Water-based acrylic emulsion for steel structure coating and production method of water-based acrylic emulsion

Abstract

The invention discloses a water-based acrylic emulsion for a steel structure coating. The water-based acrylic emulsion is prepared from the following raw materials in percentage by mass: 10%-15% of an acrylic soft monomer, 25%-30% of an acrylic hard monomer, 0.8%-1.5% of a functional monomer, 0.5%-1.0% of a crosslinking monomer, 0.1%-0.3% of an initiator, 0.5%-1.0% of an anionic emulsifier, 0.08%-0.15% of a nonionic emulsifier, 0.03%-0.15% of a regulating buffer agent, 0.5%-1.2% of a pH value regulator, 0.02%-0.08% of an oxidizing agent, 0.02%-0.08% of a reducing agent, 0.1%-0.5% of a preservative and the balance of deionized water. The water-based acrylic emulsion disclosed by the invention can be self-crosslinked at room temperature, a paint film has relatively good mechanical properties, adhesive force, solvent resistance and mechanical properties, an emulsification system is stable, and the emulsification time is short.

Description

Technical Field

[0001] The invention belongs to the technical field of production of water-based acrylic emulsions, and in particular relates to a water-based acrylic emulsion for steel structure coatings and a production method thereof. Background Art

[0002] In water-based paints, the base material plays a decisive role in the performance of the paint film. Acrylic resins are widely used as base materials for paints because of their wide sources, moderate cost, quick drying, high hardness and excellent weather resistance.

[0003] Steel plates are corroded to varying degrees due to environmental factors during storage and use, causing serious economic losses and safety hazards. Applying an anti-corrosion layer on the surface of steel to prevent uniform corrosion, uneven corrosion, pitting corrosion, stress corrosion and other metal corrosion phenomena of steel structures is the most common and cost-effective protective measure.

[0004] Steel structure anti-corrosion coatings have three important functions in protecting steel structures: shielding, corrosion inhibition and cathodic protection. Steel structure anti-corrosion coatings are a kind of polymer solution, which is coated on the outer surface of the steel structure and forms a coating after drying or curing, thereby preventing the external corrosive medium from contacting the metal under the coating, avoiding metal corrosion and playing a protective role.

[0005] At present, the anti-corrosion coatings for steel structures are mainly oil-based paints, such as alkyd paint, nitro paint and epoxy paint which is famous for its strong adhesion. With the society's emphasis on environmental protection, water-based anti-corrosion coatings have gradually developed. In water-based anti-corrosion coatings, the base material plays a decisive role in the performance of the paint film. The commonly used base materials for water-based anti-corrosion coatings are: water-based acrylic emulsion, water-based alkyd resin, water-based epoxy ester-acrylic resin hybrid, two-component water-based polyurethane, and water-based epoxy resin. Among them, water-based acrylic emulsion is the most cost-effective polymer among various water-based coating film-forming materials due to its excellent weather resistance and flexibility, short drying time, and convenient construction.

[0006] The current water-based acrylic anti-corrosion coatings for steel structures generally have good water and salt water resistance, but poor salt spray resistance, become brittle at low temperatures, and become sticky at high temperatures. At the same time, the wet adhesion of the paint film is poor, which can cause blistering of the paint film and corrosion of the substrate; it is easy to flash rust, and water-based coatings introduce water during the construction stage, and the iron substrate comes into contact with water, causing flash rust; in order to improve the anti-corrosion performance, some researchers will introduce a large amount of phosphate esters and silicone monomers into the emulsion, but silicone monomers are easily hydrolyzed, resulting in unstable performance, and phosphate ester monomers are easily complexed with anti-rust paint fillers, resulting in gelation of the coating during storage.

[0007] Patent document CN118146424A discloses a self-drying high-gloss water-based acrylic emulsion for steel structure and its preparation method, comprising: component A: 60-70 parts of hard monomer, 30-40 parts of soft monomer, 20-25 parts of deionized water, 2-3 parts of anionic emulsifier, 1-1.5 parts of nonionic emulsifier, 0.05-0.1 parts of initiator; component B: 20-60 parts of hard monomer, 20-60 parts of soft monomer, 30-60 parts of functional monomer, 40-60 parts of deionized water, 2-3 parts of anionic emulsifier, 1-1.5 parts of nonionic emulsifier, 0-2 parts of molecular weight regulator; component C: 0.2-0.5 parts of anionic emulsifier, 0.1-1.3 parts of cationic emulsifier, 0. 002-0.005 parts of regulating buffer, 18-28 parts of deionized water; wherein the mass ratio of 5-10% of the A component pre-reacts with the C component to generate free radicals and initiate polymerization; the functional monomer is any one or more of methacrylic acid, methacrylic acid hydroxyl monomer, methacrylate glycidyl ester, diacetone acrylamide, adipic acid dihydrazide; the hard monomer is any one or more of styrene, butyl methacrylate, methyl methacrylate; the soft monomer is any one or more of 2-ethylhexyl acrylate and butyl acrylate; the molecular weight regulator is α-methylstyrene linear dimer; the initiator is any one or more of ammonium persulfate and sodium persulfate; the regulating buffer includes sodium bicarbonate. However, the reaction process of the document is relatively complicated, and the mechanical properties, adhesion and corrosion resistance still cannot meet the requirements. Summary of the invention

[0008] The purpose of the present invention is to provide a water-based acrylic emulsion for steel structure coating and a production method thereof, so as to solve the problems of poor solvent resistance and flexibility existing in the prior art.

[0009] The purpose of the present invention is achieved through the following technical solutions:

[0010] The invention discloses a water-based acrylic emulsion for steel structure coating, which is prepared from the following raw materials in mass fraction: 10% to 15% of acrylic soft monomer, 25% to 30% of acrylic hard monomer, 0.8% to 1.5% of functional monomer, 0.5% to 1.0% of cross-linking monomer, 0.1% to 0.3% of initiator, 0.5% to 1.0% of anionic emulsifier, 0.08% to 0.15% of nonionic emulsifier, 0.03% to 0.15% of regulating buffer, 0.5% to 1.2% of pH value regulator, 0.02% to 0.08% of oxidant, 0.02% to 0.08% of reducing agent, 0.1% to 0.5% of preservative, and the balance is deionized water;

[0011] The functional monomer is a mixture of at least one of acrylic acid and / or methacrylic acid and allyl methacrylate, and the mass ratio of the two is (3-6):1; the cross-linking monomer is diacetone acrylamide and adipic acid dihydrazide in a mass ratio of (1.8-2.3):1; the acrylic soft monomer is isooctyl acrylate; and the acrylic hard monomer is a mixture of styrene and methyl methacrylate in a mass ratio of (1-2):1.

[0012] Preferably, the anionic emulsifier is sodium dodecyl sulfate (SDS) or / and sodium dodecyl sulfonate, and the nonionic emulsifier is Clariant Emulsogen LCN 407 nonionic emulsifier.

[0013] Preferably, the initiator is ammonium persulfate and / or sodium persulfate; the adjusting buffer is ammonium bicarbonate; and the pH adjusting agent is aqueous ammonia.

[0014] Preferably, the oxidant is tert-butyl hydroperoxide; the reducing agent is sodium formaldehyde sulfoxylate (commonly known as bleaching powder); and the preservative is at least one of the isothiazolin preservatives (such as Rohm and Haas preservative KATHON LXE, Kathon preservative).

[0015] A method for producing a water-based acrylic emulsion for steel structure coatings of the present invention comprises the following steps:

[0016] S1, adding 1 / 3 to 2 / 3 of the nonionic emulsifier and the anionic emulsifier into an appropriate amount of deionized water and stirring evenly; then adding diacetoneamine thereto and stirring evenly; continuing to add the functional monomer, the acrylic soft monomer and the acrylic hard monomer, stirring and emulsifying sufficiently to obtain a pre-emulsion; and mixing the initiator with an appropriate amount of deionized water to obtain an initiator solution;

[0017] S2, add an appropriate amount of deionized water to the reactor, then add the remaining nonionic emulsifier and anionic emulsifier, stir and heat to 80-88° C. under nitrogen protection; first add 1 / 30-1 / 10 of the pre-emulsion to the reactor, then add 1 / 3-2 / 3 of the initiator, and keep the reaction at 83-86° C. for 10-30 minutes;

[0018] S3, adding the remaining pre-emulsion and the remaining initiator dropwise for 200 to 300 minutes, and then keeping the temperature at 83 to 86°C for 30 to 60 minutes;

[0019] S4, cooling to below 75°C, and simultaneously dropping the oxidant and the reductant into the reaction kettle for post-elimination reaction, the dropping time lasting 20 to 40 minutes; after the dropping is completed, keeping the temperature at 65 to 75°C for 30 to 60 minutes;

[0020] S5, cooling to below 40° C., adding the pH adjuster to adjust the pH value to 7-8; and then sequentially adding the adipic acid dihydrazide and the preservative;

[0021] S6, adjusting the solid content to 40.0% to 44.0% with the remaining deionized water, filtering and discharging the material after the test is qualified, to obtain a water-based acrylic emulsion;

[0022] The 4-cup coating viscosity of the aqueous acrylic emulsion at 25° C. is 15 to 35 seconds.

[0023] The pH adjuster should be added slowly and stopped immediately when the pH value reaches 7-8.

[0024] The oxidant, the reducing agent and the preservative should all be dissolved in deionized water to form a solution before use.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] The present invention adopts allyl methacrylate as an acrylic acid monomer for compounding, and simultaneously adds diacetone acrylamide and adipic acid dihydrazide, so that the water-based acrylic emulsion of the present invention can not only be self-crosslinked at room temperature, but also has a paint film with good mechanical properties, adhesion, solvent resistance and mechanical properties, a stable emulsification system, a short emulsification time, high reaction efficiency and controllable process. DETAILED DESCRIPTION

[0027] The present invention is further described below by means of specific embodiments, which are only used to illustrate the present invention rather than to limit the present invention.

[0028] Example 1

[0029] The water-based acrylic emulsions for steel structure coatings of Examples 1 to 3 and Comparative Examples 1 to 3 have a formula as shown in Table 1, and a production method thereof comprises the following steps:

[0030] S1, add 1 / 2 of the nonionic emulsifier and the anionic emulsifier into an appropriate amount of deionized water and stir evenly; then add diacetone acrylamide thereto and stir evenly; continue to add functional monomers, acrylic soft monomers and acrylic hard monomers, stir and emulsify thoroughly to obtain a pre-emulsion; mix the initiator with an appropriate amount of deionized water to obtain an initiator solution;

[0031] S2, add an appropriate amount of deionized water to the reactor, then add the remaining nonionic emulsifier and anionic emulsifier, stir and heat to 85°C under nitrogen protection; first add 1 / 20 of the pre-emulsion to the reactor, then add 1 / 3 of the initiator, and keep the reaction at 83-86°C for 20 minutes;

[0032] S3, adding the remaining pre-emulsion and the remaining initiator dropwise for 275 minutes, and then keeping the temperature at 83-86°C for 30 minutes;

[0033] S4, cooling to 70°C, and simultaneously adding an oxidant and a reductant to the reaction kettle for post-elimination reaction, the addition time lasting for 30 minutes; after the addition is completed, the temperature is kept at 65-75°C for 30 minutes;

[0034] S5, cooling to below 40°C, adding a pH adjuster to adjust the pH to 7; adding adipic acid dihydrazide solution, stirring for 15 minutes; adding a preservative solution, stirring for 15 minutes;

[0035] S6, adjusting the solid content to 43.0% with the remaining deionized water, filtering and discharging the material after the test is qualified, and obtaining an aqueous acrylic emulsion with a 4-cup coating viscosity of 15 to 35 seconds at 25°C.

[0036] Table 1 Raw materials and proportions of Examples 1 to 3 and Comparative Examples 1 to 3, unit: wt%

[0037]

[0038] Comparative Example 1 is a comparative example of Example 1, except that no functional monomer allyl methacrylate is added in Comparative Example 1.

[0039] Comparative Example 2 is a comparative example of Example 1, except that the amount of allyl methacrylate added in Comparative Example 2 is relatively large.

[0040] Comparative Example 3 is a comparative example of Example 1, except that the added amounts of the cross-linking monomers diacetone acrylamide and adipic acid dihydrazide in Comparative Example 3 are relatively small.

[0041] The water-based acrylic emulsions obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were tested. Three embodiments and three comparative examples of the water-based acrylic emulsions of the present invention were applied to water-based coatings, and the water-based coatings included the following components: 50 parts of water-based acrylic emulsions, 30 parts of color paste, 2 parts of film formers, and 1 part of water-based leveling agents. Adhesion was measured according to the cross-hatch method. The coating film was subjected to a reverse impact test according to the test standard HGT3830-2006. The water resistance (coating film thickness 18 μm) was measured according to the provisions of 5.1 of "GB-T1733-1993 Paint Film Water Resistance Test Method", and the sample was taken out for observation after the specified time, and the evaluation of the results was carried out according to the provisions of GB / T1766-2008. The salt spray resistance (coating thickness 18μm) shall be measured according to the provisions of 5.4 of GB / T1771-2007 Determination of neutral salt spray resistance of paints and varnishes. If blistering, rusting, cracking and peeling of the paint film occur, the results shall be evaluated according to the provisions of GB / T1766-2008.

[0042] Table 2 Test results of Examples 1 to 3 and Comparative Examples 1 to 3

[0043]

[0044] As can be seen from Table 2, the present invention uses allyl methacrylate as an acrylic acid monomer for compounding, and simultaneously adds diacetone acrylamide and adipic acid dihydrazide, so that the water-based acrylic emulsion of the present invention can not only be self-crosslinked at room temperature, but also has a paint film with good mechanical properties, adhesion, solvent resistance and mechanical properties, a stable emulsification system and a short emulsification time.

Claims

1. A water-based acrylic emulsion for steel structure coating, characterized in that: The invention is prepared from the following raw materials in mass fraction: 10% to 15% acrylic soft monomer, 25% to 30% acrylic hard monomer, 0.8% to 1.5% functional monomer, 0.5% to 1.0% cross-linking monomer, 0.1% to 0.3% initiator, 0.5% to 1.0% anionic emulsifier, 0.08% to 0.15% nonionic emulsifier, 0.03% to 0.15% adjusting buffer, 0.5% to 1.2% pH value adjusting agent, 0.02% to 0.08% oxidant, 0.02% to 0.08% reducing agent, 0.1% to 0.5% preservative, and the balance is deionized water; The functional monomer is a mixture of at least one of acrylic acid and / or methacrylic acid and allyl methacrylate, and the mass ratio of the two is (3-6):1; the cross-linking monomer is diacetone acrylamide and adipic acid dihydrazide in a mass ratio of (1.8-2.3):1; the acrylic soft monomer is isooctyl acrylate; and the acrylic hard monomer is a mixture of styrene and methyl methacrylate in a mass ratio of (1-2):

1.

2. The water-based acrylic emulsion for steel structure coating according to claim 1, characterized in that: The anionic emulsifier is sodium lauryl sulfate or / and sodium lauryl sulfonate, and the nonionic emulsifier is Clariant Emulsogen LCN 407 nonionic emulsifier.

3. The water-based acrylic emulsion for steel structure coating according to claim 1, characterized in that: The initiator is ammonium persulfate and / or sodium persulfate; the regulating buffer is ammonium bicarbonate; and the pH value regulator is ammonia water.

4. The water-based acrylic emulsion for steel structure coating according to claim 1, characterized in that: The oxidant is tert-butyl hydroperoxide; the reducing agent is sodium formaldehyde sulfoxylate; and the preservative is at least one of isothiazolinyl preservatives.

5. The method for producing a water-based acrylic emulsion for steel structure coating according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1, adding 1 / 3 to 2 / 3 of the nonionic emulsifier and the anionic emulsifier into an appropriate amount of deionized water and stirring evenly; then adding diacetoneamine thereto and stirring evenly; continuing to add the functional monomer, the acrylic soft monomer and the acrylic hard monomer, stirring and emulsifying sufficiently to obtain a pre-emulsion; and mixing the initiator with an appropriate amount of deionized water to obtain an initiator solution; S2, add an appropriate amount of deionized water to the reactor, then add the remaining nonionic emulsifier and anionic emulsifier, stir and heat to 80-88° C. under nitrogen protection; first add 1 / 30-1 / 10 of the pre-emulsion to the reactor, then add 1 / 3-2 / 3 of the initiator, and keep the reaction at 83-86° C. for 10-30 minutes; S3, adding the remaining pre-emulsion and the remaining initiator dropwise for 200 to 300 minutes, and then keeping the temperature at 83 to 86° C. for 30 to 60 minutes; S4, cooling to below 75°C, and simultaneously dropping the oxidant and the reductant into the reaction kettle for post-elimination reaction, the dropping time lasting 20 to 40 minutes; after the dropping is completed, keeping the temperature at 65 to 75°C for 30 to 60 minutes; S5, cooling to below 40° C., adding the pH adjuster to adjust the pH value to 7-8; and then sequentially adding the adipic acid dihydrazide and the preservative; S6, adjust the solid content to 40.0%-44.0% with the remaining deionized water, filter and discharge the material after passing the test to obtain a water-based acrylic emulsion.

6. The production method according to claim 5, characterized in that The 4-cup coating viscosity of the aqueous acrylic emulsion at 25° C. is 15 to 35 seconds.

7. The production method according to claim 5, characterized in that: The pH adjuster should be added slowly and stopped immediately when the pH value reaches 7-8.

8. The production method according to claim 5, characterized in that: The oxidant, the reducing agent and the preservative should all be dissolved in deionized water to form a solution before use.

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