A water-based hydroxy acrylic acid dispersion, its preparation method and application

Abstract

This invention discloses an aqueous hydroxy acrylic dispersion, its preparation method, and its applications. The aqueous hydroxy acrylic dispersion of this invention is made from the following raw materials in parts by weight: soft monomer: 10-40 parts; hard monomer: 10-40 parts; hydroxyl-containing monomer: 10-20 parts; carboxyl-containing monomer: 4-6 parts; caprolactone-modified acrylate and / or caprolactone-modified methacrylate: 5-10 parts; chain transfer agent: 2-3 parts; initiator: 2-4 parts; neutralizing agent: 2-3 parts; organic solvent: 30-50 parts; water: 115-135 parts. The aqueous hydroxy acrylic dispersion of this invention, after film formation, achieves both high flexibility and excellent scratch resistance, extending the service life of the film. Furthermore, the film exhibits advantages such as fast drying speed, high gloss, strong adhesion, and good weather resistance, making it suitable for large-scale industrial applications.

Description

Technical Field

[0001] This invention relates to the field of synthetic resin materials technology, specifically to an aqueous hydroxy acrylic dispersion, its preparation method, and its application. Background Technology

[0002] Surface coatings used in rail transit and construction machinery often face scratches caused by wind, sand, rain, and various human factors during practical applications, which can easily damage the coatings. Damaged surface coatings not only affect the aesthetics but also expose the steel structure of the machinery to direct air exposure, further leading to corrosion problems. Therefore, it is necessary to improve the scratch resistance of surface coatings used in rail transit and construction machinery to extend their service life.

[0003] Waterborne hydroxyacrylic acid dispersions are an important type of coating resin. Compared to solvent-based hydroxyacrylic acid dispersions, they have lower VOC content while possessing comparable or even better overall performance. Furthermore, hydroxyacrylic acid dispersions are easily chemically modified, allowing for the targeted introduction of specific groups or structures to enhance certain properties or aspects depending on the application. Therefore, waterborne hydroxyacrylic acid dispersions have been extensively researched and applied in recent decades. However, coatings made from existing waterborne hydroxyacrylic acid dispersions exhibit poor scratch resistance, are easily damaged by scratches, and have a short service life, making it difficult to fully meet practical application requirements.

[0004] Currently, the main method to improve the scratch resistance of acrylic resin films is through organosilicon modification (for example, CN 113072851 A discloses a scratch-resistant self-cleaning silicone PU topcoat and its preparation method, which improves the scratch resistance of the film by mixing silicone-modified resin with conventional resin in a certain proportion; CN113928034 A discloses a method for making scratch-resistant heat transfer ribbons, which improves the scratch resistance of the film by adding organosiloxane monomers to modify hydroxyl acrylic resin; CN 105348958 A discloses a two-component organic-inorganic hybrid waterborne matte topcoat varnish and its preparation and application methods, wherein the main component of component B is organosiloxane, and the wear resistance of the prepared film is greatly improved). However, while the introduction of silicon greatly improves the scratch resistance of the resin-modified coating film, coatings made from silicon-modified resins or silicon-containing coatings often suffer from poor adhesion to the substrate, poor resistance to organic solvents, insufficient mechanical strength at high temperatures, and poor flexibility. Furthermore, research has found that appropriately increasing the hydroxyl value of the hydroxyl acrylic dispersion can improve the scratch resistance of the resin-modified coating film (increasing the hydroxyl value helps increase the crosslinking density between the hydroxyl acrylic dispersion and the isocyanate curing agent, resulting in a denser resin film surface and improved scratch resistance). However, increasing the hydroxyl content in the resin also leads to an increase in the film's hardness, which inevitably reduces its flexibility, making it difficult to achieve both high flexibility and excellent scratch resistance.

[0005] Therefore, it is of great significance to develop a waterborne hydroxy acrylic dispersion that can achieve both high flexibility and excellent scratch resistance in the coating film after film formation. Summary of the Invention

[0006] The purpose of this invention is to provide an aqueous hydroxy acrylic acid dispersion, its preparation method, and its application.

[0007] The technical solution adopted in this invention is:

[0008] An aqueous hydroxyacrylic acid dispersion, which is made from the following raw materials in parts by weight:

[0009] Soft monomer: 10 to 40 parts;

[0010] Hard monomer: 10 to 40 parts;

[0011] Hydroxyl monomer: 10 to 20 parts;

[0012] Carboxyl-containing monomers: 4 to 6 parts;

[0013] Caprolactone-modified acrylates and / or caprolactone-modified methacrylates: 5 to 10 parts;

[0014] Chain transfer agent: 2 to 3 parts;

[0015] Initiator: 2 to 4 parts;

[0016] Neutralizing agent: 2 to 3 parts;

[0017] Organic solvent: 30 to 50 parts;

[0018] Water: 115 to 140 parts.

[0019] Preferably, an aqueous hydroxyacrylic acid dispersion is made from the following raw materials in parts by weight:

[0020] Soft monomer: 30 to 40 parts;

[0021] Hard monomer: 35 to 40 parts;

[0022] Hydroxyl monomer: 10 to 15 parts;

[0023] Carboxyl-containing monomers: 4 to 6 parts;

[0024] Caprolactone-modified acrylates and / or caprolactone-modified methacrylates: 5 to 10 parts;

[0025] Chain transfer agent: 2 to 3 parts;

[0026] Initiator: 2 to 4 parts;

[0027] Neutralizing agent: 2 to 3 parts;

[0028] Organic solvent: 30 to 50 parts;

[0029] Water: 115 to 140 parts.

[0030] Preferably, the soft monomer is at least one of butyl acrylate and isooctyl acrylate.

[0031] Preferably, the hard monomer is at least one selected from styrene, methyl methacrylate, and isobornyl methacrylate.

[0032] Preferably, the hydroxyl-containing monomer is at least one selected from hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, and hydroxypropyl methacrylate.

[0033] Preferably, the carboxyl-containing monomer is at least one of acrylic acid and methacrylic acid.

[0034] Preferably, the structural formula of the caprolactone-modified acrylate is: In the formula, n = 1 or 2.

[0035] Preferably, the structural formula of the caprolactone-modified methacrylate is: In the formula, n = 1 or 2.

[0036] Preferably, the chain transfer agent is at least one of β-mercaptoethanol and dodecathiol.

[0037] Preferably, the initiator is at least one selected from 2,2-azobisisobutyronitrile, benzoyl peroxide, tert-butyl peroxide-2-ethylhexanoate, and tert-amyl peroxide-2-ethylhexanoate.

[0038] Preferably, the neutralizing agent is at least one of N,N-dimethylethanolamine and triethylamine.

[0039] Preferably, the organic solvent is at least one selected from propylene glycol methyl ether, dipropylene glycol methyl ether, propylene glycol butyl ether, and diethylene glycol butyl ether.

[0040] A method for preparing an aqueous hydroxyacrylic acid dispersion as described above includes the following steps:

[0041] 1) Mix the soft monomer, hard monomer, hydroxyl-containing monomer, carboxyl-containing monomer, caprolactone-modified acrylate or / and caprolactone-modified methacrylate, chain transfer agent and a portion of the initiator evenly to obtain a mixed liquid.

[0042] 2) Add a portion of the organic solvent to the reactor and purge with protective gas. Then heat the reactor to 72℃~78℃ and turn on the stirrer. Add a portion of the mixed liquid to react and obtain the initial product I.

[0043] 3) Add the remaining mixture to the initial product I for reaction to obtain the initial product II;

[0044] 4) Add the remaining organic solvent and the remaining initiator to the initial product II to react and obtain the initial product III;

[0045] 5) Add the neutralizing agent to the initial product III of the reaction to maintain the pH value of the system at 7-9, and then add water to disperse it to obtain the aqueous hydroxy acrylic dispersion.

[0046] Preferably, in step 1), the amount of initiator added accounts for 85% to 95% of the total mass of the initiator.

[0047] Preferably, the amount of organic solvent added in step 2) is 60% to 70% of the total mass of the organic solvent.

[0048] Preferably, the protective gas in step 2) is nitrogen.

[0049] Preferably, the stirring speed of the stirrer in step 2) is 250 r / min to 350 r / min.

[0050] Preferably, the amount of the mixed liquid added in step 2) is 30% to 35% of the total mass of the mixed liquid.

[0051] Preferably, the reaction time in step 2) is 50 min to 70 min.

[0052] Preferably, the mixture in step 3) is added by dripping for 3.5h to 4.5h.

[0053] Preferably, the reaction time in step 4) is 50 min to 70 min.

[0054] Preferably, the dispersion method in step 5) is mechanical stirring, with the stirring speed of the stirrer being 2500 r / min to 3500 r / min and the stirring time being 5 min to 10 min.

[0055] A coating comprising the above-mentioned aqueous hydroxy acrylic dispersion.

[0056] Preferably, the coating is a polyurethane coating.

[0057] The principle of this invention:

[0058] When the hydroxyl content in the hydroxyl acrylic dispersion is too low, the crosslinking density of the paint film formed after formulation into polyurethane coating is too low, resulting in poor hardness and scratch resistance of the paint film, as well as poor resistance to organic solvents (e.g., swelling in acetone or methyl ethyl ketone). If the hydroxyl content in the hydroxyl acrylic dispersion is too high, the amount of crosslinking agent needs to be increased (e.g., blocked isocyanate). After anionization with the hydroxyl acrylic dispersion, the co-deposition during electrophoresis decreases, and while the hydroxyl value increases, the viscosity of the hydroxyl acrylic dispersion also increases, resulting in decreased smoothness and decorative properties of the paint film, making the paint film brittle and less flexible, and may even lead to increased hydrophilicity of the paint film.

[0059] To address the aforementioned issues, this invention introduces caprolactone-modified acrylates and / or caprolactone-modified methacrylates to modify the hydroxyl acrylic dispersion. These monomers contain highly reactive primary hydroxyl groups. By reducing the amount of traditional hydroxyl functional monomers (e.g., hydroxyethyl methacrylate, hydroxyethyl acrylate, etc.), the goal of increasing hydroxyl content without affecting the film's flexibility can be achieved. This is because caprolactone-modified acrylates and caprolactone-modified methacrylates have longer molecular chains than typical hydroxyl functional monomers, ensuring both increased hydroxyl content and improved flexibility, thereby enhancing the scratch resistance of the film.

[0060] The beneficial effects of the present invention are: the water-based hydroxy acrylic dispersion of the present invention can form a film that combines high flexibility and excellent scratch resistance, which can extend the service life of the film. In addition, the film also has the advantages of fast drying speed, high gloss, strong adhesion and good weather resistance, making it suitable for large-scale industrial application.

[0061] Specifically:

[0062] 1) This invention uses caprolactone-modified acrylate or / and caprolactone-modified methacrylate to modify hydroxyl acrylic resin. By introducing this highly flexible, hydroxyl-containing acrylate monomer, not only can the flexibility of the paint film after the hydroxyl acrylic resin is formed be improved, but the crosslinking density between the hydroxyl acrylic resin and the isocyanate curing agent can also be increased, thereby improving the scratch resistance of the paint film after the waterborne hydroxyl acrylic dispersion is formed.

[0063] 2) This invention uses caprolactone-modified acrylate and / or caprolactone-modified methacrylate to modify hydroxyl acrylic resin. The caprolactone-modified acrylate and caprolactone-modified methacrylate are long-chain monomers, and their molecular chains contain a hydroxyl group. When these monomers are polymerized into the hydroxyl acrylic dispersion, their flexibility and hydroxyl value can be improved, and a good balance can be achieved between the two. This can improve the scratch resistance of the coating film after the waterborne hydroxyl acrylic dispersion is formed and extend the service life of the coating film.

[0064] 3) This invention uses caprolactone-modified acrylate and / or caprolactone-modified methacrylate to modify hydroxyl acrylic resin. The monomer contains highly reactive primary hydroxyl groups. Therefore, the amount of traditional hydroxyl functional monomers (e.g., hydroxyethyl methacrylate, hydroxyethyl acrylate, etc.) added can be reduced to increase the hydroxyl content without affecting the flexibility of the paint film. The caprolactone-modified acrylate and caprolactone-modified methacrylate have longer molecular chains than general monomers, which increases the hydroxyl content while ensuring flexibility, thereby improving the flexibility and scratch resistance of the paint film.

[0065] 4) The paint film made from the water-based hydroxy acrylic dispersion of the present invention has the advantages of fast drying speed, high gloss, strong adhesion and good weather resistance. In addition, the paint film has high flexibility and excellent scratch resistance, long service life and is suitable for large-scale industrial application. Detailed Implementation

[0066] The present invention will be further explained and described below with reference to specific embodiments.

[0067] Example 1:

[0068] An aqueous hydroxyacrylic acid dispersion, the raw material composition of which is shown in the table below:

[0069] Table 1. Raw material composition of an aqueous hydroxyacrylic acid dispersion.

[0070] Soft monomer: butyl acrylate 36 Hard monomer: methyl methacrylate 38 Hydroxyl monomer: Hydroxyethyl methacrylate 15 Carboxyl-containing monomer: methacrylic acid 6 Caprolactone-modified acrylate 5 Chain transfer agent: β-mercaptoethanol 2 Initiator: 2,2-Azobisisobutyronitrile 3 Neutralizing agent: N,N-dimethylethanolamine 3 Organic solvent: propylene glycol butyl ether 30 Deionized water 132

[0071] Note:

[0072] The structural formula of caprolactone-modified acrylate is: (Purchased from Daicel Japan).

[0073] The preparation method of the above-mentioned aqueous hydroxyacrylic acid dispersion is as follows:

[0074] 1) Mix the soft monomer, hard monomer, hydroxyl-containing monomer, carboxyl-containing monomer, caprolactone-modified acrylate, chain transfer agent and 9 / 10 of the initiator evenly to obtain a mixed liquid;

[0075] 2) Add 2 / 3 of the organic solvent to the reaction vessel and purge with nitrogen. Then heat the vessel to 75°C in a water bath and turn on the stirrer. Set the stirrer speed to 300 r / min. Slowly add 1 / 3 of the mixture and keep it at the temperature for 1 hour to obtain the initial product I.

[0076] 3) The remaining mixture is added dropwise to the initial product I using a peristaltic pump, and the dropping time is controlled to be 4 hours to obtain the initial product II.

[0077] 4) Add the remaining organic solvent and the remaining initiator to the initial product II of the reaction, keep warm for 1 hour, and obtain the initial product III of the reaction;

[0078] 5) Add the neutralizing agent to the initial product III of the reaction, keep warm for 0.5 h, maintain the pH of the system at 7-9, then add deionized water and stir and disperse for 10 min with a high-speed disperser at a speed of 3000 r / min to obtain the water-based hydroxy acrylic dispersion (milky white).

[0079] Example 2:

[0080] An aqueous hydroxyacrylic acid dispersion, the raw material composition of which is shown in the table below:

[0081] Table 2. Raw material composition of an aqueous hydroxyacrylic acid dispersion.

[0082]

[0083]

[0084] Note:

[0085] The structural formula of caprolactone-modified acrylate is: (Purchased from Daicel Japan).

[0086] The preparation method of the above-mentioned aqueous hydroxyacrylic acid dispersion is as follows:

[0087] 1) Mix the soft monomer, hard monomer, hydroxyl-containing monomer, carboxyl-containing monomer, caprolactone-modified acrylate, chain transfer agent and 9 / 10 of the initiator evenly to obtain a mixed liquid;

[0088] 2) Add 2 / 3 of the organic solvent to the reaction vessel and purge with nitrogen. Then heat the vessel to 75°C in a water bath and turn on the stirrer. Set the stirrer speed to 300 r / min. Slowly add 1 / 3 of the mixture and keep it at the temperature for 1 hour to obtain the initial product I.

[0089] 3) The remaining mixture is added dropwise to the initial product I using a peristaltic pump, and the dropping time is controlled to be 4 hours to obtain the initial product II.

[0090] 4) Add the remaining organic solvent and the remaining initiator to the initial product II of the reaction, keep warm for 1 hour, and obtain the initial product III of the reaction;

[0091] 5) Add the neutralizing agent to the initial product III of the reaction, keep warm for 0.5 h, maintain the pH of the system at 7-9, then add deionized water and stir and disperse for 10 min with a high-speed disperser at a speed of 3000 r / min to obtain the water-based hydroxy acrylic dispersion (milky white).

[0092] Example 3:

[0093] An aqueous hydroxyacrylic acid dispersion, the raw material composition of which is shown in the table below:

[0094] Table 3. Raw material composition of an aqueous hydroxyacrylic acid dispersion.

[0095]

[0096]

[0097] Note:

[0098] The structural formula of caprolactone-modified methacrylate is: (Purchased from Daicel Japan).

[0099] The preparation method of the above-mentioned aqueous hydroxyacrylic acid dispersion is as follows:

[0100] 1) Mix the soft monomer, hard monomer, hydroxyl-containing monomer, carboxyl-containing monomer, caprolactone-modified methacrylate, chain transfer agent and 9 / 10 of the initiator evenly to obtain a mixed liquid;

[0101] 2) Add 2 / 3 of the organic solvent to the reaction vessel and purge with nitrogen. Then heat the vessel to 75°C in a water bath and turn on the stirrer. Set the stirrer speed to 300 r / min. Slowly add 1 / 3 of the mixture and keep it at the temperature for 1 hour to obtain the initial product I.

[0102] 3) The remaining mixture is added dropwise to the initial product I using a peristaltic pump, and the dropping time is controlled to be 4 hours to obtain the initial product II.

[0103] 4) Add the remaining organic solvent and the remaining initiator to the initial product II of the reaction, keep warm for 1 hour, and obtain the initial product III of the reaction;

[0104] 5) Add the neutralizing agent to the initial product III of the reaction, keep warm for 0.5 h, maintain the pH of the system at 7-9, then add deionized water and stir and disperse for 10 min with a high-speed disperser at a speed of 3000 r / min to obtain the water-based hydroxy acrylic dispersion (milky white).

[0105] Example 4:

[0106] An aqueous hydroxyacrylic acid dispersion, the raw material composition of which is shown in the table below:

[0107] Table 4. Raw material composition of an aqueous hydroxyacrylic acid dispersion.

[0108]

[0109]

[0110] Note:

[0111] The structural formula of caprolactone-modified methacrylate is: (Purchased from Daicel Japan).

[0112] The preparation method of the above-mentioned aqueous hydroxyacrylic acid dispersion is as follows:

[0113] 1) Mix the soft monomer, hard monomer, hydroxyl-containing monomer, carboxyl-containing monomer, caprolactone-modified methacrylate, chain transfer agent and 9 / 10 of the initiator evenly to obtain a mixed liquid;

[0114] 2) Add 2 / 3 of the organic solvent to the reaction vessel and purge with nitrogen. Then heat the vessel to 75°C in a water bath and turn on the stirrer. Set the stirrer speed to 300 r / min. Slowly add 1 / 3 of the mixture and keep it at the temperature for 1 hour to obtain the initial product I.

[0115] 3) The remaining mixture is added dropwise to the initial product I using a peristaltic pump, and the dropping time is controlled to be 4 hours to obtain the initial product II.

[0116] 4) Add the remaining organic solvent and the remaining initiator to the initial product II of the reaction, keep warm for 1 hour, and obtain the initial product III of the reaction;

[0117] 5) Add the neutralizing agent to the initial product III of the reaction, keep warm for 0.5 h, maintain the pH of the system at 7-9, then add deionized water and stir and disperse for 10 min with a high-speed disperser at a speed of 3000 r / min to obtain the water-based hydroxy acrylic dispersion (milky white).

[0118] Example 5:

[0119] An aqueous hydroxyacrylic acid dispersion, the raw material composition of which is shown in the table below:

[0120] Table 5. Raw material composition of an aqueous hydroxyacrylic acid dispersion.

[0121]

[0122] Note:

[0123] The structural formula of caprolactone-modified acrylate is: (Purchased from Daicel Japan).

[0124] The preparation method of the above-mentioned aqueous hydroxyacrylic acid dispersion is as follows:

[0125] 1) Mix the soft monomer, hard monomer, hydroxyl-containing monomer, carboxyl-containing monomer, caprolactone-modified acrylate, chain transfer agent and 9 / 10 of the initiator evenly to obtain a mixed liquid;

[0126] 2) Add 2 / 3 of the organic solvent to the reaction vessel and purge with nitrogen. Then heat the vessel to 75°C in a water bath and turn on the stirrer. Set the stirrer speed to 300 r / min. Slowly add 1 / 3 of the mixture and keep it at the temperature for 1 hour to obtain the initial product I.

[0127] 3) The remaining mixture is added dropwise to the initial product I using a peristaltic pump, and the dropping time is controlled to be 4 hours to obtain the initial product II.

[0128] 4) Add the remaining organic solvent and the remaining initiator to the initial product II of the reaction, keep warm for 1 hour, and obtain the initial product III of the reaction;

[0129] 5) Add the neutralizing agent to the initial product III of the reaction, keep warm for 0.5 h, maintain the pH of the system at 7-9, then add deionized water and stir and disperse for 10 min with a high-speed disperser at a speed of 3000 r / min to obtain the water-based hydroxy acrylic dispersion (milky white).

[0130] Comparative Example 1: (Acrylates / methacrylates without caprolactone modification)

[0131] An aqueous hydroxyacrylic acid dispersion, the raw material composition of which is shown in the table below:

[0132] Table 6. Raw material composition of an aqueous hydroxyacrylic acid dispersion.

[0133] Soft monomer: butyl acrylate 40 Hard monomer: methyl methacrylate 40 Hydroxyl monomer: Hydroxyethyl methacrylate 14 Carboxyl-containing monomer: methacrylic acid 6 Chain transfer agent: β-mercaptoethanol 2 Initiator: 2,2-Azobisisobutyronitrile 3 Neutralizing agent: N,N-dimethylethanolamine 3 Organic solvent: propylene glycol butyl ether 30 Deionized water 132

[0134] The preparation method of the above-mentioned aqueous hydroxyacrylic acid dispersion is as follows:

[0135] 1) Mix the soft monomer, hard monomer, hydroxyl-containing monomer, carboxyl-containing monomer, chain transfer agent and 9 / 10 of the initiator evenly to obtain a mixed liquid;

[0136] 2) Add 2 / 3 of the organic solvent to the reaction vessel and purge with nitrogen. Then heat the vessel to 75°C in a water bath and turn on the stirrer. Set the stirrer speed to 300 r / min. Slowly add 1 / 3 of the mixture and keep it at the temperature for 1 hour to obtain the initial product I.

[0137] 3) The remaining mixture is added dropwise to the initial product I using a peristaltic pump, and the dropping time is controlled to be 4 hours to obtain the initial product II.

[0138] 4) Add the remaining organic solvent and the remaining initiator to the initial product II of the reaction, keep warm for 1 hour, and obtain the initial product III of the reaction;

[0139] 5) Add the neutralizing agent to the initial product III of the reaction, keep warm for 0.5 h, maintain the pH of the system at 7-9, then add deionized water and stir and disperse for 10 min with a high-speed disperser at a speed of 3000 r / min to obtain the water-based hydroxy acrylic dispersion (milky white).

[0140] Comparative Example 2:

[0141] Hydroxyacrylate dispersion A2470: Covestro.

[0142] Performance testing:

[0143] The waterborne hydroxy acrylic dispersions of Examples 1-5, the waterborne hydroxy acrylic dispersion of Comparative Example 1, and the hydroxy acrylic dispersion A2470 of Comparative Example 2 were respectively formulated with waterborne isocyanate curing agent XP 2655 (Covestro) at a molar ratio of NCO:OH of 1.5:1 to prepare polyurethane coatings. After being re-formed into boards (tinplate), the performance of the coating film was tested according to the requirements of "ISO 20566-2020 Paints and varnishes - Laboratory automotive washing method for determination of scrub resistance of coating systems". The test results were in accordance with ISO standards. The following tests were conducted to compare the gloss levels of the unwashed board (A1), the board after washing with a silica suspension (average particle size of 24 μm, concentration of 1.50 g / L ± 0.05 g / L), the board after washing with a silica suspension (20° gloss retention rate C1), the board after baking at 60°C for 2 hours and washing with a silica suspension (20° gloss retention rate E1). After the test panels were treated with ultraviolet xenon lamps for 1000 hours according to GB / T14522-2008, the following tests were conducted: 20° gloss (A2) of the unwashed panel; 20° gloss (B2) of the panel after washing with silica suspension; 20° gloss retention rate (C2) of the panel after washing with silica suspension; 20° gloss (D2) of the panel after baking at 60℃ for 2 hours and washing with silica suspension; and 20° gloss retention rate (E2) of the panel after baking at 60℃ for 2 hours and washing with silica suspension. The film flexibility (F) was also tested according to GB / T 1731-1993. The specific test results are shown in the table below.

[0144] Table 7 Results of gloss and flexibility tests on paint film

[0145]

[0146]

[0147] As shown in Table 7:

[0148] 1) Compared with the aqueous hydroxy acrylic dispersion of Comparative Example 1 (without caprolactone-modified acrylate / methacrylate), the aqueous hydroxy acrylic dispersions of Examples 1-3, due to the addition of 5 parts by mass of caprolactone-modified acrylate / methacrylate, have significantly improved the scratch resistance of the polyurethane coating film after film formation, and the flexibility is increased to 1 mm. The gloss after scratching can reach the level that the coating formulated with Covestro's hydroxy acrylic dispersion A2470 (Comparative Example 2) can achieve.

[0149] 2) In Examples 4 and 5, after increasing the amount of caprolactone-modified acrylate / methacrylate to 10 parts by mass, the scratch resistance of the polyurethane coating film after film formation was further improved, which was superior to the coating formulated with Covestro's hydroxyl acrylic dispersion A2470 (Comparative Example 2).

[0150] 3) The polyurethane coatings made from the waterborne hydroxy acrylic dispersions of Examples 4-5, without undergoing UV-Xenon lamp testing, can achieve a gloss retention rate of over 80% at a 20° angle after wiping in the rail transit and automotive repair fields. The gloss retention rate at a 20° angle after 1000 hours of UV-Xenon lamp testing is about 12% higher than that of the polyurethane coatings made from Covestro's hydroxy acrylic dispersion A2470.

[0151] In summary, the polyurethane coating formulated with the waterborne hydroxy acrylic dispersion of the present invention exhibits excellent flexibility and scratch resistance after film formation.

[0152] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. An aqueous hydroxyacrylic acid dispersion, characterized in that, Made from the following parts by weight of raw materials: Soft monomer: 10 to 40 parts; Hard monomer: 10 to 40 parts; Hydroxyl monomer: 10 to 20 parts; Carboxyl-containing monomers: 4 to 6 parts; Caprolactone-modified acrylates and / or caprolactone-modified methacrylates: 5 to 10 parts; Chain transfer agent: 2 to 3 parts; Initiator: 2 to 4 parts; Neutralizing agent: 2 to 3 parts; Organic solvent: 30 to 50 parts; Water: 115 to 140 parts; The soft monomer is at least one of butyl acrylate and isooctyl acrylate; The hard monomer is at least one of styrene, methyl methacrylate, and isobornyl methacrylate; The hydroxyl-containing monomer is at least one of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, and hydroxypropyl methacrylate. The carboxyl-containing monomer is at least one of acrylic acid and methacrylic acid; The structural formula of the caprolactone-modified acrylate is: In the formula, n = 1 or 2; The structural formula of the caprolactone-modified methacrylate is: In the formula, n = 1 or 2; The aqueous hydroxyacrylic acid dispersion is prepared by a method comprising the following steps: 1) Mix the soft monomer, hard monomer, hydroxyl-containing monomer, carboxyl-containing monomer, caprolactone-modified acrylate or / and caprolactone-modified methacrylate, chain transfer agent and a portion of the initiator evenly to obtain a mixed liquid. 2) Add a portion of the organic solvent to the reactor and purge with protective gas. Then heat the reactor to 72℃~78℃ and turn on the stirrer. Add a portion of the mixed liquid to react and obtain the initial product I. 3) Add the remaining mixture to the initial product I for reaction to obtain the initial product II; 4) Add the remaining organic solvent and the remaining initiator to the initial product II to react and obtain the initial product III; 5) Add the neutralizing agent to the initial product III of the reaction to maintain the pH value of the system at 7-9, and then add water to disperse it to obtain the aqueous hydroxy acrylic dispersion.

2. The aqueous hydroxy acrylic acid dispersion according to claim 1, characterized in that: The chain transfer agent is at least one of β-mercaptoethanol and dodecathionol; the initiator is at least one of 2,2-azobisisobutyronitrile, benzoyl peroxide, tert-butyl peroxide-2-ethylhexanoate, and tert-amyl peroxide-2-ethylhexanoate; and the neutralizing agent is at least one of N,N-dimethylethanolamine and triethylamine.

3. The aqueous hydroxy acrylic acid dispersion according to claim 1, characterized in that: The organic solvent is at least one of propylene glycol methyl ether, dipropylene glycol methyl ether, propylene glycol butyl ether, and diethylene glycol butyl ether.

4. A coating, characterized in that, It comprises the aqueous hydroxy acrylic dispersion according to any one of claims 1 to 3.

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