Polyurea-based modified high-thixotropy waterborne epoxy curing agent and preparation method thereof

Abstract

The invention provides a polyurea-based modified high-thixotropy waterborne epoxy hardener and a preparation method thereof, and relates to the technical field of epoxy hardeners, the method comprises the following steps: 1) mixing small molecular aldehyde and diethylenetriamine for reaction to obtain aldimine-terminated modified amine; (2) carrying out reaction on the aldimine-terminated modified amine, polyfunctional isocyanate diluted by a solvent and amino-terminated methoxy polyether, so as to obtain hydrophilic modified aldimine-terminated polyurea-based modified resin amine; and 3) mixing the hydrophilic modified aldimine-terminated polyurea-based modified resin amine, the epoxy resin mixture and water for reaction to obtain the polyurea-based modified high-thixotropy waterborne epoxy curing agent. The carbamido modified waterborne epoxy curing agent and waterborne epoxy emulsion are compounded to form a film, so that a paint film can be endowed with excellent anti-sagging performance, the preparation process is simple, the production cost is low, and the carbamido modified waterborne epoxy curing agent is suitable for large-scale industrial application.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of epoxy curing agents, and particularly relates to a polyurea-based modified high-thixotropy waterborne epoxy curing agent and a preparation method thereof. BACKGROUND

[0002] Epoxy resin has excellent bonding, corrosion resistance, moldability and thermal stability, and has very excellent performance in mechanics, heat, electricity and chemical resistance. Due to these functions and properties, it can be used as a coating, adhesive and molding material, and has been widely used in the fields of electrical, electronic, optical machinery, engineering technology, civil construction and cultural and sports product manufacturing. However, waterborne epoxy resin coating has the characteristics of poor thickening, poor sagging, and is not suitable for single-pass film forming thick coating construction. At present, it can only be solved by adding polyurethane thickening agent, silicon, bentonite and the like. The addition of these materials will lead to the decrease of the mechanical properties and corrosion resistance of the epoxy coating.

[0003] For example, CN112955485A provides a thixotropic agent for a urea-based compound of a curable composition for polyurethane or SMP; and patent EP1152019 describes a thixotropic agent based on a urea compound, which uses a polyol instead of a thickening agent as a carrier. There are almost no polyurea-based modified high-thixotropy waterborne epoxy curing agents on the market, and the introduction of multifunctional isocyanate has a more obvious hyperbranched structure, which can significantly improve the crosslinking density of the curing agent and improve the chemical resistance of the curing agent. Therefore, it is of great significance to develop a polyurea-based modified high-thixotropy waterborne epoxy curing agent. SUMMARY

[0004] Therefore, the purpose of the present application is to provide a polyurea-based modified high-thixotropy waterborne epoxy curing agent and a preparation method thereof. In the synthesis process, an aldimine structure is introduced, which has a special structure of closed primary amine and residual secondary amine. By designing, the secondary amine group and the primary amine in the terminal aminomethoxy polyether are fully reacted with the isocyanate in the multifunctional isocyanate to form a modified resin amine with a dendritic structure. Then, the aldimine structure in the modified resin amine is hydrolyzed with water to release the corresponding primary amine, which is then reacted with the epoxy resin to obtain a polyurea-based modified high-thixotropy waterborne epoxy curing agent, and the structural formula is as follows:

[0005]

[0006] The polyurea-based modified high-thixotropy waterborne epoxy curing agent prepared by the present application has an anchoring effect of the hydrophilic group R, which can help the system to quickly anchor and prevent sagging. The resin-like multiple amino ends can quickly establish a three-dimensional network structure through strong hydrogen bonds to help prevent dust and sagging. The epoxy modification group R1 can provide better compatibility with waterborne epoxy resin and ensure excellent comprehensive performance.

[0007] To achieve the above object, the present application provides the following technical solutions.

[0008] Based on the above object, in the first aspect, the present application provides a preparation method of a polyurea-based modified high-thixotropy waterborne epoxy curing agent, comprising the following steps:

[0009] 1) mixing and reacting a small molecule aldehyde and diethylenetriamine to obtain an aldehyde imine-terminated modified amine;

[0010] 2) reacting the aldehyde imine-terminated modified amine, a solvent-diluted multifunctional isocyanate, and an amino methoxy polyether to obtain a hydrophilic modified aldehyde imine-terminated polyurea-based modified resin amine;

[0011] 3) mixing and reacting the hydrophilic modified aldehyde imine-terminated polyurea-based modified resin amine, an epoxy resin mixture, and water to obtain the polyurea-based modified high-thixotropy waterborne epoxy curing agent.

[0012] As a further scheme of the present application, in step 1), the small molecule aldehyde is at least one of propyl aldehyde, pentyl aldehyde, and isobutyl aldehyde.

[0013] As a further scheme of the present application, in step 1), the molar ratio of the small molecule aldehyde to diethylenetriamine is 2.8-4.0:1.0; and the reaction temperature in step 1) is 80-120℃, and the reaction time is 6-12h.

[0014] As a further scheme of the present application, in step 1), the specific operation is: mixing and reacting the small molecule aldehyde and diethylenetriamine, timely removing water generated in the reaction, and then performing vacuumizing operation (removing excess small molecule aldehyde) under the conditions of a temperature of 100-120℃ and a vacuum degree of -0.1MPa to -0.06MPa for 1-3h to obtain the aldehyde imine-terminated modified amine.

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

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

[0017] As a further scheme of the present application, the molar ratio of the aldimine-terminated modified amine to the isocyanate in the polyfunctional 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 scheme of the present application, the molar ratio of the aldimine-terminated modified amine to the amino-methoxy-terminated 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 2-4h.

[0019] As a further scheme of the present application, in step 3), the epoxy resin mixture is composed of a mixture of a di-functional epoxy resin and a mono-functional glycidyl ether.

[0020] As a further scheme of the present application, the di-functional epoxy resin in the epoxy resin mixture in step 3) is at least one of E54, E51 and E44; the mono-functional glycidyl ether in the epoxy resin mixture in step 3) is at least one of C1-C 14 at least one of an alkyl glycidyl ether, a phenyl glycidyl ether, a benzyl glycidyl ether and an o-tolyl glycidyl ether.

[0021] As a further scheme of the present application, the mass ratio of the hydrophilically modified aldimine-terminated polyurea-based modified resin amine to water in step 3) is 0.59-0.75:1; the molar ratio of the hydrophilically modified aldimine-terminated polyurea-based modified resin amine to the di-functional epoxy and the mono-functional glycidyl ether in the epoxy resin mixture in step 3) is 1.0:0.2-0.4:0.5-1.0.

[0022] As a further scheme of the present application, the reaction temperature in step 3) is 60-90°C, and the reaction time is 2-4h.

[0023] In a second aspect, the present application further provides a polyurea-based modified high-thixotropy waterborne epoxy curing agent prepared by the above-mentioned method for preparing a polyurea-based modified high-thixotropy waterborne epoxy curing agent.

[0024] Compared with the prior art, the polyurea-based modified high-thixotropy waterborne epoxy curing agent and the preparation method thereof have the following beneficial effects: the aldimine structure is introduced in the synthesis process through structural design, the amino-methoxy-terminated polyether and the polyfunctional isocyanate are used for chain extension to obtain a supramolecular structure, and then an urea-based modified high-thixotropy waterborne epoxy curing agent is obtained through epoxy modification.

[0025] The present application introduces an aldimine structure in the synthesis process, which has a special structure of a closed primary amine and a residual secondary amine; the secondary amine group and the primary amine in the terminal aminomethoxy polyether are fully reacted with isocyanate in the multifunctional isocyanate to form a modified resin amine with a dendritic structure; then the aldimine structure in the modified resin amine is hydrolyzed with water to release the corresponding primary amine, which is reacted with an epoxy resin to obtain a polyurea-based modified high-thixotropy waterborne epoxy curing agent; the structure has the following characteristics: the hydrophilic group R has an anchoring effect to help the system quickly anchor to prevent sagging, the resin-like multiple amino ends can quickly establish a three-dimensional network structure to help prevent dust and sagging, and the epoxy modification group R1 can provide better compatibility with the waterborne epoxy resin to ensure excellent comprehensive performance.

[0026] The raw materials of the polyurea-based high-thixotropy waterborne epoxy curing agent of the present application are inexpensive and easy to obtain, the preparation cost is low, the process is simple, and it is suitable for large-scale industrial production.

[0027] These aspects or other aspects of the present application will be more apparent in the following description of the embodiments. It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the present application. DETAILED DESCRIPTION

[0028] In the following, the present application will be further described in conjunction with specific embodiments, and it should be noted that the embodiments described below or the technical features thereof can be combined in any manner to form new embodiments without conflict.

[0029] Embodiment 1

[0030] The present embodiment provides a polyurea-based modified high-thixotropy waterborne epoxy curing agent, and a preparation method thereof includes the following steps:

[0031] Propionaldehyde and diethylenetriamine are mixed according to a molar ratio of 2.8:1.0, reacted at 80℃ for 6h, and the water produced in the reaction is removed in time during the reaction; then vacuum operation (to remove excess aldehyde) is performed at a temperature of 100℃ and a vacuum degree of-0.06MPa for 2h, to obtain modified amine A;

[0032] 2) To the modified amine A of step 1), 227.03g of polyether modified isocyanate (Wanhua Aquolin@161), 100g of M2070 terminal aminomethoxy polyether amine and 130g of diethylene glycol dimethyl ether mixture (the molar ratio of modified amine A to isocyanate is 1.0:1.0; the amine hydrogen molar ratio of modified amine A to terminal aminomethoxy polyether is 1.0:0.1; the mass ratio of modified amine A to diethylene glycol dimethyl ether is 1.0:0.3) are added dropwise, and reacted at 40℃ for 2h to obtain modified amine B;

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

[0034] Example 2

[0035] The present embodiment provides a polyurea-modified high-threshold waterborne epoxy curing agent, and a preparation method thereof includes the following steps:

[0036] 1) mixing isobutyraldehyde and diethylenetriamine according to a molar ratio of 3.95:1, reacting for 6 h at 100°C, timely removing water generated during the reaction, and then performing vacuumizing operation (to remove excess aldehyde) for 1 h at a temperature of 110°C and a vacuum degree of -0.07 MPa to obtain isobutyraldehyde-modified diethylenetriamine, i.e., modified amine A;

[0037] 2) adding 225.37 g of sulfonic acid-modified isocyanate (Wanhua Aquolin®268), 25 g of amino-terminated methoxy polyether M1000, and 180 g of dipropylene glycol dimethyl ether (molar ratio of modified amine, isocyanate is 1.0:1.1, amine hydrogen molar ratio of modified amine, amino-terminated methoxy polyether is 1:0.05; mass ratio of modified amine A and dipropylene glycol dimethyl ether is 1.0:0.4) dropwisely into the modified amine A, and reacting for 3 h at 35°C to obtain modified fatty amine B;

[0038] 3) mixing urea-modified amine B, 68.18 g of E44 epoxy resin, 950 g of water, 44.25 g of phenyl glycidyl ether, and 66.67 g of C 12 -C 14 alkyl glycidyl ether (molar ratio of modified amine B, epoxy resin E51, phenyl glycidyl ether, C 12 -C 14 alkyl glycidyl ether is 1.0:0.3:0.25:0.25; mass ratio of modified amine B and water is 0.59:1), reacting for 3 h at 70°C to obtain a polyurea-modified high-threshold waterborne epoxy curing agent.

[0039] Example 3

[0040] The present embodiment provides a polyurea-modified high-threshold waterborne epoxy curing agent, and a preparation method thereof includes the following steps:

[0041] 1) pentanal and diethylene triamine were mixed according to a molar ratio of 4.0:1, reacted at 85℃ for 12h, and the water produced in the reaction was removed in time, and then vacuum operation (to remove excess aldehyde) was carried out at a temperature of 120℃ and a vacuum degree of-0.09MPa for 3h to obtain modified amine A;

[0042] 2) 231.19g of HDI trimer (Wanhua HT-100), 150g of amino-terminated methoxy polyether M3085, and 159.74g of dipropylene glycol dimethyl ether were added dropwise to the modified amine A of step 1) (the molar ratio of modified amine to isocyanate was 1.0:1.1, the amine hydrogen molar ratio of modified amine to amino-terminated methoxy polyether was 1:0.1; the mass ratio of modified amine A to dipropylene glycol dimethyl ether was 1.0:0.5), and reacted at 30℃ for 4h to obtain urea-modified amine B;

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

[0044] Comparative Example 1

[0045] A waterborne epoxy curing agent GZ20 (not containing a polyurea-modified waterborne epoxy curing agent) produced by Guangdong Huaguoshan Environmental Technology Co., Ltd. was used.

[0046] Performance test:

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

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

[0049]

[0050]

[0051] Notes:

[0052] Solid content: tested according to “GB 1725-1979 Determination of solid content of paints”;

[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: viscosity ratio of different rotation speeds of the same rotor of a rotary viscometer: 3#6r: 3#60r;

[0056] Preparation of paint film: the epoxy emulsion EP101 of Guangdong Huaguoshan Environmental Protection Technology Co., Ltd. and the waterborne epoxy curing agent of examples 1-3 and comparative example 1 were mixed uniformly according to the ratio of epoxy value to active hydrogen equivalent of 1:0.8, then sprayed on an A4 tinplate, leveled for 30 min, and then baked in a 50℃ oven for 1h, and the film thickness was measured.

[0057] As shown in table 1, the Ti value of the polyurea-based modified high-thixotropy waterborne epoxy curing agent of the present application and the Ti value after mixing with the waterborne epoxy emulsion and the corresponding anti-sagging film thickness are all significantly higher than those of the competitive product, indicating that the polyurea-based modified high-thixotropy waterborne epoxy curing agent of the present application has high thixotropy in the aspect of structural design.

[0058] The above examples are the preferred embodiments of the present application, but the embodiments of the present application are not limited by the above examples, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application are equivalent replacement methods and are included in the protection scope of the present application.

Claims

1. A method for preparing a polyurea-based modified high-thixotropy waterborne epoxy curing agent, characterized by, The method comprises the following steps: 1) mixing and reacting a small molecule aldehyde and diethylene triamine to obtain an aldehyde imine capped modified amine; 2) reacting the aldehyde imine capped modified amine, a solvent diluted multi-functional isocyanate and an amino methoxy polyether to obtain a hydrophilic modified aldehyde imine capped polyurea based modified resin amine; 3) mixing and reacting the hydrophilic modified aldehyde imine capped polyurea based modified resin amine, an epoxy resin mixture and water to obtain the polyurea based modified high thixotropy waterborne epoxy curing agent.

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 propyl aldehyde, pentyl aldehyde and isobutyl aldehyde.

3. The preparation method of the polyurea-modified high-thixotropic waterborne epoxy curing agent as described in claim 2, characterized in that, In step 1), the molar ratio of the small molecule aldehyde and diethylene triamine is 2.8-4.0:1.0; the reaction temperature is 80-120 DEG C, and the reaction time is 6-12 hours; and the specific operation of step 1) is as follows: mixing and reacting the small molecule aldehyde and diethylene triamine, timely removing water generated in the reaction, and then performing vacuumizing operation under the conditions of temperature of 100-120 DEG C and vacuum degree of-0.1-0.06 MPa for 1-3 hours to obtain the aldehyde imine capped 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 multi-functional isocyanate is at least one of polyether modified isocyanate (Wanhua Aquolin@161), sulfonic acid modified isocyanate (Wanhua Aquolin@268) and HDI trimer (Wanhua HT-100) with isocyanate functionality of not less than 3.

5. 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 solvent is at least one of diethylene glycol dimethyl ether and dipropylene glycol dimethyl ether; and the amino methoxy polyether 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 5, characterized in that, In step 2), the molar ratio of the aldehyde imine capped modified amine and isocyanate in the multi-functional isocyanate is 1.0:1.05-1.1; and the mass ratio of the solvent in the solvent diluted multi-functional isocyanate and the multi-functional isocyanate is 0.57-0.8:1.

0.

7. The preparation method of the polyurea-modified high-thixotropic waterborne epoxy curing agent as described in claim 6, characterized in that, In step 2), the molar ratio of the aldehyde imine capped modified amine and the amino methoxy polyether is 1.0:0.05-0.1; the reaction temperature is 0-40 DEG C, and the reaction time is 2-4 hours.

8. 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 epoxy resin mixture consists of a mixture of a bifunctional epoxy resin and a monofunctional glycidyl ether; in step 3), the bifunctional epoxy resin in the epoxy resin mixture is at least one of E54, E51, E44; in step 3), the monofunctional glycidyl ether in the epoxy resin mixture is C1-C 14 at least one of an alkyl glycidyl ether, a phenyl glycidyl ether, a benzyl glycidyl ether, an o-tolyl glycidyl ether.

9. The preparation method of the polyurea-modified high-thixotropic waterborne epoxy curing agent as described in claim 8, characterized in that, In step 3), the mass ratio of the hydrophilic modified aldehyde imine capped polyurea based modified resin amine and water is 0.59-0.75:1; the molar ratio of the hydrophilic modified aldehyde imine capped polyurea based modified resin amine and the double functional epoxy and the mono-functional glycidyl ether in the epoxy resin mixture is 1.0:0.2-0.4:0.5-1.0; and the reaction temperature is 60-90 DEG C, and the reaction time is 2-4 hours.

10. A polyurea-based modified hyperhypo waterborne epoxy curing agent, characterized by, The polyurea based modified high thixotropy waterborne epoxy curing agent is prepared by the method of any one of claims 1-9.

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