Wear-resistant thin-layer water-based paint and preparation method thereof

Abstract

The invention relates to the technical field of coatings, and discloses a wear-resistant thin-layer water-based coating and a preparation method thereof.The water-based coating is prepared from, by weight, 100 parts of waterborne polyurethane, 5-25 parts of sodium sulfonate modified cellulose, 0.6-1 part of a defoaming agent, 3-5 parts of a coalescing agent, 5-8 parts of pigment filler and 1.4-2.3 parts of a dispersing agent. The modified cellulose contains a sodium sulfonate hydrophilic group, the water solubility of the cellulose is improved, the cellulose is better in dispersity in the water-based paint and free of precipitation, the storage stability of the paint is excellent, and microcrystalline cellulose is uniformly dispersed in the water-based paint and has a good enhancement effect on a polyurethane paint film; meanwhile, cellulose contains a rigid phenyl maleimide ring, so that the structural stability is high, the strength is high, and the impact resistance, the hardness and the wear resistance of a paint film are favorably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of coatings, and specifically to a wear-resistant thin-layer waterborne coating and a preparation method thereof. Background Art

[0002] Waterborne polyurethane coatings do not contain volatile organic solvents, have a very low VOC content, are green and environmentally friendly, and have good film-forming properties, a thin film thickness, and excellent properties such as solvent resistance, corrosion resistance, and toughness. They are widely used in fields including construction, furniture, transportation, electronics, etc. Improving the wear resistance, mechanical strength and other properties of waterborne polyurethane coatings is the research focus.

[0003] Cellulose is cheap and easily available, biodegradable, and has high strength and good mechanical properties. It is widely used in materials such as coatings, inks, plastics, and textiles. The functional modification of cellulose is a research hotspot. For example, by reacting mercaptoacetic acid with the hydroxyl groups of cellulose in a catalytic system of concentrated sulfuric acid and acetic anhydride, cellulose containing mercapto groups can be obtained, which has a wide range of applications. Chinese Patent with Publication No. CN111019507B discloses a high-strength waterborne polyurethane / cellulose nanocomposite emulsion and a preparation method thereof. The carboxylated cellulose is activated by EDC and NHS, and then a waterborne polyurethane / cellulose nanocomposite emulsion and its film material are prepared using oligomeric polyols as the soft segment and isocyanate compounds as the hard segment, which have excellent mechanical properties. Compared with this patent, the present invention uses sodium sulfonate-modified cellulose to improve the wear resistance and other properties of waterborne polyurethane coatings. Summary of the Invention

[0004] (1) Technical problems to be solved: The present invention provides a wear-resistant thin-layer waterborne coating, which solves the problems of poor wear resistance, strength and other properties of polyurethane coatings.

[0005] (2) Technical solution: A wear-resistant thin-layer waterborne coating includes 100 parts by weight of waterborne polyurethane, 5 - 25 parts by weight of sodium sulfonate-modified cellulose, 0.6 - 1 part by weight of defoamer, 3 - 5 parts by weight of film-forming aid, 5 - 8 parts by weight of pigment filler, and 1.4 - 2.3 parts by weight of dispersant.

[0006] Preferably, the preparation method of the wear-resistant thin-layer waterborne coating is: adding waterborne polyurethane, sodium sulfonate-modified cellulose, defoamer, film-forming aid, pigment filler, and dispersant into water, and shearing and dispersing in a high-speed shear machine to obtain the wear-resistant thin-layer waterborne coating.

[0007] Preferably, the film-forming aid is alcohol ester 12, and the pigment filler is titanium dioxide or talc powder.

[0008] Preferably, the preparation method of the sodium sulfonate-modified cellulose is:

[0009] (1) Add 100 parts by weight of mercapto cellulose to N,N-dimethylformamide. After stirring, add 4-7 parts by weight of N-phenyl maleimide and 5-8.5 parts by weight of triethylamine, and stir and react at 50-75 °C for 7-12 h. Add ethanol to the solution, filter by suction, wash with ethanol, and dry to obtain a modified cellulose precursor.

[0010] (2) Add the modified cellulose precursor to concentrated sulfuric acid, stir and react at 80-90 °C for 2-3 h. After filtering by suction, add the product to a sodium hydroxide solution with a mass fraction of 30-40%, stir for 30-60 min, then filter by suction, wash with ethanol, and dry to obtain sodium sulfonate modified cellulose. The preparation reaction formula is:

[0011]

[0012] Preferably, the preparation method of mercapto cellulose is: add 350-500 parts by weight of acetic anhydride, 1.4-2.2 parts by weight of concentrated sulfuric acid, 600-900 parts by weight of mercaptoacetic acid, and 100 parts by weight of microcrystalline cellulose to 220-320 parts by weight of glacial acetic acid, react at 35-45 °C for 72-96 h, filter by suction, wash with water, and dry to obtain mercapto cellulose. The preparation reaction formula is:

[0013]

[0014] (3) Technical effects: In the present invention, mercapto cellulose reacts with N-phenyl maleimide by an addition reaction, and then is sulfonated with concentrated sulfuric acid to obtain sodium sulfonate modified cellulose. Finally, it is compounded with waterborne polyurethane, defoamer, pigments and fillers, etc. to obtain a polyurethane waterborne coating. The modified cellulose contains sodium sulfonate hydrophilic groups, which improves the water solubility of cellulose, has better dispersion in waterborne coatings, no precipitation, excellent storage stability of the coating, and microcrystalline cellulose is uniformly dispersed in the waterborne coating, which has a good reinforcing effect on the polyurethane paint film. At the same time, the cellulose contains a rigid phenyl maleimide ring, with high structural stability and large strength, which is beneficial to improving the impact resistance, hardness and wear resistance of the paint film. Specific embodiments

[0015] The following describes the present application in detail in combination with the embodiments. However, these embodiments do not limit the present application, and any structural, method, or functional transformation made by those of ordinary skill in the art based on these embodiments is included in the protection scope of the present application.

[0016] The following aqueous polyurethane, grade PU850, is from Green Source Baisui Chemical Technology (Beijing) Co., Ltd. The defoamer, model T-4201, is from Nanjing Baiju Technology Co., Ltd. The dispersant, model ECO-2300, is from Dongguan Wanying New Materials Co., Ltd. The microcrystalline cellulose, product number NO528ACE, is from Shenzhen Lefu Biotechnology Co., Ltd. Concentrated sulfuric acid, 98 wt%.

[0017] Example 1:

[0018] (1) Add 88 g of acetic anhydride, 150 g of mercaptoacetic acid, 0.37 g of concentrated sulfuric acid, and 20 g of microcrystalline cellulose to 56 g of glacial acetic acid, stir and react at 35 °C for 96 h, filter by suction, wash with water, and dry to obtain mercapto cellulose.

[0019] (2) Add 10 g of mercapto cellulose to 100 mL of N,N-dimethylformamide, stir, add 0.58 g of N-phenylmaleimide and 0.7 g of triethylamine, stir and react at 60 °C for 12 h, add ethanol to the solution, filter by suction, wash with ethanol, and dry to obtain a modified cellulose precursor.

[0020] (3) Add 20 g of the modified cellulose precursor to 70 mL of concentrated sulfuric acid with a mass fraction of 98%, stir and react at 80 °C for 3 h, filter by suction, add the product to 150 mL of a sodium hydroxide solution with a mass fraction of 30%, stir for 60 min, filter by suction, wash with ethanol, and dry to obtain sodium sulfonate-modified cellulose.

[0021] (4) The preparation method of the wear-resistant thin-layer waterborne coating is as follows: Add 100 g of aqueous polyurethane, 5 g of sodium sulfonate-modified cellulose, 1 g of defoamer, 5 g of film-forming auxiliary alcohol ester 12, 5 g of pigment filler talc powder, and 1.4 g of dispersant to 120 mL of water, and shear and disperse in a high-speed shear machine to obtain a wear-resistant thin-layer waterborne coating.

[0022] Example 2:

[0023] (1) Add 70 g of acetic anhydride, 120 g of mercaptoacetic acid, 0.28 g of concentrated sulfuric acid with a mass fraction of 98%, and 20 g of microcrystalline cellulose to 44 g of glacial acetic acid, stir and react at 45 °C for 72 h, filter by suction, wash with water, and dry to obtain mercapto cellulose.

[0024] (2) Add 10 g of mercapto cellulose to 100 mL of N,N-dimethylformamide, stir, add 0.4 g of N-phenylmaleimide and 0.5 g of triethylamine, stir and react at 50 °C for 8 h, add ethanol to the solution, filter by suction, wash with ethanol, and dry to obtain a modified cellulose precursor.

[0025] (3) Add 20 g of the modified cellulose precursor to 80 mL of concentrated sulfuric acid with a mass fraction of 98%, stir and react at 80 °C for 3 h. After filtration, add the product to 120 mL of sodium hydroxide solution with a mass fraction of 40%, stir for 30 min and then filter. Wash with ethanol and dry to obtain sodium sulfonate modified cellulose.

[0026] (4) The preparation method of the wear-resistant thin-layer waterborne coating is as follows: Add 100 g of waterborne polyurethane, 15 g of sodium sulfonate modified cellulose, 0.6 g of defoamer, 3 g of film-forming auxiliary alcohol ester 12, 8 g of pigment filler titanium dioxide, and 2.3 g of dispersant to 130 mL of water, and shear and disperse in a high-speed shear machine to obtain the wear-resistant thin-layer waterborne coating.

[0027] Example 3:

[0028] (1) Add 100 g of acetic anhydride, 180 g of mercaptoacetic acid, 0.44 g of concentrated sulfuric acid with a mass fraction of 98%, and 20 g of microcrystalline cellulose to 64 g of glacial acetic acid, stir and react at 40 °C for 96 h. After filtration, wash with water and dry to obtain mercapto cellulose.

[0029] (2) Add 10 g of mercapto cellulose to 110 mL of N,N-dimethylformamide, stir and then add 0.7 g of N-phenylmaleimide and 0.85 g of triethylamine, stir and react at 75 °C for 7 h. Add ethanol to the solution, filter and wash with ethanol, and dry to obtain the modified cellulose precursor.

[0030] (3) Add 20 g of the modified cellulose precursor to 70 mL of concentrated sulfuric acid, stir and react at 90 °C for 2 h. After filtration, add the product to 150 mL of sodium hydroxide solution with a mass fraction of 30%, stir for 60 min and then filter. Wash with ethanol and dry to obtain sodium sulfonate modified cellulose.

[0031] (4) The preparation method of the wear-resistant thin-layer waterborne coating is as follows: Add 100 g of waterborne polyurethane, 25 g of sodium sulfonate modified cellulose, 1 g of defoamer, 4.3 g of film-forming auxiliary alcohol ester 12, 7 g of pigment filler titanium dioxide, and 2 g of dispersant to 150 mL of water, and shear and disperse in a high-speed shear machine to obtain the wear-resistant thin-layer waterborne coating.

[0032] Comparative Example 1: The difference between this comparative example and Example 1 is that sodium sulfonate modified cellulose is not added.

[0033] (1) The preparation method of the wear-resistant thin-layer waterborne coating is as follows: Add 100 g of waterborne polyurethane, 1 g of defoamer, 5 g of film-forming auxiliary alcohol ester 12, 5 g of pigment filler talc, and 1.4 g of dispersant to 120 mL of water, and shear and disperse in a high-speed shear machine to obtain the thin-layer waterborne coating.

[0034] Comparative Example 2: The difference between this comparative example and Example 1 is that microcrystalline cellulose is used instead of sodium sulfonate modified cellulose.

[0035] (1) The preparation method of the wear-resistant thin-layer waterborne coating is as follows: Add 100 g of waterborne polyurethane, 5 g of microcrystalline cellulose, 1 g of defoamer, 5 g of film-forming auxiliary alcohol ester 12, 5 g of pigment filler talc powder, and 1.4 g of dispersant to 120 mL of water, and shear and disperse in a high-speed shear machine to obtain a thin-layer waterborne coating.

[0036] Comparative Example 3: The difference between this comparative example and Example 1 is that a modified cellulose precursor is used instead of sodium sulfonate modified cellulose.

[0037] (1) The preparation method of the wear-resistant thin-layer waterborne coating is as follows: Add 100 g of waterborne polyurethane, 5 g of modified cellulose precursor, 1 g of defoamer, 5 g of film-forming auxiliary alcohol ester 12, 5 g of pigment filler talc powder, and 1.4 g of dispersant to 120 mL of water, and shear and disperse in a high-speed shear machine to obtain a thin-layer waterborne coating.

[0038] The storage stability is tested according to the national standard GB / T 6753.3-1986.

[0039] The curing temperature of the coating is 90 °C and the time is 8 h. The abrasion resistance of the cured paint film is tested according to the national standard GB / T1768-2006. The impact resistance is tested according to the national standard GB / T 1732-2020. The hardness is tested according to the national standard GB / T 6739-2022. The test results are shown in the following table.

[0040] Table 1 Coating Performance Test

[0041]

[0042] After testing, compared with Comparative Example 1, the polyurethane coatings of Examples 1-3 have lower friction mass loss, better abrasion resistance, and higher impact resistance and pencil hardness, and good mechanical properties. This is mainly because sodium sulfonate modified cellulose is added. The sodium sulfonate hydrophilic group it contains improves the water solubility of cellulose, has better dispersibility in waterborne coatings, no precipitation, and excellent storage stability of the coatings. Microcrystalline cellulose is evenly dispersed in the waterborne coating, has a good strengthening effect on the polyurethane paint film, and the cellulose contains a rigid phenylmaleimide ring, with high structural stability and large strength, which is beneficial to improving the impact resistance, hardness, and wear resistance of the paint film.

[0043] The waterborne coating of Comparative Example 2 added microcrystalline cellulose, which has poor water solubility and is prone to precipitation in waterborne coatings, resulting in poor storage stability of the coatings. Moreover, microcrystalline cellulose does not contain a rigid phenylmaleimide ring and has a poor strengthening effect on the polyurethane paint film, resulting in lower impact resistance, hardness, and wear resistance of the paint film than those of Example 1.

[0044] In Comparative Example 3, the modified cellulose precursor added does not contain a sodium sulfonate hydrophilic group, and its water solubility is poor, so it is likely to precipitate in the waterborne coating. The dispersion of microcrystalline cellulose in the polyurethane paint film is poor, and the reinforcing effect on the polyurethane paint film is low, resulting in the impact resistance, hardness and wear resistance of the paint film being lower than those of Example 1.

[0045] The above description of the present disclosure is provided to enable any ordinary person skilled in the art to implement or use the present disclosure. Various modifications to the present disclosure will be obvious to those of ordinary skill in the art, and the general principles corresponding herein can also be applied to other variations without departing from the protection scope of the present disclosure. Therefore, the present disclosure is not limited to the examples and designs described herein, but is consistent with the broadest scope that conforms to the principles and novel features disclosed herein.

Claims

1. A wear-resistant thin-layer waterborne coating, characterized in that, The waterborne coating comprises 100 parts by weight of waterborne polyurethane, 5 - 25 parts by weight of sodium sulfonate modified cellulose, 0.6 - 1 part by weight of defoamer, 3 - 5 parts by weight of film-forming aid, 5 - 8 parts by weight of pigment extender, and 1.4 - 2.3 parts by weight of dispersant; The preparation method of the sodium sulfonate modified cellulose is as follows: (1) Add mercapto cellulose into N,N-dimethylformamide, stir, then add N-phenyl maleimide and triethylamine. After stirring and reacting, add ethanol to the solution, filter by suction, wash, and dry to obtain a modified cellulose precursor; (2) Add the modified cellulose precursor into concentrated sulfuric acid, stir and react, then filter by suction. Add the product into sodium hydroxide solution, stir, filter by suction, wash, and dry to obtain sodium sulfonate modified cellulose.

2. The wear-resistant thin-layer waterborne coating according to claim 1, wherein The reaction temperature in (1) is 50 - 75 °C, and the reaction time is 7 - 12 h.

3. The wear-resistant thin-layer waterborne coating according to claim 1, wherein In (1), the dosage of mercapto cellulose is 100 parts by weight, N-phenyl maleimide is 4 - 7 parts by weight, and triethylamine is 5 - 8.5 parts by weight.

4. The wear-resistant thin-layer waterborne coating according to claim 1, wherein The reaction temperature in (2) is 80 - 90 °C, and the reaction time is 2 - 3 h.

5. The wear-resistant thin-layer waterborne coating according to claim 1, characterized in that In (2), the mass fraction of the sodium hydroxide solution is 30 - 40%.

6. The wear-resistant thin-layer waterborne coating according to claim 1, characterized in that, The preparation method of the mercapto cellulose is as follows: Add 350 - 500 parts by weight of acetic anhydride, 1.4 - 2.2 parts by weight of concentrated sulfuric acid, 600 - 900 parts by weight of mercaptoacetic acid, and 100 parts by weight of microcrystalline cellulose into 220 - 320 parts by weight of glacial acetic acid, react at 35 - 45 °C for 72 - 96 h, filter by suction, wash with water, and dry to obtain mercapto cellulose.

7. The wear-resistant thin-layer waterborne coating according to claim 1, wherein The film-forming aid is alcohol ester 12, and the pigment extender is titanium dioxide or talc powder.

8. A method for preparing a wear-resistant thin-layer waterborne coating according to any one of claims 1-7, characterized in that, The preparation method is as follows: Add waterborne polyurethane, sodium sulfonate modified cellulose, defoamer, film-forming aid, pigment extender, and dispersant into water, and shear and disperse in a high-speed shear machine to obtain a wear-resistant thin-layer waterborne coating.

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