Hydroxyl acrylic latex capable of being used for preparing high-gloss paint film as well as preparation and application of hydroxyl acrylic latex

Abstract

The invention relates to a hydroxy acrylic latex for preparing a high-gloss paint film as well as preparation and application of the hydroxy acrylic latex. The hydroxy acrylic latex comprises the following raw material components in parts by weight: 10-20 parts of a hydroxypropyl secondary dispersion; 2.5 to 8 parts of alpha, beta-monoolefinic unsaturated monocarboxylic acid; 20 to 60 parts of an ester of an alpha, beta-monoolefinic unsaturated monocarboxylic acid; 5-20 parts of a vinyl aromatic compound; 5-30 parts of hydroxyalkyl (meth) acrylate; 2-4 parts of a chain transfer agent; 40 to 80 parts of deionized water; 0.3 to 1 part of an initiator; and a neutralizing agent. Compared with the prior art, the hydroxyl acrylic latex prepared by the invention combines the advantages of the hydroxyl acrylic latex and the hydroxyl acrylic dispersion, and the waterborne two-component polyurethane coating prepared after the hydroxyl acrylic latex is combined with the hydrophilic modified isocyanate curing agent is high in drying speed, high in paint film glossiness, good in tolerance, high in gloss and excellent in comprehensive performance.

Description

Technical Field

[0001] The invention belongs to the technical field of coatings and relates to a hydroxy acrylic latex which can be used for preparing a high-gloss paint film and the preparation and application thereof. Background Art

[0002] Waterborne (hydroxy) acrylic resin has become one of the research hotspots in the field of waterborne industrial coatings due to its excellent weather resistance, decorative and mechanical properties, and is widely used in the fields of corrosion protection and weather resistance. Waterborne (hydroxy) acrylic resin is often used with isocyanate curing agent to prepare waterborne two-component polyurethane coating (2K-WPU). The cured paint film has the characteristics of both acrylic and polyurethane, with excellent performance and outstanding resistance. Waterborne hydroxy acrylic resin can be divided into waterborne hydroxy acrylic latex and waterborne hydroxy acrylic dispersion.

[0003] Hydroxylated acrylic latex has the advantages of fast drying time, good construction performance, good resistance, low VOC, and high cost performance. At the same time, due to the unique polymerization mechanism of emulsion polymerization, hydroxylated acrylic latex can have the characteristics of high relative molecular weight and low viscosity. However, the emulsifier molecules remain in the polymerization product, which seriously affects the water resistance of the latex film and reduces the mechanical and optical properties of the polymer. Water-based hydroxylated acrylic dispersion has excellent film-forming properties and good gloss and fullness, but the system coating has a long drying time, a short activation period, and poor resistance.

[0004] For example, the preparation method of hydroxy polyacrylate aqueous dispersion disclosed in CN201010605162.X comprises the following steps: (1) mixing carboxylate-containing hydroxy polyacrylate and carboxylate-free hydroxy polyacrylate in a mass ratio of 1:0.1-3, and adding deionized water in an amount of 1-10 times the weight of the carboxylate-containing hydroxy polyacrylate for emulsification; (2) removing the solvent by distillation until the solid content is 40-70%, and adjusting the pH value to 6-8 to obtain the hydroxy polyacrylate aqueous dispersion. The aqueous dispersion of this patent also requires the use of an organic solvent, which is not friendly to the environment and operators. In addition, the prepared paint film is also difficult to balance the drying speed, resistance and high gloss performance.

[0005] Therefore, the preparation of cost-effective water-based resins that take into account drying speed, durability and high gloss is an urgent need in the coatings industry. Summary of the invention

[0006] The purpose of the present invention is to provide a hydroxylated acrylic latex that can be used to prepare a high-gloss paint film and its preparation and application, so as to solve the problem of drying speed, durability and high gloss being difficult to balance.

[0007] The purpose of the present invention can be achieved by the following technical solutions:

[0008] In a first aspect, the present invention provides a hydroxyl acrylic latex that can be used to prepare a high-gloss paint film, comprising the following raw material components in parts by weight:

[0009]

[0010] Neutralizing agent.

[0011] Furthermore, the hydroxypropyl secondary dispersion includes but is not limited to the following commercially available brand products: Shi Quanxing 6233, JJ688, CX-822, Guanzhi PA-3225, PA-4560, PUST-8040, 6242, BLJ-Q370X, DB-3646, CF9470, XT-3223, 5042G, ALQ-20701W, A 2601, Zahn Setaqua 6754, Delun JT-207A, BASF Joncryl 678, Huashi ACR-D6175, etc., preferably 6242, 5042G, A 2601, Zahn Setaqua 6754, Huashi ACR-D6175.

[0012] Furthermore, the α,β-monoethylenically unsaturated monocarboxylic acid is selected from acrylic acid, methacrylic acid, ethylacrylic acid, acryloxypropionic acid, methacryloxypropionic acid, acryloxyacetic acid or methacryloxyacetic acid, and their salts, acid anhydrides and mixtures.

[0013] Still further, the ester of the α,β-monoethylenically unsaturated monocarboxylic acid is selected from the esters of the α,β-monoethylenically unsaturated monocarboxylic acid and C1-C10 alkanols. More preferably, the ester of the α,β-monoethylenically unsaturated monocarboxylic acid is selected from at least one of methyl (meth)acrylate, methyl ethylacrylate, ethyl (meth)acrylate, ethyl ethylacrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, tert-butyl ethylacrylate, n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, n-decyl (meth)acrylate, isooctyl (meth)acrylate. Preferably, methyl (meth)acrylate, n-butyl (meth)acrylate, tert-butyl (meth)acrylate and isooctyl (meth)acrylate are preferred. It should be noted here that the writing of methyl (meth)acrylate means that it covers both methyl acrylate and methyl methacrylate.

[0014] Further, the vinyl aromatic compound is at least one selected from styrene, 2-methylstyrene, 4-methylstyrene, 2-butylstyrene, 4-butylstyrene or 4-decylstyrene, preferably styrene.

[0015] Furthermore, the hydroxyalkyl (meth)acrylate is selected from at least one of hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl methacrylate, hydroxypropyl acrylate or 6-hydroxyhexyl acrylate.

[0016] Further, the chain transfer agent is at least one compound having a mercapto group, preferably tert-butyl mercaptan, alkyl thioglycolate, mercaptoethanol, mercaptopropionic acid, 2-ethylhexyl thioglycolate, mercaptopropyltrimethoxysilane, n-dodecyl mercaptan or tert-dodecyl mercaptan, more preferably alkyl thioglycolate or alkyl ester of mercaptopropionic acid, specifically preferably 2-ethylhexyl thioglycolate or isooctyl mercaptopropionate. Further, the initiator is sodium persulfate, potassium persulfate or ammonium persulfate, preferably ammonium persulfate.

[0017] Furthermore, the neutralizing agent is selected from ammonia water, sodium hydroxide, N,N-dimethylethanolamine or triethylamine, preferably N,N-dimethylethanolamine.

[0018] In a second aspect, the present invention provides a method for preparing a hydroxylated acrylic latex that can be used to prepare a high-gloss paint film, comprising the following steps:

[0019] (1) 50-60% of the hydroxypropylene secondary dispersion is charged into a reaction kettle, and a portion of deionized water is added to obtain a kettle bottom material;

[0020] (2) stirring, dispersing and emulsifying the α,β-monoethylenically unsaturated monocarboxylic acid, the ester of the α,β-monoethylenically unsaturated monocarboxylic acid, the vinyl aromatic compound, the hydroxyalkyl (meth)acrylate, the chain transfer agent, the remaining hydroxypropylene secondary dispersion and deionized water to obtain a pre-emulsion;

[0021] (3) heating the reactor. When the temperature in the reactor reaches 86-89° C., adding 3-5% of the pre-emulsion and part of the initiator to the reactor bottom material, keeping the temperature for one time, and then dropping the remaining pre-emulsion and initiator. After the dropping is completed, keeping the temperature for a second time;

[0022] (4) After the above operation is completed, the obtained product is cooled to below 50° C., the pH value is adjusted to 8.0-9.0 with a neutralizer, and filtered to obtain a hydroxylated acrylic latex.

[0023] Furthermore, in step (3), when the remaining pre-emulsion and initiator are added dropwise, the addition is completed in one go within 3-4 hours;

[0024] Or it is added dropwise in 2-4 steps within 3-4 hours, and each time when the dropping stops, a neutralizing agent is used to adjust the pH of the emulsion system to 7.0-8.0.

[0025] In a third aspect, the present invention provides an application of a hydroxyl acrylic latex that can be used to prepare a high-gloss paint film. The hydroxyl acrylic latex is combined with a hydrophilic modified isocyanate curing agent to form a two-component polyurethane coating, including the following steps

[0026] Furthermore, the two-component polyurethane coating includes the following raw materials in parts by weight:

[0027] Table 1

[0028]

[0029] The titanium white paste in the formula is composed of three components: 75 wt% of R930 titanium dioxide, 17.5 wt% of water; 7.5 wt% of BYK190. The film-forming aid is diethylene glycol butyl ether, the wetting agent is BYK345, and the thickener is WT202. When formulating the two-component paint, there is an important parameter a = -NCO / -OH, that is, the equivalent ratio of the isocyanate group to the hydroxyl group. If -NCO and -OH react completely, the theoretical value of a = 1, but in waterborne coatings, the large amount of water and other groups that may react inevitably consume part of -NCO. Therefore, in two-component waterborne coatings, usually a > 1. Regarding the value of a, the best method is to conduct a gradient experiment in the application system to determine the optimal ratio. The conventional value of a is about between 1.2 and 1.5. Through experiments, the present invention verifies that -NCO / -OH is 1.25:1.

[0030] Even further, the specific preparation process is as follows:

[0031] Mix the hydroxyl acrylic latex, deionized water, titanium dioxide, film-forming aid, wetting agent, and thickener, and disperse them with a disk disperser for 15-25 minutes to obtain a matrix emulsion;

[0032] Mix and dilute the hydrophilic modified isocyanate curing agent according to the ratio of the hydroxyl group (-OH) in the matrix emulsion to the isocyanate group (-NCO) in the hydrophilic modified isocyanate curing agent of 1:1.25, and slowly add it to the matrix emulsion under stirring conditions, and add an appropriate amount of deionized water to adjust to a suitable viscosity to obtain the two-component polyurethane coating.

[0033] Compared with the prior art, the present invention has the following advantages:

[0034] (1) The present invention utilizes the self-emulsifying property of the hydroxypropyl secondary dispersion, uses it as a macromolecular emulsifier during the polymerization of hydroxyacrylic latex, and then through the polymerization of acrylate monomers, obtains a hydroxyacrylic latex with the characteristics of both primary and secondary dispersions. As an emulsifier in latex polymerization, the hydroxypropyl secondary dispersion can effectively increase the solid content of the synthesized system, and the hydroxyl groups therein also increase the reaction sites with isocyanate groups, further improving the crosslinking density and significantly increasing the film hardness and resistance.

[0035] (2) The hydroxyacrylic latex prepared by the present invention combines the advantages of hydroxyacrylic latex and hydroxyacrylic dispersion. The waterborne two-component polyurethane coating prepared by combining with a hydrophilic modified isocyanate curing agent has a fast drying speed, high film gloss, good resistance, high gloss, and excellent comprehensive performance. Specific embodiments

[0036] The present invention will be described in detail below with reference to specific embodiments. These embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operation processes are given, but the protection scope of the present invention is not limited to the following embodiments.

[0037] In the following embodiments, unless otherwise specified for raw materials or treatment techniques, it means that they are all conventional commercially available raw materials or conventional treatment techniques in the art.

[0038] Example 1

[0039] Add 7 g of hydroxypropyl secondary dispersion Huashi ACR-D6175 (solid content 45%, hydroxyl content 3.9%) and 61 g of deionized water to a reaction kettle equipped with a stirrer, a condenser, and a thermometer to prepare the bottom material of the kettle. Stir and emulsify the monomer mixture (22.6 g of methyl methacrylate, 17.4 g of styrene, 12.6 g of butyl acrylate, 16.1 g of 2-hydroxyethyl methacrylate, 5.2 g of acrylic acid, 3.2 g of isooctyl acrylate, 2 g of 2-ethylhexyl mercaptoacetate) with 7 g of aqueous hydroxypropyl secondary dispersion and 40 g of deionized water to prepare a pre-emulsion for standby;

[0040] When the temperature in the reaction kettle reaches 88 ± 1 °C, add 4% of the pre-emulsion and initiator aqueous solution I (0.135 g of ammonium persulfate, 2 g of deionized water) to the bottom material of the kettle, keep warm for 30 min, and then dropwise add the remaining pre-emulsion and initiator aqueous solution II (0.535 g of ammonium persulfate, 10 g of deionized water). The dropping takes 3 h. After the dropping is completed, keep warm for 1 h. After the above operations are completed, cool the latex to below 50 °C, adjust the pH to 8.0 - 9.0 with a neutralizing agent, and filter with a 200-mesh filter to obtain the hydroxyacrylic latex.

[0041] Comparative Example 1

[0042] Preparation of hydroxyacrylic latex

[0043] The aqueous hydroxypropylene secondary dispersion in the bottom of the kettle was replaced with 1.2g of sodium dodecylbenzene sulfonate and 0.4g of ER30, the deionized water in the bottom of the kettle was changed from 61g to 50g, 1.5g of the aqueous hydroxypropylene secondary dispersion in the pre-emulsification step was replaced with 0.8g of sodium dodecylbenzene sulfonate and 0.3g of ER30, methyl methacrylate in the monomer mixture was changed from 15.6g to 25.6g, and butyl acrylate was changed from 9.6g to 14.9g, and the remaining steps were the same as in Example 1, so that the hydroxyl content and solid content in Example 1 were kept consistent with those in Comparative Example 1.

[0044] The hydroxylated acrylic latex (solid content 45%, -OH%: 2.5%) prepared in Example 1 and the hydroxylated acrylic emulsion (solid content 45%, -OH%: 2.5%) prepared in Comparative Example 1 were formulated into paints according to the following method and sprayed on clean tinplate sheets. After drying at room temperature, the paints were placed in an oven at 80°C for 2 hours and the properties of the paint films were measured.

[0045] Preparation method:

[0046] Prepare a base emulsion: 40 parts of water-based hydroxy acrylate latex, 4.5 parts of deionized water, 35 parts of titanium dioxide, 5 parts of film-forming aid diethylene glycol butyl ether, 0.2 parts of wetting agent BYK-345, and 0.3 parts of thickener WT-202 are mixed according to weight parts, and sheared and dispersed for 15 minutes using a shearing machine to obtain a base emulsion; wherein the titanium dioxide is composed of 75wt% R930 titanium dioxide, 17.5wt% water, and 7.5wt% BYK-190;

[0047] Preparation of water-based two-component polyurethane coating: dilute the hydrophilic modified isocyanate curing agent (Bayer XP2655) in a ratio of 1:1.25 between the hydroxyl group (-OH) in the base emulsion and the (-NCO) isocyanate group in the hydrophilic modified isocyanate curing agent at a ratio of 1:1.25, then slowly add it to the base emulsion under stirring, and add an appropriate amount of deionized water to adjust to a suitable viscosity to obtain a two-component polyurethane coating.

[0048] The paint film test methods and standards are shown in Table 2, and the performance results are shown in Table 3.

[0049] Table 2

[0050]

[0051]

[0052] Table 3

[0053]

[0054] As can be seen from the table, under the same solid content and hydroxyl content, the gloss, impact resistance, fullness, pencil hardness and water resistance of the paint film prepared with the water-based hydroxy acrylate microsphere latex in Implementation 1 as the raw material are higher than those of the paint film prepared with the water-based hydroxy acrylate microsphere latex in Comparative Example 1 as the raw material, and the drying speed is also close to the drying speed of the conventional hydroxy acrylic latex, i.e., Comparative Example 1. It can be seen that the use of the secondary dispersion as an emulsifier to synthesize the hydroxy acrylic latex can effectively reduce the problems of low gloss and poor fullness of the latex after film formation caused by the emulsifier. At the same time, since the secondary dispersion itself also contains some hydroxyl groups, it can not only play an emulsifying role during polymerization, but also react with isocyanate during curing, which will not reduce the overall cross-linking degree of the paint film, but also make the cross-linking and curing of the paint film more uniform and dense, thereby improving the hardness of the paint film. The hydroxy acrylic latex prepared by the present invention has good polishing property and long activation period, and basically combines the advantages of high gloss and good fullness of water-based hydroxy acrylic secondary dispersion and good resistance and fast drying speed of hydroxy acrylic latex, and has good application prospects in the field of water-based wood coatings.

[0055] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A hydroxylated acrylic latex for preparing a high gloss paint film, characterized in that: The raw material components include the following parts by weight:

2. The hydroxylated acrylic latex for preparing a high gloss paint film according to claim 1, characterized in that: The α,β-monoethylenically unsaturated monocarboxylic acid is selected from acrylic acid, methacrylic acid, ethacrylic acid, acryloxypropionic acid, methacryloxypropionic acid, acryloxyacetic acid or methacryloxyacetic acid, and salts, anhydrides and mixtures thereof.

3. The hydroxylated acrylic latex for preparing a high gloss paint film according to claim 1, characterized in that: The ester of α,β-monoethylenically unsaturated monocarboxylic acid is selected from esters of α,β-monoethylenically unsaturated monocarboxylic acid and C1-C10 alkanol.

4. The hydroxylated acrylic latex for preparing a high gloss paint film according to claim 3, characterized in that: The ester of the α,β-monoethylenically unsaturated monocarboxylic acid is selected from at least one of methyl (meth)acrylate, methyl ethylacrylate, ethyl (meth)acrylate, ethyl ethylacrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, tert-butyl ethylacrylate, n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, n-decyl (meth)acrylate, and isooctyl (meth)acrylate.

5. The hydroxylated acrylic latex for preparing a high gloss paint film according to claim 1, characterized in that: The vinyl aromatic compound is at least one selected from styrene, 2-methylstyrene, 4-methylstyrene, 2-butylstyrene, 4-butylstyrene or 4-decylstyrene.

6. The hydroxylated acrylic latex for preparing a high gloss paint film according to claim 1, characterized in that: The hydroxyalkyl (meth)acrylate is selected from at least one of hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl methacrylate, hydroxypropyl acrylate, and 6-hydroxyhexyl acrylate.

7. The hydroxylated acrylic latex for preparing a high gloss paint film according to claim 1, characterized in that: The chain transfer agent is at least one compound having a mercapto group, including at least one of tert-butyl mercaptan, alkyl thioglycolate, mercaptoethanol, mercaptopropionic acid, 2-ethylhexyl thioglycolate, mercaptopropyltrimethoxysilane, n-dodecyl mercaptan or tert-dodecyl mercaptan; the initiator is sodium persulfate, potassium persulfate or ammonium persulfate; The neutralizing agent is selected from ammonia water, sodium hydroxide, N,N-dimethylethanolamine or triethylamine.

8. The method for preparing a hydroxylated acrylic latex for preparing a high gloss paint film according to any one of claims 1 to 7, characterized in that: The following steps are involved: (1) 50-60% of the total amount of the hydroxypropylene secondary dispersion is charged into a reaction kettle, and a portion of deionized water is added to obtain a kettle bottom material; (2) stirring, dispersing and emulsifying the α,β-monoethylenically unsaturated monocarboxylic acid, the ester of the α,β-monoethylenically unsaturated monocarboxylic acid, the vinyl aromatic compound, the hydroxyalkyl (meth)acrylate, the chain transfer agent, the remaining hydroxypropylene secondary dispersion and deionized water to obtain a pre-emulsion; (3) heating the reactor. When the temperature in the reactor reaches 86-89° C., adding 3-5% of the pre-emulsion and part of the initiator to the reactor bottom material, keeping the temperature for one time, and then dropping the remaining pre-emulsion and initiator. After the dropping is completed, keeping the temperature for a second time; (4) After the above operation is completed, the obtained product is cooled to below 50° C., the pH value is adjusted to 8.0-9.0 with a neutralizer, and filtered to obtain a hydroxylated acrylic latex.

9. The method for preparing a hydroxylated acrylic latex for preparing a high gloss paint film according to claim 8, characterized in that: In step (3), when the remaining pre-emulsion and initiator are added dropwise, the addition is completed in one go within 3-4 hours; Or the solution may be added dropwise in 2-4 steps within 3-4 hours, and the pH value of the emulsion system may be adjusted to 7.0-8.0 with a neutralizer each time the addition is stopped.

10. The use of the hydroxylated acrylic latex for preparing a high gloss paint film according to any one of claims 1 to 7, characterized in that: The hydroxylated acrylic latex is combined with a hydrophilically modified isocyanate curing agent to form a two-component polyurethane coating.

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