A high-temperature resistant and anti-corrosion coating and its preparation method

Abstract

The present invention relates to the technical field of coatings, and discloses a temperature-resistant and corrosion-resistant coating and a preparation method thereof. The temperature-resistant and corrosion-resistant coating of the present invention includes 100 parts by weight of polyester polyol, 14.6 - 19.3 parts by weight of diisocyanate monomer, 18 - 19 parts by weight of diphenolic acid chain extender, 1.9 - 3.5 parts by weight of small molecule chain extender, 20 - 28 parts by weight of filler, etc.; the obtained waterborne polyurethane coating has good water dispersibility and good storage stability. The diphenolic acid chain extender contains a hydrophobic and heat-resistant phenyl indolocarbazole heterocycle, which is beneficial to reducing the water absorption rate of the waterborne polyurethane coating, improving the water resistance of the coating, and improving the salt spray corrosion resistance. At the same time, the coating film shows good high-temperature resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of coatings, and specifically to a temperature-resistant and anti-corrosion coating and a preparation method thereof. Background Art

[0002] Compared with solvent-based coatings, waterborne coatings are more environmentally friendly, dry quickly, and are easy to use. Among them, waterborne polyurethane has good mechanical strength, toughness, and wear resistance, and is widely used. Traditional waterborne polyurethane has a relatively large water absorption rate, which is not conducive to improving the water resistance and salt spray anti-corrosion performance of the paint film.

[0003] Polyurethane is usually prepared from raw materials such as polyols, isocyanate monomers, chain extenders, etc. Among them, the chain extender has a great influence on the hydrophilicity, temperature resistance and other properties of polyurethane. Common chain extenders include 2,2-dimethylolpropionic acid, ethylene glycol, 1,4-butanediol, hydroquinone, biphenol, ethylenediamine, etc. For example, the literature "Effect of Rosin Acid Modified Epoxy Soybean Oil on the Properties of Waterborne Polyurethane" in the 4th issue of the 41st volume of the Journal of Shaanxi University of Science & Technology discloses the reaction of rosin acid and epoxy soybean oil to prepare a bio-based polyol containing a hydrogenated triphenylene ring structure, and introducing the hydrogenated triphenylene ring structure into waterborne polyurethane to improve the hydrophobicity, thermal stability and other properties of polyurethane. However, this literature requires the additional addition of dimethylolpropionic acid as a waterborne chain extender to obtain waterborne polyurethane. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the present invention solves the problems of poor temperature resistance, waterproofing and anti-corrosion performance of polyurethane coatings.

[0005] The present invention provides a temperature-resistant and anti-corrosion coating, which includes 100 parts by weight of polyester polyol, 14.6 - 19.3 parts by weight of diisocyanate monomer, 0.08 - 0.11 parts by weight of dibutyltin dilaurate, 18 - 19 parts by weight of diphenolic carboxylic acid chain extender, 1.9 - 3.5 parts by weight of small molecule chain extender, 20 - 28 parts by weight of filler, 1.5 - 2.4 parts by weight of dispersant, 0.6 - 1.1 parts by weight of defoamer and 0.5 - 0.8 parts by weight of leveling agent.

[0006] The preparation method of the temperature-resistant and anti-corrosion coating is as follows: drying and dehydrating the polyester polyol, reacting with the diisocyanate monomer and dibutyltin dilaurate in a nitrogen atmosphere at 70 - 80°C for 2 - 3 h, adding acetone and diphenolic carboxylic acid chain extender, reducing the temperature to 40 - 45°C, reacting for 40 - 60 min, adding triethylamine for neutralization, then adding the small molecule chain extender, reacting for 30 - 40 min, finally adding water, stirring and then distilling off acetone under reduced pressure, adding the filler, dispersant, defoamer and leveling agent, and stirring and mixing evenly to obtain the temperature-resistant and anti-corrosion coating.

[0007] Preferably, the preparation method of the diphenolic acid chain extender is as follows: Add 100 parts by weight of 6,12-diphenolic-5,11-dihydroindolo[3,2-b]carbazole and 0.5-0.6 parts by weight of the catalyst benzyltriethylammonium chloride to dimethyl sulfoxide. Add an aqueous solution containing 80-130 parts by weight of sodium hydroxide and 70-78 parts by weight of bromoacetic acid under a nitrogen atmosphere, and react at 20-30 °C for 5-8 h. Add water for dilution, and adjust the pH of the solution to 3-4 by dropping concentrated hydrochloric acid. Precipitate is separated out, and then filtered by suction. The product is recrystallized in a mixed solution of N,N-dimethylformamide and chloroform to obtain the diphenolic acid chain extender. The reaction formula is:

[0008] .

[0009] Preferably, the diisocyanate monomer is isophorone diisocyanate, toluene-2,4-diisocyanate or hexamethylene diisocyanate.

[0010] Preferably, the small molecule chain extender is ethylene glycol, diethylene glycol or 1,4-butanediol.

[0011] Preferably, the filler is mica powder or titanium dioxide.

[0012] The beneficial technical effects of the present invention: The present invention uses the diphenolic acid chain extender containing a carboxyl group as the waterborne chain extender of polyurethane, and mica powder, etc. as the filler. The obtained waterborne polyurethane coating has good water dispersibility, the coating does not delaminate, and the storage stability is good.

[0013] The diphenolic acid chain extender of the present invention contains a hydrophobic phenyl indolocarbazole heterocycle, which is beneficial to reducing the water absorption rate of the waterborne polyurethane coating, improving the water resistance performance, and improving the salt spray corrosion resistance performance of the coating.

[0014] The phenyl indolocarbazole fused ring structure contained in the diphenolic acid chain extender of the present invention has strong heat resistance and is not easily thermally decomposed, which is beneficial to increasing the thermal decomposition temperature of polyurethane. And the fused ring undergoes isomerization crosslinking to form carbon at high temperature, which is beneficial to improving the high temperature carbon formation property and the high temperature mass residue rate, thereby improving the high temperature resistance performance of the paint film. Specific embodiments

[0015] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0016] The following polyester polyol with an average molecular weight of 3000 is purchased from Jining Tangyi Chemical Co., Ltd.

[0017] Add 0.234 g (2 mmol) of indole, 0.244 g (2 mmol) of p-hydroxybenzaldehyde, and 0.0228 g of the catalyst N,2-dibromo-6-chloro-3,4-dihydro-2H-benzo[e][1,2,4]thiadiazine-7-sulfonamide-1,1-dioxide (DCDBTSD, CAS No. 1625664-18-7, structural formula is ) to 2 mL of acetonitrile, react at 50 °C for 20 min, filter and dry. The product is recrystallized from a mixed solution of N,N-dimethylformamide and chloroform to obtain 6,12-diphenolyl-5,11-dihydroindolo[3,2-b]carbazole. The structural formula is .

[0018] Example 1

[0019] (1) Add 5 g of 6,12-diphenolyl-5,11-dihydroindolo[3,2-b]carbazole and 30 mg of benzyltriethylammonium chloride to 160 mL of dimethyl sulfoxide. Under a nitrogen atmosphere, add 15 mL of an aqueous solution containing 6.5 g of sodium hydroxide and 3.5 g of bromoacetic acid, react at 20 °C for 8 h, add 800 mL of water for dilution, adjust the pH of the solution to 4 by dropping concentrated hydrochloric acid, precipitate a solid, filter by suction. The product is recrystallized from a mixed solution of N,N-dimethylformamide and chloroform to obtain a diphenolyl carboxylic acid chain extender.

[0020] (2) Dry and remove water from 100 g of polyester polyol, react with 19.3 g of isophorone diisocyanate and 0.11 g of dibutyltin dilaurate under a nitrogen atmosphere at 70 °C for 3 h. Add 30 mL of acetone and 18.3 g (32.91 mmol) of the diphenolyl carboxylic acid chain extender, lower the temperature to 40 °C, react for 60 min, add 6.7 g of triethylamine for neutralization, then add 3 g of 1,4-butanediol, react for 30 min. Finally, add 180 mL of water, stir and distill off acetone under reduced pressure. Add 26 g of filler mica flakes, 2 g of dispersant BASF Disponil A 1080, 1.1 g of defoamer TEGO-825, and 0.6 g of leveling agent TEGO-2300, stir and mix evenly to obtain a high-temperature resistant and corrosion-resistant coating.

[0021] Example 2

[0022] (1) Add 5 g of 6,12-diphenolyl-5,11-dihydroindolo[3,2-b]carbazole and 25 mg of benzyltriethylammonium chloride to 160 mL of dimethyl sulfoxide. Under a nitrogen atmosphere, add 10 mL of an aqueous solution containing 4 g of sodium hydroxide and 3.9 g of bromoacetic acid, react at 30 °C for 5 h, add 800 mL of water for dilution, adjust the pH of the solution to 3 by dropping concentrated hydrochloric acid, precipitate a solid, filter by suction. The product is recrystallized from a mixed solution of N,N-dimethylformamide and chloroform to obtain a diphenolyl carboxylic acid chain extender.

[0023] (2) 100 g of polyester polyol was dried to remove water, and reacted with 15.1 g of toluene-2,4-diisocyanate and 0.08 g of dibutyltin dilaurate in a nitrogen atmosphere at 70 °C for 3 h. Then, 30 mL of acetone and 18 g of diphenolic carboxylic acid chain extender were added. The temperature was lowered to 45 °C and the reaction was carried out for 40 min. 6.5 g of triethylamine was added for neutralization, and then 3.5 g of diethylene glycol was added and the reaction was carried out for 40 min. Finally, 190 mL of water was added. After stirring, acetone was removed by distillation under reduced pressure. 28 g of filler mica flakes, 2.4 g of dispersant BASF Disponil A1080, 0.6 g of defoamer TEGO-825, and 0.8 g of leveling agent TEGO-2300 were added and stirred evenly to obtain a temperature-resistant and corrosion-resistant coating.

[0024] Example 3

[0025] (1) 100 g of polyester polyol was dried to remove water, and reacted with 14.6 g of hexamethylene diisocyanate and 0.11 g of dibutyltin dilaurate in a nitrogen atmosphere at 80 °C for 2 h. Then, 35 mL of acetone and 19 g of diphenolic carboxylic acid chain extender (prepared in the same way as in Example 1) were added. The temperature was lowered to 45 °C and the reaction was carried out for 40 min. 6.9 g of triethylamine was added for neutralization, and then 1.9 g of ethylene glycol was added and the reaction was carried out for 30 min. Finally, 180 mL of water was added. After stirring, acetone was removed by distillation under reduced pressure. 20 g of filler titanium dioxide, 1.5 g of dispersant BASF Disponil A 1080, 0.8 g of defoamer TEGO-825, and 0.8 g of leveling agent TEGO-2300 were added and stirred evenly to obtain a temperature-resistant and corrosion-resistant coating.

[0026] Example 4

[0027] (1) 100 g of polyester polyol was dried to remove water, and reacted with 15.1 g of toluene-2,4-diisocyanate and 0.09 g of dibutyltin dilaurate in a nitrogen atmosphere at 75 °C for 3 h. Then, 30 mL of acetone and 18.8 g of diphenolic carboxylic acid chain extender (prepared in the same way as in Example 1) were added. The temperature was lowered to 45 °C and the reaction was carried out for 40 min. 6.8 g of triethylamine was added for neutralization, and then 3.5 g of 1,4-butanediol was added and the reaction was carried out for 40 min. Finally, 180 mL of water was added. After stirring, acetone was removed by distillation under reduced pressure. 28 g of filler mica powder, 1.5 g of dispersant BASF Disponil A 1080, 0.6 g of defoamer TEGO-825, and 0.5 g of leveling agent TEGO-2300 were added and stirred evenly to obtain a temperature-resistant and corrosion-resistant coating.

[0028] Comparative Example 1

[0029] (1) 100 g of polyester polyol was dried to remove water, and reacted with 19.3 g of isophorone diisocyanate and 0.11 g of dibutyltin dilaurate in a nitrogen atmosphere at 70 °C for 3 h. Then, 30 mL of acetone and 4.41 g (32.91 mmol) of 2,2-dimethylolpropionic acid were added. The temperature was lowered to 40 °C and reacted for 60 min. 6.7 g of triethylamine was added for neutralization, then 3 g of 1,4-butanediol was added and reacted for 30 min. Finally, 180 mL of water was added. After stirring, acetone was removed by distillation under reduced pressure. 26 g of filler mica flakes, 2 g of dispersant BASF Disponil A 1080, 1.1 g of defoamer TEGO-825, and 0.6 g of leveling agent TEGO-2300 were added and stirred evenly to obtain a temperature-resistant and corrosion-resistant coating.

[0030] Comparative Example 2

[0031] (1) 100 g of polyester polyol was dried to remove water, and reacted with 19.3 g of isophorone diisocyanate and 0.11 g of dibutyltin dilaurate in a nitrogen atmosphere at 70 °C for 3 h. Then, 30 mL of acetone and 14.48 g (32.91 mmol) of 6,12-diphenolic-5,11-dihydroindolo[3,2-b]carbazole were added. The temperature was lowered to 40 °C and reacted for 60 min. 6.7 g of triethylamine was added for neutralization, then 3 g of 1,4-butanediol was added and reacted for 30 min. Finally, 180 mL of water was added. After stirring, acetone was removed by distillation under reduced pressure. 26 g of filler mica flakes, 2 g of dispersant BASF Disponil A 1080, 1.1 g of defoamer TEGO-825, and 0.6 g of leveling agent TEGO-2300 were added and stirred evenly to obtain a temperature-resistant and corrosion-resistant coating.

[0032] Comparative Example 3

[0033] (1) 100 g of polyester polyol was dried to remove water, and reacted with 19.3 g of isophorone diisocyanate and 0.11 g of dibutyltin dilaurate in a nitrogen atmosphere at 70 °C for 3 h. Then, 30 mL of acetone and 9.03 g (32.91 mmol) of 2,5-dihydroxyterephthalic acid (structural formula is , CAS No. is 13987-45-6) was added. The temperature was lowered to 40 °C and reacted for 60 min. 6.7 g of triethylamine was added for neutralization, then 3 g of 1,4-butanediol was added and reacted for 30 min. Finally, 180 mL of water was added. After stirring, acetone was removed by distillation under reduced pressure. 26 g of filler mica flakes, 2 g of dispersant BASF Disponil A1080, 1.1 g of defoamer TEGO-825, and 0.6 g of leveling agent TEGO-2300 were added and stirred evenly to obtain a temperature-resistant and corrosion-resistant coating.

[0034] The coating was placed at room temperature for 30 days to observe the dispersion of the coating.

[0035] Pour the coating onto the surface of the tinplate and dry it at 80 °C for 8 h to form a paint film. Test the salt spray resistance of the paint film according to the method of GB / T 1771-2007.

[0036] Cure the coating into a gel film, dry it, weigh it, then soak it in water for 24 h. After taking it out, wipe the residual water on the surface and weigh it to calculate the water absorption rate W. W = (m - m0) / m0 × 100%. m is the mass after water absorption, and m0 is the mass before water absorption.

[0037] Weigh 8 mg of the gel film and place it in a thermogravimetric analyzer. Perform thermal performance analysis in a nitrogen atmosphere with a heating rate of 10 °C / min, rising from 30 °C to 700 °C.

[0038] Table 1 Coating Performance Test

[0039] Coating dispersibility Salt spray resistance (960h) Water absorption rate (%) Initial thermal decomposition temperature (°C) Mass residue rate (%) Example 1 No delamination No bubbling, no peeling, no rusting 6.72 289.1 22.3 Example 2 No delamination No bubbling, no peeling, no rusting 6.34 291.0 23.5 Example 3 No delamination No bubbling, no peeling, no rusting 7.04 287.5 21.8 Example 4 No delamination No bubbling, no peeling, no rusting 6.49 290.7 23.9 Comparative Example 1 No delamination Bubbling, no peeling, no rusting 17.36 274.8 16.7 Comparative Example 2 Obvious delamination No bubbling, no peeling, no rusting 4.69 289.6 22.5 Comparative Example 3 No delamination Bubbling, no peeling, no rusting 9.18 282.7 19.0

[0040] After testing, in Examples 1-4, a carboxyl-containing diphenolic carboxylic acid chain extender was used as the aqueous chain extender for polyurethane, and the obtained polyurethane coating had good water dispersibility, the coating did not delaminate, and the storage stability was good. And the diphenolic carboxylic acid chain extender contains a hydrophobic phenyl indolocarbazole heterocycle, which is beneficial to reducing the water absorption rate of the aqueous polyurethane coating, improving the water resistance, and improving the salt spray corrosion resistance of the coating. At the same time, the phenyl indolocarbazole fused ring structure has strong heat resistance and is not easily thermally decomposed, which is beneficial to increasing the thermal decomposition temperature of polyurethane, and the fused ring undergoes isomerization cross-linking to form carbon at high temperature, which is beneficial to improving the high-temperature carbon formation property and the high-temperature mass residue rate, thereby improving the high-temperature resistance of the paint film.

[0041] In Comparative Example 1, ordinary 2,2-dimethylolpropionic acid was used as the aqueous chain extender, and the obtained polyurethane coating had good water dispersibility, the coating did not delaminate, and the storage stability was good, but the water absorption rate was relatively large, which was not conducive to improving the water resistance and salt spray resistance of the paint film. At the same time, the polyurethane did not contain a heat-resistant fused ring structure, resulting in a lower thermal decomposition temperature and mass residue rate, and the high-temperature resistance of the paint film was poor.

[0042] In Comparative Example 2, 6,12-diphenolic-5,11-dihydroindolo[3,2-b]carbazole was used as the chain extender, which does not contain a carboxyl group. The obtained polyurethane had poor hydrophilicity and water dispersibility, and it was impossible to obtain an aqueous coating with excellent storage stability. However, the water absorption rate was low, the salt spray resistance was excellent, and at the same time, the thermal decomposition temperature and mass residue rate were high, and the high-temperature resistance of the paint film was good.

[0043] Comparative Example 3 used 2,5-dihydroxyterephthalic acid as the aqueous chain extender, which does not contain the hydrophobic and heat-resistant phenyl indolocarbazole fused ring structure, resulting in a relatively large water absorption rate of the paint film, which is not conducive to improving the water resistance and salt spray corrosion resistance of the paint film, and the thermal decomposition temperature and mass residue rate are relatively low, and the high temperature resistance is not good.

[0044] The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and variations based on the concept of the present invention without creative work. Therefore, all technical solutions that can be obtained by those skilled in the art in the technical field of the present invention based on the concept of the present invention through logical analysis, reasoning or limited experiments on the basis of the prior art should be within the protection scope determined by the claims.

Claims

1. A heat-resistant and anti-corrosion coating, characterized in that: The heat-resistant anticorrosive coating comprises 100 parts by weight of polyester polyol, 14.6-19.3 parts by weight of diisocyanate monomer, 0.08-0.11 parts by weight of dibutyltin dilaurate, 18-19 parts by weight of diphenolic carboxylic acid chain extender, 1.9-3.5 parts by weight of small molecule chain extender, 20-28 parts by weight of filler, 1.5-2.4 parts by weight of dispersant, 0.6-1.1 parts by weight of defoamer and 0.5-0.8 parts by weight of leveling agent; The preparation method of the diphenol-based carboxylic acid chain extender comprises the following steps: adding 6,12-diphenol-5,11-dihydroindole[3,2-b]carbazole and benzyltriethylammonium chloride to dimethyl sulfoxide, adding sodium hydroxide aqueous solution and bromoacetic acid in a nitrogen atmosphere, adding water to dilute the solution after the reaction, dropping concentrated hydrochloric acid to adjust the pH value of the solution, precipitating a precipitate, filtering the precipitate, and recrystallizing the product in a mixed solution of N,N-dimethylformamide and chloroform to obtain the diphenol-based carboxylic acid chain extender.

2. The heat-resistant anticorrosive coating according to claim 1, characterized in that: The diisocyanate monomer is isophorone diisocyanate, toluene-2,4-diisocyanate or hexamethylene diisocyanate.

3. The heat-resistant anticorrosive coating according to claim 1, characterized in that: The small molecule chain extender is ethylene glycol, diethylene glycol or 1,4-butanediol.

4. The heat-resistant anticorrosive coating according to claim 1, characterized in that: The filler is mica powder or titanium dioxide.

5. The heat-resistant anticorrosive coating according to claim 1, characterized in that: The dosage of the 6,12-diphenol-5,11-dihydroindole[3,2-b]carbazole is 100 parts by weight, the dosage of benzyltriethylammonium chloride is 0.5-0.6 parts by weight, the dosage of sodium hydroxide is 80-130 parts by weight, and the dosage of bromoacetic acid is 70-78 parts by weight.

6. The heat-resistant anticorrosive coating according to claim 1, characterized in that: The reaction temperature is 20-30°C and the reaction time is 5-8h.

7. The heat-resistant anticorrosive coating according to claim 1, characterized in that: The solution pH is adjusted to 3-4 by adding concentrated hydrochloric acid.

8. A method for preparing a heat-resistant and anticorrosive coating according to any one of claims 1 to 7, characterized in that: The preparation method comprises the following steps: drying and removing water from the polyester polyol, reacting the polyester polyol with a diisocyanate monomer and dibutyltin dilaurate in a nitrogen atmosphere at 70-80° C. for 2-3 hours, adding acetone and a diphenolic carboxylic acid chain extender, lowering the temperature to 40-45° C., reacting for 40-60 minutes, adding triethylamine for neutralization, then adding a small molecule chain extender, reacting for 30-40 minutes, finally adding water, stirring and removing acetone by vacuum distillation, adding a filler, a dispersant, a defoamer, and a leveling agent, stirring and mixing, and obtaining a heat-resistant and anticorrosive coating.