Rapeseed oil phosphate emulsified acrylate water-based metal antirust coating and preparation method thereof

Abstract

The application discloses rapeseed oil phosphate emulsified acrylate water-based metal antirust paint and a preparation method thereof. The rapeseed oil phosphate emulsified acrylate water-based metal antirust paint comprises the following components in parts by weight: modified acrylate emulsion 55-75 parts, antirust pigment and filler 18-30 parts, functional additive 3-8 parts and deionized water 10-20 parts. The preparation raw materials of the modified acrylate emulsion comprise the following components in parts by weight: acrylate comonomer 35-45 parts, rapeseed oil phosphate 1.5-3.0 parts, initiator 0.2-0.5 parts, pH buffer 0.1-0.3 parts and deionized water 50-60 parts. The modified acrylate emulsion is prepared by using the rapeseed oil phosphate as a reaction-type emulsifier through a semi-continuous seed emulsion polymerization process, the emulsion solid content is 45+ / -2%, and the pH value is 7.0-8.5. The rapeseed oil phosphate is an anionic reaction emulsifier prepared by modifying rapeseed oil through epoxidation and phosphate esterification. The application is applied to the technical field of water-based industrial antirust paint compositions.

Description

Technical Field

[0001] This invention belongs to the field of water-based industrial anti-rust coating technology, and specifically relates to a rapeseed oil phosphate ester emulsified acrylic water-based metal anti-rust coating and its preparation method. It is suitable for anti-corrosion and anti-rust coating of ferrous metal substrates such as steel, carbon steel, and cast iron, and can be widely used in mechanical equipment, steel structures, hardware components, pipeline facilities and other fields. Background Technology

[0002] Traditional metal anti-rust coatings are mostly solvent-based, posing safety hazards such as high VOC content, serious environmental pollution, high irritation during application, and flammability and explosiveness, which do not conform to the trend of green and environmentally friendly industrial development. Water-based acrylic coatings, with their advantages of low cost, good film-forming properties, excellent weather resistance, and convenient application, have become the mainstream product to replace solvent-based anti-rust coatings.

[0003] Currently, most commercially available water-based acrylic emulsions use traditional chemical emulsifiers such as sodium dodecylbenzenesulfonate and fatty alcohol polyoxyethylene ether, which have several drawbacks: First, traditional emulsifiers have poor compatibility with acrylic resins and easily migrate to the coating surface after film formation, resulting in a significant decrease in the coating's water resistance and salt spray resistance, and a short rust-proof lifespan; second, residues of small-molecule emulsifiers can easily cause coating blistering, peeling, and loss of gloss, affecting the overall performance of the paint film; third, conventional emulsions lack functional rust-preventing groups and rely solely on added rust-preventing pigments to achieve anti-corrosion effects, resulting in large amounts of pigment added, uneven dispersion, and a tendency to settle and chalk. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and to provide a rapeseed oil phosphate ester emulsified acrylate water-based metal anti-rust coating and its preparation method.

[0005] The technical solution adopted in this invention is as follows: This invention includes a rapeseed oil phosphate ester emulsified acrylic ester water-based metal anti-rust coating and its preparation method. The rapeseed oil phosphate ester emulsified acrylic ester water-based metal anti-rust coating, by weight, includes the following components: 55-75 parts of modified acrylic ester emulsion, 18-30 parts of anti-rust pigments and fillers, 3-8 parts of functional additives, and 10-20 parts of deionized water. The raw materials for preparing the modified acrylate emulsion include, by weight: 35-45 parts of acrylate comonomer, 1.5-3.0 parts of rapeseed oil phosphate, 0.2-0.5 parts of initiator, 0.1-0.3 parts of pH buffer, and 50-60 parts of deionized water; wherein, the modified acrylate emulsion is prepared by a semi-continuous seed emulsion polymerization process using rapeseed oil phosphate as a reactive emulsifier, with an emulsion solid content of 45±2% and a pH value of 7.0-8.5; the rapeseed oil phosphate is an anionic reactive emulsifier obtained by epoxidation and phosphorylation modification of rapeseed oil, with an effective phosphorus content ≥8%, a hydrophilic-lipophilic balance value (HLB) of 12-14, and possesses emulsifying and dispersing, metal complexing and passivation, and film-forming toughening functions.

[0006] Furthermore, the acrylate comonomer includes a hard monomer and a soft monomer, wherein the hard monomer is at least one of methyl methacrylate and styrene, and the soft monomer is at least one of butyl acrylate and isooctyl acrylate, with a mass ratio of hard monomer to soft monomer of 1:1.2-1:1.5; the acrylate comonomer also contains 0.5-1.0 parts of a functional monomer, which is an acrylic monomer, used to improve the adhesion and crosslinking properties of the modified acrylate emulsion.

[0007] Furthermore, the acrylate comonomer also includes a phosphorus-containing comonomer to enhance the intrinsic phosphating ability of the modified acrylate emulsion. The phosphorus-containing comonomer is at least one of methacryloyloxyethyl phosphate, vinylphosphonic acid, and hydroxyethyl methacrylate phosphate, and its addition amount accounts for 0.5%-2.0% of the total weight of the comonomer. The phosphorus-containing comonomer works synergistically with rapeseed oil phosphate to increase the density of phosphate groups in the polymer chain, further improving the chemical bonding ability with the metal substrate and the density of the phosphating film, and significantly improving the salt spray resistance of the coating.

[0008] Furthermore, the initiator is one of ammonium persulfate and sodium persulfate, and the pH buffer is one of sodium bicarbonate and ammonium bicarbonate. The pH buffer is used to stabilize the pH value of the polymerization reaction system and prevent emulsion gelation.

[0009] Furthermore, the rust-preventive pigments and fillers are a chromium-free compound system, composed of zinc phosphate, aluminum tripolyphosphate, talc, and mica powder in a mass ratio of 2:1:1.5:1. Zinc phosphate and aluminum tripolyphosphate are functional rust-preventive pigments that can synergistically modify the phosphate groups in the acrylic emulsion to form a multi-layer passivation protection system. Talc and mica powder are extender pigments that can improve the density, impermeability, and mechanical strength of the paint film.

[0010] Furthermore, the functional additives include, by weight: 0.8-1.5 parts of dispersant, 0.2-0.5 parts of wetting agent, 0.3-0.6 parts of defoamer, 1.0-2.0 parts of film-forming aid, 0.4-0.8 parts of rheology modifier, and 0.1-0.3 parts of bactericide.

[0011] Furthermore, the dispersant is a polyacrylate aqueous dispersant, the wetting agent is an organosilicon wetting agent, the defoamer is a mineral oil defoamer, the film-forming aid is propylene glycol methyl ether acetate, the rheology modifier is a polyurethane thickening rheology modifier, and the bactericide is an isothiazolinone environmentally friendly bactericide.

[0012] Furthermore, the preparation method of the rapeseed oil phosphate emulsified acrylate waterborne metal anti-rust coating includes the following steps: S1. Pre-emulsion preparation: Take half of the deionized water and all of the rapeseed oil phosphate according to the ratio and add them to the emulsification kettle. Stir at room temperature for 10-15 minutes until completely dissolved. Add the acrylate comonomer and functional monomer, and homogenize at high speed for 20-30 minutes to obtain a uniform and stable milky white pre-emulsion. S2. Preparation of base solution: Add the remaining deionized water and pH buffer from the emulsion polymerization to the polymerization reactor, stir evenly, raise the temperature to 78-82℃, add 1 / 3 of the initiator aqueous solution, and keep the temperature for 5-8 minutes. S3. Post-polymerization treatment at constant temperature: Add 1 / 4 of the pre-emulsion dropwise to the polymerization reactor at a uniform rate, and keep the reaction at the temperature for 15-20 min to form a blue fluorescent seed emulsion; then add the remaining pre-emulsion and the remaining initiator aqueous solution dropwise at a uniform rate, controlling the dropwise addition time to 3-4 h, and maintaining the reaction temperature at 80±2℃ during the dropwise addition process. After the dropwise addition is completed, raise the temperature to 83-85℃ and keep the reaction at the temperature for 1 h, then lower the temperature to below 40℃, adjust the pH value to 7.0-8.5 with ammonia water, filter and discharge to obtain the modified acrylate emulsion; S4. Coating preparation: Add metered deionized water, dispersant, wetting agent, and half of the defoamer to the mixing tank, and stir at low speed for 5 minutes until the additives are evenly dispersed; add rust-preventive pigments and fillers in batches, disperse at high speed for 25-35 minutes, and then grind them with a sand mill until the slurry fineness is ≤30μm, and set aside; slowly add the prepared modified acrylic emulsion to the ground slurry, and stir at medium speed for 15 minutes; add film-forming aid, rheology aid, remaining defoamer, and bactericide in sequence, stir evenly, adjust the coating viscosity to 80-120s, filter and discharge to obtain the finished metal anti-rust coating.

[0013] Furthermore, the application of the rapeseed oil phosphate emulsified acrylate waterborne metal anti-rust coating obtained by the above preparation method in the anti-corrosion coating of carbon steel, cast iron, and steel structure metal substrates.

[0014] The beneficial effects of this invention are: 1. Innovative core emulsifier with multiple functions: This invention abandons traditional small-molecule chemical emulsifiers and uses naturally modified rapeseed oil phosphate ester as a reactive emulsifier. Its molecules can participate in the polymerization reaction of acrylate and are firmly bonded to the resin molecular chain, completely solving the migration and precipitation problem of traditional emulsifiers and significantly improving the water resistance and weather resistance of the paint film. At the same time, the phosphate groups in the rapeseed oil phosphate ester molecules can undergo phosphating complexation reaction with the metal substrate to form a dense passivation film, giving the emulsion intrinsic anti-rust properties from the source, reducing the amount of anti-rust pigments used, and lowering the cost of coatings.

[0015] 2. Dual-layer anti-rust system with excellent anti-corrosion performance: This invention constructs a dual protection system of "intrinsic phosphating anti-rust emulsion + physicochemical anti-rust without chromium pigments and fillers". The active phosphorus groups of rapeseed oil phosphate achieve passivation and sealing of metal surface. Zinc phosphate and aluminum tripolyphosphate synergistically release anti-rust ions to block the micropores of the paint film. Mica powder and talc powder form a dense barrier layer to effectively block the penetration of water vapor and oxygen. The coating's salt spray resistance is greatly improved, and long-term anti-rust of steel substrates can be achieved.

[0016] 3. Environmentally friendly and safe, suitable for green production: The core raw material, rapeseed oil, is a natural and renewable resource with good biodegradability. The overall VOC content of the coating is extremely low, with no heavy metals or toxic solvents, meeting the national environmental protection standards for water-based coatings. The preparation process is simple and the reaction is mild, with no waste discharge. There is no irritating odor during construction, ensuring high safety.

[0017] 4. Excellent overall performance of the coating film: The long-chain alkyl structure of rapeseed oil can improve the flexibility and impact resistance of acrylic ester coating film, solving the problem of traditional acrylic ester coating film being brittle and prone to cracking; the coating has extremely strong adhesion to metal substrates such as carbon steel and cast iron, the film is uniform and dense, and it has excellent water resistance, acid and alkali resistance, and aging resistance. It has good storage stability and does not exhibit stratification, sedimentation, or gelation after long-term storage.

[0018] 5. This invention further introduces phosphorus-containing comonomers (such as methacryloyloxyethyl phosphate, etc.) to form a dual phosphating functional system with rapeseed oil phosphate emulsifier. The phosphorus-containing comonomers copolymerize in the acrylate backbone, significantly increasing the phosphate density in the polymer, enhancing the chelation and passivation reaction with the metal substrate, and improving the salt spray resistance of the coating from the conventional 120h to more than 200h, while not affecting the emulsion stability and the flexibility of the paint film. Detailed Implementation

[0019] In this embodiment, the present invention includes a rapeseed oil phosphate emulsion acrylate waterborne metal anti-rust coating and its preparation method. The rapeseed oil phosphate emulsion acrylate waterborne metal anti-rust coating comprises, by weight, the following components: 55-75 parts of modified acrylate emulsion, 18-30 parts of anti-rust pigments and fillers, 3-8 parts of functional additives, and 10-20 parts of deionized water. In this embodiment, the raw materials for preparing the modified acrylate emulsion include, by weight: 35-45 parts of acrylate comonomer, 1.5-3.0 parts of rapeseed oil phosphate, 0.2-0.5 parts of initiator, 0.1-0.3 parts of pH buffer, and 50-60 parts of deionized water; wherein, the modified acrylate emulsion is prepared by a semi-continuous seed emulsion polymerization process using rapeseed oil phosphate as a reactive emulsifier, with an emulsion solid content of 45±2% and a pH value of 7.0-8.5; the rapeseed oil phosphate is an anionic reactive emulsifier obtained by epoxidation and phosphorylation modification of rapeseed oil, with an effective phosphorus content ≥8%, a hydrophilic-lipophilic balance value (HLB) of 12-14, and possesses emulsification and dispersion, metal complexation and passivation, and film-forming toughening functions.

[0020] In this embodiment, the acrylate comonomer includes a hard monomer and a soft monomer, wherein the hard monomer is at least one of methyl methacrylate and styrene, and the soft monomer is at least one of butyl acrylate and isooctyl acrylate, and the mass ratio of the hard monomer to the soft monomer is 1:1.2-1:1.5; the acrylate comonomer also contains 0.5-1.0 parts of a functional monomer, which is an acrylic monomer, used to improve the adhesion and crosslinking properties of the modified acrylate emulsion.

[0021] In this embodiment, the acrylate comonomer further includes a phosphorus-containing comonomer to enhance the intrinsic phosphating ability of the modified acrylate emulsion. The phosphorus-containing comonomer is at least one of methacryloyloxyethyl phosphate, vinylphosphonic acid, and hydroxyethyl methacrylate phosphate, and its addition amount accounts for 0.5%-2.0% of the total weight of the comonomer. The phosphorus-containing comonomer works synergistically with rapeseed oil phosphate to increase the density of phosphate groups in the polymer chain, further improving the chemical bonding ability with the metal substrate and the density of the phosphating film, and significantly improving the salt spray resistance of the coating.

[0022] In this embodiment, the initiator is one of ammonium persulfate and sodium persulfate, and the pH buffer is one of sodium bicarbonate and ammonium bicarbonate. The pH buffer is used to stabilize the pH value of the polymerization reaction system and prevent emulsion gelation.

[0023] In this embodiment, the anti-rust pigment and filler is a chromium-free compound system, which is composed of zinc phosphate, aluminum tripolyphosphate, talc powder and mica powder in a mass ratio of 2:1:1.5:1. Zinc phosphate and aluminum tripolyphosphate are functional anti-rust pigments that can synergistically modify the phosphate groups in the acrylic emulsion to form a multi-layer passivation protection system. Talc powder and mica powder are extender pigments that can improve the density, impermeability and mechanical strength of the paint film.

[0024] In this embodiment, the functional additives include, by weight, 0.8-1.5 parts of dispersant, 0.2-0.5 parts of wetting agent, 0.3-0.6 parts of defoamer, 1.0-2.0 parts of film-forming aid, 0.4-0.8 parts of rheology modifier, and 0.1-0.3 parts of bactericide.

[0025] In this embodiment, the dispersant is a polyacrylate aqueous dispersant, the wetting agent is an organosilicon wetting agent, the defoamer is a mineral oil defoamer, the film-forming aid is propylene glycol methyl ether acetate, the rheology modifier is a polyurethane thickening rheology modifier, and the bactericide is an isothiazolinone environmentally friendly bactericide.

[0026] In this embodiment, the preparation method of the rapeseed oil phosphate emulsified acrylate waterborne metal anti-rust coating includes the following steps: S1. Pre-emulsion preparation: According to the raw material ratio for the preparation of modified acrylate emulsion, take half of the deionized water and all of the rapeseed oil phosphate and add them to the emulsification kettle. Stir at room temperature for 10-15 minutes until completely dissolved. Add the acrylate comonomer (containing phosphorus comonomer) and functional monomers. Homogenize at high speed for 20-30 minutes to obtain a uniform and stable milky white pre-emulsion. S2. Preparation of base solution: Add the remaining deionized water and pH buffer from the emulsion polymerization to the polymerization reactor, stir evenly, raise the temperature to 78-82℃, add 1 / 3 of the initiator aqueous solution, and keep the temperature for 5-8 minutes. S3. Post-polymerization treatment at constant temperature: Add 1 / 4 of the pre-emulsion dropwise to the polymerization reactor at a uniform rate, and keep the reaction at the temperature for 15-20 min to form a blue fluorescent seed emulsion; then add the remaining pre-emulsion and the remaining initiator aqueous solution dropwise at a uniform rate, controlling the dropwise addition time to 3-4 h, and maintaining the reaction temperature at 80±2℃ during the dropwise addition process. After the dropwise addition is completed, raise the temperature to 83-85℃ and keep the reaction at the temperature for 1 h, then lower the temperature to below 40℃, adjust the pH value to 7.0-8.5 with ammonia water, filter and discharge to obtain the modified acrylate emulsion; S4. Coating preparation: Add metered deionized water (i.e., 10-20 parts of deionized water in the anti-rust coating), dispersant, wetting agent, and half of the defoamer to the mixing tank, and stir at low speed for 5 minutes until the additives are evenly dispersed; add anti-rust pigments and fillers in batches, disperse at high speed for 25-35 minutes, and then grind them with a sand mill until the slurry fineness is ≤30μm, and set aside; slowly add the prepared modified acrylic emulsion to the ground slurry, and stir at medium speed for 15 minutes; add film-forming aid, rheology aid, remaining defoamer, and bactericide in sequence, stir evenly, and adjust the coating viscosity to 80-120s (Ford-4 cup, 25℃), filter and discharge to obtain the finished metal anti-rust coating.

[0027] In this embodiment, an application of a rapeseed oil phosphate emulsified acrylate waterborne metal anti-rust coating obtained by the preparation method is described in the anti-corrosion coating of carbon steel, cast iron, and steel structure metal substrates.

[0028] Vegetable oil phosphates are environmentally friendly reactive emulsifiers that combine surface activity and rust prevention. Rapeseed oil phosphates, prepared from natural, renewable rapeseed oil through esterification and phosphorylation modification, contain lipophilic long-chain alkyl groups, hydrophilic phosphate groups, and reactive double bonds that can participate in polymerization in their molecular structure. Compared to traditional chemical emulsifiers, they exhibit good biodegradability, produce no secondary pollution, and the phosphate groups can undergo complexation and phosphating reactions with the metal substrate surface to form a dense passivation protective film, achieving both physical barrier and chemical rust prevention. Currently, there is no complete technical solution for preparing acrylic emulsions using rapeseed oil phosphates as a dedicated emulsifier and for compounding with functional components to prepare high-performance metal rust-preventive coatings.

[0029] To address the shortcomings of existing technologies, this invention uses rapeseed oil phosphate ester to replace traditional emulsifiers in the preparation of acrylic emulsions, imparting rust-preventive properties to the emulsion from the source of the base material. Then, it is compounded with environmentally friendly rust-preventive pigments, fillers, and functional additives to prepare a water-based metal rust-preventive coating with low VOC, high corrosion resistance, and excellent adhesion, solving the industry pain points of traditional water-based rust-preventive coatings such as poor salt spray resistance, weak adhesion, and insufficient environmental protection.

[0030] To better illustrate the performance of this invention, three sets of experimental groups were conducted for comparison: Experimental group 1 1. Preparation of modified acrylate emulsion Raw material ratio: 22 parts butyl acrylate, 16 parts methyl methacrylate, 0.8 parts acrylic acid, 1.0 part methacryloyloxyethyl phosphate, 2.2 parts rapeseed oil phosphate emulsifier, 0.3 parts ammonium persulfate, 0.2 parts sodium bicarbonate, and 57.7 parts deionized water.

[0031] Preparation process: Following the steps S1-S3 above, a pre-emulsion is prepared, followed by seed polymerization, constant temperature dropwise addition, and pH adjustment after post-treatment to obtain a modified acrylate emulsion with a solid content of 45% and a pH of 7.8.

[0032] 2. Preparation of anti-rust coatings Coating formulation: 65 parts of the above modified acrylic emulsion, 22 parts of compounded rust-inhibiting pigments and fillers (8 parts of zinc phosphate, 4 parts of aluminum tripolyphosphate, 6 parts of talc, and 4 parts of mica powder), 1.2 parts of dispersant, 0.3 parts of wetting agent, 0.4 parts of defoamer, 1.5 parts of film-forming aid, 0.6 parts of rheology modifier, 0.2 parts of bactericide, and 14.8 parts of deionized water.

[0033] Following process steps S4, the coating is dispersed, ground, mixed, and filtered to obtain the finished anti-rust coating.

[0034] Experimental group 2 1. Preparation of modified acrylate emulsion Raw material ratio: 24 parts isooctyl acrylate, 14 parts styrene, 0.6 parts acrylic acid, 0.8 parts vinylphosphonic acid, 2.8 parts rapeseed oil phosphate emulsifier, 0.4 parts sodium persulfate, 0.25 parts ammonium bicarbonate, and 57.15 parts deionized water.

[0035] The preparation process was the same as in Example 1, resulting in a modified acrylate emulsion with a solid content of 45% and a pH of 8.0.

[0036] 2. Preparation of anti-rust coatings Coating formulation: 70 parts of the above modified acrylic emulsion, 20 parts of compounded rust-inhibiting pigments and fillers (7 parts of zinc phosphate, 3.5 parts of aluminum tripolyphosphate, 5.5 parts of talc, and 4 parts of mica powder), 1.0 part of dispersant, 0.4 parts of wetting agent, 0.5 parts of defoamer, 1.8 parts of film-forming aid, 0.5 parts of rheology modifier, 0.2 parts of bactericide, and 15.6 parts of deionized water.

[0037] Following process steps S4, the coating is dispersed, ground, mixed, and filtered to obtain the finished anti-rust coating.

[0038] Experimental group comparison Comparative example (traditional emulsifier system) The rapeseed oil phosphate emulsifier of the present invention was replaced by the traditional sodium dodecylbenzene sulfonate emulsifier. The rest of the emulsion formulation, coating formulation and preparation process were the same as those of experimental group 1, and the comparative sample coating was obtained.

[0039] The coatings for experimental groups 1, 2, and the comparative group were sprayed onto ordinary carbon steel plates after grinding and rust removal. The dry film thickness was 35±5μm. After curing at room temperature for 7 days, performance testing was conducted. The testing standards were based on GB / T 25261-2010 and GB / T10125-2021.

[0040]

[0041] Test results show that the rust-preventive coating with phosphorus-containing copolymer monomers, after optimization according to the present invention, has its neutral salt spray resistance improved from 120h to over 250h, while other properties remain excellent.

[0042] Although the embodiments of the present invention are described with reference to actual solutions, they do not constitute a limitation on the meaning of the present invention. Modifications to the embodiments and combinations with other solutions based on this specification will be obvious to those skilled in the art.

Claims

1. A rapeseed oil phosphate ester emulsified acrylic ester water-based metal anti-rust coating, characterized in that: By weight, it includes the following components: 55-75 parts modified acrylic emulsion, 18-30 parts rust-inhibiting pigments and fillers, 3-8 parts functional additives, and 10-20 parts deionized water. The raw materials for preparing the modified acrylate emulsion include, by weight: 35-45 parts of acrylate comonomer, 1.5-3.0 parts of rapeseed oil phosphate, 0.2-0.5 parts of initiator, 0.1-0.3 parts of pH buffer, and 50-60 parts of deionized water; wherein, the acrylate comonomer also includes a phosphorus-containing comonomer, and the modified acrylate emulsion is prepared by a semi-continuous seed emulsion polymerization process using rapeseed oil phosphate as a reactive emulsifier, with an emulsion solid content of 45±2% and a pH value of 7.0-8.5; the rapeseed oil phosphate is an anionic reactive emulsifier obtained by epoxidation and phosphorylation modification of rapeseed oil, with an effective phosphorus content ≥8% and a hydrophilic-lipophilic balance (HLB) value of 12-14.

2. The rapeseed oil phosphate ester emulsified acrylic water-based metal anti-rust coating according to claim 1, characterized in that: The acrylate comonomer includes a hard monomer and a soft monomer, wherein the hard monomer is at least one of methyl methacrylate and styrene, and the soft monomer is at least one of butyl acrylate and isooctyl acrylate, and the mass ratio of the hard monomer to the soft monomer is 1:1.2-1:1.5; the acrylate comonomer also contains 0.5-1.0 parts of a functional monomer, which is an acrylic monomer.

3. The rapeseed oil phosphate ester emulsified acrylic water-based metal anti-rust coating according to claim 2, characterized in that: The phosphorus-containing comonomer is at least one of methacryloyloxyethyl phosphate, vinylphosphonic acid, and hydroxyethyl methacrylate phosphate, and its addition amount accounts for 0.5%-2.0% of the total weight of the comonomer.

4. The rapeseed oil phosphate ester emulsified acrylic water-based metal anti-rust coating according to claim 3, characterized in that: The initiator is one of ammonium persulfate and sodium persulfate, and the pH buffer is one of sodium bicarbonate and ammonium bicarbonate.

5. The rapeseed oil phosphate ester emulsified acrylic water-based metal anti-rust coating according to claim 4, characterized in that: The rust-preventive pigments and fillers are a chromium-free compound system, which is composed of zinc phosphate, aluminum tripolyphosphate, talc powder and mica powder in a mass ratio of 2:1:1.5:

1. Zinc phosphate and aluminum tripolyphosphate are functional rust-preventive pigments, and talc powder and mica powder are extender pigments.

6. The rapeseed oil phosphate ester emulsified acrylic water-based metal anti-rust coating according to claim 5, characterized in that: The functional additives include, by weight, 0.8-1.5 parts of dispersant, 0.2-0.5 parts of wetting agent, 0.3-0.6 parts of defoamer, 1.0-2.0 parts of film-forming aid, 0.4-0.8 parts of rheology modifier, and 0.1-0.3 parts of bactericide.

7. The rapeseed oil phosphate ester emulsified acrylic water-based metal anti-rust coating according to claim 6, characterized in that: The dispersant is a polyacrylate aqueous dispersant, the wetting agent is an organosilicon wetting agent, the defoamer is a mineral oil defoamer, the film-forming aid is propylene glycol methyl ether acetate, the rheology modifier is a polyurethane thickening rheology modifier, and the bactericide is an isothiazolinone environmentally friendly bactericide.

8. A method for preparing a rapeseed oil phosphate emulsified acrylic waterborne metal anti-rust coating as described in claim 6 or 7, characterized in that, Includes the following steps: S1. Pre-emulsion preparation: Take half of the deionized water and all of the rapeseed oil phosphate according to the ratio and add them to the emulsification kettle. Stir at room temperature for 10-15 minutes until completely dissolved. Add the acrylate comonomer and functional monomer, and homogenize at high speed for 20-30 minutes to obtain a uniform and stable milky white pre-emulsion. S2. Preparation of base solution: Add the remaining deionized water and pH buffer from the emulsion polymerization to the polymerization reactor, stir evenly, raise the temperature to 78-82℃, add 1 / 3 of the initiator aqueous solution, and keep the temperature for 5-8 minutes. S3. Post-polymerization treatment at constant temperature: Add 1 / 4 of the pre-emulsion dropwise to the polymerization reactor at a uniform rate, and keep the reaction at the temperature for 15-20 min to form a blue fluorescent seed emulsion; then add the remaining pre-emulsion and the remaining initiator aqueous solution dropwise at a uniform rate, controlling the dropwise addition time to 3-4 h, and maintaining the reaction temperature at 80±2℃ during the dropwise addition process. After the dropwise addition is completed, raise the temperature to 83-85℃ and keep the reaction at the temperature for 1 h, then lower the temperature to below 40℃, adjust the pH value to 7.0-8.5 with ammonia water, filter and discharge to obtain the modified acrylate emulsion; S4. Coating preparation: Add metered deionized water dispersant, wetting agent, and half of the defoamer to the mixing tank, and stir at low speed for 5 minutes until the additives are evenly dispersed; add rust-inhibiting pigments and fillers in batches, disperse at high speed for 25-35 minutes, and then grind the slurry to a fineness of ≤30μm, and set aside; slowly add the prepared modified acrylic emulsion to the ground slurry, and stir at medium speed for 15 minutes; add film-forming aid, rheology aid, remaining defoamer, and bactericide in sequence, stir evenly, adjust the coating viscosity to 80-120s, filter and discharge to obtain the finished metal anti-rust coating.

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