A rapidly curable waterborne acrylic-modified epoxy resin emulsion for multi-substrate coating and a preparation method thereof

Abstract

The application discloses a kind of for multi-substrate coating fast-curable water-based acrylic modified epoxy resin emulsion and its preparation method, first by itaconic acid, alcohol ether solvent and bisphenol A type epoxy resin synthesis epoxy adduct intermediate product, then with other acrylic monomer free radical polymerization is formed acrylic modified epoxy resin with this intermediate product, finally using additional epoxy emulsifier by phase inversion method is made water-based acrylic modified epoxy resin emulsion.The emulsion prepared in the application has higher glass transition temperature, has faster surface dry and curing speed, can satisfy the fast curing of coating film on various substrate workpieces, workpiece offline stacking resistance requirements;Side chain contains a certain amount of carboxyl and hydroxyl, can give coating excellent adhesion, realize good adhesion on various substrates;Resin structure contains a certain amount of bisphenol A type epoxy resin, and epoxy-amine curing agent is well compatible after curing, and coating is uniform.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of coatings, and particularly relates to a water-based acrylic modified epoxy resin emulsion for multi-substrate coating and a preparation method thereof. BACKGROUND

[0002] Two-component water-based 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, and the same coating is applied on the workpiece, which requires the coating film to have universal adhesion to the parts of different 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 the key factors considered by coating enterprises.

[0003] It is known that there are many technical methods for improving the surface drying and curing speed of two-component water-based epoxy coatings, such as improving the activity of epoxy-amine curing agent, commonly by increasing the content of primary amine hydrogen substance; or using raw materials containing phenolic amine and aromatic amine; or by adding a catalyst to improve the curing speed; some documents also use a larger molecular weight epoxy resin to prepare an emulsion to accelerate the surface drying speed of the coating film, but the actual corrosion protection effect at low temperature needs to be improved; patent CN114686069A improves the dryness by splicing a high-Tg polyacrylate resin, but the acrylic ester and the epoxy resin do not undergo chemical grafting reaction, and the coating film has the problems of poor compatibility and easy migration.

[0004] There are few technical solutions for the adhesion of two-component water-based epoxy coating systems with fast surface drying or fast curing on multi-substrate workpieces. The coating film with fast surface drying or fast curing usually has high internal stress, and the adhesion on aluminum alloy substrates, galvanized substrates, finished surfaces of workpieces and electrophoretic primers is not high, which is a key technical difficulty that needs to be considered in industrial coating construction. SUMMARY

[0005] The present application is proposed to solve the problems in the prior art, and the purpose is to provide a water-based acrylic modified epoxy resin emulsion for multi-substrate coating and a preparation method thereof.

[0006] The present application is realized by the following technical solutions:

[0007] A water-based acrylic modified epoxy resin emulsion for multi-substrate coating and fast curing, the water-based acrylic modified epoxy resin emulsion comprises the following components and the mass fraction of each component is as follows:

[0008]

[0009]

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

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

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

[0013] In the technical solution, the other alkyl acrylate monomer is any one or several of methyl methacrylate, butyl acrylate, butyl methacrylate, isooctyl acrylate, isooctyl methacrylate or styrene.

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

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

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

[0017] A preparation method of a water-based acrylic modified epoxy resin emulsion for multi-substrate coating and capable of being quickly cured, comprising the following steps:

[0018] (I) Synthesis of epoxy adduct intermediate product

[0019] In a reaction container, itaconic acid and the same mass fraction of ethanol as the itaconic acid are added, and part of the alcohol ether solvent is added to make the azeotropic point of the mixed solution reach 100-120℃, and after being uniformly mixed, the temperature is raised to 100-120℃, and after being melted, the bisphenol A type epoxy resin is added, the temperature is raised to 120-130℃, and after being kept for 2h, the acid value is tested every 1h, and when the acid value is ≤5mgKOH / g, the reaction is stopped, and the epoxy addition intermediate product is obtained;

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

[0021] The temperature is controlled at 100-110 DEG C, the functional group-containing acrylic monomer, other acrylic alkyl ester monomers and the first batch of initiator are mixed uniformly in advance, and are placed in a dropping funnel, the mixture of the functional group-containing acrylic monomer, other acrylic alkyl ester monomers and the initiator is added dropwise in the epoxy adduct intermediate product, the dropping is completed in 2-4 hours, and the temperature is kept for 2 hours; then the mixture of the remaining initiator and the remaining alcohol ether solvent is added dropwise for 1-2 hours, and finally the temperature is kept for 2-3 hours to end the reaction, so as to obtain the acrylic modified epoxy resin; the first batch of initiator accounts for 80% of the total mass of the initiator;

[0022] (III) preparation of the water-based acrylic modified epoxy resin emulsion

[0023] The epoxy emulsifier and the acrylic modified epoxy resin are added in a reaction container, and are heated to 80-90 DEG C to melt; under high-speed stirring, deionized water is slowly added into the reaction container until the phase inversion is completed, so as to prepare the water-based acrylic modified epoxy resin emulsion.

[0024] The present application has the following beneficial effects:

[0025] The present application provides a water-based acrylic modified epoxy resin emulsion which can be quickly surface-dried, quickly solidified and has good adhesion on various substrates, and a preparation method thereof. An epoxy adduct intermediate product is prepared first, then free radical polymerization is carried out between the intermediate product and other acrylic monomers to form an acrylic modified epoxy resin, and finally an epoxy emulsifier is added to prepare a water-based acrylic modified epoxy resin emulsion by phase inversion. The prepared emulsion has a high glass transition temperature, a fast surface-drying and solidification speed, and can meet the requirements of rapid solidification of the coating film and offline stacking resistance of the workpiece on various substrates. The side chain contains a certain amount of carboxyl and hydroxyl groups, which can endow the coating film with excellent adhesion and good adhesion on various substrates. The resin structure contains a certain amount of bisphenol A type epoxy resin, which has good compatibility with the epoxy-amine curing agent after curing, and the coating film is uniform. DETAILED DESCRIPTION

[0026] In order to enable the personnel in the technical field to better understand the technical scheme of the present application, the technical scheme of the present application is further described below through specific embodiments.

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

[0028] Table 1

[0029]

[0030]

[0031] Example 1

[0032] A preparation method for multi-substrate coating of rapidly solidifiable waterborne acrylic modified epoxy resin emulsion, comprising the following steps:

[0033] (I) Synthesis of epoxy adduct intermediate product

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

[0035] Table 1-1

[0036]

[0037]

[0038] In the reaction container, 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 were added, mixed uniformly, and heated to 100°C. After melting, 233.0 parts by weight of epoxy resin E-51 was added, and the temperature was raised to 120°C. After 2h of incubation at 120°C, the acid value was tested every 1h. When the acid value was ≤5mgKOH / g, the reaction was stopped, and 323.0 parts by weight of epoxy adduct intermediate product was obtained.

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

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

[0041] Table 1-2

[0042]

[0043] In the reaction container, 323.0 parts by weight of epoxy adduct intermediate product was added, and the reaction temperature was controlled at 105°C. The corresponding weight parts of functional group-containing acrylic monomer, other acrylic alkyl ester monomer, and 7.2 parts by weight of initiator were mixed uniformly in advance and placed in a dropping funnel. The mixture of functional group-containing acrylic monomer, other acrylic alkyl ester monomer, and initiator was added dropwise into 323.0 parts by weight of epoxy adduct intermediate product. The addition was completed in 4h, and the mixture was incubated for 2h. Then, the mixture of remaining 1.8 parts by weight of initiator and remaining 18.0 parts by weight of propylene glycol methyl ether was added dropwise for 1h, and finally incubated for 3h to complete the reaction, obtaining the acrylic modified epoxy resin.

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

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

[0046] Table 1-3

[0047] Component Raw material name Amount, parts by weight 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] In a reaction vessel, 376.0 parts by weight of the acrylic modified epoxy resin and 50.0 parts by weight of the epoxy emulsifier according to Table 1-3 were added and heated to 80°C. After the material was completely melted, 266.3 parts by weight of deionized water was slowly and uniformly added at a rotation speed of 2000 rpm for 2 hours. After the phase inversion was completed, a water-based acrylic modified epoxy resin emulsion was obtained. The particle size of the prepared acrylic modified epoxy resin emulsion was 400-600 nm, the epoxy equivalent weight was 618, the non-volatile content was about 52%, and the viscosity was 3458 MPa*s.

[0049] Example 2

[0050] A preparation method for a multi-substrate coating rapidly curable water-based acrylic modified epoxy resin emulsion, comprising the following steps:

[0051] (I) Synthesis of epoxy adduct intermediate

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

[0053] Table 2-1

[0054]

[0055] In a reaction vessel, 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 according to Table 1-1 were added and mixed uniformly. The temperature was raised to 100°C, and after melting, 222.0 parts by weight of epoxy resin E-51 was added. The temperature was raised to 120°C, and after 2 hours of incubation at 120°C, the acid value was tested every hour. When the acid value was ≤5 mgKOH / g, the reaction was stopped, and 306.0 parts by weight of epoxy adduct intermediate was obtained.

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

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

[0058] Table 2-2

[0059]

[0060] In a reaction vessel, 306.0 parts by weight of the epoxy adduct intermediate product was added, and the reaction temperature was controlled at 105°C; the corresponding weight parts of the functional group-containing acrylic monomer, other acrylic alkyl ester monomers and 6.8 parts by weight of the initiator were mixed uniformly in advance and placed in a dropping funnel, and the mixture of the functional group-containing acrylic monomer, other acrylic alkyl ester monomers and the initiator was added dropwise in the 306.0 parts by weight of the epoxy adduct intermediate product, and the dropping was completed in 4h, and the temperature was maintained for 2h; then 1.7 parts by weight of the remaining initiator and 17.0 parts by weight of the remaining propylene glycol methyl ether were added dropwise for 1h, and finally the reaction was completed after maintaining the temperature for 3h, to obtain an acrylic-modified epoxy resin.

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

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

[0063] Table 2-3

[0064]

[0065]

[0066] In a reaction vessel, 306.0 parts by weight of the epoxy adduct intermediate product was added, and the reaction temperature was controlled at 105°C; the corresponding weight parts of the functional group-containing acrylic monomer, other acrylic alkyl ester monomers and 6.8 parts by weight of the initiator were mixed uniformly in advance and placed in a dropping funnel, and the mixture of the functional group-containing acrylic monomer, other acrylic alkyl ester monomers and the initiator was added dropwise in the 306.0 parts by weight of the epoxy adduct intermediate product, and the dropping was completed in 4h, and the temperature was maintained for 2h; then 1.7 parts by weight of the remaining initiator and 17.0 parts by weight of the remaining propylene glycol methyl ether were added dropwise for 1h, and finally the reaction was completed after maintaining the temperature for 3h, to obtain an acrylic-modified epoxy resin.

[0067] Comparative Example 1

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

[0069] (I) Preparation of an epoxy emulsion

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

[0071] Table 3

[0072] Component Raw material name Amount, parts by 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 solvent 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 resin E-20, E-12, 50.0 parts by weight of epoxy emulsifier, 38.0 parts by weight of alcohol ether solvent propylene glycol methyl ether were added, and stirred to warm up to 90°C. After the materials were fully melted, 284.3 parts by weight of deionized water was slowly and uniformly added at a rotation speed of 2000 rad / min for 2h. After the phase inversion was completed smoothly, an epoxy emulsion was obtained, with an epoxy equivalent weight of 628, a non-volatile content of about 52%, and a viscosity of 3570 MPa*s.

[0074] The application performance of the acrylic-modified epoxy resin emulsion of the present application in waterborne epoxy coatings was monitored.

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

[0076] A two-component waterborne epoxy coating was prepared using CTW-WSJ(R7035) waterborne mortar with a non-volatile content of 75.0±2.0%, and CTW-3206 waterborne epoxy curing agent with an active hydrogen equivalent weight of 150 (according to the supply form).

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

[0078] Table 4-1

[0079]

[0080] (II) Coating process

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

[0082] The two-component waterborne epoxy coating main agents 1#, 2#, and 3# were mixed uniformly with corresponding amounts of CTW-3206 waterborne epoxy curing agent, and deionized water was added to adjust the viscosity to 25-35s in a 4-cup coating machine, filtered, and air sprayed.

[0083] (III) Preparation of test panels

[0084] The test panels were tinplate, mirror stainless steel, galvanized steel, aluminum alloy, pure aluminum, and electrophoretic primer panels, which were cleaned without polishing and oil removal. The cold-rolled steel panels were sandblasted to S2.5 grade after oil removal. The two-component waterborne epoxy coatings prepared from Examples 1, 2, and 3 (comparative example) were sprayed on the panels, which were then air dried at room temperature for 7 days.

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

[0086] After the test plate is maintained well, the performance of the coating film is tested, wherein the tinplate sheet, mirror surface stainless steel sheet, galvanized sheet, aluminum alloy sheet, pure aluminum sheet and electrophoretic primer sheet are tested for coating film adhesion according to GB / T 9286-2021 grid method. The cold-rolled steel sheet is tested for coating film surface dry time, coating film hardness after self-drying for 24 h, and coating film adhesion to deionized water and neutral salt spray before and after, wherein the coating film adhesion is tested according to GB / T5210-2006 pull-off method.

[0087] The performance of the coating film of the above sample is detected according to the relevant national standards of the paint industry, and the comparison results are shown in Table 4-2.

[0088] Table 4-2

[0089]

[0090] As can be seen from Table 4-2, the application performance detection results of the water-based acrylic modified epoxy resin emulsion of the present application by preparing the above-mentioned two-component water-based epoxy coating show that the acrylic modified epoxy resin emulsion prepared by the technical scheme of the present application for multi-substrate coating can be quickly cured, can ensure the rapid curing of the coating film, and can impart excellent adhesion of the coating film to various substrates, while having good corrosion resistance.

[0091] The present application provides a kind of for multi-substrate coating can be quickly cured acrylic modified epoxy resin emulsion, epoxy resin and itaconic acid are grafted by chemistry, form epoxy resin adduct intermediate product, then modified with acrylic acid, provide the adhesion, flexibility etc. Characteristics of better coating film, so as to reach the balance of the excellent adhesion of coating film to various substrates, quick curing and corrosion resistance after preparing paint.

[0092] The applicant declares that the above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto. It should be understood by those skilled in the art that any changes or substitutions within the technical scope disclosed by the present application can be easily thought of by those skilled in the art, and all fall within the protection scope and disclosure scope of the present application.

Claims

1. A process for the preparation of a waterborne, acryl-modified epoxy resin emulsion for multi-substrate coating which can be rapidly cured, characterized in that: The method comprises the following steps: (I) synthesis of epoxy adduct intermediate In a reaction vessel, itaconic acid and the same mass fraction of ethanol as itaconic acid are added, and part of alcohol ether solvent is added to make the azeotropic point of the mixed solution reach 100-120℃. After being mixed uniformly, the temperature is raised to 100-120℃, and after melting, bisphenol A type epoxy resin is added, and the temperature is raised to 120-130℃. After being kept for 2 hours, the acid value is tested every hour, and the reaction is stopped when the acid value is ≤5 mgKOH / g, to obtain an epoxy adduct intermediate; (II) synthesis of acrylic modified epoxy resin The temperature is controlled at 100-110℃. The functional group-containing acrylic monomer, other acrylic alkyl ester monomer and the first batch of initiator are mixed uniformly in advance and placed in a dropping funnel. The mixture of the functional group-containing acrylic monomer, other acrylic alkyl ester monomer and initiator is added dropwise into the epoxy adduct intermediate. The dropping is completed in 2-4 hours, and the temperature is kept for 2 hours. Then the mixture of the remaining initiator and remaining alcohol ether solvent is added dropwise for 1-2 hours, and finally the temperature is kept for 2-3 hours to complete the reaction, to obtain an acrylic modified epoxy resin. The first batch of initiator accounts for 80% of the total mass of the initiator. (III) preparation of water-based acrylic modified epoxy resin emulsion In a reaction vessel, epoxy emulsifier and acrylic modified epoxy resin are added, and heated to 80-90℃ to melt. Deionized water is slowly added into the reaction vessel under high-speed stirring until the phase inversion is completed, to prepare a water-based acrylic modified epoxy resin emulsion. The water-based acrylic modified epoxy resin emulsion comprises the following components and mass fractions of each component: Epoxy emulsifier 6-8 parts; Bisphenol A type epoxy resin 20-30 parts; Itaconic acid 2-3 parts; Ethanol 2-3 parts; Functional group-containing acrylic monomer 1.8-3.3 parts; Other acrylic alkyl ester monomer 15-18 parts; Initiator 0.8-1 part; Alcohol ether solvent 6-9 parts; Deionized water 35-40 parts; The epoxy emulsifier is a polyethylene oxide-epoxy resin polymer. The functional group-containing acrylic monomer is any one or several of acrylic acid, methacrylic acid, hydroxypropyl acrylate or hydroxyethyl methacrylate. The other acrylic alkyl ester monomer is any one or several of methyl methacrylate, butyl acrylate, butyl methacrylate, isooctyl acrylate or isooctyl methacrylate.

2. The method for the preparation of a waterborne, acryl-modified epoxy resin emulsion for the rapid curable coating of multiple substrates according to claim 1, characterized in that The bisphenol A type epoxy resin is any one or several of E-51, E-44 or E-20.

3. The method for preparing a waterborne, acryl-modified epoxy resin emulsion that can be rapidly cured for multi-substrate coating according to claim 1, characterized by: The initiator is azobisisobutyronitrile.

4. The method for preparing a waterborne, acryl-modified epoxy resin emulsion for multi-substrate coating that can be rapidly cured according to claim 1, characterized by: The alcohol ether solvent is any one or several of propylene glycol methyl ether, propylene glycol butyl ether or dipropylene glycol butyl ether.

5. The method for preparing a waterborne, acryl-modified epoxy resin emulsion for multi-substrate coating that can be rapidly cured according to claim 1, characterized by: The epoxy equivalent of the water-based acrylic modified epoxy resin emulsion is 600-660 according to the non-volatile content, and the non-volatile content is 50%-56%.

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