A steel casting coated with a high-strength and high-toughness weather-resistant paint and a method for preparing the same

Abstract

The application relates to the technical field of paint, and discloses a steel casting coated with high-strength high-toughness weather-resistant paint and a preparation method thereof; the steel casting coated with high-strength high-toughness weather-resistant paint comprises the following operation steps: uniformly mixing epoxy resin, modified polyimide, alkylated lignin composite material, polyamide and a solvent to obtain high-strength high-toughness weather-resistant paint; a basic steel casting is cleaned in acetone, washed with water, dried, coated with the high-strength high-toughness weather-resistant paint, and cured at a high temperature to obtain the steel casting; in the scheme, a benzoyl ketone group structure is introduced into lignin and into polyimide to synergistically improve the mechanical properties, but the strength is too high and the weather resistance is limited, so an alkane structure is further introduced into the obtained amino benzoyl ketone group lignin as a filler to enhance the toughness and weather resistance of the coating.

Description

Technical Field

[0001] This invention relates to the field of coating technology, specifically to a steel casting coated with a high-strength, high-toughness, and weather-resistant coating, and its preparation method. Background Technology

[0002] Steel castings, as key structural components, are widely used in machinery manufacturing, bridge construction, marine engineering, and heavy equipment. However, when steel castings are used for extended periods in harsh environments such as outdoor humidity, salt spray, or industrial atmospheres, their surfaces are prone to electrochemical corrosion and oxidation, significantly shortening their service life.

[0003] To improve the durability of steel castings, a protective coating is usually applied to their surface. However, most existing protective coatings are ordinary epoxy or acrylic systems, which have problems such as insufficient adhesion, poor toughness, and poor weather resistance. Under the influence of external factors such as ultraviolet radiation and alternating temperature and humidity, the coating performance will decline, affecting the service life of the steel castings.

[0004] In summary, the preparation of a steel casting coated with a high-strength, high-toughness, and weather-resistant coating is of great significance. Summary of the Invention

[0005] The purpose of this invention is to provide a steel casting coated with a high-strength, high-toughness, and weather-resistant coating and its preparation method, so as to solve the problems raised in the prior art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for preparing a steel casting coated with a high-strength, high-toughness, and weather-resistant coating includes the following steps:

[0008] Step 1: Mix epoxy resin, modified polyimide, alkylated lignin composite material, polyamide, and solvent evenly to obtain a high-strength, high-toughness, and weather-resistant coating;

[0009] Step 2: The base steel casting is cleaned in acetone, washed with water, dried, coated with a high-strength, high-toughness, weather-resistant coating, and cured by heating to obtain the steel casting.

[0010] In a more optimized form, the raw materials of the high-strength, high-toughness, and weather-resistant coating include the following components: by mass parts, 100 parts epoxy resin, 30-50 parts modified polyimide, 15-25 parts alkylated lignin composite material, 25-35 parts polyamide, and 80-100 parts solvent.

[0011] A more optimized method for preparing the modified polyimide is as follows: under nitrogen protection, aminobenzoyl ketone lignin and bis(4-aminophenyl) ether are added to N,N'-dimethylacetamide and mixed, then 3,3',4,4'-biphenyl dianhydride is added, and the mixture is stirred in an ice-water bath for 20-24 hours to obtain the modified polyimide.

[0012] In a more optimized form, the raw material for the modified polyimide comprises the following components: by mass parts, 15-25 parts of aminobenzoyl ketone lignin, 30-40 parts of bis(4-aminophenyl) ether, 50-60 parts of 3,3',4,4'-biphenyl dianhydride, and 150-200 parts of N,N'-dimethylacetamide.

[0013] A more optimized method for preparing aminobenzoyl lignin is as follows: (1) Phenolic lignin is added to an aqueous sodium hydroxide solution and mixed, p-phenylenediamine and formaldehyde aqueous solution are added, and the mixture is stirred at 60-80°C for 3-5 hours, washed, and dried to obtain p-aminoaniline lignin; (2) p-aminoaniline lignin is dispersed in deionized water, acetic anhydride is added and stirred for 3-4 hours, washed, and dried to obtain acetylated aniline lignin;

[0014] (3) Under nitrogen protection, acetylated aniline lignin and 4-nitrobenzoyl chloride were added to 1,2-dichloroethane, anhydrous aluminum chloride was added and mixed, refluxed and stirred for 4-6 hours, cooled to room temperature, and post-treated to obtain nitrobenzoyl ketone lignin; (4) Nitrobenzoyl modified lignin was added to ethanol for dispersion, Pd / C was added and mixed, hydrogen was introduced and stirred for 6-8 hours, filtered and washed to obtain aminobenzoyl ketone lignin.

[0015] The preparation method of phenolic lignin in the scheme is as follows: at 110℃, lignin is added to phenol and mixed, sulfuric acid is added, stirred for 25 minutes, cooled to room temperature, and slowly added to hydrochloric acid at pH=2 to precipitate. After filtration, it is washed with 2M hydrochloric acid, washed with water until neutral, and dried to obtain phenolic lignin. The benzene ring of phenol is attached to the benzene ring skeleton of lignin through electrophilic substitution. The mass ratio of lignin to phenol is 1:2, and the lignin is basic lignin.

[0016] In a more optimized form, the raw material for the p-aminoaniline lignin comprises the following components: by mass parts, 10-15 parts of phenolic lignin, 3-5 parts of p-phenylenediamine, and 20-25 parts of formaldehyde aqueous solution; the mass ratio of the p-aminoaniline lignin to acetic anhydride is 1:2-3.

[0017] The raw material for the nitrobenzyl lignin comprises the following components: by mass, 10-15 parts acetylated aniline lignin, 4-6 parts 4-nitrobenzyl chloride, 3.5-5 parts anhydrous aluminum chloride, and 70-100 parts 1,2-dichloroethane; the mass ratio of the nitrobenzyl modified lignin to Pd / C is 12-17:1.

[0018] A more optimized method for preparing the alkylated lignin composite material is as follows: under nitrogen protection, aminobenzoyl ketone lignin and sebacate chloride are added to 1,2-dichloroethane and mixed, anhydrous aluminum chloride is added and mixed, the mixture is refluxed and stirred for 6-8 hours, cooled to room temperature, and then post-treated to obtain the alkylated lignin composite material.

[0019] In a more optimized form, the raw materials for the alkylated lignin composite material include the following components: by mass parts, 7-15 parts aminobenzoyl ketone lignin, 6-10 parts sebacate chloride, 4-6 parts anhydrous aluminum chloride, and 70-100 parts 1,2-dichloroethane.

[0020] In this scheme, phenolic lignin, p-phenylenediamine, and formaldehyde are used as raw materials. Under alkaline conditions, a Mannich reaction is carried out to introduce aromatic primary amino groups onto the phenolic lignin, resulting in p-aminoaniline lignin. The amino group on the lignin reacts with acetic anhydride to obtain acetylated aniline lignin. This acetylated aniline lignin undergoes a Friedel-Crafts acylation reaction with anhydrous aluminum chloride and 4-nitrobenzoyl chloride to introduce p-nitrobenzoyl groups onto the lignin, resulting in nitrobenzoyl ketone lignin. Finally, catalytic hydrogenation is performed to reduce the nitro group to an amino group, resulting in aminobenzoyl ketone lignin. The amino group can copolymerize with polyimide monomers, making the lignin part of the cross-linking network and enhancing the interfacial bonding of the coating.

[0021] A more optimized process is as follows: treat at 60~80℃ for 1~2 hours, raise the temperature to 110~120℃ for 1.5~2 hours, raise the temperature to 160~180℃ and hold for 2~4 hours, and then cool to room temperature at a rate of 1~5℃ / min.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] In this scheme, lignin is modified and introduced into polyimide, which is then mixed with epoxy resin, alkylated lignin composite material and polyamide to obtain a high-strength, high-toughness and weather-resistant coating, forming a high-strength, high-toughness and weather-resistant protective coating on the surface of steel castings.

[0024] In this process, benzoyl ketone groups are introduced onto lignin and catalytically hydrogenated to obtain aminobenzoyl ketone lignin. This lignin, along with bis(4-aminophenyl) ether and 3,3',4,4'-biphenyl dianhydride, is used as raw materials to prepare modified polyimide. The hydrophobicity of the benzoyl group reduces moisture penetration in humid and hot environments, decreases the risk of hydrolytic aging, and synergistically improves UV protection, thereby enhancing weather resistance. Furthermore, it can generate stronger π-π conjugation and polar interactions with the polyimide chain, significantly improving the dispersion and interfacial bonding of lignin in the resin matrix, which helps to enhance the weather resistance and mechanical strength of the coating.

[0025] In this scheme, aminobenzoyl ketone-based lignin, polyimide, and epoxy resin synergistically improve rigidity. Bis(4-aminophenyl) ether is introduced into the polyimide to balance some of the rigidity; however, relying solely on bis(4-aminophenyl) ether makes it difficult to improve the coating's toughness. Introducing other toughening materials may reduce the coating's weather resistance. To address this issue, the scheme further modifies the aminobenzoyl ketone-based lignin by introducing flexible long alkyl chains (from sebacate chloride) to obtain an alkylated lignin composite material. This material not only has good compatibility with modified polyimide, but the other active groups on the alkylated lignin composite material can improve its interfacial bonding with the epoxy resin, thereby improving the overall toughness and weather resistance of the coating and reducing its impact on coating strength. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0027] In the following specific embodiments, the parts are by weight. In this embodiment, it should be noted that there are no special restrictions on the purchase manufacturers of all the raw materials involved in this invention. Exemplary examples include: p-phenylenediamine CAS number 106-50-3; formaldehyde CAS number 50-00-0; acetic anhydride CAS number 108-24-7; 4-nitrobenzoyl chloride CAS number 122-04-3; anhydrous aluminum chloride CAS number 7446-70-0; Pd / C is 10% Pd / C; bis(4-aminophenyl) ether CAS number 106426-62-4; 3,3',4,4'-biphenyl dianhydride CAS number 2420-87-3; epoxy resin type is E51 epoxy resin; polyamide is polyamide 650.

[0028] Example 1: A method for preparing a steel casting coated with a high-strength, high-toughness, and weather-resistant coating, comprising the following steps:

[0029] Pre-preparation: The preparation method of aminobenzoyl ketone lignin is as follows: (1) 15 parts of phenolic lignin are added to sodium hydroxide aqueous solution and mixed, 5 parts of p-phenylenediamine and 22 parts of formaldehyde aqueous solution (concentration of 37wt%) are added, and the mixture is stirred at 80℃ for 4 hours, washed and dried to obtain p-aminoaniline lignin; (2) The mass ratio of p-aminoaniline lignin to acetic anhydride is 1:2; p-aminoaniline lignin is dispersed in deionized water, acetic anhydride is added and stirred for 3 hours, washed and dried to obtain acetylated aniline lignin;

[0030] (3) Under nitrogen protection, 12 parts of acetylated aniline lignin and 5 parts of 4-nitrobenzyl chloride were added to 80 parts of 1,2-dichloroethane, and 3.5 parts of anhydrous aluminum chloride were added and mixed. The mixture was refluxed and stirred for 6 hours, cooled to room temperature, and added to an ice-water bath of 5wt% HCl and stirred for 2 hours. The mixture was filtered, and the precipitate was washed with saturated sodium bicarbonate aqueous solution and deionized water. The precipitate was added to ethanol and recrystallized to obtain nitrobenzyl ketone lignin. (4) The mass ratio of nitrobenzyl modified lignin to Pd / C was 14:1. Nitrobenzoyl modified lignin was added to ethanol and dispersed. Pd / C (the Pd content in Pd / C was 10wt%) was added and mixed. Hydrogen was introduced and stirred for 7 hours. The mixture was filtered and washed to obtain aminobenzoenzyl ketone lignin.

[0031] The preparation method of alkylated lignin composite material is as follows: under nitrogen protection, 15 parts of aminobenzoyl ketone lignin and 10 parts of sebacyl chloride are added to 80 parts of 1,2-dichloroethane and mixed. 6 parts of anhydrous aluminum chloride are added and mixed. The mixture is refluxed and stirred for 6 hours, cooled to room temperature, filtered, and the precipitate is washed with saturated sodium bicarbonate aqueous solution and deionized water. The precipitate is then added to ethanol for recrystallization to obtain alkylated lignin composite material.

[0032] Step 1: (1) Under nitrogen protection, 20 parts of aminobenzoyl ketone lignin and 35 parts of bis(4-aminophenyl) ether were added to 150 parts of N,N'-dimethylacetamide and mixed. Then 50 parts of 3,3',4,4'-biphenyl dianhydride were added and stirred in an ice-water bath for 22 hours to obtain modified polyimide.

[0033] (2) 100 parts epoxy resin, 30 parts modified polyimide, 15 parts alkylated lignin composite material, 25 parts polyamide, and 80 parts solvent (N,N-dimethylacetamide) are mixed evenly to obtain a high-strength, high-toughness, and weather-resistant coating.

[0034] Step 2: The base steel casting is cleaned in acetone, washed with water, dried, coated with a high-strength, high-toughness, and weather-resistant coating, treated at 80℃ for 2 hours, heated to 110℃ for 1.5 hours, heated to 165℃ for 3 hours, and cooled to room temperature at a rate of 2℃ / min to obtain the steel casting.

[0035] Example 2: A method for preparing a steel casting coated with a high-strength, high-toughness, and weather-resistant coating, comprising the following steps:

[0036] Pre-preparation: The preparation method of aminobenzoyl ketone lignin is as follows: (1) 15 parts of phenolic lignin are added to sodium hydroxide aqueous solution and mixed, 5 parts of p-phenylenediamine and 22 parts of formaldehyde aqueous solution (concentration of 37wt%) are added, and the mixture is stirred at 80℃ for 4 hours, washed and dried to obtain p-aminoaniline lignin; (2) The mass ratio of p-aminoaniline lignin to acetic anhydride is 1:2; p-aminoaniline lignin is dispersed in deionized water, acetic anhydride is added and stirred for 3 hours, washed and dried to obtain acetylated aniline lignin;

[0037] (3) Under nitrogen protection, 12 parts of acetylated aniline lignin and 5 parts of 4-nitrobenzyl chloride were added to 80 parts of 1,2-dichloroethane, and 3.5 parts of anhydrous aluminum chloride were added and mixed. The mixture was refluxed and stirred for 6 hours, cooled to room temperature, and added to an ice-water bath of 5wt% HCl and stirred for 2 hours. The mixture was filtered, and the precipitate was washed with saturated sodium bicarbonate aqueous solution and deionized water. The precipitate was added to ethanol and recrystallized to obtain nitrobenzyl ketone lignin. (4) The mass ratio of nitrobenzyl modified lignin to Pd / C was 14:1. Nitrobenzoyl modified lignin was added to ethanol and dispersed. Pd / C (the Pd content in Pd / C was 10wt%) was added and mixed. Hydrogen was introduced and stirred for 7 hours. The mixture was filtered and washed to obtain aminobenzoenzyl ketone lignin.

[0038] The preparation method of alkylated lignin composite material is as follows: under nitrogen protection, 15 parts of aminobenzoyl ketone lignin and 10 parts of sebacyl chloride are added to 80 parts of 1,2-dichloroethane and mixed. 6 parts of anhydrous aluminum chloride are added and mixed. The mixture is refluxed and stirred for 6 hours, cooled to room temperature, filtered, and the precipitate is washed with saturated sodium bicarbonate aqueous solution and deionized water. The precipitate is then added to ethanol for recrystallization to obtain alkylated lignin composite material.

[0039] Step 1: (1) Under nitrogen protection, 20 parts of aminobenzoyl ketone lignin and 35 parts of bis(4-aminophenyl) ether were added to 150 parts of N,N'-dimethylacetamide and mixed. Then 50 parts of 3,3',4,4'-biphenyl dianhydride were added and stirred in an ice-water bath for 22 hours to obtain modified polyimide.

[0040] (2) 100 parts epoxy resin, 40 parts modified polyimide, 20 parts alkylated lignin composite material, 25 parts polyamide, and 80 parts solvent (N,N-dimethylacetamide) are mixed evenly to obtain a high-strength, high-toughness, and weather-resistant coating.

[0041] Step 2: The base steel casting is cleaned in acetone, washed with water, dried, coated with a high-strength, high-toughness, and weather-resistant coating, treated at 80℃ for 2 hours, heated to 110℃ for 1.5 hours, heated to 165℃ for 3 hours, and cooled to room temperature at a rate of 2℃ / min to obtain the steel casting.

[0042] Example 3: A method for preparing a steel casting coated with a high-strength, high-toughness, and weather-resistant coating, comprising the following steps:

[0043] Pre-preparation: The preparation method of aminobenzoyl ketone lignin is as follows: (1) 15 parts of phenolic lignin are added to sodium hydroxide aqueous solution and mixed, 5 parts of p-phenylenediamine and 22 parts of formaldehyde aqueous solution (concentration of 37wt%) are added, and the mixture is stirred at 80℃ for 4 hours, washed and dried to obtain p-aminoaniline lignin; (2) The mass ratio of p-aminoaniline lignin to acetic anhydride is 1:2; p-aminoaniline lignin is dispersed in deionized water, acetic anhydride is added and stirred for 3 hours, washed and dried to obtain acetylated aniline lignin;

[0044] (3) Under nitrogen protection, 12 parts of acetylated aniline lignin and 5 parts of 4-nitrobenzyl chloride were added to 80 parts of 1,2-dichloroethane, and 3.5 parts of anhydrous aluminum chloride were added and mixed. The mixture was refluxed and stirred for 6 hours, cooled to room temperature, and added to an ice-water bath of 5wt% HCl and stirred for 2 hours. The mixture was filtered, and the precipitate was washed with saturated sodium bicarbonate aqueous solution and deionized water. The precipitate was added to ethanol and recrystallized to obtain nitrobenzyl ketone lignin. (4) The mass ratio of nitrobenzyl modified lignin to Pd / C was 14:1. Nitrobenzoyl modified lignin was added to ethanol and dispersed. Pd / C (the Pd content in Pd / C was 10wt%) was added and mixed. Hydrogen was introduced and stirred for 7 hours. The mixture was filtered and washed to obtain aminobenzoenzyl ketone lignin.

[0045] The preparation method of alkylated lignin composite material is as follows: under nitrogen protection, 15 parts of aminobenzoyl ketone lignin and 10 parts of sebacyl chloride are added to 80 parts of 1,2-dichloroethane and mixed. 6 parts of anhydrous aluminum chloride are added and mixed. The mixture is refluxed and stirred for 6 hours, cooled to room temperature, filtered, and the precipitate is washed with saturated sodium bicarbonate aqueous solution and deionized water. The precipitate is then added to ethanol for recrystallization to obtain alkylated lignin composite material.

[0046] Step 1: (1) Under nitrogen protection, 20 parts of aminobenzoyl ketone lignin and 35 parts of bis(4-aminophenyl) ether were added to 150 parts of N,N'-dimethylacetamide and mixed. Then 50 parts of 3,3',4,4'-biphenyl dianhydride were added and stirred in an ice-water bath for 22 hours to obtain modified polyimide.

[0047] (2) 100 parts epoxy resin, 50 parts modified polyimide, 25 parts alkylated lignin composite material, 25 parts polyamide, and 80 parts solvent (N,N-dimethylacetamide) are mixed evenly to obtain a high-strength, high-toughness, and weather-resistant coating.

[0048] Step 2: The base steel casting is cleaned in acetone, washed with water, dried, coated with a high-strength, high-toughness, and weather-resistant coating, treated at 80℃ for 2 hours, heated to 110℃ for 1.5 hours, heated to 165℃ for 3 hours, and cooled to room temperature at a rate of 2℃ / min to obtain the steel casting.

[0049] Comparative Example 1 is based on Example 3, except that the alkylated lignin composite material is replaced with p-aminoaniline lignin; the other operating steps are the same.

[0050] Step 1: (1) Under nitrogen protection, 20 parts of aminobenzoyl ketone lignin and 35 parts of bis(4-aminophenyl) ether were added to 150 parts of N,N'-dimethylacetamide and mixed. Then 50 parts of 3,3',4,4'-biphenyl dianhydride were added and stirred in an ice-water bath for 22 hours to obtain modified polyimide.

[0051] (2) Mix 100 parts of epoxy resin, 50 parts of modified polyimide, 25 parts of p-aminoaniline lignin, 25 parts of polyamide, and 80 parts of solvent (N,N-dimethylacetamide) evenly to obtain a high-strength, high-toughness, and weather-resistant coating.

[0052] Step 2: The base steel casting is cleaned in acetone, washed with water, dried, coated with a high-strength, high-toughness, and weather-resistant coating, treated at 80℃ for 2 hours, heated to 110℃ for 1.5 hours, heated to 165℃ for 3 hours, and cooled to room temperature at a rate of 2℃ / min to obtain the steel casting.

[0053] Comparative Example 2 is based on Example 3, except that aminobenzoyl ketone lignin was not added to the modified polyurethane; the other operating steps are the same.

[0054] Step 1: (1) Under nitrogen protection, 35 parts of bis(4-aminophenyl) ether were added to 150 parts of N,N'-dimethylacetamide and mixed. Then 50 parts of 3,3',4,4'-biphenyl dianhydride were added and stirred in an ice-water bath for 22 hours to obtain modified polyimide.

[0055] (2) 100 parts epoxy resin, 50 parts modified polyimide, 25 parts alkylated lignin composite material, 25 parts polyamide, and 80 parts solvent (N,N-dimethylacetamide) are mixed evenly to obtain a high-strength, high-toughness, and weather-resistant coating.

[0056] Step 2: The base steel casting is cleaned in acetone, washed with water, dried, coated with a high-strength, high-toughness, and weather-resistant coating, treated at 80℃ for 2 hours, heated to 110℃ for 1.5 hours, heated to 165℃ for 3 hours, and cooled to room temperature at a rate of 2℃ / min to obtain the steel casting.

[0057] Comparative Example 3 is based on Example 3, except that in the preparation of the alkylated lignin composite material, p-aminoaniline lignin and sebacate chloride are used as raw materials, while the other operation steps are the same.

[0058] The preparation method of alkylated lignin composite material is as follows: (1) 15 parts of phenolic lignin are added to sodium hydroxide aqueous solution and mixed, 5 parts of p-phenylenediamine and 22 parts of formaldehyde aqueous solution (concentration of 37wt%) are added, and the mixture is stirred at 80℃ for 4 hours. After washing and drying, p-aminoaniline lignin is obtained; (2) Under nitrogen protection, 15 parts of aminoaniline lignin and 10 parts of sebacyl chloride are added to 80 parts of 1,2-dichloroethane and mixed, 6 parts of anhydrous aluminum chloride are added and mixed, and the mixture is refluxed and stirred for 6 hours. After cooling to room temperature, the mixture is filtered, and the precipitate is washed with saturated sodium bicarbonate aqueous solution and deionized water. It is then added to ethanol for recrystallization to obtain alkylated lignin composite material.

[0059] Step 1: (1) Under nitrogen protection, 20 parts of aminobenzoyl ketone lignin and 35 parts of bis(4-aminophenyl) ether were added to 150 parts of N,N'-dimethylacetamide and mixed. Then 50 parts of 3,3',4,4'-biphenyl dianhydride were added and stirred in an ice-water bath for 22 hours to obtain modified polyimide.

[0060] (2) 100 parts epoxy resin, 50 parts modified polyimide, 25 parts alkylated lignin composite material, 25 parts polyamide, and 80 parts solvent (N,N-dimethylacetamide) are mixed evenly to obtain a high-strength, high-toughness, and weather-resistant coating.

[0061] Step 2: The base steel casting is cleaned in acetone, washed with water, dried, coated with a high-strength, high-toughness, and weather-resistant coating, treated at 80℃ for 2 hours, heated to 110℃ for 1.5 hours, heated to 165℃ and held for 3 hours, and then cooled to room temperature at a rate of 2℃ / min to obtain the steel casting.

[0062] I. Coating performance testing experiment: The coatings prepared in Examples 1-3 and Comparative Examples 1-3 were applied to the clean substrate surface and cured by heating to obtain a high-strength, high-toughness, and weather-resistant coating (thickness of 150µm). The following experiments were conducted.

[0063] (1) Tensile strength test: The tensile strength of the high-strength, high-toughness, weather-resistant coating prepared above was tested according to GB / T1040.3-2006;

[0064] (2) Impact strength test: The high-strength, high-toughness, weather-resistant coating prepared above was tested for impact strength (kg*cm) according to GB / T1732-2020 Test Method for Impact Resistance of Film.

[0065] (3) Weather resistance test: According to GB / T14522-2008, the high-strength and high-toughness weather-resistant coating prepared above was placed in an aging test chamber with a relative humidity of 65%, a temperature of 60℃, and an irradiation intensity of 0.71 W·m -2 The impact strength (kg*cm) after treatment was measured after irradiation under 340nm ultraviolet light for 240 hours, with a cycle of 12 hours (including 8 hours of irradiation, 0.25 hours of spraying, and 3.75 hours of condensation). The impact strength was then measured based on the impact strength obtained from test (2). The impact strength retention rate (%) was calculated. The impact strength retention rate (%) = (impact strength after treatment / impact strength) × 100%.

[0066] Table 1

[0067]

[0068] Conclusions: Comparative Example 1 is based on Example 3, except that the alkylated lignin composite material was replaced with p-aminoaniline lignin; the absence of alkylation crosslinking and benzoyl ketone structure led to a decrease in mechanical properties and UV protection, thus causing a decline in the performance of the coating prepared in Comparative Example 1; Comparative Example 2 is based on Example 3, except that aminobenzoyl ketone lignin was not added to the modified polyurethane; the rigid skeleton of aminobenzoyl ketone lignin can form a synergistic reinforcing structure with polyimide, and its absence reduces the rigidity of the molecular chain; since the aromatic ring of lignin can improve UV aging resistance and its polar groups can optimize interfacial bonding and reduce stress concentration during impact, its absence reduces both toughness and weather resistance; Comparative Example 3 is based on Example 3, except that p-aminoaniline lignin and sebacate chloride were used as raw materials in the preparation of the alkylated lignin composite material; this led to a decrease in performance because the benzoyl ketone group can synergistically improve UV protection and strength with lignin and sebacate chloride.

[0069] II. Adhesion test of steel castings: The adhesion of the steel castings prepared in Example 3 was tested according to the standard of ISO4624-2023; Conclusion: The adhesion of Example 3 is 27.8 MPa; According to Table 1, Example 3 has a high-strength, high-toughness, and weather-resistant coating, which has a good protective effect on the base steel castings.

[0070] 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.

Claims

1. A method for preparing a steel casting coated with a high-strength, high-toughness, and weather-resistant coating, characterized in that: The following steps are included: Step 1: Mix epoxy resin, modified polyimide, alkylated lignin composite material, polyamide, and solvent evenly to obtain a high-strength, high-toughness, and weather-resistant coating; Step 2: The base steel casting is cleaned in acetone, washed with water, dried, coated with a high-strength, high-toughness, weather-resistant coating, and cured at a high temperature to obtain the steel casting. The modified polyimide is prepared by mixing aminobenzoyl ketone lignin and bis(4-aminophenyl) ether with N,N'-dimethylacetamide under nitrogen protection, then adding 3,3',4,4'-biphenyl dianhydride and stirring in an ice-water bath for 20-24 hours to obtain the modified polyimide. The preparation method of the aminobenzoyl ketone lignin is as follows: (1) Phenolic lignin is added to sodium hydroxide aqueous solution and mixed, p-phenylenediamine and formaldehyde aqueous solution are added, and the mixture is stirred at 60~80℃ for 3~5 hours, washed and dried to obtain p-aminoaniline lignin; (2) p-aminoaniline lignin is dispersed in deionized water, acetic anhydride is added and stirred for 3~4 hours, washed and dried to obtain acetylated aniline lignin; (3) Under nitrogen protection, acetylated aniline lignin and 4-nitrobenzyl chloride were added to 1,2-dichloroethane, anhydrous aluminum chloride was added and mixed, refluxed and stirred for 4-6 hours, cooled to room temperature, and post-treated to obtain nitrobenzyl ketone lignin; (4) Nitrobenzoyl modified lignin was added to ethanol for dispersion, Pd / C was added and mixed, hydrogen was introduced and stirred for 6-8 hours, filtered and washed to obtain aminobenzoenzyl ketone lignin; The preparation method of the alkylated lignin composite material is as follows: under nitrogen protection, aminobenzoyl ketone lignin and sebacate chloride are added to 1,2-dichloroethane and mixed, anhydrous aluminum chloride is added and mixed, refluxed and stirred for 6-8 hours, cooled to room temperature, and then post-treated to obtain the alkylated lignin composite material.

2. The method of claim 1, wherein the steel casting is surface coated with a high strength and high toughness weather resistant coating. The raw materials of the high-strength, high-toughness, and weather-resistant coating include the following components: by mass parts, 100 parts epoxy resin, 30-50 parts modified polyimide, 15-25 parts alkylated lignin composite material, 25-35 parts polyamide, and 80-100 parts solvent.

3. The method of claim 1, wherein the steel casting is surface coated with a high strength and high toughness weather resistant coating. The modified polyimide raw materials include the following components: by mass, 15-25 parts of aminobenzoyl ketone lignin, 30-40 parts of bis(4-aminophenyl) ether, 50-60 parts of 3,3',4,4'-biphenyl dianhydride, and 150-200 parts of N,N'-dimethylacetamide.

4. The method of claim 1, wherein the steel casting is surface coated with a high strength and high toughness weather resistant coating. The raw material for the p-aminoaniline lignin comprises the following components: by mass parts, 10-15 parts of phenolic lignin, 3-5 parts of p-phenylenediamine, and 20-25 parts of formaldehyde aqueous solution; the mass ratio of the p-aminoaniline lignin to acetic anhydride is 1:2-3. The raw material for the nitrobenzyl lignin comprises the following components: by mass, 10-15 parts acetylated aniline lignin, 4-6 parts 4-nitrobenzyl chloride, 3.5-5 parts anhydrous aluminum chloride, and 70-100 parts 1,2-dichloroethane; the mass ratio of the nitrobenzyl modified lignin to Pd / C is 12-17:

1.

5. The method of claim 1, wherein the steel casting is surface coated with a high strength and high toughness weather resistant coating. The raw materials of the alkylated lignin composite material include the following components: by mass, 7-15 parts aminobenzoyl ketone lignin, 6-10 parts sebacate chloride, 4-6 parts anhydrous aluminum chloride, and 70-100 parts 1,2-dichloroethane.

6. The method of claim 1, wherein the steel casting is surface coated with a high strength and high toughness weatherable coating. The process conditions for heating and curing are as follows: treat at 60~80℃ for 1~2 hours, heat to 110~120℃ for 1.5~2 hours, heat to 160~180℃ and hold for 2~4 hours, and then cool to room temperature at a rate of 1~5℃ / min.

7. A steel casting is prepared by a method for preparing a steel casting with a surface coated with a high-strength, high-toughness, and weather-resistant coating according to any one of claims 1 to 6.

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