CN110054979A - A kind of aqueous coating for plastic and its preparation method and application - Google Patents

Abstract

The invention discloses an aqueous coating for plastics and a preparation method and application thereof. The coating comprises the following components in parts by mass: 30-65 parts of an alcoholic hydroxyl-containing aqueous polyester resin dispersion, 8 parts of deionized water -35 parts, 1-20 parts of pigments and fillers, 10-20 parts of hydrophilically modified polyisocyanates, 2-8 parts of film-forming auxiliary mixed solvent, 0.1-1 part of reinforcing agent and 1-2 parts of other auxiliaries. The plastic water-based paint can form a dense paint film with a network structure, and the paint film has a large number of urethane groups, urea groups and hydrogen bonds, so that the adhesion between the paint film and the plastic surface layer, wear resistance, liquid medium resistance performance better. The preparation method can effectively improve the reaction degree of the alcoholic hydroxyl group-containing water-based polyester resin and the hydrophilic modified polyisocyanate, and promote the performance of the paint film. The preparation method is simple, uses deionized water as a solvent, reduces VOC emission, can effectively improve the working environment of painting operators, reduce environmental pollution, and can effectively promote the coordinated development of environment and economy.

Description

A kind of plastic water-based paint and its preparation method and use

technical field

The invention relates to the technical field of water-based coatings, in particular to a water-based coating for plastics and a preparation method and application thereof.

Background technique

Coatings for plastics refer to coatings applied to the surface of plastic materials, which have the functions of decoration, protection, and specific functions, and are of great significance to improving the weather resistance of plastic products and their applications. Compared with solvent-based coatings for plastics, water-based coatings for plastics have the advantages of reducing volatile organic compound (VOC) emissions and reducing environmental pollution. However, the water-based coatings for plastics are easily scratched, have poor resistance to acid and alkaline media, and have insufficient adhesion, which limit the application of the existing water-based coatings for plastics. Therefore, the research and development of low-VOC water-based coatings for plastics that are resistant to friction and various liquid media has become a research hotspot, and has received attention from countries all over the world.

At present, water-based coatings for plastics mainly include water-based acrylate coatings, water-based epoxy coatings, water-based polyurethane coatings, and water-based polyurethane acrylate coatings. Since the paint film formed by the polyurethane coating contains a large number of urethane bonds, and the hydrogen bonds are easily formed between the molecules, the formation and breaking of the hydrogen bonds make the polyurethane coating film have a certain strength and toughness, so it not only has excellent friction resistance It also has excellent resistance to liquid media, such as acid resistance, alkali resistance, salt resistance, and water resistance. Water-based polyurethane coatings have the advantages of both water-based coatings and polyurethane coatings, and will be widely used in the plastic coating industry.

Waterborne polyurethane coatings are divided into one-component waterborne polyurethane coatings and two-component waterborne polyurethane coatings. Relatively speaking, two-component waterborne polyurethane coatings have better performance. Two-component waterborne polyurethane coating is composed of waterborne polyol resin and hydrophilic modified polyisocyanate curing agent, and its performance is mainly determined by waterborne polyol resin and hydrophilic modified polyisocyanate curing agent. And the diversity and adjustability of water-based polyol resin can meet the needs of different plastic coating. There have been many reports on water-based polyurethane coatings applied to plastics in China. For example, CN 106833360 A discloses a water-resistant and wear-resistant plastic coating and a preparation method thereof. CN 105733390 A discloses a water-based two-component transparent topcoat for PP plastics and its preparation method. The preparation method and CN 104263230 A disclose an aqueous plastic coating and a preparation method thereof, and the like. However, there is no report on the water-based polyurethane coating applied to the surface of plastics that has both abrasion resistance, good adhesion and resistance to liquid media (acid, alkali, salt or organic solvent). Therefore, it is of practical significance to prepare an aqueous coating for plastics with excellent friction resistance and good resistance to liquid media.

SUMMARY OF THE INVENTION

In order to improve the deficiencies of the prior art, the purpose of the present invention is to provide a water-based coating for plastics and a preparation method and application thereof. The paint film prepared by the coating has the properties of good adhesion, friction resistance and resistance to various liquid media. The excellent friction resistance of the paint film lies in the use of multifunctional polyester resin with good toughness as the connecting material; the excellent adhesion and resistance to various liquid media of the paint film lies in the use of a reinforcing agent and a film-forming aid mixed. Solvent and control of its dosage can improve the internal crosslinking degree of the coating system and prolong the open time of the coating film formation process, so as to avoid the surface defects of the paint film such as pinholes and porosity caused by excessive crosslinking.

The object of the invention is to be achieved through the following technical solutions:

An aqueous coating for plastics, comprising the following components in parts by mass: 30-65 parts of alcoholic hydroxyl-containing aqueous polyester resin dispersion, 8-35 parts of deionized water, 1-20 parts of pigments and fillers, 10-20 parts of water-modified polyisocyanate, 2-8 parts of film-forming auxiliary mixed solvent, 0.1-1 part of reinforcing agent and 1-2 parts of other auxiliary agents.

Further, the water-based paint comprises the following components in parts by mass: 40-65 parts of alcoholic hydroxyl-containing water-based polyester resin dispersion, 8-25 parts of deionized water, 5-20 parts of pigments and fillers, 10-16 parts of water-modified polyisocyanate, 5-8 parts of film-forming auxiliary mixed solvent, 0.4-1 part of reinforcing agent and 1-2 parts of other auxiliary agents.

In the present invention, the amount of the hydrophilically modified polyisocyanate used is 10-20 (mass) parts, preferably 10-16 (mass) parts; the increase in the amount of the hydrophilically modified polyisocyanate can improve the cross-linking of the coating degree, thereby enhancing the adhesion and resistance to liquid media of the paint film.

Further, the mass fraction ratio of the hydrophilic modified polyisocyanate and the film-forming auxiliary mixed solvent is (1.5-2.5):1, for example, 2:1. Selecting such a range can avoid surface defects of the paint film caused by excessive cross-linking, such as pinholes and pores.

Further, the solid content of the alcoholic hydroxyl group-containing aqueous polyester resin dispersion is 20-75 wt %, the viscosity is 200-1000 mPa.s, and the hydroxyl value is 20-100 mg KOH/g.

Further, the pigments and fillers include pigments and/or fillers, and the pigments include water-based color pastes; the fillers are any fillers for coatings known in the art, such as titanium dioxide, calcium carbonate, montmorillonite, gas phase At least one of silica, talc, and bentonite. The water-based color paste is mainly used as a colorant, and the fillers such as titanium dioxide, calcium carbonate, montmorillonite, fumed silica, talc, bentonite and the like are mainly used for thickening, reinforcing and filling.

Further, the water-based color paste is a color paste for water-based systems, such as at least one of water-based iron red paste, water-based carbon black paste, water-based white paste, water-based bright red paste, water-based iron yellow paste, and water-based phthalocyanine blue paste. A sort of.

Further, the water-based color paste uses water as the dispersing medium, and optionally adds an auxiliary agent that can promote the uniform dispersion of the pigment to disperse the pigment into a uniform emulsion.

Further, the hydrophilically modified polyisocyanates include hydrophilically modified aliphatic polyisocyanates or hydrophilically modified aromatic polyisocyanates.

Further, the film-forming auxiliary mixed solvent includes the following components in parts by mass: 1-5 parts of propylene glycol methyl ether acetate and 1-4 parts of dipropylene glycol dimethyl ether.

Further, the film-forming auxiliary mixed solvent also includes the following components in parts by mass: 0-2 parts of dipropylene glycol monomethyl ether.

Further, the reinforcing agent is a silica sol-type reinforcing agent, which can improve the hardness and liquid medium resistance of the paint film by forming a network structure in the paint film to increase its compactness.

Further, the other adjuvants include wetting agents (such as anionic surfactant-type wetting agents), defoaming agents (such as silicone-based defoaming agents), leveling agents (such as polyether-modified polydimethylsilicones) One or at least two of oxane-type leveling agents) and thickeners (such as associative thickeners).

In the present invention, by adding a wetting agent, the wetting and dispersing among the components of the water-based plastic coating can be increased, so that the mixing can be more uniform, and the bonding force between the water-based plastic coating and the substrate can be improved. By adding a defoamer, the foam in the water-based plastic coating can be reduced, and defects such as shrinkage craters during the coating construction and pinholes after the paint film is dried can be avoided. By adding a leveling agent, the water-based plastic coating can form a flat, smooth and uniform coating film during the drying and film-forming process. By adding thickeners, the viscosity of the coating can be adjusted to meet different construction conditions.

Further, the other adjuvants include the following components in parts by mass: 0.1-0.6 part of wetting agent, 0.1-0.6 part of defoamer, 0.2-1.2 part of leveling agent, and 0-0.5 part of thickener .

Further, the viscosity of the water-based plastic coating tested at 25°C by the coating-4 cup method is 23-40s.

The present invention also provides the preparation method of the above-mentioned plastic water-based paint, the method comprises the following steps:

Mix the alcoholic hydroxyl-containing water-based polyester resin dispersion, deionized water, pigments and fillers, hydrophilically modified polyisocyanate, reinforcing agent, film-forming auxiliary mixed solvent and other auxiliary agents according to the stated mass fractions. The water-based paint for plastic is prepared.

Further, the method includes the steps:

a) Mix and stir the alcoholic hydroxyl-containing aqueous polyester resin dispersion, deionized water, pigments and fillers, reinforcing agent, and optionally wetting agent and defoaming agent according to the mass fractions to obtain Group A Minute;

b) Mixing the hydrophilic modified polyisocyanate and the film-forming aid mixed solvent according to the mass fraction, mixing and stirring evenly, to obtain component B;

c) Mix the A component of step a) and the B component of step b) to obtain a mixed system; optionally add a leveling agent and a thickening agent; prepare the water-based plastic coating.

It has been found that, when preparing the coating, a one-step mixing method can be adopted; it is also possible to use the water-based polyester resin dispersion containing alcoholic hydroxyl groups and the hydrophilically modified polyisocyanate to first prepare the A component and the B component, respectively, Then mix the two. The latter method has the following advantages: when the hydrophilic modified polyisocyanate and the film-forming aid mixed solvent are first formulated into component B, the viscosity of the hydrophilic modified polyisocyanate can be reduced, and then the viscosity of the hydrophilic modified polyisocyanate can be reduced. The mixing of the A component of the hydroxyl-containing aqueous polyester resin dispersion can effectively promote its reaction with the hydroxyl-containing aqueous polyester resin dispersion.

Further, the stirring speed is 200-400r/min.

Further, the method further comprises filtering the water-based plastic coating of step c) through a 200-mesh mesh cloth to prepare the final water-based plastic coating.

The present invention also provides the use of the above-mentioned water-based paint for plastics, which is used for preparing paint films on the surface of plastics.

The present invention also provides a composite material, comprising a plastic layer and a paint film layer on at least one surface of the plastic, wherein the paint film layer is obtained by coating the above-mentioned plastic with water-based paint.

Wherein, the volatile organic compound (VOC) content in the paint film is less than 110g/L.

Further, the paint film has good adhesion, abrasion resistance and liquid medium resistance between the paint film and the plastic surface layer.

Further, the wear resistance includes but is not limited to paper tape friction resistance, rubber friction resistance and alcohol friction resistance, etc.; the liquid medium resistance includes but is not limited to water resistance, organic solvent resistance, acid and alkali resistance and salt resistance, etc. Wait.

Further, the paint film satisfies at least one of the following characteristics:

(1) Resistant to paper tape rubbing more than 100 times;

(2) Rubber friction resistance is more than 500 times;

(3) More than 500 times of alcohol rubbing resistance;

(4) The adhesion reaches the grade 0 standard;

(5) The pencil hardness is not lower than HB;

(6) Resistant to liquid medium 50g/LH ₂ SO ₄ aqueous solution, 50g/L KOH aqueous solution, 50g/L NaCl aqueous solution and deionized water for more than 15 days without abnormal change on the surface of the paint film.

The abnormal changes include, but are not limited to, defects such as dents, blistering, cracking, peeling, cracking, peeling off, exposed substrates, or a different color base coat in the paint film.

Beneficial effects of the present invention:

1. The water-based paint for plastics of the present invention is a curing agent with a hydrophilic modified polyisocyanate, which is cross-linked with the water-based polyester resin containing alcoholic hydroxyl to form a dense paint film of a network structure, and the paint film has a large amount of urethane. In this way, the internal cross-linking degree of the coating system is improved, and the open time of the coating film-forming process is prolonged, so as to avoid surface defects such as pinholes and porosity caused by excessive cross-linking. Adhesion between paint film and plastic surface layer, wear resistance (paper tape friction resistance, rubber friction resistance, alcohol friction resistance), liquid medium resistance (water resistance, organic solvent resistance (such as ethanol), acid and alkali resistance (such as H ₂ SO ₄ ) , KOH), salt resistance (such as NaCl)) performance is better.

2. A certain amount of a reinforcing agent and a film-forming auxiliary mixed solvent is used in the water-based plastic paint of the present invention, so that the paint film has excellent adhesion and resistance to various liquid media. The main reason is that the use of reinforcing agent and film-forming aid mixed solvent and controlling the amount of it can improve the internal cross-linking degree of the coating system and prolong the opening time of the coating film-forming process, so as to avoid the surface defects of the paint film caused by excessive cross-linking such as pinholes, pores and other phenomena, so that the paint film has excellent adhesion and resistance to various liquid media.

3. The volatile organic content in the paint film prepared by the water-based plastic coating of the present invention is less than 110g/L, and its friction resistance is: paper tape friction resistance more than 100 times, rubber friction resistance more than 500 times, alcohol friction resistance 500 times The paint film surface is resistant to liquid media such as 50g/LH ₂ SO ₄ aqueous solution, 50g/L KOH aqueous solution, 50g/L NaCl aqueous solution, and deionized water for more than 15 days. No unusual changes.

4. The preparation method of the present invention can effectively improve the reaction degree of the alcoholic hydroxyl group-containing water-based polyester resin and the hydrophilically modified polyisocyanate, and promote the performance of the paint film. The preparation method is simple, uses deionized water as a solvent, reduces VOC emission, can effectively improve the working environment of painting operators, reduce environmental pollution, and can effectively promote the coordinated development of environment and economy.

Detailed ways

The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the protection scope of the present invention. In addition, it should be understood that after reading the content disclosed in the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the protection scope defined by the present invention.

The experimental methods used in the following examples are conventional methods unless otherwise specified; the reagents, materials, etc. used in the following examples can be obtained from commercial sources unless otherwise specified.

Instrumentation and Testing:

The test method for the friction resistance of the paper tape is: load 175g, drag the paper tape to rub, and observe the degree of damage to the surface of the paint film. For details, refer to the American Society for Testing and Materials Standard ASTM F2357-2010;

The test method of the described rubber friction resistance is: use EF74 rubber, rub with a load of 500g, observe the degree of damage on the surface of the paint film, and specifically refer to the American Society for Testing and Materials standard ASTM D6279-2003 (2013);

The test method for the alcohol rubbing resistance is as follows: use alcohol with a concentration of 95%, rub two layers of gauze with a load of 500g, and observe the degree of damage on the surface of the paint film. For details, refer to the national standard "GB/T 23989-2009 Determination of Solvent Wipe Resistance of Paints" Law";

The described adhesion adopts the 100 grid test method, with specific reference to the national standard "GB/T9286-1998 Scratch Test of Paint and Varnish Films";

The test method of the described pencil hardness is: different pencil models carry a load of 500g on the pencil tip and draw 6.5mm forward, and observe the degree of damage on the surface of the paint film;

The test method for the resistance to liquid medium is as follows: after coating the paint film on the plastic substrate, immerse it in different solvents, and observe the degree of damage on the surface of the paint film;

The above pencil hardness and liquid medium resistance test refer to the test of the paint film for inorganic non-metallic surfaces in the national standard "Waterborne Polyurethane Coatings" HG/T 4761-2014.

In this embodiment, the viscosity test method of the coating is as follows: measuring the viscosity of the coating by coating-4 cup method, after filling the viscosity cup with the coating, use a metal or glass flat plate to scrape the cup, and scrape the excess test solution into the viscosity cup In the edge groove, place the receiving cup. Open the hole of the viscosity cup, let the paint flow out vertically at room temperature, start the stopwatch at the same time, the paint flows out into a line, stop the stopwatch when it is disconnected, and the measured time represents its conditional viscosity in seconds.

Example 1

This embodiment provides a water-based plastic coating, including the following components in mass fractions: an alcoholic hydroxyl-containing water-based polyester resin (a water-based polyester resin dispersion containing an alcoholic hydroxyl group is selected, the solid content is 40 wt %, and the viscosity is 1000mPa.s, hydroxyl value 20mg KOH/g) 64 parts, deionized water 8 parts, hydrophilic modified aliphatic polyisocyanate 14 parts, iron red paste 5 parts, PCS-S6 reinforcing agent 0.4 parts, GE/ 0.5 part of M wetting agent, 0.5 part of BYK-028 defoamer, 0.6 part of BYK-333 leveling agent, 5 parts of propylene glycol methyl ether acetate and 2 parts of dipropylene glycol dimethyl ether.

First, mix the water-based polyester resin containing alcoholic hydroxyl group, deionized water, iron red slurry, wetting agent and defoamer, and stir evenly. Then, the hydrophilic modified aliphatic polyisocyanate, propylene glycol methyl ether acetate, and dipropylene glycol dimethyl ether are stirred evenly, then the two are mixed, and finally a leveling agent is added. The purpose is to reduce the viscosity of the hydrophilically modified polyisocyanate and promote its reaction with the hydroxyl-containing aqueous polyester resin dispersion. After stirring evenly at a stirring speed of 200-400 r/min, the viscosity of the coating was detected to be 25 s, and filtered with a 200-mesh mesh cloth to prepare a water-based plastic coating.

Example 2

The present embodiment provides a water-based plastic coating and a preparation and construction method thereof, including the following components by mass fraction: an alcoholic hydroxyl-containing water-based polyester resin (a water-based polyester resin dispersion containing an alcoholic hydroxyl group is selected, and its solid content is 37wt%, viscosity is 1000mPa.s, hydroxyl value is 20mg KOH/g) 60 parts, deionized water 8 parts, hydrophilic modified aliphatic polyisocyanate 16 parts, carbon black paste 6 parts, PCS-S6 reinforcing agent 0.6 part, GE/M wetting agent 0.25 part, BYK-028 defoamer 0.25 part, BYK-333 leveling agent 0.5 part, PS-166 thickener 0.4 part, propylene glycol methyl ether acetate 5 parts, dipropylene glycol dipropylene glycol 3 parts of methyl ether.

First, mix the water-based polyester resin containing alcoholic hydroxyl group, deionized water, carbon black slurry, wetting agent and defoamer, and stir evenly. Then, the hydrophilic modified aliphatic polyisocyanate, propylene glycol methyl ether acetate and dipropylene glycol dimethyl ether are stirred evenly, then the two are mixed, and finally a leveling agent and a thickening agent are added. The purpose is to reduce the viscosity of the hydrophilically modified polyisocyanate and promote its reaction with the hydroxyl-containing aqueous polyester resin dispersion. After stirring evenly at a stirring speed of 200-400 r/min, the viscosity of the coating was detected to be 35 s, and filtered with a 200-mesh mesh cloth to prepare a water-based plastic coating.

Example 3

This embodiment provides a water-based plastic coating, including the following components in mass fractions: an alcoholic hydroxyl-containing water-based polyester resin (a water-based polyester resin dispersion containing an alcoholic hydroxyl group is selected, the solid content is 37 wt %, and the viscosity is 1000mPa.s, hydroxyl value 20mg KOH/g) 53 parts, 18 parts deionized water, 10 parts hydrophilic modified aliphatic polyisocyanate, 12 parts iron red paste, 0.5 part PCS-S6 reinforcing agent, GE/ 0.3 part of M wetting agent, 0.3 part of BYK-028 defoamer, 0.8 part of BYK-333 leveling agent, 0.1 part of PS-166 thickener, 3.5 part of propylene glycol methyl ether acetate, and 1.5 part of dipropylene glycol dimethyl ether.

First, mix the water-based polyester resin containing alcoholic hydroxyl group, deionized water, iron red slurry, wetting agent, thickener and defoamer, and stir evenly. Then, the hydrophilic modified aliphatic polyisocyanate, propylene glycol methyl ether acetate and dipropylene glycol dimethyl ether are stirred evenly, then the two are mixed, and finally a leveling agent and a thickening agent are added. The purpose is to reduce the viscosity of the hydrophilically modified polyisocyanate and promote its reaction with the hydroxyl-containing aqueous polyester resin dispersion. After stirring evenly at a stirring speed of 200-400 r/min, the viscosity of the coating was detected to be 23 s, and filtered with a 200-mesh mesh cloth to prepare a water-based plastic coating.

Comparative Example 1

This comparative example provides a water-based plastic coating, which includes the following components by mass fraction: an alcoholic hydroxyl-containing water-based polyester resin (a water-based polyester resin dispersion containing an alcoholic hydroxyl group is selected, and its solid content is 37wt% and the viscosity is 1000mPa.s, hydroxyl value 20mg KOH/g) 54.1 parts, deionized water 16.2 parts, hydrophilic modified aliphatic polyisocyanate 13.5 parts, iron red paste 8.4 parts, GE/M wetting agent 0.3 parts, BYK- 0.25 part of 028 defoamer, 0.5 part of BYK-333 leveling agent, 4 parts of propylene glycol methyl ether acetate, and 2.75 parts of dipropylene glycol dimethyl ether.

First, mix the water-based polyester resin containing alcoholic hydroxyl group, deionized water, iron red slurry, fumed silica, wetting agent, thickener and defoamer, and stir evenly. Then, the hydrophilic modified aliphatic polyisocyanate, propylene glycol methyl ether acetate and dipropylene glycol dimethyl ether are stirred evenly, then the two are mixed, and finally a leveling agent is added. The purpose is to reduce the viscosity of the hydrophilically modified polyisocyanate and promote its reaction with the hydroxyl-containing aqueous polyester resin dispersion. After stirring evenly at a stirring speed of 200-400 r/min, the viscosity of the coating was detected to be 16s, and filtered with a 200-mesh mesh cloth to prepare a water-based plastic coating.

Example 4

The water-based plastic coating prepared by Example 1-3 and Comparative Example 1 is coated on the surface of the plastic plate, specifically by the construction method of air spraying, and the coating of Example 1-3 is coated on PC, ABS, ABS/PC respectively On the surface of the plastic sheet, the paint of Comparative Example 1 was coated on the surface of the PC plastic sheet. Place in an oven at 60°C and bake for 8 hours to obtain a paint film. Observe and test the performance of the paint films on the surfaces of the above four plastic sheets. The specific results are shown in Table 1-Table 2.

Table 1 Test data table of friction resistance and adhesion of water-based plastic paint films of Examples 1-3 and Comparative Example 1

Table 2 The water-based plastic coatings prepared in Examples 1-3 are resistant to liquid medium data sheet

50g/L H₂SO₄ 50g/L KOH 50g/L NaCl Deionized water Film performance Example 1 15d 15d 30d 15d No abnormal change on the surface of the paint film Example 2 15d 15d 30d 15d No abnormal change on the surface of the paint film Example 3 15d 15d 30d 15d No abnormal change on the surface of the paint film

Comparing the water-based plastic coatings prepared in Examples 1-3 and Comparative Example 1, it can be seen from Table 1 and Table 2 that the water-based plastic coatings prepared in Examples 1-3 of the present invention have a volatile organic content of less than 110g/L , All kinds of friction resistance such as paper tape rubbing resistance more than 100 times, rubber rubbing resistance more than 500 times, alcohol rubbing resistance more than 500 times, adhesion reaching 0 grade standard, pencil hardness greater than or equal to HB; resistance to liquid media such as 50g/LH ₂ SO ₄ , 50g/L KOH, 50g/L NaCl, deionized water for more than 15 days, there is no abnormal change on the surface of the paint film, the abnormal changes include but are not limited to dents, blistering, cracking, peeling, and cracking of the paint film , peeling off, exposed substrate or other defects such as color base coating. When the paint film is applied, the wet film reaches 100μm and does not sag and form a good film. According to the calculation formula of VOC content, the VOCs of Examples 1-3 are 102g/L, 110g/L and 76g/L respectively, which greatly reduces the emission of paint VOCs. It is indicated that the water-based plastic coating prepared in this example belongs to a low-VOC green environment-friendly coating that is resistant to friction and liquid medium. However, the water-based plastic coating prepared in Comparative Example 1 has a low viscosity due to no thickener added, which leads to easy sagging during construction; in addition, due to the lack of reinforcing agent, the three friction resistance and adhesion properties of the paint film are reduced. worse than that of Examples 1-3.

The embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. A water-based paint for plastics, comprising the following components in parts by mass: 30-65 parts of alcoholic hydroxyl-containing water-based polyester resin dispersions, 8-35 parts of deionized water, 1-20 parts of pigments and fillers , 10-20 parts of hydrophilic modified polyisocyanate, 2-8 parts of film-forming auxiliary mixed solvent, 0.1-1 part of reinforcing agent and 1-2 parts of other auxiliary agents. 2. The water-based paint for plastics according to claim 1, wherein the water-based paint comprises the following components in parts by mass: 40-65 parts of alcoholic hydroxyl-containing water-based polyester resin dispersion, 8-25 parts of ionized water, 5-20 parts of pigments and fillers, 10-16 parts of hydrophilic modified polyisocyanate, 5-8 parts of film-forming auxiliary mixed solvent, 0.4-1 part of reinforcing agent and 1- 2 servings. 3. The water-based coating for plastics according to claim 1 or 2, characterized in that, the mass ratio of the hydrophilic modified polyisocyanate and the film-forming auxiliary mixed solvent is (1.5～2.5): 1, For example 2:1. Preferably, the solid content of the alcoholic hydroxyl group-containing aqueous polyester resin dispersion is 20-75 wt %, the viscosity is 200-1000 mPa.s, and the hydroxyl value is 20-100 mg KOH/g. Preferably, the film-forming auxiliary mixed solvent includes the following components in parts by mass: 1-5 parts of propylene glycol methyl ether acetate and 1-4 parts of dipropylene glycol dimethyl ether. Preferably, the film-forming auxiliary mixed solvent further includes the following components in parts by mass: 0-2 parts of dipropylene glycol monomethyl ether. Preferably, the pigments and fillers include pigments and/or fillers, and the pigments include aqueous color pastes; the fillers include at least one of titanium dioxide, calcium carbonate, montmorillonite, fumed silica, talc, and bentonite. Preferably, the water-based color paste includes at least one of water-based iron red paste, water-based carbon black paste, water-based white paste, water-based bright red paste, water-based iron yellow paste, and water-based phthalocyanine blue paste. 4. The water-based coating for plastics according to any one of claims 1-3, wherein the hydrophilically modified polyisocyanate comprises a hydrophilically modified aliphatic polyisocyanate or a hydrophilically modified aromatic polyisocyanate Polyisocyanates. 5 . The water-based plastic coating according to claim 1 , wherein the reinforcing agent is a silica sol-type reinforcing agent. 6 . Preferably, the other adjuvants include wetting agents (such as anionic surfactant-type wetting agents), defoaming agents (such as silicone-based defoaming agents), leveling agents (such as polyether-modified polydimethylsilicones) One or at least two of oxane-type leveling agents) and thickeners (such as associative thickeners). Preferably, the other adjuvants include the following components in parts by mass: 0.1-0.6 part of wetting agent, 0.1-0.6 part of defoamer, 0.2-1.2 part of leveling agent, and 0-0.5 part of thickener . Preferably, the viscosity of the water-based plastic coating is 23-40s tested at 25°C by the coating-4-cup method. 6. the preparation method of the plastic water-based paint described in any one of claim 1-5, is characterized in that, described method comprises the steps: Mix the alcoholic hydroxyl-containing water-based polyester resin dispersion, deionized water, pigments and fillers, hydrophilically modified polyisocyanate, reinforcing agent, film-forming auxiliary mixed solvent and other auxiliary agents according to the stated mass fractions. The water-based paint for plastic is prepared. 7. preparation method according to claim 6, is characterized in that, described method comprises the steps: a) Mix and stir the alcoholic hydroxyl-containing aqueous polyester resin dispersion, deionized water, pigments and fillers, reinforcing agent, and optionally wetting agent and defoaming agent according to the mass fractions to obtain Group A Minute; b) Mixing the hydrophilic modified polyisocyanate and the film-forming aid mixed solvent according to the mass fraction, mixing and stirring evenly, to obtain component B; c) Mix the A component of step a) and the B component of step b) to obtain a mixed system; optionally add a leveling agent and a thickening agent; prepare the water-based plastic coating. Preferably, the stirring speed is 200-400 r/min. Preferably, the method further comprises filtering the water-based plastic coating of step c) through a 200-mesh mesh cloth to prepare the final water-based plastic coating. 8. Use of the water-based coating for plastics according to any one of claims 1 to 5 for preparing paint films on plastic surfaces. 9. A composite material, characterized in that the composite material comprises a plastic layer and a paint film layer located on at least one surface of the plastic, and the paint film layer is made of the plastic according to any one of claims 1-5. Obtained by coating with water-based paint. 10 . The use according to claim 8 or the composite material according to claim 9 , wherein the content of volatile organic compounds in the paint film is less than 110 g/L. 11 . Preferably, the paint film and the plastic surface layer have good adhesion, abrasion resistance and liquid medium resistance. Preferably, the wear resistance includes but is not limited to paper tape friction resistance, rubber friction resistance, and alcohol friction resistance; the liquid medium resistance includes but is not limited to water resistance, organic solvent resistance, acid and alkali resistance, and salt resistance. Preferably, the paint film satisfies at least one of the following characteristics: (1) Resistant to paper tape rubbing more than 100 times; (2) Rubber friction resistance is more than 500 times; (3) More than 500 times of alcohol rubbing resistance; (4) The adhesion reaches the grade 0 standard; (5) The pencil hardness is not lower than HB; (6) Resistant to liquid medium 50g/LH ₂ SO ₄ aqueous solution, 50g/L KOH aqueous solution, 50g/L NaCl aqueous solution and deionized water for more than 15 days without abnormal change on the surface of the paint film.