Water-based colored paint for automobiles as well as preparation method and application of water-based colored paint

Abstract

The invention discloses water-based colored paint for automobiles as well as a preparation method and application of the water-based colored paint. The water-based colored paint is prepared from the following raw materials in parts by weight: 10 to 15 parts of water-based polyurethane dispersion, 5 to 9 parts of water-based hydroxy acrylic acid dispersion, 4 to 8 parts of melamine formaldehyde resin, 2 to 4 parts of color paste, 1 to 2 parts of aluminum paste, 2 to 3 parts of pearlescent pigment, 15 to 30 parts of deionized water and an organic solvent, the organic solvent comprises 6-8 parts of a high-boiling-point alcohol ether solvent and 2-4 parts of a swelling type solvent. The water-based colored paint for the automobile, provided by the invention, is generally used for coating an outer plate and an inner plate of an automobile body, and can be used for well improving the appearance of a coating film formed by spraying the inner plate and overcoming the problems of gloss loss and the like of the coating film when a static-free compressed air machine arm is used for spraying the inner plate of the automobile body.

Description

Technical Field

[0001] This invention relates to water-based paints for automobiles. More specifically, it relates to a water-based paint for automobiles, its preparation method, and its application. Background Technology

[0002] Cars, as essential means of transportation, are present in every aspect of our lives. To win over consumers and boost sales, car manufacturers are constantly redesigning their vehicles to appeal to a younger demographic. This extends beyond styling; they also opt for cool, metallic paints to add vibrancy. However, to reduce costs, automakers often use electrostatic-free compressed air robotic arms to paint the interior panels. This robotic arm method typically uses a high compressed air ratio and low rotary cup speed, resulting in a noticeable loss of gloss in the final paint film. These issues lead to frequent rework, impacting production costs and efficiency.

[0003] Current solutions include: 1. Adding directional additives to the formulation. However, since the inner and outer panels of the vehicle are supplied with a single paint system, when improving the gloss of the inner panels, the color and appearance of the outer panel paint must be considered, thus limiting the scope and effectiveness of this method. 2. Developing specialized coatings for inner panels, reducing the amount of high-scintillation pigments in the formulation or directly replacing them with small-particle-size pigments. The disadvantage of this method is that it requires a separate paint delivery system, resulting in reduced resource and equipment efficiency. Summary of the Invention

[0004] Based on the above facts, the purpose of this invention is to provide a water-based paint for automobiles, its preparation method, and its application. The water-based paint for automobiles provided in this invention is applicable to the coating of both outer and inner panels of automobile bodies. In particular, when using a static-free compressed air robotic arm to spray the inner panels of automobile bodies, it can significantly improve the appearance of the coating film formed on the inner panels and overcome problems such as coating gloss loss.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] On one hand, the present invention provides a water-based paint for automobiles, wherein the raw materials for forming the water-based paint, by weight, contain the following components:

[0007]

[0008] Organic solvents, including 6-8 parts of high-boiling-point alcohol ether solvents and 2-4 parts of swelling solvents.

[0009] Furthermore, the swelling solvent is selected from at least two of isooctanol, isopropanol, and ethylene glycol hexyl ether.

[0010] Furthermore, the swelling solvent is a mixture of isooctanol and isopropanol in a mass ratio of 1:0.5-1:2.

[0011] Furthermore, the high-boiling-point alcohol ether solvent is selected from ethylene glycol butyl ether and / or ethylene glycol isooctyl ether.

[0012] Furthermore, the raw material also contains a thickener, which comprises 4-6 parts of silicate thickener and 0.5-1 parts of acrylic copolymer thickener.

[0013] Furthermore, the mass ratio of the silicate thickener to the acrylic copolymer thickener is 4:1 to 6:1.

[0014] Furthermore, the raw material also contains 3-6 parts of polyamide wax.

[0015] Furthermore, the raw materials also contain 0.5-1 parts of pH adjuster, 3-5 parts of defoamer and 1-3 parts of wetting agent.

[0016] In another aspect, the present invention provides a method for preparing the water-based paint for automobiles as described above, comprising the following steps:

[0017] Add some deionized water to the waterborne polyurethane dispersion, mix well, then add melamine-formaldehyde resin and waterborne hydroxy acrylic dispersion, adjust the pH, then add organic solvent, color paste, aluminum silver paste and pearlescent pigment, and finally use the remaining deionized water to adjust the viscosity to obtain the waterborne paint for automobiles.

[0018] On another front, the present invention provides the application of water-based paints for automobiles as described above in the coating of automobile bodies.

[0019] Furthermore, an anti-static compressed air robotic arm is used to apply water-based paint to the car body.

[0020] Furthermore, an anti-static compressed air robotic arm is used to apply the water-based paint to the inner panels of the car body.

[0021] The beneficial effects of this invention are as follows:

[0022] In the water-based automotive paint provided by this invention, the addition of a swelling solvent increases the evaporation rate of the paint solvent. At the moment of atomization during spraying, it accelerates the escape speed of the solvent in the paint mist. Combined with the use of a water-based polyurethane dispersion, it improves the drying speed after film formation, thereby optimizing the interlayer miscibility and improving the appearance of the paint film. A preferred polyamide wax provides resistance to paint film sagging, blown-out, and cyclic sedimentation, while also improving low-shear rheology and enhancing the orientation of metallic pigments after film formation. The use of a preferred thickener gives the coating higher thixotropy and resistance to cyclic viscosity reduction, ensuring stable orientation of metallic pigments after paint film formation. Through the combination of these components, the high-scintillation pigments in the water-based paint film are arranged in a flat, planar orientation, preventing the pigments from puncturing the clear coat and solving the problem of gloss loss in paint films applied to automotive interior panels using robotic arms under electrostatic-free, high-compression air ratios. Attached Figure Description

[0023] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0024] Figure 1 This diagram illustrates how the appearance of a paint film is affected by the abnormal orientation of metallic pigments.

[0025] Figure 2 The images show actual photos of the appearance of the paint films obtained in Example 1 and Comparative Example 1. Detailed Implementation

[0026] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments and accompanying drawings, further explains the invention. Similar components in the drawings are indicated by the same reference numerals. Those skilled in the art should understand that the specific description below is illustrative rather than restrictive and should not be construed as limiting the scope of protection of the present invention.

[0027] To address the noticeable loss of gloss in paint films obtained when using a static-free compressed air robotic arm to spray paint automotive body interior panels, this invention reveals that the common practice of using a high compressed air ratio and low rotary cup speed in this method often results in abnormal alignment of metallic pigments in high-gloss metallic paints after film formation. Consequently, after dehydration, clear coat application, and baking, the clear coat surface is easily punctured by the sharp corners of these abnormally aligned metallic pigments (e.g., ...). Figure 1 As shown in the figure, this results in a noticeable loss of gloss in the obtained composite coating film.

[0028] Based on this, one specific embodiment of the present invention provides an automotive water-based paint, wherein the raw materials forming the water-based paint, by weight, contain the following components:

[0029]

[0030] Organic solvents, including 6-8 parts of high-boiling-point alcohol ether solvents and 2-4 parts of swelling solvents.

[0031] The water-based paint provided in this embodiment can be used as original equipment manufacturer (OEM) paint for painting automobile bodies. Specifically, it can be used for painting both the inner and outer panels of an automobile body, especially the inner panels. The water-based paint is preferably a metallic paint.

[0032] This embodiment does not require specific application methods for the water-based paint; conventional automotive body painting is sufficient. In particular, when this water-based paint is used to spray the inner panels of an automotive body using a non-static compressed air robotic arm, the resulting paint film not only meets all performance requirements but also exhibits a better appearance, higher spraying efficiency, and a higher product yield.

[0033] As the main film-forming resin of this waterborne paint, the waterborne polyurethane dispersion exhibits shear stability, providing the paint film with good flexibility and appearance. Exemplary waterborne polyurethane dispersions include, but are not limited to, ZINX's polyurethane resins DAOTAN TW6466 / 36WA and DAOTAN TW 6462 / 36WA, DSM's NeoPacE-122, and Lubrizol's Aptalon. TM M8100, etc.

[0034] Exemplary amounts of aqueous polyurethane dispersions include, but are not limited to, 12-15 parts, 13-15 parts, 15 parts, etc.

[0035] In this embodiment of the invention, the swelling solvent is preferably an alcohol-based swelling solvent. The swelling solvent in this embodiment can effectively combine with the aqueous polyurethane dispersion to achieve a swelling effect, providing thermal stability and good thixotropy of the coating viscosity, thereby improving the appearance of the paint. In some examples, suitable swelling solvents are selected from at least two of isooctanol, isopropanol, and ethylene glycol hexyl ether, preferably a mixture of isooctanol and isopropanol in a mass ratio of 1:0.5-1:2. By selecting and combining the swelling solvents, the solvent evaporation rate is increased, accelerating the solvent escape rate from the paint mist during spraying atomization, increasing the drying speed after film formation, optimizing the interlayer miscibility, and thus improving the abnormal pigment arrangement in the coating film, giving the coating film a better appearance and preventing the problem of gloss loss. In some specific examples, the mass ratio of isooctanol to isopropanol includes, but is not limited to, 1:0.5-1:1, 1:1-1:1.5, 1:1-1:2, 1:1, etc.

[0036] In this embodiment, controlling the range of amounts of the aqueous polyurethane dispersion and the swelling solvent can further prevent the problem of gloss loss in the paint film. Preferred suitable mass ratios of the aqueous polyurethane dispersion and the swelling solvent include, but are not limited to, 2.5:1-5:1, 2.5:1-4:1, 3:1-5:1, 3:1-4:1, and 3.75:1.

[0037] In this embodiment, the high-boiling-point alcohol ether solvent mainly serves to improve the affinity of the film-forming resin and related additives in the water-based paint with water, while also providing a better window for surface drying at the interfaces between the coating layers after application. The high-boiling-point alcohol ether solvent preferably has good hydrophilicity. Exemplary high-boiling-point alcohol ether solvents include, but are not limited to, those selected from ethylene glycol butyl ether and / or ethylene glycol isooctyl ether.

[0038] To further improve the thermal stability and thixotropic properties of the paint viscosity, in some examples, the raw materials also contain a thickener, which contains 4-6 parts of silicate thickener and 0.5-1 parts of acrylic copolymer thickener.

[0039] The silicate thickener is a synthetic flake silicate that is insoluble in water but can hydrate and swell in water to form a colorless and transparent colloid. A 2% aqueous solution is typically prepared to form a highly thixotropic colloid. In this embodiment, the silicate thickener is swelled in combination with an aqueous polyurethane dispersion, providing thermal stability of viscosity, superior thickening, anti-sagging properties, and rheological properties. Exemplary silicate thickeners include, but are not limited to, BYK's Laponite RD and Hemmings' BENTONE LT.

[0040] The acrylic copolymer thickener is preferably a non-associative polyacrylate alkali-swellable emulsion, which, when combined with a silicate thickener, achieves a morphological thickening effect on the film-forming resin, particles, and water (i.e., alkali-swellable thickening effect: it can undergo dissolution and hydration reactions in an alkaline environment, thereby forming high molecular weight polymer chains. These polymer chains form a colloidal solution in water, in which polymer molecules interact with water molecules to form a network structure. This structure can form a network in the liquid, thereby increasing the viscosity and toughness of the liquid and improving its rheological properties). Exemplary acrylic copolymer thickeners include, but are not limited to, ASE 60 selected from Rohm and Haas and / or Viscalex HV-30 selected from Ciba.

[0041] By combining silicate thickeners and acrylic copolymer thickeners, water-based paints exhibit higher thixotropy and resistance to cyclic viscosity reduction, thereby achieving stable directional alignment of metallic pigments after paint film formation. More specifically, this embodiment found that if the formulation contains only silicate thickeners, the overall viscosity of the resulting paint (e.g., circulation pipeline viscosity) is too low, making the formed paint film prone to problems such as paint cracking; if the formulation contains only acrylic copolymer thickeners, the low-shear viscosity of the resulting paint is too low, making the formed paint film prone to defects such as blistering and poor visual appearance.

[0042] In some preferred examples, the mass ratio of the silicate thickener to the acrylic copolymer thickener is 4:1 to 6:1.

[0043] To further improve the arrangement and interfacial effects of pigments in water-based paints, in some examples, the raw material also contains 3-6 parts of polyamide wax. Exemplary polyamide waxes are selected from Hemings' THXATROL P2100W and / or Longhai Chemical's 7802. The use of polyamide wax can improve low-shear rheology, enhance the orientation ability of metallic pigments after film formation, and provide good anti-sagging and anti-settling effects in this water-based paint system.

[0044] In the water-based paint provided in this embodiment, other additives, such as pH adjusters, defoamers, and wetting agents, can be added as needed.

[0045] In some examples, the raw materials also contain 0.5-1 parts of pH adjuster, 3-5 parts of defoamer and 1-3 parts of wetting agent.

[0046] pH adjusters can be used to adjust the pH value of this water-based paint. An exemplary pH adjuster is dimethylethanolamine, including but not limited to dimethylacetamide produced by Shandong Jiawei Chemical Co., Ltd.

[0047] Defoamers can be used to prevent surface defects in paint films, such as pinholes, orange peel, blistering, and pores. They can also prevent boiling marks, thus improving the leveling properties of the coating. Exemplary defoamers include, but are not limited to, BYK-WS and BYK-WA from BYK Corporation, and SHELLSOL TK from Shell Corporation.

[0048] Wetting agents are primarily used to wet / reduce the surface tension of coatings, preventing pinholes and bubbles from forming on the coating surface, and also have a wetting and leveling effect. Exemplary wetting agents include, but are not limited to, Evonik's DYNOL 607, DYNOL 360, SURFYNOL 104PG, and Degussa Evonik's BETTERSOL 440.

[0049] In this embodiment, the aqueous hydroxy acrylic dispersion can react with melamine-formaldehyde resin, resulting in a coating film with better appearance and performance. Exemplary aqueous hydroxy acrylic dispersions include, but are not limited to, Zhanxin acrylic resin. 6803, Wanhua Chemical's Lacper 4702 acrylic emulsion, BASF's... One or more of the following: PU1035W, Luhydran S 938T, and Guangshu Company's water-based acrylic resin GS-360.

[0050] Exemplary amounts of aqueous hydroxyacrylic acid dispersions include, but are not limited to, 6-9 parts, 7-9 parts, 9 parts, etc.

[0051] In this embodiment, melamine-formaldehyde resin can be used as a crosslinking agent to impart a certain degree of crosslinking to the paint film. Exemplary melamine-formaldehyde resins include, but are not limited to, one or more selected from CYMEL325, CYMEL327, CYMEL370, etc.

[0052] The color paste mainly serves to adjust the color. In this embodiment, there are no special requirements for the selection of color paste; for example, conventional red, black, and yellow color pastes used for color adjustment are sufficient.

[0053] Aluminum silver paste is primarily used to provide shimmer and graininess in color. In this embodiment, a high-gloss aluminum silver paste is preferred, and its selection depends on the specific desired color. The particle size of the aluminum silver paste is preferably 15 μm or larger, more preferably 15-20 μm. Exemplary aluminum silver pastes include, but are not limited to, those selected from Toyo's AL 93-0647 or ECAR's coated aluminum silver paste HP Z 2505.

[0054] In this embodiment, pearlescent pigments are primarily used to provide color and a shimmering effect. Suitable pearlescent pigments are preferably high-sparkle pearlescent pigments. Their selection depends on the specific color. The particle size of the high-sparkle pearlescent pigment is preferably 15 μm or larger, more preferably 25 μm or larger, for example, 25-35 μm. Exemplary pearlescent pigments include, but are not limited to, those selected from Merck's Xirallic series and CQV pigments' AE series.

[0055] In some examples, the total raw material content of water-based paints for automobiles is 100 parts by weight.

[0056] According to another specific embodiment of the present invention, a method for preparing the water-based paint for automobiles as described above is provided, the method comprising the following steps:

[0057] Add some deionized water to the waterborne polyurethane dispersion, mix well, then add melamine-formaldehyde resin and waterborne hydroxy acrylic dispersion, adjust the pH, then add organic solvent, color paste, aluminum silver paste and pearlescent pigment, and finally use the remaining deionized water to adjust the viscosity to obtain the waterborne paint for automobiles.

[0058] In some specific examples, the preparation method includes the following steps:

[0059] Under stirring conditions of 300-500 r / min, waterborne polyurethane dispersion and silicate thickener are mixed sequentially. A portion of deionized water is added while stirring, and after mixing, melamine-formaldehyde resin and waterborne hydroxy acrylic dispersion are added sequentially. The pH value is adjusted using a pH adjuster, and after thorough mixing, acrylic copolymer thickener, defoamer, high-boiling-point alcohol ether solvent, and wetting agent are added in sequence. After thorough mixing, a swelling solvent is added, and the stirring speed is increased to 800-1000 r / min. Polyamide wax is slowly added and thoroughly mixed. Color paste, aluminum silver paste, and pearlescent pigment are added while stirring. Finally, the viscosity is adjusted using the remaining deionized water to obtain the waterborne automotive paint.

[0060] On another front, the present invention provides the application of water-based paints for automobiles as described above in the coating of automobile bodies.

[0061] It is understandable that this water-based paint can be used for painting the outer and inner panels of a car body.

[0062] Preferably, in this application, an anti-static compressed air robotic arm is used to coat the inner panels of the car body with water-based paint.

[0063] The technical solution of the present invention will be described below with reference to some specific embodiments:

[0064] Example 1

[0065] A water-based paint for automobiles, the formulation of which is shown in Table 1 below, and its preparation method includes the following steps:

[0066] According to the raw material ratio, the aqueous polyurethane dispersion and silicate thickener were added to the container in sequence under stirring conditions of 300-500 r / min. Deionized water 1 was added under stirring conditions and stirred thoroughly.

[0067] Add the melamine-formaldehyde resin and water-based hydroxy acrylic dispersion in the order of raw materials, then adjust the pH value with a pH adjuster and stir thoroughly.

[0068] Add the acrylic copolymer thickener, defoamer, high-boiling-point alcohol ether solvent and wetting agent in sequence, and stir thoroughly.

[0069] Add the swelling solvents isooctanol and isopropanol, increase the rotation speed to 800-1000 r / min, slowly add the polyamide wax, and stir thoroughly.

[0070] Add color paste, aluminum silver paste, and pearlescent pigment while stirring, and finally adjust the viscosity with deionized water 2 to obtain the water-based paint for automobiles.

[0071] Comparative Examples 1-9

[0072] The formulations of the water-based paints for automobiles in each comparative example are shown in Tables 1 and 2 below. Their preparation methods are similar to those in Example 1, with the only difference being the amount of some components or the fact that some components do not need to be added.

[0073] Table 1

[0074]

[0075]

[0076] Table 2

[0077]

[0078] The application of the above-mentioned water-based paints includes the following steps:

[0079] On the cold-rolled steel sheet substrate after electrophoresis, a rotary cup atomizer simulating the field was used to spray water-based automotive interior coating with a film thickness of 15-25 micrometers. After flash drying for 3 minutes, it was dehydrated and baked at 75-90℃. Then, a clear varnish was sprayed with a film thickness of about 30-40 micrometers, flash dried for 7 minutes, and baked at 130-150℃ for 25 minutes. After being removed and cooled, it became the experimental material.

[0080] The performance of the experimental boards obtained from the tests is shown in Tables 3 and 4 below. The test standards for each performance attribute are as follows:

[0081] In the testing items, the gloss item was tested using a BYK-4430 three-angle gloss meter; the appearance item was tested using a BYK-4840 orange peel meter; and the pinhole item was tested by visual observation.

[0082] Table 3

[0083]

[0084] Table 4

[0085]

[0086] The appearance of the paint film obtained using Example 1 and Comparative Example 1 are shown in the following images. Figure 2 As shown.

[0087] Example 2

[0088] A water-based paint for automobiles has the following formula as shown in Table 5, and its preparation method is the same as that in Example 1.

[0089] Example 3

[0090] A water-based paint for automobiles has the following formula as shown in Table 5, and its preparation method is the same as that in Example 1.

[0091] Example 4

[0092] A water-based paint for automobiles has the following formula as shown in Table 5, and its preparation method is the same as that in Example 1.

[0093] Table 5

[0094]

[0095]

[0096] Using the same method as in Example 1, the coatings of Examples 2-4 were applied and their performance was tested. The performance results are shown in Tables 6 and 7 below.

[0097] Table 6

[0098]

[0099] Table 7

[0100] Testing items Testing standards Example 1 Example 2 Example 3 Example 4 Adhesion GB / T 1720-1979 Level 0 Level 0 Level 0 Level 0 Impact resistance GBT1732-1993 35cm 35cm 35cm 35cm Cup protuberance GB / T 9753-2007 6mm 6mm 6mm 6mm acid resistance GB 1763-1979 OK OK OK OK Alkali resistance GB 1763-1979 OK OK OK OK Water resistance GB / T 1733-1993 OK OK OK OK

[0101] The performance tests of the paint films obtained in each comparative example are shown in Table 7. The acid and alkali resistance and water resistance of the paint films are all NG.

[0102] 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. A water-based paint for automobiles, characterized in that, The raw materials that form this water-based paint, by weight, contain the following components: Organic solvents, including 6-8 parts of high-boiling-point alcohol ether solvents and 2-4 parts of swelling solvents.

2. The water-based automotive paint according to claim 1, characterized in that, The swelling solvent is selected from at least two of isooctanol, isopropanol, and ethylene glycol hexyl ether; Preferably, the swelling solvent is a mixture of isooctanol and isopropanol in a mass ratio of 1:0.5-1:

2.

3. The water-based automotive paint according to claim 1, characterized in that, The high-boiling-point alcohol ether solvent is selected from ethylene glycol butyl ether and / or ethylene glycol isooctyl ether.

4. The water-based automotive paint according to claim 1, characterized in that, The raw materials also contain a thickener, which contains 4-6 parts of silicate thickener and 0.5-1 parts of acrylic copolymer thickener; Preferably, the mass ratio of the silicate thickener to the acrylic copolymer thickener is 4:1 to 6:

1.

5. The water-based automotive paint according to claim 1, characterized in that, The raw materials also contain 3-6 parts of polyamide wax.

6. The water-based automotive paint according to any one of claims 1-5, characterized in that, The raw materials also contain 0.5-1 parts of pH adjuster, 3-5 parts of defoamer and 1-3 parts of wetting agent.

7. The method for preparing water-based automotive paint according to any one of claims 1-6, characterized in that, Includes the following steps: Add some deionized water to the waterborne polyurethane dispersion, mix well, then add melamine-formaldehyde resin and waterborne hydroxy acrylic dispersion, adjust the pH, then add organic solvent, color paste, aluminum silver paste and pearlescent pigment, and finally use the remaining deionized water to adjust the viscosity to obtain the waterborne paint for automobiles.

8. The application of water-based paints for automobiles as described in any one of claims 1-6 in the coating of automobile bodies.

9. The application according to claim 8, characterized in that, A static-free compressed air robotic arm is used to apply water-based paint to the car body.

10. The application according to claim 8, characterized in that, A static-free compressed air robotic arm is used to coat the inner panels of the car body with water-based paint.

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