Hydroxyalkylamide curing agent and preparation method thereof

Abstract

The invention discloses a hydroxyalkylamide curing agent and a preparation method thereof, and belongs to the technical field of powder coating curing agents, the curing agent comprises a curing component, the curing component comprises a component A and a component B, an S < i-O-S chain segment is introduced into the component A through 1, 1, 3, 3-tetramethyldisiloxane, and the component B is N, N, N ', N'-tetra (2-hydroxyethyl) adipamide. The curing agent further comprises an anti-yellowing component, and the anti-yellowing component comprises an antioxidant and an ultraviolet light absorber. And compounding the curing component and the anti-yellowing component according to a ratio to obtain the hydroxyalkylamide curing agent. In the application process, the curing agent not only can improve the damp-heat resistance, boiling resistance and thick coating performance of a coating film, but also can improve the yellowing resistance of the coating film.

Description

Technical Field

[0001] The invention belongs to the technical field of powder coating curing agents, and in particular relates to a hydroxyalkylamide curing agent and a preparation method thereof. Background Art

[0002] Hydroxyalkylamide curing agent is a curing agent for pure polyester powder coatings. It is widely used in polyester powder coatings containing carboxyl or anhydride to improve the performance and stability of the coating.

[0003] Hydroxyalkylamide curing agent has some advantages, such as being able to replace the traditional TG IC (triglycidyl isocyanurate) curing agent, having better environmental performance and lower cost. This makes hydroxyalkylamide curing agent more and more widely used in the coating industry. However, compared with TG IC curing agent, hydroxyalkylamide curing agent has poor resistance to moisture and heat and water boiling, and releases low molecular weight compounds (such as water molecules) during curing, which leads to pinhole blistering when the coating is too thick, affecting the thick coating performance of the paint film. In addition, hydroxyalkylamide curing agent has good anti-yellowing performance at low temperatures, but its anti-yellowing performance is poor in high temperature environments. Long-term high temperature exposure may cause the coating film to turn yellow, affecting its service life and aesthetics. Summary of the invention

[0004] The object of the present invention is to provide a hydroxyalkylamide curing agent and a preparation method thereof, so as to solve the problem that the hydroxyalkylamide curing agent has poor resistance to moisture and heat, resistance to boiling water, resistance to yellowing and the like.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A hydroxyalkylamide curing agent includes a curing component, wherein the curing component includes a component A and a component B in a mass ratio of 8:0-2; the structure of the component A is as follows:

[0007] Where X is Where n is an integer from 1 to 3;

[0008] The component B is N,N,N',N'-tetrakis(2-hydroxyethyl)adipamide.

[0009] Furthermore, the curing agent also includes a yellowing-resistant component, and the yellowing-resistant component includes an antioxidant and an ultraviolet absorber;

[0010] The antioxidant is one of a phosphite antioxidant and a hindered phenol antioxidant; the ultraviolet absorber is one of a benzotriazole ultraviolet absorber and a hindered amine ultraviolet absorber.

[0011] Furthermore, the mass ratio of the yellowing-resistant component to the curing component is 1:20-25.

[0012] A method for preparing a hydroxyalkylamide curing agent comprises the following steps:

[0013] The first step is to add the Custer catalyst and methyl enoate to toluene, heat to 60°C under a nitrogen atmosphere, add 1,1,3,3-tetramethyldisiloxane, stir and react for 48 hours, and after the reaction is completed, remove the unreacted raw materials by rotary evaporation under vacuum conditions at 80°C to obtain silicon-containing dimethyl ester; add the silicon-containing dimethyl ester and N,N-bis(2-hydroxyethyl)ethylenediamine to the reaction solvent, then add the alkaline catalyst, and heat the reaction under nitrogen protection to obtain component A, wherein the heating temperature is 85-95°C;

[0014] The second step is to compound component A, component B and the yellowing-resistant component according to a certain proportion to obtain a hydroxyalkylamide curing agent.

[0015] Furthermore, the methyl enoate is one of methyl acrylate, methyl 3-butenoate and methyl 4-pentenoate.

[0016] Furthermore, in the Custer catalyst, xylene is used as a solvent, and the mass fraction of Pt is 2%;

[0017] The molar ratio of methyl enoate to 1,1,3,3-tetramethyldisiloxane is 2:1.1;

[0018] The mass ratio of methyl enoate and Custer catalyst is 5:0.1;

[0019] The molar ratio of methyl enoate and N,N-bis(2-hydroxyethyl)ethylenediamine is 1:1.

[0020] Furthermore, the mass ratio of N,N-bis(2-hydroxyethyl)ethylenediamine, reaction solvent and alkaline catalyst is 1:1-1.2:0.05-0.1.

[0021] Furthermore, the reaction solvent is one of ethylene glycol diethyl ether or diethylene glycol dimethyl ether.

[0022] Furthermore, the alkaline catalyst is one of sodium methoxide or potassium hydroxide.

[0023] Beneficial effects of the present invention:

[0024] In the component A of the hydroxyalkylamide curing agent of the present invention, 1,1,3,3-tetramethyldisiloxane is introduced into the S iOS i segment, thereby increasing the distribution of the hydrophobic structure, improving the hydrophobicity in the cured network, and improving the heat and moisture resistance and water boiling resistance of the cured coating. The introduction of the hydrophobic structure promotes the escape of water molecules during the curing process, reduces the situation in which water molecules cannot escape in time during the curing process to generate pinholes, and the prepared powder coating film has good surface performance and improves the thick coating performance of the coating film.

[0025] The component B in the hydroxyalkylamide curing agent of the present invention has low toxicity, excellent mechanical properties and weather resistance, and by compounding the component A, the component B and the anti-yellowing component under the premise of ensuring product performance, not only the production cost can be reduced, but also the anti-yellowing performance of the coating film can be improved. DETAILED DESCRIPTION

[0026] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] A hydroxyalkylamide curing agent includes a curing component, wherein the curing component includes a component A and a component B; the structure of the component A is as follows:

[0028] Where X is Where n is an integer from 1 to 3;

[0029] The component B is N,N,N',N'-tetrakis(2-hydroxyethyl)adipamide;

[0030] The mass ratio of component A to component B is 8:0-2.

[0031] The curing agent also includes a yellowing-resistant component, and the yellowing-resistant component includes an antioxidant and an ultraviolet absorber;

[0032] Example 1

[0033] This embodiment provides a hydroxyalkylamide curing agent, which is prepared by the following steps:

[0034] The first step is to add a Custer catalyst and methyl acrylate to toluene, heat the mixture to 60°C under a nitrogen atmosphere, add 1,1,3,3-tetramethyldisiloxane, and stir the mixture for 48 hours. After the reaction is completed, remove the unreacted raw materials by rotary evaporation under vacuum conditions at 80°C to obtain a silicon-containing dimethyl ester; xylene is used as a solvent in the Custer catalyst, and the mass fraction of Pt is 2%; the molar ratio of methyl acrylate to 1,1,3,3-tetramethyldisiloxane is 2:1.1; and the mass ratio of methyl acrylate to Custer catalyst is 5:0.1;

[0035] Silicon-containing dimethyl ester and N,N-bis(2-hydroxyethyl)ethylenediamine are added to ethylene glycol diethyl ether, and then potassium hydroxide is added, and the reaction is carried out under nitrogen protection at a temperature of 85°C until no methanol is produced during the reaction, and the reaction is terminated to obtain component A; wherein the amount of N,N-bis(2-hydroxyethyl)ethylenediamine added is calculated based on the amount of methyl acrylate added, and the molar ratio of methyl acrylate to N,N-bis(2-hydroxyethyl)ethylenediamine is 1:1. The mass ratio of N,N-bis(2-hydroxyethyl)ethylenediamine, reaction solvent and alkaline catalyst is 1:1:0.05.

[0036] The second step is to use component A as the curing component, and compound component A (curing component) and the anti-yellowing component according to the proportion to obtain a hydroxyalkylamide curing agent. The mass ratio of the anti-yellowing component to the curing component is 1:20. The anti-yellowing component is a mixture of ultraviolet absorber UV-P and antioxidant 1010 in a mass ratio of 1:1.

[0037] Example 2

[0038] This embodiment provides a hydroxyalkylamide curing agent, which is prepared by the following steps:

[0039] The first step is to add a Custer catalyst and methyl acrylate to toluene, heat the mixture to 60°C under a nitrogen atmosphere, add 1,1,3,3-tetramethyldisiloxane, and stir the mixture for 48 hours. After the reaction is completed, remove the unreacted raw materials by rotary evaporation under vacuum conditions at 80°C to obtain a silicon-containing dimethyl ester; xylene is used as a solvent in the Custer catalyst, and the mass fraction of Pt is 2%; the molar ratio of methyl acrylate to 1,1,3,3-tetramethyldisiloxane is 2:1.1; and the mass ratio of methyl acrylate to Custer catalyst is 5:0.1;

[0040] Silicon-containing dimethyl ester and N,N-bis(2-hydroxyethyl)ethylenediamine are added to ethylene glycol diethyl ether, and then potassium hydroxide is added, and the reaction is carried out under nitrogen protection at a temperature of 95°C until no methanol is produced during the reaction, and the reaction is terminated to obtain component A; wherein the amount of N,N-bis(2-hydroxyethyl)ethylenediamine added is based on the amount of methyl acrylate added, and the molar ratio of methyl acrylate to N,N-bis(2-hydroxyethyl)ethylenediamine is 1:1. The mass ratio of N,N-bis(2-hydroxyethyl)ethylenediamine, reaction solvent and alkaline catalyst is 1:1.2:0.1.

[0041] The second step is to use component A as the curing component, and compound component A (curing component) and the anti-yellowing component according to the proportion to obtain a hydroxyalkylamide curing agent. The mass ratio of the anti-yellowing component to the curing component is 1:22. The anti-yellowing component is a mixture of ultraviolet absorber UV-P and antioxidant 1010 in a mass ratio of 1:1.

[0042] Example 3

[0043] This embodiment provides a hydroxyalkylamide curing agent, which is prepared by the following steps:

[0044] The first step is to add a Custer catalyst and methyl acrylate to toluene, heat the mixture to 60°C under a nitrogen atmosphere, add 1,1,3,3-tetramethyldisiloxane, and stir the mixture for 48 hours. After the reaction is completed, remove the unreacted raw materials by rotary evaporation under vacuum conditions at 80°C to obtain a silicon-containing dimethyl ester; xylene is used as a solvent in the Custer catalyst, and the mass fraction of Pt is 2%; the molar ratio of methyl acrylate to 1,1,3,3-tetramethyldisiloxane is 2:1.1; and the mass ratio of methyl acrylate to Custer catalyst is 5:0.1;

[0045] Silicon-containing dimethyl ester and N,N-bis(2-hydroxyethyl)ethylenediamine are added to ethylene glycol diethyl ether, and then potassium hydroxide is added, and the reaction is carried out under nitrogen protection at a temperature of 95°C until no methanol is produced during the reaction, and the reaction is terminated to obtain component A; wherein the amount of N,N-bis(2-hydroxyethyl)ethylenediamine added is based on the amount of methyl acrylate added, and the molar ratio of methyl acrylate to N,N-bis(2-hydroxyethyl)ethylenediamine is 1:1. The mass ratio of N,N-bis(2-hydroxyethyl)ethylenediamine, reaction solvent and alkaline catalyst is 1:1.2:0.1.

[0046] The second step is to use component A as the curing component, and compound component A (curing component) and the anti-yellowing component according to the proportion to obtain a hydroxyalkylamide curing agent. The mass ratio of the anti-yellowing component to the curing component is 1:25. The anti-yellowing component is a mixture of ultraviolet absorber UV-P and antioxidant 1010 in a mass ratio of 1:1.

[0047] Example 4

[0048] Compared with Example 2, this example is different in that methyl acrylate is replaced with methyl 3-butenoate, and the other raw materials and preparation process remain the same as those in Example 2.

[0049] Example 5

[0050] Compared with Example 2, this example is different in that methyl acrylate is replaced with methyl 4-pentenoate, and the other raw materials and preparation process remain the same as those in Example 2.

[0051] Example 6

[0052] Compared with Example 2, the curing component in this example is replaced by component A and component B, wherein component B is N,N,N',N'-tetrakis(2-hydroxyethyl)adipamide (HAA curing agent, Anhui Keruda New Materials Co., Ltd.); the mass ratio of component A to component B is 4:1. The remaining raw materials and preparation process remain the same as those in Example 2.

[0053] Comparative Example 1

[0054] This embodiment provides a hydroxyalkylamide curing agent, which is prepared by the following steps:

[0055] The first step is to add dimethyl adipate and N,N-bis(2-hydroxyethyl)ethylenediamine to ethylene glycol diethyl ether, then add potassium hydroxide, react under nitrogen protection, the reaction temperature is 85°C, until no methanol is produced during the reaction, and terminate the reaction to obtain component A'; wherein the amount of N,N-bis(2-hydroxyethyl)ethylenediamine added is based on the amount of dimethyl adipate added, and the molar ratio of dimethyl adipate and N,N-bis(2-hydroxyethyl)ethylenediamine is 1:1. The mass ratio of N,N-bis(2-hydroxyethyl)ethylenediamine, reaction solvent and alkaline catalyst is 1:1:0.05.

[0056] The second step is to use component A' as the curing component, and compound component A' (curing component) and the anti-yellowing component according to the proportion to obtain a hydroxyalkylamide curing agent. The mass ratio of the anti-yellowing component to the curing component is 1:20. The anti-yellowing component is a mixture of ultraviolet absorber UV-P and antioxidant 1010 in a mass ratio of 1:1.

[0057] Comparative Example 2

[0058] Compared with Comparative Example 1, this comparative example does not add the anti-yellowing component, and the other raw materials and preparation process remain the same as those of Comparative Example 1.

[0059] Comparative Example 3

[0060] Compared with Example 2, the curing component in this comparative example is replaced by component B, that is, the curing component is only N,N,N',N'-tetrakis(2-hydroxyethyl)adipamide (HAA curing agent, Anhui Korida New Materials Co., Ltd.), and the other raw materials and preparation process remain the same as Example 2.

[0061] The performance tests were performed on the samples prepared in Examples 1 to 6 and Comparative Examples 1 to 3, and the test samples were prepared according to the formula:

[0062] Samples to be tested: 570 parts of carboxyl-terminated saturated polyester resin Anhui Shenjian SJ5122, 30 parts of prepared curing agent, 200 parts of titanium dioxide, 160 parts of barium sulfate, 6 parts of leveling agent, and 3 parts of degassing agent;

[0063] According to the above polyester powder coating formula, the materials are mixed, extruded, tableted and crushed by a twin-screw extruder, and then the tablets are crushed and sieved (180 mesh) to make powder coating. The powder coating is sprayed on the surface treated tinplate substrate with an electrostatic spray gun, with a spraying thickness of 90-100μm, and cured at 150℃ / 15min to obtain a powder coating film.

[0064] The coating index (including coating film appearance, leveling grade, impact, hardness and high temperature baking) is tested according to GB / T21776-2008 "Testing Standard Guide for Powder Coatings and Coatings"; the prepared samples are tested for water boiling resistance, and the color difference of the samples after water boiling (100℃, 2h) is recorded. The color difference is measured according to GB / T7921-2008. And record the test data in the following Tables 1-2:

[0065] Table 1

[0066]

[0067]

[0068] Table 2

[0069]

[0070] It can be seen from Table 1-Table 2 that the samples to be tested prepared using the curing agents prepared in Examples 1-6 of the present invention have good comprehensive properties, such as coating film appearance, impact resistance, etc.

[0071] The curing component includes component A and component B, wherein the organic silicon segment in component A is conducive to improving the heat resistance and hydrolysis resistance of the curing network, and component B has low toxicity and excellent mechanical properties and weather resistance. Under the premise of ensuring product performance, the production cost can be reduced by compounding component A and component B. From the test results, it can be seen that the curing component combined with the yellowing-resistant component increases the distribution of the hydrophobic structure and improves the hydrophobicity in the curing network, thereby improving the water boiling resistance of the coating, and can further improve the yellowing resistance and water boiling resistance of the coating.

[0072] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0073] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A hydroxyalkylamide curing agent, characterized in that The invention comprises a curing component, wherein the curing component comprises a component A and a component B in a mass ratio of 8:0-2; the structure of the component A is as follows: Where X is Where n is an integer from 1 to 3; The component B is N,N,N',N'-tetrakis(2-hydroxyethyl)adipamide.

2. A hydroxyalkylamide curing agent according to claim 1, characterized in that: The curing agent also includes a yellowing-resistant component, and the yellowing-resistant component includes an antioxidant and an ultraviolet absorber; The ultraviolet absorber is one of a benzotriazole ultraviolet absorber and a hindered amine ultraviolet absorber; the antioxidant is one of a phosphite antioxidant and a hindered phenol antioxidant.

3. A hydroxyalkylamide curing agent according to claim 2, characterized in that: The mass ratio of the yellowing-resistant component to the curing component is 1:20-25.

4. A method for preparing the hydroxyalkylamide curing agent according to claim 3, characterized in that: The steps include: The first step is to add the Custer catalyst and methyl enoate to toluene, heat to 60°C under a nitrogen atmosphere, add 1,1,3,3-tetramethyldisiloxane, stir and react for 48 hours, and after the reaction is completed, remove the unreacted raw materials by rotary evaporation under vacuum conditions at 80°C to obtain silicon-containing dimethyl ester; add the silicon-containing dimethyl ester and N,N-bis(2-hydroxyethyl)ethylenediamine to the reaction solvent, then add the alkaline catalyst, and heat the reaction under nitrogen protection to obtain component A, wherein the heating temperature is 85-95°C; The second step is to compound component A, component B and the yellowing-resistant component according to a certain proportion to obtain a hydroxyalkylamide curing agent.

5. The method for preparing a hydroxyalkylamide curing agent according to claim 4, characterized in that: The methyl enoate is one of methyl acrylate, methyl 3-butenoate and methyl 4-pentenoate.

6. The method for preparing a hydroxyalkylamide curing agent according to claim 4, characterized in that: In the Custer catalyst, xylene is used as solvent and the mass fraction of Pt is 2%; The molar ratio of methyl enoate to 1,1,3,3-tetramethyldisiloxane is 2:1.1; The mass ratio of methyl enoate and Custer catalyst is 5:0.1; The molar ratio of methyl enoate and N,N-bis(2-hydroxyethyl)ethylenediamine is 1:

1.

7. The method for preparing a hydroxyalkylamide curing agent according to claim 4, characterized in that: The mass ratio of N,N-bis(2-hydroxyethyl)ethylenediamine, reaction solvent and alkaline catalyst is 1:1-1.2:0.05-0.

1.

8. The method for preparing a hydroxyalkylamide curing agent according to claim 4, characterized in that: The reaction solvent is one of ethylene glycol diethyl ether or diethylene glycol dimethyl ether.

9. The method for preparing a hydroxyalkylamide curing agent according to claim 4, characterized in that: The alkaline catalyst is one of sodium methoxide or potassium hydroxide.

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