Temperature-resistant anticorrosive paint and preparation method thereof

Abstract

The invention relates to the technical field of coatings, and discloses a temperature-resistant anticorrosive coating and a preparation method thereof.The temperature-resistant anticorrosive coating is prepared from, by weight, 100 parts of polyester polyol, 14.6-19.3 parts of diisocyanate monomer, 18-19 parts of diphenol carboxylic acid chain extender, 1.9-3.5 parts of micromolecule chain extender, 20-28 parts of filler and the like; the obtained waterborne polyurethane coating has good water dispersibility and good storage stability. The diphenol carboxylic acid chain extender contains hydrophobic and heat-resistant phenylindolocarbazole heterocyclic rings, so that the water absorption rate of the waterborne polyurethane coating is reduced, the water resistance of the coating is improved, the salt spray resistance and corrosion resistance are improved, and meanwhile, a coating film shows good high-temperature resistance.

Description

Technical Field

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

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

[0003] Polyurethane is usually prepared from polyols, isocyanate monomers, chain extenders, etc. as raw materials. Among them, chain extenders have 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, biphenylene glycol, ethylenediamine, etc. For example, the document "The Effect of Rosin Acid Modified Epoxidized Soybean Oil on the Performance of Waterborne Polyurethane" in Volume 41, Issue 4 of the Journal of Shaanxi University of Science and Technology discloses that rosin acid and epoxy soybean oil are reacted to prepare a bio-based polyol containing a hydrogenated triphenanthrene ring structure, and the hydrogenated triphenanthrene ring condensed ring structure is introduced into the waterborne polyurethane, which improves the hydrophobicity, thermal stability and other properties of the polyurethane. However, the document requires the additional addition of dimethylolpropionic acid as a waterborne chain extender to obtain waterborne polyurethane. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention solves the problem that the polyurethane coating has poor performances such as temperature resistance, waterproofness and corrosion resistance.

[0005] The invention provides a heat-resistant anticorrosive coating, comprising 100 parts by weight of polyester polyol, 14.6-19.3 parts by weight of diisocyanate monomers, 0.08-0.11 parts by weight of dibutyltin dilaurate, 18-19 parts by weight of diphenolic carboxylic acid chain extenders, 1.9-3.5 parts by weight of small molecule chain extenders, 20-28 parts by weight of fillers, 1.5-2.4 parts by weight of dispersants, 0.6-1.1 parts by weight of defoamers and 0.5-0.8 parts by weight of leveling agents.

[0006] The preparation method of the heat-resistant anticorrosion coating 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 diphenol-based 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 the heat-resistant anticorrosion coating.

[0007] Preferably, the preparation method of the diphenolic carboxylic acid chain extender is: add 100 parts by weight of 6,12-diphenolic-5,11-dihydroindole[3,2-b]carbazole and 0.5-0.6 parts by weight of 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 in a nitrogen atmosphere, react at 20-30°C for 5-8h, add water to dilute, add concentrated hydrochloric acid dropwise to adjust the pH of the solution to 3-4, precipitate, filter, and recrystallize the product in a mixed solution of N,N-dimethylformamide and chloroform to obtain a diphenolic carboxylic acid chain extender. The reaction formula is: .

[0008] Preferably, the diisocyanate monomer is isophorone diisocyanate, toluene-2,4-diisocyanate or hexamethylene diisocyanate.

[0009] Preferably, the small molecule chain extender is ethylene glycol, diethylene glycol or 1,4-butanediol.

[0010] Preferably, the filler is mica powder or titanium dioxide.

[0011] The beneficial technical effect of the present invention is as follows: the present invention uses a diphenolic carboxylic acid chain extender containing a carboxyl group as a water-based chain extender for polyurethane and mica powder and the like as a filler, and the obtained water-based polyurethane coating has good water dispersibility, no stratification of the coating, and good storage stability.

[0012] The diphenol-based carboxylic acid chain extender of the invention contains a hydrophobic phenylindolecarbazole heterocycle, which is beneficial to reducing the water absorption rate of the waterborne polyurethane coating, improving the water resistance, and improving the salt spray resistance and anticorrosion performance of the coating.

[0013] The phenylindolecarbazole condensed ring structure contained in the diphenolic carboxylic acid chain extender of the present invention has strong heat resistance and is not easy to be thermally decomposed, which is beneficial to increasing the thermal decomposition temperature of polyurethane. In addition, the condensed ring undergoes isomerization and cross-linking to form carbon at high temperature, which is beneficial to improving high-temperature carbonization and high-temperature mass residual rate, thereby improving the high-temperature resistance of the paint film. DETAILED DESCRIPTION

[0014] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0015] The following polyester polyols, with an average molecular weight of 3000, were purchased from Jining Tangyi Chemical Co., Ltd.

[0016] To 2 mL of acetonitrile, 0.234 g (2 mmol) of indole, 0.244 g (2 mmol) of p-hydroxybenzaldehyde, and 0.0228 g of 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 ), react at 50°C for 20 minutes, filter and dry, and the product is recrystallized in a mixed solution of N,N-dimethylformamide and chloroform to obtain 6,12-diphenol-5,11-dihydroindole[3,2-b]carbazole. The structural formula is .

[0017] Example 1 (1) Add 5 g of 6,12-diphenol-5,11-dihydroindole[3,2-b]carbazole and 30 mg of benzyltriethylammonium chloride to 160 mL of dimethyl sulfoxide, add 15 mL of an aqueous solution containing 6.5 g of sodium hydroxide and 3.5 g of bromoacetic acid in a nitrogen atmosphere, react at 20°C for 8 h, add 800 mL of water to dilute, add concentrated hydrochloric acid dropwise to adjust the pH of the solution to 4, precipitate, filter, and recrystallize the product in a mixed solution of N,N-dimethylformamide and chloroform to obtain a diphenol-based carboxylic acid chain extender.

[0018] (2) 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. 30 mL of acetone and 18.3 g (32.91 mmol) of diphenol carboxylic acid chain extender were added, the temperature was lowered to 40 ° C, and the reaction was carried out for 60 min. 6.7 g of triethylamine was added for neutralization, and then 3 g of 1,4-butanediol was added and the reaction was carried out for 30 min. Finally, 180 mL of water was added, and the acetone was removed by vacuum distillation after stirring. 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 to obtain a heat-resistant and anti-corrosion coating.

[0019] Example 2 (1) Add 5 g of 6,12-diphenol-5,11-dihydroindole[3,2-b]carbazole and 25 mg of benzyltriethylammonium chloride to 160 mL of dimethyl sulfoxide, add 10 mL of an aqueous solution containing 4 g of sodium hydroxide and 3.9 g of bromoacetic acid in a nitrogen atmosphere, react at 30°C for 5 h, add 800 mL of water to dilute, add concentrated hydrochloric acid dropwise to adjust the pH of the solution to 3, precipitate, filter, and recrystallize the product in a mixed solution of N,N-dimethylformamide and chloroform to obtain a diphenol-based carboxylic acid chain extender.

[0020] (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. 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, and the acetone was removed by vacuum distillation after stirring. 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 to obtain a heat-resistant and anti-corrosion coating.

[0021] Example 3 (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. 35 mL of acetone and 19 g of a diphenolic carboxylic acid chain extender (prepared in the same manner 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 for reaction for 30 min. Finally, 180 mL of water was added. After stirring, the acetone was removed by vacuum distillation. 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 the mixture was stirred to obtain a heat-resistant and anticorrosive coating.

[0022] Example 4 (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. 30 mL of acetone and 18.8 g of a diphenolic carboxylic acid chain extender (prepared in the same manner as in Example 1) were added. The temperature was lowered to 45° C. and reacted for 40 min. 6.8 g of triethylamine was added for neutralization. Then 3.5 g of 1,4-butanediol was added and reacted for 40 min. Finally, 180 mL of water was added. After stirring, the 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 to obtain a heat-resistant and anticorrosive coating.

[0023] Comparative Example 1 (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. 30 mL of acetone and 4.41 g (32.91 mmol) of 2,2-dihydroxymethylpropionic acid were added, the temperature was lowered to 40°C, and the reaction was carried out for 60 min. 6.7 g of triethylamine was added for neutralization, and then 3 g of 1,4-butanediol was added and the reaction was carried out for 30 min. Finally, 180 mL of water was added, and the acetone was removed by vacuum distillation after stirring. 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 to obtain a heat-resistant and anti-corrosion coating.

[0024] Comparative Example 2 (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. 30 mL of acetone and 14.48 g (32.91 mmol) of 6,12-diphenyl-5,11-dihydroindole[3,2-b]carbazole were added, the temperature was lowered to 40°C, and the reaction was carried out for 60 min. 6.7 g of triethylamine was added for neutralization, and then 3 g of 1,4-butanediol was added and the reaction was carried out for 30 min. Finally, 180 mL of water was added, and the acetone was removed by vacuum distillation after stirring. 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 to obtain a heat-resistant and anti-corrosion coating.

[0025] Comparative Example 3 (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 at 70 °C in a nitrogen atmosphere for 3 h. 30 mL of acetone and 9.03 g (32.91 mmol) of 2,5-dihydroxyphenylenedicarboxylic acid (structural formula: , CAS No. 13987-45-6), the temperature was reduced to 40°C, the reaction was carried out for 60 minutes, 6.7g of triethylamine was added for neutralization, and then 3g of 1,4-butanediol was added for reaction for 30 minutes, and finally 180mL of water was added. After stirring, the acetone was removed by vacuum distillation, 26g of filler mica flakes, 2g of dispersant BASF Disponil A1080, 1.1g of defoamer TEGO-825, and 0.6g of leveling agent TEGO-2300 were added, and the mixture was stirred to obtain a heat-resistant and anti-corrosion coating.

[0026] The coating was placed at room temperature for 30 days and the dispersion of the coating was observed.

[0027] Pour the paint onto the tinplate surface and dry it at 80℃ for 8h to form a paint film. Test the salt spray resistance of the paint film according to GB / T 1771-2007.

[0028] The coating is cured into a film, dried, weighed, and then immersed in water for 24 hours. After taking it out, wipe off the residual water on the surface, weigh it, and 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.

[0029] 8 mg of the film was weighed and placed in a thermogravimetric analyzer for thermal performance analysis in a nitrogen atmosphere at a heating rate of 10°C / min from 30°C to 700°C.

[0030] Table 1 Coating performance test Coating Dispersion Salt spray resistance (960h) Water absorption (%) Initial thermal decomposition temperature (°C) Mass residual rate (%) Example 1 No stratification No blistering, no peeling, no rusting 6.72 289.1 22.3 Example 2 No stratification No blistering, no peeling, no rusting 6.34 291.0 23.5 Example 3 No stratification No blistering, no peeling, no rusting 7.04 287.5 21.8 Example 4 No stratification No blistering, no peeling, no rusting 6.49 290.7 23.9 Comparative Example 1 No stratification No blistering, no peeling, no rusting 17.36 274.8 16.7 Comparative Example 2 Obvious stratification No blistering, no peeling, no rusting 4.69 289.6 22.5 Comparative Example 3 No stratification No blistering, no peeling, no rusting 9.18 282.7 19.0 After testing, Examples 1-4 use a carboxyl-containing diphenolic carboxylic acid chain extender as a water-based chain extender for polyurethane, and the resulting polyurethane coating has good water dispersibility, no stratification of the coating, and good storage stability. In addition, the diphenolic carboxylic acid chain extender contains a hydrophobic phenylindole and carbazole heterocycle, which is beneficial to reducing the water absorption rate of the waterborne polyurethane coating, improving water resistance, and improving the salt spray resistance and corrosion resistance of the coating. At the same time, the phenylindole and carbazole condensed ring structure has strong heat resistance and is not easy to be thermally decomposed, which is beneficial to increasing the thermal decomposition temperature of the polyurethane, and the condensed ring isomerizes and cross-links to form carbon at high temperature, which is beneficial to improving high-temperature carbonization and high-temperature mass residual rate, thereby improving the high-temperature resistance of the paint film.

[0031] In Comparative Example 1, ordinary 2,2-dihydroxymethylpropionic acid is used as a water-based chain extender. The obtained polyurethane coating has good water dispersibility, no stratification, and good storage stability. However, the water absorption rate is large, which is not conducive to improving the water resistance and salt spray resistance of the paint film. At the same time, the polyurethane does not contain a heat-resistant condensed ring structure, resulting in a low thermal decomposition temperature and mass residual rate, and the high temperature resistance of the paint film is poor.

[0032] Comparative Example 2 uses 6,12-diphenol-5,11-dihydroindole[3,2-b]carbazole as a chain extender, which does not contain a carboxyl group. The obtained polyurethane has poor hydrophilicity and water dispersibility, and a water-based coating with excellent storage stability cannot be obtained. However, the water absorption rate is low, the salt spray resistance is excellent, the thermal decomposition temperature and mass residual rate are high, and the high temperature resistance of the paint film is good.

[0033] In Comparative Example 3, 2,5-dihydroxyphthalic acid is used as a water-based chain extender, which does not contain the hydrophobic and heat-resistant phenylindolecarbazole fused ring structure, resulting in a 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 residual rate are low, and the high temperature resistance is poor.

[0034] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection 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.