Composite coating and preparation method thereof

Abstract

The invention discloses a composite coating and a preparation method thereof.The composite coating comprises a substrate material, a polyamide-imide coating and a polyaryletherketone coating are sequentially arranged on the surface of the substrate material from inside to outside, the polyamide-imide coating is prepared from polyamide-imide containing carbonyl, and the polyaryletherketone coating is prepared from polyaryletherketone containing carbonyl. The preparation raw materials of the polyaryletherketone coating comprise soluble polyaryletherketone containing polar groups. The preparation method comprises the following steps: preparing the polyamide-imide coating and the polyaryletherketone coating, and sequentially spraying the polyamide-imide coating and the polyaryletherketone coating on the surface of the substrate material to form the composite coating. In the invention, under the combined action of the polyamide-imide coating and the polyaryletherketone coating, the composite coating has the advantages of high adhesive force, good high temperature resistance, low water absorption, low friction coefficient and the like, is a novel composite coating material with excellent performance, and has high use value and good application prospect; and the preparation method has the advantages of simple process, convenience in operation and the like, is suitable for large-scale preparation and is convenient for industrial application.

Description

Technical Field

[0001] This invention belongs to the field of functional polymer composite coating preparation technology, and relates to a composite coating and its preparation method. Background Technology

[0002] Polyamide-imide (PAI) is a high-performance polymer derived from polyimide. Its molecular chain contains both imide and amide structures, retaining the excellent heat resistance and mechanical properties of polyimide while overcoming its processing difficulties. It significantly increases tensile strength and impact resistance, and exhibits good creep resistance, leading to its widespread application in coatings, aerospace, and other industries. However, when PAI is used as a coating material on metal substrates, its high water absorption rate can cause numerous adverse effects on the metal material, hindering its widespread use. Furthermore, existing PAI synthesis methods primarily rely on the isocyanate method, which is technically challenging.

[0003] Polyaryletherketone (PEEK) possesses excellent high-temperature resistance, self-lubricating properties, corrosion resistance, flame retardancy, mechanical properties, electrical properties, hydrolysis resistance, and weather resistance, exhibiting extremely excellent comprehensive physical, mechanical, electrical, thermal, and chemical properties. It can be manufactured into various parts using traditional thermoplastic molding methods such as injection molding, extrusion, compression molding, coating, and machining, attracting widespread attention and importance from sample designers, molding and processing companies, and product manufacturers. Consequently, PEEK has found wide applications in petrochemical, transportation, electronics, medical and health, food processing, and aerospace industries. However, when existing PEEK is used as a coating material on metal substrates, its poor adhesion makes it difficult to stably adhere to the metal substrate surface. This not only makes composite structures prone to defects such as missing corners and porosity but also prevents it from serving as a base coating for reinforcing materials. Furthermore, existing PEEK has poor solubility in organic solvents, making it difficult to formulate coatings and adhesives using solvent methods, which is detrimental to industrial applications. Furthermore, PEEK coatings are generally applied using electrostatic spraying. Since the raw material is PEEK powder, additives such as polytetrafluoroethylene are usually added to make PEEK powder into a wear-resistant coating. However, after mechanical dispersion, the mixing of PEEK powder and additives is uneven, resulting in insufficient uniformity of additive dispersion in the coating after electrostatic spraying. Ultimately, this leads to deviations in coating performance at different locations, which is not conducive to preparing coating materials with excellent performance.

[0004] In addition, existing researchers have proposed a composite coating. First, a 3D mesh underlayer is prepared on the substrate by flame spraying. The underlayer includes PEEK. Then, a fluorinated coating is prepared on the underlayer by spraying or brushing. The fluorinated coating includes PAI and fluorocarbon resin. Finally, a discontinuous hard underlayer is formed on the substrate surface. The shortcomings are: (1) When PEEK is used as the underlayer, the adhesion between it and the substrate is poor, and it is difficult to achieve stable adhesion. In particular, when the application field is engineering machinery, it is difficult to adapt to the high load and long-term friction scenario; (2) When PAI is used as the outer layer, due to its large water absorption rate, it will bring many adverse effects to the metal material, making it difficult to promote its use; (3) The adhesion between PEEK and PAI is poor, and the two are difficult to combine effectively. In the end, it is difficult to form a composite coating with excellent performance. Although the use of fluorocarbon resin will increase the adhesion of the coating, it is difficult to adapt to the high temperature scenario when used in engineering machinery.

[0005] Therefore, obtaining a composite coating with high adhesion, good high temperature resistance, low water absorption and low coefficient of friction, as well as a simple and convenient preparation method to match it, will play an important role in promoting the widespread use of PEEK and PAI in many industries. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a composite coating with high adhesion, good high temperature resistance, low water absorption and low friction coefficient and its preparation method.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A composite coating includes a substrate material, the surface of which, from the inside out, consists of a polyamide-imide coating and a polyaryletherketone coating. The raw material for preparing the polyamide-imide coating includes a polyamide-imide containing a carbonyl group, and the raw material for preparing the polyaryletherketone coating includes a soluble polyaryletherketone containing a polar group.

[0008] In a further improvement of the above-mentioned composite coating, the substrate material is one of a metal substrate, a plastic substrate, a cement board, or a wood board; the metal substrate includes at least one of an iron plate, a steel plate, an aluminum plate, or a copper plate; the plastic substrate includes at least one of nylon or ABS board; the thickness of the polyamide-imide coating is 10 μm to 50 μm; and the thickness of the polyaryletherketone coating is 10 μm to 50 μm.

[0009] In a further improvement to the aforementioned composite coating, the carbonyl-containing polyamide-imide is prepared by an imidization reaction using 1,2,4-trimeric triglyceride acyl chloride and a carbonyl-containing diamine monomer as raw materials.

[0010] A further improvement to the above-mentioned composite coating is that the preparation method of the carbonyl-containing polyamide-imide includes the following steps: S11. Mix the carbonyl-containing diamine monomer with organic solvent A and stir to obtain solution A; wherein the organic solvent A is a polar organic solvent; S12. Add 1,2,4-triphenyltriacrylic acid chloride to solution A in batches and stir to obtain solution B; S13. Add the acid-binding agent to solution B to react and obtain solution C; S14. Add the imidizing reagent to solution C to react and obtain solution D; S15. Add solution D to deionized water, precipitate, crush, wash with water, filter, and dry to obtain polyamide imide containing carbonyl groups.

[0011] In a further improvement to the above-described composite coating, the method for preparing the carbonyl-containing polyamide-imide satisfies at least one of the following conditions (1.11) to (1.22): (1.11) In step S11, the carbonyl-containing diamine monomer is at least one of 4,4'-diaminobenzophenone and 4,4-diaminotriphenyl ketone; (1.12) In step S11, the polar organic solvent is at least one of N,N-dimethylacetamide and N-methylpyrrolidone; (1.13) The molar ratio of the 1,2,4-triphenyltriacrylic acid chloride to the carbonyl-containing diamine monomer is 1.02:1; (1.14) The mass ratio of the polar organic solvent to the 1,2,4-triphenyltriamic anhydride acyl chloride is 5 to 10:1; (1.15) In step S13, the acid-binding agent is triethylamine; the molar ratio of the acid-binding agent to the 1,2,4-triphenyltriacrylic anhydride chloride is 1:0.8 to 1.2; (1.16) In step S14, the imidizing agent is a mixture of acetic anhydride and triethylamine; the molar ratio of acetic anhydride to triethylamine is 0.5 to 2:1; (1.17) The molar ratio of the imidizing agent to the 1,2,4-triphenyltriacrylic anhydride acyl chloride is 0.125:0.052; (1.18) In step S11, the stirring is carried out at a temperature of 0 to 5°C; (1.19) In step S12, the stirring is carried out under a nitrogen atmosphere; the stirring time is 1h to 3h; (1.20) In step S13, the reaction is carried out at a temperature of 50℃ to 80℃; the reaction time is 12h to 24h. (1.21) In step S14, the reaction is carried out at a temperature of 50℃ to 80℃; the reaction time is 12h to 24h. (1.22) In step S15, the drying is carried out under vacuum conditions; the drying temperature is 100℃~150℃; and the drying time is 10h~24h.

[0012] In a further improvement to the above-mentioned composite coating, the raw materials for preparing the polyamide-imide coating also include: organic solvent B, defoamer A, and leveling agent A.

[0013] In a further improvement to the aforementioned composite coating, the raw materials for preparing the polyamide-imide coating are, by weight, the following: 5 to 50 parts of carbonyl-containing polyamide-imide Organic solvent B: 50-90 parts Defoamer A: 0.1 to 5 parts Leveling agent A: 0.1 to 3 parts.

[0014] In a further improvement of the above-mentioned composite coating, the organic solvent B is at least one selected from chloroform, 1,2-dichloroethane, tetrahydrofuran, cyclohexanone, N,N-dimethylformamide, N-methylpyrrolidone, and N,N-dimethylacetamide.

[0015] In a further improvement to the aforementioned composite coating, the defoamer A is Defom 5300, Defom 2700, or Efka. ® At least one of PB 2020 AN.

[0016] In a further improvement to the aforementioned composite coating, the leveling agent A is Efka. ® FL 3740 AN, Efka ® At least one of FL3287 and Levaslip 467.

[0017] In a further improvement of the aforementioned composite coating, the polar groups in the soluble polyaryletherketone containing polar groups include at least one of sulfonic acid groups, nitrate groups, and carboxyl groups.

[0018] In a further improvement to the aforementioned composite coating, the soluble polyarylether ketone containing polar groups is prepared by modifying soluble polyarylether ketone with an oxidizing acid.

[0019] A further improvement to the aforementioned composite coating is the preparation method of the soluble polyarylether ketone containing polar groups, which includes the following steps: S21. A soluble polyarylether ketone is mixed with an oxidizing acid to carry out a modification reaction, resulting in a mixed solution; S22. Add the mixture to ice water, filter, and dry to obtain mixture A; S23. Add mixture A to the alkaline solution, stir, filter, and obtain mixture B; S24. Wash mixture B until the pH of the washing solution is 5-6, then dry to obtain soluble polyarylether ketone containing polar groups.

[0020] In a further improvement to the above-mentioned composite coating, the method for preparing the soluble polyarylether ketone containing polar groups shall satisfy at least one of the following conditions (2.11) to (2.16): (2.11) In step S21, the mass ratio of the soluble polyarylether ketone to the oxidizing acid is 1:10 to 30; the oxidizing acid is at least one of concentrated nitric acid, concentrated sulfuric acid, and perchloric acid.

[0021] (2.12) In step S21, the soluble polyarylether ketone is prepared using twisted non-coplanar monomers and dihalogenated monomers as raw materials under the action of a catalyst, a dehydrating agent, and a reaction solvent; the molar ratio of the twisted non-coplanar monomer to the dihalogenated monomer is 1:0.8-1.5; the ratio of the sum of the masses of the twisted non-coplanar monomer and the dihalogenated monomer to the mass of the catalyst is 1:0.8-1.8; the twisted non-coplanar monomer is 1,4-cyclohexanediol, phenolphthalein, or 3,3-(2,4-diamino-6-hydroxyethyl)-6-hydroxyethyl. The reaction mixture comprises at least one of the following: 7-pteridindiyl)diphenol, phenolphthalein, 1,5-naphthyldiol, 2,5-tripterobenzenediol, 9,9'-bis(4-hydroxyphenyl)fluorene, 9,9-bis(3-isopropyl-4-hydroxyphenyl)fluorene, 3,3-bis(4-hydroxy-1-naphthyl)phthalide, 9,9'-bis(4-hydroxyphenyl)xanthine, and 9,9'-bis(3-nitro-4-hydroxyphenyl)xanthine; the dihalogen monomer is at least one of 4,4-difluorobenzophenone and 4,4-difluorotrifluorobenzophenone; the catalyst is an alkali metal carbonate; the alkali metal carbonate includes at least one of potassium carbonate and sodium carbonate; the dehydrating agent includes at least one of toluene and xylene; and the reaction solvent includes at least one of N-methylpyrrolidone, sulfolane, and diphenyl sulfone.

[0022] (2.13) In step S21, the modification reaction is carried out at a temperature of 60℃~120℃; the modification reaction time is 10h~20h.

[0023] (2.14) In step S22, the temperature of the ice water is 0℃~5℃; the drying temperature is 80℃~120℃; and the drying time is 24h.

[0024] (2.15) In step S23, the alkaline solution is a sodium hydroxide solution; the mass percentage of the alkaline solution is 30%; and the stirring time is 1h to 4h.

[0025] (2.16) In step S24, the drying temperature is 60℃~120℃; the drying time is 10h~20h.

[0026] The above-mentioned composite coating is further improved by including the following raw materials for preparing the polyaryletherketone coating: organic solvent C, defoamer B, leveling agent B, lubricant, dispersant, anti-settling agent, coupling agent, and pigment.

[0027] In a further improvement to the aforementioned composite coating, the raw materials for preparing the polyaryletherketone coating are, by weight, the following: 5 to 50 parts of soluble polyaryletherketone containing polar groups. Organic solvent C: 50-90 parts Defoamer B: 0.1 to 5 parts Leveling agent B: 0.1 to 3 parts 3 to 10 parts lubricant 1 to 10 parts of dispersant Anti-settling agent: 0.1 to 5 parts 0.1 to 2 parts of coupling agent, Pigment 0.1 to 4 parts.

[0028] In a further improvement of the above-mentioned composite coating, the organic solvent C is at least one selected from chloroform, 1,2-dichloroethane, tetrahydrofuran, N,N-dimethylacetamide, N,N-dimethylformamide, and N-methylpyrrolidone.

[0029] In a further improvement to the aforementioned composite coating, the defoamer B is Defom 5300, Defom 2700, or Efka. ® At least one of PB 2020 AN.

[0030] In a further improvement to the aforementioned composite coating, the leveling agent B is Efka. ® FL 3740 AN, Efka ® At least one of FL3287 and Levaslip 467.

[0031] In a further improvement of the aforementioned composite coating, the lubricant is at least one selected from polytetrafluoroethylene, polyvinylidene fluoride, molybdenum disulfide, graphite, and polyamide.

[0032] In a further improvement to the aforementioned composite coating, the dispersant is Efka. ®PU 4061 AN, Efka ® At least one of PA4401, Disponer 912, and Disponer 9850.

[0033] In a further improvement to the aforementioned composite coating, the anti-settling agent is BENTONE SD. ® -1. At least one of BENGEL 828 and BENGEL 958.

[0034] In a further improvement to the aforementioned composite coating, the coupling agent is a silane coupling agent KH550.

[0035] In a further improvement to the aforementioned composite coating, the pigment is at least one of carbon black, titanium dioxide, iron oxide red, chrome yellow, and lead chrome green.

[0036] As a general technical concept, the present invention also provides a method for preparing the above-mentioned composite coating, comprising the following steps: S31. Prepare polyamide-imide coatings from raw materials including polyamide-imide containing carbonyl groups; prepare polyaryletherketone coatings from raw materials including soluble polyaryletherketone containing polar groups. S32. Spray the polyamide-imide coating onto the surface of the substrate material and cure it to form a polyamide-imide coating on the surface of the substrate material; S33. Spray the polyaryletherketone coating onto the surface of the polyamide-imide coating and cure it to form a polyamide-imide coating on the surface of the polyamide-imide coating, thus completing the preparation of the composite coating.

[0037] The above-described preparation method is further improved in that the preparation method of the composite coating satisfies at least one of the following conditions (3.11) to (3.17): (3.11) In step S31, the preparation method of the polyamide-imide coating includes the following steps: placing raw materials, including polyamide-imide containing carbonyl groups, into a planetary ball mill for grinding to obtain a polyamide-imide coating; the process parameters during the ball milling process are: rotation speed of 100 rpm to 3000 rpm, revolution speed of 50 rpm to 2000 rpm, forward stirring time of 30 minutes to 60 minutes, reverse stirring time of 30 minutes to 60 minutes, and cycle of 2 to 4 times; the particle size of the grinding balls used in the planetary ball mill is 1 mm to 10 mm; the material of the grinding balls is at least one of zirconium oxide, agate, alumina, tungsten carbide, and stainless steel; the ratio of the mass of the grinding balls to the total mass of each raw material component is 0.1 to 2:1; the volume of the grinding balls and each raw material component accounts for 50% to 90% of the total volume of the grinding jar of the planetary ball mill.

[0038] (3.12) In step S31, the preparation method of the polyaryletherketone coating includes the following steps: placing raw materials, including soluble polyaryletherketone containing polar groups, into a planetary ball mill for grinding to obtain the polyaryletherketone coating; the process parameters during the ball milling process are: rotation speed of 100 rpm to 3000 rpm, revolution speed of 50 rpm to 2000 rpm, forward stirring time of 30 minutes to 60 minutes, reverse stirring time of 30 minutes to 60 minutes, and cycle of 2 to 4 times; the particle size of the grinding balls used in the planetary ball mill is 1 mm to 10 mm; the material of the grinding balls is at least one of zirconium oxide, agate, alumina, tungsten carbide, and stainless steel; the ratio of the mass of the grinding balls to the total mass of each raw material component is 0.1 to 2:1; the volume of the grinding balls and each raw material component accounts for 50% to 90% of the total volume of the grinding jar of the planetary ball mill.

[0039] (3.13) In step S32, before spraying the polyamide-imide coating onto the surface of the substrate material, the following treatment is also included: preheating the substrate material; the preheating treatment is carried out at a temperature of 80°C; the preheating treatment time is 30 min.

[0040] (3.14) In step S32, the polyamide-imide coating is sprayed onto the surface of the substrate material using an air spraying method.

[0041] (3.15) In step S32, the curing is carried out at a temperature of 200℃~320℃; the curing time is 10min~30min.

[0042] (3.16) In step S33, polyaryletherketone coating is sprayed onto the surface of polyamide-imide coating by air spraying.

[0043] (3.17) In step S33, the curing is carried out at a temperature of 200℃~320℃; the curing time is 30min~60min.

[0044] Compared with the prior art, the advantages of the present invention are as follows: (1) In view of the shortcomings of existing polyamide-imide coatings, polyaryletherketone coatings and their composite coatings, such as poor adhesion, high water absorption and weak bonding ability, the present invention creatively proposes a composite coating. The composite coating includes a base material, and on the surface of the base material, from the inside to the outside, there are polyamide-imide coating and polyaryletherketone coating. The raw material for preparing the polyamide-imide coating includes polyamide-imide containing carbonyl groups, and the raw material for preparing the polyaryletherketone coating includes soluble polyaryletherketone containing polar groups. In this invention, the polyamide-imide coating is prepared from polyamide-imide containing carbonyl groups. By introducing carbonyl groups, on the one hand, it can promote the formation of covalent bonds between the amide bonds in the polyamide-imide and the substrate material (such as a metal substrate), thereby enhancing the adhesion of the polyamide-imide to the substrate material. Therefore, when the polyamide-imide coating is used as the bottom layer, the adhesion stability of the composite coating to the substrate material can be significantly improved, enabling the composite coating to adapt to high-load long-term friction scenarios. On the other hand, it can also enhance the adhesion of the polyamide-imide to soluble polyaryletherketones (such as PEK-C), allowing the soluble polyaryletherketone to adhere firmly to the surface of the substrate material. Based on this, a polyaryletherketone coating prepared from soluble polyaryletherketones containing polar groups is attached to the polyamide-imide coating. By introducing polar groups into the soluble polyaryletherketone, the adhesion stability of the composite coating to the substrate material can be significantly improved. The polarity of the soluble polyaryletherketone (PAEK) molecular chain allows for the formation of chemical bonds between the polar groups and carbonyl groups, ensuring a strong bond between the polyamide-imide coating and the PAEK coating. This results in excellent structural stability for the composite coating. Furthermore, the PAEK coating contains carbonyl groups and polar groups, enabling the formation of numerous hydrogen bonds. The molecular chains also exhibit "like dissolves like" properties. Moreover, the PAEK coating, as a topcoat, has extremely low water absorption, providing low water absorption capacity for the composite coating. More importantly, the combined effect of the polyamide-imide and PAEK coatings results in a composite coating that combines high adhesion, good high-temperature resistance, low water absorption, and a low coefficient of friction. This makes it a high-performance novel composite coating material with high practical value and promising application prospects.

[0045] (2) In the composite coating of the present invention, by optimizing the thickness of the polyamide-imide coating to 10 μm to 50 μm and the thickness of the polyaryletherketone coating to 10 μm to 50 μm, a composite coating with strong adhesion and excellent impact resistance can be prepared on the surface of the substrate material. In particular, the composite coating has the best performance when the thickness of the polyamide-imide coating is 30 μm and the thickness of the polyaryletherketone coating is 30 μm. However, when the thickness of both the polyamide-imide coating and the polyaryletherketone coating is 50 μm, the coating thickness is too large, which will lead to peeling. Moreover, bubbling or delamination is likely to occur during curing. When the thickness of both the polyamide-imide coating and the polyaryletherketone coating is 10 μm, the coating thickness is too thin, which will result in poor impact test performance and easy wear off after long-term friction.

[0046] (3) In the composite coating of the present invention, the carbonyl-containing polyamide imide is prepared by imidization reaction of 1,2,4-triphenyltriatic anhydride acyl chloride and carbonyl-containing diamine monomer as raw materials. The molar ratio of 1,2,4-triphenyltriatic anhydride acyl chloride to carbonyl-containing diamine monomer is 1.02:1. By optimizing the molar ratio of 1,2,4-triphenyltriatic anhydride acyl chloride to carbonyl-containing diamine monomer, the polycondensation reaction can be promoted and the reaction of each material can be completed, thereby ensuring that the reaction is carried out completely. The PAI macromolecular chain is capped with anhydride groups to obtain a high molecular weight PAI product containing carbonyl groups. This results in carbonyl-containing polyamide-imide products with higher thermal stability, meeting practical performance requirements. However, when the amount of 1,2,4-trimeric anhydride acyl chloride is too low, the acyl chloride is easily hydrolyzed and deactivated, and it can also partially associate with the solvent, leading to a decrease in the amount of acyl chloride participating in the reaction. Consequently, the molecular weight of the prepared PAI resin decreases, making it difficult to meet application requirements. Conversely, when the amount of 1,2,4-trimeric anhydride acyl chloride is too high, the PAI macromolecule is prone to premature capping, further reducing the molecular weight of PAI.

[0047] (4) In the composite coating of the present invention, the raw materials for preparing the polyamide-imide coating also include defoamer A and leveling agent A. Defoamer A is a key component of oil-based coatings, which can effectively eliminate small bubbles in the coating and avoid the formation of a large number of micropores in the coating, thus affecting the performance. At the same time, under the combined action of leveling agent A, it can also further eliminate defects on the surface of the coating, such as effectively avoiding defects such as orange peel, fish eyes, and edge shrinkage. As a result, the polyamide-imide coating of the present invention can better adhere to the surface of the substrate material. At the same time, it can also promote and improve the adhesion effect of soluble polyaryletherketone coating on the polyamide-imide coating. Furthermore, the dosage of each raw material in the polyamide-imide coating is optimized. For example, by optimizing the polyamide-imide content, the viscosity of the oil-based coating can be improved, thereby enabling the oil-based coating of the present invention to be sprayed more evenly on the surface of the substrate material. In particular, an air spraying method can be used to evenly spray the oil-based coating onto the surface of the substrate material to form a suitable polyamide-imide coating. However, if the polyamide-imide content is too low, it will not easily flow onto the substrate surface after coating. If the polyamide-imide content is too high, it will not be effectively sprayed from the spray gun, affecting the coating effect.

[0048] (5) In the composite coating of the present invention, the raw materials for preparing the soluble polyaryletherketone coating also include defoamer B, leveling agent B, lubricant, dispersant, anti-settling agent, coupling agent, and pigment. Among them, defoamer B is a key component of oil-based coatings, which can effectively eliminate small bubbles in the coating and avoid the formation of a large number of micropores in the coating, thus affecting performance. Under the combined action of leveling agent B, it can also further eliminate defects on the coating surface, such as effectively avoiding defects such as orange peel, fish eyes, and edge shrinkage. Thus, the soluble polyaryletherketone coating of the present invention can better adhere to the surface of the polyamide-imide coating; lubricant Lubricants are important additives in coatings, serving to reduce the coefficient of friction. Furthermore, as dispersants, they promote the dispersion of lubricants in the coating, ensuring a more uniform distribution. As anti-settling agents, they prevent suspended lubricants from settling and causing coating stratification due to prolonged exposure. Adding coupling agents enhances the adhesion between composite coatings, allowing soluble polyaryletherketone coatings to adhere more firmly to the polyamide-imide coating surface. Finally, adding pigments improves the color of the coating, making it more aesthetically pleasing. Furthermore, by optimizing the amount of each raw material in the soluble polyaryletherketone coating, for example, by optimizing the content of soluble polyaryletherketone containing polar groups, the viscosity of the oil-based coating can be improved. This allows the oil-based coating of the present invention to be sprayed more uniformly onto the surface of the polyamide-imide coating. In particular, an air spraying method can be used to uniformly spray the oil-based coating onto the surface of the polyamide-imide coating to form a suitable soluble polyaryletherketone coating. However, if the content of soluble polyaryletherketone containing polar groups is too low, it will not easily flow onto the substrate surface after coating. If the content of soluble polyaryletherketone containing polar groups is too high, it cannot be effectively sprayed from the spray gun, affecting the coating effect. Similarly, regarding the content of lubricant, if its content is too low, it will not be able to reduce the coefficient of friction; while if the content is too high, sedimentation and agglomeration are likely to occur, or more dispersants and anti-settling agents may be needed, which will also bring other adverse effects.

[0049] (6) The present invention also provides a method for preparing a composite coating. First, a polyamide-imide coating is prepared from raw materials including a carbonyl polyamide-imide and a polyaryletherketone coating is prepared from raw materials including a soluble polyaryletherketone containing polar groups. Then, the polyaryletherketone coating is sprayed onto the surface of the polyamide-imide coating and cured to form a polyamide-imide coating on the surface of the polyamide-imide coating. Thus, a composite coating with high adhesion, good high temperature resistance, low water absorption and low friction coefficient is prepared. At the same time, the preparation method of the present invention also has the advantages of simple process and convenient operation, which is suitable for large-scale preparation and convenient for industrial application. Attached Figure Description

[0050] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0051] Figure 1 This is a schematic diagram of the composite coating structure in Embodiment 1 of the present invention.

[0052] Legend: 1. Substrate material; 2. Polyamide-imide coating; 3. Polyaryletherketone coating. Detailed Implementation

[0053] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of the present invention.

[0054] The "range" disclosed in this invention can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. This type of range definition can include or exclude endpoints; any endpoint can be independently included or excluded, and they can be arbitrarily combined, meaning any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60–120 and 80–110 are listed for specific parameters, it is understood that ranges of 60–110 and 80–120 are also expected. Furthermore, if minimum range values ​​of 1 and 2 are listed, and maximum range values ​​of 3, 4, and 5 are also listed, then the following ranges are all expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5. In this invention, unless otherwise stated, the numerical range "a–b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 and 5" have been listed in this article; "0 to 5" is just a shortened representation of these numerical combinations.

[0055] In this invention, terms such as "multiple" or "various" are used, unless otherwise specified, to refer to a quantity greater than or equal to 2. For example, "one or more" means one or more types.

[0056] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0057] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments. The term "implementation" as used herein has a similar understanding.

[0058] Those skilled in the art will understand that the order in which the steps are written in the various implementations or embodiments does not imply a strict execution order and does not constitute any limitation on the implementation process. The detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of the present invention can be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0059] In this invention, unless otherwise specified, A (such as B) means that B is a non-limiting example of A, and it is understood that A is not limited to B.

[0060] In this invention, "optionally," "optionally," and "optional" mean that they are optional, that is, they are selected from either "with" or "without." If multiple "options" appear in a technical solution, unless otherwise specified, and there are no contradictions or mutual constraints, then each "option" is independent.

[0061] Firstly, in view of the shortcomings of existing polyamide-imide coatings, polyaryletherketone coatings and their composite coatings, such as poor adhesion, high water absorption and weak bonding ability, this invention creatively proposes a composite coating. The composite coating includes a substrate material, on the surface of the substrate material, from the inside out, a polyamide-imide coating and a polyaryletherketone coating. The raw material for preparing the polyamide-imide coating includes polyamide-imide containing carbonyl groups, and the raw material for preparing the polyaryletherketone coating includes soluble polyaryletherketone containing polar groups. In this invention, the polyamide-imide coating is prepared from polyamide-imide containing carbonyl groups. By introducing carbonyl groups, on the one hand, it can promote the formation of covalent bonds between the amide bonds in the polyamide-imide and the substrate material (such as a metal substrate), thereby enhancing the adhesion of the polyamide-imide to the substrate material. Therefore, when the polyamide-imide coating is used as the bottom layer, the adhesion stability of the composite coating to the substrate material can be significantly improved, enabling the composite coating to adapt to high-load long-term friction scenarios. On the other hand, it can also enhance the adhesion of the polyamide-imide to soluble polyaryletherketones (such as PEK-C), allowing the soluble polyaryletherketone to adhere firmly to the surface of the substrate material. Based on this, a polyaryletherketone coating prepared from soluble polyaryletherketones containing polar groups is attached to the polyamide-imide coating. By introducing polar groups into the soluble polyaryletherketone, the adhesion stability of the composite coating to the substrate material can be significantly improved. The polarity of the soluble polyaryletherketone (PAEK) molecular chain allows for the formation of chemical bonds between the polar groups and carbonyl groups, ensuring a strong bond between the polyamide-imide coating and the PAEK coating. This results in excellent structural stability for the composite coating. Furthermore, the PAEK coating contains carbonyl groups and polar groups, enabling the formation of numerous hydrogen bonds. The molecular chains also exhibit "like dissolves like" properties. Moreover, the PAEK coating, as a topcoat, has extremely low water absorption, providing low water absorption capacity for the composite coating. More importantly, the combined effect of the polyamide-imide and PAEK coatings results in a composite coating that combines high adhesion, good high-temperature resistance, low water absorption, and a low coefficient of friction. This makes it a high-performance novel composite coating material with high practical value and promising application prospects.

[0062] In some embodiments, the substrate material used is one of the following: metal substrate, plastic substrate, cement board, and wood board, but is not limited to these.

[0063] Optionally, the metal substrate used includes at least one of iron plate, steel plate, aluminum plate or copper plate.

[0064] Optionally, the plastic substrate used includes at least one of nylon and ABS sheet.

[0065] Optionally, the thickness of the polyamide-imide coating used is 10 μm to 50 μm.

[0066] Optionally, the thickness of the polyaryletherketone coating used is 10 μm to 50 μm.

[0067] In some embodiments, the carbonyl-containing polyamide imide used is prepared by imidization reaction of 1,2,4-trimeric triglyceride acyl chloride and carbonyl-containing diamine monomer.

[0068] Optionally, the preparation method of the carbonyl-containing polyamide-imide includes the following steps: S11. Mix the carbonyl-containing diamine monomer with organic solvent A and stir to obtain solution A; wherein the organic solvent A is a polar organic solvent; S12. Add 1,2,4-triphenyltriacrylic acid chloride to solution A in batches and stir to obtain solution B; S13. Add the acid-binding agent to solution B to react and obtain solution C; S14. Add the imidizing reagent to solution C to react and obtain solution D; S15. Add solution D to deionized water, precipitate, crush, wash with water, filter, and dry to obtain polyamide imide containing carbonyl groups.

[0069] Optionally, the method for preparing the carbonyl-containing polyamide-imide used must satisfy at least one of the following conditions (1.11) to (1.22): (1.11) In step S11, the carbonyl-containing diamine monomer is at least one of 4,4'-diaminobenzophenone and 4,4-diaminotriphenyl ketone.

[0070] (1.12) In step S11, the polar organic solvent is at least one of N,N-dimethylacetamide and N-methylpyrrolidone.

[0071] (1.13) The molar ratio of the 1,2,4-triphenyltriacyl chloride to the carbonyl diamine monomer is 1.02:1.

[0072] (1.14) The mass ratio of the polar organic solvent to the 1,2,4-triphenyltrihydric anhydride acyl chloride is 5 to 10:1.

[0073] (1.15) In step S13, the acid-binding agent is triethylamine. The molar ratio of the acid-binding agent to the 1,2,4-triphenyltriatic anhydride acyl chloride is 1:0.8 to 1.2.

[0074] (1.16) In step S14, the imidizing agent is a mixture of acetic anhydride and triethylamine; the molar ratio of acetic anhydride to triethylamine is 0.5 to 2:1.

[0075] (1.17) The molar ratio of the imidizing agent to the 1,2,4-triphenyltrihydric anhydride acyl chloride is 0.125:0.052.

[0076] (1.18) In step S11, the stirring is carried out at a temperature of 0 to 5°C.

[0077] (1.19) In step S12, the stirring is carried out under a nitrogen atmosphere; the stirring time is 1h to 3h.

[0078] (1.20) In step S13, the reaction is carried out at a temperature of 50℃ to 80℃; the reaction time is 12h to 24h.

[0079] (1.21) In step S14, the reaction is carried out at a temperature of 50℃ to 80℃; the reaction time is 12h to 24h.

[0080] (1.22) In step S15, the drying is carried out under vacuum conditions; the drying temperature is 100℃~150℃; and the drying time is 10h~24h.

[0081] In some embodiments, the raw materials used to prepare the polyamide-imide coating further include: organic solvent B, defoamer A, and leveling agent A.

[0082] Optionally, the raw materials used to prepare the polyamide-imide coating are, by weight, as follows: 5 to 50 parts of carbonyl-containing polyamide-imide Organic solvent B: 50-90 parts Defoamer A: 0.1 to 5 parts Leveling agent A: 0.1 to 3 parts.

[0083] Optionally, the organic solvent B used is at least one of chloroform, 1,2-dichloroethane, tetrahydrofuran, cyclohexanone, N,N-dimethylformamide, N-methylpyrrolidone, and N,N-dimethylacetamide, but is not limited thereto.

[0084] Optionally, the defoamer A used is Haimings Defom 5300, Haimings Defom 2700, or Efka. ® At least one of PB 2020AN, but not limited to.

[0085] Optionally, the leveling agent A used is Efka. ® FL 3740 AN, Efka ® At least one of FL 3287 and Levaslip 467, but not limited to.

[0086] In some embodiments, the polar groups in the soluble polyaryletherketone containing polar groups include at least one of sulfonic acid group, nitrate group, and carboxyl group, for example, sulfonic acid group, nitrate group, and carboxyl group.

[0087] In some embodiments, the soluble polyaryletherketone containing polar groups is prepared by modifying soluble polyaryletherketone with oxidizing acid.

[0088] Optionally, the method for preparing soluble polyarylether ketones containing polar groups includes the following steps: S21. A soluble polyarylether ketone is mixed with an oxidizing acid to carry out a modification reaction, resulting in a mixed solution; S22. Add the mixture to ice water, filter, and dry to obtain mixture A; S23. Add mixture A to the alkaline solution, stir, filter, and obtain mixture B; S24. Wash mixture B until the pH of the washing solution is 5-6, then dry to obtain soluble polyarylether ketone containing polar groups.

[0089] Optionally, the method for preparing the soluble polyarylether ketone containing a polar group shall satisfy at least one of the following conditions (2.11) to (2.16): (2.11) In step S21, the mass ratio of the soluble polyarylether ketone to the oxidizing acid is 1:10 to 30; the oxidizing acid is at least one of concentrated nitric acid, concentrated sulfuric acid, and perchloric acid.

[0090] (2.12) In step S21, the soluble polyarylether ketone is prepared using twisted non-coplanar monomers and dihalogenated monomers as raw materials under the action of a catalyst, a dehydrating agent, and a reaction solvent; the molar ratio of the twisted non-coplanar monomer to the dihalogenated monomer is 1:0.8-1.5; the ratio of the sum of the masses of the twisted non-coplanar monomer and the dihalogenated monomer to the mass of the catalyst is 1:0.8-1.8; the twisted non-coplanar monomer is 1,4-cyclohexanediol, phenolphthalein, or 3,3-(2,4-diamino-6-hydroxyethyl)-6-hydroxyethyl. The reaction mixture comprises at least one of the following: 7-pteridindiyl)diphenol, phenolphthalein, 1,5-naphthyldiol, 2,5-tripterobenzenediol, 9,9'-bis(4-hydroxyphenyl)fluorene, 9,9-bis(3-isopropyl-4-hydroxyphenyl)fluorene, 3,3-bis(4-hydroxy-1-naphthyl)phthalide, 9,9'-bis(4-hydroxyphenyl)xanthine, and 9,9'-bis(3-nitro-4-hydroxyphenyl)xanthine; the dihalogen monomer is at least one of 4,4-difluorobenzophenone and 4,4-difluorotrifluorobenzophenone; the catalyst is an alkali metal carbonate; the alkali metal carbonate includes at least one of potassium carbonate and sodium carbonate; the dehydrating agent includes at least one of toluene and xylene; and the reaction solvent includes at least one of N-methylpyrrolidone, sulfolane, and diphenyl sulfone.

[0091] (2.13) In step S21, the modification reaction is carried out at a temperature of 60℃~120℃; the modification reaction time is 10h~20h.

[0092] (2.14) In step S22, the temperature of the ice water is 0℃~5℃; the drying temperature is 80℃~120℃; and the drying time is 24h.

[0093] (2.15) In step S23, the alkaline solution is a sodium hydroxide solution; the mass percentage of the alkaline solution is 30%; and the stirring time is 1h to 4h.

[0094] (2.16) In step S24, the drying temperature is 60℃~120℃; the drying time is 10h~20h.

[0095] In some embodiments, the raw materials used to prepare the polyaryletherketone coating further include: organic solvent C, defoamer B, leveling agent B, lubricant, dispersant, anti-settling agent, coupling agent, and pigment.

[0096] Optionally, the raw materials used to prepare the polyaryletherketone coating are, by weight, as follows: 5 to 50 parts of soluble polyaryletherketone containing polar groups. Organic solvent C: 50-90 parts Defoamer B: 0.1 to 5 parts Leveling agent B: 0.1 to 3 parts Lubricant 3 to 10 parts, 1 to 10 parts of dispersant Anti-settling agent 0.1 to 5 parts, 0.1 to 2 parts of coupling agent, Pigment 0.1 to 4 parts.

[0097] Optionally, the organic solvent C used is at least one of chloroform, 1,2-dichloroethane, tetrahydrofuran, N,N-dimethylacetamide, N,N-dimethylformamide, and N-methylpyrrolidone, but is not limited thereto.

[0098] Optionally, the defoamer B used is Haimings Defom 5300, Haimings Defom 2700, or Efka. ® At least one of PB 2020AN, but not limited to.

[0099] Optionally, the leveling agent B used is Efka. ® FL 3740 AN, Efka ® At least one of FL 3287 and Levaslip 467, but not limited to.

[0100] Optionally, the lubricant used may be at least one of polytetrafluoroethylene, polyvinylidene fluoride, molybdenum disulfide, graphite, and polyamide, but is not limited thereto.

[0101] Optionally, Efka is used as the dispersant. ® PU 4061 AN, Efka ® The device may contain at least one of PA 4401, Disponer 912, and Disponer 9850, but is not limited thereto.

[0102] Optionally, the anti-settling agent used is BENTONE SD. ® -1. At least one of BENGEL 828 and BENGEL 958, but not limited to.

[0103] Optionally, the coupling agent used is silane coupling agent KH550, but it is not limited to this.

[0104] Optionally, the pigment used may be at least one of carbon black, titanium dioxide, iron oxide red, chrome yellow, and lead chrome green, but is not limited to this.

[0105] Secondly, the present invention also provides a method for preparing the above-mentioned composite coating, comprising the following steps: S31. Prepare polyamide-imide coatings from raw materials including polyamide-imide containing carbonyl groups; prepare polyaryletherketone coatings from raw materials including soluble polyaryletherketone containing polar groups. S32. Spray the polyamide-imide coating onto the surface of the substrate material and cure it to form a polyamide-imide coating on the surface of the substrate material; S33. Spray the polyaryletherketone coating onto the surface of the polyamide-imide coating and cure it to form a polyamide-imide coating on the surface of the polyamide-imide coating, thus completing the preparation of the composite coating.

[0106] In some embodiments, the method for preparing the composite coating satisfies at least one of the following conditions (3.11) to (3.17): (3.11) In step S31, the preparation method of the polyamide-imide coating includes the following steps: placing raw materials, including polyamide-imide containing carbonyl groups, into a planetary ball mill for grinding to obtain a polyamide-imide coating; the process parameters during the ball milling process are: rotation speed of 100 rpm to 3000 rpm, revolution speed of 50 rpm to 2000 rpm, forward stirring time of 30 minutes to 60 minutes, reverse stirring time of 30 minutes to 60 minutes, and cycle of 2 to 4 times; the particle size of the grinding balls used in the planetary ball mill is 1 mm to 10 mm; the material of the grinding balls is at least one of zirconium oxide, agate, alumina, tungsten carbide, and stainless steel; the ratio of the mass of the grinding balls to the total mass of each raw material component is 0.1 to 2:1; the volume of the grinding balls and each raw material component accounts for 50% to 90% of the total volume of the grinding jar of the planetary ball mill.

[0107] (3.12) In step S31, the preparation method of the polyaryletherketone coating includes the following steps: placing raw materials, including soluble polyaryletherketone containing polar groups, into a planetary ball mill for grinding to obtain the polyaryletherketone coating; the process parameters during the ball milling process are: rotation speed of 100 rpm to 3000 rpm, revolution speed of 50 rpm to 2000 rpm, forward stirring time of 30 minutes to 60 minutes, reverse stirring time of 30 minutes to 60 minutes, and cycle of 2 to 4 times; the particle size of the grinding balls used in the planetary ball mill is 1 mm to 10 mm; the material of the grinding balls is at least one of zirconium oxide, agate, alumina, tungsten carbide, and stainless steel; the ratio of the mass of the grinding balls to the total mass of each raw material component is 0.1 to 2:1; the volume of the grinding balls and each raw material component accounts for 50% to 90% of the total volume of the grinding jar of the planetary ball mill.

[0108] (3.13) In step S32, before spraying the polyamide-imide coating onto the surface of the substrate material, the following treatment is also included: preheating the substrate material; the preheating treatment is carried out at a temperature of 80°C; the preheating treatment time is 30 min.

[0109] (3.14) In step S32, the polyamide-imide coating is sprayed onto the surface of the substrate material using an air spraying method.

[0110] (3.15) In step S32, the curing is carried out at a temperature of 200℃~320℃; the curing time is 10min~30min.

[0111] (3.16) In step S33, polyaryletherketone coating is sprayed onto the surface of polyamide-imide coating by air spraying.

[0112] (3.17) In step S33, the curing is carried out at a temperature of 200℃~320℃; the curing time is 30min~60min.

[0113] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0114] Example 1 like Figure 1 As shown, a composite coating includes a substrate material 1, on the surface of the substrate material 1, from the inside out, a polyamide-imide coating 2 and a polyarylether ketone coating 3, wherein the raw material for preparing the polyamide-imide coating 2 includes a polyamide-imide containing a carbonyl group, and the raw material for preparing the polyarylether ketone coating 3 includes a soluble polyarylether ketone containing a polar group.

[0115] In this embodiment, the substrate material 1 is a metal substrate, specifically a tin-plated steel plate, i.e., test-grade tinplate; the thickness of the polyamide-imide coating 2 is 30 μm; and the thickness of the polyaryletherketone coating 3 is 30 μm.

[0116] In this embodiment, the polyamide-imide coating comprises the following raw material components by weight: 14 parts of carbonyl-containing polyamide-imide Organic solvent B, 85.4 parts, Defoamer A 0.5 parts, Leveling agent A, 0.1 parts.

[0117] In this embodiment, the carbonyl-containing polyamide imide is prepared by imidization reaction using 1,2,4-tristyric anhydride chloride and carbonyl-containing diamine monomer as raw materials, including the following steps: S11. Under nitrogen protection, 0.05 mol of 4,4'-diaminobenzophenone (a diamine monomer containing a carbonyl group) is dissolved in N,N-dimethylacetamide (DMAc). The temperature is controlled at 0℃ and the mixture is stirred until the 4,4'-diaminobenzophenone is completely dissolved in the solvent to obtain solution A.

[0118] S12. Under nitrogen protection, 0.051 mol of 1,2,4-triphenyltriacrylic anhydride chloride was added to solution A in five portions and stirred at 0℃ for 1 h to obtain solution B.

[0119] S13. Under nitrogen protection, solution B is heated to 60°C, and 0.052 mol of acid-binding agent (triethylamine) is added to carry out the reaction for 12 hours to obtain solution C.

[0120] S14. Under nitrogen protection, 0.125 mol of imidizing reagent was added to solution C, and the temperature of the system was controlled at 70℃. The reaction was carried out for 12 h to obtain solution D. In this step, the imidizing reagent used was a mixture of acetic anhydride and triethylamine, wherein the molar ratio of acetic anhydride to triethylamine was 1:1.

[0121] S15. Add solution D to deionized water, precipitate, crush, wash with water, filter, and dry under vacuum at 150°C for 24 hours to obtain polyamide imide containing carbonyl groups.

[0122] In this embodiment, the chemical reaction formula for preparing polyamide-imide containing a carbonyl group is as follows: .

[0123] In this embodiment, the carbonyl-containing polyamide-imide has a structural formula in which n is 272. In other embodiments, n is 260, 261, 262, 263, 264, 265, 266, 267, 268, 269, 270, 271, 273, 274, 275, 276, 277, 278, 279, or 280, but is not limited to these.

[0124] In this embodiment, the organic solvent B used is N-methylpyrrolidone.

[0125] In this embodiment, the defoamer A used is Haimings Defom 5300.

[0126] In this embodiment, the leveling agent A used is Efka. ® FL 3287.

[0127] In this embodiment, the raw materials used to prepare the polyarylether ketone coating also include: organic solvent C, defoamer B, leveling agent B, lubricant, dispersant, anti-settling agent, coupling agent, and pigment, which are expressed in parts by weight as follows: 14 parts of soluble polyaryletherketone containing polar groups. Organic solvent C 66.8 parts, Defoamer B 0.1 parts, Leveling agent B, 3 parts 6 parts lubricant 1 part dispersant 5 parts anti-settling agent 0.1 parts coupling agent, 4 parts pigment.

[0128] In this embodiment, the polar group in the soluble polyarylether ketone containing polar groups is a sulfonic acid group (-SO3H).

[0129] In this embodiment, the soluble polyarylether ketone containing polar groups is prepared by modifying soluble polyarylether ketone with concentrated sulfuric acid, including the following steps: S21. Soluble polyaryletherketone is mixed with 98% concentrated sulfuric acid at a mass ratio of 1:20 and stirred at 100°C. The soluble polyaryletherketone is modified by concentrated sulfuric acid for 12 hours to obtain a mixed solution.

[0130] In step S21, optimizing the mass ratio of soluble polyarylether ketone to oxidizing acid to 1:10-30 is beneficial for modifying soluble polyarylether ketone. When the mass ratio is too low, the content of functional groups on the molecular chain is low, while when the mass ratio is too high, carbonization is likely to occur.

[0131] S22. Slowly add the mixture to ice water at 0°C, filter, and dry the filtered polymer at 100°C for 24 hours to obtain mixture A.

[0132] S23. Add mixture A to a 30% sodium hydroxide solution and stir at room temperature for 2 hours. Filter to obtain mixture B.

[0133] S24. Wash mixture B with deionized water until the pH of the washing solution is 6, and dry it at 100℃ for 15 hours to obtain soluble polyarylether ketone containing sulfonic acid groups.

[0134] In step S24, when the pH value of the cleaning solution is higher than 6, the carboxylic acid or sulfonic acid group does not have H and exists in ionic form, which does not meet the requirements; when the pH value of the cleaning solution is lower than 5, due to the high acidity, it is easy to react with the additives of the coating.

[0135] In this embodiment, the soluble polyarylether ketone used in step S21 is phenolphthalein-based polyarylether ketone, which is prepared from twisted non-coplanar monomers and dihalogen monomers under the action of a catalyst, a dehydrating agent, and a reaction solvent, including the following steps: Taking a 250mL polymerization reactor as an example, prepare the raw materials according to the following quantities: 20mmol of twisted non-coplanar monomer (phenolphthalein), 20mmol of 4,4-difluorobenzophenone, 28mmol of catalyst (potassium carbonate), 40mL of dehydrating agent (toluene), and 30mL of reaction solvent (sulfolane). Then, introduce nitrogen gas into the reaction system, introduce cooling water into the condenser, and slowly raise the temperature to 140℃ for azeotropic dehydration. Reflux for 4 hours, then raise the temperature to 200℃, during which time the dehydrating agent and water mixture are discharged, and the polymerization reaction begins. During this period, the viscosity of the polymerization system will gradually increase. Based on the system's behavior, add an appropriate amount of reaction solvent until the viscosity no longer increases. Add 40mL of solvent to dilute and stir rapidly. Slowly pour the polymer mixture into a dilute acid solution, precipitating a white fibrous polymer. After multiple cycles of washing with ethanol and water, soluble polyarylether ketone is obtained.

[0136] In this embodiment, the organic solvent C used is N-methylpyrrolidone.

[0137] In this embodiment, the defoamer B used is Haimings Defom 5300.

[0138] In this embodiment, the leveling agent B used is Levaslip 467.

[0139] In this embodiment, the lubricant used is polytetrafluoroethylene.

[0140] In this embodiment, the dispersant used is Efka. ® PU 4061 AN.

[0141] In this embodiment, the anti-settling agent used is BENTONE SD. ® -1.

[0142] In this embodiment, the coupling agent used is silane coupling agent KH550.

[0143] In this embodiment, carbon black is used as the pigment.

[0144] A method for preparing the composite coating described in this embodiment includes the following steps: S31. Preparation of polyamide-imide coatings and polyaryletherketone coatings Polyamide-imide coatings are made from raw materials including polyamide-imides containing carbonyl groups, specifically: Raw materials, including carbonyl-containing polyamide-imide, are ground in a planetary ball mill to obtain a polyamide-imide coating. The process parameters during ball milling are as follows: rotation speed of 100 rpm, revolution speed of 600 rpm, forward stirring time of 30 minutes, reverse stirring time of 30 minutes, and cycle of 3 times. The grinding beads used in the planetary ball mill have particle sizes of 1 mm, 5 mm, and 10 mm. The grinding beads are made of zirconium oxide. The mass ratio of the grinding beads to the total mass of each raw material component is 1:1. The volume of the grinding beads and each raw material component accounts for 70% of the total volume of the grinding jar of the planetary ball mill.

[0145] A polyaryletherketone coating is prepared from raw materials including soluble polyaryletherketones containing polar groups. Specifically, the raw materials, including soluble polyaryletherketones containing polar groups, are placed in a planetary ball mill for grinding to obtain the polyaryletherketone coating. The process parameters during the ball milling process are as follows: The rotation speed is 100 rpm, the revolution speed is 600 rpm, the forward stirring time is 30 minutes, the reverse stirring time is 30 minutes, and the cycle is 3 times. In the planetary ball mill, the particle size of the grinding balls used is 1 mm, 5 mm and 10 mm respectively. The material of the grinding balls is zirconium oxide. The mass ratio of the grinding balls to the total mass of each raw material component is 1:1. The volume of the grinding balls and each raw material component accounts for 70% of the total volume of the grinding jar of the planetary ball mill.

[0146] S32. Apply polyamide-imide coating to the surface of the substrate material (tin-plated steel plate) using air spraying method, and cure at a temperature of 270℃ for 30 minutes to form a polyamide-imide coating on the surface of the substrate material.

[0147] In step 32, before spraying, the tin-plated steel sheet is preheated, specifically heated at 80°C for 30 minutes. Preheating the tin-plated steel sheet helps to improve the adhesion between the coating and the substrate.

[0148] S33. Apply polyaryletherketone coating to the surface of polyamide-imide coating using air spraying method, and cure at 270℃ for 30 minutes to form a polyamide-imide coating on the surface of the polyamide-imide coating, thus completing the preparation of the composite coating.

[0149] Example 2 A composite coating is basically the same as that in Example 1, except that the polar group in the soluble polyarylether ketone containing polar groups is a nitrate group (-NO2).

[0150] In Example 2, the preparation method of soluble polyaryletherketone containing polar groups is basically the same as that in Example 1, except that concentrated nitric acid is used instead of concentrated sulfuric acid, wherein the concentration of concentrated nitric acid is 68%.

[0151] Example 3 A composite coating is basically the same as in Example 1, except that the polar group in the soluble polyarylether ketone containing polar groups is a carboxyl group (-COOH).

[0152] In Example 3, the preparation method of soluble polyarylether ketone containing polar groups is basically the same as that in Example 1, except that perchloric acid is used instead of concentrated sulfuric acid.

[0153] Example 4 A composite coating is basically the same as in Example 1, except that in the preparation method of the carbonyl-containing polyamide-imide, the carbonyl-containing diamine monomer is 4,4-diaminotriphenyl dimethyl ketone.

[0154] In this embodiment, the chemical reaction formula for preparing polyamide-imide containing a carbonyl group is as follows: .

[0155] In this embodiment, the carbonyl-containing polyamide-imide has a structural formula in which n is 272. In other embodiments, n is 260, 261, 262, 263, 264, 265, 266, 267, 268, 269, 270, 271, 273, 274, 275, 276, 277, 278, 279, or 280, but is not limited to these.

[0156] Example 5 A composite coating is basically the same as that in Example 4, except that the polar group in the soluble polyarylether ketone containing polar groups is a nitrate group (-NO2).

[0157] In Example 5, the preparation method of soluble polyarylether ketone containing polar groups is basically the same as that in Example 4, except that concentrated nitric acid is used instead of concentrated sulfuric acid, wherein the concentration of concentrated nitric acid is 68%.

[0158] Example 6 A composite coating is basically the same as in Example 4, except that the polar group in the soluble polyarylether ketone containing polar groups is a carboxyl group (-COOH).

[0159] In Example 6, the preparation method of soluble polyarylether ketone containing polar groups is basically the same as that in Example 4, except that perchloric acid is used instead of concentrated sulfuric acid.

[0160] Comparative Example 1 A composite coating is basically the same as in Example 1, except that: a commercially available polyamide-imide (without carbonyl) is used instead of a polyamide-imide containing carbonyl, and a commercially available phenolphthalein-type polyarylether ketone is used instead of a soluble polyarylether ketone containing polar groups.

[0161] Comparative Example 2 A composite coating is basically the same as that in Example 1, except that a commercially available phenolphthalein-type polyarylether ketone is used instead of a soluble polyarylether ketone containing polar groups.

[0162] Comparative Example 3 A composite coating is basically the same as that in Example 4, except that a commercially available phenolphthalein-type polyaryletherketone is used instead of a soluble polyaryletherketone containing polar groups.

[0163] The composite coatings in Examples 1-6 and Comparative Examples 1-3 were tested, as follows: 1. Adhesion by the circular scratch test: The test was conducted according to the test method provided in GB / T 1720-2020, and the results are shown in Table 1.

[0164] 2. Impact resistance: The test was conducted according to the test method provided in GB / T 1732-2020, and the results are shown in Table 1.

[0165] 3. Flexibility: The test was conducted according to the test method provided in Clause 4 of GB / T 1731-2020, and the results are shown in Table 1.

[0166] 4. Pencil hardness: The test was conducted according to the test method provided in GB / T 6739-2022, and the results are shown in Table 1.

[0167] Table 1. Performance comparison of composite coatings in Examples 1-6 and Comparative Examples 1-3

[0168] As shown in Table 1, compared with conventional composite coatings, the polyamide-imide coating used in Examples 1-6 of this invention is prepared from polyamide-imide containing carbonyl groups, which has the advantage of strong adhesion to the substrate material. Therefore, the polyamide-imide coating can be stably attached to the surface of the substrate material. Furthermore, the raw materials for preparing the polyaryletherketone coating include soluble polyaryletherketone containing polar groups, which has the advantages of strong adhesion to the polyamide-imide coating and low water absorption. Therefore, the polyaryletherketone coating can be stably attached to the surface of the polyamide-imide coating to form a composite coating with high adhesion, good high temperature resistance, low water absorption and low coefficient of friction. As a new type of composite coating material with excellent performance, it can be adapted to the field of engineering machinery, especially to high temperature scenarios, with high use value and good application prospects.

[0169] The effects of different thicknesses of polyamide-imide coatings and polyaryletherketone coatings, as well as different curing times, on the performance of the composite coating were investigated, as follows: Example 7 A composite coating is basically the same as that in Example 1, except that in Example 7, the thickness of the polyamide-imide coating is 10 μm and the thickness of the polyaryletherketone coating is 10 μm.

[0170] In Example 7, the preparation method of the composite coating is basically the same as that in Example 1, except that in Example 7, the curing temperature is 270°C and the curing time is 10 min during the preparation of the polyamide-imide coating, and the curing temperature is 270°C and the curing time is 10 min during the preparation of the polyaryletherketone coating.

[0171] Example 8 A composite coating is basically the same as that in Example 1, except that in Example 8, the thickness of the polyamide-imide coating is 30 μm and the thickness of the polyaryletherketone coating is 30 μm.

[0172] In Example 8, the preparation method of the composite coating is basically the same as that in Example 1, except that in Example 8, the curing temperature is 270°C and the curing time is 10 min during the preparation of the polyamide-imide coating, and the curing temperature is 270°C and the curing time is 10 min during the preparation of the polyaryletherketone coating.

[0173] Example 9 A composite coating is basically the same as that in Example 1, except that in Example 9, the thickness of the polyamide-imide coating is 50 μm and the thickness of the polyaryletherketone coating is 50 μm.

[0174] In Example 9, the preparation method of the composite coating is basically the same as that in Example 1, except that in Example 9, the curing temperature is 270°C and the curing time is 10 min during the preparation of the polyamide-imide coating, and the curing temperature is 270°C and the curing time is 10 min during the preparation of the polyaryletherketone coating.

[0175] Example 10 A composite coating is basically the same as that in Example 1, except that in Example 10, the thickness of the polyamide-imide coating is 10 μm and the thickness of the polyaryletherketone coating is 10 μm.

[0176] In Example 10, the preparation method of the composite coating is basically the same as that in Example 1, except that in Example 10, the curing temperature is 270°C and the curing time is 30 min during the preparation of the polyamide-imide coating, and the curing temperature is 270°C and the curing time is 30 min during the preparation of the polyaryletherketone coating.

[0177] Example 11 A composite coating is basically the same as that in Example 1, except that in Example 11, the thickness of the polyamide-imide coating is 50 μm and the thickness of the polyaryletherketone coating is 50 μm.

[0178] In Example 11, the preparation method of the composite coating is basically the same as that in Example 1, except that in Example 11, the curing temperature is 270°C and the curing time is 30 min during the preparation of the polyamide-imide coating, and the curing temperature is 270°C and the curing time is 30 min during the preparation of the polyaryletherketone coating.

[0179] Example 12 A composite coating is basically the same as that in Example 1, except that in Example 12, the thickness of the polyamide-imide coating is 10 μm and the thickness of the polyaryletherketone coating is 10 μm.

[0180] In Example 12, the preparation method of the composite coating is basically the same as that in Example 1, except that in Example 12, the curing temperature is 270°C and the curing time is 60 min during the preparation of the polyamide-imide coating, and the curing temperature is 270°C and the curing time is 60 min during the preparation of the polyaryletherketone coating.

[0181] Example 13 A composite coating is basically the same as that in Example 1, except that in Example 13, the thickness of the polyamide-imide coating is 30 μm and the thickness of the polyaryletherketone coating is 30 μm.

[0182] In Example 13, the preparation method of the composite coating is basically the same as that in Example 1, except that in Example 13, the curing temperature is 270°C and the curing time is 60 min during the preparation of the polyamide-imide coating, and the curing temperature is 270°C and the curing time is 60 min during the preparation of the polyaryletherketone coating.

[0183] Example 14 A composite coating is basically the same as that in Example 1, except that in Example 14, the thickness of the polyamide-imide coating is 50 μm and the thickness of the polyaryletherketone coating is 50 μm.

[0184] In Example 14, the preparation method of the composite coating is basically the same as that in Example 1, except that in Example 14, the curing temperature is 270°C and the curing time is 60 min during the preparation of the polyamide-imide coating, and the curing temperature is 270°C and the curing time is 60 min during the preparation of the polyaryletherketone coating.

[0185] The composite coatings in Examples 7-14 were subjected to abrasion resistance and scratch resistance tests, and the results are shown in Table 2.

[0186] Table 2. Effects of different thicknesses of polyamide-imide coatings and polyaryletherketone coatings, and different curing times on the performance of composite coatings.

[0187] As shown in Table 2, by optimizing the thickness of the polyamide-imide coating to 10 μm–50 μm and the polyaryletherketone coating to 10 μm–50 μm, a composite coating with strong adhesion and excellent impact resistance can be prepared on the substrate surface. In particular, the composite coating exhibits the best performance when both the polyamide-imide coating and the polyaryletherketone coating are 30 μm thick. However, when both the polyamide-imide coating and the polyaryletherketone coating are 50 μm thick, peeling occurs due to the excessive coating thickness, and blistering or delamination is likely to occur during curing. Conversely, when both the polyamide-imide coating and the polyaryletherketone coating are 10 μm thick, the coating is too thin, resulting in poor impact test performance and easy wear away during long-term friction.

[0188] Meanwhile, as shown in Table 2, in this invention, optimizing the curing time of the polyamide-imide coating to 10-30 minutes and the curing time of the polyaryletherketone coating to 30-60 minutes is beneficial to improving the curing effect of the coatings. In particular, when the curing time of both the polyamide-imide coating and the polyaryletherketone coating is 30 minutes, the curing efficiency can be effectively improved while ensuring complete curing. However, when the curing time is less than 10 minutes, the performance of the composite coating shows a precipitous decline, which is because the coating is not completely cured and its performance does not meet the standards.

[0189] As can be seen from the above results, compared with existing conventional composite coatings, the present invention includes a substrate material, on which a polyamide-imide coating and a polyaryletherketone coating are formed sequentially from the inside out on the surface of the substrate material. The raw materials for preparing the polyamide-imide coating include polyamide-imide containing carbonyl groups, and the raw materials for preparing the polyaryletherketone coating include soluble polyaryletherketone containing polar groups. Under the combined action of the polyamide-imide coating and the polyaryletherketone coating, the composite coating has the advantages of high adhesion, good high temperature resistance, low water absorption and low coefficient of friction. It is a novel composite coating material with excellent performance, high use value and good application prospects.

[0190] The above embodiments are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A composite coating, characterized in that, The substrate material includes a polyamide-imide coating and a polyaryletherketone coating, which are arranged from the inside out. The polyamide-imide coating is prepared from polyamide-imide containing carbonyl groups, and the polyaryletherketone coating is prepared from soluble polyaryletherketone containing polar groups.

2. The composite coating according to claim 1, characterized in that, The substrate material is one of a metal substrate, a plastic substrate, a cement board, or a wood board; the metal substrate includes at least one of an iron plate, a steel plate, an aluminum plate, or a copper plate; the plastic substrate includes at least one of nylon or ABS board; the thickness of the polyamide-imide coating is 10 μm to 50 μm; and the thickness of the polyaryletherketone coating is 10 μm to 50 μm.

3. The composite coating according to claim 1 or 2, characterized in that, The carbonyl-containing polyamide-imide is prepared by imidization reaction using 1,2,4-trimeric triglyceride acyl chloride and a carbonyl-containing diamine monomer as raw materials; the preparation method of the carbonyl-containing polyamide-imide includes the following steps: S11. Mix the carbonyl-containing diamine monomer with organic solvent A and stir to obtain solution A; wherein the organic solvent A is a polar organic solvent; S12. Add 1,2,4-triphenyltriacrylic acid chloride to solution A in batches and stir to obtain solution B; S13. Add the acid-binding agent to solution B to react and obtain solution C; S14. Add the imidizing reagent to solution C to react and obtain solution D; S15. Add solution D to deionized water, precipitate, crush, wash with water, filter, and dry to obtain polyamide imide containing carbonyl groups.

4. The composite coating according to claim 3, characterized in that, The method for preparing the carbonyl-containing polyamide-imide satisfies at least one of the following conditions (1.11) to (1.22): (1.11) In step S11, the carbonyl-containing diamine monomer is at least one of 4,4'-diaminobenzophenone and 4,4-diaminotriphenyl ketone; (1.12) In step S11, the polar organic solvent is at least one of N,N-dimethylacetamide and N-methylpyrrolidone; (1.13) The molar ratio of the 1,2,4-triphenyltriacrylic acid chloride to the carbonyl-containing diamine monomer is 1.02:1; (1.14) The mass ratio of the polar organic solvent to the 1,2,4-triphenyltriamic anhydride acyl chloride is 5 to 10:1; (1.15) In step S13, the acid-binding agent is triethylamine; the molar ratio of the acid-binding agent to the 1,2,4-triphenyltriacrylic anhydride chloride is 1:0.8 to 1.2; (1.16) In step S14, the imidizing agent is a mixture of acetic anhydride and triethylamine; the molar ratio of acetic anhydride to triethylamine is 0.5 to 2:1; (1.17) The molar ratio of the imidizing agent to the 1,2,4-triphenyltriacrylic anhydride acyl chloride is 0.125:0.052; (1.18) In step S11, the stirring is carried out at a temperature of 0 to 5°C; (1.19) In step S12, the stirring is carried out under a nitrogen atmosphere; the stirring time is 1h to 3h; (1.20) In step S13, the reaction is carried out at a temperature of 50℃ to 80℃; the reaction time is 12h to 24h. (1.21) In step S14, the reaction is carried out at a temperature of 50℃ to 80℃; the reaction time is 12h to 24h. (1.22) In step S15, the drying is carried out under vacuum conditions; the drying temperature is 100℃~150℃; and the drying time is 10h~24h.

5. The composite coating according to claim 4, characterized in that, The raw materials for preparing the polyamide-imide coating also include: organic solvent B, defoamer A, and leveling agent A; the raw materials for preparing the polyamide-imide coating are, by weight, as follows: 5 to 50 parts of carbonyl-containing polyamide-imide Organic solvent B: 50-90 parts Defoamer A: 0.1 to 5 parts Leveling agent A: 0.1 to 3 parts; The organic solvent B is at least one of chloroform, 1,2-dichloroethane, tetrahydrofuran, cyclohexanone, N,N-dimethylformamide, N-methylpyrrolidone, and N,N-dimethylacetamide; The defoamer A is Haimings Defom 5300, Haimings Defom 2700, or Efka. ® At least one of PB 2020 AN; The leveling agent A is Efka. ® FL 3740 AN, Efka ® At least one of FL 3287 and Levaslip 467.

6. The composite coating according to claim 1 or 2, characterized in that, The polar groups in the soluble polyaryletherketone containing polar groups include at least one of sulfonic acid groups, nitrate groups, and carboxyl groups; The soluble polyarylether ketone containing polar groups is prepared by modifying soluble polyarylether ketone with oxidizing acid; the preparation method of the soluble polyarylether ketone containing polar groups includes the following steps: S21. A soluble polyarylether ketone is mixed with an oxidizing acid to carry out a modification reaction, resulting in a mixed solution; S22. Add the mixture to ice water, filter, and dry to obtain mixture A; S23. Add mixture A to the alkaline solution, stir, filter, and obtain mixture B; S24. Wash mixture B until the pH of the washing solution is 5-6, then dry to obtain soluble polyarylether ketone containing polar groups.

7. The composite coating according to claim 6, characterized in that, The method for preparing the soluble polyarylether ketone containing polar groups shall satisfy at least one of the following conditions (2.11) to (2.16): (2.11) In step S21, the mass ratio of the soluble polyarylether ketone to the oxidizing acid is 1:10 to 30; the oxidizing acid is at least one of concentrated nitric acid, concentrated sulfuric acid, and perchloric acid; (2.12) In step S21, the soluble polyarylether ketone is prepared using twisted non-coplanar monomers and dihalogenated monomers as raw materials under the action of a catalyst, a dehydrating agent, and a reaction solvent; the molar ratio of the twisted non-coplanar monomer to the dihalogenated monomer is 1:0.8-1.5; the ratio of the sum of the masses of the twisted non-coplanar monomer and the dihalogenated monomer to the mass of the catalyst is 1:0.8-1.8; the twisted non-coplanar monomer is 1,4-cyclohexanediethanol, phenolphthalein, 3,3-(2 ... The reaction mixture comprises at least one of the following: 4-diamino-6,7-pteridindiyl)diphenol, phenolphthalein, 1,5-naphthyldiol, 2,5-tripterobenzenediol, 9,9'-bis(4-hydroxyphenyl)fluorene, 9,9-bis(3-isopropyl-4-hydroxyphenyl)fluorene, 3,3-bis(4-hydroxy-1-naphthyl)phthalide, 9,9'-bis(4-hydroxyphenyl)xanthine, and 9,9'-bis(3-nitro-4-hydroxyphenyl)xanthine; the dihalogen monomer is at least one of 4,4-difluorobenzophenone and 4,4-difluorotribenzophenone; the catalyst is an alkali metal carbonate; the alkali metal carbonate includes at least one of potassium carbonate and sodium carbonate; the dehydrating agent includes at least one of toluene and xylene; and the reaction solvent includes at least one of N-methylpyrrolidone, sulfolane, and diphenyl sulfone. (2.13) In step S21, the modification reaction is carried out at a temperature of 60℃~120℃; the modification reaction time is 10h~20h; (2.14) In step S22, the temperature of the ice water is 0℃~5℃; the drying temperature is 80℃~120℃; and the drying time is 24h. (2.15) In step S23, the alkaline solution is a sodium hydroxide solution; the mass percentage of the alkaline solution is 30%; and the stirring time is 1h to 4h. (2.16) In step S24, the drying temperature is 60℃~120℃; the drying time is 10h~20h.

8. The composite coating according to claim 7, characterized in that, The raw materials for preparing the polyaryletherketone coating also include: organic solvent C, defoamer B, leveling agent B, lubricant, dispersant, anti-settling agent, coupling agent, and pigment; the raw materials for preparing the polyaryletherketone coating are, by weight: 5 to 50 parts of soluble polyaryletherketone containing polar groups. Organic solvent C: 50-90 parts Defoamer B: 0.1 to 5 parts Leveling agent B: 0.1 to 3 parts 3 to 10 parts lubricant 1 to 10 parts of dispersant Anti-settling agent: 0.1 to 5 parts 0.1 to 2 parts of coupling agent, Pigment 0.1 to 4 parts; The organic solvent C is at least one of chloroform, 1,2-dichloroethane, tetrahydrofuran, N,N-dimethylacetamide, N,N-dimethylformamide, and N-methylpyrrolidone; The defoamer B is Haimingsi Defom 5300, Haimingsi Defom 2700, or Efka. ® At least one of PB 2020 AN; The leveling agent B is Efka. ® FL 3740 AN, Efka ® At least one of FL 3287 and Levaslip 467; The lubricant is at least one of polytetrafluoroethylene, polyvinylidene fluoride, molybdenum disulfide, graphite, and polyamide. The dispersant is Efka. ® PU 4061 AN, Efka ® At least one of PA 4401, Disponer 912, and Disponer 9850; The anti-settling agent is BENTONE SD. ® -1. At least one of BENGEL 828 and BENGEL 958; The coupling agent is silane coupling agent KH550; The pigment is at least one of carbon black, titanium dioxide, iron oxide red, chrome yellow, and lead chrome green.

9. A method for preparing a composite coating as described in any one of claims 1 to 8, characterized in that, Includes the following steps: S31. Prepare polyamide-imide coatings from raw materials including polyamide-imide containing carbonyl groups; prepare polyaryletherketone coatings from raw materials including soluble polyaryletherketone containing polar groups. S32. Spray the polyamide-imide coating onto the surface of the substrate material and cure it to form a polyamide-imide coating on the surface of the substrate material; S33. Spray the polyaryletherketone coating onto the surface of the polyamide-imide coating and cure it to form a polyamide-imide coating on the surface of the polyamide-imide coating, thus completing the preparation of the composite coating.

10. The preparation method according to claim 9, characterized in that, The method for preparing the composite coating shall satisfy at least one of the following conditions (3.11) to (3.17): (3.11) In step S31, the preparation method of the polyamide-imide coating includes the following steps: placing raw materials, including polyamide-imide containing carbonyl groups, into a planetary ball mill for grinding to obtain a polyamide-imide coating; the process parameters during the ball milling process are: rotation speed of 100 rpm to 3000 rpm, revolution speed of 50 rpm to 2000 rpm, forward stirring time of 30 minutes to 60 minutes, reverse stirring time of 30 minutes to 60 minutes, and cycle of 2 to 4 times; the particle size of the grinding balls used in the planetary ball mill is 1 mm to 10 mm; the material of the grinding balls is at least one of zirconium oxide, agate, alumina, tungsten carbide, and stainless steel; the ratio of the mass of the grinding balls to the total mass of each raw material component is 0.1 to 2:1; the volume of the grinding balls and each raw material component accounts for 50% to 90% of the total volume of the grinding jar of the planetary ball mill; (3.12) In step S31, the preparation method of the polyaryletherketone coating includes the following steps: placing raw materials, including soluble polyaryletherketone containing polar groups, into a planetary ball mill for grinding to obtain the polyaryletherketone coating; the process parameters during the ball milling process are: rotation speed of 100 rpm to 3000 rpm, revolution speed of 50 rpm to 2000 rpm, forward stirring time of 30 minutes to 60 minutes, reverse stirring time of 30 minutes to 60 minutes, and cycle of 2 to 4 times; the particle size of the grinding balls used in the planetary ball mill is 1 mm to 10 mm; the material of the grinding balls is at least one of zirconium oxide, agate, alumina, tungsten carbide, and stainless steel; the ratio of the mass of the grinding balls to the total mass of each raw material component is 0.1 to 2:1; the volume of the grinding balls and each raw material component accounts for 50% to 90% of the total volume of the grinding jar of the planetary ball mill; (3.13) In step S32, before spraying the polyamide-imide coating onto the surface of the substrate material, the following treatment is also included: preheating the substrate material; the preheating treatment is carried out at a temperature of 80°C; the preheating treatment time is 30 min; (3.14) In step S32, the polyamide-imide coating is sprayed onto the surface of the substrate material using an air spraying method; (3.15) In step S32, the curing is carried out at a temperature of 200℃~320℃; the curing time is 10min~30min; (3.16) In step S33, the polyaryletherketone coating is sprayed onto the surface of the polyamide-imide coating using an air spraying method; (3.17) In step S33, the curing is carried out at a temperature of 200℃~320℃; the curing time is 30min~60min.

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