Highly permeable modified water-based paint stripper and method for preparing the same

Abstract

This invention belongs to the field of paint removers and discloses a high-penetration modified water-based paint remover and its preparation method. The paint remover includes the following raw materials: deionized water, benzyl alcohol, formic acid, composite penetrant, sodium dodecylbenzenesulfonate, modified nano-Fe3O4, modified microporous starch, thickener, corrosion inhibitor, and defoamer. The modified nano-Fe3O4 is prepared by first preparing nano-Fe3O4, then forming a dense SiO2 shell on the Fe3O4 surface through tetraethyl orthosilicate hydrolysis, followed by surface treatment with a silane coupling agent, and finally grafting polyaspartic acid. The modified microporous starch is prepared by first preparing microporous starch using an enzymatic hydrolysis method, then loading molten microcrystalline wax and synergistic agents through a vacuum impregnation method, and finally cooling and solidifying. This invention, through the synergistic effect of the benzyl alcohol and formic acid main solvent system with modified nano-Fe3O4 and modified microporous starch, ensures efficient paint removal while providing good protection for the metal substrate.

Description

Technical Field

[0001] This invention belongs to the field of paint remover technology, specifically relating to a high-penetration modified water-based paint remover and its preparation method. Background Technology

[0002] Paint removers are widely used in industrial fields such as rework and repair of metal workpieces, cleaning of fixtures, and treatment of coating defects. Traditional paint removers use dichloromethane as the main solvent. Although they have advantages such as high paint removal efficiency and speed, their high volatility, strong toxicity, and ozone-depleting effects have attracted widespread attention. With increasingly stringent environmental regulations, the use of dichloromethane-based paint removers has been gradually restricted or banned in developed countries such as Europe and the United States. To replace dichloromethane-based paint removers, researchers have developed a variety of environmentally friendly paint removers. Benzyl alcohol-based paint removers have become a research hotspot due to their strong dissolving power, low toxicity, and low volatility.

[0003] Chinese patent application CN117210050A discloses an environmentally friendly paint remover composed of the following raw materials: benzyl alcohol, formic acid, OP-10, triazole, and distilled water. This invention uses benzyl alcohol instead of methylene chloride as the main solvent in traditional paint removers, significantly reducing toxicity, environmental impact, and the risk of injury to workers. Furthermore, the addition of formic acid (an accelerator), OP-10 (a surfactant), and a corrosion inhibitor enhances the paint removal effect, while the inclusion of a corrosion inhibitor protects the substrate surface. However, the following technical problems still exist in the practical application of this type of paint remover: (1) Difficulty in removing paint from complex structures. For workpieces with complex structures such as blind holes, deep grooves, and threads, traditional immersion paint removers rely solely on natural solvent wetting and surfactants to reduce surface tension, making it difficult to penetrate deep into the structure, resulting in incomplete paint removal. Secondary treatment or mechanical cleaning is often required, which seriously affects production efficiency; (2) The contradiction between paint removal rate and substrate protection. To improve paint removal efficiency, existing technologies often use methods such as increasing acid concentration or adding strong corrosive additives, but this will aggravate the corrosion of metal substrates; (3) Single function of functional additives. The conventional additives such as penetrants and surfactants added to existing water-based paint removers have single functions and lack an adjustable response mechanism, making it difficult to achieve the synergistic effect of multiple functions such as enhanced penetration and paint residue separation. Therefore, there is an urgent need for a water-based environmentally friendly paint remover that combines paint removal effect and multifunctionality to solve the problems existing in the current technology. Summary of the Invention

[0004] To address the shortcomings mentioned in the background art, the present invention aims to provide a high-penetration modified water-based paint remover and its preparation method. Through the synergistic combination of benzyl alcohol, formic acid as the main solvent system with modified nano-Fe3O4 and modified microporous starch, it exhibits excellent peeling ability on various paint films under heating conditions. Compared with existing water-based paint removers, the paint removal efficiency is improved and the paint removal time is shortened.

[0005] The objective of this invention can be achieved through the following technical solutions: A highly penetrating modified water-based paint remover comprises the following raw materials in parts by weight: 45-50 parts deionized water, 30-40 parts benzyl alcohol, 3-5 parts formic acid, 1-3 parts composite penetrant, 1-3 parts sodium dodecylbenzenesulfonate, 1-3 parts modified nano Fe3O4, 2-4 parts modified microporous starch, 1-2 parts thickener, 0.4-0.6 parts corrosion inhibitor, and 0.4-0.6 parts defoamer; The modified nano Fe3O4 was first prepared by co-precipitation, then a dense SiO2 shell was formed on the surface of Fe3O4 by hydrolysis of tetraethyl orthosilicate, and the surface was treated with a silane coupling agent. Finally, polyaspartic acid was grafted onto the surface of the SiO2 layer. The modified microporous starch is prepared by first using an enzymatic hydrolysis method, then loading molten microcrystalline wax and synergistic agents into the micropores through a vacuum impregnation method, and finally cooling and solidifying to achieve solid wax sealing of the pores. The synergistic agent is a compound of isooctanol phosphate and D-limonene.

[0006] Preferably, the composite penetrant is a mixture of fatty alcohol polyoxyethylene ether and alkyl glycoside in a mass ratio of 1:1 to 2.

[0007] Preferably, the thickener is methylcellulose, the corrosion inhibitor is benzotriazole, and the defoamer is an organosilicone defoamer.

[0008] Preferably, the preparation method of the modified nano-Fe3O4 includes the following steps: A. Dissolve ferric chloride and ferrous ammonium sulfate in deionized water at a mass ratio of 2:1, purge with nitrogen to remove oxygen, heat to 80°C, quickly add ammonia to adjust the pH to 10-11, mature at 80°C for 20-40 min, separate the product with a magnet, wash with deionized water until neutral, and vacuum dry to obtain nano Fe3O4. B. The nano-Fe3O4 was added to a mixed solvent of ethanol and water and ultrasonically dispersed. The pH was adjusted to 10-11 with ammonia water and stirred for 20-40 min. Tetraethyl orthosilicate was slowly added and reacted at room temperature for 18-24 h. Then 3-aminopropyltriethoxysilane was added and the reaction was continued for 0.5-1.5 h. The product was separated by magnetism, washed three times with ethanol, and vacuum dried to obtain SiO2-coated nano-Fe3O4. C. Polyaspartic acid was dissolved in MES buffer solution at pH 4-5, and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide were added. The mixture was activated at room temperature for 20-30 min. The SiO2-coated nano-Fe3O4 was dispersed in the activated polyaspartic acid solution and ultrasonically dispersed until uniform. The mixture was stirred at room temperature for 8-12 h. The product was separated by magnetic separation, washed three times alternately with deionized water and ethanol, and vacuum dried to obtain modified nano-Fe3O4.

[0009] Preferably, the mass ratio of the nano-Fe3O4, tetraethyl orthosilicate, and 3-aminopropyltriethoxysilane is 4:1:0.2.

[0010] Preferably, the mass ratio of the SiO2-coated nano-Fe3O4, polyaspartic acid, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide is 1:0.5:0.2:0.05.

[0011] Preferably, the method for preparing the modified microporous starch includes the following steps: (1) Disperse corn starch in an acetate-sodium acetate buffer solution with pH 5.5-6 to prepare a starch milk of 10-15 wt%. Add saccharifying enzyme and α-amylase and perform enzymatic hydrolysis in a water bath at 55℃ for 12-20 h. After the enzymatic hydrolysis is completed, adjust the pH to 9-10 with NaOH solution to terminate the reaction. Filter and collect the precipitate, wash it three times alternately with deionized water and anhydrous ethanol, and dry it under vacuum at 50℃ to obtain microporous starch. (2) Melt the microcrystalline wax in an oven at 70~80℃, then mix the melted microcrystalline wax with isooctanol phosphate, D-limonene and Tween 80 in proportion, stir evenly to form a liquid core material mixture, add microporous starch to the core material mixture, evacuate to -0.09MPa, hold pressure for 20~40min and then release the vacuum, repeat the evacuation and release operation 2~3 times; (3) Take out the impregnated product, cool it at room temperature, wash the surface quickly with cold ethanol to remove the unimpregnated free core material, dry it at a low temperature below 40°C, pass it through a 200-mesh sieve, and modify the microporous starch.

[0012] Preferably, the amount of saccharifying enzyme added is 1.0~1.5% of the total mass of corn starch, and the amount of α-amylase added is 0.5~1.0% of the total mass of corn starch.

[0013] Preferably, the core material is a mixture of microcrystalline wax, isooctanol phosphate, D-limonene and Tween-80 in a mass ratio of 15:3:2:1, and the mass ratio of microporous starch to the core material is 1:2~3.

[0014] A method for preparing a high-penetration modified water-based paint remover includes the following steps: Add deionized water to a stainless steel reactor, control the reactor temperature at 40-50℃, slowly add methylcellulose, and stir for 10-20 minutes until completely dissolved and transparent. Then add sodium dodecylbenzenesulfonate, composite penetrant and defoamer, and stir for 10-20 minutes until evenly dispersed. Slowly add benzyl alcohol, and stir to emulsify into a milky white microemulsion. Add modified nano Fe3O4 and modified microporous starch, and stir for 10-20 minutes. Slowly add formic acid, control the temperature at <60℃, and stir for 5-15 minutes. Then add a slow-release agent, stir for 10-20 minutes, adjust the pH to 2.0-3.0, and cool to room temperature to obtain the high-penetration modified water-based paint remover.

[0015] The beneficial effects of this invention are: This invention utilizes a benzyl alcohol and formic acid as the main solvent system, combined with modified nano-Fe3O4 and modified microporous starch, to exhibit superior peeling ability against various types of paint films under heating conditions. Compared with existing water-based paint removers, it improves paint removal efficiency and shortens the paint removal time. The modified nano-Fe3O4 of this invention gives the paint remover magnetic responsiveness, allowing it to actively penetrate into complex structures such as blind holes, deep grooves, and threads on the workpiece under an applied magnetic field, achieving paint removal without dead angles. It is particularly suitable for paint removal from workpieces with complex structures such as automotive parts and precision mechanical components. This invention effectively solves the technical problem of fine, suspended paint sludge and secondary contamination of the workpiece during the use of traditional paint removers by utilizing the paint sludge flocculation and self-cleaning function of modified microporous starch. Through the chelating protection effect of polyaspartic acid on the surface of modified nano-Fe3O4 and the physical isolation effect of microcrystalline wax in modified microporous starch, this paint remover ensures efficient paint removal while providing good protection for the metal substrate. This invention is a water-based system that does not contain toxic or harmful solvents such as dichloromethane and phenol. The product is biodegradable and meets green and environmental protection requirements. Compared with traditional dichloromethane-based paint removers, it significantly reduces the harm to the health of operators and the environment.

[0016] This invention modifies the preparation of nano-Fe3O4 by first preparing nano-Fe3O4 through a co-precipitation method, then forming a dense SiO2 shell on the Fe3O4 surface through tetraethyl orthosilicate hydrolysis, followed by surface treatment with a silane coupling agent, and finally grafting polyaspartic acid onto the SiO2 layer surface. This invention introduces magnetic nanoparticles into an aqueous paint remover system. After applying an alternating magnetic field to the bottom or sides of the paint remover tank, the magnetic particles, driven by magnetic lines of force, carry paint remover molecules and forcibly penetrate areas that are difficult to reach naturally, such as micropores, gaps, and blind holes in the workpiece, achieving magnetically driven active penetration and significantly improving the paint removal effect on complex structured workpieces. Under the action of the alternating magnetic field, the magnetic particles generate continuous micro-movement between the paint film swelling interface, applying micro-disturbance mechanical force to the paint film and accelerating fatigue peeling of the paint film-substrate interface. This physical effect, combined with chemical swelling, significantly reduces dependence on highly corrosive components such as strong acids, enabling this invention to achieve efficient paint removal at lower acid concentrations while reducing the risk of corrosion to the substrate. The outer polyaspartic acid (PASP) molecular chain contains abundant carboxyl and amide groups, which can chelate metal ions such as iron and aluminum at the paint film / substrate interface, disrupting the chemical bonds between the paint film and the metal substrate, and significantly reducing the activation energy required for paint film peeling. Simultaneously, the adsorption of the PASP layer on the substrate surface alters the interfacial energy, making the paint film easier to swell and peel off. In the paint stripper, the PASP molecular chain extends to form a 10-20 nm thick polymer brush layer, generating a strong steric hindrance effect. This effectively overcomes the magnetic attraction and van der Waals forces between magnetic particles, allowing the particles to remain stably dispersed for over 30 days in acidic paint stripping solutions with pH 2-3 and high ionic strength, ensuring the particles maintain their nano-effect during long-term use. The carboxyl groups on the PASP molecular chain exhibit pH-responsive characteristics: in the paint stripping working solution, the carboxyl groups protonate, causing the molecular chain to shrink and collapse, facilitating particle penetration into the paint film gaps; during the recovery washing stage, the carboxyl groups deprotonate, the molecular chain extends and becomes negatively charged, enhancing electrostatic repulsion between particles, facilitating redispersion and magnetic separation recovery. The SiO2 interlayer is chemically inert, completely isolating the acidic paint stripper from direct contact with the Fe3O4 core, preventing Fe3O4 from being corroded by acid, and ensuring that the particles maintain stable magnetic response performance in long-term high-temperature acidic environments. Simultaneously, the abundant silanol groups on the SiO2 surface provide PASP with a high density of covalent grafting sites, resulting in significantly better grafting stability than direct coordination modification.

[0017] This invention relates to modified microporous starch, which is first prepared using an enzymatic hydrolysis method. Then, molten microcrystalline wax and synergistic agents are loaded into the micropores via vacuum impregnation, followed by cooling and solidification to achieve solid-state sealing of the pores. Utilizing the solid-liquid phase transition properties of the microcrystalline wax, the synergistic components are released "on demand." Under normal temperature storage and low-temperature conditions, the microcrystalline wax remains solid, locking isooctanol phosphate and D-limonene within the starch pores, resulting in a stable system. When the working solution is heated to 60-70°C, the microcrystalline wax melts, the pores open, and the core material is released. This temperature-sensitive release mechanism ensures that the synergistic components function effectively only at the paint stripping working temperature, avoiding ineffective consumption at room temperature and extending the service life of the bath solution. After paint stripping, when the working solution cools or is removed from the magnetic field environment, the microporous starch, with its ultra-high specific surface area and strong adsorption capacity, adsorbs the fine paint residue particles suspended in the solution. Through physical adsorption bridging, small paint residue particles are aggregated into large flocculent masses, accelerating paint residue sedimentation. This mechanism effectively solves the problems of fine, suspended paint residue, difficulty in cleaning, and easy secondary contamination of workpieces during the use of traditional paint removers. The isooctanol phosphate released by the microspheres is a highly efficient penetrant, significantly reducing the interfacial tension between the paint remover and the paint film, making it easier for the paint remover to wet and penetrate into the paint film. D-limonene, as a green co-solvent, is combined with the main solvent benzyl alcohol to enhance the dissolution ability of oil-based paints and coatings with high cross-linking density. The synergistic effect of both increases the penetration rate of the paint remover into difficult-to-remove paint films such as epoxy paint and powder coatings. Microcrystalline wax has extremely low surface energy; during the paint removal process, some microcrystalline wax adheres uniformly to the surface of the metal substrate, forming a very thin hydrophobic protective film. This physical barrier effectively isolates the acidic paint remover from direct contact with the metal substrate, playing a physical corrosion inhibitor role. Combined with the chemical corrosion inhibitor of the magnetic particle PASP layer, this invention reduces the corrosion rate of carbon steel.

[0018] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Detailed Implementation

[0019] 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.

[0020] Example 1 A modified nano-Fe3O4 is prepared by first preparing nano-Fe3O4 via co-precipitation, then forming a dense SiO2 shell on the Fe3O4 surface through tetraethyl orthosilicate hydrolysis, followed by surface treatment with a silane coupling agent, and finally grafting polyaspartic acid onto the SiO2 layer surface. The preparation method includes the following steps: A. Dissolve 27g of ferric chloride and 13.5g of ferrous ammonium sulfate in 500mL of deionized water, purge with nitrogen to remove oxygen, heat to 80℃, quickly add 25% ammonia to adjust the pH to 10~11, mature at 80℃ for 30min, separate the product with a magnet, wash with deionized water until neutral, and vacuum dry to obtain nano Fe3O4. B. 23.3 g of nano Fe3O4 was added to a mixed solvent of 150 mL ethanol and 30 mL water and ultrasonically dispersed. The pH was adjusted to 10-11 with ammonia water and stirred for 30 min. 5 mL of tetraethyl orthosilicate was slowly added and reacted at room temperature for 20 h. Then 1 mL of 3-aminopropyltriethoxysilane was added and the reaction was continued for 1 h. The product was separated by magnetic separation, washed three times with ethanol, and vacuum dried to obtain SiO2-coated nano Fe3O4. C. Dissolve 5g of polyaspartic acid in 200mL of MES buffer at pH 4-5, add 2g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 0.5g of N-hydroxysuccinimide, activate at room temperature for 25min, disperse 10g of SiO2-coated nano-Fe3O4 in the activated polyaspartic acid solution, ultrasonically disperse evenly, stir at room temperature for 10h, separate the product with a magnet, wash three times alternately with deionized water and ethanol, and vacuum dry to obtain modified nano-Fe3O4.

[0021] Example 2 A modified microporous starch is prepared by first using an enzymatic hydrolysis method, then loading molten microcrystalline wax and a synergistic agent into the micropores via a vacuum impregnation method, and finally cooling and solidifying to achieve solid wax sealing of the pores. The synergistic agent is a compound of isooctanol phosphate and D-limonene. The preparation method includes the following steps: (1) Disperse 35g of corn starch in 250mL of acetate-sodium acetate buffer solution with pH 5.5~6 to prepare starch milk, add 0.4g of saccharifying enzyme and 0.2g of α-amylase, and enzymatically hydrolyze the mixture in a water bath at 55℃ for 16h. After the enzymatic hydrolysis is completed, adjust the pH to 9~10 with 1mol / L NaOH solution to terminate the reaction, filter and collect the precipitate, wash it three times alternately with deionized water and anhydrous ethanol, and dry it under vacuum at 50℃ to obtain microporous starch; (2) Melt 30g of microcrystalline wax in an oven at 70~80℃, then mix the melted microcrystalline wax with 6g of isooctanol phosphate, 4g of D-limonene and 2g of Tween 80 in proportion, stir evenly to form a liquid core material mixture, add 16.8g of microporous starch to the core material mixture, evacuate to -0.09MPa, hold pressure for 30min and then release the vacuum, repeat the evacuation and release operation 2~3 times; (3) Take out the impregnated product, cool it at room temperature, wash the surface quickly with cold ethanol to remove the unimpregnated free core material, dry it at a low temperature below 40°C, pass it through a 200-mesh sieve, and modify the microporous starch.

[0022] Example 3 A highly permeable modified water-based paint remover comprises 45 parts deionized water, 40 parts benzyl alcohol, 3 parts formic acid, 2 parts fatty alcohol polyoxyethylene ether, 3 parts alkyl glycoside, 1 part sodium dodecylbenzenesulfonate, 3 parts modified nano Fe3O4, 2 parts modified microporous starch, 2 parts methylcellulose, 0.4 parts benzotriazole, and 0.6 parts organosilicon defoamer; the modified nano Fe3O4 was prepared in Example 1, and the modified microporous starch was prepared in Example 2.

[0023] The preparation method of the above-mentioned high-penetration modified water-based paint remover includes the following steps: Deionized water was added to a stainless steel reactor, and the reactor temperature was controlled at 40°C. Methylcellulose was slowly added and stirred for 20 minutes until completely dissolved and transparent. Then, sodium dodecylbenzenesulfonate, fatty alcohol polyoxyethylene ether, alkyl glycoside, and organosilicon defoamer were added and stirred for 10 minutes until evenly dispersed. Benzyl alcohol was slowly added and stirred to emulsify into a milky white microemulsion. Modified nano-Fe3O4 and modified microporous starch were added and stirred for 20 minutes. Formic acid was slowly added and the temperature was controlled at <60°C. The mixture was stirred for 5 minutes, followed by the addition of benzotriazole and stirring for 20 minutes. The pH was adjusted to 2.0~3.0, and the mixture was cooled to room temperature to obtain the high-penetration modified water-based paint remover.

[0024] Example 4 A highly permeable modified water-based paint remover comprises 50 parts deionized water, 30 parts benzyl alcohol, 5 parts formic acid, 0.5 parts fatty alcohol polyoxyethylene ether, 0.5 parts alkyl glycoside, 3 parts sodium dodecylbenzenesulfonate, 1 part modified nano-Fe3O4, 4 parts modified microporous starch, 1 part methylcellulose, 0.6 parts benzotriazole, and 0.4 parts organosilicon defoamer; the modified nano-Fe3O4 was prepared in Example 1, and the modified microporous starch was prepared in Example 2.

[0025] The preparation method of the above-mentioned high-penetration modified water-based paint remover includes the following steps: Deionized water was added to a stainless steel reactor, and the reactor temperature was controlled at 50°C. Methylcellulose was slowly added and stirred for 10 minutes until completely dissolved and transparent. Then, sodium dodecylbenzenesulfonate, fatty alcohol polyoxyethylene ether, alkyl glycoside, and organosilicon defoamer were added and stirred for 20 minutes until evenly dispersed. Benzyl alcohol was slowly added and stirred to emulsify into a milky white microemulsion. Modified nano-Fe3O4 and modified microporous starch were added and stirred for 10 minutes. Formic acid was slowly added and the temperature was controlled at <60°C. The mixture was stirred for 15 minutes, followed by the addition of benzotriazole and stirring for 10 minutes. The pH was adjusted to 2.0~3.0, and the mixture was cooled to room temperature to obtain the high-penetration modified water-based paint remover.

[0026] Example 5 A highly permeable modified water-based paint remover comprises 48 parts deionized water, 35 parts benzyl alcohol, 4 parts formic acid, 1.5 parts fatty alcohol polyoxyethylene ether, 1 part alkyl glycoside, 2 parts sodium dodecylbenzenesulfonate, 2 parts modified nano Fe3O4, 3 parts modified microporous starch, 1.5 parts methylcellulose, 0.5 parts benzotriazole, and 0.5 parts organosilicon defoamer; the modified nano Fe3O4 was prepared in Example 1, and the modified microporous starch was prepared in Example 2.

[0027] The preparation method of the above-mentioned high-penetration modified water-based paint remover includes the following steps: Deionized water was added to a stainless steel reactor, and the reactor temperature was controlled at 45°C. Methylcellulose was slowly added and stirred for 15 minutes until completely dissolved and transparent. Then, sodium dodecylbenzenesulfonate, fatty alcohol polyoxyethylene ether, alkyl glycoside, and organosilicon defoamer were added and stirred for 15 minutes until evenly dispersed. Benzyl alcohol was slowly added and stirred to emulsify into a milky white microemulsion. Modified nano-Fe3O4 and modified microporous starch were added and stirred for 15 minutes. Formic acid was slowly added and the temperature was controlled at <60°C. The mixture was stirred for 10 minutes, followed by the addition of benzotriazole and stirring for 15 minutes. The pH was adjusted to 2.0~3.0, and the mixture was cooled to room temperature to obtain the high-penetration modified water-based paint remover.

[0028] Comparative Example 1 A highly permeable modified water-based paint remover comprises 48 parts deionized water, 35 parts benzyl alcohol, 4 parts formic acid, 1.5 parts fatty alcohol polyoxyethylene ether, 1 part alkyl glycoside, 2 parts sodium dodecylbenzenesulfonate, 3 parts modified microporous starch, 1.5 parts methylcellulose, 0.5 parts benzotriazole, and 0.5 parts organosilicon defoamer; the modified microporous starch is prepared in Example 2.

[0029] The preparation method of the above-mentioned high-penetration modified water-based paint remover is the same as that in Example 5, except that modified nano Fe3O4 is not added.

[0030] Comparative Example 2 A highly permeable modified water-based paint remover comprises 48 parts deionized water, 35 parts benzyl alcohol, 4 parts formic acid, 1.5 parts fatty alcohol polyoxyethylene ether, 1 part alkyl glycoside, 2 parts sodium dodecylbenzenesulfonate, 2 parts modified nano-Fe3O4, 3 parts modified microporous starch, 1.5 parts methylcellulose, 0.5 parts benzotriazole, and 0.5 parts organosilicon defoamer; the modified nano-Fe3O4 is prepared in Example 1.

[0031] The preparation method of the above-mentioned high-penetration modified water-based paint remover is the same as that in Example 5, except that modified microporous starch is not added.

[0032] Performance testing The high-penetration modified water-based paint removers prepared in Example 5 and Comparative Examples 1 and 2 were subjected to basic physicochemical property tests and paint removal performance tests.

[0033] I. Physicochemical Performance Testing (1) Appearance inspection: Take 50mL of sample and place it in a 100mL colorless transparent glass beaker. Observe it visually under natural light and record the color, state, whether it is layered, and whether there is any precipitate. (2) pH value determination: After the pH meter is calibrated with a standard buffer solution, it is directly inserted into the sample for measurement at 25±1℃. The measurement is repeated 3 times and the average value is taken. (3) Density determination: The specific gravity bottle method is used. The mass of the empty specific gravity bottle is accurately weighed, and then the specific gravity bottle is filled with the sample and weighed again. ρ=(m2-m1) / V is calculated, where m1 is the mass of the empty bottle, m2 is the mass after filling with the sample, and V is the volume of the specific gravity bottle. (4) Viscosity measurement: The rotational viscometer method was used at 25±0.5℃, with a No. 2 rotor at 30 rpm. The reading was taken after stabilization. (5) Determination of solid content: Weigh 2-3g of sample into a pre-weighed weighing bottle, dry at 105℃ to constant weight, and calculate the solid content = (mass after drying / mass before drying) × 100%; (6) Thermal storage stability: Place the sample in an oven at 54±1℃ and let it stand for 7 days. Observe whether there is any layering, precipitation, or color change. (7) Low temperature stability: Place the sample in a -5±1℃ refrigerator and let it stand for 24 hours. Take it out and let it return to room temperature. Observe whether there is stratification, crystallization or flocculation. The results are shown in Table 1 below.

[0034] Table 1. Test results of the physicochemical properties of the high-penetration modified water-based paint remover As can be seen from the data in Table 1, the pH values ​​of the three groups of samples are all within the range of 2 to 3, ensuring the comparability of paint removal activity; Example 5 has a slightly higher overall density due to the addition of magnetic particles and temperature-sensitive microspheres; Example 5 has a slightly higher viscosity, mainly due to the thickening effect of methylcellulose and temperature-sensitive microspheres; after heat storage, sample A showed slight precipitation, and the magnetic particles slightly settled, which could be redispersed after stirring.

[0035] II. Paint Removal Performance Test The test sample uses a 50mm×50mm×2mm Q235 carbon steel plate substrate. After degreasing, derusting, sanding (400# sandpaper), acetone cleaning, and drying, the coating system in Table 2 below is applied and cured. Then, the coating adhesion is tested according to GB / T 5210-2006. The coating adhesion of the test sample is required to be ≥5MPa. Table 2 Coating parameters of the test samples (1) Paint stripping rate test: At 70℃, the sample was completely immersed in the paint stripper. In Example 5, a low-frequency alternating magnetic field (30Hz, magnetic field strength 0.05T) was applied. In Comparative Example 1 and Comparative Example 2, no magnetic field was applied. The sample was taken out and observed every 0.5 minutes. The paint film was gently scraped with a plastic scraper. The paint film could be peeled off in one piece. The paint stripping was completed when the exposed area of ​​the substrate was ≥95%. The time required from immersion to completion of paint stripping was recorded. Three samples were tested for each type of paint film, and the average value was taken. The results are shown in Table 3 below.

[0036] Table 3. Test results of paint removal rate of high-penetration modified water-based paint remover (unit: min) As can be seen from the data in Table 3, Example 5 showed a significantly better paint removal rate than the comparative examples for all types of paint films. Comparative Example 1 had the slowest rate, indicating that the modified nano Fe3O4 magnetic active penetration had a significant effect on dense paint films (epoxy, powder). Comparative Example 2 had a moderate rate, indicating that the modified microporous starch temperature-sensitive release mechanism also made a significant contribution to the relatively loose paint films such as alkyd and acrylic.

[0037] (2) Paint stripping efficiency test: The carbon steel plate substrate was dried at 105℃ to constant weight and weighed (m0). The carbon steel plate substrate was dried at 105℃ and weighed (m1). Coating mass = m1-m0. The four types of paint film test samples were immersed in paint stripper at 70℃ for a fixed time (5 min for alkyd paint, 8 min for acrylic paint, 8 min for epoxy paint, and 10 min for powder coating), rinsed with high pressure water gun (pressure 5 MPa, distance 15 cm, 30 s), dried at 105℃ to constant weight, and the mass of the sample after paint stripping (m2) was weighed. The paint stripping efficiency η = [(m1-m2) / (m1-m0)] × 100% was calculated. Three samples were tested for each type of paint film, and the average value was taken. The results are shown in Table 4 below.

[0038] Table 4. Test results of paint removal efficiency of high-penetration modified water-based paint remover As can be seen from the data in Table 4, Example 5 showed a paint removal efficiency of over 90% for all four types of paint films, while Comparative Example 1 showed a paint removal efficiency of over 90% only for alkyd paint, and Comparative Example 2 showed a paint removal efficiency of over 90% only for alkyd paint and acrylic paint. This shows that the two additives have a significant synergistic effect. Adding one of them alone has a limited effect on efficiency improvement, while adding both at the same time achieves the optimal effect.

[0039] (3) Residual paint film assessment: The residual paint film of the test sample after paint removal was calculated by weighing. The residual amount per unit area = (mass of the sample after paint removal - mass of the substrate) / sample area (g / m²) 2 The data obtained is shown in Table 5 below.

[0040] Table 5. Evaluation results of residual paint film of high-penetration modified water-based paint remover As can be seen from the data in Table 5, Example 5 had the highest surface cleanliness, with a residue level of only 18% of that in Comparative Example 1. This indicates that the micro-disturbance mechanical force of the magnetic particles helps to remove difficult-to-remove residual paint spots. Powder coatings, due to their high crosslinking density, have a relatively high residue level.

[0041] (4) Substrate corrosion test Static immersion corrosion test: 50mm×25mm×2mm Q235 carbon steel, 6061 aluminum alloy, and H62 brass substrates were selected. The substrates were polished (400#→800#→1200# sandpaper), degreased (acetone ultrasonic cleaning for 10 min), dried, and weighed (accuracy 0.0001g). The substrates were then immersed in a 70℃ paint remover for 8 hours (simulating the paint removal time of 8 batches). After removal, the substrates were rinsed with deionized water. For carbon steel substrates, ultrasonic cleaning with 10% ammonium citrate solution for 5 min removed corrosion products. For aluminum alloy substrates, immersion in 70% nitric acid solution for 1 min removed the substrates. The substrates were dried and weighed. Corrosion weight loss and corrosion rate were calculated: Corrosion weight loss = pre-test mass - post-test mass; Corrosion rate (mm / year) = (Corrosion weight loss × 8.76 × 10⁻¹¹) / (Corrosion weight loss × 8.76 × 10⁻¹¹) 7 () / (sample density × area × time in hours), with 3 parallel samples for each material, and the results are shown in Table 6 below.

[0042] Table 6. Substrate corrosion test results of high-penetration modified water-based paint remover As can be seen from the data in Table 6, the corrosion rates of all three groups of samples are ≤0.011 mm / year, which meets the industrial requirement of ≤0.01 mm / year (carbon steel slightly exceeds this, but it is within an acceptable range). Example 5 has the lowest corrosion rate, which is about 25-30% lower than that of Comparative Example 1. The corrosion rate is: carbon steel > aluminum alloy > brass, which is consistent with the order of metal activity. The reason why Example 5 has the lowest corrosion rate is that the PASP layer on the surface of the modified nano Fe3O4 particles has a metal chelating effect, forming a protective film. The microcrystalline wax component of the modified microporous starch forms a hydrophobic layer on the metal surface, which physically isolates the acid.

[0043] (5) Salt spray corrosion test According to GB / T 10125-2021, artificial atmosphere corrosion tests were conducted on Q235 carbon steel samples after paint removal and those without paint removal. The NaCl solution concentration was 5%, pH value was 6.5~7.2, test temperature was 35℃, and salt spray deposition was 1-2 mL / (80cm²). 2 • h), test time: 72h, observe the rust area, and rate according to GB / T 6461; the results are shown in Table 7 below.

[0044] Table 7. Salt spray corrosion test results of high-penetration modified water-based paint remover The data in Table 7 show that the salt spray corrosion resistance of the substrate treated in Example 5 is better than that of Comparative Example 1 and Comparative Example 2, indicating that the modified nano Fe3O4 and modified microporous starch have a certain protective effect on the substrate, rather than simply causing corrosion.

[0045] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0046] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A high-penetration modified water-based paint remover, characterized in that, The raw materials include the following parts by weight: 45-50 parts deionized water, 30-40 parts benzyl alcohol, 3-5 parts formic acid, 1-3 parts composite penetrant, 1-3 parts sodium dodecylbenzenesulfonate, 1-3 parts modified nano Fe3O4, 2-4 parts modified microporous starch, 1-2 parts thickener, 0.4-0.6 parts corrosion inhibitor, and 0.4-0.6 parts defoamer; The modified nano Fe3O4 was first prepared by co-precipitation, then a dense SiO2 shell was formed on the surface of Fe3O4 by hydrolysis of tetraethyl orthosilicate, and the surface was treated with a silane coupling agent. Finally, polyaspartic acid was grafted onto the surface of the SiO2 layer. The modified microporous starch is prepared by first using an enzymatic hydrolysis method, then loading molten microcrystalline wax and synergistic agents into the micropores through a vacuum impregnation method, and finally cooling and solidifying to achieve solid wax sealing of the pores. The synergistic agent is a compound of isooctanol phosphate and D-limonene.

2. The high-penetration modified water-based paint remover according to claim 1, characterized in that, The composite penetrant is a mixture of fatty alcohol polyoxyethylene ether and alkyl glycoside in a mass ratio of 1:1~2.

3. The high-penetration modified water-based paint remover according to claim 1, characterized in that, The thickener is methylcellulose, the corrosion inhibitor is benzotriazole, and the defoamer is an organosilicone defoamer.

4. The high-penetration modified water-based paint remover according to claim 1, characterized in that, The preparation method of the modified nano Fe3O4 includes the following steps: A. Dissolve ferric chloride and ferrous ammonium sulfate in deionized water at a mass ratio of 2:1, purge with nitrogen to remove oxygen, heat to 80°C, quickly add ammonia to adjust the pH to 10-11, mature at 80°C for 20-40 min, separate the product with a magnet, wash with deionized water until neutral, and vacuum dry to obtain nano Fe3O4. B. Add nano Fe3O4 to a mixed solvent of ethanol and water and disperse it by ultrasonication. Adjust the pH to 10-11 with ammonia water and stir for 20-40 min. Slowly add tetraethyl orthosilicate and react at room temperature for 18-24 h. Then add 3-aminopropyltriethoxysilane and continue to react for 0.5-1.5 h. Separate the product with a magnet, wash it three times with ethanol, and dry it under vacuum to obtain SiO2-coated nano Fe3O4. C. Polyaspartic acid was dissolved in MES buffer solution at pH 4-5, and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide were added. The mixture was activated at room temperature for 20-30 min. The SiO2-coated nano-Fe3O4 was dispersed in the activated polyaspartic acid solution and ultrasonically dispersed until uniform. The mixture was stirred at room temperature for 8-12 h. The product was separated by magnetic separation, washed three times alternately with deionized water and ethanol, and vacuum dried to obtain modified nano-Fe3O4.

5. The high-penetration modified water-based paint remover according to claim 4, characterized in that, The mass ratio of nano-Fe3O4, tetraethyl orthosilicate, and 3-aminopropyltriethoxysilane is 4:1:0.

2.

6. The high-penetration modified water-based paint remover according to claim 4, characterized in that, The mass ratio of the SiO2-coated nano-Fe3O4, polyaspartic acid, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide is 1:0.5:0.2:0.

05.

7. The high-penetration modified water-based paint remover according to claim 1, characterized in that, The method for preparing the modified microporous starch includes the following steps: (1) Disperse corn starch in an acetate-sodium acetate buffer solution with pH 5.5-6 to prepare a starch milk of 10-15 wt%. Add saccharifying enzyme and α-amylase and perform enzymatic hydrolysis in a water bath at 55℃ for 12-20 h. After the enzymatic hydrolysis is completed, adjust the pH to 9-10 with NaOH solution to terminate the reaction. Filter and collect the precipitate, wash it three times alternately with deionized water and anhydrous ethanol, and dry it under vacuum at 50℃ to obtain microporous starch. (2) Melt the microcrystalline wax in an oven at 70~80℃, then mix the melted microcrystalline wax with isooctanol phosphate, D-limonene and Tween 80 in proportion, stir evenly to form a liquid core material mixture, add microporous starch to the core material mixture, evacuate to -0.09MPa, hold pressure for 20~40min and then release the vacuum, repeat the evacuation and release operation 2~3 times; (3) Take out the impregnated product, cool it at room temperature, wash the surface quickly with cold ethanol to remove the unimpregnated free core material, dry it at a low temperature below 40°C, pass it through a 200-mesh sieve, and modify the microporous starch.

8. The high-penetration modified water-based paint remover according to claim 7, characterized in that, The amount of saccharifying enzyme added is 1.0~1.5% of the total mass of corn starch, and the amount of α-amylase added is 0.5~1.0% of the total mass of corn starch.

9. The high-penetration modified water-based paint remover according to claim 7, characterized in that, The core material is a mixture of microcrystalline wax, isooctanol phosphate, D-limonene and Tween-80 in a mass ratio of 15:3:2:1, and the mass ratio of microporous starch to the core material is 1:2~3.

10. The method for preparing the high-penetration modified water-based paint remover according to any one of claims 1 to 9, characterized in that, Includes the following steps: Add deionized water to a stainless steel reactor, control the reactor temperature at 40-50℃, slowly add methylcellulose, and stir for 10-20 minutes until completely dissolved and transparent. Then add sodium dodecylbenzenesulfonate, composite penetrant and defoamer, and stir for 10-20 minutes until evenly dispersed. Slowly add benzyl alcohol, and stir to emulsify into a milky white microemulsion. Add modified nano Fe3O4 and modified microporous starch, and stir for 10-20 minutes. Slowly add formic acid, control the temperature at <60℃, and stir for 5-15 minutes. Then add a slow-release agent, stir for 10-20 minutes, adjust the pH to 2.0-3.0, and cool to room temperature to obtain the high-penetration modified water-based paint remover.

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