Water-based acrylic emulsion for metal passivation solution and production method of water-based acrylic emulsion

Abstract

The invention discloses a water-based acrylic emulsion for a metal passivation solution and a production method of the water-based acrylic emulsion. The water-based acrylic emulsion is prepared from the following raw materials in percentage by mass: 10%-15% of methyl methacrylate, 12%-18% of butyl acrylate, 1.0%-2.0% of a functional monomer, 0.7%-1.2% of acrylonitrile, 0.1%-0.5% of an oxidant, 0.03%-0.08% of a reducing agent, 0.2%-0.4% of a nonionic emulsifier, 1%-5% of a pH regulator, 5%-10% of isopropanol and the balance of deionized water. The functional monomer is a mixture of at least one of acrylic acid and / or methacrylic acid and mercaptoacetic acid-2-ethylhexyl ester, and the mass ratio of the acrylic acid and / or methacrylic acid to the mercaptoacetic acid-2-ethylhexyl ester is (8-10): 1. According to the raw material matching and production method disclosed by the invention, the adhesive force, water resistance and salt fog resistance of the fingerprint-resistant coating prepared from the water-based acrylic emulsion are very excellent.

Description

Technical Field

[0001] The present invention belongs to the technical field of acrylic emulsion synthesis, and particularly relates to an aqueous acrylic emulsion for metal passivation liquid and a production method thereof. Background Art

[0002] Galvanized steel sheets are widely used. However, in a humid environment, the galvanized layer is prone to corrosion, forming dark gray or white loose corrosion products - white rust on the surface of the galvanized layer. Over time, red rust will appear, thus losing the anti-corrosion effect. In order to improve the corrosion resistance of the coating, after electro-galvanizing or hot-galvanizing the steel material surface, the coating needs to be passivated to form a dense passivation film on the coating surface, improve the corrosion resistance of the coating, and extend the service life of the workpiece.

[0003] The basic film-forming substances of existing passivation liquids (or fingerprint-resistant coating agents) are all aqueous organic resins, and the polymerization method is emulsion polymerization, including polyethylene resins, silane resins, acrylic resins, epoxy resins, polyurethane resins, etc. Acrylic resins have a wide source, moderate cost, and have fast drying properties, high hardness, and excellent weather resistance, and are widely used in coatings or binders.

[0004] For example: Patent document CN118271948A mentions the use of a composite system of zirconium saltification (ammonium zirconium carbonate), silane coupling agent, ammonium vanadate / sodium periodate, and aqueous polyurethane / acrylic resin to improve the film layer density through the interpenetrating network of linear and network structures, and form a stable passivation film through redox reactions. Patent document CN114350239A forms a network structure in which linear and network structures of polyurethane resin / acrylic resin penetrate each other by mixing linear and network structures of polyurethane resin / acrylic resin, and adds a silane coupling agent and silica sol, significantly improving the salt spray resistance and solvent resistance. Patent document CN117304789A is prepared by mixing a polyurethane emulsion, a modified filler, and lithium silicate. The mercapto group on the modified filler is grafted with the double bond on the polyurethane molecular chain to improve the density of the coating film and increase the fingerprint-resistant effect. At the same time, the polyurethane molecular chain contains organosilicon segments, long-chain fluoroalkyl groups, and long-chain alkyl groups, and itself is a hyperbranched structure, making the formed coating film have good water and oil repellent effects. Summary of the Invention

[0005] The purpose of the present invention is to provide an aqueous acrylic emulsion for metal passivation liquid and a preparation method thereof to meet the market demand for aqueous acrylic emulsions for metal passivation liquid.

[0006] To achieve the above purpose, the technical solution of the present invention is:

[0007] An aqueous acrylic emulsion for a metal passivation solution according to the present invention is prepared from raw materials including the following mass fractions: 10% - 15% of methyl methacrylate, 12% - 18% of butyl acrylate, 1.0% - 2.0% of a functional monomer, 0.7% - 1.2% of acrylonitrile, 0.1% - 0.5% of an oxidant, 0.03% - 0.08% of a reducing agent, 0.2% - 0.4% of a non-ionic emulsifier, 1% - 5% of a pH regulator, 5% - 10% of isopropanol, and the balance being deionized water; the functional monomer is a mixture of at least one of acrylic acid and / or methacrylic acid and 2-ethylhexyl mercaptoacetate, and the mass ratio of the two is (8 - 10):1.

[0008] Preferably, an aqueous acrylic emulsion for a metal passivation solution according to the present invention is prepared from raw materials including the following mass fractions: 13% of methyl methacrylate, 15% of butyl acrylate, 1.46% of a functional monomer, 0.89% of acrylonitrile, 0.2% of an oxidant, 0.07% of a reducing agent, 0.27% of a non-ionic emulsifier, 2% of a pH regulator, 7.2% of isopropanol, and the balance being deionized water.

[0009] Preferably, the oxidant is azobisisovaleronitrile and tert-butyl hydroperoxide, and the mass ratio of the two is (1.1 - 1.3):1.

[0010] Preferably, the reducing agent is sodium erythorbate; the pH regulator is ammonia water; the non-ionic emulsifier is Clariant Emulsogen LCN 407 non-ionic emulsifier.

[0011] Preferably, an aqueous acrylic emulsion for a metal passivation solution according to the present invention further includes 0.03% - 0.1% of an adjustment buffer and 0.1% - 0.5% of a preservative; the adjustment buffer is ammonium bicarbonate; the preservative is at least one of isothiazoline-based preservatives (such as Rohm and Haas preservative KATHON LXE, Carson preservative).

[0012] A production method of an aqueous acrylic emulsion for a metal passivation solution according to the present invention includes the following steps:

[0013] S1, adding the functional monomer and 50% - 60% of methyl methacrylate into an appropriate amount of isopropanol, stirring evenly to obtain a monomer mixture A; adding the butyl acrylate, acrylonitrile and the remaining methyl methacrylate into an appropriate amount of deionized water, stirring evenly to obtain a monomer mixture B;

[0014] S2, adding 75% - 85% of azobisisovaleronitrile and 85% - 95% of isopropanol into a reaction kettle, stirring and heating to 73 - 80 °C, and starting to dropwise add the monomer mixture A, with the dropping time being 120 - 180 min;

[0015] S3. After the dropping of the monomer mixture A is completed, quickly add the remaining azodiisovaleronitrile to the reaction kettle and make up the remaining isopropanol; keep the temperature at 73 - 80 °C and continue the reaction for 120 - 180 min.

[0016] S4. Dropwise add ammonia water diluted with deionized water to the reaction kettle over 20 - 50 min, and adjust the pH value to 8.5 - 9.0.

[0017] S5. Add 70% - 95% deionized water to the reaction kettle, stir and heat up to 65 - 75 °C; add tert-butyl hydroperoxide, and at the same time dropwise add the monomer mixture B, reducing agent and non-ionic emulsifier to the reaction kettle, with the dropping time lasting 100 - 150 min; continue to keep the temperature at 65 - 78 °C and carry out the insulation reaction for 70 - 120 min.

[0018] S6. Cool down to below 40 °C, adjust the solid content to 28.0% - 33.0% with the remaining deionized water, filter and discharge to obtain the aqueous acrylic emulsion.

[0019] The aqueous acrylic emulsion is a milky white to slightly yellowish translucent emulsion, with a viscosity of 300 - 1000 mPa·s at 25 °C and a pH value of 7.0 - 9.0.

[0020] Furthermore, when it is necessary to add a buffering agent and / or a preservative, it needs to be added after the end of step S5, and after stirring evenly, then carry out step S6.

[0021] Both the oxidant and the preservative should be first dissolved in deionized water to form a solution before use.

[0022] Compared with the prior art, the positive effects of the present invention are as follows:

[0023] The present invention combines acrylic acid / methacrylic acid (carboxylic acid monomers) with 2-ethylhexyl thioglycolate (abbreviated as EHTG, mercaptan chain transfer agent), which has the dual functions of carboxyl anchoring and thiol catalytic passivation. Together with the co-dispersion of isopropyl ester, the emulsion particle size can be controlled within 80 - 120 nm; introducing a cyano group (-CN) into the MMA / BA main chain enhances the chemical medium resistance of the aqueous acrylic emulsion; the preferred raw material combination and reasonable production method ensure that the adhesion, water resistance and salt spray resistance of the fingerprint-resistant coating prepared with the aqueous acrylic emulsion of the present invention are all excellent. Specific Embodiments

[0024] Those of ordinary skill in the art in this technical field should recognize that this embodiment is only used to illustrate the present invention and is not used as a limitation to the present invention. As long as changes and modifications are made to the embodiment within the scope of the present invention, they can all be within the scope of the claims of the present invention.

[0025] Examples 1 to 5 and Comparative Example 1

[0026] The raw material ratios of Examples 1 to 5 and Comparative Example 1 are shown in Table 1. The production method of the aqueous acrylic emulsion for the metal passivation solution includes the following steps:

[0027] S1, Add the functional monomer and 55% of methyl methacrylate to an appropriate amount of isopropanol, stir evenly to obtain monomer mixture A; add butyl acrylate, acrylonitrile and the remaining methyl methacrylate to an appropriate amount of deionized water, stir evenly to obtain monomer mixture B;

[0028] S2, Add 80% of azodiisopentanenitrile and 85% of isopropanol to the reaction kettle, stir and heat up to 75 °C, start dropping monomer mixture A, the dropping time is 150 min, and maintain the temperature at 74 - 77 °C during the dropping;

[0029] S3, After the dropping of monomer mixture A is completed, quickly add the remaining azodiisopentanenitrile to the reaction kettle and make up the remaining isopropanol; continue to react at 73 - 80 °C for 150 min;

[0030] S4, Drop ammonia water diluted with deionized water into the reaction kettle, the dropping time is 30 min, and adjust the pH value to 8.7;

[0031] S5, Add 85% of deionized water to the reaction kettle, stir and heat up to 68 °C; add tert-butyl hydroperoxide, and at the same time drop monomer mixture B, reducing agent and non-ionic emulsifier into the reaction kettle, the dropping time lasts for 120 min; continue to keep the temperature at 65 - 78 °C and react for 90 min;

[0032] S6, Cool down to below 40 °C, adjust the solid content to 31.0% with the remaining deionized water, filter and discharge to obtain a milky white to slightly yellowish translucent aqueous acrylic emulsion, and measure its viscosity at 25 °C to meet 300 - 1000 mPa·s, and the pH value is 7.0 - 9.0.

[0033] Table 1 Raw material ratios of Examples 1 to 5 and Comparative Examples 1 to 2, unit wt%

[0034]

[0035]

[0036] Comparative Example 1 is the comparative example of Example 1. The difference is that 2-ethylhexyl mercaptoacetate, the functional monomer, is not added in Comparative Example 1.

[0037] Comparative Example 2 is the comparative example of Example 1. The difference is that the addition amount of acrylonitrile in Comparative Example 2 is increased to 1.45%.

[0038] Test experimental example

[0039] The waterborne acrylic emulsions obtained in Examples 1-5 and Comparative Examples 1-2 were tested:

[0040] 1. Take a part for storage stability test.

[0041] 2. Prepare the fingerprint-resistant coating liquid for galvanized steel plates with the waterborne acrylic emulsion, including the following components: 45 parts of waterborne acrylic emulsion, 15 parts of silane coupling agent KH-550, 3 parts of fluoziric acid, 5 parts of high molecular silicone wax emulsion, and 45 parts of deionized water.

[0042] Determine the adhesion according to the cross-cut method.

[0043] Determine the water resistance according to the provisions of 5.1 in "GB-T1733-1993 Test Method for Water Resistance of Paint Films" (coating film thickness 18μm), immerse it in grade III water meeting the requirements of GB / T6682, take out the sample plate after the specified time for observation, and evaluate the results according to the provisions of GB / T1766-2008.

[0044] Determine the salt spray resistance according to the provisions of 5.4 in "GB / T1771-2007 Determination of Resistance to Neutral Salt Spray of Paints and Varnishes" (coating film thickness 18μm). In a test chamber at a temperature of 35°C, place the prepared sample plate in a salt spray chamber. At a pressure barrel temperature of 47°C, spray with 5wt% sodium chloride brine with a pH of 7.0 at an air pressure of 1.0 kgf / cm 2 ; after spraying the sample plate for 300h, wash it with water and dry it, and observe whether there is white rust or red rust on the surface of the sample plate and the percentage of the corrosion area in the total area of the product.

[0045] Table 2 Test results of Examples 1-3 and Comparative Examples 1-3

[0046]

[0047]

[0048] It can be seen from Table 2 that in the present invention, acrylic acid / methacrylic acid (carboxylic acid monomer) is compounded with 2-ethylhexyl thioglycolate, and at the same time, two oxidants, azodiisovaleronitrile and tert-butyl hydroperoxide, are used to introduce cyano (-CN) into the MMA / BA main chain, enhancing the chemical medium resistance of the waterborne acrylic emulsion. The preferred raw material combination and reasonable production method ensure that the fingerprint-resistant coating prepared with the waterborne acrylic emulsion of the present invention has excellent adhesion, water resistance and salt spray resistance.

Claims

1. An aqueous acrylic emulsion for metal passivation solution, characterized in that: The invention is prepared from raw materials including the following mass fractions: 10% to 15% methyl methacrylate, 12% to 18% butyl acrylate, 1.0% to 2.0% functional monomer, 0.7% to 1.2% acrylonitrile, 0.1% to 0.5% oxidant, 0.03% to 0.08% reductant, 0.2% to 0.4% nonionic emulsifier, 1% to 5% pH regulator, 5% to 10% isopropanol, and the balance is deionized water; the functional monomer is a mixture of at least one of acrylic acid and / or methacrylic acid and 2-ethylhexyl thioglycolate, and the mass ratio of the two is (8 to 10):

1.

2. The aqueous acrylic emulsion according to claim 1, characterized in that The invention is prepared from the following raw materials in mass fractions: 13% of methyl methacrylate, 15% of butyl acrylate, 1.46% of functional monomer, 0.89% of acrylonitrile, 0.2% of oxidant, 0.07% of reducing agent, 0.27% of nonionic emulsifier, 2% of pH adjusting agent, 7.2% of isopropanol, and the balance is deionized water.

3. The aqueous acrylic emulsion according to claim 1, characterized in that The oxidant is azobisisovaleronitrile and tert-butyl hydroperoxide, and the mass ratio of the two is (1.1-1.3):

1.

4. The aqueous acrylic emulsion according to claim 1, characterized in that The reducing agent is sodium isoascorbate; the pH adjusting agent is ammonia water; and the nonionic emulsifier is Clariant Emulsogen LCN 407 nonionic emulsifier.

5. The aqueous acrylic emulsion according to claim 1, characterized in that A water-based acrylic emulsion for metal passivation liquid also includes 0.03% to 0.1% of a regulating buffer and 0.1% to 0.5% of a preservative; the regulating buffer is ammonium bicarbonate; and the preservative is at least one of isothiazolinyl preservatives.

6. The method for producing an aqueous acrylic emulsion according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1, adding the functional monomer and 50% to 60% of methyl methacrylate into an appropriate amount of isopropanol, stirring evenly, to obtain a monomer mixture A; adding the butyl acrylate, acrylonitrile and the remaining methyl methacrylate into an appropriate amount of deionized water, stirring evenly, to obtain a monomer mixture B; S2, adding 75% to 85% of azobisisovaleronitrile and 85% to 95% of isopropanol into a reaction kettle, stirring and heating to 73 to 80° C., and starting to dropwise add the monomer mixture A for 120 to 180 min; S3, after the monomer mixture A is added dropwise, the remaining azobisisovaleronitrile is quickly added to the reaction kettle to make up the remaining isopropanol; the reaction is continued at 73-80° C. for 120-180 min; S4, adding ammonia diluted with deionized water to the reactor dropwise for 20 to 50 minutes, and adjusting the pH value to 8.5 to 9.0; S5, add 70% to 95% of deionized water to the reactor, stir and heat to 65 to 75° C.; add tert-butyl hydroperoxide, and simultaneously drop the monomer mixture B, reducing agent and nonionic emulsifier into the reactor for 100 to 150 minutes; continue to heat and react at 65 to 78° C. for 70 to 120 minutes; S6, cooling to below 40°C, adjusting the solid content to 28.0% to 33.0% with the remaining deionized water, filtering the material to obtain the aqueous acrylic emulsion.

7. The method for producing an aqueous acrylic emulsion according to claim 6, characterized in that: The aqueous acrylic emulsion is a milky white to slightly yellow translucent emulsion, with a viscosity of 300 to 1000 mPa.s at 25° C. and a pH value of 7.0 to 9.

0.

8. The method for producing an aqueous acrylic emulsion according to claim 6, characterized in that: When it is necessary to add a buffer and / or a preservative, add them after step S5, stir them evenly, and then proceed to step S6.

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