CN110655857B

CN110655857B - Water-based colored paint suitable for wet spraying process and application thereof

Info

Publication number: CN110655857B
Application number: CN201911071405.3A
Authority: CN
Inventors: 朱敏德; 夏天渊; 印维坚; 许建华; 毛方桂; 王飞
Original assignee: Nippon Paint China Co Ltd
Current assignee: Nippon Paint China Co Ltd
Priority date: 2019-11-05
Filing date: 2019-11-05
Publication date: 2022-03-18
Anticipated expiration: 2039-11-05
Also published as: CN110655857A

Abstract

The invention discloses a water-based colored paint suitable for a wet spraying process, which comprises the following components in parts by weight: 10-20 parts of waterborne polyurethane, 10-20 parts of core-shell structure acrylic emulsion, 10-15 parts of water-soluble amino resin, 5-10 parts of water-soluble acrylic acid, 10-20 parts of water-soluble polyester, 0-5 parts of effect pigment, 5-20 parts of auxiliary agent and 0-10 parts of water-based color paste; wherein the number average molecular weight of the waterborne polyurethane is 1000-5000, and the hydroxyl value is 100-200 mgKOH/g; the glass transition temperature of the acrylic emulsion with the core-shell structure is 30-60 ℃, and the hydroxyl value is 80-150mg KOH/g. The water-based colored paint has good application property and appearance in a wet spraying process, effectively avoids common paint film defects of pinholes, popping, sagging, mixed layers and the like, and improves the color effect of effect pigments.

Description

Water-based colored paint suitable for wet spraying process and application thereof

Technical Field

The invention relates to the technical field of coatings. More particularly, it relates to a water-based colored paint suitable for wet spraying process and its application.

Background

The production of the Chinese automobile market has been the first place in the world through continuous and rapid growth, and brings a great deal of coating demand. Meanwhile, the development and application of water-based automobile coatings are promoted by the increasingly severe environmental protection pressure. In Germany, France, Japan and other countries have begun to apply a large amount of automotive base paints with water-based paints. In China, from 2016, 1/1, the latest revised air pollution prevention and control laws are formally implemented by the government of China, and Volatile Organic Compounds (VOCs) are brought into the supervision range for the first time, which puts more strict requirements on the coating industry. How to reduce the amount of organic solvent in the coating system becomes an important target of reducing air pollution and energy consumption, which are closely related to environmental protection. The water-based color paint of automobile factories is one of effective means for environmental protection, and is increasingly adopted in domestic main engine factories such as Jili automobiles, Changan automobiles and the like. Compared with the traditional solvent-based colored paint, the paint also brings a plurality of technical requirements for further improvement in the aspects of workability and the like.

In the traditional solvent-based colored paint, different solvents such as butyl acetate, xylene, 100# solvent oil, propylene glycol methyl ether acetate and the like are usually used in the formula to adjust the volatilization rate of a wet film after the paint is sprayed so as to avoid the paint film defects such as pinholes, explosion holes, sagging, mixed layers and the like which are easy to occur in construction. Meanwhile, the arrangement distribution of effect pigments such as aluminum powder, pearl and the like in a coating film and the color effect generated by the effect pigments are often optimized by different solvents in solvent-based colored paint. In contrast, the existing water-based colored paint uses a large amount of water as a solvent, and it is difficult to adjust the volatilization rate. The workability of the paint and the glitter of the effect pigment are often improved by adding a large amount of additives or the characteristics of the resin itself. A large amount of additives such as polyethylene wax, bentonite, organic silicon modified defoaming agent and the like inevitably cause other negative effects, such as reduction of the mechanical property of a coating film, reduction of chemical resistance, reduction of weather resistance and the like, and small molecular additives can be slowly released to the external environment for a long time to cause bad influence on the natural environment or biological ecology and the like. If the characteristics of the resin can meet most of construction requirements, and the use of a large amount of auxiliary agents in the water-based colored paint is reduced, the method becomes very advantageous.

On the other hand, in order to reduce energy consumption and improve benefits, the original automobile factory paint basically and completely abandons the traditional three-coating and three-baking coating process, and the three-coating and two-baking process is largely adopted and gradually converted into the three-coating and one-baking process at present. That is, the color paint is not fully baked at 140 ℃ and above, but is dehydrated for 5-10 minutes under the condition of 60-90 ℃, and then is directly sprayed with wet spray varnish on the color paint, and then a plurality of coatings are baked and crosslinked together. Because the varnish is almost all solvent-based products at present. Under the condition that the water-based colored paint is not fully dried and also contains water, the risk of paint film defects caused by the water-based colored paint is greatly increased by wet spraying of the solvent-based varnish, and compared with the traditional technology, the ideal appearance and color effect are difficult to achieve. In addition, in order to improve the production efficiency, the automobile host factory uses the same colored paint to be matched with different varnishes sometimes, and puts more severe requirements on the workability and the matching of the colored paint.

Therefore, it is desirable to provide an aqueous colored paint suitable for wet spray wet process having good appearance and workability.

Disclosure of Invention

The invention aims to provide a water-based colored paint suitable for a wet spraying process, and the water-based colored paint is suitable for wet spraying processes matched with various varnishes. The colored paint has good application property, can effectively avoid the defects of common paint films such as pinholes, shrinkage cavities, sagging, mixed layers and the like, simultaneously improves the directionality of equivalent pigments such as aluminum powder and pearly-lustre in the colored paint, and obtains the appearance of a paint film with a flashing effect. In addition, the water-based colored paint has good properties such as mechanical property, chemical resistance and the like; compared with the traditional colored paint, the use amount of a plurality of small molecular auxiliary agents can be reduced.

The second purpose of the invention is to provide the application of the water-based colored paint suitable for the wet spraying process.

In order to achieve the first purpose of the invention, the invention adopts the following technical scheme:

the water-based colored paint suitable for the wet spraying process comprises the following components in parts by weight:

10-20 parts of waterborne polyurethane, 10-20 parts of core-shell structure acrylic emulsion, 10-15 parts of water-soluble amino resin, 5-10 parts of water-soluble acrylic acid, 10-20 parts of water-soluble polyester, 0-5 parts of effect pigment, 5-20 parts of auxiliary agent and 0-10 parts of water-based color paste;

wherein the number average molecular weight of the waterborne polyurethane is 1000-5000, and the hydroxyl value is 100-200 mgKOH/g; the glass transition temperature of the acrylic emulsion is 30-60 ℃, and the hydroxyl value is 80-150mg KOH/g.

Optionally, the pH of the aqueous pigmented paint is 8.0-8.5.

Optionally, the mass ratio of the non-volatile parts in the water-based colored paint is 20-30%.

Optionally, the B-type viscosity of the aqueous pigmented paint is from 3000mPa · s to 4500mPa · s.

Optionally, the preparation process of the waterborne polyurethane comprises: uniformly mixing polyester polyol, dihydric alcohol, trihydric alcohol, a compound containing an anionic functional group and a catalyst, heating to 60-120 ℃, adding non-cyclic aliphatic diisocyanate, and reacting at constant temperature; after the reaction is finished, cooling to 30-50 ℃ for amine neutralization; after neutralization, adding deionized water, and cooling to 20-40 ℃ to obtain waterborne polyurethane;

wherein the non-cyclic aliphatic diisocyanate may be replaced with a non-cyclic aliphatic diisocyanate polymer, an alicyclic diisocyanate or an alicyclic diisocyanate polymer;

the number average molecular weight of the polyester polyol is 500-2000, the acid value in the solid content is less than 5, and the hydroxyl value is 100-300mg KOH/g; the compound containing an anionic functional group is a compound having a functionality of not less than 2 capable of reacting with an isocyanate.

Optionally, in the preparation process of the aqueous polyurethane, the mass ratio of the polyester polyol, the dihydric alcohol, the trihydric alcohol, the compound containing the anionic functional group, the catalyst and the non-cyclic aliphatic diisocyanate is (10-30): (0.5-5): (0.5-5): (0.5-5): (0.01-0.1): (5-20).

Optionally, the preparation process of the acrylic emulsion with the core-shell structure comprises the following steps:

(1) preparation of the acrylic emulsion core part: dissolving acrylic acid monomer, nonionic emulsifier, anionic emulsifier and water-soluble initiator in deionized water, mixing uniformly, reacting at constant temperature of 80 + -20 deg.C for 50-150min, and neutralizing with amine to obtain acrylic emulsion core;

(2) preparation of acrylic emulsion shell part: dissolving acrylic acid monomer and non-ionic emulsifier in deionized water, and stirring and mixing uniformly to obtain an acrylic acid emulsion shell part;

(3) mixing the acrylic emulsion shell part and the acrylic emulsion core part, and keeping the temperature at 80 +/-20 ℃ for 60-240min to obtain the acrylic emulsion with the core-shell structure.

Optionally, the effect pigment is selected from at least one of scale-shaped aluminum powder, resin-coated aluminum powder, coated colored aluminum powder, natural mica-type pearl powder, synthetic mica-type pearl powder and coated pearl powder.

Optionally, the auxiliary agent is selected from at least one of an antifoaming agent, a leveling agent, a dispersing agent and a thickening agent.

To achieve the second object of the present invention, the present invention provides the use of the above-mentioned aqueous colored paint for forming a coating layer on a substrate by using a three-coat two-bake process or a three-coat one-bake process.

The invention has the following beneficial effects:

the invention provides the water-based colored paint which simultaneously contains the low-molecular weight high-hydroxyl-value water-based polyurethane and the core-shell structure high-hydroxyl-value acrylic emulsion and is suitable for the wet spraying process. And when the modified polyurethane is matched with different varnishes, the modified polyurethane shows excellent stability. In addition, the water-based colored paint has important value in the aspects of environmental protection and chemical safety management, and becomes a better choice in commercial water-based industrial coatings.

Drawings

The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.

Fig. 1 shows a perforated steel plate used in the workability test in example 4 of the present invention.

Detailed Description

In order to more clearly illustrate the invention, the invention is further described below with reference to preferred embodiments and the accompanying drawings. Similar parts in the figures are denoted by the same reference numerals. It is to be understood by persons skilled in the art that the following detailed description is illustrative and not restrictive, and is not to be taken as limiting the scope of the invention.

The water-based colored paint suitable for the wet spraying process comprises the following raw materials in parts by weight:

wherein the number average molecular weight of the waterborne polyurethane is 1000-5000, and the hydroxyl value is 100-200 mgKOH/g; the glass transition temperature of the acrylic emulsion with the core-shell structure is 30-60 ℃, and the hydroxyl value is 80-150mg KOH/g.

In the composition of the water-based colored paint, the hydroxyl values of the water-based polyurethane and the acrylic emulsion with the core-shell structure are high, the number average molecular weight of the water-based polyurethane is lower and is 1000-5000, the acrylic emulsion has the core-shell structure, and the two substances with special structures and high hydroxyl values play an important role in various wet spraying processes of the water-based colored paint.

Hydroxyl on the water-based polyurethane molecule and the acrylic emulsion molecule and other functional groups such as carboxyl in the system form a three-dimensional hydrogen bond network. At high shear rates during paint construction, the hydrogen bonding network is broken, leaving the paint in a low viscosity state and a good appearance. After the colored paint is sprayed, in the flashing and dehydration stages before the varnish is wet-sprayed and wet-coated, the hydrogen bond network is quickly recovered, so that the viscosity is quickly recovered, and the problems of sagging, mixed layers and the like are avoided. Meanwhile, the water-based colored paint has good dehydration rate to avoid the paint film defects of pinholes and popping before wet spraying wet coating varnish through the molecular weight and the structural design of the water-based polyurethane, the structural design of the acrylic emulsion and the glass transition temperature. On the other hand, hydroxyl is used as one of anchoring groups of the effect pigment, and the high hydroxyl value aqueous polyurethane and the acrylic emulsion have excellent affinity and stability for the effect pigment, so that irregular movement of the response pigment becomes more stable when the coating is formed into a film, and the flickering effect of the coating after the film is formed is improved. The system structure of the water-based colored paint also ensures the requirements of the whole car factory on the performance of the coating film, such as weather resistance, chemical resistance, mechanical performance and the like.

In a preferred example, the pH of the aqueous pigmented paint is 8.0-8.5. Under the pH value, the water-based colored paint has good appearance and construction performance.

The proportion of non-volatile matter in the aqueous colored paint has an influence on the drying rate, sag prevention property, and the like thereof, and preferably, the proportion of non-volatile matter in the aqueous colored paint is 20 to 30%.

In another preferred example, the B-type viscosity of the aqueous pigmented paint is from 3000 mPas to 4500 mPas.

The properties of the waterborne polyurethane of the present invention have an important influence on the performance of the waterborne color paint, and preferably, the preparation process of the waterborne polyurethane comprises: uniformly mixing polyester polyol, dihydric alcohol, trihydric alcohol, a compound containing an anionic functional group and a catalyst, heating to 60-120 ℃, adding non-cyclic aliphatic diisocyanate, and reacting at constant temperature; after the reaction is finished, cooling to 30-50 ℃ for amine neutralization; after neutralization, adding deionized water, and cooling to 20-40 ℃ to obtain waterborne polyurethane;

wherein the acyclic aliphatic diisocyanate may be replaced with an acyclic aliphatic diisocyanate polymer, an alicyclic diisocyanate, or an alicyclic diisocyanate polymer;

the number average molecular weight of the polyester polyol is 500-2000, the acid value in the solid content is less than 5, and the hydroxyl value is 100-300mg KOH/g; the compound having an anionic functional group is a compound having a functionality of not less than 2 capable of reacting with an isocyanate, including but not limited to N-methylpyrrolidone.

Preferably, in the preparation process of the waterborne polyurethane, the mass ratio of the polyester polyol, the dihydric alcohol, the trihydric alcohol, the compound containing the anionic functional group, the catalyst and the non-cyclic aliphatic diisocyanate is as follows: (10-30): (0.5-5): (0.5-5): (0.5-5): (0.01-0.1): (5-20).

Further, catalysts used in the synthesis of the waterborne polyurethane include, but are not limited to, dibutyltin dilaurate, dibutyltin oxide, zinc isooctanoate, and Borchi Kat22 catalyst, Borchi Kat24 catalyst, Borchi KAT VP 0243 catalyst, Borchi KAT VP 0244 catalyst, Borchi KAT VP 0245 catalyst, K-Kat 4205 catalyst, available from OMG, USA.

The isocyanate-containing monomer used in the synthesis of the waterborne polyurethane is selected from 1, 4-diisocyanatobutane, 1, 6-diisocyanatohexane, 2-methyl-1, 5-diisocyanatopentane, 1, 5-diisocyanato-2, 2-dimethyl-pentane, 2, 4-trimethyl-1, 6-diisocyanatohexane, 2,4, 4-trimethyl-1, 6-diisocyanatohexane, 1, 10-diisocyanatodecane and isophorone diisocyanate.

In a specific embodiment, the synthesis process of the polyester polyol, which is one of the raw materials for preparing the aqueous polyurethane of the present invention, is as follows: mixing a plurality of alcoholic hydroxyl monomers and a catalyst, heating until the raw materials are dissolved, continuously stirring and heating to 160 ℃, and keeping the temperature for 1 h; then the temperature is raised to 230 ℃, and the temperature is maintained until the polyester polyol with the acid value of less than 5 and the hydroxyl value of 100-300mg KOH/g is obtained. Here, the catalyst used is the same as that used in the preparation of the aqueous polyurethane; a wide variety of alcoholic hydroxyl group-containing monomers include, but are not limited to, neopentyl glycol, diethylene glycol, 1, 6-hexanediol, trimethylolpropane, 1, 6-adipic acid, and the like.

In some preferred examples, the preparation process of the acrylic emulsion with the core-shell structure comprises the following steps:

(1) preparation of the acrylic emulsion core part: dissolving acrylic acid monomer, nonionic emulsifier, anionic emulsifier and water-soluble initiator in deionized water, mixing uniformly, reacting at 80 + -2 deg.C for 50-150min, and neutralizing with amine to obtain acrylic emulsion core;

(3) mixing the acrylic emulsion shell part and the acrylic emulsion core part, and keeping the temperature at 80 +/-2 ℃ for 60-240min to obtain the acrylic emulsion with the core-shell structure.

Preferably, the acrylic monomer used in the synthesis of the acrylic emulsion is selected from acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, lauryl acrylate, isopropyl acrylate, isobutyl acrylate, tert-butyl acrylate, isooctyl acrylate, isodecyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, lauryl methacrylate, stearyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, isooctyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, acrylonitrile, methacrylonitrile, isobornyl acrylate, isobornyl methacrylate, methyl acrylate, methyl methacrylate, n-propyl acrylate, n-butyl methacrylate, n-acrylate, n-butyl methacrylate, n-acrylate, n-butyl acrylate, n-butyl acrylate, n-acrylate, and/or a-acrylate, n-acrylate, and a-acrylate, or a-acrylate copolymer, One or more of styrene.

Preferably, the emulsifier used in the synthesis of the acrylic emulsion is selected from one or more of NE-10, NE-20, NE-30, SE-10N, SE-1025A, ER-10, ER-20, ER-30, ER-40, SR-10, SR-20, SR-1025 and SR-3025 from Adeka.

In some preferred examples, the effect pigment in the aqueous paint is selected from at least one of a scale-shaped aluminum powder, a resin-coated aluminum powder, a coated colored aluminum powder, a natural mica-type pearl powder, a synthetic mica-type pearl powder, and a coated pearl powder.

In some preferred examples, the auxiliary agent in the aqueous color paint is selected from at least one of a defoaming agent, a leveling agent, a dispersing agent, and a thickening agent.

In another aspect of the invention, there is also provided the use of the above-described aqueous pigmented paint suitable for use in a wet-on-wet process for forming a coating on a substrate using a three-coat two-bake process or a three-coat one-bake process.

The three-coating one-baking process comprises the following steps:

(1) spraying the water-based intermediate coating to ensure that the film thickness of a dry coating film is 10-20 mu m, and forming an uncrosslinked and cured water-based intermediate coating film;

(2) spraying water-based colored paint on the unbaked water-based intermediate coating film in the step (1) to enable the dry coating film thickness of the water-based colored paint to reach 10-20 mu m, and forming an uncured water-based colored paint coating film;

(3) drying and dehydrating the unbaked and cured water-based intermediate coat film and the water-based colored paint film obtained in the steps (1) and (2) at 60-90 ℃ for 5-10 minutes, and then spraying a varnish coating to enable the film thickness of the dried film to reach 30-50 mu m so as to form an uncured varnish film;

(4) and (4) simultaneously baking the uncured aqueous intermediate coating, the color paint and varnish composite coating obtained in the step (3) at 140-160 ℃ for 20-30 minutes at one time to cure the coating, so as to form the composite coating comprising the aqueous intermediate coating, the aqueous color paint coating and the varnish coating.

The three-coating two-baking process comprises the following steps:

(1) spraying the water-based intermediate coating to ensure that the film thickness of a dry coating film is 10-40 mu m, and forming an uncrosslinked and cured water-based intermediate coating film;

(2) coating the unbaked water-based material in the step (1) in baking reaction at the temperature of 140 ℃ and 160 ℃ for 20-30 minutes;

(3) spraying water-based colored paint on the cured water-based intermediate coating film obtained in the step (2) and enabling the dry coating film thickness of the water-based colored paint to reach 10-20 mu m to form an uncured water-based colored paint coating film; then drying and dehydrating for 5-10 minutes at the temperature of 60-90 ℃;

(4) spraying a varnish coating on the composite coating film obtained in the step (3) to enable the film thickness of the dried coating film to reach 30-50 mu m, and forming an uncured varnish coating film; then baking and reacting at 140-160 ℃ for 20-30 minutes to cure the color paint coating film and the varnish coating film together.

When the water-based colored paint provided by the invention is used, the thickness of a sprayed film can be 10-20 mu m, and the flash drying condition is 20-30 ℃ and 60-70% humidity for 5 min; the dehydration condition is 5-10min at 75-85 deg.C.

The technical solution of the present invention is described below with reference to some specific examples:

production example of aqueous polyurethane A

(1) Production of polyester polyols

In a reaction vessel equipped with a reflux cooling device having a reaction water outlet, a thermometer, a stirring device and a nitrogen inlet tube, the following raw materials were charged:

heating to 120 deg.C for dissolving, stirring, and heating to 160 deg.C. After maintaining 160 ℃ for 1 hour, the temperature was raised to 230 ℃ for 5 hours. The acid value is tested at fixed time in the heat preservation at 230 ℃ until the acid value of the resin reaches 1 mgKOH/g. Then cooling to below 80 ℃ to obtain the polyester polyol A with the acid value of 1mg KOH/g, the hydroxyl value of 129mgKOH/g and the number average molecular weight of about 1000.

(2) Synthesis of polyurethane

A reaction vessel equipped with a reflux cooling apparatus having a reaction outlet, a thermometer, a stirring apparatus and a nitrogen inlet tube was charged with the following raw materials.

The temperature was raised to 80 ℃ with continuous stirring. After 80 ℃ had been reached, isophorone diisocyanate (15.5 parts) was added and the reaction was continued at 80 ℃ until the absorption peak of the isocyanate groups in the IR spectrum disappeared.

Then cooling to 50 ℃, adding dimethylethanolamine (1.2 parts) for neutralization, adding deionized water (75.6 parts) after neutralization, keeping the temperature for 1 hour, and cooling to 40 ℃ to obtain the waterborne polyurethane A with the solid content of 35.0%, the hydroxyl value of 140mgKOH/g and the number average molecular weight of 3000 or so.

Preparation example of acrylic emulsion B

The specific manufacturing steps are as follows:

(1) a reaction vessel equipped with a reflux cooling device, a thermometer, a stirring device and a nitrogen inlet tube was charged with the following raw materials, gradually heated to 80. + -. 2 ℃,

120 portions of pure water

SR-10 anionic emulsifier (Ediko Co., Ltd.) 0.05 part.

(2) In another container adding the following components

35 portions of pure water

NE-10 nonionic emulsifier (Ediko Co., Ltd.) 0.8 part.

The components are gradually added into the mixture under the low-speed stirring of 200-400rpm to prepare a premixed solution,

this part is the composition of the acrylic emulsion core part.

(3) 0.1 part of initiator ammonium persulfate is added into the reaction vessel in (1). And then, gradually and constantly adding the premixed solution obtained in the step (2) into the reaction vessel in the step (1) within the time of 100-120 minutes. Gradually adding 0.2 part of initiator ammonium persulfate into the reaction vessel within 100-120 minutes synchronously.

(4) And (4) after the raw materials in the step (3) are added, continuously preserving the heat for 60 minutes at the temperature of 80 +/-2 ℃.

(5) And (4) adding 0.3 part of dimethylethanolamine into the reaction vessel 10 minutes before the heat preservation in the step (4) is finished to finish the neutralization.

(6) In another vessel the following ingredients were added:

13 parts of pure water

NE-10 nonionic emulsifier (Ediko Co., Ltd.) 0.9 part.

10-25 parts of ethyl acrylate

1-8 parts of methacrylic acid

4-10 parts of hydroxyethyl methacrylate.

The part is the composition of the acrylic emulsion shell part, and the Tg and the hydroxyl value of the acrylic resin are slightly adjusted by the variation of acrylic monomers within a certain range.

(7) And (4) after the heat preservation in the step (4) is finished, gradually adding the premixed solution in the step (6) into the reaction container in the step (1) at a constant speed within 60-80 minutes. After the addition, the temperature is kept for 120 minutes at 80 plus or minus 2 ℃.

(8) And after the heat preservation is finished, cooling to room temperature to obtain the milky acrylic resin B dispersed in the water. The acrylic emulsion has Tg (glass transition temperature) of 30-60 ℃, hydroxyl value of 80-150mg KOH/g and solid content of 30%.

Production example and comparative example of Water-based colored paint

Production examples 1-2 and comparative examples 1-6 of Water-based color paints containing Effect pigments

The raw materials, parts and sources of the coatings prepared in production examples 1 to 2 and comparative examples 1 to 6 are shown in Table 1.

TABLE 1 raw materials, parts and sources of coatings prepared in production examples 1-2 and comparative examples 1-6

The preparation of an effect pigment-containing aqueous color paint is described below in preparation example 1.

Production example 1

The preparation process of the water-based colored paint in the manufacturing example 1 comprises the following steps:

firstly, adding ALUMINUM PASTE LX-318S and A-903K-SP into an auxiliary cylinder a, then adding ethylene glycol isophorous ether and isophorous alcohol to dissolve the mixture, and stirring for 10 min; then adding ACS-1016, Surfynol-440, BYK-345 and DISPERBYK-182 in sequence, and stirring for 20min to obtain a mixture.

Secondly, sequentially adding A, NP-6100 waterborne polyurethane and CYMEL 250 into the master cylinder b, and stirring for 30 min; and adding CYMEL 370N, BYK-011 in sequence, stirring for 15min, and adjusting pH to 7.8-8.5 with 10% aqueous solution of dimethylethanolamine.

Thirdly, adding the acrylic emulsion B and the ADEKANOL UH-814N into the master cylinder B in sequence, and stirring for 30 min; then, ACW-1011 and AR-2000(T) G314/BF-21PASTE UDP were added in this order and stirred for 20 min.

And fourthly, adding the mixture in the auxiliary cylinder a into the main cylinder b while stirring, washing the auxiliary cylinder a by using the glycol isophorous ether, merging the washing liquid into the main cylinder b, and stirring for 15 min.

And fifthly, adding pure water, RHEOVIS AS 1130 auxiliary agent, ethylene glycol monobutyl ether and 10% aqueous solution of dimethylethanolamine into the main cylinder b while stirring, and stirring for 30 min.

Sixthly, adjusting the pH value to 7.8-8.5 by using a 10% aqueous solution of dimethylethanolamine; and regulating the viscosity of the B-type paint to be 3000-4500 at 6rpm by using pure water to obtain the water-based colored paint.

Production example 2

The manufacturing method was the same as in manufacturing example 1. Except that AQUACER 507 wax emulsion was added in the fifth step.

Comparative example 1

The manufacturing method was the same as in manufacturing example 1. Except that in the second step the aqueous polyurethane a WAs replaced with a non-volatile equivalent amount of DAOTAN VTW 6462/36 WA.

Comparative example 2

The manufacturing method was the same as in manufacturing example 1. Except that in the second step the aqueous polyurethane a WAs replaced with a non-volatile equivalent amount of DAOTAN VTW 6462/36WA and in the fifth step AQUACER 507 wax emulsion WAs added.

Comparative example 3

The manufacturing method was the same as in manufacturing example 1. Except that acrylic emulsion B was replaced with a non-volatile equivalent amount of Luhydran S938T in the third step.

Comparative example 4

The manufacturing method was the same as in manufacturing example 1. Except that acrylic emulsion B was replaced with a non-volatile equivalent of Luhydran S938T in the third step and AQUACER 507 wax emulsion was added in the fifth step.

Comparative example 5

The manufacturing method was the same as in manufacturing example 1. Except that in the second step aqueous polyurethane a WAs replaced with a non-volatile equivalent amount of DAOTAN VTW 6462/36WA and in the third step acrylic emulsion B WAs replaced with a non-volatile equivalent amount of Luhydran S938T.

Comparative example 6

The manufacturing method was the same as in manufacturing example 1. Except that in the second step the aqueous polyurethane a WAs replaced with a non-volatile equivalent amount of DAOTAN VTW 6462/36WA, in the third step the acrylic emulsion B WAs replaced with a non-volatile equivalent amount of Luhydran S938T, and in the fifth step AQUACER 507 wax emulsion WAs added.

Production examples 3 to 4 and comparative examples 7 to 12 of effect pigment-free waterborne paints

The raw materials, parts and sources of the coatings prepared in production examples 3 to 4 and comparative examples 7 to 12 are shown in Table 2.

TABLE 2 raw materials, parts and sources of coatings prepared in production examples 3-4 and comparative examples 7-12

The preparation of an aqueous paint not containing effect pigments is described below in the context of preparation example 3.

Production example 3

The preparation of the effect pigment-free waterborne color paint of preparation example 3 comprises the following steps:

step one, adding ethylene glycol isobutrol and isobutrol into an auxiliary cylinder a, and stirring for 5 min; then adding ACS-1016, Surfynol-440, BYK-345 and DISPERBYK-182 in sequence, and stirring for 10min to obtain a mixture.

Secondly, sequentially adding waterborne polyurethane, NP-6100 and CYMEL 250 into the main cylinder b, and stirring for 30 min; and sequentially adding CYMEL 370N, BYK-011, stirring for 15min, and adjusting pH to 7.8-8.5 with 10% aqueous solution of dimethylethanolamine.

Thirdly, adding the acrylic emulsion B and the ADEKANOL UH-814N into the master cylinder B in sequence, and stirring for 30 min; then, ACW-1011 and AR 2000(T)5000BLACK UDP were added in this order and stirred for 20 min.

Sixthly, adjusting the pH value to 7.8-8.5 by using a 10% aqueous solution of dimethylethanolamine; and adjusting the viscosity of the B-type paint to 2500-6000 at 6rpm by using pure water to obtain the water-based colored paint.

Production example 4

The manufacturing method was the same as in manufacturing example 3. Except that AQUACER 507 wax emulsion was added in the fifth step.

Comparative example 7

The manufacturing method was the same as in manufacturing example 3. Except that in the second step the aqueous polyurethane a WAs replaced with a non-volatile equivalent amount of DAOTAN VTW 6462/36 WA.

Comparative example 8

The manufacturing method was the same as in manufacturing example 3. Except that in the second step the aqueous polyurethane a WAs replaced with a non-volatile equivalent amount of DAOTAN VTW 6462/36WA and in the fifth step AQUACER 507 wax emulsion WAs added.

Comparative example 9

The manufacturing method was the same as in manufacturing example 3. Except that acrylic emulsion B was replaced with a non-volatile equivalent amount of Luhydran S938T in the third step.

Comparative example 10

The manufacturing method was the same as in manufacturing example 3. Except that acrylic emulsion B was replaced with a non-volatile equivalent of Luhydran S938T in the third step and AQUACER 507 wax emulsion was added in the fifth step.

Comparative example 11

The manufacturing method was the same as in manufacturing example 3. Except that in the second step aqueous polyurethane a WAs replaced with a non-volatile equivalent amount of DAOTAN VTW 6462/36WA and in the third step acrylic emulsion B WAs replaced with a non-volatile equivalent amount of Luhydran S938T.

Comparative example 12

The manufacturing method was the same as in manufacturing example 3. Except that in the second step the aqueous polyurethane a WAs replaced with a non-volatile equivalent amount of DAOTAN VTW 6462/36WA, in the third step the acrylic emulsion B WAs replaced with a non-volatile equivalent amount of Luhydran S938T, and in the fifth step AQUACER 507 wax emulsion WAs added.

Example 1

Coating film prepared by three-coating and two-baking process

An electrodeposition coating PN-310 (cationic electrodeposition coating manufactured by Nippon paint) was applied to a zinc phosphate-treated passivated steel sheet until the dry coating film thickness became 20 μm, and then the steel sheet was cured by heating at 160 ℃ for 30 minutes and then cooling to form a cured electrodeposition coating film. All paint making examples and comparative examples were then spray coated on the electrocoat film using the three coat two bake process described above. The other coatings involved are listed in Table-3 below. Then, each index test was performed according to the contents of Table-4.

Table 3 information on other coatings used in the coating film (three coat two bake)

TABLE 4 film coating Performance test index

The water-based colored paint containing the effect paint in the manufacturing examples 1-2 and the comparative examples 1-6 was sprayed to form a film in a three-coat two-bake process, and various indexes were measured as shown in table 4, and the obtained results are shown in table 5.

Table 5 contains the film properties of the aqueous paints (containing effect pigments, three-coat two-bake process) of preparation examples 1-2 and comparative examples 1-6

The results in Table 5 show that only when the waterborne color paint contains the waterborne polyurethane A and the acrylic emulsion B which are prepared by the invention, the hydroxyl and other functional groups in the system, such as carboxyl, generate reversible acting force networks, such as hydrogen bonds, and the like, and the appearance leveling is better during construction. After wet spraying and wet coating of the solvent type varnish, the phenomenon of mixing of components in the varnish and the colored varnish is effectively avoided, and better distinctness of image is obtained. And simultaneously, a better effect pigment flickering effect is obtained. The same effect is difficult to achieve by using only the aqueous polyurethane A or the acrylic emulsion B alone. On the other hand, when these two resins are used together, the appearance and color are very excellent, and the addition of other additives (in this case, wax emulsion) cannot be further improved. When these two resins are not used simultaneously, the addition of the wax emulsion can improve the appearance and color effect, but does not achieve the excellent level in the coating production example, and at the same time, adversely affects the properties such as water resistance.

Wherein, the manufacturing examples 3 to 4 and the comparative examples 7 to 12 do not contain the effect paint, the water-based colored paint containing the pigment black is sprayed under the three-coating and two-baking process to prepare a film, each index is detected according to the table 4, and the obtained result is shown in the table 6.

Table 6 contains the film properties of the aqueous color paints (pigmented Black, three coat two bake Process) of preparation examples 3-4 and comparative examples 7-12

Table 6 the results show that the performance indexes of the aqueous paints containing pigment black, which were prepared in manufacturing examples 3 to 4 and comparative examples 7 to 12 without effect pigments, sprayed under the three-coat two-bake process, were consistent with those of the paints containing effect pigments shown in table 5. When the aqueous polyurethane A and the acrylic acid B are used together, the appearance is optimal. And the factor color black paint is more sensitive to the mixed layer, and the use of the wax emulsion has no obvious effect on improving the appearance.

Example 2

Coating film prepared by three-coating one-baking process

An electrodeposition coating PN-310 (cationic electrodeposition coating manufactured by Nippon paint) was applied to a zinc phosphate-treated passivated steel sheet until the dry coating film thickness became 20 μm, and then the steel sheet was cured by heating at 160 ℃ for 30 minutes and then cooling to form a cured electrodeposition coating film. All paint making examples and comparative examples were then spray coated on the electrocoat film using the three coat one bake process described above. The other coatings involved are listed in Table-7 below. Then, each index test was performed according to the contents of Table-4. The results are reported in Table-8 and Table-9.

Table 7 additional paint information used in the paint film (three coats one bake)

The aqueous colored paint containing the effect paint in the manufacturing examples 1 to 2 and the comparative examples 1 to 6 was sprayed to form a film by the three-coat one-bake process, and the indexes were measured as shown in table 4, and the results are shown in table 8.

Table 8 contains the film properties of the aqueous color paints (containing effect pigments, three coat one bake process) of production examples 1-2 and comparative examples 1-6

The results in Table 8 show that the appearance and color effect are more advantageous only when the aqueous polyurethane A prepared according to the invention and the acrylic emulsion B are included in an aqueous pigmented paint at the same time. Meanwhile, the thickness of the middle coating is thinned due to the three-coating one-baking process. The additives exemplified by wax emulsion and the like are less effective in improving appearance and more adversely affect performance (production example 2).

Wherein, the manufacturing examples 3 to 4 and the comparative examples 7 to 12 do not contain the effect paint, the water-based colored paint containing the pigment black is sprayed and prepared into a film under the three-coating and one-baking process, each index is detected according to the table 4, and the obtained result is shown in the table 9.

Table 9 contains the film properties of the aqueous color paints (pigmented Black, three coat one bake Process) of preparation examples 3-4 and comparative examples 7-12

The results in Table 9 also show that the aqueous paints of preparation examples 3 to 4 and comparative examples 7 to 12 which do not contain effect pigments, but which contain pigment black, when sprayed in a three-coat two-bake process, have index properties which are in accordance with the tendency of the paints containing effect pigments shown in Table 8. Only when the aqueous colored paint contains both the aqueous polyurethane A prepared by the invention and the acrylic emulsion B, the appearance and the color effect show more advantages. Meanwhile, the thickness of the middle coating is thinned due to the three-coating one-baking process. The additives exemplified by wax emulsion and the like are less effective in improving appearance and more adversely affect performance (production example 2). And the factor color black paint is more sensitive to the mixed layer, and the use of the wax emulsion has no obvious effect on improving the appearance.

Example 3

Coating film (different varnish) prepared by three-coating one-baking process

The wet spraying condition of the three-coating one-drying process is more severe, so the spraying method is selected. The procedure was as in example-2, with different varnishes and the appearance was examined. The matching coating is shown in the table-10.

Table 10 information on other coatings used in the coating film of example 3 (three coats and one bake)

The effect pigment-containing aqueous base paints of production example 1 and comparative examples 1, 3 and 5, and the effect pigment-free aqueous base paints of production example 3 and comparative examples 7, 9 and 11 were matched with different varnishes under a three-coat one-bake process to prepare coating films, and the properties thereof were tested, as shown in table 11.

TABLE 11 Properties of coating films obtained by matching aqueous color paints with different varnishes (three coats and one bake)

From this result, different varnishes were matched to the same color paint, giving different appearance results. Although some data were also obtained when the aqueous polyurethane A and the acrylic emulsion B were not used simultaneously. It is worth mentioning that only coating production example-1 using these two resins simultaneously exhibited appearance stability under different varnish conditions.

Example 4

Detection of workability

The perforated steel sheet shown in fig. 1 was coated using the three coat one bake process mentioned above. The middle coat and the clear coat were the same as in example 2 and were normally sprayed. When the aqueous colored paint is sprayed, the spraying direction is from the right to the left of the test panel A, the traveling speed of the spray gun is changed from slow to fast, and thus a coating with a thickness from thick to thin is formed. And measuring the film thickness of the composite coating at the position of 0.5cm from the sagging to the lower edge of the round hole as the sagging limit film thickness of the coating. The first pinhole appears as the pinhole limit of the coating. The matched coating is shown in the table-12. The results are summarized in Table-13.

Table 12 example 4 additional paint information (three coats one bake) used in the paint film

Coating films were prepared and tested for properties as shown in table 13 by the spray method of example 4 using the effect pigment-containing aqueous color paints of production example 1 and comparative examples 1, 3 and 5, and the effect pigment-free aqueous color paints of production example 3 and comparative examples 7, 9 and 11, respectively, in a three-coat one-bake process.

TABLE 13 Properties of the coating films obtained with the aqueous paints by the spraying method described in example 4 (three coats one bake)

From the results, although a single index of some comparative examples under specific conditions can reach a maximum. In summary, the examples using both the aqueous polyurethane A and the acrylic emulsion B were the best in workability by matching different varnishes and examining the pinhole limit and the sagging limit. Compared with appearance data, the data gap of the workability is not as obvious as the appearance. The small difference of the construction data can bring huge influence on the risk caused by the defect of the paint film in the actual spraying time of an automobile host factory. In conclusion, after the resin is improved, the novel water-based colored paint with the synergistic effect can bring obvious improvement on the aspects of appearance and constructability, accelerate the water-based process of industrial paint in China and help the coating engineering to save energy and reduce emission, thereby generating greater economic benefit.

It should be understood that the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention, and it will be obvious to those skilled in the art that other variations or modifications may be made on the basis of the above description, and all embodiments may not be exhaustive, and all obvious variations or modifications may be included within the scope of the present invention.

Claims

1. The water-based colored paint suitable for the wet spraying process is characterized by comprising the following components in parts by weight:

wherein the number average molecular weight of the waterborne polyurethane is 1000-5000, and the hydroxyl value is 100-200 mgKOH/g; the glass transition temperature of the acrylic emulsion with the core-shell structure is 30-60 ℃, and the hydroxyl value is 80-150mg KOH/g;

wherein the preparation process of the waterborne polyurethane comprises the following steps: uniformly mixing polyester polyol, dihydric alcohol, trihydric alcohol, a compound containing an anionic functional group and a catalyst, heating to 60-120 ℃, adding non-cyclic aliphatic diisocyanate or non-cyclic aliphatic diisocyanate polymer or alicyclic diisocyanate polymer, and reacting at constant temperature; after the reaction is finished, cooling to 30-50 ℃ for amine neutralization; after neutralization, adding deionized water, and cooling to 20-40 ℃ to obtain waterborne polyurethane;

the number average molecular weight of the polyester polyol is 500-2000, the acid value in the solid content is less than 5, and the hydroxyl value is 100-300mg KOH/g; the compound containing the anionic functional group is a compound having a functionality of not less than 2 and capable of reacting with isocyanate;

the preparation process of the acrylic emulsion with the core-shell structure comprises the following steps:

2. The aqueous colored paint according to claim 1, wherein the pH of the aqueous colored paint is 8.0 to 8.5.

3. The water-based colored paint according to claim 1, wherein the mass ratio of non-volatile components in the water-based colored paint is 20-30%.

4. The aqueous colored paint according to claim 1, wherein the B-type viscosity of the aqueous colored paint is 3000 mPa-s to 4500 mPa-s.

5. The aqueous colored paint according to claim 1, wherein the mass ratio of the polyester polyol, the diol, the triol, the compound containing an anionic functional group, the catalyst and the non-cyclic aliphatic diisocyanate used in the preparation of the aqueous polyurethane is as follows: (10-30): (0.5-5): (0.5-5): (0.5-5): (0.01-0.1): (5-20).

6. The water-based paint according to claim 1, wherein the effect pigment is at least one selected from the group consisting of a scale-shaped aluminum powder, a resin-coated aluminum powder, a coated colored aluminum powder, a natural mica-type pearl powder, a synthetic mica-type pearl powder and a coated pearl powder.

7. The aqueous colored paint according to claim 1, wherein the auxiliary agent is at least one selected from a defoaming agent, a leveling agent, a dispersing agent, and a thickener.

8. Use of an aqueous pigmented paint according to any of claims 1 to 7 for wet-on-wet processes wherein the aqueous pigmented paint is used in forming a coating on a substrate using a three-coat two-bake process or a three-coat one-bake process.