A high-temperature-resistant coating and a preparation method thereof

Abstract

The application relates to the paint technology field and discloses a high-temperature-resistant paint and a preparation method thereof. Epoxy resin, a filler, a dispersing agent and a defoaming agent are added into a solvent, a curing agent is added after stirring, and the high-temperature-resistant paint is obtained. The curing agent is composed of a polyamide curing agent and UPy diamino diphenyl sulfone; UPy structure forms stable quadruple hydrogen bond action in the molecular chain bond of the epoxy resin, the crosslinking density of the epoxy resin is improved, when the epoxy resin is stressed, the quadruple hydrogen bond can be broken by absorbing energy at the same time, stress can be consumed and energy can be transmitted, the paint curing product is not damaged by stress, has good toughening effect, and the toughness of the paint film is improved. The heat-resistant diphenyl sulfone structure is introduced into the molecular chain of the epoxy resin, the high-temperature-resistant performance of the paint is improved, and the paint has higher thermal decomposition temperature.

Description

Technical Field

[0001] This invention relates to the field of coating technology, specifically to a high-temperature resistant coating and its preparation method. Background Technology

[0002] Epoxy resin coatings are widely used in flooring, pipelines, automobiles, ships and other fields. Although epoxy resin has good acid and alkali resistance, corrosion resistance and mechanical strength, its toughness is poor and the paint film is prone to cracking, which will affect the protective effect of the coating. In addition, epoxy resin has poor high temperature resistance, which limits the practical application of epoxy resin coatings.

[0003] Curing agents for epoxy resins mainly include amine curing agents and acid anhydride curing agents, which have a significant impact on the performance of epoxy resins and their coatings. For example, polyamide curing agents can improve the toughness of epoxy resins, but they are unlikely to improve their heat resistance and other properties. 4,4'-diaminodiphenyl sulfone can improve the heat resistance of epoxy resins, but it cannot improve their toughness. Patent CN113185899B discloses a method for preparing an epoxy coating with self-healing function at room temperature, using polyamides with reversible quadruple hydrogen bond groups in the branched chains as curing agents, which improves the self-healing and anti-corrosion properties of epoxy resin coatings. However, this patent does not solve the problem of poor high-temperature resistance of epoxy resins. Summary of the Invention

[0004] (a) Technical problem solved: The present invention solves the problem of poor high temperature resistance and toughness of epoxy resin coatings.

[0005] (II) Technical solution: A high-temperature resistant coating, which, by weight, comprises 100 parts epoxy resin, 18-30 parts filler, 1-1.6 parts dispersant, 0.7-1.2 parts defoamer, and 40-47 parts curing agent; the curing agent is composed of 23-41 parts polyamide curing agent and 6-15 parts UPy diaminodiphenyl sulfone.

[0006] The preparation method of high-temperature resistant coating includes the following steps: adding solvent and epoxy resin to a container, stirring, adding filler, dispersant and defoamer, stirring, adding curing agent, and obtaining high-temperature resistant coating.

[0007] Preferably, the filler includes any one or combination of silicon micro powder, silicon carbide micro powder, alumina micro powder, corundum powder, and zinc oxide.

[0008] Preferably, the solvent is any one or a combination of n-butanol, ethyl acetate, toluene, and xylene.

[0009] Preferably, the preparation method of UPy diaminodiphenyl sulfone includes the following steps:

[0010] Step (1) 2-amino-4-hydroxy-6-methylpyrimidine and hexamethylene diisocyanate were reacted to obtain Upy-HDI; then Upy-HDI and 3,3'-dinitro-4,4'-dihydroxydiphenyl sulfone were added to the reaction solvent and reacted at 40-90℃ for 2-5 h under a nitrogen atmosphere. The crude product was separated by silica gel column chromatography to obtain UPy dinitrodiphenyl sulfone.

[0011] Step (2) Add ethanol, hydrazine hydrate solution, UPy dinitrodiphenyl sulfone, and palladium on carbon to 1,4-dioxane. React at 60-70℃ for 24-30 h under nitrogen atmosphere. After filtration, distill the filtrate under reduced pressure. Separate the crude product by silica gel column chromatography to obtain UPy diaminodiphenyl sulfone.

[0012] Preferably, in step (1), the amount of 3,3'-dinitro-4,4'-dihydroxydiphenyl sulfone is 100 parts by weight, and the amount of Upy-HDI is 172-190 parts.

[0013] Preferably, the reaction solvent in step (1) is dichloromethane or toluene.

[0014] Preferably, in step (2), the amount of UPy dinitrodiphenyl sulfone is 100 parts by weight, and the amount of palladium on carbon catalyst is 1.6-2.2 parts.

[0015] Preferably, in step (2), the volume ratio of 1,4-dioxane, ethanol, and hydrazine hydrate solution is (100-150):100:(20-30).

[0016] (III) Beneficial technical effects: The UPy diaminodiphenyl sulfone of the present invention contains multiple amino groups, which can replace part of the polyamide curing agent and react with epoxy resin coatings to cure. The UPy structure and diphenyl sulfone structure are introduced into the epoxy resin molecular chain. The UPy structure forms a stable quadruple hydrogen bond in the epoxy resin molecular chain, which increases the crosslinking density of the epoxy resin. When the epoxy resin is subjected to stress, the quadruple hydrogen bond can absorb energy and break, which can consume stress and transfer energy, so that the cured coating is not damaged by stress. It has a good toughening effect and improves the toughness of the paint film.

[0017] This invention introduces a heat-resistant diphenyl sulfone structure into the epoxy resin molecular chain, which is beneficial to improving the high-temperature resistance of the coating and giving it a higher thermal decomposition temperature. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention are described clearly and completely below. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0019] The epoxy resin model is E51; the polyamide curing agent model is polyamide 650. The CAS number of 3,3'-dinitro-4,4'-dihydroxydiphenyl sulfone is 7149-20-4; the CAS number of 3,3'-dinitro-[1,1'-biphenyl]-4,4'-diol is 66041-61-0.

[0020] Example 1

[0021] Step (1): 50g Upy-HDI and 86g 3,3'-dinitro-4,4'-dihydroxydiphenyl sulfone were added to 1.2L of dichloromethane. The mixture was refluxed at 40℃ for 5h under a nitrogen atmosphere. The mixture was then distilled under reduced pressure. The crude product was separated by silica gel column chromatography using a mixture of dichloromethane and methanol as the eluent to obtain UPy-dinitrodiphenyl sulfone. The preparation reaction formula is:

[0022] .

[0023] Step (2): Add 0.8 L of ethanol, 180 mL of hydrazine hydrate solution (80% by mass), 70 g of UPy dinitrodiphenyl sulfone, and 1.12 g of palladium on carbon to 1 L of 1,4-dioxane. Reflux at 70 °C for 24 h under a nitrogen atmosphere to reduce the nitro group to an amino group. After filtration, distill the filtrate under reduced pressure. Separate the crude product by silica gel column chromatography using a mixture of dichloromethane and methanol as the eluent to obtain UPy diaminodiphenyl sulfone. The structural formula is:

[0024] .

[0025] Step (3): Add 100mL ethyl acetate, 120mL xylene, and 1kg epoxy resin to the container. After stirring, add 160g silica powder, 80g zinc oxide, 14g dispersant, and 12g defoamer. After stirring, add 410g polyamide curing agent and 60g UPy diaminodiphenyl sulfone as curing agent to obtain a high-temperature resistant coating.

[0026] Example 2

[0027] Step (1): Add 50g Upy-HDI and 95g 3,3'-dinitro-4,4'-dihydroxydiphenyl sulfone to 1L of toluene. Reflux the mixture at 90℃ for 2h under a nitrogen atmosphere. Distill under reduced pressure. Separate the crude product by silica gel column chromatography with a mixed solution of dichloromethane and methanol as the eluent to obtain UPy dinitrodiphenyl sulfone.

[0028] Step (2): Add 0.8L of ethanol, 160mL of hydrazine hydrate solution (mass fraction 80%), 70g of UPy dinitrodiphenyl sulfone, and 1.57g of palladium on carbon to 1.2L of 1,4-dioxane. Reflux the mixture at 70℃ for 24h under a nitrogen atmosphere. After filtration, distill the filtrate under reduced pressure. Separate the crude product by silica gel column chromatography using a mixture of dichloromethane and methanol as the eluent to obtain UPy diaminodiphenyl sulfone.

[0029] Step (3): Add 80mL n-butanol, 130mL toluene, and 1kg epoxy resin to the container. After stirring, add 130g silicon carbide micro powder, 170g alumina micro powder, 10g dispersant, and 9g defoamer. After stirring, add 330g polyamide curing agent and 100g UPy diaminodiphenyl sulfone as curing agent to obtain a high-temperature resistant coating.

[0030] Example 3

[0031] Step (1): Add 50g Upy-HDI and 93g 3,3'-dinitro-4,4'-dihydroxydiphenyl sulfone to 1L of toluene. Reflux the mixture at 90℃ for 3h under a nitrogen atmosphere. Distill under reduced pressure. Separate the crude product by silica gel column chromatography using a mixture of dichloromethane and methanol as the eluent to obtain UPy dinitrodiphenyl sulfone.

[0032] Step (2): Add 0.8L of ethanol, 240mL of hydrazine hydrate solution (mass fraction 80%), 70g of UPy dinitrodiphenyl sulfone, and 1.34g of palladium on carbon to 0.8L of 1,4-dioxane. Reflux the mixture at 60℃ for 30h under a nitrogen atmosphere. After filtration, distill the filtrate under reduced pressure. Separate the crude product by silica gel column chromatography with a mixed solution of dichloromethane and methanol as the eluent to obtain UPy diaminodiphenyl sulfone.

[0033] Step (3): Add 100mL ethyl acetate, 120mL xylene, and 1kg epoxy resin to the container. After stirring, add 140g silica powder, 40g corundum powder, 16g dispersant, and 7g defoamer. After stirring, add 230g polyamide curing agent and 150g UPy diaminodiphenyl sulfone as curing agent to obtain a high-temperature resistant coating.

[0034] Comparative Example 1:

[0035] Step (1): Add 100mL ethyl acetate, 120mL xylene, and 1kg epoxy resin to a container. After stirring, add 160g silica powder, 80g zinc oxide, 14g dispersant, and 12g defoamer. After stirring, add 410g polyamide curing agent to obtain the coating.

[0036] Comparative Example 2:

[0037] Step (1): Prepare UPy dinitrodiphenyl sulfone according to the method of Example 1.

[0038] Step (2): Add 100mL ethyl acetate, 120mL xylene, and 1kg epoxy resin to the container. After stirring, add 160g silica powder, 80g zinc oxide, 14g dispersant, and 12g defoamer. After stirring, add 410g polyamide curing agent and 60g UPy dinitrodiphenyl sulfone as curing agent to obtain the coating.

[0039] Comparative Example 3:

[0040] Step (1): Add 100mL ethyl acetate, 120mL xylene, and 1kg epoxy resin to a container. After stirring, add 160g silica powder, 80g zinc oxide, 14g dispersant, and 12g defoamer. After stirring, add 410g polyamide curing agent and 60g 4,4'-diaminodiphenyl sulfone as curing agents to obtain the coating.

[0041] Comparative Example 4:

[0042] Step (1): 50g Upy-HDI and 86g 3,3'-dinitro-[1,1'-biphenyl]-4,4'-diol were added to 1.2L of dichloromethane. The mixture was refluxed at 40℃ for 5h under a nitrogen atmosphere. The reaction was then carried out under reduced pressure. The crude product was separated by silica gel column chromatography using a mixture of dichloromethane and methanol as the eluent to obtain UPy-dinitrobiphenyl. The structural formula is as follows:

[0043] .

[0044] Step (2): Add 0.8 L of ethanol, 180 mL of hydrazine hydrate solution (80% by mass), 70 g of UPy dinitrodiphenyl sulfone, and 1.12 g of palladium on carbon to 1 L of 1,4-dioxane. Reflux at 70 °C for 24 h under a nitrogen atmosphere. After filtration, distill the filtrate under reduced pressure. Separate the crude product by silica gel column chromatography using a mixture of dichloromethane and methanol as the eluent to obtain UPy diaminobiphenyl. The structural formula is as follows:

[0045] .

[0046] Step (3): Add 100mL ethyl acetate, 120mL xylene, and 1kg epoxy resin to the container. After stirring, add 160g silica powder, 80g zinc oxide, 14g dispersant, and 12g defoamer. After stirring, add 410g polyamide curing agent and 60g UPy diaminobiphenyl as curing agent to obtain the coating.

[0047] The coating was sprayed onto the tinplate surface and cured sequentially at 80℃ for 1 hour, 110℃ for 2 hours, and then left at room temperature for 24 hours. The flexibility of the coating film was tested according to standard GB / T 1731-2020.

[0048] Weigh 6 mg of the paint film and test its thermal properties in a thermogravimetric analyzer. The temperature was increased from 25°C to 800°C at a rate of 5°C / min, and the test atmosphere was nitrogen.

[0049] The tensile properties of the cured coating were tested according to standard GB / T 1040.1-2018.

[0050] Coating performance

[0051] Compared to Comparative Example 1, the epoxy resin coatings of Examples 1 to 3 contained UPy diaminodiphenyl sulfone, which contains multiple amino groups and can replace part of the polyamide curing agent to undergo a curing reaction with the epoxy resin, thereby forming multiple UPy structures ( The introduction of diphenyl sulfone (UPy) structures into the epoxy resin molecular chain creates more stable quadruple hydrogen bonds, increasing the crosslinking density and maintaining good tensile strength. When the epoxy resin is subjected to stress, the quadruple hydrogen bonds absorb energy and break, effectively dissipating stress and transferring energy, preventing stress damage to the cured coating and thus providing excellent toughening. The film flexibility is 0.5-1 mm, and the elongation at break of the cured product reaches 18.3-33.7%. Furthermore, the introduction of heat-resistant diphenyl sulfone structures into the epoxy resin molecular chain improves the coating's high-temperature resistance and results in a higher thermal decomposition temperature.

[0052] Comparative Example 2's UPy dinitrodiphenyl sulfone does not contain amino groups and cannot undergo a curing reaction with epoxy resin. It cannot introduce the UPy structure and diphenyl sulfone structure into the epoxy resin molecular chain, resulting in poor toughening effect, poor coating toughness, and a significantly lower thermal decomposition temperature than in Example 1.

[0053] Comparative Example 3, which incorporated 4,4'-diaminodiphenyl sulfone, showed a significantly lower elongation at break and poorer toughness compared to Example 1.

[0054] The UPy diaminobiphenyl in Comparative Example 4 does not contain a heat-resistant diphenyl sulfone structure, resulting in a significantly lower initial thermal decomposition temperature of the epoxy resin coating compared to Example 1, and poorer high-temperature resistance.

Claims

1. A high-temperature resistant coating, characterized in that, By weight, the high-temperature resistant coating comprises 100 parts epoxy resin, 18-30 parts filler, 1-1.6 parts dispersant, 0.7-1.2 parts defoamer, and 40-47 parts curing agent; The curing agent is composed of 23-41 parts of polyamide curing agent and 6-15 parts of UPy diaminodiphenyl sulfone; The structural formula of the UPy diaminodiphenyl sulfone is: 。 2. The high-temperature resistant coating according to claim 1, characterized in that, The filler includes any one or a combination of silicon micro powder, silicon carbide micro powder, alumina micro powder, corundum powder, and zinc oxide.

3. The high-temperature resistant coating according to claim 1, characterized in that, The preparation method of the UPy diaminodiphenyl sulfone includes the following steps: Step (1) 2-amino-4-hydroxy-6-methylpyrimidine and hexamethylene diisocyanate were reacted to obtain Upy-HDI; then Upy-HDI and 3,3'-dinitro-4,4'-dihydroxydiphenyl sulfone were added to the reaction solvent and reacted at 40-90℃ for 2-5 h under a nitrogen atmosphere. The crude product was separated by silica gel column chromatography to obtain UPy dinitrodiphenyl sulfone. Step (2) Add ethanol, hydrazine hydrate solution, UPy dinitrodiphenyl sulfone, and palladium on carbon to 1,4-dioxane. React at 60-70℃ for 24-30 h under nitrogen atmosphere. After filtration, distill the filtrate under reduced pressure. Separate the crude product by silica gel column chromatography to obtain UPy diaminodiphenyl sulfone.

4. The high-temperature resistant coating according to claim 3, characterized in that, By weight, the amount of 3,3'-dinitro-4,4'-dihydroxydiphenyl sulfone used in step (1) is 100 parts, and the amount of Upy-HDI is 172-190 parts.

5. The high-temperature resistant coating according to claim 3, characterized in that, The reaction solvent in step (1) is dichloromethane or toluene.

6. The high-temperature resistant coating according to claim 3, characterized in that, By weight, the amount of UPy dinitrodiphenyl sulfone used in step (2) is 100 parts, and the amount of palladium on carbon catalyst is 1.6-2.2 parts.

7. The high-temperature resistant coating according to claim 3, characterized in that, In step (2), the volume ratio of 1,4-dioxane, ethanol, and hydrazine hydrate solution is (100-150):100:(20-30).

8. A method for preparing a high-temperature resistant coating as described in any one of claims 1-7, characterized in that, The preparation method includes the following steps: adding solvent and epoxy resin to a container, stirring, then adding filler, dispersant and defoamer, stirring, then adding curing agent to obtain high-temperature resistant coating.

9. The method for preparing the high-temperature resistant coating according to claim 8, characterized in that, The solvent is any one or a combination of n-butanol, ethyl acetate, toluene, and xylene.

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