A waterborne protective coating composition, and a method of making and using the same

Abstract

The present application relates to a kind of water-based protective coating compositions suitable for automobile metal parts, by weight parts, it includes: water-based epoxy resin 56.1~61.3 parts, coloring pigment 1.1~1.5 parts, antirust pigment 6.3~7.3 parts, filler 8.6~9.6 parts, flatting powder 1.0~3.0 parts, phosphate ester polymer 0.5~1.0 parts, two-component flash rust inhibitor 0.6~1.0 parts, auxiliary 2.2~3.6 parts, solvent 15.0~18.0 parts, the total weight of above component is 100 parts. The water-based protective coating compositions can be used for the coating of automobile brake disc, steering knuckle, transmission shaft and other metal parts, with good salt spray resistance, volatile oil resistance, water resistance and over high temperature adhesion. The present application also relates to the preparation method and application of the above water-based protective coating compositions, and a kind of coating based on the above water-based protective coating compositions.

Description

Technical Field

[0001] This invention relates to the field of coating technology, specifically to a water-based protective coating composition, and more specifically to a water-based protective coating composition suitable for coating automotive metal parts, as well as a method for preparing the above coating composition and its application. Background Technology

[0002] The waterborne protective coating composition uses waterborne single-component self-drying epoxy resin as the main film-forming substance. Due to the strong cohesive force and dense material structure of epoxy resin, as well as the presence of highly reactive epoxy groups, hydroxyl groups, and polar groups such as ether bonds and ester bonds, epoxy resin coatings exhibit excellent adhesion to polar substrates such as metals.

[0003] With increasingly stringent environmental protection requirements, various environmental regulations are becoming more and more stringent, especially the restrictions on the emission of volatile organic compounds (VOCs), the content of harmful solvents and various heavy metals. Developing green, environmentally friendly, and low-VOC water-based protective coatings has become a trend in the coating industry.

[0004] In existing technologies, most water-based protective coating compositions have the problem of not being able to self-dry or rapidly cure into a film by low-temperature baking, which is not conducive to their use in automotive parts coating. In addition, existing water-based protective coatings generally have poor resistance to salt spray, volatile oils, water, and high-temperature adhesion, and are gradually failing to meet the needs of industry development.

[0005] In view of this, the present invention aims to provide a water-based protective coating composition to solve the problems faced in the field of existing coating technology. Summary of the Invention

[0006] Based on the above facts, the purpose of this invention is to provide a water-based protective coating composition that can be used for coating metal parts such as automotive brake discs, steering knuckles, and drive shafts, and has good resistance to salt spray, volatile oils, water, and high-temperature adhesion.

[0007] A first aspect of the present invention provides an aqueous protective coating composition, comprising, by weight:

[0008]

[0009]

[0010] The total weight of all the above components is 100 portions.

[0011] Waterborne epoxy resin

[0012] In this invention, the waterborne epoxy resin includes two different waterborne epoxy resins A and B, and the weight ratio of waterborne epoxy resin A to waterborne epoxy resin B is 2:1 to 2.3:1.

[0013] Preferably, the non-volatile content of both waterborne epoxy resin A and waterborne epoxy resin B is 35.0-41.0%, the viscosity is 500-10000 Pa·s, and the pH is 8-11.

[0014] Specifically, the waterborne epoxy resin A is EPICLON H-502-42W (purchased from D.E. Company), with a non-volatile content of 37.0-41.0%, a viscosity of 500-10000 Pa·s, and a pH of 8-11; the waterborne epoxy resin B is MODEPICS 304C (purchased from Arakawa Chemical Company), with a non-volatile content of 35.0-38.0%, a viscosity of 1500 Pa·s, and a pH of 9-11.

[0015] Coloring pigment

[0016] In some embodiments of the present invention, the coloring pigment is carbon black.

[0017] Specifically, the coloring pigment is carbon black of model MITSUBISHI CARBON BLACK MA-100 (purchased from Mitsubishi Chemical).

[0018] Rust preventive pigment

[0019] In some embodiments of the present invention, the anti-rust pigment is zinc phosphate. The anti-rust pigment used in the present invention can further improve the salt spray resistance of the coating film, mainly by reducing the corrosion propagation at the X-shaped tangential portion of the metal parts during salt spray tests. This is achieved by its fine particles filling the coating structure, increasing the density of the coating film, acting as a shield, reducing the permeability of the coating film, and thus achieving anti-rust properties. Experiments show that zinc phosphate, as an anti-rust pigment, achieves better salt spray resistance than aluminum tripolyphosphate.

[0020] Preferably, the zinc phosphate has a zinc content of 45.0-49.0%, a phosphate content of 44.0-48.0%, and an oil absorption capacity of 15-25%.

[0021] Specifically, the rust-preventive pigment is zinc phosphate of type 409 (purchased from Jiangsu Shenlong Zinc Industry Co., Ltd.), with a zinc content of 45.0-49.0%, a phosphate content of 44.0-48.0%, and an oil absorption of 15-25%.

[0022] Filling material

[0023] In some embodiments of the present invention, the filler is barium sulfate.

[0024] Preferably, the barium sulfate has an oil absorption capacity of 15-25% and a pH of 6.5-9.0.

[0025] Specifically, the filler is barium sulfate sold by Hebei Xinji Chemical Co., Ltd., with a BaSO4 content ≥98%, an oil absorption capacity of 15-25, and a pH of 6.5-9.0.

[0026] Matting powder

[0027] In some embodiments of the present invention, the matting agent is silicon dioxide. The purpose of using matting agent in the present invention is to increase the thixotropic properties of the coating, so as to improve the paintability of the coating at the chamfered edge of the metal workpiece, increase the film thickness at that location, and thereby improve the corrosion resistance of that location.

[0028] Preferably, the specific surface area of ​​the silicon dioxide is 300 m². 2 / g, with an average particle size of 1.7–2.1 μm.

[0029] Specifically, the matting agent is silicon dioxide of type AZ 201 or AZ 204 (purchased from Tosoh Corporation).

[0030] Phosphate ester polymer

[0031] In some embodiments of the present invention, the phosphate polymer is an alkylaryl phosphate. The appropriate amount of phosphate polymer used in the present invention can improve the adhesion and salt spray resistance of the coating film on the metal substrate.

[0032] Specifically, the phosphate polymer is an alkylaryl phosphate with the model name Lubrizol 2062 (purchased from Lubrizol Company) and a non-volatile content of 59-66%.

[0033] Two-component flash rust inhibitor

[0034] In some embodiments of the present invention, the two-component flash rust inhibitor comprises component A and component B, wherein the mass ratio of component A to component B is 1:1. The use of the two-component flash rust inhibitor in the present invention can solve problems such as blistering, pitting, and through-rusting during salt spray treatment. Its mechanism is that the two-component flash rust inhibitor provides slow-release protection to the substrate.

[0035] Specifically, component A is selected from CHE L6NF or CHE L8NF (purchased from Tianjin Aoluoqi Chemical Technology Co., Ltd.), and is a mixed solution of inorganic acid and amine; component B is selected from CHE L6AF or CHE L8AF, and is one or a mixture of two sodium salts and potassium salts.

[0036] Auxiliary agent

[0037] In some embodiments of the present invention, the additive is selected from one or more of pH adjusters, leveling agents, defoamers, substrate wetting agents, or wetting and dispersing agents.

[0038] In a preferred embodiment of the present invention, the additives comprise, by weight:

[0039] pH adjuster 0.10–0.30 parts;

[0040] The leveling agent is used in an amount of 0.20 to 0.30 parts, preferably 0.20 to 0.25 parts, and more preferably 0.25 to 0.30 parts.

[0041] The defoamer is used in an amount of 0.10 to 0.30 parts, preferably 0.10 to 0.20 parts, and more preferably 0.20 to 0.30 parts;

[0042] The substrate wetting agent is 0.20 to 0.30 parts, preferably 0.20 to 0.25 parts, and more preferably 0.25 to 0.30 parts;

[0043] The wetting and dispersing agent is 1.60 to 2.40 parts, preferably 1.60 to 2.00 parts, and more preferably 2.00 to 2.40 parts;

[0044] The total weight of all the above components is 2.2 to 3.6 parts.

[0045] Specifically, the pH adjuster is dimethylethanolamine (purchased from BASF); the leveling agent is BYK381 (purchased from BYK); the defoamer is BYK 011 (purchased from BYK); the substrate wetting agent is TEGO 4100 (purchased from TEGO); and the wetting and dispersing agent is BYK 190 (purchased from BYK).

[0046] Solvent

[0047] In some embodiments of the present invention, the solvent is selected from at least one of ether solvents, alcohol solvents, and deionized water.

[0048] Preferably, the solvent is selected from two or more of ether solvents, alcohol solvents, and deionized water. Ether solvents and alcohol solvents have lower evaporation rates than deionized water and have good miscibility with deionized water, which can regulate the evaporation rate of the entire coating system and avoid abnormalities such as blistering / scalding during coating and baking.

[0049] More preferably, by weight, the solvent contains 4.0 to 6.0 parts of ether solvent and 11.0 to 12.0 parts of deionized water, wherein the ether solvent is selected from one or a combination of propylene glycol methyl ether and dipropylene glycol butyl ether, and the total weight of the above components is 15.0 to 18.0 parts.

[0050] A second aspect of the present invention provides a method for preparing the water-based protective coating composition described in the first aspect of the present invention, comprising the following steps:

[0051] (1) Add wetting and dispersing agent, defoamer and part of solvent into container A, stir at 300-500 r / min, add coloring pigment, anti-rust pigment, filler and matting powder while stirring, stir for about 20-30 min until it is evenly dispersed and there are no lumps, then stop stirring.

[0052] (2) Grind the mixture in container A to a fineness of ≤10μm;

[0053] (3) Add the remaining solvent to container B and stir at 200-300 r / min. Add waterborne epoxy resin A and waterborne epoxy resin B while stirring. Stir for 5-10 min. Then add the mixture in container A after sand milling, phosphate polymer, two-component flash rust inhibitor, substrate wetting agent, leveling agent, etc., and continue stirring for 10-15 min.

[0054] (4) Adjust the pH of the mixture obtained in step (3) to 8.5-9.0 using a pH adjuster to obtain the water-based protective coating composition.

[0055] A third aspect of the present invention provides an application of the aforementioned waterborne protective coating composition, specifically, an application suitable for coating automotive metal parts.

[0056] A fourth aspect of the present invention provides a water-based protective coating comprising the water-based protective coating composition described in the first aspect of the present invention.

[0057] The beneficial effects of this invention are as follows:

[0058] The waterborne protective coating composition provided by this invention uses two different waterborne self-drying epoxy resins as the main resin in a certain proportion, and adds coloring pigments, anti-rust pigments, matting powder, phosphate polymers, two-component flash rust inhibitors and other additives. The resulting waterborne protective coating composition can achieve rapid curing into a film by self-drying or low-temperature baking. It has good resistance to salt spray, volatile oil, water and high temperature adhesion. When sprayed on metal parts such as automotive brake discs, steering knuckles, and drive shafts, the cured paint film can reach a pencil hardness of F, a neutral salt spray resistance of 300h, a single-sided corrosion of <3mm, and can withstand water for 240h at 40℃ without bubbling or peeling. After high temperature of 350℃*2min, the adhesion is grade 0. Detailed Implementation

[0059] To illustrate the present invention more clearly, specific embodiments are described below. It should be understood that the following description is illustrative rather than restrictive and should not be construed as limiting the scope of protection of the present invention.

[0060] The water-based protective coating composition provided by the present invention uses water-based self-drying epoxy resin as the main resin, and is supplemented with appropriate amounts of fillers and matting powder to achieve rapid curing of the water-based protective coating composition into a film by self-drying or low-temperature baking.

[0061] Specifically, the purpose of using matting powder in this invention is to increase the thixotropic properties of the coating, thereby improving the paintability of the coating at the chamfered edge of the metal workpiece, increasing the film thickness at that location, and thus improving the corrosion resistance of that location.

[0062] Furthermore, the present invention also incorporates appropriate amounts of anti-rust pigments, phosphate polymers, two-component flash rust inhibitors, and additives, so that the water-based protective coating composition maintains its other properties while exhibiting good resistance to salt spray, volatile oils, water, and high-temperature adhesion.

[0063] On the one hand, the rust-inhibiting pigment used in this invention can further improve the salt spray resistance of the coating film, mainly by reducing the corrosion propagation at the X-shaped tangential part of the metal parts during the salt spray test. This is achieved by filling the coating film structure with its fine particles, improving the density of the coating film, playing a shielding role, reducing the permeability of the coating film, and thus playing a rust-preventing role. Preferably, zinc phosphate as a rust-inhibiting pigment achieves better salt spray resistance than aluminum tripolyphosphate as a rust-inhibiting pigment.

[0064] On the other hand, the two-component flash rust inhibitor used in this invention can solve problems such as blistering, pitting, and rust penetration that occur during salt spray treatment. The mechanism is that the two-component flash rust inhibitor plays a role in slow-release protection of the substrate.

[0065] Furthermore, the appropriate amount of phosphate polymer used in this invention can improve the adhesion of the coating film to the metal substrate and its salt spray resistance.

[0066] This water-based protective coating composition is suitable for simple air spraying, is easy to apply and operate, and has a fast surface drying rate. It is suitable for coating automotive metal parts such as brake discs, drive shafts and steering knuckles.

[0067] The technical solution of the present invention will be described below with reference to some more specific embodiments:

[0068] Related raw material model and manufacturer description

[0069] Waterborne epoxy resin A is EPICLON H-502-42W, purchased from D.E.S.;

[0070] The waterborne epoxy resin B is MODEPICS 304C, purchased from Arakawa Chemical Co., Ltd.

[0071] The coloring pigment was MITSUBISHI CARBON BLACK MA-100 carbon black, purchased from Mitsubishi Chemical.

[0072] The rust-preventive pigment is 409 zinc phosphate, purchased from Jiangsu Shenlong Zinc Industry Co., Ltd.

[0073] The filler material was barium sulfate, purchased from Xinji Chemical Plant in Hebei Province.

[0074] The matting agent is silicon dioxide AZ 201 or AZ 204, purchased from Tosoh Corporation;

[0075] Phosphate polymer Lubrizol 2062, purchased from Lubrizol Corporation;

[0076] Two-component flash rust inhibitors CHE L6NF and CHE L6AF, or CHE L8NF and CHE L8AF, were purchased from Tianjin Aoluoqi Chemical Technology Co., Ltd.

[0077] pH adjuster dimethylethanolamine, purchased from BASF;

[0078] Wetting and dispersing agent BYK 190, purchased from BYK Corporation;

[0079] The defoamer was BYK 011, purchased from BYK Corporation;

[0080] The substrate wetting agent was TEGO 4100, purchased from TEGO Corporation;

[0081] The leveling agent was BYK 381, purchased from BYK Corporation;

[0082] Example 1: Water-based protective coating composition 1

[0083] Waterborne protective coating composition 1 was prepared according to the formulation shown in Table 1 below:

[0084] Table 1. Raw material weight parts for Example 1

[0085]

[0086] The preparation process of the water-based protective coating composition 1 includes the following steps:

[0087] (1) Add 2.2 parts of wetting and dispersing agent, 0.2 parts of defoamer, 8 parts of deionized water, and 3.0 parts of propylene glycol methyl ether into container A, and stir at 400 r / min. While stirring, add 1.3 parts of carbon black, 6.8 parts of zinc phosphate, 9.1 parts of barium sulfate, and 2.0 parts of matting powder, and stir for about 20 to 30 minutes until the mixture is evenly dispersed and free of lumps.

[0088] (2) Grind the mixture in container A to a fineness of ≤10μm;

[0089] (3) Add 2.0 parts of dipropylene glycol butyl ether and the remaining 3.7 parts of deionized water to container B, stir at 300 r / min, add 40.5 parts of waterborne epoxy resin EPICLON H-502-42W and 19 parts of waterborne epoxy MODEPICS 304C, stir for 8 min, then add the mixture in container A after sand milling, 0.8 parts of phosphate polymer, 0.4 parts each of two-component flash rust inhibitors CHE L6NF and CHE L6AF, 0.2 parts of substrate wetting agent, 0.2 parts of leveling agent, etc., and continue stirring for 15 min;

[0090] (4) Adjust the pH of the mixture obtained in step (3) to 8.5-9.0 with 0.2 parts of the pH adjuster dimethylethanolamine to obtain the water-based protective coating composition 1.

[0091] Comparative Example 1: Waterborne Protective Coating Composition C1

[0092] Example 1 was repeated, except that commercially available waterborne acrylic modified epoxy resin LWEA-3250NP and other solids were used to replace waterborne epoxy resin A in Example 1, while the amounts of other materials remained unchanged.

[0093] It should be noted that the waterborne acrylic modified epoxy resin LWEA-3250NP used in this comparative example requires cross-linking and curing by the curing resin and cannot be self-drying. It is not within the scope of this invention. Therefore, this example is only comparative example 1. Using this type of epoxy resin will lead to a decrease in the adhesion, water resistance, volatile oil resistance and salt spray resistance of the coating. This is due to the poor adhesion of commercially available resins to metal substrates.

[0094] Comparative Example 2: Waterborne Protective Coating Composition C2

[0095] Example 1 was repeated, except that commercially available waterborne acrylic modified epoxy resin LWEA-3250NP and other solids were used to replace waterborne epoxy resin B in Example 1, while the amounts of other materials remained unchanged.

[0096] It should be noted that the waterborne acrylic modified epoxy resin LWEA-3250NP used in this comparative example requires cross-linking and curing by the curing resin and cannot be self-drying. It is not within the scope of this invention. Therefore, this example is only comparative example 2. Similar to comparative example 1, the use of this epoxy resin will lead to a decrease in the adhesion, water resistance and salt spray resistance of the coating. This is due to the poor adhesion of commercially available resins to metal substrates.

[0097] Comparative Example 3: Waterborne Protective Coating Composition C3

[0098] Comparative Example 3 is a commercially available water-based protective coating for ordinary metal parts.

[0099] It should be noted that the content of components such as anti-rust pigments and flash rust inhibitors in the water-based protective coating in this comparative example is not within the scope of this invention. Therefore, this example is only comparative example 3.

[0100] Comparative Example 4: Waterborne Protective Coating Composition C4

[0101] Example 1 was repeated, except that the amounts of waterborne epoxy resin A and waterborne epoxy resin B were used. The raw material weight parts of Comparative Example 4 are shown in Table 2.

[0102] Table 2 Comparative Example 4 Raw Material Weight Parts

[0103]

[0104] It should be noted that in this comparative example, the ratio of waterborne epoxy resin A to B is 4.95:1, which exceeds the upper limit of the dosage range of 2.3:1 and is not within the scope of this invention. Therefore, this example is only comparative example 4. An excessively high proportion of waterborne epoxy resin A will lead to a decrease in the water resistance of the paint film.

[0105] Comparative Example 5: Waterborne Protective Coating Composition C5

[0106] Example 1 was repeated, except that the amounts of waterborne epoxy resin A and waterborne epoxy resin B were used. The raw material weight parts of Comparative Example 5 are shown in Table 3.

[0107] Table 3 Comparative Example 5 Raw Material Weight Parts

[0108]

[0109] It should be noted that in this comparative example, the ratio of waterborne epoxy resin A to B is 1.05:1, which is lower than the lower limit of the dosage range of 2:1. Therefore, it is not within the scope of this invention, and this example is only comparative example 5. A low proportion of waterborne epoxy resin A will lead to a decrease in the salt spray resistance of the paint film.

[0110] Comparative Example 6: Waterborne Protective Coating Composition C6

[0111] Example 1 was repeated, except for the amount of waterborne epoxy resin A and anti-rust pigment used. The raw material weight parts of Comparative Example 6 are shown in Table 4.

[0112] Table 4 Comparative Example 6 Raw Material Weight Parts

[0113]

[0114] It should be noted that in this comparative example, the amount of the rust-preventive pigment used is 5.3 parts, which is lower than the lower limit of 6.3 parts, and therefore not within the scope of this invention. Thus, this example is merely comparative example 6. Insufficient use of the rust-preventive pigment will lead to a decrease in the salt spray resistance of the paint film.

[0115] Comparative Example 7: Waterborne Protective Coating Composition C7

[0116] Example 1 was repeated, except for the amount of waterborne epoxy resin B and the two-component flash rust inhibitor. The raw material weight parts of Comparative Example 7 are shown in Table 5.

[0117] Table 5 Comparative Example 7 Raw Material Weight Parts

[0118]

[0119] It should be noted that in this comparative example, the amount of the two-component flash rust inhibitor is 0.4 parts, which is lower than the lower limit of 0.6 parts, and therefore not within the scope of this invention. Thus, this example is only Comparative Example 7. Insufficient dosage of the two-component flash rust inhibitor will lead to a decrease in the salt spray resistance of the paint film.

[0120] Test Example 1: Performance Testing of Waterborne Protective Coating Compositions

[0121] Substrate: Automotive brake disc workpiece (cast iron, silane pretreatment).

[0122] Coating process: Air gun spraying, spraying viscosity 26.0-30.0″ / 20℃*Ford cup 4.

[0123] Coating composition: Automotive brake disc workpiece + water-based protective coating composition.

[0124] After the brake disc workpiece coating is baked at 80℃ for 30 minutes (effective surface temperature of the workpiece), it is naturally cured at room temperature for 7 days to obtain a water-based protective coating for automotive metal parts.

[0125] Due to the different production process conditions for different automotive metal parts, the baking conditions for some automotive metal parts are 120℃*15min (effective surface temperature of the workpiece). Under these baking conditions, the natural curing of the workpiece at room temperature can be shortened to 4 days.

[0126] The performance testing methods are shown in Table 6:

[0127] Table 6 Performance Testing Methods

[0128]

[0129] The performance of the waterborne protective coating compositions in Example 1 and Comparative Examples 1-7 was tested using the above method, and the results are shown in Tables 7 and 8.

[0130] Table 7 Performance of Baking Varnish in Examples 1 and Comparative Examples 1-3

[0131]

[0132] Table 8 shows the performance of the baking varnishes in Comparative Examples 4–7.

[0133]

[0134] The test results in Tables 7 and 8 above show that:

[0135] (1) When the water-based protective coating composition of the present invention is sprayed under standard construction conditions, the appearance of the paint film is normal and the performance of the coating film meets the technical requirements.

[0136] (2) In Comparative Example 1, commercially available waterborne acrylic modified epoxy resin LWEA-3250NP and other solids were used to replace waterborne epoxy resin A in Example 1, resulting in failure to meet the requirements for adhesion, water resistance, volatile oil resistance and neutral salt spray. This was due to the poor adhesion of the commercially available resin to the metal substrate.

[0137] (3) In Comparative Example 2, commercially available waterborne acrylic modified epoxy resin LWEA-3250NP and other solids were used to replace the waterborne epoxy resin B in Example 1, which resulted in failure to meet the requirements for adhesion, water resistance and neutral salt spray, for the same reason as Comparative Example 1.

[0138] (4) Comparative Example 3 is a commercially available water-based protective coating, which failed the tests for pencil hardness, neutral salt spray, and high-temperature compactness / salt spray.

[0139] (5) In Comparative Example 4, the ratio of waterborne epoxy resin A to B exceeded the upper limit of the dosage range of 2.3:1, which resulted in poor water resistance of the paint film and made it unqualified.

[0140] (6) In Comparative Example 5, the ratio of waterborne epoxy resin A to B was lower than the lower limit of the dosage range of 2.0:1, which resulted in the failure of neutral salt spray performance.

[0141] (7) The amount of anti-rust pigment in Comparative Example 6 was lower than the lower limit of the dosage range of 6.3 parts, resulting in rust corrosion of X-shaped tangent >3mm and unqualified neutral salt spray performance.

[0142] (8) The amount of the two-component flash rust inhibitor in Comparative Example 7 was lower than the lower limit of the dosage range of 0.8 parts. Although the rust corrosion of the X-shaped tangent was <3mm, bubbles and pitting rust appeared in the area outside the X-shaped tangent, and the neutral salt spray performance was still unqualified.

[0143] Example 2: Water-based protective coating composition 2

[0144] Example 1 was repeated, except that the two-component flash rust inhibitor was CHE L8NF and CHE L8AF. The raw material weight parts for Example 2 are shown in Table 9.

[0145] Table 9. Raw material weight parts for Example 2

[0146]

[0147] Example 3: Water-based protective coating composition 3

[0148] Example 1 was repeated, except that the matting agent was AZ 204. The raw material weight parts for Example 3 are shown in Table 10.

[0149] Table 10. Raw material weight parts for Example 3

[0150]

[0151] Example 4: Water-based protective coating composition 4

[0152] Example 1 was repeated, except that the matting agent was AZ 204 and the two-component flash rust inhibitor was CHE L8NF and CHE L8AF. The raw material weight parts of Example 4 are shown in Table 11.

[0153] Table 11. Raw material weight parts for Example 4

[0154]

[0155] Example 5: Water-based protective coating composition 5

[0156] Example 1 was repeated, except that the weight ratio of waterborne epoxy resins A and B was 2.3:1.

[0157] Example 6: Water-based protective coating composition 6

[0158] Example 1 was repeated, except that the weight ratio of waterborne epoxy resins A and B was 2.0:1.

[0159] Example 7: Water-based protective coating composition 7

[0160] Example 1 was repeated, except for the amounts of waterborne epoxy resin A and rust-inhibiting pigment zinc phosphate. The raw material weight parts for Example 7 are shown in Table 12.

[0161] Table 12. Raw material weight parts for Example 1

[0162]

[0163] Example 8: Water-based protective coating composition 8

[0164] Example 1 was repeated, except for the amounts of waterborne epoxy resin B and rust-inhibiting pigment zinc phosphate. The raw material weight parts for Example 8 are shown in Table 13.

[0165] Table 13. Raw material weight parts for Example 1

[0166]

[0167] Example 9: Water-based protective coating composition 9

[0168] Example 1 was repeated, except for the amounts of waterborne epoxy resin A, waterborne epoxy resin B, rust-inhibiting pigment zinc phosphate, and filler barium sulfate. The raw material weight parts for Example 9 are shown in Table 14.

[0169] Table 14. Raw material weight parts for Example 1

[0170]

[0171] Example 10: Water-based protective coating composition 10

[0172] Example 1 was repeated, except for the amounts of waterborne epoxy resin A, waterborne epoxy resin B, rust-inhibiting pigment zinc phosphate, filler barium sulfate, matting agent, phosphate ester polymer, two-component flash rust inhibitor, and propylene glycol methyl ether. The raw material weight parts for Example 10 are shown in Table 15.

[0173] Table 15. Raw material weight parts for Example 1

[0174]

[0175] Following the method described in Example 1 above, the main coating properties of the waterborne protective coating compositions in Examples 2 to 10 were tested. The test results are shown in Table 16. The test results are similar to those in Example 1, indicating that the components and proportions of the waterborne protective coating compositions specified in this invention can achieve the purpose of the invention.

[0176] Table 16 Main parameters of water-based protective coatings in Examples 2-10

[0177] Examples Adhesion Pencil hardness Water resistance Middle salt spray Example 2 100 / 100 no flaking F No abnormality Linear rust 1 mm Example 3 100 / 100 no flaking F No abnormality Linear rust 2 mm Example 4 100 / 100 no flaking F No abnormality Linear rust 1 mm Example 5 100 / 100 no flaking F No abnormality Linear rust 1 mm Example 6 100 / 100 no flaking F No abnormality Linear rust 1 mm Example 7 100 / 100 no flaking F No abnormality Linear rust 1 mm Example 8 100 / 100 no flaking F No abnormality Linear rust 2 mm Example 9 100 / 100 no flaking F No abnormality Linear rust 2 mm Example 10 100 / 100 no flaking H No abnormality Linear rust <1 mm

[0178] Comparative Example 8: Waterborne Protective Coating Composition C8

[0179] The raw material formulation of Comparative Example 8 is the same as that of Example 1, except that in the preparation process of the waterborne protective coating composition C8, a portion of the waterborne epoxy resin, matting powder, pigments, and fillers are ground and dispersed together. The specific steps are as follows.

[0180] (1) Add 2.2 parts of wetting and dispersing agent, 0.2 parts of defoamer, 8 parts of deionized water, and 3.0 parts of propylene glycol methyl ether to container A, and stir at 400 r / min. While stirring, add 20 parts of waterborne epoxy resin EPICLON H-502-42W, 1.3 parts of carbon black, 6.8 parts of zinc phosphate, 9.1 parts of barium sulfate, and 2.0 parts of matting powder. Stir for about 20 to 30 minutes until the mixture is evenly dispersed and free of lumps, then stop stirring.

[0181] (2) Grind the mixture in container A to a fineness of ≤10μm;

[0182] (3) Add 2.0 parts of dipropylene glycol butyl ether and the remaining 3.7 parts of deionized water to container B, stir at 300 r / min, and then add the mixture after sand milling in container A, 20.5 parts of waterborne epoxy resin EPICLON H-502-42W and 19.0 parts of waterborne epoxy resin MODEPICS 304C, 0.8 parts of phosphate polymer, 0.4 parts each of two-component flash rust inhibitors CHE L6NF and CHE L6AF, 0.2 parts of substrate wetting agent, 0.2 parts of leveling agent, etc., and continue stirring for 15 min;

[0183] (4) Adjust the pH of the mixture obtained in step (3) to 8.5-9.0 with 0.2 parts of pH adjuster dimethylethanolamine to obtain the water-based protective coating composition.

[0184] As mentioned above, in this comparative example, the preparation process involved grinding and dispersing a portion of the waterborne epoxy resin, matting agent, pigment, and filler together. This process is not within the scope of this invention, and therefore this example is only comparative example 8. It should be noted that this comparative example illustrates that neither waterborne epoxy resin A nor B can participate in the grinding process. Regardless of the amount of waterborne epoxy resin in step (1), it will cause flocculation in the waterborne protective coating, demonstrating that the preparation method of this invention can effectively prevent clumping.

[0185] Comparative Example 9: Waterborne Protective Coating Composition C9

[0186] The raw material formulation of Comparative Example 9 is the same as that of Example 1, except that the two-component flash rust inhibitor is mixed in advance and then added together into container B.

[0187] It should be noted that in this comparative example, the preparation process involved pre-mixing the two-component flash rust inhibitor before adding them together into container B, rather than adding them sequentially as described in this invention. Therefore, this method is not within the scope of this invention, and this example is only comparative example 9. The resulting waterborne protective coating exhibits poorer resistance to neutral salt spray.

[0188] 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 protective coating composition, comprising, by weight, the following components: 56.1 to 61.3 parts of waterborne epoxy resin Coloring pigment 1.1 ~ 1.5 parts Rust-preventive pigment: 6.3 ~ 7.3 parts 8.6 ~ 9.6 parts of filler Matte powder 1.0 ~ 3.0 parts Phosphate ester polymer 0.5 ~ 1.0 parts Two-component flash rust inhibitor, 0.6 ~ 1.0 parts 2.2 to 3.6 parts of additives Solvent 15.0 ~ 18.0 parts, The total weight of all the above components is 100 parts; characterized in that, The waterborne epoxy resin comprises two different waterborne epoxy resins, A and B, wherein the weight ratio of waterborne epoxy resin A to waterborne epoxy resin B is 2:1 to 2.3:

1. The waterborne epoxy resin A is a waterborne epoxy resin of model EPICLON H-502-42W provided by D.E.S., with a non-volatile content of 37.0-41.0%, a viscosity of 500-10000 mPa.s, and a pH of 8-11. The waterborne epoxy resin B is MODEPICS 304C, supplied by Arakawa Chemical Co., Ltd., with a non-volatile content of 35.0-38.0%, a viscosity of 1500 mPa.s, and a pH of 9-11.

2. The water-based protective coating composition as described in claim 1, characterized in that, The coloring pigment is carbon black, the anti-rust pigment is zinc phosphate, the filler is barium sulfate, and the matting agent is silicon dioxide.

3. The water-based protective coating composition as described in claim 2, characterized in that, The zinc phosphate has a zinc content of 45.0-49.0%, a phosphate content of 44.0-48.0%, and an oil absorption capacity of 15-25%. The barium sulfate has an oil absorption capacity of 15-25%, a pH of 6.5-9.0, and the silica has a specific surface area of ​​300 m². 2 / g, with an average particle size of 1.7 ~ 2.1 μm.

4. The water-based protective coating composition as described in claim 1, characterized in that, The phosphate polymer is an alkylaryl phosphate.

5. The water-based protective coating composition as described in claim 1, characterized in that, The two-component flash rust inhibitor includes component A and component B. Component A is a mixed solution of inorganic acid and amine, and component B is one or a mixture of two sodium salts and potassium salts. The weight ratio of component A to component B is 1:

1.

6. The water-based protective coating composition according to claim 1, characterized in that, The additives are selected from one or more of pH adjusters, leveling agents, defoamers, substrate wetting agents, or wetting and dispersing agents.

7. The water-based protective coating composition as described in claim 6, characterized in that, The additives comprise, by weight: pH adjuster 0.10 ~ 0.30 parts; Leveling agent 0.20 ~ 0.30 parts; Defoamer 0.10~0.30 parts; Substrate wetting agent: 0.20 ~ 0.30 parts; 1.60 ~ 2.40 parts of wetting and dispersing agent; The total weight of all the above components is 2.2 to 3.6 parts.

8. The water-based protective coating composition as described in claim 1, characterized in that, The adjuvant contains: pH adjuster 0.10 ~ 0.30 parts; Leveling agent 0.25 ~ 0.30 parts; Defoamer 0.20 ~ 0.30 parts; Substrate wetting agent: 0.25 ~ 0.30 parts; Wetting and dispersing agent 2.00 ~ 2.40 parts.

9. The water-based protective coating composition according to claim 1, characterized in that, The solvent is selected from one or more of ether solvents, alcohol solvents, or deionized water.

10. The water-based protective coating composition as described in claim 9, characterized in that, The solvent is selected from two or more of the following: ether solvents, alcohol solvents, or deionized water.

11. The water-based protective coating composition as described in claim 9, characterized in that, By weight, the solvent contains 4.0 to 6.0 parts of ether solvent and 11.0 to 12.0 parts of deionized water. The ether solvent is selected from one or a combination of propylene glycol methyl ether and dipropylene glycol butyl ether. The total weight of the above components is 15.0 to 18.0 parts.

12. A method for preparing a water-based protective coating composition according to any one of claims 1 to 11, comprising the following steps: (1) Add part of the additives and part of the solvent into container A, stir at 300 ~ 500 r / min, add coloring pigment, anti-rust pigment, filler and matting powder while stirring, stir for 20 ~ 30 min until it is evenly dispersed and there are no lumps, then stop stirring. (2) Grind the mixture in container A to a fineness ≤ 10 μm; (3) Add the remaining solvent to container B and stir at 200-300 r / min. Add waterborne epoxy resin and stir for 5-10 min. Then add the mixture, phosphate polymer, two-component flash rust inhibitor and remaining additives to container A after sand milling in sequence and continue stirring for 10-15 min. (4) Adjust the pH of the mixture obtained in step (3) to 8.5 ~ 9.0 to obtain the water-based protective coating composition.

13. The application of a water-based protective coating composition as described in any one of claims 1 to 11, characterized in that, The water-based protective coating composition is suitable for coating automotive metal parts such as brake discs, drive shafts, and steering knuckles.

14. A water-based protective coating, characterized in that, The water-based protective coating comprises the water-based protective coating composition according to any one of claims 1 to 11.

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