High-temperature-resistant coating in acetate reaction kettle and preparation method of high-temperature-resistant coating

Abstract

The invention provides a high-temperature-resistant coating in an acetate reaction kettle. The high-temperature-resistant coating in the acetate reaction kettle is prepared from polymethylphenyl siloxane, modified metal oxide, texanol, an emulsifier, polyethylene glycol and a flatting agent, wherein the modified metal oxide is a product formed by reacting and grafting a blend of hydroxylated aluminum oxide, iron oxide and zinc oxide with KH-570 and then carrying out free radical polymerization. After inorganic particles such as aluminum oxide are modified by KH-570, surface hydroxyl groups and Si-OH generated by hydrolysis of KH-570 are condensed, grafted double bonds are polymerized to form organic chain segments, and the particles are used as rigid nodes to be connected into a compact integrated net-shaped structure. According to the structure, the mechanical property, chemical stability and high-temperature stability of the coating can be improved, and the particle dispersity can be optimized. Meanwhile, the polymethylphenylsiloxane serves as a matrix, basic high temperature resistance and chemical inertness are provided for the coating, the coating can be prevented from cracking, the film forming stability is guaranteed, and the cohesiveness of the coating and the reaction kettle matrix is enhanced.

Description

Technical Field

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

[0002] Acetate compounds are core organic chemical raw materials in fields such as coating solvents, adhesive monomers, and pharmaceutical intermediates. Their industrial production scale continues to expand with the demand from downstream industries. As the core equipment for acetate synthesis, the reactor must withstand extremely harsh operating conditions for extended periods. On the one hand, acetate synthesis largely relies on transesterification or esterification reactions, which generally involve high temperatures, placing extremely high demands on the high-temperature stability of the equipment's inner wall materials. On the other hand, media such as glacial acetic acid in the reaction system are corrosive to the reactor's metal inner wall. Long-term contact can lead to corrosion failure of the reactor's metal inner wall, not only shortening the equipment's lifespan but also allowing metal impurities to seep into the product, resulting in decreased acetate purity and affecting product quality. Furthermore, materials easily adhere and form scale on the reactor wall during the reaction process, increasing cleaning difficulty and energy consumption, and causing uneven local heat transfer, affecting reaction efficiency and product yield. Therefore, developing reactor inner wall coatings that can withstand high temperatures for extended periods, resist chemical corrosion, have strong adhesion, and are anti-adhesive has become a key requirement for overcoming the bottlenecks in acetate production. Moreover, as the industry's requirements for product purity and equipment service life increase, the performance shortcomings of traditional coating technologies are becoming increasingly apparent.

[0003] Current technological explorations in the industry regarding high-temperature protection of reactors mainly revolve around three major directions: "base material framework construction - functional filler reinforcement - auxiliary performance optimization." In terms of base material selection, silicone resins have become the mainstream choice due to the high thermal stability of the siloxane backbone. Among them, polymethylphenylsiloxane, due to its combination of heat resistance and a certain degree of flexibility, is often used in coatings for medium- and high-temperature applications. Regarding functional fillers, the industry mostly uses single or simple physical mixtures of metal oxides, utilizing their high hardness and high-temperature resistance to improve the mechanical strength and heat resistance of the coating. Some solutions reduce film-forming defects by controlling the filler particle size. In addition, some technologies have attempted to use ceramic coatings (forming a dense structure through high-temperature sintering) or metal-based composite coatings. However, ceramic coatings suffer from high brittleness and are prone to cracking due to temperature cycling, while metal-based coatings face problems such as high cost and poor compatibility with organic reaction systems, making large-scale application in acetate reactors difficult.

[0004] However, existing technologies still face significant performance bottlenecks under the unique operating conditions of acetate reactors, failing to meet the industry's core requirements for coatings that offer "long-term stability and multi-functionality." Firstly, the compatibility and dispersibility between metal oxide fillers and silicone substrates are insufficient. Single or simply mixed metal oxides exhibit strong surface polarity, and even with conventional coupling agent treatment, only a shallow surface modification can be formed. Aggregation easily occurs within the silicone substrate, leading to uneven internal structure of the coating. At high temperatures, internal stress arises due to differences in thermal expansion coefficients, causing coating cracking and peeling, with a protection failure period generally shorter than 6 months. Secondly, the interfacial bonding strength between fillers and substrates is weak. Conventional coupling agent modification only forms weak chemical bonds between metal oxides and silicone substrates. Under long-term exposure to high temperatures and the corrosive effects of acetic acid and alcohols, the interface easily dissociates, resulting in peeling and blistering of the coating, preventing sustained adhesion to the reactor wall. Thirdly, coating performance cannot simultaneously meet multiple requirements. In existing technologies, single metal oxide fillers cannot simultaneously satisfy high-temperature resistance, corrosion resistance, anti-adhesion, and mechanical toughness. For example, although alumina is resistant to high temperatures, it has poor toughness and is prone to cracking due to temperature fluctuations; iron oxide has good corrosion resistance but poor dispersibility, which can easily lead to uneven coating surfaces and increase material adhesion; simply mixing multiple metal oxides can only achieve a simple superposition of performance, and cannot form a synergistic effect, making it difficult to cope with the multiple challenges of "high temperature + corrosion + adhesion" in acetate reactors; fourth, the long-term stability of the coating is poor. Under high-temperature cycling and long-term immersion in the reaction medium, some coatings are prone to problems such as aging and degradation of organosilicon base materials and dissolution of metal oxides, which leads to a decrease in coating density and a rapid decline in corrosion resistance. It can only maintain effective protection for a short period of time, requiring frequent shutdowns for recoating, which seriously affects the continuity and economy of acetate production; fifth, there is a contradiction between construction performance and practical performance. In order to improve high-temperature resistance, some solutions will excessively increase the amount of metal oxide fillers, which will lead to increased coating viscosity and poor leveling. After construction, the coating surface is prone to scratches and depressions, which will aggravate material adhesion, increase cleaning difficulty and coating wear rate, forming a vicious cycle of "performance improvement - decline in practical experience". The existence of these technical bottlenecks highlights the urgent need for a new coating technology solution to overcome the limitations of existing technologies and meet the pressing demand of acetate reaction vessels for high-performance protective coatings.

[0005] In conclusion, a new technical solution is urgently needed to address the problems existing in the current technology. Summary of the Invention

[0006] To address the deficiencies and shortcomings of the existing technology, this invention provides a high-temperature resistant coating for acetate reactors and its preparation method. The high-temperature resistant coating for acetate reactors provided by this invention possesses excellent high-temperature stability, strong and long-lasting corrosion resistance, superior adhesion and mechanical properties, and a balanced performance in both application and practicality. It can be adapted to the harsh operating conditions of acetate reactors, including high temperatures, strong corrosion, and material adhesion, significantly extending the effective protection period of the coating and reducing equipment maintenance costs.

[0007] One object of the present invention is to provide a high-temperature resistant coating for an acetate reaction vessel, the high-temperature resistant coating comprising the following components in parts by weight: 100-120 parts of polymethylphenylsiloxane 20-30 parts of modified metal oxide 2-4 parts of alcohol ester twelve 1-3 parts emulsifier 10-20 parts of polyethylene glycol Leveling agent 1-3 parts; The modified metal oxide is a product formed by reacting a blend of hydroxylated alumina, iron oxide, and zinc oxide with KH-570 and then undergoing free radical polymerization.

[0008] Furthermore, the mass ratio of the alumina, iron oxide, and zinc oxide is 1:(2-5):(2-8).

[0009] Furthermore, the particle size of the alumina, iron oxide, and zinc oxide is 1-20 μm.

[0010] Furthermore, the polymethylphenylsiloxane is selected from polymethylphenylsiloxanes with a molecular weight of 1500-3000.

[0011] Furthermore, the polyethylene glycol is selected from polyethylene glycols with a molecular weight of 200-1000.

[0012] Furthermore, the emulsifier is selected from one or more of polyoxyethylene lauryl ether, trimethylolpropane trioctanoic acid, and monododecyl phosphate.

[0013] Furthermore, the leveling agent is selected from one or more of polyether-modified polydimethylsiloxane and perfluoroalkyl ether-modified polysiloxane.

[0014] Another object of the present invention is to provide a method for preparing a high-temperature resistant coating in an acetate reaction vessel, the method comprising the following steps: S1. Aluminum oxide, iron oxide, and zinc oxide are subjected to hydroxylation treatment to obtain a mixture; S2. The mixture is blended with KH-570, heated and stirred to react, and a modified mixture is obtained. S3. Disperse the modified mixture in toluene, add a catalyst, and heat to react, thereby obtaining the modified metal oxide; S4. First, the modified metal oxide is mixed with other components, then mixed with water, sprayed onto the surface of the reactor substrate, sintered at high temperature, cooled and removed to obtain a high-temperature resistant coating in the acetate reactor.

[0015] Further, in step S2, the mass ratio of the mixture to KH-570 is 2:(1-2).

[0016] Furthermore, in step S2, the heating temperature is 60-90℃.

[0017] Furthermore, in step S3, the heating temperature is 60-80℃.

[0018] Furthermore, in step S4, the sintering temperature is 500-600℃.

[0019] The present invention has the following beneficial effects: This invention provides a high-temperature resistant coating for an acetate reactor. The high-temperature resistant coating comprises polymethylphenylsiloxane, modified metal oxide, dodecyl alcohol ester, emulsifier, polyethylene glycol, and leveling agent. The modified metal oxide is a product formed by grafting a blend of hydroxylated alumina, iron oxide, and zinc oxide with KH-570, followed by free radical polymerization. As solid inorganic particles doped in the coating, alumina, iron oxide, and zinc oxide possess extremely high molecular melting points and good high-temperature chemical stability. After modification with KH-570, the surface hydroxyl groups condense with Si-OH generated from the hydrolysis of KH-570 alkoxy groups. The grafted carbon-carbon double bonds then form organic segments through free radical polymerization. This prevents aggregation, and the metal oxides act as rigid nodes, interconnected by the organic segments to form a dense and stable integrated network structure. This structure offers several advantages. First, using 1-20 μm metal oxide particles as rigid nodes in the network, interconnected by organic segments, significantly enhances the coating's hardness and wear resistance while preventing brittle fracture caused by isolated metal oxides. This particle size avoids the agglomeration tendency of nano-sized particles and the dispersion difficulties of large-sized particles, while filling coating voids to improve density and ensure film smoothness. It also provides sufficient specific surface area and particle strength to fully utilize the rigid node function. Second, its dense network structure and highly stable rigid nodes synergistically enhance the coating's chemical and high-temperature stability, preventing damage under high temperatures and from acetic acid and alcohol-based media. Third, the good compatibility between the organic segments on the metal oxide surface and polymethylphenylsiloxane allows for better dispersion of solid inorganic particles in the system, resulting in a more uniform and smooth film. Meanwhile, polymethylphenylsiloxane, as the organic core matrix of the coating, plays a crucial role: its high bond energy Si-O main chain and phenyl structure provide the coating with basic high temperature resistance and chemical inertness; its own flexibility can buffer the high temperature shrinkage stress of inorganic particles and prevent the coating from cracking; during curing, it will also form a cross-linked network, which not only ensures the stability of film formation, but also enhances the adhesion between the coating and the reactor substrate, preventing peeling during long-term use. Detailed Implementation

[0020] To more clearly illustrate the technical solution of the present invention, the following embodiments are provided. Unless otherwise stated, the raw materials, reactions, and post-processing methods appearing in the embodiments are all commercially available raw materials and technical methods well known to those skilled in the art.

[0021] The terms "preferred," "more preferably," and "more suitable" used in this invention refer to embodiments of the invention that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this invention.

[0022] It should be understood that, except in any operational instance or otherwise indicated, the amounts or all figures representing ingredients used, for example, in the specification and claims, should be understood to be modified by the term "about" in all cases. Therefore, unless otherwise stated, the numerical parameters set forth in the following specification and appended claims are approximate values ​​varying according to the desired performance to be obtained according to the invention.

[0023] In embodiments of the present invention, the following raw materials will be used: Polymethylphenylsiloxane, brand name P331251, was purchased from Aladdin.

[0024] Alumina, with a particle size of 1-5 μm, was purchased from Shanghai Yuanjiang Chemical.

[0025] Iron oxide, with a particle size of 1-10 μm, was purchased from Shanghai Yunfu Nanotechnology Co., Ltd.

[0026] Zinc oxide, with a particle size of 1-10 μm, was purchased from Yumu New Materials Co., Ltd.

[0027] Polyethylene glycol, brand name P103737, was purchased from Aladdin.

[0028] The emulsifier, polyoxyethylene lauryl ether, brand name AEO-9, was purchased from BASF.

[0029] The leveling agent, polyether-modified polydimethylsiloxane, brand name BYK-333, was purchased from BYK in Germany.

[0030] Unless otherwise specified, the water used in the embodiments of this invention refers to deionized water.

[0031] In the embodiments of this invention, "parts" refers to parts by mass.

[0032] Example 1 A high-temperature resistant coating for an acetate reaction vessel, the high-temperature resistant coating comprising the following components in parts by weight: 120 parts of polymethylphenylsiloxane 25 parts of modified metal oxide 3 parts of alcohol ester twelve 2 parts emulsifier 20 parts of polyethylene glycol 1 part leveling agent; The method for preparing the high-temperature resistant coating in the acetate reaction vessel includes the following steps: S1. Mix 10 parts of aluminum oxide, 20 parts of iron oxide and 40 parts of zinc oxide in 200 parts of 10 wt% H2O2 aqueous solution, heat to 60℃, stir at 500 rpm for 4 h, filter, dry to obtain mixture; S2. Using 100 parts of 60 wt% ethanol aqueous solution as solvent, 5 parts of the above mixture are mixed with 5 parts of KH-570, heated and stirred at 80℃ and 300 r / min for 2 h, and the solvent is removed to obtain the modified mixture. S3. Under a nitrogen atmosphere, 50 parts of the modified mixture were dispersed in 200 parts of toluene, 0.5 parts of azobisisobutyronitrile were added, and the mixture was heated at 70°C for 6 h to remove the solvent, thereby obtaining the modified metal oxide. S4. According to the above mass proportions, the modified metal oxide is mixed with other components, 40 parts of water are added, the mixture is stirred evenly, and sprayed onto the surface of the reactor substrate. The mixture is sintered at 500°C for 40 min, cooled, and then removed to obtain a high-temperature resistant coating in the acetate reactor.

[0033] Example 2 A high-temperature resistant coating for an acetate reaction vessel, the high-temperature resistant coating comprising the following components in parts by weight: 100 parts of polymethylphenylsiloxane 20 parts of modified metal oxide 2 parts of alcohol ester twelve 1 part emulsifier 10 parts of polyethylene glycol 2 parts leveling agent; The method for preparing the high-temperature resistant coating in the acetate reaction vessel includes the following steps: S1. Mix 10 parts of alumina, 30 parts of iron oxide and 50 parts of zinc oxide in 200 parts of 10 wt% H2O2 aqueous solution, heat to 60℃, stir at 500 rpm for 4 h, filter, and dry to obtain the mixture. S2. Using 100 parts of 60 wt% ethanol aqueous solution as solvent, 5 parts of the above mixture are mixed with 5 parts of KH-570, heated and stirred at 80℃ and 300 r / min for 2 h, and the solvent is removed to obtain the modified mixture. S3. Under a nitrogen atmosphere, 50 parts of the modified mixture were dispersed in 200 parts of toluene, 0.5 parts of azobisisobutyronitrile were added, and the mixture was heated at 70°C for 6 h to remove the solvent, thereby obtaining the modified metal oxide. S4. According to the above mass proportions, the modified metal oxide is mixed with other components, 40 parts of water are added, the mixture is stirred evenly, and sprayed onto the surface of the reactor substrate. The mixture is sintered at 500°C for 40 min, cooled, and then removed to obtain a high-temperature resistant coating in the acetate reactor.

[0034] Example 3 A high-temperature resistant coating for an acetate reaction vessel, the high-temperature resistant coating comprising the following components in parts by weight: 110 parts of polymethylphenylsiloxane 30 parts of modified metal oxide 2 parts of alcohol ester twelve 2 parts emulsifier 10 parts of polyethylene glycol 2 parts leveling agent; The method for preparing the high-temperature resistant coating in the acetate reaction vessel includes the following steps: S1. Mix 10 parts of alumina, 40 parts of iron oxide and 80 parts of zinc oxide in 200 parts of 10 wt% H2O2 aqueous solution, heat to 60℃, stir at 500 rpm for 4 h, filter, and dry to obtain the mixture. S2. Using 100 parts of 60 wt% ethanol aqueous solution as solvent, 5 parts of the above mixture are mixed with 5 parts of KH-570, heated and stirred at 80℃ and 300 r / min for 2 h, and the solvent is removed to obtain the modified mixture. S3. Under a nitrogen atmosphere, 50 parts of the modified mixture were dispersed in 200 parts of toluene, 0.5 parts of azobisisobutyronitrile were added, and the mixture was heated at 70°C for 6 h to remove the solvent, thereby obtaining the modified metal oxide. S4. According to the above mass proportions, the modified metal oxide is mixed with other components, 40 parts of water are added, the mixture is stirred evenly, and sprayed onto the surface of the reactor substrate. The mixture is sintered at 500°C for 40 min, cooled, and then removed to obtain a high-temperature resistant coating in the acetate reactor.

[0035] Comparative Example 1 A high-temperature resistant coating for an acetate reactor. The difference between this comparative example and Example 1 is that the amount of KH-570 in step S2 is replaced with 1 part, while the other steps and amounts are the same as in Example 1.

[0036] Comparative Example 2 A high-temperature resistant coating for an acetate reaction vessel. The difference between this comparative example and Example 1 is that in step S1, 40 parts of zinc oxide are first hydroxylated and then blended with 10 parts of aluminum and 20 parts of iron to form a mixture. Other steps and amounts are the same as in Example 1.

[0037] Test case The stability of the high-temperature resistant coatings in the acetate reaction vessels prepared in Examples 1-3 and Comparative Examples 1-2 was tested.

[0038] High temperature resistance test: The sample was placed in a muffle furnace and held at 250°C for 100 h. If no cracking or peeling was found on the coating surface, it indicates that the coating of the present invention has good heat resistance and is recorded as qualified.

[0039] Acid resistance test: Pour the same volume of 5 wt% sulfuric acid solution into the reaction vessel containing each sample as a corrosion solution, soak at room temperature for 200 h and observe. If there are no adverse phenomena such as bubbling and no substances are dissolved on the coating surface, it indicates that no corrosion has occurred and is recorded as qualified.

[0040] Corrosion resistance test: The test was conducted in accordance with GB / T 6458-86 "Neutral Salt Spray Test (NSS) for Metallic Coatings". The test temperature was 35±2℃ and the corrosion solution used was 5 wt% sodium chloride solution. The mass change rate of the specimen was measured after 240 h of corrosion.

[0041] The test results are shown in Table 1.

[0042] Table 1 Stability Test Results As shown in Table 1, the high-temperature resistant coatings in the acetate reactors prepared in Examples 1-3 of this invention exhibit excellent chemical stability and can be well applied in reactors. However, in Comparative Example 1, due to the reduction in the amount of KH-570, the modification of the metal oxide was insufficient, failing to form a dense, integrated network structure, resulting in an overall decrease in system stability. In Comparative Example 2, the partially hydroxylated metal oxide was replaced with elemental metal, resulting in insufficient surface hydroxyl groups, poor network structure construction, and oxidation of the elemental metal during high-temperature sintering, which damaged the smoothness of the coating, making the resulting product prone to cracking and significantly reducing its overall stability.

[0043] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0044] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A high temperature resistant coating in an acetate reactor characterized in that, The high-temperature-resistant coating in the acetate reaction kettle comprises the following components in mass fraction: Polymethylphenylsiloxane 100-120 parts Modified metal oxide 20-30 parts Alcohol ester twelve 2-4 parts Emulsifier 1-3 parts Polyethylene glycol 10-20 parts Leveling agent 1-3 parts The modified metal oxide is the product formed by grafting the blend of hydroxylated aluminum oxide, iron oxide and zinc oxide with KH-570 and then free radical polymerization.

2. The high temperature resistant coating in acetic acid ester reactor according to claim 1, characterized in that, The mass ratio of the aluminum oxide, iron oxide and zinc oxide is 1:(2-5):(2-8).

3. The high temperature resistant coating in acetic acid ester reactor according to claim 1, characterized in that, The particle size of the aluminum oxide, iron oxide and zinc oxide is 1-20 μm.

4. The high temperature resistant coating in acetic acid reactor according to claim 1, characterized in that, The polymethylphenylsiloxane is selected from polymethylphenylsiloxane with a molecular weight of 1500-3000.

5. The high temperature resistant coating in acetic acid reactor according to claim 1, wherein, The polyethylene glycol is selected from polyethylene glycol with a molecular weight of 200-1000.

6. The method of producing a high temperature resistant coating in an acetate reactor according to any one of claims 1 to 5, characterized in that, The preparation method of the high-temperature-resistant coating in the acetate reaction kettle comprises the following steps: S1, hydroxylate the aluminum oxide, iron oxide and zinc oxide to obtain a mixture; S2, blend the mixture with KH-570 and heat and stir to obtain a modified mixture; S3, disperse the modified mixture in toluene, add a catalyst and heat to obtain the modified metal oxide; S4, first blend the modified metal oxide with other components, then blend with water, spray on the surface of the reaction kettle substrate, high-temperature sintering, and then take out after cooling to obtain the high-temperature-resistant coating in the acetate reaction kettle.

7. The method of claim 6, wherein the coating is prepared by a process comprising: (a) applying a first coating to the surface of the substrate; (b) applying a second coating to the first coating; and (c) applying a third coating to the second coating. In step S2, the mass ratio of the mixture to KH-570 is 2:(1-2).

8. The method of claim 6, wherein the coating is prepared by a process comprising: (a) applying a first coating to the surface of the substrate; (b) applying a second coating to the first coating; and (c) applying a third coating to the second coating. In step S2, the heating temperature is 60-90℃.

9. The method of claim 6, wherein the coating is prepared by a process comprising: (a) applying a first coating to the surface of the substrate; (b) applying a second coating to the first coating; and (c) applying a third coating to the second coating. In step S3, the heating temperature is 60-80℃.

10. The method of claim 6, wherein the coating is prepared by a process comprising: (a) applying a first coating to the surface of the substrate; (b) applying a second coating to the first coating; and (c) applying a third coating to the second coating. In step S4, the sintering temperature is 500-600℃.

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