A photocurable aqueous acrylic dispersion and its application

Abstract

The present invention relates to the technical field of coatings, with the classification number IPC C08G18 / 67, and discloses a photocurable aqueous acrylic dispersion and its application. By mass, the raw materials for preparation include: 90 - 170 parts of monomers, 0.1 - 5 parts of molecular weight regulators, 0.5 - 2 parts of initiators, 20 - 30 parts of cosolvents, 20 - 30 parts of solvents, 5 - 20 parts of neutralizing agents, and 0.01 - 1 part of catalysts. Through the compounding of different monomers and the combined action of monomers, neutralizing agents, initiators, and molecular weight regulators, the present invention effectively improves the performance of the photocurable aqueous acrylic dispersion, enabling the prepared photocurable aqueous acrylic coating to have good adhesion, hardness, solvent resistance, and stability.

Description

Technical Field

[0001] The present invention relates to the technical field of coatings, in particular to IPC C08G18 / 67, and more specifically, to a photocurable waterborne acrylic dispersion and its application. Background Art

[0002] Objects such as wood and metal are exposed to the atmosphere and are eroded by oxygen, moisture, etc., resulting in damage phenomena such as rust and wood decay. In order to extend the service life of various materials, coatings are usually applied to the surface of the object to form a certain protective film, which can prevent or delay the occurrence and development of these damage phenomena. Ultraviolet (UV) curable coatings are a new type of environmentally friendly material, especially waterborne UV curable coatings, which can effectively reduce the pollution of VOCs to the environment. Currently, the UV coatings developed on the market have some problems to varying degrees. Among them, although acrylic resins have excellent properties, the adhesion and stability of the coatings are slightly insufficient and need to be further improved.

[0003] In order to solve the above problems, the application document CN202010387587.1 discloses an isocyanate-modified UV monomer and its preparation method. This isocyanate-modified UV monomer, as a bridge between polyurethane resin and acrylic resin, has excellent properties such as light color, fast curing speed, high hardness, and low cost, solves the drawbacks of poor adhesion and impact resistance of acrylic resins, and at the same time has high heat resistance and durability, but does not explore the impact on storage stability.

[0004] The application document CN201910808829.7 discloses a photocurable waterborne coating and its preparation method. This invention uses a reasonable ratio of waterborne acrylic dispersion, modified amino resin, water-dispersible modified isocyanate, photoinitiator, additives, pigments, etc. With the mutual influence and cooperation of each component, the prepared coating has strong adhesion, resistance to film yellowing and chalking, and also has certain antibacterial properties, but the improvement of solvent resistance, stability and hardness is not obvious. Summary of the Invention

[0005] In order to solve the above problems, the present invention effectively improves the performance of the photocurable waterborne acrylic dispersion through the compounding of different monomers and the combined action of monomers, neutralizing agents, initiators, and molecular weight regulators, so that the prepared photocurable waterborne acrylic coating has good adhesion, hardness, solvent resistance and stability.

[0006] A photocurable waterborne acrylic dispersion and its application. By mass, the preparation raw materials include: 70 - 150 parts of monomers, 15 - 30 parts of hydroxy compounds, 0.1 - 5 parts of molecular weight regulators, 0.5 - 2 parts of initiators, 20 - 30 parts of co-solvents, 20 - 30 parts of solvents, 5 - 20 parts of neutralizing agents, and 0.0.1 - 1 part of catalysts.

[0007] Preferably, the monomers include 50-90 parts of acrylate monomers, 10-30 parts of carboxyl-containing monomers, and 30-50 parts of isocyanate monomers.

[0008] More preferably, the acrylate monomers include one or more of hydroxyethyl acrylate, hydroxybutyl acrylate, hydroxypropyl acrylate, methyl methacrylate, hydroxyethyl methacrylate, methyl methacrylate, butyl methacrylate, ethyl acrylate, isooctyl acrylate, lauryl methacrylate, pentaerythritol triacrylate, dipentaerythritol pentaacrylate.

[0009] More preferably, the acrylate monomers include hydroxypropyl methacrylate, methyl methacrylate, lauryl methacrylate, ethyl acrylate, and pentaerythritol triacrylate.

[0010] To increase the crosslinking density of the system, more preferably, the mass ratio of methyl methacrylate, lauryl methacrylate, and ethyl acrylate is (4-6):(1-2):(2-3), adjusting the glass transition temperature and molecular weight of the polymer, controlling the change of free volume, reducing the hindrance of further reaction of some uncrosslinked hydroxyl groups, increasing the crosslinking density of the system, and improving the solvent resistance and water resistance of the coating on the basis of ensuring that the polymer has a certain hardness. More preferably, the mass ratio of methyl methacrylate, lauryl methacrylate, and ethyl acrylate is 5:1:2.

[0011] To improve the compatibility of the system, further optimize, the mass ratio of hydroxypropyl methacrylate and methyl methacrylate is (3-5):(4-6). The hydroxyl content in the system will affect the dispersion of isocyanate in the system. Through the combined action of a specific amount of hydroxypropyl methacrylate and methyl methacrylate, the particle size of the acrylic dispersion is adjusted, the side reaction between isocyanate groups and water is reduced, the stability of the dispersion is effectively improved, and the gloss of the coating film prepared therefrom is relatively high.

[0012] More preferably, the mass ratio of hydroxypropyl methacrylate and methyl methacrylate is 4:5.

[0013] More preferably, the carboxyl-containing monomers include one or more of methacrylic acid, methylene butanedioic acid, and acrylic acid.

[0014] More preferably, the carboxyl-containing monomers include methacrylic acid and methylene butanedioic acid.

[0015] More preferably, the isocyanate monomers include toluene-2,4-diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and diphenylmethane diisocyanate.

[0016] Further preferably, the isocyanate monomer is toluene-2,4-diisocyanate.

[0017] To improve the comprehensive performance of the dispersion, further preferably, the mass ratio of the toluene-2,4-diisocyanate, pentaerythritol triacrylate, and methyl methacrylate is (28-32):(21-23):(22-27). Under the combined action of specific amounts of the three, the film shrinkage is reduced, and local chain segment diffusion is likely to occur at the adhesion interface, improving the adhesion, and enhancing the abrasion resistance and impact resistance.

[0018] Preferably, the hydroxy compound includes one or more of polybutylene glycol, polyethylene glycol, and polypropylene glycol.

[0019] Further preferably, the hydroxy compound is polyethylene glycol.

[0020] Preferably, the molecular weight regulator includes one or more of mercaptoethanol and dodecyl mercaptan.

[0021] Further preferably, the molecular weight regulator is dodecyl mercaptan.

[0022] Preferably, the initiator includes one or more of benzoyl peroxide, tert-amyl peroxy-2-ethylhexanoate, and di-tert-butyl peroxide.

[0023] Further preferably, the initiator is benzoyl peroxide.

[0024] Preferably, the co-solvent includes one or more of propylene glycol methyl ether acetate, ethylene glycol butyl ether, n-butanol, and isopropanol.

[0025] Further preferably, the co-solvent is n-butanol and isopropanol.

[0026] To improve the distribution of hydroxyl groups, further preferably, the mass ratio of the dodecyl mercaptan, benzoyl peroxide, n-butanol, and isopropanol is (1-3):(1-2):(18-22):(9-10). The initiator and the molecular chain regulator act together to adjust the molecular weight and its distribution, making the distribution of hydroxyl groups more uniform, avoiding the absence of hydroxyl groups on small molecular chains, shortening the crosslinking time, and cooperating with the co-solvent to ensure the gloss, hardness of the coating, and improve the surface drying speed.

[0027] Further preferably, the mass ratio of the dodecyl mercaptan, benzoyl peroxide, n-butanol, and isopropanol is 2:1:20:10.

[0028] Preferably, the solvent includes one or more of dipropylene glycol butyl ether, propylene glycol dimethyl ether, diethylene glycol dimethyl ether, and dipropylene glycol dimethyl ether.

[0029] Further preferably, the solvent is dipropylene glycol butyl ether.

[0030] Preferably, the neutralizing agent includes one or more of triethylamine, diethanolamine, dimethylethanolamine, and 1-amino-1-methylpropanol.

[0031] More preferably, the neutralizing agent is dimethylethanolamine.

[0032] To further improve the stability of the dispersion, more preferably, the mass ratio of dimethylethanolamine, methacrylic acid, and methylene succinic acid is (1-2):(1-3):1. A specific amount of carboxyl-containing monomer and neutralizing agent act together to adjust the viscosity of the system and improve compatibility, and avoid poor adhesion caused by too strong hydrophilicity. On the basis of good adhesion, the stability of the dispersion is further improved.

[0033] More preferably, the mass ratio of dimethylethanolamine, methacrylic acid, and methylene succinic acid is 2:2:1.

[0034] Preferably, the catalyst includes one or more of organotin catalysts and amine catalysts.

[0035] More preferably, the catalyst is an organotin catalyst.

[0036] One or more of dibutyltin dilaurate, dimethyltin dilaurate, stannous octoate, dibutyltin oxide, dibutyltin dibutyrate, and dimethyltin dioleate.

[0037] More preferably, the organotin catalyst is dibutyltin dilaurate.

[0038] The second aspect of the present invention provides an application of a photocurable aqueous acrylic dispersion, and the photocurable aqueous acrylic dispersion is applied to a photocurable aqueous acrylic coating.

[0039] Beneficial effects:

[0040] (1) In this application, the mass ratio of methyl methacrylate, lauryl methacrylate, and ethyl acrylate is (4-6):(1-2):(2-3), which improves the solvent resistance and water resistance of the coating while ensuring that the polymer has a certain hardness.

[0041] (2) In this application, the mass ratio of hydroxypropyl methacrylate and methyl methacrylate is (3-5):(4-6), which effectively improves the stability of the dispersion, and the coating film prepared therefrom has a relatively high gloss.

[0042] (3) In this application, the mass ratio of toluene-2,4-diisocyanate, pentaerythritol triacrylate, and methyl methacrylate is (28-32):(21-23):(22-27), which improves adhesion and enhances abrasion resistance and impact resistance.

[0043] (4) In this application, the mass ratio of dodecyl mercaptan, benzoyl peroxide, n-butanol, and isopropanol is (1-3):(1-2):(18-22):(9-10), which ensures the gloss and hardness of the coating and improves the surface drying speed.

[0044] (5) In this application, the mass ratio of dimethylethanolamine, methacrylic acid, and methylene succinic acid is (1-2):(1-3):1, which further improves the stability of the dispersion on the basis of good adhesion. Example

[0045] Example 1

[0046] A photocurable aqueous acrylic dispersion and its application. By mass, the preparation raw materials include: 127 parts of monomer, 20 parts of hydroxyl compound, 2 parts of molecular weight regulator, 1 part of initiator, 30 parts of cosolvent, 20 parts of solvent, 10 parts of neutralizer, and 0.1 part of catalyst.

[0047] By mass, the monomer includes 82 parts of acrylate monomer, 15 parts of carboxyl-containing monomer, and 30 parts of isocyanate monomer.

[0048] By mass, the acrylate monomer is 20 parts of hydroxypropyl methacrylate, 25 parts of methyl methacrylate, 5 parts of lauryl methacrylate, 10 parts of ethyl acrylate, and 22 parts of pentaerythritol triacrylate.

[0049] By mass, the carboxyl-containing monomer is 10 parts of methacrylic acid and 5 parts of methylene succinic acid.

[0050] The methacrylic acid is purchased from Jinan Sane Chemical Co., Ltd.

[0051] By mass, the isocyanate monomer is 30 parts of toluene-2,4-diisocyanate.

[0052] The hydroxyl compound is polyethylene glycol, purchased from Shanghai Lianji Chemical Co., Ltd., model PEG-400.

[0053] The molecular weight regulator is dodecane mercaptan.

[0054] The initiator is benzoyl peroxide.

[0055] By mass, the cosolvent is 20 parts of n-butanol and 10 parts of isopropanol.

[0056] The solvent is dipropylene glycol monobutyl ether.

[0057] The neutralizing agent is dimethylethanolamine.

[0058] The catalyst is dibutyltin dilaurate.

[0059] The preparation method of the photocurable aqueous acrylic dispersion comprises the following steps:

[0060] S1: Mix acrylate monomers, carboxyl-containing monomers, initiators, cosolvents, and molecular weight regulators in the formula amount except for pentaerythritol triacrylate, stir at 600 rpm, heat up to 120 °C, keep the temperature constant for reaction for 6 h, cool to 60 °C, add the formula amount of the neutralizing agent, and continue to stir at a constant temperature for 30 min to obtain an acrylic resin.

[0061] S2: Mix the formula amount of the solvent, isocyanate monomers, hydroxyl compounds, and catalysts, stir at 600 rpm, then add the formula amount of pentaerythritol triacrylate, heat up to 70 °C, keep the temperature constant for reaction for 3 h to obtain an isocyanate intermediate.

[0062] S3: Mix the isocyanate in S2 with the acrylic resin in S1, stir at 600 rpm, heat up to 70 °C, keep the temperature constant for reaction for 3 h. After the reaction is completed, extract and add the solvent with a mass of 80% of the solvent, and add 200 parts by mass of water to obtain the photocurable aqueous acrylic dispersion.

[0063] Example 2

[0064] The specific implementation method is the same as that of Example 1. The difference from Example 1 is that, by mass, the addition amount of methacrylic acid is 12 parts, and the addition amount of methylene succinic acid is 5 parts; the addition amount of methyl methacrylate is 27 parts; the addition amount of lauryl methacrylate is 4 parts, and the addition amount of ethyl acrylate is 10 parts.

[0065] Example 3

[0066] The specific implementation method is the same as that of Example 1. The difference from Example 1 is that the carboxyl monomer is acrylic acid, and by mass, the addition amount of acrylic acid is 10 parts; replace the neutralizing agent dimethylethanolamine with 1-amino-1-methylpropanol, and the addition amount of 1-amino-1-methylpropanol is 12 parts.

[0067] Example 4

[0068] The specific implementation method is the same as that of Example 1. The difference from Example 1 is that replace the molecular weight regulator dodecanethiol with mercaptoethanol, and by mass, the addition amount of mercaptoethanol is 0.1 part.

[0069] Example 5

[0070] The specific implementation manner is the same as that of Example 1. The difference from Example 1 is that, by mass parts, the addition amount of methyl methacrylate is 32 parts, the addition amount of lauryl methacrylate is 5 parts, and the addition amount of ethyl acrylate is 5 parts.

[0071] Performance test

[0072] The photocurable waterborne acrylic dispersions of Examples 1-5 were prepared into photocurable waterborne acrylic coatings. The preparation method comprises the following steps:

[0073] By mass parts, 80 parts of the photocurable waterborne acrylic dispersion, 5 parts of the waterborne reactive diluent, 10 parts of talc powder, 1 part of silica, and 1 part of photoinitiator were mixed and stirred at 600 rpm for 10 min; then defoamer, wetting agent, and pigment were added and stirred for another 5 min to obtain the photocurable waterborne acrylic coating.

[0074] The waterborne reactive diluent is β-hydroxyethyl methacrylate; the photoinitiator is azobisisobutyronitrile; the talc powder is purchased from Guangxi Longsheng Jinbeike New Material Technology Co., Ltd., with the model of 2500# talc powder; the silica is purchased from Shanghai Lingmeng New Material Co., Ltd., with the model of A-360; the defoamer is TEGO Airex 902W, purchased from Dongguan Haoyouduo New Material Co., Ltd.; the wetting agent is BYK346, purchased from Guangzhou Xianrenhui International Trade Co., Ltd.; the pigment is R4254-SI, purchased from Yingde Cody Pigment Technology Co., Ltd.

[0075] The photocurable waterborne acrylic coating prepared by the above method was applied on a clean aluminum plate, and the coating thickness was maintained at 30 μm. The curing time was 2.5 h under the ultraviolet lamp intensity of 30 mW / cm 2 .

[0076] Performance tests on the stability of the photocurable waterborne acrylic coatings prepared from the photocurable waterborne acrylic dispersions of Examples 1-5 were carried out, and performance tests on the hardness and solvent resistance of the cured coatings were carried out. The test results are recorded in Table 1.

[0077] (1) Hardness

[0078] The test standard for the coating hardness was in accordance with GB / T 6739-2006.

[0079] (2) Solvent resistance

[0080] The test method for the solvent resistance of the coating was referred to GB / T 23989-2009. Absorbent cotton was soaked with acetone until it was in a wet state and wiped on the coating. One forward and one backward wipe was regarded as one reciprocating wipe. After the wiping was completed, the exposure of the substrate was observed.

[0081] The number of reciprocating wipes when the substrate is not exposed is denoted as n. n ≥ 100 is excellent; 80 ≤ n < 100 is qualified; n < 80 is unqualified.

[0082] (3) Stability

[0083] For the coating stability test, refer to GB / T 6753.3 - 1986. Store it at a constant temperature of 50 ± 2°C for 30 days, take it out and place it at room temperature (25°C) for 24 hours, and check for skin formation and sedimentation.

[0084] The skin formation area on the coating surface is denoted as s: s = 0, no skin formation; 0 < s ≤ 5, very slight skin formation; 5 < s ≤ 15, slight skin formation; 15 < s ≤ 30, moderate skin formation; 30 < s ≤ 50, relatively severe skin formation; s > 50, severe skin formation.

[0085] The sedimentation situation is scored using six grades of 10, 8, 6, 4, 2, 0, and the scoring evaluation criteria follow GB / T6753.3 - 1986.

[0086] Table 1

[0087]

Claims

1. A photocurable aqueous acrylic dispersion, characterized in that, By mass parts, the preparation raw materials include: 70 - 150 parts of monomer, 15 - 30 parts of hydroxy compound, 0.1 - 5 parts of molecular weight regulator, 0.5 - 2 parts of initiator, 20 - 30 parts of cosolvent, 20 - 30 parts of solvent, 5 - 20 parts of neutralizer, 0.0.1 - 1 part of catalyst; the monomer includes acrylate monomer, carboxyl-containing monomer, isocyanate monomer; the acrylate monomer includes hydroxypropyl methacrylate, methyl methacrylate, lauryl methacrylate, ethyl acrylate, pentaerythritol triacrylate; the mass ratio of methyl methacrylate, lauryl methacrylate, ethyl acrylate is (4 - 6):(1 - 2):(2 - 3); the mass ratio of hydroxypropyl methacrylate, methyl methacrylate is (3 - 5):(4 - 6); the isocyanate monomer is toluene-2,4-diisocyanate, and the mass ratio of toluene-2,4-diisocyanate, pentaerythritol triacrylate, methyl methacrylate is (28 - 32):(21 - 23):(22 - 27); the carboxyl-containing monomer includes methacrylic acid, methylene succinic acid, the neutralizer is dimethylethanolamine, and the mass ratio of the neutralizer, methacrylic acid, methylene succinic acid is (1 - 2):(1 - 3):1; the molecular weight regulator is dodecyl mercaptan, the initiator is benzoyl peroxide, the cosolvent is n-butanol, isopropanol; the mass ratio of the molecular weight regulator, initiator, n-butanol, isopropanol is (1 - 3):(1 - 2):(18 - 22):(9 - 10).

2. Use of the photocurable aqueous acrylic dispersion according to claim 1, characterized in that, The photocurable aqueous acrylic dispersion is applied to the photocurable aqueous acrylic coating.

Images