Anti-floating silver gray finish paint for automobile refinishing paint and preparation method of anti-floating silver gray finish paint

Abstract

The invention relates to the technical field of paint, and discloses anti-floating silver gray finish paint for automobile refinishing paint and a preparation method thereof. The finishing paint is prepared from unsaturated polyester resin, maleic acid monoester aldehyde ketone resin, a diluent, a curing agent, a curing accelerator, an oxygen barrier, a defoaming agent, a flatting agent and aluminum paste according to the proportion of 100g: (20 to 35) g: (8 to 14) g: (1.8 to 2.6) g: (0.6 to 0.8) g: (0.02 to 0.04) g: (0.4 to 0.8) g: (0.3 to 0.6) g: (4 to 12) g. The maleic acid monoester aldehyde ketone resin and the unsaturated polyester resin have good compatibility and interface bonding strength, so that a paint film of the paint has better impact resistance, wear resistance and the like, meanwhile, the dispersity of aluminum powder of aluminum paste in the paint can be improved, the appearance flatness and smoothness and flooding and floating resistance of the paint film are improved, and the service life of the paint film is prolonged. And the paint film has better protective effects such as wear resistance and the like on the automobile.

Description

Technical Field

[0001] This invention relates to the field of coating technology, specifically to an anti-blooming silver-gray topcoat for automotive repair paint and its preparation method. Background Technology

[0002] Silver-gray metallic coatings are typically composed of resins, aluminum silver paste, and other metallic pigments. They have a unique appearance and texture, good rust and corrosion resistance, and are widely used in automotive coatings and other fields. However, the dispersion of metallic pigments such as aluminum silver paste in coatings is poor, which can result in alternating light and dark patterns and uneven color, leading to floating color and mottled appearance, which affects the aesthetic appeal.

[0003] Unsaturated polyester resins possess excellent mechanical properties, high chemical resistance, and good film-forming properties, allowing for good alignment of aluminum powder and making them important in automotive paints and coatings. Aldehyde-ketone resins are excellent coating additives, exhibiting properties such as fast drying, weather resistance, lightfastness, high hardness, and resistance to clear coat erosion, effectively preventing topcoat blooming. However, phenolic resins have poor compatibility with unsaturated polyester resins, which can affect coating performance. Summary of the Invention

[0004] (i) This invention solves the problem of poor anti-staining and wear-resistant properties of unsaturated polyester resin.

[0005] (II) Technical Solution: A silver-gray topcoat for automotive repair paint that prevents blooming, the topcoat comprising unsaturated polyester resin, maleic acid monoester aldehyde-ketone resin, diluent, curing agent, curing accelerator, oxygen barrier, defoamer, leveling agent, and aluminum silver paste in a ratio of 100g:(20-35)g:(8-14)g:(1.8-2.6)g:(0.6-0.8)g:(0.02-0.04)g:(0.4-0.8)g:(0.3-0.6)g:(4-12)g.

[0006] The preparation method of the topcoat is as follows: (1) Dichloromethane, 4-hydroxymethylcyclohexanone, maleic anhydride, and 4-dimethylaminopyridine were added to the reaction flask. After stirring and reacting, the mixture was distilled under reduced pressure. The crude product was separated by silica gel column chromatography to obtain 4-(maleic acid monoester methyl)cyclohexanone. The reaction formula is as follows: .

[0007] (2) Add an aqueous solution of cyclohexanone, 4-(maleic acid monoester methyl)cyclohexanone, and formaldehyde to a reaction flask equipped with a reflux condenser and a water separator. After stirring, add an aqueous solution of sodium hydroxide dropwise, stir the reaction, adjust the pH by adding acid, extract with ethyl acetate, distill the organic phase of ethyl acetate under reduced pressure, and dry to obtain maleic acid monoester aldehyde-ketone resin. The reaction formula is: .

[0008] (3) Add maleic acid monoester aldehyde ketone resin and aluminum silver paste to the high-speed disperser, shear and disperse, then add unsaturated polyester resin, diluent, oxygen barrier, defoamer and leveling agent, shear and disperse, and finally add curing agent and curing accelerator to obtain anti-blooming silver gray topcoat for automotive repair paint.

[0009] Preferably, the ratio of 4-hydroxymethylcyclohexanone, maleic anhydride, and 4-dimethylaminopyridine in (1) is 1 mol: (1.2-1.4) mol: (0.3-0.4) mol.

[0010] Preferably, the reaction temperature in (1) is 20-35℃ and the reaction time is 4-6h.

[0011] Preferably, the ratio of cyclohexanone, 4-(maleic acid monoester methyl)cyclohexanone, formaldehyde, and sodium hydroxide in (2) is (0.84-0.92) mol: (0.08-0.16) mol: (1.1-1.4) mol: (0.13-0.23) mol.

[0012] Preferably, the temperature during the stirring reaction in (2) is 90-100℃ and the reaction time is 2-3h.

[0013] Preferably, in (2), acid solution is added dropwise to adjust the pH to 6.5-7.

[0014] Preferably, in (2), the acid solution is an aqueous solution of oxalic acid or an aqueous solution of citric acid.

[0015] Preferably, the diluent in (3) is styrene.

[0016] Preferably, the curing agent in (3) is methyl ethyl ketone peroxide.

[0017] Preferably, the curing accelerator in (3) is cycloalkane cobalt acid.

[0018] Preferably, the oxygen barrier in (3) is paraffin.

[0019] Preferably, the temperature of the first shear dispersion in (3) is 20-30℃ and the time is 2-4h.

[0020] Preferably, the temperature of the first shear dispersion in (3) is 20-30℃ and the time is 20-40min.

[0021] (III) Beneficial Technical Effects: This invention involves a polycondensation reaction of cyclohexanone, 4-(maleic acid monoester methyl)cyclohexanone, and formaldehyde to obtain a maleic acid monoester-based aldehyde-ketone resin. This resin is then compounded with aluminum silver paste, unsaturated polyester resin, diluent, curing agent, etc., to obtain an anti-blooming silver-gray topcoat for automotive repair paint. This maleic acid monoester-based aldehyde-ketone resin contains ester groups and alkenyl groups. The ester groups can improve the compatibility between the aldehyde-ketone resin and the unsaturated polyester resin. At the same time, the alkenyl groups can undergo cross-linking polymerization with the unsaturated polyester resin and styrene, further improving the interfacial bonding strength between the aldehyde-ketone resin and the unsaturated polyester resin. This results in better mechanical and other properties of the unsaturated polyester resin coating film, which is beneficial for improving impact resistance, abrasion resistance, and adhesion. This allows the paint film to provide better abrasion protection for automobiles.

[0022] The maleic acid monoester aldehyde-ketone resin of the present invention contains carboxylate groups, which interact with the surface of aluminum powder in aluminum silver paste, and can act as a dispersant to improve the dispersibility of aluminum powder in unsaturated polyester resin coatings. This improves the smoothness and anti-floating properties of the paint film, and the uniform dispersion of aluminum silver paste in the paint film can reduce the impact on the mechanical properties of the paint film, thereby maintaining good impact resistance, abrasion resistance and adhesion. Attached Figure Description

[0023] Figure 1 The infrared spectrum is that of the maleic acid monoester aldehyde ketone resin prepared in Example 1. Detailed Implementation

[0024] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0025] Example 1: (1) Add 300 mL of dichloromethane, 0.1 mol of 4-hydroxymethylcyclohexanone, 0.14 mol of maleic anhydride and 0.03 mol of 4-dimethylaminopyridine to the reaction flask, stir the reaction at 20 °C for 6 h, distill under reduced pressure, separate the crude product by silica gel column chromatography, and use petroleum ether and ethyl acetate solution as the mobile phase to obtain 4-(maleic acid monoester methyl)cyclohexanone.

[0026] (2) Add 0.92 mol cyclohexanone, 0.08 mol 4-(maleic acid monoester methyl)cyclohexanone, and 34 mL of aqueous solution containing 1.2 mol formaldehyde to a reaction flask equipped with a reflux condenser and a water separator. After stirring, add 12 mL of aqueous solution containing 0.13 mol sodium hydroxide. Heat to 100 °C and stir for 2 h. Adjust the pH to 6.5 by adding 40% citric acid aqueous solution. Extract with ethyl acetate. Distill the organic phase of ethyl acetate under reduced pressure and dry to obtain maleic acid monoester aldehyde ketone resin. Figure 1 The infrared spectrum shows 2957-2853 cm⁻¹ -1 It is the characteristic peak of methylene-CH2- in aldehyde and ketone resins, at 1735 cm⁻¹. -1 The absorption peak is at the C=O group of the ester group, 1641 cm⁻¹. -1 The absorption peak of the alkenyl group.

[0027] (3) Add 200g of maleic acid monoester aldehyde ketone resin and 40g of aluminum silver paste to a high-speed disperser and shear disperse at 20℃ for 3h. Then add 1000g of unsaturated polyester resin (model Langfang Aiyuan 196 unsaturated resin), 110g of diluent styrene, 0.2g of oxygen barrier paraffin, 5g of defoamer (model Yilian Chemical 2608, the same below), and 6g of leveling agent (Shanghai Huiyan HY-527, the same below). Shear disperse at 20℃ for 40min. Finally, add 20g of curing agent methyl ethyl ketone peroxide and 0.67g of curing accelerator naphthenic acid to obtain an anti-blooming silver-gray topcoat for automotive repair paint.

[0028] Example 2: (1) Add 300 mL of dichloromethane, 0.1 mol of 4-hydroxymethylcyclohexanone, 0.2 mol of maleic anhydride and 0.04 mol of 4-dimethylaminopyridine to the reaction flask, stir and react at 35 °C for 4 h, distill under reduced pressure, separate the crude product by silica gel column chromatography, and use petroleum ether and ethyl acetate solution as the mobile phase to obtain 4-(maleic acid monoester methyl)cyclohexanone.

[0029] (2) Add 0.9 mol cyclohexanone, 0.1 mol 4-(maleic acid monoester methyl)cyclohexanone, and 31 mL of aqueous solution containing 1.1 mol formaldehyde to a reaction flask equipped with a reflux condenser and a water separator. After stirring, add 18 mL of aqueous solution containing 0.16 mol sodium hydroxide. Heat to 90 °C and stir for 3 h. Adjust the pH to 7 by adding 2% oxalic acid aqueous solution. Extract with ethyl acetate. Distill the organic phase of ethyl acetate under reduced pressure and dry to obtain maleic acid monoester aldehyde ketone resin.

[0030] (3) Add 250g of maleic acid monoester aldehyde ketone resin and 65g of aluminum silver paste to a high-speed disperser and shear disperse at 30℃ for 3h. Then add 1000g of unsaturated polyester resin, 80g of diluent styrene, 0.3g of oxygen barrier paraffin, 8g of defoamer and 3g of leveling agent and shear disperse at 30℃ for 20min. Finally add 18g of curing agent methyl ethyl ketone peroxide and 0.8g of curing accelerator naphthenic acid to obtain an anti-blooming silver-gray topcoat for automotive repair paint.

[0031] Example 3: (1) Add 0.87 mol cyclohexanone, 0.13 mol 4-(maleic acid monoester methyl)cyclohexanone (prepared from Example 1), and 39 mL of aqueous solution containing 1.4 mol formaldehyde to a reaction flask equipped with a reflux condenser and a water separator. After stirring, add 20 mL of aqueous solution containing 0.2 mol sodium hydroxide. Heat to 100°C and stir for 3 h. Adjust the pH to 6.5 by adding 40% citric acid aqueous solution. Extract with ethyl acetate. Distill the organic phase of ethyl acetate under reduced pressure and dry to obtain maleic acid monoester aldehyde ketone resin.

[0032] (2) Add 300g of maleic acid monoester aldehyde ketone resin and 90g of aluminum silver paste to a high-speed disperser and shear disperse at 20℃ for 4h. Then add 1000g of unsaturated polyester resin, 140g of diluent styrene, 0.2g of oxygen barrier paraffin, 4g of defoamer and 5g of leveling agent and shear disperse at 20℃ for 40min. Finally add 25g of curing agent methyl ethyl ketone peroxide and 0.8g of curing accelerator naphthenic acid to obtain an anti-blooming silver-gray topcoat for automotive repair paint.

[0033] Example 4: (1) Add 0.84 mol cyclohexanone, 0.16 mol 4-(maleic acid monoester methyl)cyclohexanone (prepared from Example 1), and 34 mL of aqueous solution containing 1.2 mol formaldehyde to a reaction flask equipped with a reflux condenser and a water separator. After stirring, add 25 mL of aqueous solution containing 0.23 mol sodium hydroxide. Heat to 90 °C and stir for 3 h. Adjust the pH to 7 by adding 40% citric acid aqueous solution. Extract with ethyl acetate. Distill the organic phase of ethyl acetate under reduced pressure and dry to obtain maleic acid monoester aldehyde ketone resin.

[0034] (2) Add 350g of maleic acid monoester aldehyde ketone resin and 120g of aluminum silver paste to a high-speed disperser and shear disperse at 30℃ for 2h. Then add 1000g of unsaturated polyester resin, 130g of diluent styrene, 0.4g of oxygen barrier paraffin, 8g of defoamer and 4g of leveling agent and shear disperse at 30℃ for 30min. Finally add 26g of curing agent methyl ethyl ketone peroxide and 0.6g of curing accelerator naphthenic acid to obtain an anti-blooming silver-gray topcoat for automotive repair paint.

[0035] Comparative Example 1 differs from Example 1 in that cyclohexanone is used instead of 4-(maleic acid monoester methyl)cyclohexanone.

[0036] (1) Add 0.1 mol cyclohexanone and 34 mL of aqueous solution containing 1.2 mol formaldehyde to a reaction flask equipped with a reflux condenser and a water separator. After stirring, add 12 mL of aqueous solution containing 0.13 mol sodium hydroxide. Heat to 100°C and stir for 2 h. Adjust the pH to 6.5 by adding 40% citric acid aqueous solution. Extract with ethyl acetate. Distill the organic phase of ethyl acetate under reduced pressure and dry to obtain aldehyde-ketone resin.

[0037] (2) Add 200g of aldehyde-ketone resin and 40g of aluminum silver paste to a high-speed disperser and shear disperse at 20℃ for 3h. Then add 1000g of unsaturated polyester resin, 110g of diluent styrene, 0.2g of oxygen barrier paraffin, 5g of defoamer and 6g of leveling agent and shear disperse at 20℃ for 40min. Finally add 20g of curing agent methyl ethyl ketone peroxide and 0.67g of curing accelerator cycloalkane cobalt acid to obtain silver-gray topcoat.

[0038] Comparative Example 2 differs from Example 1 in that 4-cyclohexanone carboxylic acid (CAS No. 874-61-3) is used instead of 4-(maleic acid monoester methyl)cyclohexanone.

[0039] (1) Add 0.92 mol cyclohexanone, 0.08 mol 4-cyclohexanone carboxylic acid, and 34 mL of aqueous solution containing 1.2 mol formaldehyde to a reaction flask equipped with a reflux condenser and a water separator. After stirring, add 12 mL of aqueous solution containing 0.13 mol sodium hydroxide. Heat to 100 °C and stir for 2 h. Adjust the pH to 6.5 by adding 40% citric acid aqueous solution. Extract with ethyl acetate. Distill the organic phase of ethyl acetate under reduced pressure and dry to obtain carboxylate aldehyde ketone resin.

[0040] (2) Add 200g of carboxylate aldehyde ketone resin and 40g of aluminum silver paste to a high-speed disperser and shear disperse at 20℃ for 3h. Then add 1000g of unsaturated polyester resin, 110g of diluent styrene, 0.2g of oxygen barrier paraffin, 5g of defoamer and 6g of leveling agent and shear disperse at 20℃ for 40min. Finally add 20g of curing agent methyl ethyl ketone peroxide and 0.67g of curing accelerator cycloalkane cobalt acid to obtain silver-gray topcoat.

[0041] Comparative Example 3 differs from Example 1 in that ethyl p-cyclohexanone carboxylate (CAS No. 17159-79-4) is used instead of 4-(maleic acid monoester methyl)cyclohexanone.

[0042] (1) Add 0.92 mol cyclohexanone, 0.08 mol ethyl p-cyclohexanone formate, and 34 mL of aqueous solution containing 1.2 mol formaldehyde to a reaction flask equipped with a reflux condenser and a water separator. After stirring, add 12 mL of aqueous solution containing 0.13 mol sodium hydroxide. Heat to 100 °C and stir for 2 h. Adjust the pH to 6.5 by adding 40% citric acid aqueous solution. Extract with ethyl acetate. Distill the organic phase of ethyl acetate under reduced pressure and dry to obtain ethyl formate-based aldehyde-ketone resin.

[0043] (2) Add 200g of ethyl formate-based aldehyde-ketone resin and 40g of aluminum silver paste to a high-speed disperser and shear disperse at 20℃ for 3h. Then add 1000g of unsaturated polyester resin, 110g of diluent styrene, 0.2g of oxygen barrier paraffin, 5g of defoamer, and 6g of leveling agent and shear disperse at 20℃ for 40min. Finally add 20g of curing agent methyl ethyl ketone peroxide and 0.67g of curing accelerator cycloalkane cobalt acid to obtain a silver-gray topcoat.

[0044] A silver-gray topcoat was sprayed onto the tinplate substrate and baked at 40℃ for 24 hours to form a paint film. The smoothness and appearance of the paint film were visually inspected. Impact resistance was tested according to GB / T 1732-2020 standard. Abrasion resistance was tested according to GB / T 1768-2006 standard. Adhesion was tested according to GB / T 9286-2021 standard.

[0045] Table 1 Performance of Coatings

[0046] Compared with Comparative Examples 1-3, the coating films of Examples 1-4 are smooth and even, without color floating or blooming, and have good impact resistance, abrasion resistance, and adhesion. This is mainly because the maleic acid monoester-based aldehyde-ketone resin prepared with 4-(maleic acid monoester methyl)cyclohexanone as the polymerizing monomer contains ester and alkenyl groups. The ester groups can improve the compatibility of the aldehyde-ketone resin with the unsaturated polyester resin, while the alkenyl groups can undergo cross-linking polymerization with the unsaturated polyester resin and styrene, further improving the interfacial bonding strength between the aldehyde-ketone resin and the unsaturated polyester resin. This results in the unsaturated polyester resin coating film having better mechanical properties, which is beneficial for improving impact resistance, abrasion resistance, and adhesion. Meanwhile, the maleic acid monoester aldehyde-ketone resin contains carboxylate groups, which interact with the surface of aluminum powder in the aluminum silver paste. It can act as a dispersant to improve the dispersibility of aluminum silver paste and aluminum powder in unsaturated polyester resin coatings, thereby improving the appearance, smoothness, and anti-floating and anti-blooming properties of the paint film. Furthermore, the uniform dispersion of aluminum silver paste in the paint film can reduce the impact on the mechanical properties of the paint film, thus maintaining good impact resistance, abrasion resistance, and adhesion.

[0047] The above embodiments are merely illustrative examples of the present invention. The present invention may also be implemented in other specific ways or forms without departing from the spirit or essential characteristics of the invention. Therefore, the described embodiments should be regarded as illustrative rather than limiting in any respect.

Claims

1. A silver-gray topcoat for automotive refinishing, characterized in that, The topcoat comprises unsaturated polyester resin, maleic acid monoester aldehyde-ketone resin, diluent, curing agent, curing accelerator, oxygen barrier, defoamer, leveling agent, and aluminum silver paste in a ratio of 100g:(20-35)g:(8-14)g:(1.8-2.6)g:(0.6-0.8)g:(0.02-0.04)g:(0.4-0.8)g:(0.3-0.6)g:(4-12)g. The preparation method of the maleic acid monoester aldehyde-ketone resin includes: adding an aqueous solution of cyclohexanone, 4-(maleic acid monoester methyl)cyclohexanone, and formaldehyde to a reaction flask equipped with a reflux condenser and a water separator; stirring and then adding an aqueous solution of sodium hydroxide dropwise; stirring and reacting; adding acid solution to adjust the pH; extracting and then distilling under reduced pressure; and drying to obtain the maleic acid monoester aldehyde-ketone resin.

2. The anti-blooming silver-gray topcoat for automotive refinish paint according to claim 1, characterized in that, The diluent is styrene; the curing agent is methyl ethyl ketone peroxide; the curing accelerator is naphthenic cobalt acid; and the oxygen barrier is paraffin wax.

3. The anti-blooming silver-gray topcoat for automotive refinish paint according to claim 1, characterized in that, The ratio of cyclohexanone, 4-(maleic acid monoester methyl)cyclohexanone, formaldehyde, and sodium hydroxide is (0.84-0.92) mol: (0.08-0.16) mol: (1.1-1.4) mol: (0.13-0.23) mol.

4. The anti-blooming silver-gray topcoat for automotive refinish paint according to claim 1, characterized in that, The temperature during the stirring reaction is 90-100℃, and the reaction time is 2-3 hours.

5. The anti-blooming silver-gray topcoat for automotive refinish paint according to claim 1, characterized in that, The pH is adjusted to 6.5-7 by adding acid solution.

6. The anti-blooming silver-gray topcoat for automotive refinish paint according to claim 5, characterized in that, The acid solution is an aqueous solution of oxalic acid or an aqueous solution of citric acid.

7. The anti-blooming silver-gray topcoat for automotive refinish paint according to claim 2, characterized in that, The preparation method of 4-(maleic acid monoester methyl)cyclohexanone is as follows: add dichloromethane, 4-hydroxymethylcyclohexanone, maleic anhydride, and 4-dimethylaminopyridine to a reaction flask, stir the reaction at 20-35℃ for 4-6 h, distill under reduced pressure, and separate the crude product by silica gel column chromatography to obtain 4-(maleic acid monoester methyl)cyclohexanone.

8. The anti-blooming silver-gray topcoat for automotive refinish paint according to claim 7, characterized in that, The ratio of 4-hydroxymethylcyclohexanone, maleic anhydride, and 4-dimethylaminopyridine is 1 mol: (1.2-1.4) mol: (0.3-0.4) mol.

9. A method for preparing an anti-blooming silver-gray topcoat for automotive refinish paint as described in any one of claims 1-8, characterized in that, The preparation method includes: adding maleic acid monoester aldehyde ketone resin and aluminum silver paste to a high-speed disperser, shearing and dispersing, then adding unsaturated polyester resin, diluent, oxygen barrier, defoamer, and leveling agent, shearing and dispersing, and finally adding curing agent and curing accelerator to obtain an anti-blooming silver-gray topcoat for automotive repair paint.

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