A polyurea-based modified high-thixotropy waterborne epoxy curing agent and a preparation method thereof

Abstract

The application provides a polyurea-based modified high-thixotropy waterborne epoxy curing agent and a preparation method thereof, relates to the technical field of epoxy curing agents, and comprises the following steps: 1) mixing a small molecule aldehyde and diethylenetriamine to perform a reaction, so as to obtain an aldehyde imine-terminated modified amine; 2) performing a reaction on the aldehyde imine-terminated modified amine, a solvent-diluted multifunctional isocyanate and an amino group-terminated methoxy polyether, so as to obtain a hydrophilic modified aldehyde imine-terminated polyurea-based modified resin amine; and 3) mixing the hydrophilic modified aldehyde imine-terminated polyurea-based modified resin amine, an epoxy resin mixture and water to perform a reaction, so as to obtain the polyurea-based modified high-thixotropy waterborne epoxy curing agent. The urea-based modified waterborne epoxy curing agent can endow a paint film with excellent sag resistance when being compounded with a waterborne epoxy emulsion to form a film, the preparation process is simple, the production cost is low, and the application is suitable for large-scale industrialization.

Description

Technical Field

[0001] This invention relates to the field of epoxy curing agent technology, specifically to a polyurea-modified high-thixotropic waterborne epoxy curing agent and its preparation method. Background Technology

[0002] Epoxy resins possess excellent adhesion, corrosion resistance, moldability, and thermal stability, exhibiting outstanding mechanical, thermal, electrical, and chemical resistance properties. Due to these properties, they can be used as coatings, adhesives, and molding materials, finding wide application in electrical, electronic, optical, mechanical, engineering, civil engineering, and sporting goods manufacturing industries. However, waterborne epoxy resin coatings suffer from poor thickening, poor flowability, and are unsuitable for single-coat thick coating applications. Currently, these issues are addressed by adding polyurethane thickeners, silicates, bentonite, etc., but the addition of these materials leads to a decrease in the mechanical and corrosion-resistant properties of the epoxy coating.

[0003] For example, CN112955485A provides a thixotropic agent based on a urea-based compound for curable compositions of polyurethane or SMP; patent EP1152019 describes a thixotropic agent based on a urea compound that uses a polyol instead of a thickener as a carrier. Compared to commercially available polyurea-modified high-thixotropic waterborne epoxy curing agents, the introduction of multifunctional isocyanates results in a more pronounced hyperbranched structure, significantly increasing the crosslinking density and chemical resistance of the curing agent. Therefore, developing a polyurea-modified high-thixotropic waterborne epoxy curing agent is of great significance. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a polyurea-modified high-thixotropic waterborne epoxy curing agent and its preparation method. During the synthesis process, an aldehyde-imine structure is introduced, which has a unique structure of a closed primary amine and a residual secondary amine. By designing a method to fully react the primary amine in the secondary amine group and the terminal aminomethoxy polyether with the isocyanate in the polyfunctional isocyanate, a modified resin amine with a dendritic structure is formed. Then, the aldehyde-imine structure in the modified resin amine is hydrolyzed with water to release the corresponding primary amine, which is then reacted with epoxy resin to obtain the polyurea-modified high-thixotropic waterborne epoxy curing agent, the structural formula of which is:

[0005]

[0006] The polyurea-modified high-thixotropic waterborne epoxy curing agent prepared in this invention has a hydrophilic group R that has an anchoring effect, which can help the system to quickly anchor and prevent sagging. The multiple amino ends of the resin can quickly establish a three-dimensional network structure through relatively strong hydrogen bonds to help prevent dust and sagging. The epoxy-modifying group R1 can provide better compatibility with waterborne epoxy resin, ensuring excellent comprehensive performance.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] To achieve the above objectives, in a first aspect, the present invention provides a method for preparing a polyurea-modified highly thixotropic waterborne epoxy curing agent, comprising the following steps:

[0009] 1) A small molecule aldehyde and diethylenetriamine are mixed and reacted to obtain an aldehyde-imine-terminated modified amine;

[0010] 2) The aldehyde-imide-terminated modified amine, the solvent-diluted polyfunctional isocyanate, and the terminal amino-methoxy polyether are reacted to obtain the hydrophilic modified aldehyde-imide-terminated polyurea-modified resin amine.

[0011] 3) The hydrophilic modified aldehyde-imide-terminated polyurea-modified resin amine, epoxy resin mixture and water are mixed and reacted to obtain polyurea-modified high thixotropic waterborne epoxy curing agent.

[0012] As a further aspect of the present invention, in step 1), the small molecule aldehyde is at least one of propionaldehyde, pentanal, and isobutyraldehyde.

[0013] As a further embodiment of the present invention, the molar ratio of the small molecule aldehyde and diethylenetriamine in step 1) is 2.8 to 4.0:1.0; the reaction temperature in step 1) is 80°C to 120°C, and the reaction time is 6 to 12 hours.

[0014] As a further embodiment of the present invention, the specific operation of step 1) is as follows: a small molecule aldehyde and diethylenetriamine are mixed and reacted, and the water produced in the reaction is removed in time during the reaction. Then, a vacuum operation is performed for 1h to 3h under the conditions of 100℃~120℃ and vacuum degree of -0.1MPa~-0.06MPa (to remove excess small molecule aldehyde) to obtain an aldehyde imine-terminated modified amine.

[0015] As a further aspect of the present invention, in step 2), the polyfunctional isocyanate is an isocyanate with an isocyanate functionality ≥3, and the corresponding product model is at least one of polyether modified isocyanate (Wanhua Aquolin@161), sulfonic acid modified isocyanate (Wanhua Aquolin@268), and HDI trimer (Wanhua HT-100).

[0016] As a further embodiment of the present invention, the solvent in step 2) is at least one of diethylene glycol dimethyl ether and dipropylene glycol dimethyl ether; the terminal amino methoxy polyether in step 2) is at least one of Huntsman M1000, M2070, and M3085.

[0017] As a further embodiment of the present invention, the molar ratio of the aldehyde-imine-terminated modified amine to the isocyanate in step 2) is 1.0:1.05-1.1; the mass ratio of the solvent to the polyfunctional isocyanate in the solvent-diluted polyfunctional isocyanate in step 2) is 0.57-0.8:1.0.

[0018] As a further embodiment of the present invention, the molar ratio of the aldehyde-imine-terminated modified amine and the terminal aminomethoxy polyether in step 2) is 1.0:0.05-0.1; the reaction temperature in step 2) is 0-40°C, and the reaction time is 2-4 hours.

[0019] As a further aspect of the present invention, in step 3), the epoxy resin mixture is a mixture of difunctional epoxy resin and monofunctional glycidyl ether.

[0020] As a further aspect of the present invention, in step 3), the difunctional epoxy resin in the epoxy resin mixture is at least one of E54, E51, and E44; and in step 3), the monofunctional glycidyl ether in the epoxy resin mixture is C1 to C4. 14 At least one of alkyl glycidyl ether, phenyl glycidyl ether, benzyl glycidyl ether, and o-tolyl glycidyl ether.

[0021] As a further embodiment of the present invention, the mass ratio of the hydrophilic modified aldehyde-imide-terminated polyurea-modified resin amine to the water in step 3) is 0.59 to 0.75:1; the molar ratio of the hydrophilic modified aldehyde-imide-terminated polyurea-modified resin amine to the difunctional epoxy and monofunctional glycidyl ether in the epoxy resin mixture in step 3) is 1.0:0.2 to 0.4:0.5 to 1.0.

[0022] As a further embodiment of the present invention, the reaction temperature in step 3) is 60℃~90℃, and the reaction time is 2h~4h.

[0023] Secondly, the present invention also provides a polyurea-modified high thixotropic waterborne epoxy curing agent, which is prepared by the above-mentioned method for preparing polyurea-modified high thixotropic waterborne epoxy curing agent.

[0024] Compared with existing technologies, this invention proposes a polyurea-modified high-thixotropic waterborne epoxy curing agent and its preparation method. Through structural design, an aldehyde-imine structure is introduced during the synthesis process. A supramolecular structure is obtained by chain extension of terminal amino-methoxy polyethers and polyfunctional isocyanates. Then, epoxy modification yields a urea-modified high-thixotropic waterborne epoxy curing agent. Compared to the near absence of polyurea-modified epoxy curing agents on the market, the polyfunctional isocyanate designed in this invention has a more pronounced hyperbranched structure, which significantly increases the crosslinking density and chemical resistance of the curing agent, offering the following beneficial effects:

[0025] This invention introduces an aldehyde-imine structure during the synthesis process, which has a unique structure of a closed primary amine and a residual secondary amine. Through design, the primary amine in the secondary amine group and the terminal aminomethoxy polyether are fully reacted with the isocyanate in the polyfunctional isocyanate to form a modified resin amine with a dendritic structure. Then, the aldehyde-imine structure in the modified resin amine is hydrolyzed with water to release the corresponding primary amine, which is then reacted with epoxy resin to obtain a polyurea-modified high-thixotropic waterborne epoxy curing agent. This structure has the following characteristics: the hydrophilic group R has an anchoring effect, which helps the system to quickly anchor and prevent sagging; the multiple amino ends of the resin can quickly establish a three-dimensional network structure through relatively strong hydrogen bonds to help prevent dust and sagging; and the epoxy modification group R1 can provide better compatibility with waterborne epoxy resin, ensuring excellent overall performance.

[0026] The polyurea-based high thixotropic waterborne epoxy curing agent of the present invention uses inexpensive and readily available raw materials, has low preparation costs, simple processes, and is suitable for mass industrial production.

[0027] These or other aspects of this application will become more apparent from the following description of embodiments. It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only, and are not intended to limit the application. Detailed Implementation

[0028] The present application will be further described below with reference to specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0029] Example 1

[0030] This embodiment provides a polyurea-modified high-thixotropic waterborne epoxy curing agent, the preparation method of which includes the following steps:

[0031] Propanal and diethylenetriamine were mixed at a molar ratio of 2.8:1.0 and reacted at 80°C for 6 hours. Water produced during the reaction was removed in time. Then, a vacuum operation was performed at 100°C and a vacuum degree of -0.06MPa for 2 hours (to remove excess aldehyde) to obtain modified amine A.

[0032] 2) Add 227.03g of polyether-modified isocyanate (Wanhua Aquolin@161), 100g of M2070 amino-terminated polyether amine, and 130g of diethylene glycol dimethyl ether mixture to modified amine A in step 1) (the molar ratio of modified amine A to isocyanate is 1.0:1.0; the molar ratio of amine A to amino-methoxy polyether is 1.0:0.1; the mass ratio of modified amine A to diethylene glycol dimethyl ether is 1.0:0.3), react at 40℃ for 2h to obtain modified amine B;

[0033] 3) Mix urea-modified amine B, 39.22g E51 epoxy resin, 900g water, and 108.7g benzyl glycidyl ether (molar ratio of modified amine B, epoxy resin E51, and benzyl glycidyl ether is 1.0:0.2:0.5; mass ratio of modified amine B to water is 0.59:1), and react at 60℃ for 4h to obtain polyurea-modified high thixotropic waterborne epoxy curing agent.

[0034] Example 2

[0035] This embodiment provides a polyurea-modified high-thixotropic waterborne epoxy curing agent, the preparation method of which includes the following steps:

[0036] 1) Isobutyraldehyde and diethylenetriamine were mixed at a molar ratio of 3.95:1 and reacted at 100°C for 6 hours. During the reaction, the water produced was removed in time. Then, a vacuum operation was performed at 110°C and a vacuum degree of -0.07MPa for 1 hour (to remove excess aldehyde) to obtain isobutyraldehyde-modified diethylenetriamine, i.e., modified amine A.

[0037] 2) Add 225.37g of sulfonic acid modified isocyanate (Wanhua Aquolin@268), 25g of terminal aminomethoxy polyether M1000, and 180g of dipropylene glycol dimethyl ether to modified amine A in step 1) (the molar ratio of modified amine to isocyanate is 1.0:1.1, the molar ratio of amine to hydrogen of modified amine to terminal aminomethoxy polyether is 1:0.05; the mass ratio of modified amine A to diethylene glycol dimethyl ether is 1.0:0.4), and react at 35℃ for 3h to obtain modified amine B;

[0038] 3) Mix urea-modified amine B, 68.18g E44 epoxy resin, 950g water, 44.25g phenyl glycidyl ether, and 66.67g C. 12 -C 14 Alkyl glycidyl ether mixture (modified amine B, epoxy resin E51, phenyl glycidyl ether, C) 12 -C 14 The alkyl glycidyl ether molar ratio was 1.0:0.3:0.25:0.25; the mass ratio of modified amine B to water was 0.59:1. The reaction was carried out at 70℃ for 3 hours to obtain a polyurea-modified high thixotropic waterborne epoxy curing agent.

[0039] Example 3

[0040] This embodiment provides a polyurea-modified high-thixotropic waterborne epoxy curing agent, the preparation method of which includes the following steps:

[0041] 1) Mix pentanal and diethylenetriamine at a molar ratio of 4.0:1 and react at 85°C for 12 hours. Remove the water produced during the reaction in time. Then, perform a vacuum operation at 120°C and a vacuum degree of -0.09MPa for 3 hours (to remove excess aldehyde) to obtain modified amine A.

[0042] 2) Add 231.19g of HDI trimer (Wanhua HT-100), 150g of terminal aminomethoxy polyether M3085, and 159.74g of dipropylene glycol dimethyl ether to modified amine A in step 1) (the molar ratio of modified amine to isocyanate is 1.0:1.1, the molar ratio of amine to hydrogen of modified amine to terminal aminomethoxy polyether is 1:0.1; the mass ratio of modified amine A to diethylene glycol dimethyl ether is 1.0:0.5), and react at 30℃ for 4h to obtain urea-modified amine B;

[0043] 3) Mix urea-modified amine B, 74.07g E54 epoxy resin, 1050g water, and 97.09g o-tolyl glycidyl ether (molar ratio of modified amine B, epoxy resin E44, and benzyl glycidyl ether is 1.0:0.4:0.5; mass ratio of modified amine B to water is 0.75:1), and react at 90℃ for 2h to prepare epoxy-modified resin amine C, thus obtaining polyurea-modified high-thixotropic waterborne epoxy curing agent.

[0044] Comparative Example 1

[0045] It uses water-based epoxy curing agent GZ20 (without polyurea-based water-based epoxy curing agent) produced by Guangdong Huaguoshan Environmental Protection Technology Co., Ltd.

[0046] Performance testing:

[0047] The performance of the waterborne epoxy curing agents of Examples 1-3 and Comparative Example 1 was tested, and the test results are shown in Table 1 below:

[0048] Table 1. Performance test results of the waterborne epoxy curing agents of Examples 1-3 and Comparative Example 1

[0049]

[0050]

[0051] Note:

[0052] Solid content: Tested according to "GB 1725-1979 Determination of Solid Content in Coatings";

[0053] Amine hydrogen equivalent: Tested according to "GB / T 7383-2020 Determination of hydroxyl value of nonionic surfactants";

[0054] Viscosity: Tested according to "GB / T 22235-2008 Determination of viscosity of liquids";

[0055] TI value: The ratio of viscosity measured by the same rotor at different rotational speeds in a rotational viscometer: 3#6r : 3#60r;

[0056] Preparation of the coating film: The epoxy emulsion EP101 of Guangdong Huaguoshan Environmental Protection Technology Co., Ltd. and the water-based epoxy curing agent of Examples 1-3 and Comparative Example 1 were mixed evenly according to the epoxy value and active hydrogen equivalent ratio of 1:0.8. The mixture was then sprayed on an A4 tinplate, leveled for 30 minutes, and then baked in an oven at 50°C for 1 hour. The film thickness was then measured.

[0057] As shown in Table 1, the Ti value of the polyurea-modified high thixotropic waterborne epoxy curing agent of the present invention, after being mixed with the waterborne epoxy emulsion, and the corresponding anti-flow film thickness are significantly higher than those of competing products. This indicates that the polyurea-modified high thixotropic waterborne epoxy curing agent of the present invention has high thixotropic properties in terms of structural design.

[0058] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a polyurea-modified high-thixotropic waterborne epoxy curing agent, characterized in that, The method includes the following steps: 1) A small molecule aldehyde and diethylenetriamine are mixed and reacted to obtain an aldehyde-imine-terminated modified amine; 2) An aldehyde-imide-terminated modified amine, a solvent-diluted polyfunctional isocyanate, and a terminal aminomethoxy polyether are reacted to obtain a hydrophilic modified aldehyde-imide-terminated polyurea-modified resin amine. The polyfunctional isocyanate is an isocyanate with an isocyanate functionality ≥3. The molar ratio of the aldehyde-imide-terminated modified amine to the isocyanate in the polyfunctional isocyanate is 1.0:1.05–1.

1. The mass ratio of the solvent to the polyfunctional isocyanate in the solvent-diluted polyfunctional isocyanate is 0.57–0.8:1.

0. The molar ratio of the aldehyde-imide-terminated modified amine to the terminal aminomethoxy polyether is 1.0:0.05–0.

1. The reaction temperature is 0–40℃, and the reaction time is 2–4 h. 3) A mixture of hydrophilic-modified aldehyde-imide-terminated polyurea-modified resin amine, epoxy resin, and water is reacted to obtain a polyurea-modified high-thixotropic waterborne epoxy curing agent. The epoxy resin mixture is a mixture of difunctional epoxy resin and monofunctional glycidyl ether. The mass ratio of the hydrophilic-modified aldehyde-imide-terminated polyurea-modified resin amine to water is 0.59–0.75:

1. The molar ratio of the hydrophilic-modified aldehyde-imide-terminated polyurea-modified resin amine to the difunctional epoxy and monofunctional glycidyl ether in the epoxy resin mixture is 1.0:0.2–0.4:0.5–1.

0. The reaction temperature is 60℃–90℃, and the reaction time is 2h–4h.

2. The preparation method of the polyurea-modified high-thixotropic waterborne epoxy curing agent as described in claim 1, characterized in that, In step 1), the small molecule aldehyde is at least one of propionaldehyde, pentanal, and isobutyraldehyde.

3. The preparation method of the polyurea-modified high-thixotropic waterborne epoxy curing agent as described in claim 2, characterized in that, The molar ratio of the small molecule aldehyde and diethylenetriamine in step 1) is 2.8–4.0:1.0; the reaction temperature in step 1) is 80℃–120℃, and the reaction time is 6h–12h; the specific operation of step 1) is as follows: the small molecule aldehyde and diethylenetriamine are mixed and reacted, and the water produced in the reaction is removed in time during the reaction. Then, a vacuum operation is performed for 1h–3h under the conditions of 100℃–120℃ and vacuum degree of -0.1MPa–-0.06MPa to obtain the aldehyde imine-terminated modified amine.

4. The preparation method of the polyurea-modified high-thixotropic waterborne epoxy curing agent as described in claim 1, characterized in that, In step 2), the isocyanate is selected from at least one of Wanhua Aquolin@161 polyether-modified isocyanate, Wanhua Aquolin@268 sulfonic acid-modified isocyanate, and Wanhua HT-100 HDI trimer.

5. The preparation method of the polyurea-modified high-thixotropic waterborne epoxy curing agent as described in claim 1, characterized in that, The solvent in step 2) is at least one of diethylene glycol dimethyl ether and dipropylene glycol dimethyl ether; the terminal amino methoxy polyether in step 2) is at least one of Huntsman M1000, M2070 and M3085.

6. The preparation method of the polyurea-modified high-thixotropic waterborne epoxy curing agent as described in claim 1, characterized in that, In step 3), the difunctional epoxy resin in the epoxy resin mixture is at least one of E54, E51, and E44; in step 3), the monofunctional glycidyl ether in the epoxy resin mixture is C1 to C4. 14 At least one of alkyl glycidyl ether, phenyl glycidyl ether, benzyl glycidyl ether, and o-tolyl glycidyl ether.

7. A polyurea-modified high-thixotropic waterborne epoxy curing agent, characterized in that, It is prepared by the method of preparing polyurea-modified high thixotropic waterborne epoxy curing agent according to any one of claims 1-6.

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