A high-gloss waterborne epoxy curing agent, its preparation method and application

Abstract

The present invention relates to a high-gloss waterborne epoxy curing agent, its preparation method and application. The high-gloss waterborne epoxy curing agent comprises, by weight: 9-11 parts of m-xylenediamine, 3-24 parts of polyethylene glycol diglycidyl ether, 3-24 parts of epoxy resin E51, 0-10 parts of alcohol ether compound, and 0-30 parts of water. The epoxy curing agent prepared by the present invention uses polyethylene glycol diglycidyl ether and epoxy resin E51 to modify the substrate m-xylenediamine, overcomes the problem of poor compatibility between the curing agent and the waterborne epoxy resin, and ensures good gloss after the paint film is cured.

Description

Technical Field

[0001] The present invention relates to the technical field of coatings, and in particular to a high-gloss waterborne epoxy curing agent, a preparation method thereof, and an application thereof. Background Art

[0002] Epoxy resin is a type of thermosetting polymer material with good adhesion and chemical stability, and is widely used as the resin matrix of coatings. Since solvent-based epoxy coatings contain a large amount of flammable and explosive organic volatile compounds (VOCs) such as benzene and formaldehyde, they pose great harm to the health of operators and have a great impact on the social environment.

[0003] When using epoxy resin, a curing agent needs to be added to cause a curing reaction to generate a three-dimensional network structure to exhibit its excellent properties. Therefore, the curing agent is indispensable in the application of epoxy resin and even plays a decisive role to a certain extent. Since the downstream applications of epoxy coatings have various requirements, such as the duration of the basic drying and activation period, salt spray performance, tolerance, coating requirements, construction requirements, etc., which are all related to the curing agent, the curing agent of waterborne epoxy coatings should be developed specifically according to different application occasions and performance requirements.

[0004] Room-temperature self-drying industrial coatings are widely used in various large-scale outdoor equipment, such as rail transit, bridge protection, signs, containers, ships, floors, etc., and are one of the coatings with the highest demand. The gloss of industrial coatings is an important indicator to measure the appearance quality of the paint film. A high-gloss paint film not only has a beautiful appearance, but also plays a good protective role for the coated object. According to the film-forming mechanism of coatings, it is very easy for oil-based coatings to achieve a high-gloss paint surface. However, since the film-forming process of waterborne coatings is the extrusion and fusion of latex particles after water evaporation, it is difficult for waterborne coatings to obtain a high gloss.

[0005] The Chinese patent literature discloses a high-gloss self-curing epoxy resin and a preparation method thereof (the application publication number is CN113831505 A). The epoxy coating prepared by it has a relatively high gloss, but it needs to be cured into a film at a high temperature of 150°C and cannot be carried out at room temperature. Although the epoxy resin in this patent overcomes the defect of poor gloss of waterborne coatings after curing, it can only be applied to the field of powder coatings. Summary of the Invention

[0006] The technical problem to be solved by the present invention is: The present invention provides a high-gloss waterborne epoxy curing agent, a preparation method thereof, and an application thereof, which overcome the defects that the existing curing agent has poor compatibility with waterborne epoxy resin and insufficient gloss after curing into a film.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0008] In a first aspect, an embodiment of the present invention provides a high-gloss waterborne epoxy curing agent, comprising, by weight:

[0009] 9 to 11 parts of m-xylenediamine, 3 to 24 parts of polyethylene glycol diglycidyl ether, 3 to 24 parts of epoxy resin E51, 0 to 10 parts of an alcohol ether compound, and 0 to 30 parts of water.

[0010] The high-gloss waterborne epoxy curing agent proposed by the present invention uses polyethylene glycol diglycidyl ether (hydrophilic component) and epoxy resin E51 (lipophilic component) to modify the substrate m-xylenediamine, and selects the modification ratio of the above three components to solve the problem of poor compatibility between the curing agent and the waterborne epoxy emulsion, while ensuring the gloss of the cured paint film; among them, compared with high-molecular-weight epoxy resins, epoxy resin E51 has a lower molecular weight and a higher aromatic ring content, and the prepared waterborne curing agent is more compatible with waterborne epoxy resins, making the gloss of the paint film better. And m-xylenediamine can be used as an oil-based room-temperature curing agent due to the presence of aliphatic primary amino groups in its molecular structure; however, due to the water sensitivity of m-xylenediamine and its inability to be exposed to air for a long time, it cannot be directly applied to the waterborne epoxy coating system. Therefore, the present invention uses m-xylenediamine as the modified substrate to ensure the curing activity of the modified curing agent at room temperature. At the same time, the epoxy addition method is used to protect m-xylenediamine to solve its water sensitivity problem, so that the curing agent described in the present invention can be stably applied to waterborne epoxy resin coatings. The schematic diagram of the modification mechanism used in this patent is as follows:

[0011]

[0012] Optionally, the alcohol ether compound is one or more of propylene glycol methyl ether, propylene glycol monobutyl ether, dipropylene glycol methyl ether, ethylene glycol methyl ether, ethylene glycol butyl ether, and dipropylene glycol butyl ether.

[0013] According to the above description, the above alcohol ether compounds can be used as film-forming aids for waterborne epoxy coatings to assist film formation and leveling and provide high gloss.

[0014] Optionally, the alcohol ether compound is propylene glycol methyl ether.

[0015] Optionally, 10 parts of m-xylenediamine.

[0016] Optionally, 5 to 10 parts of polyethylene glycol diglycidyl ether.

[0017] Optionally, 5 to 10 parts of epoxy resin E51.

[0018] In a second aspect, an embodiment of the present invention provides a preparation method of a high-gloss waterborne epoxy curing agent, comprising the following steps:

[0019] S1: Pour m - xylylenediamine into a container and stir it under nitrogen protection at a temperature of 20°C - 70°C;

[0020] S2: Mix epoxy resin E51, polyethylene glycol diglycidyl ether and alcohol ether compound evenly in another container at a mixing temperature of 40°C - 70°C to obtain a mixture;

[0021] S3: Slowly add the mixture obtained in S2 drop - by - drop into m - xylylenediamine, with the reaction temperature being 40°C - 70°C, and keep the temperature for 4h - 8h;

[0022] S4: Raise the temperature to 70°C - 90°C, keep the temperature for 0.5h - 2h, and then add water.

[0023] Among them, for the technical effects corresponding to the preparation method of a high - gloss water - borne epoxy curing agent provided in the second aspect, refer to the relevant description of a high - gloss water - borne epoxy curing agent provided in the first aspect.

[0024] In the third aspect, the embodiments of the present invention provide an application of a high - gloss water - borne epoxy curing agent in industrial coatings. Specific Embodiments

[0025] For better explaining the present invention for easy understanding, the present invention will be described in detail below through specific embodiments.

[0026] To better understand the above - mentioned technical solutions, the exemplary embodiments of the present invention will be described in more detail below. It should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present invention can be understood more clearly and thoroughly, and the scope of the present invention can be fully conveyed to those skilled in the art.

[0027] A high - gloss water - borne epoxy curing agent in the present invention includes, by weight:

[0028] 9 parts - 11 parts of m - xylylenediamine, 3 parts - 24 parts of polyethylene glycol diglycidyl ether, 3 parts - 24 parts of epoxy resin E51, 0 parts - 10 parts of alcohol ether compound, and 0 parts - 30 parts of water. Among them, optionally, the alcohol ether compound is one or more of propylene glycol monomethyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, dipropylene glycol monobutyl ether.

[0029] The specific preparation method of the above - mentioned high - gloss water - borne epoxy curing agent includes the following steps:

[0030] S1: Pour m - xylylenediamine into a container and stir it under nitrogen protection at a temperature of 20°C - 70°C;

[0031] S2: Mix the epoxy resin E51, polyethylene glycol diglycidyl ether, and alcohol ether compound evenly in another container at a mixing temperature of 40°C - 70°C to obtain a mixture;

[0032] S3: Slowly and evenly drip the mixture obtained in S2 into m - xylylenediamine at a reaction temperature of 40°C - 70°C and keep the temperature for 4h - 8h;

[0033] S4: Raise the temperature to 70°C - 90°C, keep the temperature for 0.5h–2h, and then add water.

[0034] Example 1

[0035] S1: Introduce nitrogen into a 100 - ml reactor, pour 10 g of m - xylylenediamine into the reactor, and stir at a temperature of 60°C;

[0036] S2: Take 4.5 g of epoxy resin E51 and 13 g of polyethylene glycol diglycidyl ether, mix them evenly in another container at a mixing temperature of 40°C to obtain a mixture;

[0037] S3: Drip the mixture obtained in S2 into the reactor containing m - xylylenediamine at a speed of 2 drops per second, with a reaction temperature of 60°C, and keep the temperature for 4h;

[0038] S4: Raise the temperature of the system to 80°C and keep the temperature for 0.5h, then 27.5 g of epoxy curing agent can be obtained, with a yield of 100%, an active hydrogen equivalent of 120, a solid content of 100%, and a viscosity of 31200 mPa·s (25°C).

[0039] Example 2

[0040] S1: Introduce nitrogen into a 100 - ml reactor, pour 10 g of m - xylylenediamine into the reactor, and stir at a temperature of 70°C;

[0041] S2: Take 8.6 g of epoxy resin E51, 8.5 g of polyethylene glycol diglycidyl ether, and 3.5 g of propylene glycol methyl ether, mix them evenly in another container at a mixing temperature of 45°C to obtain a mixture;

[0042] S3: Drip the mixture obtained in S2 into the reactor containing m - xylylenediamine at a speed of 1 drop per second, with a reaction temperature of 70°C, and keep the temperature for 5h;

[0043] S4: Raise the temperature of the reaction system in S3 to 85°C and keep the temperature for 1.5h, add 4.3 g of water, then 34.9 g of epoxy curing agent can be obtained, with a yield of 100%, an active hydrogen equivalent of 158 g / EQ, a solid content of 77.6%, and a viscosity of 8930 mPa·s (25°C).

[0044] Example 3

[0045] S1: Introduce nitrogen into a 100 ml reactor, pour 10 g of m-xylenediamine into the reactor, and stir at a temperature of 65 °C.

[0046] S2: Take 8.6 g of epoxy resin E51, 6.4 g of polyethylene glycol diglycidyl ether, and 3.4 g of dipropylene glycol methyl ether, mix them evenly in another container at a mixing temperature of 55 °C to obtain a mixture.

[0047] S3: Drop the mixture obtained in S2 into the reactor containing m-xylenediamine at a rate of 3 drops per second, with the reaction temperature at 65 °C, and keep warm for 6 h.

[0048] S4: Raise the temperature of the reaction system in S3 to 90 °C and keep warm for 1 h, add 4.9 g of water, and 33.3 g of epoxy curing agent can be obtained, with a yield of 100%, an active hydrogen equivalent of 146 g / EQ, a solid content of 75.1%, and a viscosity of 7150 mPa·s (25 °C).

[0049] Comparative Example 1

[0050] S1: Introduce nitrogen into a 100 ml reactor, add 10.0 g of m-xylenediamine to the reactor, and stir at a temperature of 70 °C.

[0051] S2: Weigh 25.7 g of epoxy resin DGEBA (molecular weight 1000 g / mol), 6.4 g of polyethylene glycol diglycidyl ether (the molar amounts of epoxy resin and polyethylene glycol diglycidyl ether are the same as those in Example 3), and 7.1 g of dipropylene glycol methyl ether, mix them evenly in another container, and control the temperature at 45 °C.

[0052] S3: Drop the mixture into the reactor containing m-xylenediamine at a rate of 3 drops per second, control the system temperature at 65 °C, and keep warm for 7 h.

[0053] S4: Raise the temperature of the system in S3 to 85 °C and keep warm for 1.5 h, add 10.5 g of water, and 59.7 g of epoxy curing agent can be obtained, with a yield of 100%, an active hydrogen equivalent of 270 g / EQ, a solid content of 70.5%, and a viscosity of 22530 mPa·s (25 °C).

[0054] Comparative Example 2

[0055] S1: Introduce nitrogen into a 100 ml reactor, add 10.0 g of m-xylenediamine to the reactor, and stir at a temperature of 70 °C.

[0056] S2: Weigh 25.7 g of epoxy resin DGEBA (molecular weight 1000 g / mol), 6.4 g of ethylene glycol diglycidyl ether, and 7.1 g of dipropylene glycol methyl ether, and mix them evenly in another container (the amounts are the same as those in Comparative Example 1, with polyethylene glycol diglycidyl ether replaced by ethylene glycol diglycidyl ether), and control the temperature at 45 °C;

[0057] S3: Drop the mixture into the reactor containing m - xylylenediamine at a rate of 3 drops per second, control the system temperature at 65 °C, and keep it warm for 7 h;

[0058] S4: Raise the system temperature of S3 to 85 °C and keep it warm for 1.5 h, then add 10.5 g of water. The resulting product turns white and shows serious water separation, and it is a non - homogeneous and unstable system. Therefore, it cannot be applied to water - borne epoxy coatings. It can be seen that polyethylene glycol diglycidyl ether is the key to the water - borne modification of the present invention and its application in water - borne epoxy coatings.

[0059] The water - borne epoxy curing agent of the present invention has good dispersibility with water - borne epoxy resin, and the surface drying time of the film - forming substance at room temperature is less than 2 hours. Mix the active hydrogen equivalent to epoxy equivalent ratio of Example 1 - Example 3, Comparative Example 1 and self - made epoxy resin at a ratio of 1:1, and cure the obtained paint film at room temperature (23 degrees, humidity 50%). The performance of the paint film is shown in Table 1:

[0060] Table 1

[0061]

[0062] The main difference between the comparative example and Example 3 is that high - molecular - weight epoxy DGEBA (molecular weight about 1000 g / mol) is used to replace epoxy resin E51. According to the results in Table 1, the gloss of the paint film in the comparative example is lower than that in Example 1 - Example 3. It can be seen that using epoxy resin E51 in the present invention can make the gloss of the coating higher. This is mainly because compared with high - molecular - weight epoxy resin DGEBA, epoxy resin E51 has a smaller molecular weight and a higher aromatic ring content, so the water - borne curing agent prepared has stronger molecular rigidity, and thus better matches the epoxy emulsion, resulting in better gloss of the paint film.

[0063] The present invention adopts the method of adding an epoxide and a polyamine compound, without by - product generation, without the need for a purification step, the viscosity of the product can be adjusted, and the synthesis and preparation process is extremely simple; the modification method used can solve the water - intolerance problem of m - xylylenediamine, enabling this curing agent to be applied to the water - borne epoxy coating system, and the cured coating film has excellent comprehensive performance and excellent gloss.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-gloss waterborne epoxy curing agent, characterized in that, It is composed of the following raw material components by weight parts: 9 - 11 parts of m - xylylenediamine, 3 - 24 parts of polyethylene glycol diglycidyl ether, 3 - 24 parts of epoxy resin E51, 0 - 10 parts of alcohol ether compound, and 0 - 30 parts of water; The preparation method of the high - gloss water - borne epoxy curing agent comprises the following steps: S1: Pour the m - xylylenediamine into a container, and stir under nitrogen protection at a temperature of 20°C - 70°C; S2: Mix the epoxy resin E51, the polyethylene glycol diglycidyl ether, and the alcohol ether compound evenly in another container at a mixing temperature of 40°C - 70°C to obtain a mixture; S3: Slowly and evenly drip the mixture obtained in S2 into the m - xylylenediamine, with the reaction temperature being 40°C - 70°C, and keep the temperature for 4h - 8h; S4: Raise the temperature to 70°C - 90°C and keep the temperature for 0.5h - 2h, then add water.

2. The high-gloss waterborne epoxy curing agent according to claim 1, wherein: The alcohol ether compound is selected from one or more of propylene glycol methyl ether, propylene glycol monobutyl ether, dipropylene glycol methyl ether, ethylene glycol methyl ether, ethylene glycol butyl ether, and dipropylene glycol butyl ether.

3. A high-gloss waterborne epoxy curing agent according to claim 1, wherein: The epoxy equivalent of the polyethylene glycol diglycidyl ether is 250 - 300 g / EQ.

4. A high-gloss waterborne epoxy curing agent according to claim 1, characterized in that: The m - xylylenediamine is 10 parts.

5. A high-gloss waterborne epoxy curing agent according to claim 1, characterized in that: The polyethylene glycol diglycidyl ether is 5 - 10 parts.

6. A high-gloss waterborne epoxy curing agent according to claim 1 or 5, characterized in that: The epoxy resin E51 is 5 - 10 parts.

7. A high-gloss waterborne epoxy curing agent according to claim 1, characterized in that: The temperatures in step S1 and step S3 are 60°C - 70°C respectively.

8. A high-gloss waterborne epoxy curing agent according to claim 1, characterized in that: The temperature in step S2 is 40°C.

9. The application of the high - gloss water - borne epoxy curing agent according to any one of claims 1 - 8 in industrial coatings.

Images