Preparation method of chemical-corrosion-resistant special coating

Abstract

The invention provides a preparation method of a chemical-corrosion-resistant special coating. The preparation method comprises the following steps: firstly, preparing a silane oligomer; then, the terminated polyisocyanate is added into the silane oligomer; then, adding a certain amount of water, lower alcohol and an acetate solvent, and uniformly stirring; and finally, adding a certain amount of wetting agent to prepare the chemical-corrosion-resistant special coating. The coating is coated on a base material and cured under specific conditions to prepare a wear-resistant and chemical corrosion-resistant coating, and the coating has the characteristics of wear resistance, chemical corrosion resistance and low cost, and has wide application prospects.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of special coating preparation, and particularly relates to a preparation method of a chemical corrosion-resistant special coating. BACKGROUND

[0002] At present, the wet desulfurization technology is mainly used in power plants at home and abroad, and the wet desulfurization mainly comprises an absorbent preparation system, a flue gas system, a sulfur dioxide absorption system, a gypsum dehydration system, a waste water treatment system and other auxiliary systems. The condensate of flue gas includes corrosive factors such as sulfuric acid, sulfurous acid, hydrochloric acid, hydrates of nitrogen oxides, fluorides and chlorides, in addition to solid particulate matter. Therefore, the corrosion process of the desulfurization tower is not only the acid corrosion of the acid substances, but also the abrasion corrosion of the solid particulate matter.

[0003] In the prior art, the corrosion-resistant coating is often coated on the surface of the substrate, but the existing coating is soft in texture and not resistant to wear. In order to improve the wear resistance of the coating, fillers are often added, but the wear resistance of the coating prepared in this way is still insufficient to support thin coating, and after thin coating, it is insufficient to resist the abrasion corrosion of the desulfurization tower, and generally several hundred microns of coating are needed to achieve a good effect of resisting the abrasion corrosion.

[0004] In addition, although the addition of too much filler can improve the wear resistance of the coating to a certain extent, the cost of the coating will also increase, and at the same time, after the addition of the filler, the coating will become opaque and cannot be applied to the outer facade corrosion protection of the equipment with appearance decoration requirements.

[0005] To solve the above problems in the prior art, the application provides a preparation method of a special wear-resistant and chemical corrosion-resistant coating, the coating can guarantee good wear-resistant and corrosion-resistant effects under a coating thickness of 5-30 um, mainly because the silane oligomer in the application forms a high-hardness and high-wear-resistant silicon dioxide coating with a main body structure of Si-O-Si during curing, but if it is a pure silicon dioxide structure, the product is prone to cracking. The application innovatively adds a blocked polyisocyanate, which is opened at high temperature, and the isocyanate and the silane oligomer are crosslinked to improve the flexibility of the coating and make it not prone to cracking, and the introduction of the isocyanate enhances the overall corrosion resistance of the coating. Another reason for using the blocked polyisocyanate is that the coating of the application is an environmentally friendly water-based coating, and water exists in the coating, so free and unblocked polyisocyanate cannot be directly used, which will cause premature reaction of part of the isocyanate groups with water, thereby causing rapid reaction and gelation, and thus cannot be used. In addition, the coating does not need to add fillers, which saves the coating cost while guaranteeing the wear-resistant and corrosion-resistant effects, and because no fillers are added, the coating itself is transparent, and after the coating is coated on a substrate, it can be used for equipment outer facade corrosion protection, and various color pastes can be added to the coating to obtain various color corrosion-resistant coatings, which can be used for outer facade corrosion protection and also have a decorative effect. SUMMARY

[0006] The application provides a preparation method of a special chemical corrosion-resistant coating, and the specific steps are as follows: 1) First, prepare a silane oligomer, mix a certain amount of water and a lower alcohol, then take compounds A and B of a general formula according to the proportion, respectively R1 a R2 b SiX1 (4-a-b) and R3 c SiX2 (4-c) , add them to the above-mentioned mixed solvent, put the obtained mixed solution into a constant-temperature water bath and stir, the stirring speed is controlled at 400-600 rpm, in the stirring process, slowly drop the acid, the dropping speed is controlled at 20-30 drops / min, adjust the pH of the solution to the appropriate interval and continue to stir for 30-100 min to obtain the required silane oligomer.

[0007] 2) The temperature of the above-mentioned silane oligomer is reduced to 20-25 DEG C, and a blocked polyisocyanate is added to the above-mentioned silane oligomer according to the proportion, and stirring is started, the stirring speed is 300-400 rpm, and the stirring time is 10-60 min.

[0008] 3) A certain amount of water, a lower alcohol and an acetic ester solvent are added again, and a certain amount of a wetting agent is added to prepare the special chemical corrosion-resistant coating.

[0009] 4) The configured chemical corrosion resistant special coating is applied to the surface of the substrate, and the coating film is cured at a certain temperature for a period of time to obtain a wear-resistant and chemical corrosion-resistant coating.

[0010] Preferably, the compound of general formula A R1 a R2 b SiX1 (4-a-b) wherein a is 0 or 1, b is 0 to 3, and the sum of a and b can be 1, 2 or 3; the compound of general formula B R3 c SiX2 (4-c) wherein c is 0~3; R1 and R3 represent non-hydrolysable groups selected from alkyl, alkenyl, alkynyl and aryl; R2 represents non-hydrolysable groups including functional groups selected from silicon atom bonded ether-, amino-, monoalkylamino-, dialkylamino-, amido-, mercapto-; X1 and X2 represent hydrolysable groups selected from halogen, alkoxy, aryloxy, acyloxy, alkylcarbonyl; the lower alcohol is one or more of methanol, ethanol, isopropanol, n-butanol; the mass ratio of the compound of general formula A, the compound of general formula B, water, lower alcohol is in the range of 2:2:1:1 to 6:6:7:3; the constant temperature water bath temperature is in the range of 45~50℃; the pH value range is 4~5.

[0011] Preferably, the blocked polyisocyanate in step 2) is a compound blocked by the reaction of a blocking agent containing at least one active hydrogen atom with polyisocyanate; the polyisocyanate comprises one of dimer or trimer polyisocyanate; the blocking agent comprises one of butanone oxime, malonate, caprolactam, dimethylpyrazole; the reaction groups in the silane oligomer should be approximately the same stoichiometry as the reaction groups in the blocked polyisocyanate; the mass ratio of the silane oligomer to the blocked polyisocyanate is in the range of 11:3~3:1.

[0012] Preferably, the lower alcohol in step 3) is one or more of methanol, ethanol, isopropanol, n-butanol; the acetic acid ester solvent is ethyl acetate or butyl acetate; the wetting agent is polyether modified polydimethylsiloxane; the mass ratio of the mixed solution prepared in step 2 to water, lower alcohol, acetic acid ester solvent, wetting agent is in the range of 4:5:5:0.1~14:35:35:0.5.

[0013] Preferably, the substrate in step 4) is one of the commonly used galvanized sheet, cold rolled sheet, nickel-based alloy, carbon steel alloy, stainless steel, aluminum alloy; the curing temperature is 120~180℃; the curing time is 10~60min.

[0014] Compounds of general formula A include, but are not limited to, the following: C3H7Si(OCH3)3, (C6H5)2SiCl2, (H3C)2Si(OH)2, (H3C)2SiCl2, (C6H5)2Si(OCH3), (i-C3H7)3SiOH, (H3C)2Si(OC2H5)2, (C6H5)2Si(OC2H5)2, H2C-CH-SiCl3, H2C-CH-CH2-Si(OCH3)3, H2C-CH-Si(OCH2OCH3)3, H2C-CH-CH2-Si(OC2H5)3, H2C-CH-Si(OCH3)3, H2C-CH-CH2-Si(OCOCH3)3.

[0015] Compounds of general formula B include, but are not limited to, the following: Si(OCH3)4, Si(OC2H5)4, CH3-Si(OC2H5)3, SiCl4, Si(Oi-C3H7)4, C2H5-Si(OC2H5)3, HSiCl3, Si(OC4H9)4, H3C-SiCl3, C2H5-SiCl3, etc.

[0016] Polyisocyanates that can be used in blocking reactions include, but are not limited to, the following: 1,6-hexamethylene diisocyanate; isocyanurate of 1,6-hexamethylene diisocyanate; isophorone diisocyanate; isocyanurate of isophorone diisocyanate; tetramethylene diisocyanate, etc.

[0017] Blocked polyisocyanates include, but are not limited to, the following: 3,5-dimethylpyrazole-blocked aqueous isocyanates, malonic acid-blocked isocyanates, ε-caprolactam-double-terminated isocyanates, etc.

[0018] The wear-resistant and chemically resistant special coating of this invention can be applied to the surfaces of common substrates such as galvanized steel sheets, cold-rolled steel sheets, nickel-based alloys, carbon steel alloys, stainless steel, and aluminum alloys. It can be applied to the substrate using standard coating methods such as dip coating, brush coating, roller coating, spray coating, and spin coating, with spray coating and dip coating being particularly suitable. The coated substrate is cured at 120~180℃ for 10~60 minutes to form a wear-resistant and chemically resistant coating.

[0019] Compared with the prior art, the method for preparing the chemically resistant special coating of the present invention has the following beneficial effects:

[0020] The wear-resistant and chemically resistant special coating provided by this invention exhibits excellent adhesion to the substrate, ensuring good resistance to wear and corrosion even with a coating thickness of 5-30 μm. Furthermore, this coating also possesses excellent water and acid resistance. In addition, since no fillers are added to the coating provided by this invention, it significantly improves cost control during actual production and can be used for corrosion protection of equipment surfaces with aesthetic requirements. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Example 1

[0023] Add 5 parts of 0.1M hydrochloric acid to 20 parts of C3H7Si(OCH3)3 and 10 parts of Si(OCH3)4 with stirring. After 30 minutes, add 15 parts of 3,5-dimethylpyrazole-blocked aqueous isocyanate to the mixture and dissolve it with stirring. Add 40 parts of water and 10 parts of methanol, and finally add 0.2 parts of wetting agent.

[0024] The prepared coating is applied to the surface of the substrate by spraying. The substrate is then cured at 120°C for 60 minutes to allow the coating to fully cure, thus forming a wear-resistant and chemically resistant coating.

[0025] Example 2

[0026] Ten parts of 0.1M hydrochloric acid were added to 10 parts of (C6H5)2Si(OC2H5)2 and 20 parts of Si(OC2H5)4 under stirring. After 30 minutes, 20 parts of 3,5-dimethylpyrazole-blocked aqueous isocyanate were added to the mixture and dissolved under stirring. 30 parts of water and 10 parts of ethanol were added, and finally 0.2 parts of wetting agent were added.

[0027] The prepared coating is applied to the surface of the substrate by spraying. The substrate is then cured at 150°C for 40 minutes to allow the coating to fully cure, thus forming a wear-resistant and chemically resistant coating.

[0028] Example 3

[0029] Add 5 parts of 0.1M hydrochloric acid to 10 parts of H2C-CH-CH2-Si(OC2H5)3 and 25 parts of SiCl4 with stirring. After 30 minutes, add 10 parts of 3,5-dimethylpyrazole-blocked aqueous isocyanate to the mixture and dissolve it with stirring. Add 40 parts of water and 15 parts of ethanol, and finally add 0.2 parts of wetting agent.

[0030] The prepared coating is applied to the surface of the substrate by spraying. The substrate is then cured at 180°C for 20 minutes to allow the coating to fully cure, thus forming a wear-resistant and chemically resistant coating.

[0031] To better illustrate the characteristics of the wear-resistant and chemically resistant special coatings for flue gas equipment provided in the embodiments of the present invention, the coatings prepared in Examples 1 to 3 were subjected to performance testing, and the test results are shown in Table 1.

[0032] Table 1 Test item Test requirement Example 1 Example 2 Example 3 Film thickness (μm) / 15 13 9 Adhesion ≤1 0 0 1 Pencil hardness ≥1H 4H 5H 6H Abrasion resistance (mg) ≤30 18 12 7 acid resistance (5% H2SO4) 48h no abnormality 96h no abnormality 96h no abnormality 96h no abnormality CASS resistance 240h no abnormality 480h no abnormality 480h no abnormality 480h no abnormality Xenon lamp aging resistance 1000h no abnormality 2000h no abnormality 2000h no abnormality 2000h no abnormality Water resistance 240h no abnormality 480h no abnormality 480h no abnormality 480h no abnormality As can be seen from Table 1, the wear-resistant and chemically resistant special coating for flue gas equipment provided by the present invention has good adhesion to the substrate, and also has good water resistance and acid resistance. After 2000h artificial aging test, the paint film basically showed no change and had high hardness. It has excellent comprehensive performance and can provide good anti-corrosion and anti-erosion performance for flue gas equipment.

Claims

1. A method for preparing a special coating resistant to chemical corrosion, characterized in that, The specific steps are as follows: 1) First, prepare the silane oligomer by mixing a certain amount of water and a lower alcohol, and then take compounds of general formula A and B in proportion, which are R1 respectively. a R2 b SiX1 (4-a-b) and R3 c SiX2 (4-c) Add the above mixed solvent, place the resulting mixture in a constant temperature water bath and stir, with the stirring speed controlled at 400~600 rpm. During the stirring process, slowly add acid dropwise at a rate of 20~30 drops / min. Adjust the pH of the solution to a suitable range and continue stirring for 30~100 min to prepare the desired silane oligomer. 2) Cool the silane oligomer obtained in step 1) to 20~25℃, and add the end-capped polyisocyanate to the silane oligomer in proportion. Turn on the stirrer and stir at a speed of 300~400 rpm for 10~60 min to obtain a mixture. 3) Add a certain amount of water, lower alcohol and acetate solvent to the mixture obtained in step 2), stir evenly, and then add a certain amount of wetting agent to obtain a special coating resistant to chemical corrosion. 4) Apply the chemical corrosion resistant special coating obtained in step 3) to the surface of the substrate, and cure the coating at a certain temperature for a period of time to obtain a wear-resistant and chemical corrosion resistant coating.

2. The method for preparing a chemically resistant special coating according to claim 1, characterized in that, In step 1), the general formula compound R1 a R2 b SiX1 (4-a-b) In the formula R3, a is 0 or 1, b is 0 to 3, and the sum of a and b can be 1, 2, or 3; c SiX2 (4-c) In this context, c is 0~3; R1 and R3 represent non-hydrolyzable groups selected from alkyl, alkenyl, alkynyl, and aryl groups; R2 represents a non-hydrolyzable group including a functional group selected from silicon-bonded ether-, amino-, monoalkylamino-, dialkylamino-, amide-, and mercapto- groups; X1 and X2 represent hydrolyzable groups selected from halogens, alkoxy groups, aryloxy groups, acyloxy groups, and alkyl carbonyl groups; the lower alcohol is one or more of methanol, ethanol, isopropanol, and n-butanol; the mass ratio of the general formula A compound, general formula B compound, water, and lower alcohol is in the range of 2:2:1:1 to 6:6:7:3; the constant temperature water bath temperature range is 45~50℃; and the pH value range is 4~5.

3. The method for preparing a chemically resistant special coating according to claim 1, characterized in that, In step 2), the capped polyisocyanate comprises a compound formed by the reaction of a blocking agent containing at least one active hydrogen atom with the polyisocyanate for capping; the polyisocyanate comprises one of dimer or trimer polyisocyanate; the blocking agent comprises one of butanone oxime, malonate, caprolactam, and dimethylpyrazole; the reactive groups in the silane oligomer should have approximately the same stoichiometry as the reactive groups in the capped polyisocyanate; the mass ratio of the silane oligomer to the capped polyisocyanate is in the range of (11:3) to (3:1).

4. The method for preparing a chemically resistant special coating according to claim 1, characterized in that, In step 3), the lower alcohol is one or more of methanol, ethanol, isopropanol, and n-butanol; the acetate solvent is ethyl acetate or butyl acetate; the wetting agent is polyether-modified polydimethylsiloxane; the mass ratio of the mixture obtained in step 2) to water, lower alcohol, acetate solvent, and wetting agent is in the range of 4:5:5:0.1 to 14:35:35:0.

5.

5. The method for preparing a chemically resistant special coating according to claim 1, characterized in that, In step 4), the substrate is one of the common galvanized steel sheet, cold-rolled steel sheet, nickel-based alloy, carbon steel alloy, stainless steel, and aluminum alloy; the curing temperature is 120~180℃; and the curing time is 10~60min.