Water-based floating coat with low film thickness and high appearance for automobile as well as preparation method and application of water-based floating coat

Abstract

The invention discloses a low-film-thickness high-appearance water-based floating coat for an automobile as well as a preparation method and application thereof. The water-based floating coat is prepared from the following raw materials in parts by weight: 20 to 40 parts of water-based polyester dispersion, 10 to 20 parts of water-based acrylic resin, 5 to 10 parts of amino resin, 2 to 4 parts of polypropylene glycol oligomer, 1 to 5 parts of transparent filler slurry, 1 to 3 parts of organic solvent, 1 to 5 parts of deionized water and auxiliaries, wherein the number-average molecular weight of the water-based polyester dispersion is 5000 to 10000, the Tg is 4 to 10 DEG C, the acid value is 3 to 16 KOHmg / g, and the hydroxyl value is 10 to 15 KOHmg / g. When the water-based floating coat is applied to automobile coating, the mechanical and chemical properties of the original coating level can be achieved under the condition of extremely low dry film thickness (less than 16 microns), and the properties (such as collision resistance, shedding resistance and corrosion resistance) and the appearance are better.

Description

Technical Field

[0001] This invention relates to the field of waterborne automotive coatings. More specifically, it relates to a low-film-thickness, high-appearance waterborne intermediate coating for automobiles, its preparation method, and its application. Background Technology

[0002] Lightweighting and energy conservation in automobiles are effective ways to achieve carbon neutrality and are of great significance to the upgrading of the automotive industry and sustainable development for humankind. Currently, automotive painting generally employs a four-coat process: electrophoretic layer, intermediate layer, topcoat, and clearcoat. The mainstream process is 3C1B. The typical intermediate coat thickness is 25-35 μm. Because the intermediate coat usually uses large amounts of barium sulfate and talc as fillers, its dry film density is high, making it the largest component of the overall coating weight. Therefore, to better achieve lightweighting of automobiles, it is necessary to reduce the thickness of the intermediate coat to achieve lightweighting of the coating process while simultaneously saving energy and reducing emissions. Summary of the Invention

[0003] Based on the above facts, the purpose of this invention is to provide a low-film-thickness, high-appearance waterborne intermediate coating for automobiles, its preparation method, and its application. When this waterborne intermediate coating is used in automotive painting, it can achieve the same mechanical and chemical properties as the original coating while having an extremely low dry film thickness (below 16 μm), and with even better performance (e.g., impact resistance, peeling resistance, and corrosion resistance) and appearance.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A low-film-thickness, high-appearance water-based intermediate coat for automobiles, wherein the raw materials forming the water-based intermediate coat comprise, by weight, the following components:

[0006] 20-40 parts waterborne polyester dispersion, 10-20 parts waterborne acrylic resin, 5-10 parts amino resin, 2-4 parts polypropylene glycol oligomer, 1-5 parts transparent filler slurry, 1-3 parts organic solvent, 1-5 parts deionized water and additives;

[0007] The number-average molecular weight (Mn) of the aqueous polyester dispersion is 5000-10000, the Tg is 4-10℃, the acid value is 3-16KOHmg / g, and the hydroxyl value is 10-15KOHmg / g.

[0008] Furthermore, the aqueous polyester dispersion is selected from VYLONAL MD-1335 provided by Yobo Co., Ltd. and Allnex Co., Ltd. At least one or more of the following: AZ 541w / 42WA, WATERSOL ZHW-1346 from DIC, SZ265 G3-75 from Covestro, and UCOAT N-800 from Sanyo Chemical Industries, Ltd.

[0009] Furthermore, the minimum film-forming temperature of the waterborne acrylic resin is 25-45°C.

[0010] Furthermore, the waterborne acrylic resin is selected from at least one or more of the following: EMA-1015S provided by Nippon Paint Co., Ltd., XK-82 or XK-86 provided by Covestro Co., Ltd., and ACW-1033, ACW-1011, and PZW-1001 provided by Noroo Co., Ltd.

[0011] Furthermore, the average number-average molecular weight of the polypropylene glycol oligomer is 950-1050, preferably 1000.

[0012] Furthermore, the polypropylene glycol oligomer is selected from one or more of PRIMEPOL PX-1000 and SANNIX GP-1000 provided by Sanyo Chemical Industries, Ltd.

[0013] Furthermore, the mass ratio of the aqueous polyester dispersion, aqueous acrylic resin, and polypropylene glycol oligomer is (30-37):(11-13):2.

[0014] Furthermore, the amino resin is a partially methylated water-soluble amino resin.

[0015] Furthermore, the amino resin is selected from at least one or more of CYMEL 325, CYMEL 370, and CYMEL250 provided by Allnex.

[0016] Further, by weight, the additives include: 1-2 parts of defoamer, 1-2 parts of surfactant, 1-5 parts of thickener and 0.01-0.05 parts of pH adjuster.

[0017] Furthermore, the raw materials also contain 0-10 parts of black non-transparent filler slurry and / or 0-40 parts of other non-transparent filler slurry.

[0018] In another aspect, the present invention provides a method for preparing the water-based intermediate coating as described above, comprising the following steps:

[0019] The transparent filler slurry, polypropylene glycol oligomer, a portion of deionized water, aqueous polyester dispersion, and aqueous acrylic resin are mixed in sequence.

[0020] Add a mixture of some additives and some deionized water to the obtained material, and then add a mixture of amino resin, organic solvent and some additives.

[0021] After mixing, add the remaining deionized water and remaining additives, and adjust the pH, viscosity and brightness respectively to obtain the water-based intermediate coating.

[0022] In another aspect, the present invention provides the application of the water-based intermediate coating as described above in automotive low film thickness intermediate coating.

[0023] Furthermore, the dry film thickness of the aqueous intermediate coating after application is less than 16 μm.

[0024] The beneficial effects of this invention are as follows:

[0025] The water-based intermediate coating provided by this invention, through the combination of various components in the raw materials, the selection of water-based polyester dispersions, and the preferred combination of water-based polyester dispersions, water-based acrylic resins, and polypropylene glycol oligomers, endows the water-based intermediate coating with mechanical and chemical properties that can still achieve the coating level of the original thick-film water-based intermediate coating under extremely low coating film thickness conditions, while having better appearance, impact resistance, peeling resistance, and corrosion resistance. Detailed Implementation

[0026] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments, further clarifies the invention. Those skilled in the art should understand that the specific descriptions below are illustrative rather than restrictive, and should not be construed as limiting the scope of protection of the present invention.

[0027] To provide a low-film-thickness coating (intermediate coat dry film thickness below 16μm) water-based intermediate coat for automotive coatings to meet the requirements of automotive lightweighting, one specific embodiment of the present invention provides a low-film-thickness, high-appearance water-based intermediate coat for automobiles. The raw materials forming this water-based intermediate coat, by weight, contain the following components:

[0028] 20-40 parts waterborne polyester dispersion, 10-20 parts waterborne acrylic resin, 5-10 parts amino resin, 2-4 parts polypropylene glycol oligomer, 1-5 parts transparent filler slurry, 1-3 parts organic solvent, 1-5 parts deionized water and additives;

[0029] The aqueous polyester dispersion has a number-average molecular weight of 5000-10000, a Tg of 4-10℃, an acid value of 3-16 KOH mg / g, and a hydroxyl value of 10-15 KOH mg / g.

[0030] In the technical solution of this invention, the selection of the waterborne polyester dispersion directly affects the appearance, impact resistance, peeling resistance, and corrosion resistance of the coating obtained by the waterborne intermediate coating with low film thickness.

[0031] In some examples, the aqueous polyester dispersion is selected from VYLONAL MD-1335 provided by Yobo Co., Ltd., and Allnex Co., Ltd. At least one or more of the following: AZ 541w / 42WA, WATERSOL ZHW-1346 from DIC, SZ265 G3-75 from Covestro, and UCOAT N-800 from Sanyo Chemical Industries, Ltd.

[0032] In some examples, the aqueous polyester dispersion is composed of VYLONALMD-1335 or A mixture of AZ 541w / 42WA and UCOAT N-800. The aforementioned effects are even better in this case.

[0033] To obtain a waterborne intermediate coat with superior appearance, impact resistance, anti-slip properties, and corrosion resistance that can be applied with low film thickness, in some preferred examples, the waterborne polyester dispersion is composed of VYLONALMD-1335 or One of AZ541w / 42WA was mixed with UCOAT N-800 at a mass ratio of (18-22):11.

[0034] In some preferred examples, the total amount of the aqueous polyester dispersion added is 30-40 parts by weight, etc.

[0035] In some examples, the waterborne acrylic resin is a fast-drying resin with a minimum film-forming temperature (MFFT) of 25-45°C. In this embodiment, the waterborne acrylic resin is used in combination with the waterborne polyester dispersion and polypropylene glycol oligomer, which enables the waterborne intermediate coat to achieve the same mechanical and chemical properties as the original thick-film waterborne intermediate coat even with extremely low coating thickness, while also providing superior appearance, impact resistance, peel resistance, and corrosion resistance.

[0036] In some specific examples, the waterborne acrylic resin is selected from at least one or more of the following: EMA-1015S provided by Nippon Paint Co., Ltd., XK-82 or XK-86 provided by Covestro, and ACW-1033, ACW-1011, and PZW-1001 provided by Noroo.

[0037] In some preferred examples, the total amount of the waterborne acrylic resin added is 10-15 parts by weight, etc.

[0038] In some examples, the average number-average molecular weight of the polypropylene glycol oligomer is 950-1050, preferably 1000.

[0039] In some specific examples, the polypropylene glycol oligomer is preferably one or more of PRIMEPOL PX-1000 and SANNIX GP-1000 provided by Sanyo Chemical Industries, Ltd.

[0040] In some preferred examples, the mass ratio of the aqueous polyester dispersion, aqueous acrylic resin, and polypropylene glycol oligomer is (30-37):(11-13):2. Under these conditions, the coating obtained by combining the three components achieves the same mechanical and chemical properties as the original coating while having an extremely low dry film thickness (below 16 μm), and also exhibits superior impact resistance, peeling resistance, corrosion resistance, and appearance.

[0041] In this embodiment, the amino resin is a cross-linked resin. In some examples, the amino resin is a partially methylated water-soluble amino resin.

[0042] In some specific examples, the amino resin is selected from at least one or more of CYMEL 325, CYMEL 370, and CYMEL 250 provided by Allnex.

[0043] In the aqueous intermediate coating of this embodiment, additives can be selected according to actual needs. For example, additives that can be added include, but are not limited to, defoamers, surfactants, thickeners, pH adjusters, etc.

[0044] In some examples, the additives, by weight, comprise: 1-2 parts of defoamer and / or 1-2 parts of surfactant and / or 1-5 parts of thickener and / or 0.01-0.05 parts of pH adjuster.

[0045] In some specific examples, the defoamer is one or a mixture of mineral oil, hydrophobic silica and polyethylene glycol nonionic surfactant, preferably one or more of SNDEFOAMER 1349, SNDEFOAMER 1341 and SNDEFOAMER 1390 from Seinopco, Japan.

[0046] In some specific examples, the surfactant is selected from one or more of Evonik's SURFYNOL 465 and SURFYNOL 440, Gamma Chemical's GS-4035, and Liaoning Saifei Chemical Co., Ltd.'s FS-640 and FS-660.

[0047] In some specific examples, the tackifier is selected from one or more of AQ-580, AQ-001, AQ-630, and AQ-870 from DISPARON Japan.

[0048] In some specific examples, the pH adjuster is dimethylethanolamine.

[0049] In some specific examples, the organic solvent is selected from one or more of ethylene glycol isooctyl ether, isooctyl alcohol, tripropylene glycol methyl ether, and diethylene glycol butyl ether.

[0050] In this embodiment, the transparent filler slurry can improve the coating's resistance to stone chipping and reduce the risk of pinholes. It is a flake-shaped talc powder dispersion.

[0051] For example, the raw material composition of the transparent filler slurry is: 40-60 wt% talc, 5-15 wt% dispersant (for example, BYK-190) and 30-50 wt% deionized water.

[0052] In some preferred embodiments, the raw material composition of the transparent filler slurry is: 50 wt% talc, 10 wt% dispersant and 40 wt% deionized water.

[0053] For example, the preparation method of the transparent filler slurry is as follows: after adding a dispersant to deionized water, talc powder is added under stirring, and after high-speed dispersion for 30 minutes, it is sand-milled to a fineness of ≤5 micrometers.

[0054] In some examples, the talc is selected from one or more of Fuji's FH104A and Heshan's CMS-888 talc.

[0055] For example, the raw materials may also contain 0-10 parts of black non-transparent filler slurry and / or 0-40 parts of other non-transparent filler slurry.

[0056] For example, the black opaque filler slurry contains 30 wt% carbon black, 10 wt% EFKA 4585, and 60 wt% deionized water. The carbon black is selected from one or more of Mitsubishi Carbon Black MA100, Orion Carbon Black HIBLACK 900L, and PRINTEX U carbon black.

[0057] It is understood that the "other non-transparent filler slurry" refers to non-transparent filler slurries other than the "black non-transparent filler slurry".

[0058] For example, the other non-transparent filler slurry is selected from at least one of filler slurry A, filler slurry B, and filler slurry C. For instance, filler slurry A contains 60 wt% barium sulfate, 10 wt% titanium dioxide, and 5 wt% dispersant (e.g., BYK-190) and 25 wt% deionized water; filler slurry B contains 70 wt% titanium dioxide, 5 wt% dispersant (BYK-190), and 25 wt% deionized water; and filler slurry C contains 30 wt% barium sulfate, 40 wt% titanium dioxide, and 5 wt% dispersant (e.g., BYK-190) and 25 wt% deionized water. Filler slurries A, B, and C can be used in conjunction with the black non-transparent filler slurry to display different lightness levels.

[0059] For example, the barium sulfate is selected from one or more of the barium sulfate models MM045 provided by Dalong Manganese Industry and BARIFINE BF-21 provided by Sakai Chemicals of Japan, and the titanium dioxide is selected from one or more of the CR-97 of ISK Japan Ishihara Sangyo Co., Ltd., R-996 of Xiangyang Longmang Titanium Industry, R-902 and R-706 of DuPont of the United States.

[0060] In some examples, the total weight of the raw materials for the water-based intermediate coating is 100 parts.

[0061] In this embodiment, the waterborne polyurethane resin is not essential.

[0062] According to another specific embodiment of the present invention, a method for preparing the water-based intermediate coating as described above is provided, the method comprising the following steps:

[0063] The transparent filler slurry, polypropylene glycol oligomer, a portion of deionized water, aqueous polyester dispersion, and aqueous acrylic resin are mixed in sequence.

[0064] Add a mixture of some additives and some deionized water to the obtained material, and then add a mixture of amino resin, organic solvent and some additives.

[0065] After mixing, add the remaining deionized water and remaining additives, and adjust the pH, viscosity and brightness respectively to obtain the water-based intermediate coating.

[0066] According to another specific embodiment of the present invention, a method for preparing the water-based intermediate coating as described above is provided, the method comprising the following steps:

[0067] The optional non-transparent filler slurry, transparent filler slurry, polypropylene glycol oligomer, partially deionized water, aqueous polyester dispersion, and aqueous acrylic resin are mixed in sequence.

[0068] Add a mixture of some additives and some deionized water to the obtained material, and then add a mixture of amino resin, organic solvent and some additives.

[0069] After mixing, add the remaining deionized water, remaining additives, and optional black opaque filler slurry, and adjust the pH value, viscosity, and brightness respectively to obtain the water-based intermediate coating.

[0070] According to yet another specific embodiment of the present invention, the application of the water-based intermediate coating as described above in automotive low film thickness intermediate coating is provided.

[0071] In some examples, the dry film thickness of the aqueous intermediate coating after application is less than 16 μm.

[0072] The technical solution of the present invention will be described below with reference to some specific embodiments:

[0073] Example 1

[0074] A water-based intermediate coating for automobiles with low film thickness and high appearance has the following raw material composition as shown in Table 1.

[0075] The preparation method of this water-based intermediate coating includes the following steps:

[0076] Sub-cylinder A:

[0077] Choose a suitable container, add thickener, 80wt% deionized water (DIW), and 80wt% pH adjuster, stir for 40 minutes, and test the fineness to ≤5 microns before use.

[0078] Sub-cylinder B:

[0079] Select a suitable container, add amino resin, add organic solvent and surfactant while stirring, stir for 40 minutes and set aside;

[0080] Main steps:

[0081] 1) Select a heat-insulating container and maintain the temperature at 20-27℃. Add filler slurry A and start stirring at 300±100 rpm / min for 10 minutes.

[0082] 2) Add the transparent filler slurry while stirring, and continue stirring for 10 minutes;

[0083] 3) Add polypropylene glycol oligomer and 10wt% deionized water (DIW) while stirring, and continue stirring for 10 minutes.

[0084] 4) Add the water-based polyester dispersion and water-based acrylic resin while stirring, and continue stirring for 10 minutes;

[0085] 5) Slowly add the material from auxiliary cylinder A while stirring, and continue stirring for 20 minutes;

[0086] 6) Slowly add the material from auxiliary cylinder B while stirring, and continue stirring for 20 minutes;

[0087] 7) Slowly add the defoamer while stirring, and continue stirring for 20 minutes;

[0088] 8) The following day, adjust the pH and viscosity using the remaining pH adjuster and deionized water, and adjust the brightness using black non-transparent filler slurry to obtain the water-based coating. The brightness result L(45°) = 81.2. After adjustment, the properties need to be confirmed to be qualified again.

[0089] The water-based coating was tested and found to have a pH value of 8.35, a viscosity of B60 of 645 mPa·s, a viscosity of B6 of 1896 mPa·s, a solid content of 46.8%, and a density of 1.35 g / L.

[0090] The transparent filler slurry is formulated as follows: 50 wt% talc, 10 wt% dispersant and 40 wt% deionized water.

[0091] The transparent filler slurry is prepared by adding a dispersant to deionized water, adding talc powder while stirring, dispersing at high speed for 30 minutes, and then grinding to a fineness of ≤5 micrometers.

[0092] The black, opaque filler slurry contains 30 wt% carbon black, 10 wt% EFKA 4585, and 60 wt% deionized water. The carbon black is selected from Mitsubishi Carbon Black MA100 from Japan.

[0093] The formulation of filler slurry A is: 60wt% barium sulfate, 10wt% titanium dioxide, 5wt% dispersant BYK-190 and 25wt% deionized water;

[0094] The preparation method of filler slurry A is as follows:

[0095] After adding a dispersant to deionized water, barium sulfate and titanium dioxide are added under stirring; after high-speed dispersion, they are sand-milled to a fineness of ≤5 microns.

[0096] Note: The above preparation method must be completed within 1 day, and the containers used must be tested by the shrinkage cavity detection method before they can be used.

[0097] Table 1

[0098]

[0099] Example 2

[0100] A water-based intermediate coating for automobiles with low film thickness and high appearance is described in Table 1 above. Its preparation method is the same as in Example 1.

[0101] Example 3

[0102] A water-based intermediate coating for automobiles with low film thickness and high appearance is described in Table 1 above. Its preparation method is the same as in Example 1.

[0103] Example 4

[0104] A water-based intermediate coating for automobiles with low film thickness and high appearance is described in Table 1 above. Its preparation method is the same as in Example 1.

[0105] The formulation of filler slurry B is: 70wt% titanium dioxide, 5wt% dispersant BYK-190 and 25wt% deionized water;

[0106] The preparation method of filler slurry B is as follows: after adding a dispersant to deionized water, titanium dioxide is added under stirring; after high-speed dispersion, it is sand-milled to a fineness of ≤5 microns;

[0107] The formulation of the filler slurry C is: 30wt% barium sulfate, 40wt% titanium dioxide, 5wt% dispersant BYK-190, and 25wt% deionized water;

[0108] The preparation method of filler slurry C is as follows: after adding a dispersant to deionized water, barium sulfate and titanium dioxide are added under stirring; after high-speed dispersion, the mixture is sand-milled to a fineness of ≤5 microns.

[0109] Example 5

[0110] A water-based intermediate coating for automobiles with low film thickness and high appearance is described in Table 1 above. Its preparation method is the same as in Example 1.

[0111] Example 6

[0112] A water-based intermediate coating for automobiles with low film thickness and high appearance is described in Table 1 above. Its preparation method is the same as in Example 1.

[0113] The color lightness L (45°) of Examples 1-3 described in Table 1 above is approximately 80, the color lightness L (45°) of Example 4 is approximately 55, the color lightness L (45°) of Example 5 is approximately 20, and the color lightness L (45°) of Example 6 is approximately 55.

[0114] Comparative Examples 1-6

[0115] A water-based intermediate coating for automobiles has the following raw material composition formula as shown in Table 2. Its preparation method is the same as in Example 1, and the added transparent filler slurry, black opaque filler slurry, and other opaque filler slurries are the same as in Examples 1-6, and will not be repeated here.

[0116] Table 2

[0117]

[0118]

[0119] Applications of the above-mentioned water-based intermediate coating in automotive coating:

[0120] The electrophoretic coating plates were prepared using Nippon Paint electrophoretic paint on GHAC#2. The lightness L(45°) of the AR 2100NH-883P water-based paint was 80-90 (Examples 1-3 and Comparative Examples 1-3); the lightness L(45°) of the AR 2100NH-938M water-based paint was 50-55 (Examples 4, 6 and Comparative Examples 4, 6); and the lightness L(45°) of the AR 2100NH-820P water-based paint was 20-25 (Example 5 and Comparative Example 5). The clear coat was MAC O-1900 acid epoxy clear coat. The film thickness levels for each test example are shown in Table 3. The appearance results are shown in Table 4 (vertical coating and baking) and Table 5 (horizontal coating and baking).

[0121] Table 3

[0122]

[0123] Table 4

[0124]

[0125] Table 5

[0126]

[0127]

[0128] Other performance test results of the coating films obtained in each embodiment and comparative example are shown in Tables 6 and 7 below.

[0129] Table 6

[0130]

[0131]

[0132] Table 7

[0133]

[0134]

[0135]

[0136] The performance tests described above show that the paint film formed by the water-based coating in the embodiments of the present invention is superior to the comparative example in terms of appearance, performance, especially impact resistance, peeling resistance and corrosion resistance, under low film thickness coating conditions.

[0137] 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 intermediate coating for automobiles with low film thickness and high appearance, characterized in that, The raw materials forming this water-based intermediate coating contain the following components, by weight: 20-40 parts waterborne polyester dispersion, 10-20 parts waterborne acrylic resin, 5-10 parts amino resin, 2-4 parts polypropylene glycol oligomer, 1-5 parts transparent filler slurry, 1-3 parts organic solvent, 1-5 parts deionized water and additives; The aqueous polyester dispersion has a number-average molecular weight of 5000-10000, a Tg of 4-10℃, an acid value of 3-16 KOH mg / g, and a hydroxyl value of 10-15 KOH mg / g.

2. The water-based intermediate coating according to claim 1, characterized in that, The aqueous polyester dispersion is selected from VYLONAL MD-1335 provided by Yobo Co., Ltd. and Allnex Co., Ltd. At least one or more of the following: AZ 541w / 42WA, WATERSOL ZHW-1346 from DIC, SZ265 G3-75 from Covestro, and UCOAT N-800 from Sanyo Chemical Industries, Ltd.

3. The water-based intermediate coating according to claim 1, characterized in that, The minimum film-forming temperature of the waterborne acrylic resin is 25-45℃; Preferably, the waterborne acrylic resin is selected from at least one or more of the following: EMA-1015S provided by Nippon Paint Co., Ltd., XK-82 or XK-86 provided by Covestro, and ACW-1033, ACW-1011, and PZW-1001 provided by Noroo Co.

4. The water-based intermediate coating according to claim 1, characterized in that, The average number-average molecular weight of the polypropylene glycol oligomer is 950-1050; Preferably, the polypropylene glycol oligomer is selected from one or more of PRIMEPOL PX-1000 and SANNIX GP-1000 provided by Sanyo Chemical Industries, Ltd.

5. The water-based intermediate coating according to claim 1, characterized in that, The mass ratio of the aqueous polyester dispersion, aqueous acrylic resin and polypropylene glycol oligomer is (30-37):(11-13):

2.

6. The water-based intermediate coating according to claim 1, characterized in that, The amino resin is a partially methylated water-soluble amino resin. Preferably, the amino resin is selected from at least one or more of CYMEL 325, CYMEL 370, and CYMEL 250 provided by Allnex.

7. The water-based intermediate coating according to claim 1, characterized in that, By weight, the additives comprise: 1-2 parts of defoamer, 1-2 parts of surfactant, 1-5 parts of thickener and 0.01-0.05 parts of pH adjuster; Preferably, the raw materials further include 0-10 parts of black non-transparent filler slurry and / or 0-40 parts of other non-transparent filler slurry.

8. The method for preparing the water-based intermediate coating according to any one of claims 1-7, characterized in that, Includes the following steps: The transparent filler slurry, polypropylene glycol oligomer, a portion of deionized water, aqueous polyester dispersion, and aqueous acrylic resin are mixed in sequence. Add a mixture of some additives and some deionized water to the obtained material, and then add a mixture of amino resin, organic solvent and some additives. After mixing, add the remaining deionized water and remaining additives, and adjust the pH, viscosity and brightness respectively to obtain the water-based intermediate coating.

9. The application of the water-based intermediate coating as described in any one of claims 1-7 in automotive low film thickness intermediate coating.

10. The application according to claim 9, characterized in that, The dry film thickness of the water-based intermediate coating after application is less than 16 μm.

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