the water-based epoxy curing agent added is 0.5 to 1% by mass of the water-based epoxy emulsion.

Technical Field

The application relates to the field of water-based epoxy paint, in particular to a water-based epoxy curing agent, a preparation method and application thereof and water-based epoxy paint.

Background

Epoxy resin refers to a high molecular prepolymer containing two or more epoxy groups and having an aliphatic, alicyclic or aromatic chain segment as a main chain, and has been widely used in the industrial production field of paints and the like due to its excellent adhesion, electrical insulation, thermal stability and mechanical properties. At present, solvent-based epoxy coatings contain organic volatile matters such as benzene series and the like, which can seriously harm the ecological environment and human health, so that the research on the development of the epoxy coatings towards the solvent-free and water-based directions is a necessary trend of the current coating industry, and a water-based epoxy curing agent is an important component of the water-based epoxy coatings and plays a decisive role in the final performance of the water-based epoxy coatings.

Most of the currently developed waterborne epoxy curing agents are synthesized by modified aliphatic amine, and the curing mechanism is that amine in the curing agent structure and epoxy in the epoxy resin structure are subjected to a crosslinking reaction to form a network-like spatial structure, so that the waterborne epoxy curing agent has good comprehensive performance, but the waterborne epoxy curing agent needs to be added according to the ratio of active hydrogen (active hydrogen contained in amine in the curing agent structure) equivalent to epoxy equivalent, so that the addition amount of the curing agent in the epoxy coating is large, and the cost for preparing the epoxy coating is increased.

Therefore, the development of an epoxy curing agent with a small amount of addition is a problem which is urgently needed to be solved at present.

Disclosure of Invention

The embodiment of the application aims to provide a water-based epoxy curing agent, a preparation method and application thereof and a water-based epoxy coating, wherein the water-based epoxy curing agent contains a structural characteristic of tertiary amine, can catalyze ring-opening curing between epoxy groups in a water-based epoxy emulsion, and is added in an amount of 0.5-1% of the mass of the water-based epoxy emulsion, and the addition amount is small, so that the cost for preparing the water-based epoxy coating is reduced.

In a first aspect, an embodiment of the present application provides a water-based epoxy curing agent, which is obtained by adding 30 parts by weight of formaldehyde solution and/or formaldehyde polymer to 44-1000 parts by weight of imine and performing a reaction.

In the implementation process, in such a form, the amino group of the imine reacts with formaldehyde to form a water-based epoxy curing agent with a structure that two tertiary amines are connected through methyl; under the action of tertiary amine, epoxy groups of the epoxy emulsion undergo ring-opening homopolymerization according to anion stepwise polymerization reaction, because nitrogen atoms in the tertiary amine have strong electronegativity and easily attack carbon atoms on the epoxy groups to form oxygen anions, and the oxygen anions can continuously react with another epoxy group in a ring-opening manner to finally generate macromolecules with a net or body-type structure.

In one possible implementation, the imine has the general structural formula:

wherein n is more than or equal to 0, R is H or alkyl with the chain length of C1-5, R¹、R²The alkyl groups are respectively and independently alkyl groups with the chain length of C1-10, and the imine is selected from one or more compounds with the structural general formula.

In the implementation process, the structural general formula of imine belongs to secondary amine, the amido of the secondary amine has strong nucleophilicity, and the imine and formaldehyde undergo nucleophilic reaction to form the aqueous epoxy curing agent with two tertiary amine structures connected through methyl, and other solvents are not required to be added to promote the reaction.

In one possible implementation, the imine comprises at least one selected from the group consisting of ethylenimine, cyclobutylimine, tetrahydropyrrole, piperidine, cyclohexylimine, dimethylamine, diethylamine, dipropylamine, dibutylamine, dipentylamine, dihexylamine, and diheptylamine.

In the implementation process, imine can provide nucleophilic nitrogen atoms to react with carbonyl groups of formaldehyde to form a waterborne epoxy curing agent with two tertiary amine structures connected through methyl groups, so that the catalytic effect is achieved, and compared with a curing agent only containing one tertiary amine structure, the catalytic effect is effectively enhanced.

In one possible implementation mode, the formaldehyde comprises at least one selected from the group consisting of 1-40 mass percent of formaldehyde aqueous solution and paraformaldehyde solid.

In the implementation process, formaldehyde can provide carbonyl to react with amine of imine to form a water-based epoxy curing agent with two tertiary amine structures connected through methyl, thereby playing a catalytic role.

In one possible implementation, the molar ratio of formaldehyde to imine is 1:1 to 3.

In the implementation process, the molar ratio of the formaldehyde to the imine is controlled, so that the carbonyl group of the formaldehyde and the amine group of the imine can be ensured to be completely reacted to form the waterborne epoxy curing agent with the structure that two tertiary amine groups are connected through methyl.

In a second aspect, embodiments of the present application provide a method for preparing a waterborne epoxy curing agent, including the following steps: the formaldehyde solution and/or the oxymethylene polymer are added to the imine to effect a reaction.

In the implementation process, the formaldehyde solution and/or the formaldehyde polymer is contacted with the imine to react and release heat immediately, so the formaldehyde solution and/or the formaldehyde polymer needs to be added into the imine first, and the problem that the reaction temperature is too high and cannot be controlled is avoided.

In a possible implementation mode, the temperature of imine is controlled to be 0-20 ℃, then the formaldehyde solution and/or the formaldehyde polymer are added into the imine, the temperature is controlled to be 0-15 ℃ in the adding process, and then the reaction is carried out at the temperature of 20-25 ℃.

In the implementation process, in the process of adding the formaldehyde solution and/or the formaldehyde polymer into the imine, the reaction between the formaldehyde solution and/or the formaldehyde polymer and the imine releases heat, so that the temperature needs to be controlled in a lower range until the formaldehyde solution and/or the formaldehyde polymer is completely added into the imine, and the problem that the reaction process is influenced by overhigh temperature is avoided, so that the performance of the prepared waterborne epoxy curing agent is poor.

In one possible implementation, the use of a waterborne epoxy curing agent as a curing agent for waterborne epoxy coatings.

In the above realization process, the aqueous epoxy curing agent is indispensable as an important component for preparing the aqueous epoxy coating and plays an important catalytic role.

In one possible implementation, a waterborne epoxy coating consists essentially of a waterborne epoxy curing agent and a waterborne epoxy emulsion.

In the implementation process, the waterborne epoxy curing agent can catalyze epoxy groups in the waterborne epoxy emulsion to carry out ring-opening curing, so that the waterborne epoxy coating can be prepared by adding the waterborne epoxy curing agent into the waterborne epoxy emulsion.

In one possible implementation mode, the addition amount of the water-based epoxy curing agent is 0.5-1% of the mass of the water-based epoxy emulsion.

In the implementation process, the waterborne epoxy curing agent can be used as a catalyst, does not need to be added according to the proportion of active hydrogen equivalent and epoxy equivalent, and has small addition amount in the waterborne epoxy emulsion, thereby reducing the cost for preparing the waterborne epoxy coating.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions of the embodiments of the present application will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

The following specifically describes the waterborne epoxy curing agent, the preparation method and the application thereof, and the waterborne epoxy coating provided in the embodiments of the present application.

The embodiment of the application provides a preparation method of a water-based epoxy curing agent, which is mainly characterized in that 30 parts by weight of formaldehyde solution and/or formaldehyde polymer are added into 44-1000 parts by weight of imine for reaction. For example, the formaldehyde solution is added to the imine to react, or the formaldehyde polymer is added to the imine to react, or the formaldehyde solution and the formaldehyde polymer are added to the imine to react together.

In the raw materials used, the imine may have the general structural formula:

wherein n is more than or equal to 0, R is H or alkyl with the chain length of C1-5, R¹、R²The alkyl groups are respectively and independently alkyl groups with the chain length of C1-10, and the imine is selected from one or more compounds with the structural general formula.

In some embodiments, the imine comprises at least one selected from the group consisting of ethylenimine, cyclobutylimine, tetrahydropyrrole, piperidine, cyclohexylimine, dimethylamine, diethylamine, dipropylamine, dibutylamine, dipentylamine, dihexylamine, and diheptylamine.

The formaldehyde comprises at least one selected from the group consisting of 1-40% by mass of an aqueous formaldehyde solution and paraformaldehyde solids. Optionally, the formaldehyde aqueous solution with the mass fraction of 1-40% is a formaldehyde aqueous solution with the mass fraction of 37%, the paraformaldehyde solid is trioxymethylene solid or tetraformaldehyde solid, or the formaldehyde is a mixture of the formaldehyde aqueous solution with the mass fraction of 37% and the trioxymethylene solid, a mixture of the formaldehyde aqueous solution with the mass fraction of 37% and the tetraformaldehyde solid, or a mixture of the formaldehyde aqueous solution with the mass fraction of 37% and the trioxymethylene solid and the tetraformaldehyde solid. The molar ratio of formaldehyde to imine is 1: 1-3, and can be selected from 1:1.2 to 1.5, for example, 1:1. 1:1.2, 1: 1.5, 1:2 or 1: 3.

in some embodiments, the method of preparing the waterborne epoxy curing agent of the examples herein includes the steps of:

step 1: firstly, controlling the temperature of imine within the range of 0-20 ℃;

step 2: adding formaldehyde into imine, and controlling the temperature to be 0-15 ℃ in the adding process;

and step 3: then reacting at 20-25 ℃.

The embodiment of the application provides a waterborne epoxy curing agent, which is prepared by the preparation method of the waterborne epoxy curing agent, has simple steps and is harmless to the environment. The waterborne epoxy curing agent with the structure that two tertiary amines are connected through methyl can catalyze epoxy groups in waterborne epoxy emulsion to carry out ring-opening curing, and the catalytic effect is good.

In one embodiment, the imine is pyrrolidine, and the formaldehyde is formaldehyde solution with a mass fraction of 37%, and the chemical reaction formula of the pyrrolidine and formaldehyde is as follows according to the above steps:

the correspondingly obtained waterborne epoxy curing agent containsAnd byproducts.

In another embodiment, the imine is piperidine, the formaldehyde is 37% formaldehyde solution, and the chemical reaction formula of piperidine and formaldehyde is as follows:

the correspondingly obtained waterborne epoxy curing agent containsAnd byproducts.

As another embodiment, the imine is selected from cycloheximide, the formaldehyde is selected from 37 mass percent of formaldehyde aqueous solution or trioxymethylene solid, and the chemical reaction formula of the cycloheximide and the formaldehyde is shown as follows according to the steps:

the correspondingly obtained waterborne epoxy curing agent containsAnd byproducts.

In another embodiment, the imine is piperidine and cycloheximide, the formaldehyde is 37% formaldehyde solution, and the chemical reaction formula of piperidine, cycloheximide and formaldehyde is as follows:

the correspondingly obtained waterborne epoxy curing agent containsAnd byproducts.

In another embodiment, the imine is diethylamine, and the formaldehyde is 37% by weight aqueous formaldehyde, and the chemical reaction formula of diethylamine and formaldehyde is as follows according to the above steps:

the correspondingly obtained waterborne epoxy curing agent containsAnd byproducts.

In another embodiment, the imine is diethylamine, the formaldehyde is 37% by weight aqueous solution, and the chemical reaction formula of dipropylamine and formaldehyde is as follows according to the above steps:

the correspondingly obtained waterborne epoxy curing agent containsAnd byproducts.

The embodiment of the application provides a water-based epoxy coating which mainly comprises a water-based epoxy curing agent and a water-based epoxy emulsion. The addition amount of the water-based epoxy curing agent is 0.5-1% of the mass of the water-based epoxy emulsion.

The paint prepared from the water-based epoxy emulsion is matched with a water-based epoxy curing agent for use, can be used for coating an anti-corrosion bottom layer on a metal surface which is not immersed in a water medium, and can also be used for an anti-rust paint in an anti-corrosion environment in the industrial field.

The application method of the water-based epoxy coating comprises the following steps: mixing the paint prepared from the water-based epoxy emulsion with a water-based epoxy curing agent, baking the mixture for 4 to 6 hours at the temperature of between 50 and 70 ℃, then spraying or brushing the mixture on a base material, and curing and drying the formed paint film at room temperature.

The features and properties of the present application are described in further detail below with reference to examples.

Example 1

This example provides a waterborne epoxy coating, which is prepared as follows:

firstly, cooling 118.8 parts by weight of cycloheximide to 20 ℃; and then 81.1 parts by weight of formaldehyde water solution with the mass fraction of 37% is dripped into the epoxy resin, the molar ratio of formaldehyde to cycloheximide is ensured to be 1:1.2, the temperature is controlled to be 15 ℃ in the adding process, and then the epoxy resin is reacted at the temperature of 25 ℃ to obtain the waterborne epoxy curing agent.

The waterborne epoxy curing agent (the addition amount is 0.5 percent of the mass of the epoxy emulsion) prepared in the above is added into paint prepared by a commercial epoxy emulsion (BANCO-2092 epoxy emulsion, the solid content is 60 percent, and the epoxy equivalent is 990g/mol) to obtain the waterborne epoxy coating.

Example 2

This example provides a waterborne epoxy coating, which is prepared as follows:

firstly, cooling 118.8 parts by weight of cycloheximide to 20 ℃; and then adding 30 parts by weight of trioxymethylene solid into the mixture in batches, ensuring that the molar ratio of formaldehyde to cycloheximide is 1:1.2, controlling the temperature to be 15 ℃ in the adding process, and then reacting at 25 ℃ to obtain the water-based epoxy curing agent.

The waterborne epoxy curing agent (the addition amount is 0.5 percent of the mass of the epoxy emulsion) prepared in the above is added into paint prepared by a commercial epoxy emulsion (BANCO-2092 epoxy emulsion, the solid content is 60 percent, and the epoxy equivalent is 990g/mol) to obtain the waterborne epoxy coating.

Example 3

This example provides a waterborne epoxy coating, which is prepared as follows:

firstly, cooling 87.6 parts by weight of diethylamine to 20 ℃; and then 81.1 parts by weight of formaldehyde water solution with the mass fraction of 37% is dripped into the aqueous epoxy hardener, the molar ratio of formaldehyde to diethylamine is ensured to be 1:1.2, the temperature is controlled to be 15 ℃ in the adding process, and then the aqueous epoxy hardener is obtained after the reaction at the temperature of 25 ℃.

The waterborne epoxy curing agent (the addition amount is 0.5 percent of the mass of the epoxy emulsion) prepared in the above is added into paint prepared by a commercial epoxy emulsion (BANCO-2092 epoxy emulsion, the solid content is 60 percent, and the epoxy equivalent is 990g/mol) to obtain the waterborne epoxy coating.

Example 4

This example provides a waterborne epoxy coating, which is prepared as follows:

firstly, cooling 121.2 parts by weight of dipropylamine to 20 ℃; and then 81.1 parts by weight of formaldehyde water solution with the mass fraction of 37% is dripped into the aqueous epoxy curing agent, the molar ratio of formaldehyde to dipropylamine is ensured to be 1:1.2, the temperature is controlled to be 15 ℃ in the adding process, and then the aqueous epoxy curing agent is obtained after reaction at the temperature of 25 ℃.

The waterborne epoxy curing agent (the addition amount is 0.5 percent of the mass of the epoxy emulsion) prepared in the above is added into paint prepared by a commercial epoxy emulsion (BANCO-2092 epoxy emulsion, the solid content is 60 percent, and the epoxy equivalent is 990g/mol) to obtain the waterborne epoxy coating.

Example 5

This example provides a waterborne epoxy coating, which is prepared as follows:

firstly, cooling 102 parts by weight of piperidine to 20 ℃; and then 81.1 parts by weight of formaldehyde water solution with the mass fraction of 37% is dripped into the aqueous epoxy hardener, the molar ratio of formaldehyde to piperidine is ensured to be 1:1.2, the temperature is controlled to be 15 ℃ in the adding process, and then the aqueous epoxy hardener is obtained after the reaction at the temperature of 25 ℃.

The waterborne epoxy curing agent (the addition amount is 0.5 percent of the mass of the epoxy emulsion) prepared in the above is added into paint prepared by a commercial epoxy emulsion (BANCO-2092 epoxy emulsion, the solid content is 60 percent, and the epoxy equivalent is 990g/mol) to obtain the waterborne epoxy coating.

Example 6

This example provides a waterborne epoxy coating, which is prepared as follows:

firstly, cooling 85.2 parts by weight of pyrrolidine to 20 ℃; and then 81.1 parts by weight of formaldehyde water solution with the mass fraction of 37% is dripped into the aqueous epoxy hardener, the molar ratio of formaldehyde to tetrahydropyrrole is ensured to be 1:1.2, the temperature is controlled to be 15 ℃ in the adding process, and then the aqueous epoxy hardener is obtained after the reaction at the temperature of 25 ℃.

The waterborne epoxy curing agent (the addition amount is 0.5 percent of the mass of the epoxy emulsion) prepared in the above is added into paint prepared by a commercial epoxy emulsion (BANCO-2092 epoxy emulsion, the solid content is 60 percent, and the epoxy equivalent is 990g/mol) to obtain the waterborne epoxy coating.

Example 7

This example provides a waterborne epoxy coating, which is prepared as follows:

firstly, cooling 51 parts by weight of piperidine and 42.6 parts by weight of pyrrolidine to 20 ℃; and then 81.1 parts of formaldehyde water solution with the mass fraction of 37% is dripped into the aqueous epoxy resin, the molar ratio of formaldehyde to imine (piperidine and tetrahydropyrrole) is ensured to be 1:1.2, the temperature is controlled to be 15 ℃ in the adding process, and then the aqueous epoxy curing agent is obtained after the reaction at the temperature of 25 ℃.

The waterborne epoxy curing agent (the addition amount is 0.5 percent of the mass of the epoxy emulsion) prepared in the above is added into paint prepared by a commercial epoxy emulsion (BANCO-2092 epoxy emulsion, the solid content is 60 percent, and the epoxy equivalent is 990g/mol) to obtain the waterborne epoxy coating.

Example 8

This example provides a waterborne epoxy coating, which is prepared as follows:

firstly, 198.3 parts by weight of cycloheximide are cooled to 20 ℃; and then 81.1 parts by weight of formaldehyde water solution with the mass fraction of 37% is dripped into the epoxy resin, the molar ratio of formaldehyde to cycloheximide is ensured to be 1:2, the temperature is controlled to be 15 ℃ in the adding process, and then the epoxy resin is reacted at the temperature of 25 ℃ to obtain the waterborne epoxy curing agent.

The waterborne epoxy curing agent (the addition amount is 0.5 percent of the mass of the epoxy emulsion) prepared in the above is added into paint prepared by a commercial epoxy emulsion (BANCO-2092 epoxy emulsion, the solid content is 60 percent, and the epoxy equivalent is 990g/mol) to obtain the waterborne epoxy coating.

Example 9

This example provides a waterborne epoxy coating, which is prepared as follows:

firstly, 297.5 parts by weight of cycloheximide are cooled to 20 ℃; and then 81.1 parts by weight of formaldehyde water solution with the mass fraction of 37% is dripped into the epoxy resin, the molar ratio of formaldehyde to cycloheximide is ensured to be 1:3, the temperature is controlled to be 15 ℃ in the adding process, and then the epoxy resin is reacted at the temperature of 25 ℃ to obtain the waterborne epoxy curing agent.

The waterborne epoxy curing agent (the addition amount is 0.5 percent of the mass of the epoxy emulsion) prepared in the above is added into paint prepared by a commercial epoxy emulsion (BANCO-2092 epoxy emulsion, the solid content is 60 percent, and the epoxy equivalent is 990g/mol) to obtain the waterborne epoxy coating.

Comparative example 1

The comparative example provides a waterborne epoxy coating prepared by the process of:

cycloheximide (added in an amount of 0.5% by mass of the epoxy emulsion) was added to a paint prepared from a commercially available epoxidized emulsion (BANCO-2092 epoxy emulsion, solid content 60%, epoxy equivalent 990g/mol) to obtain a water-based epoxy paint.

Comparative example 2

The comparative example provides a waterborne epoxy coating prepared by the process of:

diethylamine (added in an amount of 0.5% by mass of the epoxy emulsion) was added to a paint prepared from a commercially available epoxidized emulsion (BANCO-2092 epoxy emulsion, solid content 60%, epoxy equivalent 990g/mol) to obtain a water-based epoxy paint.

Comparative example 3

The comparative example provides a waterborne epoxy coating prepared by the process of:

dipropylamine (added in an amount of 0.5% by mass of the epoxy emulsion) was added to a paint prepared from a commercially available epoxidized emulsion (BANCO-2092 epoxy emulsion, solid content 60%, epoxy equivalent 990g/mol) to obtain a water-based epoxy paint.

Comparative example 4

The comparative example provides a waterborne epoxy coating prepared by the process of:

piperidine (added in an amount of 0.5% by mass of the epoxy emulsion) was added to a paint prepared from a commercially available epoxidized emulsion (BANCO-2092 epoxy emulsion, solid content 60%, epoxy equivalent 990g/mol) to obtain a water-based epoxy paint.

Comparative example 5

The comparative example provides a waterborne epoxy coating prepared by the process of:

pyrrolidine (added in an amount of 0.5% by mass of the epoxy emulsion) was added to a paint prepared from a commercially available epoxidized emulsion (BANCO-2092 epoxy emulsion, solid content 60%, epoxy equivalent 990g/mol) to obtain a water-based epoxy paint.

Comparative example 6

The comparative example provides a waterborne epoxy coating prepared by the process of:

a commercially available waterborne epoxy curing agent (BANCO-92 curing agent, active hydrogen equivalent 410g/moL) and a commercially available epoxidized emulsion (BANCO-2092 epoxy emulsion, solid content is 60%, and epoxy equivalent 990g/moL) are compounded according to the proportion of active hydrogen equivalent and epoxy equivalent to obtain the waterborne epoxy coating.

Comparative example 7

The comparative example provides a waterborne epoxy coating prepared by the process of:

a commercially available waterborne epoxy curing agent (BANCO-92 curing agent, active hydrogen equivalent 410g/moL, added in an amount of 0.5% by mass of the epoxy emulsion) was added to a paint prepared from a commercially available epoxidized emulsion (BANCO-2092 epoxy emulsion, solid content 60%, epoxy equivalent 990g/moL) to obtain a waterborne epoxy coating.

Comparative example 8

The comparative example provides a waterborne epoxy coating prepared by the process of:

and (2) mixing a tertiary amine type curing agent: 594 a curing agent (borazane tertiary amine, the amine value is 80-130 mgKOH/g, the adding amount is 0.5 percent of the mass of the epoxy emulsion) is added into a paint prepared from a commercially available epoxy emulsion (BANCO-2092 epoxy emulsion, the solid content is 60 percent, and the epoxy equivalent is 990g/mol) to obtain the water-based epoxy coating.

Examples of the experiments

The coatings prepared in examples 1 to 9 and comparative examples 1 to 8 were used as primers, and specifically, the coatings were first left at 60 ℃ for 6 hours, then sprayed on cold-rolled steel sheet substrates, and left at room temperature for 7 days, and then subjected to performance tests, wherein the hardness and impact resistance of the coatings were measured using an instrument, the adhesion was measured by the one-hundred-grid method, and the water resistance was measured at 40.0 ± 2 ℃, and the results are shown in table 1.

TABLE 1 Performance test results of the coatings

Note: grade of hardness (from soft to hard): 6B, 5B, 4B, 3B, 2B, HB, H, 2H, 3H, 4H, 5H, 6H; grade of adhesion (high to low): 0-5 grade.

Comparing the properties of the coating prepared in example 1 with the properties of the coatings prepared in examples 8 to 9, it can be seen that the molar ratio of formaldehyde to imine was 1:1.2 the performance of the prepared waterborne epoxy curing agent is compared with that of the waterborne epoxy curing agent according to the molar ratio of formaldehyde to imine of 1:2 and 1:3 the performances of the water-based epoxy curing agents respectively prepared are basically consistent, and the effects of the water-based epoxy curing agents in the water-based epoxy paint are equivalent.

The performance of the coatings prepared correspondingly in comparative examples 1-9 and the performance of the coatings prepared correspondingly in comparative examples 1-5 show that the performance of the waterborne epoxy curing agent prepared by the reaction of imine and formaldehyde is significantly better than that of the imine alone as the curing agent.

Comparing the performance of the coatings prepared in examples 1 to 9 with that of the coating prepared in comparative example 6, it can be seen that the performance of the aqueous epoxy curing agent prepared by reacting imine and formaldehyde (the addition amount is 0.5% of the mass of the epoxy emulsion) is equivalent to the performance of the commercial curing agent added according to the ratio of the active hydrogen equivalent to the epoxy equivalent, which indicates that the curing effect of the aqueous epoxy curing agent prepared by reacting imine and formaldehyde can also reach the curing effect of the commercial curing agent added according to the ratio of the equivalents under the condition of a small addition amount.

Comparing the performance of the coatings prepared in examples 1 to 9 with the performance of the coating prepared in comparative example 7, it can be seen that the performance of the aqueous epoxy curing agent prepared by reacting imine and formaldehyde (added in an amount of 0.5% by mass of the epoxy emulsion) is significantly better than that of the commercial curing agent (added in an amount of 0.5% by mass of the epoxy emulsion), indicating that the curing effect of the aqueous epoxy curing agent prepared by reacting imine and formaldehyde is significantly better than that of the commercial curing agent with a small amount of addition.

Comparing the performance of the coatings prepared in examples 1 to 9 with the performance of the coating prepared in comparative example 8, it can be seen that the performance of the aqueous epoxy curing agent prepared by reacting imine and formaldehyde (added in an amount of 0.5% by mass of the epoxy emulsion) is significantly better than that of the commercial tertiary amine curing agent (added in an amount of 0.5% by mass of the epoxy emulsion), which indicates that the curing effect of the aqueous epoxy curing agent prepared by reacting imine and formaldehyde is significantly better than that of the commercial tertiary amine curing agent with a small amount of addition.

From the results of comparing the performances of the coatings prepared in examples 1 to 9 with those of the coatings prepared in comparative examples 6 to 8, it can be seen that the aqueous epoxy curing agent prepared by the reaction of imine and formaldehyde can be used as a catalyst to catalyze the ring-opening curing between epoxy groups of the epoxy emulsion even in the presence of an amount of 0.5% by mass of the epoxy emulsion, and the curing effect is significantly better than that of a commercially available curing agent in the same amount and that of a commercially available tertiary amine-type curing agent in the same amount.

The above description is only an example of the present application and is not intended to limit the scope of the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.