Acrylic-acid-based high-solid-content single-color finish paint as well as preparation method and application thereof

Abstract

The invention relates to a high-solid-content single-color finish paint based on acrylic acid and a preparation method of the high-solid-content single-color finish paint. The color paste comprises 12-18 parts of high-solid thermosetting hydroxy acrylic resin, 2-4 parts of polyester polyol, 15-25 parts of etherified amino resin, 1-3 parts of a blocked isocyanate cross-linking agent, 12-18 parts of diurea compound modified polyester resin, 0.5-2 parts of an auxiliary agent, 5-10 parts of a solvent, 30-40 parts of white color paste and 0.5-2 parts of color paste with other colors. According to the acrylic acid-based high-solid single-color finish paint, the thermosetting hydroxy acrylic resin, the polyester polyol, the etherified amino resin and the blocked isocyanate cross-linking agent are combined, and the obtained composition has the characteristics that the construction solid content is high (organic solvent volatile matter lt; 420 g / L), has the characteristics of environment friendliness, good mechanical property, excellent appearance and luster and the like, and is suitable for industrial products, especially automobile exterior coating. The invention further discloses a preparation method and application of the high-solid-content single-color finish paint based on the acrylic acid.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of coating technology, in particular, to an acrylic-based high solid monochrome topcoat, and a preparation method and application of the topcoat. BACKGROUND

[0002] With the continuous improvement of the national environmental protection requirements, the influence of coatings on the environment is subject to more and more strict restrictions. In the prior art, the water-based technology of coatings is relatively common in the production of environmentally friendly coatings, but some automobile manufacturers still hope to meet the environmental protection requirements by providing high solid solvent-based products. At the same time, in order to better reduce the negative impact on the environment and improve economic benefits, more and more vehicles use a clear paint-free spraying process, including but not limited to light trucks, heavy trucks, economy cars, etc. This clear paint-free process uses a single colored topcoat layer on the outermost layer of the vehicle to replace the traditional "color paint + clear paint" double coating process, which not only reduces the amount of coatings used in the coating process, improves the process efficiency, but also helps to reduce the VOC emissions of the vehicle manufacturer, and is more environmentally friendly.

[0003] However, there are still many bottlenecks in the existing solvent-based monochrome topcoat technology. Its short-term performance such as stone chip resistance and medium and long-term performance such as chemical resistance and water resistance are all inferior to the coating process containing a clear paint coating. It is also at a disadvantage in appearance such as orange peel (long wave, short wave, and bright reflection), gloss, etc. More notably, the monochrome topcoat products in the prior art almost all have a low solid content, and the amount of solvent used is too much, which has a great adverse impact on the environment.

[0004] Therefore, there is an urgent need in the art to develop an environmentally friendly high solid monochrome topcoat that can reduce VOC emissions while achieving the same level of performance and appearance as the coating process containing a clear paint coating to solve the problems in the prior art. SUMMARY

[0005] Based on the above facts, the purpose of the present application is to provide an acrylic-based high solid monochrome topcoat, which uses a combination of thermosetting hydroxyl acrylic resin, polyester polyol, etherified amino resin, and blocked isocyanate crosslinking agent. The obtained composition has the characteristics of high construction solid content (organic solvent volatiles <420 g / L), environmental friendliness, good mechanical properties, excellent appearance and gloss, etc., and is suitable for industrial products, especially automotive exterior coating. In the description of the present application, "between" is understood to include the end point value, and "above" and "below" are understood to include the number.

[0006] The first aspect of the present application provides an acrylic-based high solid monochrome topcoat, which comprises, by weight:

[0007]

[0008] High solids thermosetting hydroxyl acrylate resin

[0009] In the present invention, the high solids thermosetting hydroxyl acrylic resin is a copolymer of acrylic monomers and other monomers containing carbon-carbon double bonds. Specifically, the high solids thermosetting hydroxyl acrylic resin is a copolymer of acrylic monomers and other monomers containing carbon-carbon double bonds, which is formed by free radical copolymerization in the presence of a high boiling aromatic hydrocarbon solvent S-100 and an initiator. In some preferred embodiments of the present invention, the high solids thermosetting hydroxyl acrylic resin has a number average molecular weight of 3500-5500, a hydroxyl value of 80-150 mg KOH / g, an acid value of 6.5-10.5 mg KOH / g, a glass transition temperature between -10°C and +10°C, and a solids content of 69-71% by weight.

[0010] Acrylic monomers

[0011] In the present invention, the acrylic monomers include, but are not limited to, one or more selected from the group consisting of methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, isopropyl acrylate, isopropyl methacrylate, hydroxypropyl acrylate, n-butyl acrylate, butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, t-butyl acrylate, t-butyl methacrylate, amyl acrylate, amyl methacrylate, hexyl acrylate, hexyl methacrylate, ethylhexyl acrylate, ethylhexyl methacrylate, 3,3,5-trimethylhexyl acrylate, 3,3,5-trimethylhexyl methacrylate, stearyl acrylate, stearyl methacrylate, dodecyl acrylate, dodecyl methacrylate, cyclopentyl acrylate, cyclopentyl methacrylate, isobornyl acrylate, isobornyl methacrylate, cyclohexyl acrylate and cyclohexyl methacrylate, glycidyl acrylate, glycidyl methacrylate, hydroxyalkyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, 3-hydroxybutyl acrylate, 3-hydroxybutyl methacrylate, 4-hydroxybutyl acrylate, 4-hydroxybutyl methacrylate, acrylic acid and glycidyl versatate condensation product, methacrylic acid and glycidyl versatate condensation product, acrylic acid, and methacrylic acid.

[0012] Other monomers containing carbon-carbon double bonds

[0013] In the present application, the other monomers containing carbon-carbon double bond, i.e. non-acrylic monomers containing carbon-carbon double bond, include but are not limited to one or more selected from styrene, methyl propene, allyl alcohol, vinyl versatate, acrylonitrile, acrylamide, diacetone acrylamide, maleic anhydride, monomethyl maleate, monoethyl maleate, monopropyl maleate, monoisopropyl maleate, monobutyl maleate, monosec-butyl maleate, mono-tert-butyl maleate, monopentyl maleate, monohexyl maleate, monoethylhexyl maleate, dimethyl maleate, diethyl maleate, di-n-propyl maleate, diisopropyl maleate, di-n-butyl maleate, di-sec-butyl maleate, di-tert-butyl maleate, dipentyl maleate, dihexyl maleate, diethylhexyl maleate.

[0014] Initiators

[0015] In the present application, the initiator is selected from azo or peroxide initiator, the azo initiator includes but is not limited to one or a combination of azobis isobutyronitrile, azobis heptyl nitrile, and the peroxide initiator includes but is not limited to one or more selected from benzoyl peroxide, t-butyl peroxy 2-ethylhexanoate, t-amyl peroxy 2-ethylhexanoate, 1,1-bis(t-amyl peroxy)cyclohexane, 1,1-bis(t-amyl peroxy)-3,3,5-trimethyl cyclohexane, t-butyl peroxy benzoate, t-amyl peroxy benzoate, t-amyl peroxy acetate, t-butyl peroxy 3,5,5-trimethyl hexanoate, 3,3-bis(t-butyl peroxy) butyl acetate, 3,3-bis(t-amyl peroxy) butyl acetate, dicumyl peroxide, t-amyl hydroperoxide, t-butyl hydroperoxide, di-t-butyl peroxide, di-t-amyl peroxide.

[0016] In some preferred embodiments of the present application, the high solid content thermosetting hydroxyl acrylic resin comprises, by weight parts:

[0017]

[0018]

[0019] The preparation steps of the high solid content thermosetting hydroxyl acrylic resin include:

[0020] A mixture of n-butyl acrylate, hydroxypropyl acrylate, methyl methacrylate, acrylic acid and styrene is added to high-boiling aromatic hydrocarbon solvent oil S-100 at a temperature of 130-140°C, and incubated at a temperature of 130-140°C for 1-2 hours, to obtain the high solid content thermosetting hydroxyl acrylic resin.

[0021] The high solid thermosetting hydroxyl acrylic resin prepared by the preparation method has good film-forming property, fresh appearance, appearance, gloss, mechanical property and other properties after being used in single-color topcoat.

[0022] Polyester polyols

[0023] In some embodiments of the present application, the polyester polyol comprises, by weight parts:

[0024]

[0025] The polyester polyol under the condition can better react with etherified amino resin, blocked isocyanate crosslinking agent and the like, and on the basis of good VOC reduction, provide more excellent comprehensive performance.

[0026] The preparation steps of the polyester polyol comprise:

[0027] The mixture of trimethylolpropane, hexanediol, isophthalic acid, adipic acid, phthalic anhydride and a catalyst are added into a reaction container with a temperature of 210-220℃, and the polyester polyol is obtained by keeping the temperature at 210-220℃ for 4 hours.

[0028] In some preferred embodiments of the present application, the polyester polyol has a hydroxyl value of 90-160 mgKOH / g, a solid content of 78-82%, and a viscosity of 1800-3400 mPa·s, by weight percentage.

[0029] Etherified amino resins

[0030] In some preferred embodiments of the present application, the etherified amino resin is a butyl etherified amino resin with a solid content of 68-72%; more preferably, the etherified amino resin is selected from one or more of Neoresins SETAMINE US-146BB-72, SETAMINE US-138BB-70, and BASF LUWIPAL 018, with a solid content of 68-70%.

[0031] Blocked isocyanate crosslinkers

[0032] In some embodiments of the present application, the blocked isocyanate crosslinking agent is obtained by reaction of isocyanate and blocking agent, and specifically, the blocked isocyanate crosslinking agent includes but is not limited to one or a combination of Desmodur BL3175A and Desmodur BL 3575 from Covestro. Preferably, the blocked isocyanate content is more than 10% by weight percentage, and the solid content is more than 69%.

[0033] In some preferred embodiments of the present application, the isocyanate includes, but is not limited to, one or more selected from the group consisting of toluene diisocyanate, diphenylmethane diisocyanate, polymethylene polyphenyl diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane isocyanate, trimethylhexamethylene diisocyanate, hydrogenated toluene diisocyanate; and the blocking agent is selected from one or more of the group consisting of methanol, ethanol, propanol, butanol, hexanol, octanol, benzyl alcohol, ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, diethylene glycol monomethyl ether, methyl ethyl ketone oxime, acetone oxime, cyclohexanone oxime, diisopropylamine, 3,5-dimethylpyrazole, N-tert-butylbenzylamine, caprolactam, dimethyl malonate, diethyl malonate, and butanediamine.

[0034] In some more preferred embodiments of the present application, the blocked isocyanate crosslinking agent includes, by weight:

[0035]

[0036] The preparation steps of the blocked isocyanate crosslinking agent include:

[0037] Mixing hexamethylene diisocyanate trimer, dibutyltin dilaurate, methyl isobutyl ketone and heating to 70-80℃, adding a mixture of methyl ethyl ketone oxime and butanediamine at this temperature, and continuing to react until the infrared characteristic absorption peak of isocyanate group at 2200 cm -1 -1 disappears by infrared spectrum observation, stopping heating, and obtaining a blocked isocyanate crosslinking agent with solid content of 71±2%.

[0038] The blocked isocyanate crosslinking agent prepared by the above preparation method can make the topcoat have good acid resistance, film forming property, freshness, mechanical property and other properties after being used in single-color topcoat.

[0039] Diurea compound modified polyester resins

[0040] In some preferred embodiments of the present application, the diurea compound in the diurea compound modified polyester resin is an amine reacted compound of aliphatic diisocyanate, specifically including but not limited to one or more selected from the group consisting of Nuova Setalux 90173SS-50, Setalux 91715SS-55. More preferably, the diurea compound modification amount of the diurea compound modified polyester resin is between 3.0-3.5% by weight percentage.

[0041] Auxiliaries

[0042] In some embodiments of the present application, the auxiliary agent comprises, by weight parts:

[0043]

[0044] In some preferred embodiments of the present application, the ultraviolet light absorber is selected from benzotriazole ultraviolet light absorbers; the light stabilizer is selected from sterically hindered amine light stabilizers; the silicone leveling agent is selected from polyester-modified polydimethylsiloxane silicone leveling agents, which can be combined with other components to achieve the best balance of reducing surface tension, improving slipperiness and other properties; the acrylate leveling agent is selected from non-reactive acrylate leveling agents, which can synergistically act with silicone leveling agents to achieve the best appearance. Specifically, the ultraviolet light absorber includes but is not limited to one or more selected from BASF Tinuvin 928, Tinuvin 384-2, Tinuvin 400, Tinuvin 477; the light stabilizer includes but is not limited to one or more selected from BASF Tinuvin 292, Tinuvin 123; the silicone leveling agent includes but is not limited to one or more selected from BYK-331, BYK-315, BYK-306, BYK-310 of BYK, Tego-450 of DeGussa, BAYSILONE OL-17 of Bayer; the acrylate leveling agent includes but is not limited to one or more selected from BYK-358N of BYK, Tego Flow-300 of DeGussa, Modaflow-2100 of Cytec.

[0045] Solvents

[0046] In some embodiments of the present application, the solvent is selected from one or more of n-butanol, butyl acetate, high-boiling aromatic hydrocarbon solvent oil S-150, diethylene glycol butyl ether, triethylamine. The selected solvent effectively reduces the viscosity while avoiding compounds such as xylene and toluene, which are more harmful to the environment.

[0047] White color paste

[0048] In some embodiments of the present application, the white color paste comprises, by weight parts:

[0049]

[0050] The high-solid thermosetting hydroxy acrylic resin in the white color paste is the same as the high-solid thermosetting hydroxy acrylic resin in the monochromatic topcoat of the present application, which is not repeated here.

[0051] Specifically, the wetting dispersant includes but is not limited to Byk 161 produced by Bichemical; the rutile titanium dioxide includes but is not limited to TIPAQUE CR-97 produced by Nippon Pearl Industry Co., Ltd.

[0052] The acrylic-based high solid monochrome finish of the present application can also add resistivity adjuster, such as BYK-ES 80, according to actual needs. The addition amount of resistivity adjuster is 0-0.5 parts based on 100 parts by weight of total amount, preferably 0.1-0.3 parts.

[0053] The second aspect of the present application provides a method for preparing the acrylic-based high solid monochrome finish of the first aspect of the present application, comprising the following steps:

[0054] S1: sequentially adding high solid thermosetting hydroxyl acrylic resin, polyester polyol into the main cylinder A, stirring at a speed of 200-400 rpm for 10 minutes;

[0055] S2: sequentially adding blocked isocyanate crosslinking agent, diurea compound modified polyester resin, ether type amino resin into the main cylinder A at a speed of 300-500 rpm, and continue stirring for 30 minutes after the addition is completed;

[0056] S3: adding part of the solvent into the auxiliary cylinder B, then adding the auxiliary agent under the condition of uniform stirring at a speed of 200-400 rpm, and continue stirring for 15 minutes; then adding the mixture in the auxiliary cylinder B into the main cylinder A under the condition that the main cylinder A is stirred at a speed of 300-500 rpm, and continue stirring for 20 minutes after the addition is completed;

[0057] S4: sequentially adding part of the solvent into the main cylinder A at a speed of 300-500 rpm, and continue stirring for 20 minutes after the addition is completed;

[0058] S5: sequentially adding white color paste, other color paste into the main cylinder A at a speed of 300-500 rpm, and continue stirring for 30 minutes after the addition is completed;

[0059] S6: diluting the monochrome finish in the main cylinder A to a coating viscosity of 23℃: 35-36 seconds for P-4 cup using the remaining solvent, thereby obtaining the acrylic-based high solid monochrome finish.

[0060] In the specific embodiment, resistivity adjuster can also be added according to actual needs, which is added between steps S5 and S6, and the specific adding method is: adding resistivity adjuster into the main cylinder A at a speed of 300-500 rpm, and continue stirring for 10 minutes after the addition is completed.

[0061] The third aspect of the present application provides an application of the high solid acrylic-based monochrome topcoat according to the first aspect of the present application, which includes an application to the external coating of industrial products such as automobiles, motorcycles, engineering machinery, light industrial products, and the like, and in particular, an application to the external coating of products such as automobile bodies and automobile wheel hubs.

[0062] In some embodiments of the present application, the specific steps of the application include:

[0063] applying and curing a basecoat or midcoat to a substrate, applying the high solid acrylic-based monochrome topcoat to the substrate on which the basecoat or midcoat has been cured, and then curing to obtain a multi-coat finishing system, which is a two-coat two-bake system according to the present application;

[0064] It should be noted that the prior art commonly uses a three-coat two-bake system, and the specific steps include: applying and curing a basecoat or midcoat to a substrate, applying a topcoat to the substrate on which the basecoat or midcoat has been cured, then applying a clearcoat to the surface of the uncured monochrome topcoat, and finally curing the two layers at the same time. Compared with the three-coat two-bake system commonly used in the prior art, the two-coat two-bake system of the present application does not contain a clearcoat coating link, which can effectively reduce the coating process of an automobile factory, reduce VOC, and improve production efficiency.

[0065] The basecoat and midcoat used in the two-coat two-bake system are selected from water-based paint or solvent-based paint, and the application solid content of the basecoat and midcoat is between 25-55% by weight, and the film thickness after curing is 5-40 μm, preferably 6-35 μm.

[0066] In some preferred embodiments of the present application, the application of the high solid acrylic-based monochrome topcoat satisfies the following conditions:

[0067] (1) When spraying, the application solid content of the high solid acrylic-based monochrome topcoat is 62±2%;

[0068] (2) When spraying, the application viscosity of the high solid acrylic-based monochrome topcoat is 23°C: 35-36 seconds for a 4-cup;

[0069] (3) The one-time spraying film thickness of the high solid acrylic-based monochrome topcoat is 30-50 μm;

[0070] (4) The flash-off conditions of the high solid acrylic-based monochrome topcoat are 20-30°C, 60-70% humidity, 5-10 minutes;

[0071] (5) The final baking film-forming conditions of the high solid acrylic-based monochrome topcoat are 145±5°C, 20-30 minutes;

[0072] (6) When construction, the VOC content is less than or equal to 420 g / L.

[0073] Advantages of the present application

[0074] The present application provides a high solid monochrome finish based on acrylic, which uses the combination of thermosetting hydroxyl acrylic resin, polyester polyol, etherified amino resin, and blocked isocyanate crosslinking agent, and the obtained composition has the characteristics of high construction solid (organic solvent volatiles <420 g / L), environmental friendliness, good mechanical properties, excellent appearance and gloss, etc., and integrates the effects of color paint and varnish, without the need for additional varnish coating, and is suitable for industrial products, especially for automotive exterior coating. BRIEF DESCRIPTION OF DRAWINGS

[0075] Figure 1 Schematic diagram of the dripping evaluation method of the monochrome finish coating film in Test Example 3 of the present application. DETAILED DESCRIPTION

[0076] In order to more clearly illustrate the present application, the present application will be further described below in conjunction with preferred embodiments and drawings. Those skilled in the art should understand that the specific description below is illustrative rather than limiting, and should not limit the protection scope of the present application. In the case where the purpose of the present application is clarified and explained by the following examples, the components of the composition are illustrated by weight parts as the general standard. In the absence of specific instructions, for the sake of simplicity, the "parts" described in the examples of the present application have the same meaning as weight parts. Unless otherwise specified, the various raw materials of the present application can be obtained by commercial means; or prepared according to conventional methods in the art. Unless otherwise defined or specified, all professional and scientific terms used in this application have the same meaning as those familiar to those skilled in the art. In addition, any method and material similar or equivalent to those described can be applied to the method of the present application. The experimental methods in the following specific embodiments and examples are not specified, and are usually carried out according to conventional conditions, or according to the conditions recommended by the manufacturer.

[0077] The technical solutions of the present application will be described below in conjunction with specific embodiments.

[0078] Preparation of high solid thermosetting hydroxyl acrylic resin A:

[0079] S1: 2481 parts of high-boiling aromatic hydrocarbon solvent oil S-100 were added to a reaction vessel equipped with a stirrer, thermometer, nitrogen conduit and reflux condenser;

[0080] S2: The reaction system is heated to 130-140°C, and when the reaction temperature is stable, 2590 parts of n-butyl acrylate, 1843 parts of hydroxypropyl acrylate, 1330 parts of styrene, 100 parts of acrylic acid, 726 parts of methyl methacrylate acrylate monomer premix are gradually and uniformly added to the reaction vessel by a pump, and the reaction temperature is maintained at 130-140°C during the process. At the same time, 166 parts of 3,5,5-trimethylhexanoic acid tert-butyl peroxide, 138 parts of dicumyl peroxide initiator, and the above premix are added to the reaction vessel at the same rate by another pump and pipeline. The rate is controlled to ensure that the dropping is completed within 2-4 hours;

[0081] S3: After the above acrylate monomer premix and initiator are added, continue to heat at 130-140°C for 1-2 hours, and terminate the reaction. A high solid content thermosetting hydroxyl acrylate resin A with a solid content of 70±1%, a hydroxyl value of 85 mgKOH / g, a glass transition temperature (Tg) of -5°C, and a number average molecular weight of about 4200 is obtained.

[0082] Preparation of polyester polyol B:

[0083] S1: 11.4 parts of trimethylolpropane, 42.68 parts of hexanediol, 36 parts of isophthalic acid, 16.14 parts of adipic acid, 6.29 parts of phthalic anhydride, and 0.1 parts of dibutyl tin oxide are added to a reaction vessel equipped with a stirrer, a thermometer, a nitrogen conduit, and a reflux condenser;

[0084] S2: The temperature is slowly and uniformly increased to 215±5°C within 3.5-4.5 hours, and the temperature is maintained for 3.5-4.5 hours. A polyester polyol B with a hydroxyl value of 132 mgKOH / g, a solid content of 78-82%, and a viscosity of 1800-3400 mPa·s is obtained.

[0085] Preparation of blocked isocyanate crosslinking agent C:

[0086] S1: 350 parts of hexamethylene diisocyanate trimer, 0.5 parts of dibutyltin dilaurate, and 35 parts of methyl isobutyl ketone are added to a reaction vessel equipped with a stirrer, a thermometer, a nitrogen conduit, and a reflux condenser. Then the reaction system is heated to 70°C;

[0087] S2: After the temperature is constant, a mixture of 212 parts of methyl ethyl ketone oxime and 111 parts of butanediamine is added uniformly within 1-2 hours. The reaction temperature is controlled during the addition process to keep the temperature below 80°C;

[0088] S3: After the addition is completed, the reaction is continued at this temperature for 4-5 hours, and samples are taken every 1 hour to observe the wave number of about 2200 cm-1 by infrared spectrum. 1The infrared characteristic absorption peak of the isocyanate group disappears, and after the characteristic absorption peak completely disappears, the heating is stopped, and a solid content of 71±2% of the blocked isocyanate crosslinking agent C is obtained.

[0089] Preparation of white color paste D:

[0090] S1: In a stirrer, 27.144 parts of high solid content thermosetting hydroxyl acrylic resin A was added, and the stirring speed was kept at 200-300 rpm, 2.812 parts of Byk 161 wetting dispersant was added, and stirring was continued for 10 minutes, then 60.822 parts of TIPAQUE CR-97 was added;

[0091] S2: Stop stirring, use 0.932 parts of high-boiling aromatic hydrocarbon solvent oil S-100 to clean the cylinder wall and stirring shaft. Turn on the stirring and adjust the stirring speed to 500-600 rpm, stir for 45 minutes to 1 hour, then reduce the stirring speed to 300-500 rpm, add 5.177 parts of high-boiling aromatic hydrocarbon solvent oil S-100, continue to stir for 20-30 minutes, and obtain a color paste premix;

[0092] S3: The color paste premix was ground to a fineness of ≤5 μm using a sand mill and 0.8 mm zirconium beads. When the sand mill was discharged, 3.113 parts of high-boiling aromatic hydrocarbon solvent oil S-100 was used to clean the sand mill cylinder and its pipeline, and the washing liquid entered the sand mill color paste, and white color paste D was obtained.

[0093] Example 1: High solid content single color topcoat 1 based on acrylic acid

[0094] High solid content single color topcoat 1 based on acrylic acid was prepared according to Table 1, and the preparation steps were as follows:

[0095] S1: High solid content thermosetting hydroxyl acrylic resin A and polyester polyol B were sequentially added to the main cylinder A, and stirred at a speed of 200-400 rpm for 10 minutes;

[0096] S2: Blocked isocyanate crosslinking agent C, SETALUX 91715SS-55, and SETAMINE US-138BB-70 were sequentially added to the main cylinder A at a speed of 300-500 rpm, and stirring was continued for 30 minutes after the addition was completed;

[0097] S3: High-boiling aromatic hydrocarbon solvent S-150 and triethylamine were added to the auxiliary cylinder B, and then Tinuvin 292, Tinuvin 384-2, Byk-358N, and Byk-310 were added under uniform stirring at a speed of 200-400 rpm, and stirring was continued for 15 minutes. The mixture obtained in the auxiliary cylinder B was then added to the main cylinder A under stirring at a speed of 300-500 rpm in the main cylinder A, and stirring was continued for 20 minutes after the addition was completed.

[0098] S4: At a speed of 300-500 rpm, add n-butanol, butyl acetate, and diethylene glycol butyl ether to the master cylinder A in sequence. After the addition is complete, continue stirring for 20 minutes.

[0099] S5: At a speed of 300-500 rpm, add white pigment D, OTO 640(T)MAPICOYELLOW yellow pigment, OTO 640(T)GREEN S (170kg) pigment, and OTO 640(T)BLACK (170kg) black pigment to the main cylinder A in sequence. After adding all the pigments, continue stirring for 30 minutes.

[0100] S6: Add BYK-ES 80 resistivity regulator to master cylinder A at a speed of 300-500 rpm, and continue stirring for 10 minutes after the addition is complete;

[0101] S7: Use an appropriate amount of high-boiling-point aromatic solvent oil S-150 to dilute the monochrome topcoat in master cylinder A to the suitable viscosity described in Table 1, thereby obtaining acrylic-based high-solids monochrome topcoat 1.

[0102] Example 2: High-solids monochrome topcoat based on acrylic 2

[0103] According to Table 1, a high-solids monochrome topcoat based on acrylic acid was prepared. The preparation steps were the same as in Example 1, except that the blocked isocyanate crosslinking agent C was replaced with an equal amount of Desmodur BL 3175A blocked isocyanate crosslinking agent produced by Covestro.

[0104] Comparative Examples 1-3: Monochrome topcoats 1-3 used as comparative examples

[0105] Topcoats 1-3, used as comparative examples, were prepared according to Table 1. The preparation steps were the same as in Example 1, except that:

[0106] Comparative Example 1 does not contain polyester polyol B, but is replaced with thermosetting hydroxyl acrylic resin A with high solids content and equal solids content.

[0107] In Comparative Example 2, the blocked isocyanate crosslinking agent C was replaced with a high-solids thermosetting hydroxyl acrylic resin A with equal solids content.

[0108] Comparative Example 3 did not contain polyester polyol B, but was replaced with an equal amount of Desmophen 670BA polyester resin produced by Covestro.

[0109] Table 1 Formulations of Examples 1-2 and Comparative Examples 1-3

[0110]

[0111]

[0112] The monochrome topcoats obtained in Examples 1-2 and Comparative Examples 1-3 were tested after application, and the specific tests are as follows.

[0113] Test Example 1: Two-coat, two-bake process

[0114] Test steps:

[0115] On a passivated steel plate treated with zinc phosphate, PN-310 electrophoretic coating (a cationic electrophoretic coating manufactured by Nippon Paint) was applied until the dried coating film thickness reached 20 μm. The film was then heated at 160°C for 30 minutes to cure, followed by cooling to form a cured electrophoretic coating film. Subsequently, a two-coat, two-bake process (intermediate coat and single-color topcoat layer) was used to spray the single-color topcoat obtained in Examples 1-2 and Comparative Examples 1-3 onto this electrophoretic coating film, with other conditions shown in Table 2 below.

[0116] Table 2 shows the formulation and construction conditions for the two-coat, two-bake process in Test Example 1.

[0117]

[0118] Then, based on the contents of Table 3, various indicators were tested, and the test results are shown in Table 4.

[0119] Table 3 Testing Items

[0120]

[0121]

[0122] Table 4 Test Results

[0123]

[0124] As shown in Table 4, polyester polyol B, due to the presence of trimethylolpropane in its structure, is trifunctional, and its resin structure is a nonlinear three-dimensional structure with isophthalic acid and phthalic anhydride running through it. This three-dimensional structure enhances cross-linking during coating film formation, improving mechanical properties such as stone impact resistance. Furthermore, the steric hindrance of this three-dimensional polyester resin is greater than that of the linear structure, reducing resin entanglement in the coating liquid. Therefore, at the same application viscosity, the application solids content of Examples 1 and 2 is significantly higher than that of Comparative Example 1, more effectively reducing VOCs during coating application. Its structure also significantly improves appearance DOI and gloss. Meanwhile, the blocked isocyanate crosslinking agent C, due to its isocyanate structure, enhances stone impact resistance and acid resistance. The self-made polyester polyol B and the blocked isocyanate crosslinking agent C perform better than or no worse than similar commercially available products.

[0125] Test Example 2: Three-coat two-bake process

[0126] Test steps:

[0127] On a passivated steel plate treated with zinc phosphate, PN-310 electrophoretic coating (a cationic electrophoretic coating manufactured by Nippon Paint) was applied until the dried coating film thickness reached 20 μm. The film was then heated at 160°C for 30 minutes to cure, followed by cooling to form a cured electrophoretic coating film. Subsequently, AR 2600 Milan White water-based paint was sprayed onto this electrophoretic coating film using a three-coat, two-bake process, with other conditions shown in Table 5 below.

[0128] Table 5 shows the formulation and construction conditions for the three-coat, two-bake process in Test Example 2.

[0129]

[0130] The coating system after spraying AR 2600 Milan White water-based paint was used as Comparative Example 4. The results of comparing Example 1 and Comparative Example 4 in Test Example 1 are shown in Table 6.

[0131] Table 6 Test Results

[0132]

[0133]

[0134] As shown in Table 6, Example 1 and Comparative Example 4 produce the same color effect after being painted on the car body. The difference lies in that Example 1 is a single-coat, single-process single-layer topcoat, while Comparative Example 4 is a double-coat, double-process white paint + single-component clear coat. The single-coat topcoat of Example 1 has the same performance as the double-coat containing clear coat, and the appearance is also very similar. Therefore, the single-coat topcoat technology described in this invention can replace the double-coat technology containing clear coat, effectively reducing painting processes in automobile factories, lowering VOCs, and improving production efficiency. Furthermore, the high-solids single-coat topcoat based on acrylic described in this invention itself has characteristics such as high application solids, low VOCs, environmental friendliness, excellent performance and appearance, and superior gloss, making it very suitable for industrial products, especially automotive exterior painting.

[0135] Test Example 3: Construction Inspection

[0136] Using a two-coat, two-bake process Figure 1 The perforated steel plate shown was coated. The intermediate coat and color paint were the same as in Test Example 1, applied using normal spraying. When spraying the single-color topcoat, the spraying direction was from right to left, and the spray gun travel speed gradually increased, thus forming a coating with a thickness that decreased from thick to thin. The thickness of the composite coating at 0.5 cm below the lower edge of the perforation was measured as the coating's sag limit thickness. The appearance of the first pinhole was considered the coating's pinhole limit. The matching coatings are shown in Table 2, and the results are summarized in Table 7.

[0137] Table 7. Results of Construction Review

[0138] Test items Example 1 Sag limit pm 55 Pinhole limit pm 60

[0139] As shown in Table 7, the high-solids monochrome topcoat based on acrylic described in this invention has high values ​​in terms of pinhole limit and sagging limit, which can fully meet the coating requirements of various automobile OEMs.

[0140] In summary, the acrylic-based high-solids monochrome topcoat of the present invention has the characteristics of high application solids (volatile organic solvents <420g / L), environmental friendliness, good mechanical properties, and excellent appearance and gloss. It is particularly suitable for automotive exterior coating, and is also suitable for exterior coating of automotive wheels, motorcycles, construction machinery, light industrial products, etc.

[0141] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. An acrylic acid-based high solid monochrome topcoat, comprising, by weight parts:

2. The high solids acrylic-based monochromatic topcoat of claim 1, wherein, The high solid thermosetting hydroxyl acrylic resin is selected from a copolymer of acrylic monomers and other monomers containing carbon-carbon double bonds; preferably, the number average molecular weight of the high solid thermosetting hydroxyl acrylic resin is 3500-5500, the hydroxyl value is 80-150 mgKOH / g, the acid value is 6.5-10.5 mgKOH / g, the glass transition temperature is between -10℃ to +10℃, and the solid content of the high solid thermosetting hydroxyl acrylic resin is between 69-71% by weight percentage.

3. The high solids acrylic-based monochromatic topcoat of claim 1 or 2, wherein, The high solid thermosetting hydroxyl acrylic resin comprises, by weight parts: The preparation steps of the high solid thermosetting hydroxyl acrylic resin include: adding a mixture of n-butyl acrylate, hydroxypropyl acrylate, methyl methacrylate, acrylic acid, and styrene, together with 3,5,5-trimethylhexanoic acid tert-butyl peroxide and dicumyl peroxide, into high-boiling aromatic hydrocarbon solvent oil S-100 at a temperature of 130-140℃, and incubating at a temperature of 130-140℃ for 1-2 hours to obtain the high solid thermosetting hydroxyl acrylic resin.

4. The high solids acrylic-based monochromatic topcoat of claim 1, wherein, The polyester polyol comprises, by weight parts: The preparation steps of the polyester polyol include: adding a mixture of trimethylolpropane, hexanediol, isophthalic acid, adipic acid, phthalic anhydride, and a catalyst into a reaction vessel at a temperature of 210-220℃, and incubating at a temperature of 210-220℃ for 4 hours to obtain the polyester polyol; preferably, the hydroxyl value of the polyester polyol is 90-160 mgKOH / g by weight percentage, the solid content is between 78-82%, and the viscosity is 1800-3400 mPa·s.

5. The high solids acrylic-based monochromatic topcoat of claim 1, wherein, The etherified amino resin is a butyl etherified amino resin; preferably, the solid content of the etherified amino resin is between 68-72% by weight percentage; more preferably, the solid content of the etherified amino resin is between 68-70%; the blocked isocyanate crosslinking agent is obtained by the reaction of isocyanate and blocking agent; preferably, the mass content of blocked isocyanate of the blocked isocyanate crosslinking agent is more than 10% by weight percentage, and the solid content is more than 69%; the diurea compound in the diurea compound modified polyester resin is a compound obtained by the reaction of aliphatic diisocyanate and amine; preferably, the diurea compound modification amount of the diurea compound modified polyester resin is between 3.0-3.5% by weight percentage.

6. The high solids acrylic-based monochromatic topcoat of claim 1 or 5, wherein, The blocked isocyanate crosslinking agent comprises, by weight parts: The preparation steps of the blocked isocyanate crosslinking agent include: mixing hexamethylene diisocyanate trimer, dibutyl tin dilaurate and methyl isobutyl ketone and heating to 70-80℃, adding a mixture of methyl ethyl ketoxime and butanediamine at this temperature, and continuing to react until the infrared characteristic absorption peak of isocyanate group at 2200cm -1 -1 disappears by infrared spectroscopy, stopping heating, and obtaining a blocked isocyanate crosslinking agent with a solid content of 71±2%.

7. The high solids acrylic-based monochromatic topcoat of claim 1, wherein, The auxiliary agent includes but is not limited to one or more of ultraviolet light absorbers, light stabilizers, silicone leveling agents, acrylate leveling agents; preferably, the ultraviolet light absorber is selected from benzotriazole ultraviolet light absorbers, the light stabilizer is selected from steric amine light stabilizers, the silicone leveling agent is selected from polyester modified polydimethylsiloxane silicone leveling agents, and the acrylate leveling agent is selected from non-reactive acrylate leveling agents; the solvent is selected from one or more of n-butanol, butyl acetate, high-boiling aromatic hydrocarbon solvent oil S-150, diethylene glycol butyl ether, triethylamine.

8. The high solids acrylic-based monochromatic topcoat of claim 1, wherein, The white color paste includes, by weight parts:

9. A process for the preparation of a high solids acrylic based monochromatic topcoat according to any one of claims 1 to 8, characterized in that, The method includes the following steps: S1: sequentially adding high solid content thermosetting hydroxyl acrylic resin, polyester polyol into main cylinder A, stirring at a speed of 200-400 rpm for 10 minutes; S2: sequentially adding blocked isocyanate crosslinking agent, diurea compound modified polyester resin, ether type amino resin into main cylinder A at a speed of 300-500 rpm, and continue stirring for 30 minutes after the addition is completed; S3: adding part of the solvent into auxiliary cylinder B, then adding auxiliary agent under the condition of uniform stirring at a speed of 200-400 rpm, and continue stirring for 15 minutes; then adding the mixture in auxiliary cylinder B into main cylinder A under the condition that main cylinder A is stirring at a speed of 300-500 rpm, and continue stirring for 20 minutes after the addition is completed; S4: sequentially adding part of the solvent into main cylinder A at a speed of 300-500 rpm, and continue stirring for 20 minutes after the addition is completed; S5: sequentially adding white color paste, other color paste into main cylinder A at a speed of 300-500 rpm, and continue stirring for 30 minutes after the addition is completed; S6: diluting the single color topcoat in main cylinder A to a coating viscosity of 35-36 seconds for 4 cups at 23 DEG C using the remaining solvent, thereby obtaining the high solid content single color topcoat based on acrylic acid.

10. Use of an acrylic based high solids monochrome topcoat according to any one of claims 1 to 8, characterized in that, The method includes the following steps: S1: applying primer or midcoat to the substrate and curing it; S2: applying the high solid content single color topcoat based on acrylic acid to the substrate on which the primer or midcoat has been cured, and then curing it; The primer or midcoat is selected from water-based paint or solvent-based paint, respectively, and the solid content of the primer and midcoat is between 25-55% by weight percentage, and the film thickness after curing is 5-40 μm, preferably 6-35 μm; preferably, the solid content of the high solid content single color topcoat based on acrylic acid is 62±2% during application, the coating viscosity is 35-36 seconds for 4 cups at 23 DEG C, the one-time spray film thickness is 30-50 μm, the flash drying condition is 5-10 minutes under the condition of 20-30 DEG C and humidity of 60-70%, the final film forming condition is 145±5 DEG C for 20-30 minutes, and the VOC content is less than or equal to 420 g / L.

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