Rapidly-curable water-based acrylic modified epoxy resin emulsion for coating multiple substrates and preparation method of rapidly-curable water-based acrylic modified epoxy resin emulsion

Abstract

The preparation method comprises the following steps: firstly, synthesizing an epoxy adduct intermediate product from itaconic acid, an alcohol ether solvent and bisphenol A type epoxy resin; carrying out free radical polymerization on the intermediate product and other acrylic acid monomers to form acrylic acid modified epoxy resin; and finally, preparing the water-based acrylic acid modified epoxy resin emulsion by adopting an external epoxy emulsifier through a phase inversion method. The emulsion prepared by the invention has higher glass-transition temperature and higher surface drying and curing speed, and can meet the requirements on quick curing of a coating film on various base material workpieces and stacking resistance of the workpieces in the off-line process; a side chain contains a certain amount of carboxyl and hydroxyl, so that a coating film can be endowed with excellent adhesive force, and good adhesion on various base materials is realized; the resin structure contains a certain amount of bisphenol A epoxy resin, and has good compatibility and uniform coating film after being cured with an epoxy-amine curing agent.

Description

Technical Field

[0001] The invention belongs to the technical field of coatings, and in particular relates to a water-based acrylic acid-modified epoxy resin emulsion capable of being quickly cured and used for coating multiple substrates, and a preparation method thereof. Background Art

[0002] Two-component waterborne epoxy-amine curing system coatings are widely used in industrial protection, floor coating and other fields. In recent years, on the one hand, modern industrial products are often assembled from several parts with different substrate properties. Applying the same coating on the workpiece requires the coating film to have universal adhesion to parts with multiple substrates; on the other hand, with the improvement of industrial efficiency, under the premise of ensuring the performance of the coating film, accelerating the surface drying and curing speed of the coating film and shortening the turnover time of the coated workpiece have become key factors for coating companies to consider.

[0003] It is known that there are many technical methods for improving the surface drying and curing speed of two-component waterborne epoxy coatings, such as improving the activity of epoxy-amine curing agents. The common method is to increase the content of primary amine hydrogen substances; or use raw materials containing phenolic amines and aromatic amines; or increase the curing speed by adding catalysts; there are also some documents that use larger molecular weight epoxy resins to prepare emulsions to accelerate the surface drying speed of the coating, but the actual anti-corrosion effect at low temperatures needs to be improved; Patent CN114686069A improves the drying property by adding high Tg polyacrylate resins, but the acrylate and epoxy resin do not undergo a chemical grafting reaction, and the coating has problems such as poor compatibility and easy migration.

[0004] There are few technical solutions for the adhesion of fast-drying or fast-curing two-component waterborne epoxy coating systems on multiple substrates. Fast-drying or fast-curing coatings usually have high internal stress and poor adhesion on aluminum alloy substrates, galvanized substrates, workpiece finishes, and electrophoretic primers, which is a key technical difficulty that needs to be considered in industrial coating construction. Summary of the invention

[0005] The present invention is proposed to solve the problems existing in the prior art, and its purpose is to provide a water-based acrylic acid modified epoxy resin emulsion which can be quickly cured and is used for coating multiple substrates, and a preparation method thereof.

[0006] The present invention is achieved through the following technical solutions:

[0007] A water-based acrylic acid-modified epoxy resin emulsion for coating multiple substrates and capable of rapid curing, wherein the water-based acrylic acid-modified epoxy resin emulsion comprises the following components and the mass fractions of each component:

[0008]

[0009]

[0010] In the above technical solution, the epoxy emulsifier is a polyethylene oxide-epoxy resin polymer.

[0011] In the above technical solution, the bisphenol A type epoxy resin is any one or more of E-51, E-44 or E-20.

[0012] In the above technical solution, the functional group-containing acrylic monomer is any one or more of acrylic acid, methacrylic acid, hydroxypropyl acrylate or hydroxyethyl methacrylate; acrylic acid and methacrylic acid are carboxyl functional group-containing acrylic monomers, and hydroxypropyl acrylate and hydroxyethyl methacrylate are hydroxyl functional group-containing acrylic monomers.

[0013] In the above technical solution, the other alkyl acrylate monomers are any one or more of methyl methacrylate, butyl acrylate, butyl methacrylate, isooctyl acrylate, isooctyl methacrylate or styrene.

[0014] In the above technical solution, the initiator is azobisisobutyronitrile.

[0015] In the above technical solution, the alcohol ether solvent is any one or more of propylene glycol methyl ether, propylene glycol butyl ether or dipropylene glycol butyl ether.

[0016] In the above technical scheme, the epoxy equivalent of the water-based acrylic modified epoxy resin emulsion is 600-660 in terms of non-volatile matter, and the non-volatile matter is 50%-56%; the water-based acrylic modified epoxy resin emulsion is used in a two-component water-based epoxy-amine curing system; the water-based acrylic modified epoxy resin emulsion is made water-based by a phase inversion method using an external emulsifier.

[0017] A method for preparing a water-based acrylic acid-modified epoxy resin emulsion that can be quickly cured for coating multiple substrates comprises the following steps:

[0018] (I) Synthesis of epoxy adduct intermediates

[0019] Add itaconic acid and ethanol in an amount equal to that of itaconic acid in a reaction container, then add part of an alcohol ether solvent so that the azeotropic point of the mixed solution reaches 100° C. to 120° C., mix well and heat to 100° C. to 120° C., add bisphenol A epoxy resin after melting, heat to 120° C. to 130° C., keep warm for 2 hours, test the acid value every hour, stop the reaction when the acid value is ≤5 mgKOH / g, and obtain an epoxy addition intermediate product;

[0020] (II) Synthesis of acrylic acid modified epoxy resin

[0021] The temperature is controlled at 100° C. to 110° C., a functional group-containing acrylic monomer, other alkyl acrylate monomers and a first batch of initiators are uniformly mixed in advance, placed in a dropping funnel, and a mixture of the functional group-containing acrylic monomer, other alkyl acrylate monomers and initiators is dripped into the epoxy adduct intermediate product for 2 h to 4 h, and the mixture is kept warm for 2 h; then the remaining initiator and the remaining alcohol ether solvent mixture are dripped for 1 h to 2 h, and finally the mixture is kept warm for 2 h to 3 h to terminate the reaction, thereby obtaining an acrylic modified epoxy resin; the first batch of initiators accounts for 80% of the total mass of the initiators;

[0022] (III) Preparation of waterborne acrylic modified epoxy resin emulsion

[0023] Add epoxy emulsifier and acrylic modified epoxy resin into a reaction container, heat to 80°C to 90°C to melt; slowly add deionized water into the reaction container under high-speed stirring until phase inversion is completed to prepare a water-based acrylic modified epoxy resin emulsion.

[0024] The beneficial effects of the present invention are:

[0025] The invention provides a water-based acrylic modified epoxy resin emulsion which can quickly dry and cure on multiple substrates and has good adhesion on multiple substrates, and a preparation method thereof. First, an epoxy adduct intermediate product is prepared, and the intermediate product is subjected to free radical polymerization with other acrylic monomers to form an acrylic modified epoxy resin, and finally an external epoxy emulsifier is used to prepare the water-based acrylic modified epoxy resin emulsion through a phase inversion method. The prepared emulsion has a higher glass transition temperature, faster surface drying and curing speed, and can meet the requirements of rapid curing of coatings on various substrate workpieces and stacking resistance of workpieces off the line; the side chain contains a certain amount of carboxyl and hydroxyl groups, which can give the coating excellent adhesion and achieve good adhesion on various substrates; the resin structure contains a certain amount of bisphenol A epoxy resin, which has good compatibility with an epoxy-amine curing agent after curing, and the coating is uniform. DETAILED DESCRIPTION

[0026] In order to enable persons skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is further described below through specific implementation methods.

[0027] The main raw materials involved in the examples and comparative examples of the present invention are shown in Table 1 below:

[0028] Table 1

[0029]

[0030]

[0031] Example 1

[0032] A method for preparing a water-based acrylic acid-modified epoxy resin emulsion that can be quickly cured for coating multiple substrates comprises the following steps:

[0033] (I) Synthesis of epoxy adduct intermediates

[0034] Prepare the raw materials according to the formula of bisphenol A epoxy resin and itaconic acid. The specific formula is shown in Table 1-1.

[0035] Table 1-1

[0036]

[0037]

[0038] Add 26.0 parts by weight of itaconic acid, 26.0 parts by weight of ethanol and 38.0 parts by weight of propylene glycol butyl ether as shown in Table 1-1 into a reaction container, mix well, heat to 100°C, and after melting, add 233.0 parts by weight of epoxy resin E-51, heat to 120°C, keep warm at 120°C, and react for 2 hours. Test the acid value every 1 hour. When the acid value is ≤5 mgKOH / g, stop the reaction to obtain 323.0 parts by weight of epoxy adduct intermediate product.

[0039] (II) Synthesis of acrylic acid modified epoxy resin

[0040] Prepare the raw materials according to the formula of epoxy adduct intermediate product, functional group-containing acrylic monomer, other alkyl acrylate monomer, initiator, and alcohol ether solvent. The specific formula is shown in Table 1-2.

[0041] Table 1-2

[0042]

[0043] 323.0 parts by weight of the epoxy adduct intermediate product are added to a reaction container, and the reaction temperature is controlled at 105° C. The corresponding parts by weight of the functional group-containing acrylic monomer, other alkyl acrylate monomers and 7.2 parts by weight of the initiator are uniformly mixed in advance and placed in a dropping funnel, and the mixture of the functional group-containing acrylic monomer, other alkyl acrylate monomers and the initiator is dripped into the 323.0 parts by weight of the epoxy adduct intermediate product, and the dripping is completed over 4 hours, and the mixture is kept warm for 2 hours; the remaining 1.8 parts by weight of the initiator and the remaining 18.0 parts by weight of propylene glycol methyl ether are dripped for 1 hour, and finally the mixture is kept warm for 3 hours to terminate the reaction, thereby obtaining an acrylic modified epoxy resin.

[0044] (III) Preparation of acrylic modified epoxy resin emulsion

[0045] Prepare the raw materials according to the formula of epoxy emulsifier, acrylic modified epoxy resin and deionized water. The specific formula is shown in Table 1-3.

[0046] Table 1-3

[0047] Components Raw material name Dosage, weight parts Mass percentage, % Acrylic modified epoxy resin 376.0 54.31 Epoxy emulsifier CTW-6060 emulsifier 50.0 7.22 Deionized water 266.3 38.47 total 692.3 100.00

[0048] Add 376.0 parts by weight of acrylic modified epoxy resin and 50.0 parts by weight of epoxy emulsifier as shown in Table 1-3 into the reaction vessel, heat to 80°C, wait for the material to be fully melted, keep the speed at 2000 rpm, slowly and uniformly add 266.3 parts by weight of deionized water, keep adding for 2 hours, wait for the phase inversion to be completed smoothly, and obtain water-based acrylic modified epoxy resin emulsion. The obtained acrylic modified epoxy resin emulsion has a particle size of 400-600nm, an epoxy equivalent of 618, a non-volatile matter of about 52%, and a viscosity of 3458MPa*s.

[0049] Example 2

[0050] A method for preparing a water-based acrylic acid-modified epoxy resin emulsion that can be quickly cured for coating multiple substrates comprises the following steps:

[0051] (I) Synthesis of epoxy adduct intermediates

[0052] Prepare the raw materials according to the formula of bisphenol A epoxy resin and itaconic acid. The specific formula is shown in Table 2-1.

[0053] Table 2-1

[0054]

[0055] Add 26.0 parts by weight of itaconic acid, 26.0 parts by weight of ethanol and 32.0 parts by weight of propylene glycol butyl ether as shown in Table 1-1 into a reaction container, mix well, heat to 100°C, and after melting, add 222.0 parts by weight of epoxy resin E-51, heat to 120°C, keep warm at 120°C, and react for 2 hours. Test the acid value every 1 hour. When the acid value is ≤5 mgKOH / g, stop the reaction to obtain 306.0 parts by weight of epoxy adduct intermediate product.

[0056] (II) Synthesis of acrylic acid modified epoxy resin

[0057] Prepare the raw materials according to the formula of epoxy adduct intermediate product, functional group-containing acrylic monomer, other alkyl acrylate monomer, initiator, and alcohol ether solvent. The specific formula is shown in Table 2-2.

[0058] Table 2-2

[0059]

[0060] 306.0 parts by weight of the epoxy adduct intermediate product are added to a reaction container, and the reaction temperature is controlled at 105° C. The corresponding parts by weight of the functional group-containing acrylic monomer, other alkyl acrylate monomers and 6.8 parts by weight of the initiator are uniformly mixed in advance and placed in a dropping funnel, and the mixture of the functional group-containing acrylic monomer, other alkyl acrylate monomers and the initiator is dripped into the 306.0 parts by weight of the epoxy adduct intermediate product, and the dripping is completed over 4 hours, and the mixture is kept warm for 2 hours; the remaining 1.7 parts by weight of the initiator and the remaining 17.0 parts by weight of propylene glycol methyl ether are dripped for 1 hour, and finally the mixture is kept warm for 3 hours to terminate the reaction, thereby obtaining an acrylic modified epoxy resin.

[0061] (III) Preparation of acrylic modified epoxy resin emulsion

[0062] Prepare the raw materials according to the formula of epoxy emulsifier, acrylic modified epoxy resin and deionized water. The specific formula is shown in Table 2-3.

[0063] Table 2-3

[0064]

[0065]

[0066] Add 411.9 parts by weight of acrylic modified epoxy resin and 62.5 parts by weight of epoxy emulsifier as shown in Table 1-3 into the reaction vessel, heat to 90°C, wait for the material to be fully melted, keep the rotation speed at 2000rad / min, slowly and uniformly add 294.8 parts by weight of deionized water, keep adding for 2 hours, wait for the phase inversion to be completed smoothly, and obtain water-based acrylic modified epoxy resin emulsion. The obtained acrylic modified epoxy resin emulsion has a particle size of 400-600nm, an epoxy equivalent of 620, a non-volatile matter of about 52%, and a viscosity of 4580MPa*s.

[0067] Comparative Example 1

[0068] A method for preparing a water-based acrylic acid-modified epoxy resin emulsion comprises the following steps:

[0069] (I) Preparation of epoxy emulsion

[0070] Prepare the raw materials according to the formula of epoxy resin E-20, E-12, epoxy emulsifier, alcohol ether solvent and deionized water. The specific formula is shown in Table 3.

[0071] Table 3

[0072] Components Raw material name Dosage, weight Mass percentage, % Bisphenol A epoxy resin E-20 200.0 28.89 E-12 120.0 17.33 Epoxy emulsifier CTW-6060 emulsifier 50.0 7.22 Alcohol ether solvents Propylene glycol methyl ether 38.0 5.49 Deionized water 284.3 41.07 total 692.3 100.00

[0073] In a reaction vessel, 320.0 parts by weight of epoxy resins E-20 and E-12, 50.0 parts by weight of epoxy emulsifier, and 38.0 parts by weight of propylene glycol methyl ether, an alcohol ether solvent, were added, stirred and heated to 90°C. After the materials were fully melted, 284.3 parts by weight of deionized water were slowly and uniformly added dropwise at a speed of 2000 rad / min. The addition was continued for 2 hours. After the phase inversion was completed smoothly, an epoxy emulsion was obtained, whose epoxy equivalent was 628, the non-volatile matter was about 52%, and the viscosity was 3570 MPa*s.

[0074] The application performance of the acrylic acid modified epoxy resin emulsion of the present invention in waterborne epoxy coatings was monitored:

[0075] (I) Preparation of two-component waterborne epoxy coating

[0076] Two-component waterborne epoxy coatings were prepared using CTW-WSJ (R7035) waterborne mortar, the non-volatile content of which was 75.0±2.0%. CTW-3206 waterborne epoxy curing agent was used for paint preparation, the active hydrogen equivalent of which was 150 (as supplied).

[0077] The formula of two-component water-based epoxy coating is shown in Table 4-1.

[0078] Table 4-1

[0079]

[0080] (II) Paint matching process

[0081] CTW-WSJ (R7035) water-based mortar, modified acrylic epoxy resin emulsions prepared in Examples 1 and 2, epoxy resin emulsion prepared in Example 3, leveling agent and deionized water were mixed evenly according to the formula amounts in Table 4-1 to form two-component water-based epoxy coating main agents 1#, 2# and 3#, which were set aside;

[0082] Mix two-component waterborne epoxy coating main agents 1#, 2#, and 3# with corresponding weight portions of CTW-3206 waterborne epoxy curing agent respectively, add deionized water to adjust the viscosity to 25-35s per coating cup, filter, and spray with compressed air.

[0083] (III) Preparation of test samples

[0084] Test samples: tinplate, mirror stainless steel plate, galvanized plate, aluminum alloy plate, pure aluminum plate, electrophoretic primer plate, the above test samples are not polished, degreased and cleaned; cold rolled steel plate is degreased and S2.5 grade sandblasted. The sample is sprayed with the two-component waterborne epoxy coating prepared by Example 1, Example 2, and Example 3 (comparative example), and dried at room temperature for 7 days.

[0085] Among them, the dry film thickness of the coating on tinplate plate, mirror stainless steel plate, galvanized plate, aluminum alloy plate, pure aluminum plate, and electrophoretic primer plate is controlled at 30-50μm; the dry film thickness of the coating on cold-rolled steel plate is controlled at 60-80μm.

[0086] After the test plate is cured, the coating properties are tested. The coating adhesion of tinplate, mirror stainless steel plate, galvanized plate, aluminum alloy plate, pure aluminum plate and electrophoretic primer plate is tested according to the GB / T 9286-2021 cross-cut method. The cold-rolled steel plate is tested for the coating surface drying time, coating hardness after 24 hours of self-drying, and coating resistance to deionized water and neutral salt spray before and after 24 hours of self-drying. The coating adhesion is tested according to the GB / T5210-2006 pull-off method.

[0087] The coating performance of the above-mentioned sample plates was tested in accordance with relevant national standards for the coating industry, and the test results of 1# (Example 1), 2# (Example 2), and 3# (Comparative Example) were compared and listed in Table 4-2.

[0088] Table 4-2

[0089]

[0090] It can be concluded from Table 4-2 that by preparing the above-mentioned two-component water-based epoxy coating, the results of the application performance test of the water-based acrylic modified epoxy resin emulsion of the present invention show that the multi-substrate coating fast-curing acrylic modified epoxy resin emulsion prepared by the technical scheme of the present invention can ensure rapid curing of the coating while giving the coating excellent adhesion to a variety of substrates, and at the same time has good anti-corrosion performance.

[0091] The present invention provides an acrylic modified epoxy resin emulsion which can be quickly cured for coating multiple substrates. The epoxy resin and itaconic acid are chemically grafted to form an epoxy resin adduct intermediate product, which is then modified with acrylic acid to provide the coating with better adhesion, flexibility and other properties, thereby achieving a balance between excellent adhesion to multiple substrates, rapid curing and corrosion resistance of the coating after painting.

[0092] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A fast-curing aqueous acrylic modified epoxy resin emulsion for coating multiple substrates, characterized in that: The components included in the waterborne acrylic acid modified epoxy resin emulsion and the mass fractions of each component are as follows:

2. The aqueous acrylic modified epoxy resin emulsion for fast curing for coating multiple substrates according to claim 1, characterized in that: The epoxy emulsifier is a polyethylene oxide-epoxy resin polymer.

3. The water-based acrylic modified epoxy resin emulsion for fast curing for coating multiple substrates according to claim 1, characterized in that: The bisphenol A type epoxy resin is any one or more of E-51, E-44 or E-20.

4. The water-based acrylic modified epoxy resin emulsion for fast curing for coating multiple substrates according to claim 1, characterized in that: The functional group-containing acrylic monomer is any one or more of acrylic acid, methacrylic acid, hydroxypropyl acrylate or hydroxyethyl methacrylate.

5. The water-based acrylic modified epoxy resin emulsion for fast curing for coating multiple substrates according to claim 1, characterized in that: The other alkyl acrylate monomers are any one or more of methyl methacrylate, butyl acrylate, butyl methacrylate, isooctyl acrylate, isooctyl methacrylate or styrene.

6. The water-based acrylic modified epoxy resin emulsion for fast curing for coating multiple substrates according to claim 1, characterized in that: The initiator is azobisisobutyronitrile.

7. The water-based acrylic modified epoxy resin emulsion for fast curing for coating multiple substrates according to claim 1, characterized in that: The alcohol ether solvent is any one or more of propylene glycol methyl ether, propylene glycol butyl ether or dipropylene glycol butyl ether.

8. The water-based acrylic modified epoxy resin emulsion for fast curing for coating multiple substrates according to claim 1, characterized in that: The epoxy equivalent of the water-based acrylic acid modified epoxy resin emulsion is 600-660 based on the non-volatile matter, and the non-volatile matter is 50%-56%.

9. A method for preparing a fast-curing aqueous acrylic modified epoxy resin emulsion for coating multiple substrates according to any one of claims 1 to 8, characterized in that: The following steps are involved: (I) Synthesis of epoxy adduct intermediates Add itaconic acid and ethanol in an amount equal to that of itaconic acid in a reaction container, then add part of an alcohol ether solvent so that the azeotropic point of the mixed solution reaches 100° C. to 120° C., mix well and heat to 100° C. to 120° C., add bisphenol A epoxy resin after melting, heat to 120° C. to 130° C., keep warm for 2 hours, test the acid value every hour, stop the reaction when the acid value is ≤5 mgKOH / g, and obtain an epoxy addition intermediate product; (II) Synthesis of acrylic acid modified epoxy resin The temperature is controlled at 100° C. to 110° C., a functional group-containing acrylic monomer, other alkyl acrylate monomers and a first batch of initiators are uniformly mixed in advance, placed in a dropping funnel, and a mixture of the functional group-containing acrylic monomer, other alkyl acrylate monomers and initiators is dripped into the epoxy adduct intermediate product for 2 h to 4 h, and the mixture is kept warm for 2 h; then the remaining initiator and the remaining alcohol ether solvent mixture are dripped for 1 h to 2 h, and finally the mixture is kept warm for 2 h to 3 h to terminate the reaction, thereby obtaining an acrylic modified epoxy resin; the first batch of initiators accounts for 80% of the total mass of the initiators; (III) Preparation of waterborne acrylic modified epoxy resin emulsion Add epoxy emulsifier and acrylic modified epoxy resin into a reaction container, heat to 80°C to 90°C to melt; slowly add deionized water into the reaction container under high-speed stirring until phase inversion is completed to prepare a water-based acrylic modified epoxy resin emulsion.

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