An aqueous alkyd resin dispersion and a preparation method thereof

Abstract

The present invention provides an aqueous alkyd dispersion which can be used for steel structure coatings, has a simple synthesis process, stable color paint storage, a fast film hardness development rate, and good water resistance and water whitening resistance of the film, and is suitable for light anti-corrosion coating of steel structures with the requirement of one-coat for both primer and topcoat. The aqueous alkyd resin dispersion comprises a monoethylenically unsaturated carboxyl monomer, an aromatic vinyl monomer, an (alkyl) acrylate monomer, an initiator, a branched-chain saturated fatty acid-modified alkyd resin intermediate, a pH regulator and deionized water. The present invention adjusts the weather resistance, water resistance and water whitening resistance by using branched-chain saturated fatty acids. The present invention synthesizes alkyd resins by using soybean oil acid containing conjugated double bonds and dehydrated castor oil acid with a high iodine value, thereby improving the drying rate of the film and the film hardness development rate.

Description

Technical Field

[0001] The present invention belongs to the technical field of coatings and relates to an aqueous alkyd resin dispersion and a preparation method thereof. Background Art

[0002] Alkyd resins are highly favored because of the easy availability and wide sources of raw materials and the high degree of formula adjustability. With the increasing emphasis of the public on the quality of life and the increasingly strict national and local environmental protection policies, the demand for environmentally friendly waterborne resins is becoming more urgent.

[0003] Waterborne alkyd resins are limited in application due to the slow development rate of film hardness, poor water resistance and water whitening resistance of the film, poor storage stability, and the inability to achieve a reasonable balance between weather resistance and anti-corrosion performance, as well as complex production processes.

[0004] Currently, the methods for improving the drying speed of air-drying alkyd resins include: adding natural hard resins (such as rosin) or synthetic hard resins (such as phenolic resins, petroleum resins), graft copolymerization modification of alkyd resins with vinyl monomers, and addition polymerization modification of alkyd resins with polyisocyanate compounds.

[0005] In the patent "A synthesis method of styrene and acrylate modified fast-drying waterborne alkyd resin" of CN102643392B, graft copolymerization modification of alkyd resins with vinyl monomers improves the hardness development speed, but the resin acid value is high (40 - 60mgKOH / g), which has a negative impact on the water resistance of the film.

[0006] In the patent "An epoxy resin prepolymer modified waterborne alkyd resin and its preparation method" of CN113831519A, trimellitic anhydride affects the storage stability, the water whitening resistance of the film is poor, and the corresponding film of the resin synthesized by replacing part of trimethylolpropane with epoxy ester prepolymer also shows loss of gloss.

[0007] In the patent "A self-emulsifying waterborne alkyd resin and self-emulsifying waterborne alkyd paint and preparation method" of CN109796583B, the storage at 50°C does not exceed 18 days; the bisphenol A type epoxy resin and aromatic epoxy active diluent used affect the weather resistance of the film and are not suitable for use as topcoats.

[0008] In the patent "Phenolic resin modified waterborne alkyd resin and preparation process and application" of CN109796583B, modified phenolic resin is used to synthesize alkyd resin to accelerate the film hardness development, and the disadvantage is that the phenolic structure causes the film to turn yellow, so it is not suitable to be used as a topcoat.

[0009] In the patent "An acrylic modified waterborne alkyd dispersion and its preparation method and application" of CN110527413B, the synthesis steps are numerous and the process is complex, resulting in an increase in material loss during the manufacturing process and being not conducive to industrial production.

[0010] In summary, the existing waterborne alkyd resins are limited in application due to the slow development speed of film hardness, poor water resistance and water whitening resistance of the film, poor storage stability, inability to achieve a reasonable balance between weather resistance and anti-corrosion performance, and complex production processes. Summary of the Invention

[0011] The object of the present invention is to solve the problems of slow development speed of film hardness, poor water resistance and water whitening resistance of the film, poor storage stability, inability to achieve a reasonable balance between weather resistance and anti-corrosion performance, and complex production processes of the existing waterborne alkyd resins, and to provide a waterborne alkyd dispersion that can be used in steel structure coatings, has a simple synthesis process, stable storage of colored paints, a fast development speed of film hardness, and good water resistance and water whitening resistance of the film.

[0012] To achieve the above object, the technical solution adopted by the present invention is: a waterborne alkyd resin dispersion, comprising a monoethylenically unsaturated carboxyl monomer, an aromatic vinyl monomer, an (alkyl) acrylate monomer, an initiator, a branched saturated fatty acid modified alkyd resin intermediate, a pH regulator, and deionized water.

[0013] Further, the preparation method of the branched saturated fatty acid modified alkyd resin intermediate is as follows: by mass, 310 - 330 parts of dehydrated castor oil acid, 250 - 260 parts of soybean oil fatty acid, and 20 - 26 parts of branched saturated fatty acid are mixed and stirred, heated to 80 °C, 205 - 215 parts of pentaerythritol, 30 - 35 parts of stearic acid, 225 - 255 parts of acid anhydride, and 6 - 16 parts of meta-aromatic polycarboxylic acid are added, heated to 175 - 185 °C, gradually heated to 215 - 225 °C, then cooled to 175 - 185 °C, 50 - 56 parts of xylene are added, gradually heated to 220 °C, and reacted until the acid value is lower than 16 mgKOH / g, cooled to 145 - 155 °C, 5 - 7 parts of monoglycidyl ester compound are added, and reacted for 1.5 - 2.0 hours. When the acid value is lower than 5 mgKOH / g, xylene is removed under reduced pressure, and 700 - 730 parts of ethylene glycol butyl ether are added to obtain the branched saturated fatty acid modified alkyd resin.

[0014] Preferably, the branched saturated fatty acid is one or two of isononanoic acid and neodecanoic acid.

[0015] Preferably, the meta-aromatic polycarboxylic acid is one of isophthalic acid, 1,3-phenylenediacetic acid, 5-methylisophthalic acid, A,A,A′,A′-tetramethyl-1,3-benzenedipropionic acid, and trimellitic acid.

[0016] Preferably, the monoglycidyl ester compound is a mixture of glycidyl methacrylate and glycidyl versatate, and the mass ratio of glycidyl methacrylate to glycidyl versatate is (2.3 - 2.5):1. Glycidyl methacrylate can effectively improve the graft copolymerization reaction points of alkyd resins; glycidyl versatate can quickly and effectively adjust the acid value of the resin, enhancing the weather resistance, water resistance and water whitening resistance of the resin.

[0017] Furthermore, the monoethylenically unsaturated carboxyl monomer includes one or more of acrylic acid, methacrylic acid, dimethacrylic acid, ethylacrylic acid, fumaric acid, maleic acid, crotonic acid.

[0018] Furthermore, the aromatic vinyl monomer is a mixture of styrene and α-methylstyrene, and the mass ratio of styrene to α-methylstyrene is (3.1 - 3.5):1.

[0019] Furthermore, the (meth)acrylic acid alkyl ester monomer is a mixture of C4-C8 alkyl acrylate and alkyl methacrylate, and the mass ratio of C4-C8 alkyl acrylate to alkyl methacrylate is (0.8 - 1.2):1.

[0020] Furthermore, the C4-C8 alkyl acrylate includes one or more of butyl acrylate, tert-butyl acrylate, isooctyl acrylate;

[0021] The alkyl methacrylate is a mixture of methyl methacrylate and C4-C12 alkyl methacrylate; the mass ratio of C4-C12 alkyl methacrylate to methyl methacrylate is (2.3 - 2.7):1.

[0022] The C4-C12 alkyl methacrylate is one of butyl methacrylate, isobutyl methacrylate, isooctyl methacrylate, isodecyl methacrylate. The C4-C12 alkyl methacrylate effectively enhances the weather resistance, water resistance and water whitening resistance of the resin film.

[0023] Furthermore, the pH regulator is a mixture of triethylamine and dimethylethanolamine, and their mass ratio is (5 - 6):1. If only dimethylethanolamine is used, the surface drying speed of the coating film becomes slow; if only triethylamine is used, the amine volatilization speed is too fast, which is not conducive to the stable storage of the coating, so the two need to be used in proportion.

[0024] Furthermore, the iodine value of the dehydrated ricinoleic acid is 145 - 165 mgKOH / g, and the iodine value of the soybean oil fatty acid is 135 - 140 mgKOH / g; the molar content of conjugated linoleic acid in the dehydrated ricinoleic acid is 30% - 50%. When the iodine value is too low, the film dries slowly and has low hardness; when the content of conjugated linoleic acid is too low, the crosslinking density of the film is low and the hardness development rate is slow.

[0025] Furthermore, the acid anhydride includes a mixture of an aromatic acid anhydride and a saturated aliphatic acid anhydride; the mass ratio of the aromatic acid anhydride to the saturated aliphatic acid anhydride is (3.5 - 3.9):1.

[0026] Preferably, the aromatic acid anhydride is one of phthalic anhydride and 1,8-naphthalic anhydride.

[0027] Preferably, the saturated aliphatic acid anhydride is one of hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, maleic anhydride, and succinic anhydride.

[0028] Preferably, the initiator is one or more of di-tert-butyl peroxide, tert-butyl 3,5,5-trimethylhexanoate, and 1,1'-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane.

[0029] The present invention also provides a method for preparing the above-mentioned aqueous alkyd resin dispersion, which includes the steps of mixing 55 - 65 parts of a monoethylenically unsaturated carboxyl monomer, 105 - 115 parts of an aromatic vinyl monomer, 70 - 80 parts of an (alkyl) acrylate monomer, 6 - 10 parts of an initiator, and 560 - 620 parts of a branched-chain saturated fatty acid-modified alkyd resin intermediate, reacting at 135 - 139 °C for 2.5 - 3.0 hours, maintaining the temperature for 0.5 - 1.5 hours and then cooling to 70 °C, adding 30 - 40 parts of a pH regulator for neutralization, and adding 600 - 630 parts of deionized water for dilution to obtain the aqueous alkyd resin dispersion. When preparing the aqueous alkyd resin dispersion, an appropriate amount of cosolvent can be additionally added as needed.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] 1. The weather resistance, water resistance, and water whitening resistance are adjusted by using branched-chain saturated fatty acids.

[0032] 2. The drying speed of the film and the hardness development rate are improved by synthesizing alkyd resin with soybean oil fatty acid containing conjugated double bonds and dehydrated ricinoleic acid with a high iodine value.

[0033] 3. Modifying alkyd resin with a mixture of styrene and α-methylstyrene increases the resin's glass transition temperature, accelerating the drying speed and hardness development of the coating while ensuring that weather resistance is not significantly affected, making the corresponding coating suitable for both base and topcoat applications. The introduction of an appropriate amount of meta-aromatic polybasic acid synergizes with the styrene and α-methylstyrene structure to enhance the coating's salt spray resistance, making the corresponding coating suitable for both base and topcoat applications.

[0034] 4. Using monoglycidyl ester compounds to adjust the acid value of alkyd resin intermediates in the later stage of synthesis shortens the reaction time, which is beneficial to industrial production; at the same time, it enhances the resin's weather resistance, water resistance and water whitening resistance.

[0035] The grafting modification of alkyd resin intermediates with C4-C8 alkyl acrylates and alkyl methacrylates improves the storage stability of the coating and enhances the weather resistance, water resistance and water whitening resistance of the coating film. DETAILED DESCRIPTION

[0036] The technical solutions of the present invention are further described below in conjunction with embodiments, but these are only some embodiments cited from numerous experiments by the applicant, and the scope of protection claimed by the present invention is not limited thereto.

[0037] Example 1

[0038] Synthesis of branched saturated fatty acid modified alkyd resin intermediate (M-1):

[0039] 328g of dehydrated ricinoleic acid, 256g of soybean oil fatty acid, and 22g of isononanoic acid were mixed and stirred, and the temperature was raised to 80°C. 211g of pentaerythritol, 32g of stearic acid, 188g of phthalic anhydride, 52g of hexahydrophthalic anhydride, and 14g of isophthalic acid were added. The temperature was raised to 180°C and gradually raised to 220°C (the heating rate was controlled to ensure that the temperature at the top of the packed column did not exceed 103°C). When the temperature at the top of the packed column fell back and was below 70°C, the temperature was lowered to 180°C, 51g of xylene was added, the temperature was gradually raised to 220°C, and the reaction was continued until the acid value was lower than 16mgKOH / g. The temperature was lowered to 150°C, 4.8 parts of glycidyl methacrylate and 2g of glycidyl versatate were added, and the reaction was carried out for 1.5 hours. When the acid value was lower than 5mgKOH / g, xylene was removed under reduced pressure, and 725g of ethylene glycol butyl ether was added and diluted to obtain an alkyd resin intermediate.

[0040] Preparation of waterborne alkyd resin dispersion (D-1):

[0041] Put 600 g of alkyd resin intermediate into the reaction device and heat up to 135 °C. Mix 57.6 g of methacrylic acid, 83.2 g of styrene, 26 g of α-methylstyrene, 37.2 g of isooctyl acrylate, 26 g of methyl methacrylate monomer, 10 g of isobutyl methacrylate, and 9 g of di-tert-butyl peroxide evenly, and then drop them into the reaction device within 3 hours while maintaining the temperature at 135 - 139 °C. After the dropping is completed, keep the temperature for 0.5 hour and then cool down to 70 °C. Add 28.9 g of triethylamine and 5.1 g of dimethylethanolamine for neutralization, add 617 g of deionized water for dilution, stir evenly, filter, and package to obtain the aqueous alkyd resin dispersion.

[0042] Example 2

[0043] Synthesis of branched saturated fatty acid modified alkyd resin intermediate (M-1):

[0044] Mix 310 g of dehydrated castor oil fatty acid, 250 g of soybean oil fatty acid, and 26 g of isononanoic acid and stir. Heat up to 80 °C, add 215 g of pentaerythritol, 30 g of stearic acid, 180 g of phthalic anhydride, 45 g of hexahydrophthalic anhydride, and 16 g of isophthalic acid. Heat up to 185 °C and gradually heat up to 225 °C (control the heating rate to ensure that the temperature at the top of the packed column does not exceed 103 °C). When the temperature at the top of the packed column drops and is lower than 70 °C, cool down to 185 °C, add 50 g of xylene, gradually heat up to 225 °C, and react until the acid value is lower than 16 mg KOH / g. Cool down to 155 °C, add 4.8 g of glycidyl methacrylate and 2 g of glycidyl versatate, react for 1.5 hours. When the acid value is lower than 5 mg KOH / g, remove xylene under reduced pressure, and add 715 g of ethylene glycol monobutyl ether for dilution to obtain the alkyd resin intermediate.

[0045] Preparation of aqueous alkyd resin dispersion (D-1):

[0046] Put 560 g of alkyd resin intermediate into the reaction device and heat up to 135 °C. Mix 60.3 g of methacrylic acid, 80.1 g of styrene, 26 g of α-methylstyrene, 37.2 g of isooctyl acrylate, 36 g of methyl methacrylate monomer, 6 g of isobutyl methacrylate, and 6.4 g of di-tert-butyl peroxide evenly, and then drop them into the reaction device within 2.8 hours while maintaining the temperature at 135 °C. After the dropping is completed, keep the temperature for 1 hour and then cool down to 75 °C. Add 25 g of triethylamine and 5.1 g of dimethylethanolamine for neutralization, add 628 g of deionized water for dilution, stir evenly, filter, and package to obtain the aqueous alkyd resin dispersion.

[0047] Example 3

[0048] Synthesis of branched saturated fatty acid modified alkyd resin intermediate (M-1):

[0049] Mix 320 g of dehydrated ricinoleic acid, 260 g of soybean oil fatty acid, and 24 g of neodecanoic acid, stir, and heat up to 80 °C. Charge 206 g of pentaerythritol, 35 g of stearic acid, 188 g of 1,8-naphthalic anhydride, 52 g of maleic anhydride, and 14 g of trimellitic acid. Heat up to 175 °C and then gradually to 215 °C (control the heating rate to ensure that the temperature at the top of the packed column does not exceed 103 °C). When the temperature at the top of the packed column drops below 70 °C, cool down to 175 °C, add 55 g of xylene, gradually heat up to 215 °C, and react until the acid value is lower than 16 mg KOH / g. Cool down to 145 °C, add 3.3 g of glycidyl methacrylate and 2 g of glycidyl versatate, react for 2.0 hours. When the acid value is lower than 5 mg KOH / g, remove xylene under reduced pressure, and add 703 g of ethylene glycol monobutyl ether for dilution to obtain the alkyd resin intermediate.

[0050] Preparation of aqueous alkyd resin dispersion (D-1):

[0051] Charge 620 g of the alkyd resin intermediate into the reaction device and heat up to 139 °C. Mix 64.3 g of ethyl acrylate, 88 g of styrene, 25 g of α-methylstyrene, 35 g of tert-butyl acrylate, 22.8 g of methyl methacrylate monomer, 22 g of isobutyl methacrylate, and 7 g of di-tert-butyl peroxide evenly, and then dropwise add them to the reaction device within 3 hours while maintaining the temperature at 139 °C. After the dropping is complete, keep the temperature for 1 hour and then cool down to 75 °C. Add 35.5 g of triethylamine and 3.6 g of dimethylethanolamine for neutralization, add 600 g of deionized water for dilution, stir evenly, filter, and package to obtain the aqueous alkyd resin dispersion.

[0052] Prepare a coating using the aqueous alkyd resin dispersion prepared in Example 1 and test the coating properties.

[0053] Preparation of steel structure coating (P-1) based on aqueous alkyd resin dispersion (D-1):

[0054] Pre-disperse 60 g of aqueous alkyd resin dispersion (D-1), 9.1 g of deionized water, 0.5 g of dimethylethanolamine, 7 g of ethylene glycol monobutyl ether, 0.8 g of drier, and 0.5 g of defoamer at a speed of 500 rpm. Then add 10 g of titanium dioxide, 5 g of calcium carbonate, 24 g of precipitated barium sulfate, 2.1 g of carbon black, 17 g of zinc phosphate, and 0.7 g of organobentonite. Disperse evenly at a speed of 800 rpm, transfer the slurry to a sand mill, grind it with zirconium beads as the medium until the fineness reaches below 35 μm, filter with a 200-mesh sieve, and then add 60 g of aqueous alkyd resin dispersion (D-1), 2.0 g of triethylamine, 0.5 g of leveling agent, and 0.8 g of wetting agent. Disperse evenly at a speed of 800 rpm to obtain the waterborne alkyd paint for steel structures.

[0055] Description of the test method:

[0056] Paint storage stability: No water separation or precipitation occurs during storage at 50°C, and the viscosity increase is less than 20 KU.

[0057] Surface drying time and through drying time of the paint film: Tested in accordance with GB / T1728;

[0058] Gloss of the paint film: Tested in accordance with GB / T9754;

[0059] Pencil hardness of the paint film: Tested in accordance with GB / T5209;

[0060] Water resistance of the paint film: Tested in accordance with GB / T5739;

[0061] Water whitening resistance of the paint film: Check the Lab values before and after the water resistance test using a spectrophotometric color difference meter TS7010, and compare the magnitude of the difference ΔL.

[0062] Glass transition temperature (Tg) of the paint film: Detected using a PerkinElmer differential scanning calorimeter DSC8500.

[0063] Artificial aging resistance of the paint film: Tested in accordance with GB / T1766;

[0064] Salt spray resistance of the paint film: Tested in accordance with GB / T1771.

[0065] Table 1 Performance test results of the paint in Example 1 and commercially available samples

[0066]

[0067]

[0068] The test results show that: The paint of the product in Example 1 has good storage stability, a relatively high glass transition temperature of the paint film, a fast hardness development rate, good water resistance and water whitening resistance of the paint film, and a reasonable balance between weather resistance and anti-corrosion performance, making it suitable for light anti-corrosion coating of steel structures with the requirement of bottom and surface integration.

[0069] Comparative Example 1

[0070] Synthesis of alkyd resin intermediate (M-2):

[0071] Mix 328 g of dehydrated ricinoleic acid and 256 g of soybean fatty acid, stir, and heat up to 80 °C. Charge 211 g of pentaerythritol, 32 g of stearic acid, 188 g of phthalic anhydride, 52 g of hexahydrophthalic anhydride, and 14 g of isophthalic acid. Heat up to 180 °C and then gradually to 220 °C (control the heating rate to ensure that the temperature at the top of the packed column does not exceed 103 °C). When the temperature at the top of the packed column drops and is lower than 70 °C, cool down to 180 °C, add 51 g of xylene, gradually heat up to 220 °C, and react until the acid value is lower than 16 mg KOH / g. Cool down to 150 °C, add 4.8 parts of glycidyl methacrylate and 2 g of glycidyl versatate, react for 1.5 - 2.0 hours. When the acid value is lower than 5 mg KOH / g, remove xylene under reduced pressure, and add 725 g of ethylene glycol monobutyl ether for dilution to obtain the alkyd resin intermediate.

[0072] Preparation of waterborne alkyd resin dispersion (D - 2):

[0073] Charge 600 g of the alkyd resin intermediate into the reaction device and heat up to 135 °C. Mix 57.6 g of methacrylic acid, 83.2 g of styrene, 26 g of α - methylstyrene, 37.2 g of isooctyl acrylate, 26 g of methyl methacrylate monomer, 10 g of isobutyl methacrylate, and 9 g of di - tert - butyl peroxide evenly, and then drop - add them to the reaction device within 2.5 hours while maintaining the temperature at 135 - 139 °C. After the dropping is completed, keep the temperature for 1 hour and then cool down to 70 °C. Add 28.9 g of triethylamine and 5.1 g of dimethylethanolamine for neutralization, add 617 g of deionized water for dilution, stir evenly, filter, and package to obtain the waterborne alkyd resin dispersion.

[0074] Pre - disperse 60 g of waterborne alkyd resin dispersion (D - 2), 9.1 g of deionized water, 0.5 g of dimethylethanolamine, 7 g of ethylene glycol monobutyl ether, 0.8 g of drier, and 0.5 g of defoamer at a rotation speed of 500 rpm. Then add 10 g of titanium dioxide, 5 g of calcium carbonate, 24 g of precipitated barium sulfate, 2.1 g of carbon black, 17 g of zinc phosphate, and 0.7 g of organobentonite. Disperse evenly at a rotation speed of 800 rpm, then transfer the slurry to a sand mill and grind it with zirconium beads as the medium until the fineness reaches below 35 μm. Filter with a 200 - mesh sieve, and then add 60 g of waterborne alkyd resin dispersion (D - 2), 2.0 g of triethylamine, 0.5 g of leveling agent, and 0.8 g of wetting agent, and disperse evenly at a rotation speed of 800 rpm to obtain the waterborne alkyd paint (P - 2). Test the film properties of the paint, and the results are shown in Table 2.

[0075] Table 2 Test results of the paint performance of Comparative Example 1

[0076]

[0077] The difference between Comparative Example 1 and Example 1 is that the waterborne alkyd resin in Comparative Example 1 was not modified with branched saturated fatty acids. It can be seen that the water resistance, water whitening resistance and aging resistance of the coating prepared in Comparative Example 1 are significantly worse, indicating that the modification of the waterborne alkyd resin with branched saturated fatty acids according to the present invention can effectively improve various properties of the coating.

Claims

1. An aqueous alkyd resin dispersion, characterized in that, It includes a monoethylenically unsaturated carboxyl monomer, an aromatic vinyl monomer, an (alkyl) acrylate monomer, an initiator, a branched saturated fatty acid-modified alkyd resin intermediate, a pH regulator, and deionized water; The preparation method of the branched saturated fatty acid-modified alkyd resin intermediate is as follows: By mass, 310 - 330 parts of dehydrated castor oil fatty acid, 250 - 260 parts of soybean oil fatty acid, and 20 - 26 parts of branched saturated fatty acid are mixed and stirred, heated to 80 °C, 205 - 215 parts of pentaerythritol, 30 - 35 parts of stearic acid, 225 - 255 parts of acid anhydride, and 6 - 16 parts of meta-aromatic polyacid are added, heated to 175 - 185 °C, gradually heated to 215 - 225 °C, then cooled to 175 - 185 °C, 50 - 56 parts of xylene are added, gradually heated to 215 - 225 °C, reacted until the acid value is lower than 16 mg KOH / g, cooled to 145 - 155 °C, 5 - 7 parts of monoglycidyl ester compound are added, reacted for 1.5 - 2.0 hours, when the acid value is lower than 5 mg KOH / g, xylene is removed under reduced pressure, and 700 - 730 parts of ethylene glycol butyl ether are added to obtain the branched saturated fatty acid-modified alkyd resin; The monoglycidyl ester compound is a mixture of glycidyl methacrylate and glycidyl versatate, and the mass ratio of glycidyl methacrylate to glycidyl versatate is (2.3 - 2.5):1; The branched saturated fatty acid is one or both of isononanoic acid and neodecanoic acid.

2. The aqueous alkyd resin dispersion according to claim 1, wherein The monoethylenically unsaturated carboxyl monomer includes one or several of acrylic acid, methacrylic acid, dimethacrylic acid, ethylacrylic acid, fumaric acid, maleic acid, and crotonic acid.

3. The aqueous alkyd resin dispersion according to claim 1, wherein The aromatic vinyl monomer includes a mixture of styrene and α-methylstyrene, and the mass ratio of styrene to α-methylstyrene is (3.1 - 3.5):

1.

4. The aqueous alkyd resin dispersion according to claim 1, characterized in that, The (alkyl) acrylate monomer includes a mixture of C4 - C8 alkyl acrylates and alkyl methacrylates, and the mass ratio of C4 - C8 alkyl acrylates to alkyl methacrylates is (0.8 - 1.2):

1.

5. The aqueous alkyd resin dispersion according to claim 4, wherein The C4 - C8 alkyl acrylate includes one or several of butyl acrylate, tert-butyl acrylate, and isooctyl acrylate; The alkyl methacrylate includes a mixture of methyl methacrylate and C4 - C12 alkyl methacrylates; the mass ratio of C4 - C12 alkyl methacrylates to methyl methacrylate is (2.3 - 2.7):

1.

6. The aqueous alkyd resin dispersion according to claim 2, characterized in that, The pH regulator includes a mixture of triethylamine and dimethylethanolamine, and the mass ratio of the two is (5 - 6):

1.

7. The aqueous alkyd resin dispersion according to claim 1, wherein The iodine value of the dehydrated castor oil fatty acid is 145 - 165 mg KOH / g, and the iodine value of the soybean oil fatty acid is 135 - 140 mg KOH / g; the molar content of conjugated linoleic acid in the dehydrated castor oil fatty acid is 30% - 50%.

8. The aqueous alkyd resin dispersion according to claim 1, characterized in that, The acid anhydride includes a mixture of aromatic acid anhydride and saturated fatty acid anhydride; the mass ratio of aromatic acid anhydride to saturated fatty acid anhydride is (3.5 - 3.9):

1.

9. The preparation method of the aqueous alkyd resin dispersion according to any one of claims 1-8, characterized in that, It includes: Mix 55 - 65 parts of monoethylenically unsaturated carboxyl monomer, 105 - 115 parts of aromatic vinyl monomer, 70 - 80 parts of (meth)acrylic acid alkyl ester monomer, 6 - 10 parts of initiator, and 560 - 620 parts of branched saturated fatty acid modified alkyd resin intermediate. React at 135 - 139 °C for 2.5 - 3.0 hours, keep warm for 0.5 - 1.5 hours, then cool down to 65 - 75 °C, add 30 - 40 parts of pH regulator for neutralization, and add 600 - 630 parts of deionized water for dilution to obtain an aqueous alkyd resin dispersion.

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