Preparation method of waterborne two-component zinc-rich special epoxy self-emulsifying resin

Abstract

The invention particularly discloses a preparation method of waterborne two-component zinc-rich special epoxy self-emulsifying resin. The preparation method comprises the following steps: 1) preparing a prepolymer; 2) preparing self-emulsifying epoxy resin; through the steps, the water-based double-component epoxy self-emulsifying resin special for zinc enrichment is prepared and has good wetting and wrapping effects on zinc powder, the problem that water-based epoxy resin for zinc enrichment still needs to be developed in the prior art is solved, and the water-based epoxy self-emulsifying resin specially designed for zinc enrichment products can be provided.

Description

Technical Field

[0001] The present invention relates to the technical field of coatings, and particularly to a preparation method of a waterborne two-component zinc-rich special epoxy self-emulsifying resin. Background Art

[0002] With the increasingly strict environmental protection regulations, especially the control of volatile organic compound (VOC) emissions, waterborne coatings have developed rapidly due to their advantage of significantly reducing or even completely eliminating the emissions of organic solvents. This environmentally friendly coating not only helps to protect the environment but also ensures the safety of use. Among waterborne coatings, the selection of resin is particularly crucial as it directly affects the performance of the final product. Currently, various types of resin products are available on the market, including but not limited to waterborne alkyd resins, waterborne epoxy resins, waterborne acrylic resins, waterborne polyurethane resins, waterborne polyester resins, and waterborne hybrid dispersions, etc.

[0003] Among these, waterborne epoxy resins are favored due to their unique properties. Epoxy resins themselves have been widely used in the fields of coatings, adhesives, and composite materials due to their excellent adhesion, thermal stability, chemical corrosion resistance, insulation, and mechanical strength. However, traditional solvent-based epoxy resin coatings pose potential risks to the environment and human health due to the presence of a large amount of organic solvents. In contrast, waterborne epoxy resins have gradually become the new favorite in the market due to their environmental protection characteristics and good physical and chemical properties.

[0004] The methods for preparing waterborne epoxy resins are mainly divided into two categories: the external emulsifier method and the self-emulsification method. The former realizes the emulsification of epoxy resins by adding surfactants, but has problems such as large particle size, poor storage stability, and water resistance. The latter introduces hydrophilic groups into the molecular structure of epoxy resins through chemical modification, enabling them to disperse in water by themselves, thereby improving the stability of the emulsion and the comprehensive performance of the coating film. Specifically, the self-emulsification method is further divided into the salt-forming method and the non-ionic modification method. Among them, the non-ionic modification method improves the hydrophilicity of epoxy resins by introducing polyoxyethylene segments, avoiding the use of external emulsifiers. The prepared emulsion has better stability and smaller particle size, and is particularly suitable for practical applications.

[0005] For specific application scenarios such as zinc-rich anti-corrosion coatings, it is still necessary to further develop waterborne epoxy resins with specialized formulations. Such resins need to have good stability and encapsulation ability for zinc-rich powders, as well as complexing ability with substrates to meet the high requirements in the field of heavy anti-corrosion; for example, Patent CN101260183 proposes a water-based organic zinc-rich paint composition, in which the epoxy resin as the main reagent is a common bisphenol-type epoxy resin, which has poor hydrophilicity and cannot wet and encapsulate zinc powder. In the above disclosed technical solutions, there is still room for development, especially the development of epoxy resins specifically for waterborne zinc-rich. This resin needs to have stability, encapsulation ability for zinc-rich and complexing ability with substrates to perfectly achieve the purpose of replacing oil-based products. Summary of the Invention The object of the present invention is to address the deficiencies of the prior art and provide a waterborne epoxy self-emulsifying resin structure specifically designed for zinc-rich products, aiming to solve the problem of poor wetting and encapsulation effects of existing products on zinc powder.

[0006] To achieve the above object of the invention, the technical solution provided by the present invention is as follows: A preparation method of a waterborne two-component zinc-rich special epoxy self-emulsifying resin, characterized by comprising the following steps carried out in sequence: 1) Preparation of prepolymer: 1-1) Mix 5-25 parts of epoxy resin and 40-70 parts of polyether alcohol evenly to obtain mixture I; 1-2) Under nitrogen protection, heat mixture I to a preset temperature I, keep it warm until the turbidity detection value of mixture I ≤ 10 NTU, then add 0.05-0.15 parts of catalyst I, and react for a preset time I at a preset temperature II to generate the prepolymer, and cool down and add 5-20 parts of cosolvent I for dilution; 2) Preparation of self-emulsifying epoxy resin: 2-1) Mix 5-25 parts of the prepolymer, 40-80 parts of epoxy resin, 3-30 parts of bisphenol A, 0.5-5 parts of organic carboxylic acid, and 5-30 parts of cosolvent I evenly to form mixture II, and fill it with nitrogen for protection; 2-2) Add 0.05-0.15 parts of catalyst II to mixture II and react for a preset time II at a preset temperature III; 2-3) Add 0.05-0.15 parts of catalyst III, dropwise add 1-30 parts of polyisocyanate and continue to react for a preset time III, then remove cosolvent I; 2-4) Add cosolvent II to reach the set solid content value to obtain the self-emulsifying epoxy resin; In step 1-1), the epoxy resin molecular structure contains at least two epoxy groups; The catalyst I is potassium persulfate, boron trifluoride ether complex or boron trifluoride amine complex; The catalyst II is a quaternary ammonium salt, a quaternary phosphonium salt or a derivative thereof; The catalyst III is an organotin salt or an organobismuth salt; The cosolvent I is independently selected from one or more of acetone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, butyl acetate, benzene or xylene; The cosolvent II is independently selected from one or more of benzyl alcohol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether.

[0007] Furthermore, the epoxy resin is one or more of bisphenol A epoxy, bisphenol F epoxy, phenolic epoxy, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether; the polyether alcohol is polyethylene glycol ether.

[0008] Furthermore, the set solid content in step 2-4) is 40% - 50%.

[0009] Furthermore, the organic carboxylic acid in step 2-1) is a branched-chain monocarboxylic acid.

[0010] Furthermore, the branched-chain monocarboxylic acid in step 2-1) is isooctanoic acid.

[0011] Furthermore, the polyisocyanate is independently selected from one or more of toluene diisocyanate, xylene diisocyanate, hexamethylene diisocyanate, benzidine diisocyanate, isophorone diisocyanate, trimethylhexamethylene diisocyanate, hydrogenated toluene diisocyanate.

[0012] Furthermore, the organic carboxylic acid in step 2-1) is isooctanoic acid.

[0013] Furthermore, the preset temperature I in step 1-2) is 70 - 90 °C, the preset temperature II is 90 - 120 °C, and the preset time I is 3 - 5 hours.

[0014] Furthermore, the preset temperature III in step 2-1) is 120 - 180 °C, the reaction preset time II is 3 - 5 hours, and the reaction preset time III is 2 - 3 hours.

[0015] Furthermore, the waterborne two-component zinc-rich special epoxy self-emulsifying resin is prepared by the preparation method of the waterborne two-component zinc-rich special epoxy self-emulsifying resin as described in any one of claims 1-9.

[0016] Compared with the prior art, the preparation method of the waterborne two-component zinc-rich special epoxy self-emulsifying resin provided by the present invention can achieve small self-emulsification particle size, and at the same time has a wetting and wrapping effect on zinc powder, with stronger anti-corrosion ability and a broader application prospect. The specific beneficial effects are as follows: 1. During the preparation process, an organic carboxylic acid, especially isooctanoic acid, is added, introducing an ester bond into the molecular structure of the self-emulsifying epoxy resin, which can significantly optimize the interfacial interaction between the resin and zinc powder. The introduction of the ester bond effectively improves the wetting performance of the resin on zinc powder by reducing the interfacial tension, enabling the zinc powder particles to be more uniformly wetted and dispersed during the preparation of the zinc-rich epoxy resin coating, preventing abnormal phenomena such as zinc powder agglomeration and inability to disperse.

[0017] 2. A polyethylene glycol ether grafting structure is introduced into the molecular structure of the self-emulsifying epoxy resin to reduce the polarity of the resin, making it closer to the surface of zinc powder (the surface of zinc powder usually has a certain polarity due to zinc oxide but is overall hydrophobic). The hydrophobic chain of the long-chain alkane binds to the surface of zinc powder through van der Waals forces, achieving stable encapsulation of zinc powder during the preparation of the zinc-rich epoxy resin coating.

[0018] 3. Polyisocyanate is introduced into the molecular structure of the self-emulsifying epoxy resin to form a cross-linked network, significantly increasing the molecular weight and glass transition temperature of the resin. This modification not only enhances the mechanical properties and heat resistance of the resin but also significantly improves the adhesion and anti-corrosion ability of the prepared zinc-rich epoxy resin coating to the substrate.

[0019] 4. The self-emulsifying epoxy resin prepared by the present invention is particularly suitable for protection in the field of heavy anti-corrosion, such as ports, oil tanks, offshore oil platforms, etc. Specific Embodiments

[0020] The following combines examples to clearly and completely describe the technical solutions of the present invention. Obviously, the described examples are only a part of the examples of the present invention, rather than all of them. Based on the examples in the present invention, all other examples obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present invention. The following reagents or raw materials, unless otherwise specified, are all from publicly available commercial channels.

[0021] The present invention specifically discloses a preparation method of a waterborne two-component zinc-rich special epoxy self-emulsifying resin, including the following steps carried out in sequence: 1) preparing a prepolymer, 2) preparing a self-emulsifying epoxy resin. The two-step preparation process endows it with good comprehensive properties.

[0022] In the disclosed examples of the present invention, according to the characteristics of the self-emulsifying waterborne epoxy resin and the requirements of its application scenarios, one or more of low-molecular-weight epoxy resins such as bisphenol A epoxy, bisphenol F epoxy, phenolic epoxy, polyethylene glycol glycidyl ether, and polypropylene glycol glycidyl ether are selected.

[0023] The present invention specifically discloses a preparation method of a waterborne two-component zinc-rich special epoxy self-emulsifying resin; The following further illustrates the present invention through specific examples.

[0024] Example 1 This example specifically discloses a preparation method of a waterborne two-component zinc-rich special epoxy self-emulsifying resin. The specific steps are as follows: 1) Preparation of prepolymer: 1-1) Mix 11 g of epoxy resin 128 (Nanya) and 60 g of PEG4000 evenly to obtain mixture I; 1-2) Flush with nitrogen and heat mixture I to 80 °C. After keeping warm until mixture I becomes transparent, use a turbidimeter to test the turbidity detection value ≤ 10 NTU. Add 0.1 g of boron trifluoride ethyl ether. At 110 °C, react for 2 hours to generate a prepolymer. Cool down and add 10 g of methyl isobutyl ketone for dilution to obtain the prepolymer. The molecular weight distribution of the prepolymer is controlled to be Mw / Mn ≤ 1.2; 2) Preparation of self-emulsifying epoxy resin; 2-1) Mix 10 g of prepolymer, 20 g of bisphenol A, 54 g of epoxy resin 128 (Nanya), 3 g of isooctanoic acid, and 20 g of methyl isobutyl ketone evenly to form mixture II, and flush with nitrogen for protection; 2-2) Add 0.1 g of triphenylphosphine to mixture II and react at 160 °C for 3 hours; 2-3) Add 0.1 g of dibutyltin dilaurate, dropwise add 15 g of toluene diisocyanate and continue to react for 2 hours, then remove methyl isobutyl ketone; 2-4) Add propylene glycol methyl ether until the solid content is in the range of 40% - 50% to obtain the self-emulsifying epoxy resin.

[0025] Examples 2 - 6 The preparation methods of the waterborne acrylic emulsions disclosed in Examples 2 - 6 are the same as the steps disclosed in Example 1, except for the selection and quality (unit: g) of raw materials, as shown in Table 1 specifically; and process conditions, as shown in Table 2 specifically.

[0026] Table 1 Raw material ratio table of Examples 1 - 6 and Comparative Example 1 Table 2 Process condition table of Examples 1 - 6 and Comparative Example 1 Preparation of waterborne two-component self-emulsifying epoxy zinc-rich coating and performance testing Select the self-emulsifying epoxy resin of Zhejiang Anbang (product model AB-RP-20) as Comparative Example 2. Use the examples and comparative examples as raw materials to prepare waterborne two-component self-emulsifying epoxy zinc-rich coatings respectively. The specific material formulas are shown in Table 3 and Table 4 (mass unit: g); the performance parameter comparison is shown in Table 5.

[0027] Table 3 Composition table of component A of waterborne two-component self-emulsifying epoxy zinc-rich coating Table 4 Composition table of component B of waterborne two-component self-emulsifying epoxy zinc-rich coating.

[0028] Prepare waterborne two-component self-emulsifying epoxy zinc-rich coating with the ratio of component A: component B being 10:1, and conduct performance tests. The test results are as follows in the table: Table 5 Comparison table of performance parameters of waterborne two-component self-emulsifying epoxy zinc-rich coating Note: Appearance of the coating film: Test according to the test method in GB / T 9755-2014; Flexibility test: Test according to the test method in GB1731-1993; Impact resistance test: Test according to the test method in GB1732-1993; Adhesion (cross-cut method) test: Test according to the test method in GB / 1720-79(89); Water resistance test: Test according to the test method in GB / T1733-1993; Neutral salt spray resistance test: Test according to the test method in GB / T1771-2007; Drying time: Test according to the test method in GB / T 1728-2020.

[0029] It can be seen from the above table that the impact strength, flexibility, adhesion, and neutral salt spray resistance of the example specimens are better than those of the comparative examples. In particular, the adhesion has been greatly improved, and the good wetting and encapsulation of zinc powder by waterborne self-emulsifying epoxy resin are the key to enhancing the coating adhesion performance.

[0030] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the broadest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a water-based two-component zinc-rich special epoxy self-emulsifying resin, characterized in that: The steps are as follows: 1) Preparation of prepolymer: 1-1) 5-25 parts of epoxy resin and 40-70 parts of polyether alcohol are mixed uniformly to obtain a mixed solution I; 1-2) heating the mixed solution I to a preset temperature I under nitrogen protection, keeping the temperature until the turbidity detection value of the mixed solution I is ≤10NTU, adding 0.05-0.15 parts of catalyst I, reacting at a preset temperature II for a preset time I to generate the prepolymer, cooling and adding 5-20 parts of co-solvent I to dilute; 2) Preparation of self-emulsifying epoxy resin: 2-1) 5-25 parts of the prepolymer, 40-80 parts of epoxy resin, 3-30 parts of bisphenol A, 0.5-5 parts of organic carboxylic acid, and 5-30 parts of the cosolvent I are uniformly mixed to form a mixed solution II, and nitrogen is charged for protection; 2-2) adding 0.05-0.15 parts of catalyst II to the mixed solution II, and reacting at a preset temperature III for a preset time II; 2-3) Add 0.05-0.15 parts of catalyst III, dropwise add 1-30 parts of polyisocyanate and continue to react for a preset time III, then remove the cosolvent I; 2-4) adding co-solvent II to a set solid content value to obtain the self-emulsifying epoxy resin; The epoxy resin molecular structure in step 1-1) contains at least two epoxy groups; The catalyst I is potassium persulfate, boron trifluoride ether complex or boron trifluoride amine complex; The catalyst II is a quaternary ammonium salt, a quaternary phosphonium salt or a derivative thereof; The catalyst III is an organic tin salt or an organic bismuth salt; The cosolvents I are each independently selected from one or more of acetone, butanone, methyl isobutyl ketone, ethyl acetate, butyl acetate, benzene or xylene; The co-solvents II are independently selected from one or more of benzyl alcohol, ethylene glycol ethyl ether, ethylene glycol butyl ether, propylene glycol methyl ether, propylene glycol ethyl ether, and propylene glycol butyl ether.

2. The preparation method according to claim 1, characterized in that: The epoxy resin is one or more of bisphenol A epoxy, bisphenol F epoxy, novolac epoxy, polyethylene glycol glycidyl ether, and polypropylene glycol glycidyl ether; and the polyether alcohol is polyethylene glycol ether.

3. The preparation method according to claim 2, characterized in that: The solid content value set in step 2-4) is 40%~50%.

4. The preparation method according to claim 3, characterized in that: The organic carboxylic acid in step 2-1) is a branched monocarboxylic acid.

5. The preparation method according to claim 4, characterized in that: In step 2-1), the branched monocarboxylic acid is isooctanoic acid.

6. The preparation method according to claim 5, characterized in that: The polyisocyanates are each independently selected from one or more of toluene diisocyanate, xylene diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, isophorone diisocyanate, trimethylhexamethylene diisocyanate, and hydrogenated toluene diisocyanate.

7. The preparation method according to claim 6, characterized in that: The catalyst III is one or more of dibutyltin dilaurate, stannous octoate, bismuth isooctanoate, bismuth laurate, and bismuth neodecanoate.

8. The preparation method according to claim 7, characterized in that: In step 1-2), the preset temperature I is 70-90° C., the preset temperature II is 90-120° C., and the preset time I is 3-5 hours.

9. The preparation method according to claim 8, characterized in that: In step 2-1), the preset temperature III is 120-180° C., the preset reaction time II is 3-5 hours, and the preset reaction time III is 2-3 hours.

10. A water-based two-component zinc-rich special epoxy self-emulsifying resin, characterized in that: The water-based two-component zinc-rich special epoxy self-emulsifying resin is prepared using the water-based two-component zinc-rich special epoxy self-emulsifying resin preparation method as described in any one of claims 1-9.

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