Waterborne alkyd resin dispersion and preparation method thereof

Abstract

The invention provides a water-based alkyd resin dispersion and a preparation method thereof, and belongs to the technical field of macromolecules, the preparation method of the water-based alkyd resin dispersion comprises the following steps: firstly, synthesizing alkyd ester containing vinyl active double bonds and a double-bond modified organosilicon prepolymer, then uniformly mixing a vinyl monomer and the modified organosilicon prepolymer, and carrying out melt extrusion to obtain the water-based alkyd resin dispersion. According to the present invention, organic silicon is introduced into the alkyd ester, and is gradually dropwise added into the alkyd ester in a rapid and slow manner to perform free radical polymerization so as to form the uniform polymer, such that the compatibility is good, the combination degree between the polymer chains is increased, and the reaction group distribution is uniform; the cyclic molecule contained at one end of the introduced organic silicon and the isopropoxy group contained at the other end of the introduced organic silicon make the steric hindrance of the polymer large; the problem that the dispersion is poor in storage stability is solved, the prepared dispersion is good in dispersion stability, multiple cross-linking reactions can occur in the film forming process, anchoring points are formed with a base material, and therefore the hardness and flexibility of a paint film and the adhesive force of the paint film and the base material are improved, and then the excellent aging resistance, impact resistance and medium resistance are shown; wide market application prospects are realized.

Description

Technical Field

[0001] The invention belongs to the technical field of polymers, and in particular relates to a waterborne alkyd resin dispersion and a preparation method thereof. Background Art

[0002] Waterborne alkyd resin has attracted people's attention due to its advantages such as easy construction, air self-oxidation cross-linking and high gloss of paint film, and is widely used in chemical equipment, plastic surface corrosion protection and architectural decoration. However, the waterborne alkyd resin products on the market still have disadvantages such as long drying time and poor mechanical properties.

[0003] In order to solve the above problems, researchers at home and abroad have made a lot of efforts. The Chinese patent with application number 202111134806 discloses an epoxy resin prepolymer modified water-based alkyd resin and its preparation method. The resin dries quickly and has high hardness, but the water resistance of the paint film is relatively low. Severe water whitening and blistering occur after soaking in water for one day. The Chinese invention patent with application number 202110881209 discloses a modified water-based alkyd resin and its preparation method, as well as an aqueous dispersion containing it. Although the water resistance of the modified water-based alkyd resin is improved, the hardness of the paint film is small and the preparation method is relatively complicated. The Chinese invention patent with application number 201510555550.9 discloses a silicon-fluorine modified water-based alkyd resin dispersion and its preparation method. Silicone and organic fluorine are introduced into the molecular structure of the alkyd resin. The modified alkyd resin exhibits high hardness and anti-fouling ability, but the impact resistance of the resin paint film is low, which limits its application in some fields. This is mainly because water-based alkyd resins have a low degree of cross-linking and low cohesion, making it difficult to balance the hardness and flexibility (impact resistance) of the paint film, and have poor aging resistance and media resistance. Summary of the invention

[0004] In order to solve the technical problems of poor storage stability of waterborne alkyd resin dispersion, difficulty in balancing the hardness and impact resistance of the paint film, poor aging resistance and medium resistance, the present invention provides a waterborne alkyd resin dispersion and a preparation method thereof. The waterborne resin dispersion has good appearance, good storage stability, high hardness and flexibility of the paint film, and excellent aging resistance and medium resistance.

[0005] In order to achieve the above object, the technical solution of the present invention is achieved as follows: A method for preparing a water-based alkyd resin dispersion, comprising the following steps: (1) unsaturated vegetable oil acid accounting for 50-70 wt% of the raw material components, acrylic acid accounting for 30-45 wt% of the raw material components, trimethylolpropane, a catalyst, and a polymerization inhibitor are mixed to carry out esterification reaction, and when the acid value of the system drops to ≤15 mgKOH / g, the remaining unsaturated vegetable oil acid is added, and the esterification is continued until the acid value is ≤8 mgKOH / g to obtain an alcohol acid ester; (2) mixing and reacting a solvent accounting for 15-25 wt% of the raw material components, acrylic acid accounting for 20-30 wt% of the raw material components, and organosilicon to obtain an organosilicon prepolymer reaction liquid; (3) uniformly mixing a mixed solution of methyl methacrylate, butyl acrylate, a vinyl crosslinking monomer, remaining acrylic acid, an initiator accounting for 65-75 wt % of the raw material components, a chain transfer agent, a solvent accounting for 25-35 wt % of the raw material components, and the silicone prepolymer reaction solution of step (2); (4) adjusting the temperature of the alkyd ester of step (1) to 80-140° C., adding 25-35 wt % of a solvent based on the raw material components, and then adding the mixed solution of step (3), the remaining solvent and the remaining initiator, and continuing the reaction for 2-2.5 h to obtain an alkyd resin; (5) The reaction system of step (4) is cooled to room temperature, a neutralizing agent is added while stirring until the pH value is 8-9, and deionized water is added and stirred evenly to obtain a resin dispersion.

[0006] Preferably, in step (1), the mass ratio of acrylic acid to alkyd ester is 1:(17-22); in step (4), the mass ratio of acrylic acid to alkyd ester is 1:(2.1-2.4), the mass ratio of silicone to alkyd ester is 1:(8-12); and the mass ratio of vinyl crosslinking monomer to acrylic acid ester is 1:(22-42).

[0007] Preferably, the raw material components and weight parts of the water-based alkyd resin dispersion are: 22-30 parts of unsaturated vegetable oil acid, 16-18 parts of trimethylolpropane, 0.05-0.3 parts of catalyst, 0.1-0.2 parts of inhibitor, 28-32 parts of solvent, 6-8 parts of butyl acrylate, 8-10 parts of methyl methacrylate, 6-8 parts of acrylic acid, 3.69-4.92 parts of silicone, 1-2.2 parts of vinyl crosslinking monomer, 0.1-0.3 parts of chain transfer agent, 1-4 parts of initiator, 2-4 parts of neutralizer, and 100-120 parts of deionized water.

[0008] Preferably, the temperature of the esterification reaction in step (1) is 180-220° C.; the reaction conditions in step (2) are 35-50° C., and the reaction time is 1-2 h.

[0009] Preferably, the mixed solution in step (43) is added in two times, the first time 15-25wt% of the mixed solution is added, and the addition time is 25-30min; the second time the remaining mixed solution is added, and the addition time is 2-3h.

[0010] Preferably, the unsaturated vegetable oil acid is dehydrated ricinoleic acid or linoleic acid, wherein the iodine value of the unsaturated vegetable oil is greater than 160 g / 100g.

[0011] Preferably, the organosilicon is β-(3,4-epoxycyclohexyl)ethyltriethoxysilane (A-186) or β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane (A-187); the molecular structures thereof are respectively: A-186: , A-187: .

[0012] Preferably, the vinyl crosslinking monomer is N -Hydroxymethyl acrylamide (HMEA), N - Hydroxyethyl acrylamide (HEAA) or N -Any one of methoxyacrylamide (NMMA); the structural formulas are respectively, HMEA: , HEAA: , NMMA: .

[0013] Preferably, the solvent is a combination of diethylene glycol monobutyl ether and propylene glycol butyl ether, and the mass ratio of the two is (1.1-1.5):1; the catalyst is a combination of zinc oxide and lithium hydroxide, and the mass ratio of the two is 2:1; the chain transfer agent is dodecyl mercaptan or 3-mercapto-1-propanol.

[0014] Preferably, the initiator is azobisisobutyronitrile, dibenzoyl peroxide or di-tert-butyl peroxide; the inhibitor is one or a combination of any two of p-hydroxyanisole, hydroquinone and 4-methoxyphenol; and the neutralizer is triethylamine or NN dimethylethanolamine.

[0015] Preferably, the waterborne alkyd resin dispersion prepared by the method has a particle size distribution of less than 150 nm and has no change after heat storage at 50° C. for 30 days.

[0016] The paint film of the water-based alkyd resin dispersion prepared by the present invention has a hardness of 1H and an impact resistance of 48 kg·cm; the paint film does not bubble, fall off or rust after being immersed in water for 12 days, and the acid resistance can reach 172 hours; the paint film surface does not change after being wiped with solvent xylene for 25 times; and does not powder, crack or bubble after being illuminated by xenon light for 15 days.

[0017] The present invention has the following beneficial effects: 1. The present invention uses a chemical polymerization process to prepare a water-based alkyd resin dispersion. In short: first, an alkyd ester containing active vinyl double bonds and a modified silicone prepolymer are synthesized, and then the vinyl monomer and the modified silicone prepolymer are uniformly mixed, and then gradually added to the alkyd ester in a "fast and slow" manner for free radical polymerization to form a uniform polymer, so that the bonding degree between polymer chains is increased, the reactive groups are evenly distributed, and the synergistic effect of polymers can be better exerted. Compared with physical blending, the dispersion prepared by this method has a better appearance, and the cyclic molecules contained at one end of the introduced silicone and the isopropoxy group contained at the other end increase the steric hindrance of the polymer, solving the problem of poor storage stability of the dispersion.

[0018] 2. The present invention connects alkyd esters, acrylates and silicones with greatly different polarities by chemical reaction, thus ensuring the uniformity of the resin dispersion. Then, the ratio of acrylic acid to alkyd ester is limited in the preparation process of alkyd ester, so that the vinyl monomer and silicone prepolymer are grafted onto the alkyd ester chain, improving the compatibility between each other and making the resin evenly dispersed at the microscopic level; the mass ratio of acrylate to alkyd ester is limited, so that the resin has good water dispersibility and improves the aging resistance of the modified alkyd resin.

[0019] 3. The dispersion prepared by the present invention undergoes multiple cross-linking reactions during the film-forming process: (a) the vinyl cross-linking monomer copolymerized on the main chain of the resin generates hydrogen bonds through its own amide group to form a network structure by self-cross-linking; (b) the unsaturated vegetable oil acid introduced into the synthetic alkyd undergoes oxygen absorption and self-cross-linking under the action of a catalyst to form a network structure; (c) the hydroxyl groups contained in the vinyl monomer copolymerized on the main chain of the resin undergo dehydration condensation with the silanol groups generated by the hydrolysis of the organosilicon to form a network structure by cross-linking; (d) the organosilicon copolymerized on the main chain of the resin undergoes hydrolysis to form a network structure by cross-linking; (e) the silanol groups generated by the hydrolysis of the organosilicon copolymerized on the main chain of the resin undergo cross-linking with the hydroxyl groups on the surface of the substrate to form anchor points. The physical hydrogen bonds formed in (a) above can dynamically disperse the impact resistance of the outside world and improve the flexibility of the paint film; the chemical bonds formed by (b), (c) and (d) restrict the freedom of movement between polymers, increase their rigidity, and improve the hardness of the paint film, thereby making the resin paint film exhibit high hardness and high flexibility; and the anchor points formed with the substrate in (e) improve the adhesion of the paint film. This multiple cross-linking makes the network structure of the resin paint film dense and increases the cross-linking density, so that the resin paint film exhibits excellent aging resistance and medium resistance.

[0020] 4. The waterborne alkyd resin dispersion of the present invention has good appearance and good thermal storage stability. The paint film simultaneously exhibits high hardness (=1 H) and high flexibility (48 kg·cm), and has certain aging resistance and medium resistance. The raw materials are economical, environmentally friendly, and low in cost, and have broad market application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 Schematic diagram of the preparation of the waterborne alkyd resin of the present invention (using Example 1 as a reference example).

[0023] Figure 2 The following are the glass transition temperature (DSC) and thermogravimetric (TAG) diagrams of the waterborne alkyd resin paint film of the present invention (using Example 1 as a reference example).

[0024] Figure 3 It is a scanning electron microscope (SEM) and an energy dispersive spectrometer (EDS) of a cross section of the waterborne alkyd resin paint film of the present invention.

[0025] Figure 4 It is a diagram of the film-forming mechanism of the waterborne alkyd resin dispersion of the present invention. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] Unless otherwise specified, the experimental methods used in the embodiments of the present invention are conventional methods.

[0028] Unless otherwise specified, the materials, reagents, etc. used in the embodiments of the present invention can be obtained from commercial sources.

[0029] Example 1 This embodiment provides a water-based alkyd resin dispersion, and the raw material components are as follows in parts by mass: Linoleic acid: 30g; Trimethylolpropane: 18g; Catalyst: zinc oxide (ZnO), lithium hydroxide (LiOH), 0.2g, 0.1g respectively; Inhibitor: 4-methoxyphenol, 0.2 g; Solvent: diethylene glycol monobutyl ether (DGBE), propylene glycol butyl ether (PnB), 18g, 14g respectively; Butyl acrylate (BA): 8g; Methyl methacrylate (MMA): 10g; Acrylic acid (AA): 8g; Vinyl crosslinking monomers: N -Hydroxyethyl acrylamide (HEAA), 1.5 g; Chain transfer agent: dodecyl mercaptan (SH), 0.3 g; Initiator: azobisisobutyronitrile (AIBN), 2 g; Silicone: β -(3,4-Epoxycyclohexyl)ethyltriethoxysilane (A-186): 4.92 g; Neutralizer: NN dimethylethanolamine (DMEA), 4g; Deionized water: 120g.

[0030] The preparation process is: (1) 18 g linoleic acid, 3 g AA, 18 g trimethylolpropane, 0.2 g ZnO, 0.1 g LiOH, and 0.2 g 4-methoxyphenol were added to a 500 mL four-necked flask equipped with an electric stirrer, a condenser, a thermometer, and a water separator (stirring rate 150 r / min). The oil bath was heated to 200 °C and the acid value was tested every 1 h. When the acid value of the system dropped to ≤15 mgKOH / g, the remaining linoleic acid was added and esterification was continued until the acid value was ≤8 mgKOH / g to obtain an alcohol ester.

[0031] (2) 3.6 g DGBE, 2.8 g PnB, 2.16 g AA and 4.92 g A-186 were added sequentially into a 250 mL four-necked flask equipped with an electric stirrer and a thermometer (stirring rate 150 r / min). The flask was heated to 38 °C in a water bath and reacted for 1.5 h to obtain a silicone prepolymer reaction solution.

[0032] (3) Weigh 10 MMA, 8 g BA, 1.5 g HEAA, the remaining AA, 1.4 g AIBN, 0.3 g SH, 5.4 g DGBE, 4.2 g PnB and the mixed solution of the prepolymer reaction solution in step (2), and mix them evenly.

[0033] (4) The temperature of the alkyd obtained in step (1) is adjusted to 88°C, and 5.4 g of DGBE and 4.2 g of PnB are added; 1 / 5 of the mixed solution in step (3) is rapidly dripped into the alkyd for 25-30 min; then the remaining mixed solution is slowly dripped for 2-3 h, and then the remaining initiator and solvent are added, and the reaction is kept warm for 2-2.5 h to obtain a modified alkyd resin.

[0034] (5) Cooling to room temperature, adding 4 g of DMEA to step (4) while stirring until the pH is 8-9, adding deionized water and stirring evenly to obtain a waterborne alkyd resin dispersion.

[0035] Example 2 This embodiment provides a water-based alkyd resin dispersion, and the raw material components are as follows in parts by mass: Linoleic acid: 22g; Trimethylolpropane: 16g; Catalyst: zinc oxide (ZnO), lithium hydroxide (LiOH), 0.1g, 0.05g respectively; Inhibitor: p-hydroxyanisole, 0.1 g; Solvent: diethylene glycol monobutyl ether (DGBE), propylene glycol butyl ether (PnB), accounting for 16.8g and 11.2g respectively; Butyl acrylate (BA): 6g; Methyl methacrylate (MMA): 8g; Acrylic acid (AA): 6g; Vinyl crosslinking monomers: N -NMMA, 1 g; Chain transfer agent: 3-mercapto-1-propanol, 0.1 g; Initiator: azobisisobutyronitrile (AIBN), 1 g; Silicone: β -(3,4-Epoxycyclohexyl)ethyltrimethoxysilane (A-187): 3.69 g; Neutralizing agent: triethylamine, 2g; Deionized water: 100g.

[0036] The preparation process is: (1) 11 g linoleic acid, 1.8 g AA, 16 g trimethylolpropane, 0.1 g ZnO, 0.05 g LiOH, and 0.1 g p-hydroxyanisole were added to a 500 mL four-necked flask equipped with an electric stirrer, a condenser, a thermometer, and a water separator (stirring rate 150 r / min). The oil bath was heated to 180°C, and the acid value was tested every 1 h. When the acid value of the system dropped to ≤15 mgKOH / g, the remaining linoleic acid was added and esterification was continued until the acid value was ≤8 mgKOH / g to obtain an alcohol ester.

[0037] (2) 2.52 g DGBE, 1.68 g PnB, 1.2 g AA and 3.69 g A-187 were added sequentially into a 250 mL four-necked flask equipped with an electric stirrer and a thermometer (stirring rate 150 r / min). The mixture was heated to 35 °C in a water bath and reacted for 2 h to obtain a silicone prepolymer reaction solution.

[0038] (3) Weigh 8 MMA, 6 g BA, 1 g NMMA, the remaining AA, 0.65 g AIBN, 0.1 g 3-mercapto-1-propanol, 6.53 g DGBE, 3.27 g PnB and the mixed solution of the prepolymer reaction solution in step (2), and mix them evenly.

[0039] (4) The temperature of the alkyd obtained in step (1) is adjusted to 80°C, and 4.2g of DGBE and 2.8g of PnB are added; 15wt% of the mixed solution in step (3) is rapidly dripped into the alkyd for 25-30 min; then the remaining mixed solution is slowly dripped for 2-3 h, and then the remaining initiator and solvent are added, and the reaction is kept warm for 2-2.5 h to obtain a modified alkyd resin.

[0040] (5) Cooling to room temperature, adding 2 g of triethylamine to step (4) while stirring until the pH is 8-9, adding deionized water and stirring evenly to obtain a waterborne alkyd resin dispersion.

[0041] Example 3 This embodiment provides a water-based alkyd resin dispersion, and the raw material components are as follows in parts by mass: Dehydrated ricinoleic acid: 30g; Trimethylolpropane: 18g; Catalyst: zinc oxide (ZnO), lithium hydroxide (LiOH), 0.16g, 0.08g respectively; Inhibitor: hydroquinone, 0.15g; Solvent: diethylene glycol monobutyl ether (DGBE), propylene glycol butyl ether (PnB), accounting for 16g and 14g respectively; Butyl acrylate (BA): 7g; Methyl methacrylate (MMA): 9g; Acrylic acid (AA): 7g; Vinyl crosslinking monomers: N - Hydroxymethyl acrylamide (HMMA), 2.2 g; Chain transfer agent: 3-mercapto-1-propanol, 0.2 g; Initiator: dibenzoyl peroxide (BPO), 4 g; Silicone: Silicone is β-(3,4-Epoxycyclohexyl)ethyltrimethoxysilane (A-187): 5.38 g; Neutralizing agent: triethylamine, 3g; Deionized water: 110 g.

[0042] The preparation process is: (1) 18 g of dehydrated ricinoleic acid, 2.625 g of AA, 18 g of trimethylolpropane, 0.16 g of ZnO, 0.08 g of LiOH, and 0.15 g of hydroquinone were added to a 500 mL four-necked flask equipped with an electric stirrer, a condenser, a thermometer, and a water separator (stirring rate 150 r / min). The oil bath was heated to 220°C, and the acid value was tested every 1 h. When the acid value of the system dropped to ≤15 mgKOH / g, the remaining linoleic acid was added and esterification was continued until the acid value was ≤8 mgKOH / g to obtain an alcohol ester.

[0043] (2) 3.2 g DGBE, 2.8 g PnB, 1.89 g AA and 5.38 g A-187 were added sequentially into a 250 mL four-necked flask equipped with an electric stirrer and a thermometer (stirring rate 150 r / min). The mixture was heated to 45 °C in a water bath and reacted for 1 h to obtain a silicone prepolymer reaction solution.

[0044] (3) Weigh 9 g MMA, 7 g BA, 2.2 g HMMA, the remaining AA, 2.8 g AIBN, 0.2 g 3-mercapto-1-propanol, 4.8 g DGBE, 4.2 g PnB and the mixed solution of the prepolymer reaction solution in step (2), and mix them evenly.

[0045] (4) The temperature of the alkyd obtained in step (1) is adjusted to 98°C, and 4.8 g of DGBE and 4.2 g of PnB are added; 1 / 5 of the mixed solution in step (3) is rapidly dripped into the alkyd for 25-30 min; then the remaining mixed solution is slowly dripped for 2-3 h, and then the remaining initiator and solvent are added, and the reaction is kept warm for 2-2.5 h to obtain a modified alkyd resin.

[0046] (5) Cooling to room temperature, adding 3 g of triethylamine to step (4) while stirring until the pH is 8-9, adding deionized water and stirring evenly to obtain a waterborne alkyd resin dispersion.

[0047] Example 4 This embodiment provides a water-based alkyd resin dispersion, and the raw material components are as follows in parts by mass: Dehydrated ricinoleic acid: 26g; Trimethylolpropane: 17g; Catalyst: zinc oxide (ZnO), lithium hydroxide (LiOH), accounting for 0.18g and 0.09g respectively; Inhibitor: hydroquinone, 0.18g; Solvent: diethylene glycol monobutyl ether (DGBE), propylene glycol butyl ether (PnB), accounting for 16.36g and 13.6g respectively; Butyl acrylate (BA): 7.5 g; Methyl methacrylate (MMA): 8.5 g; Acrylic acid (AA): 7.5 g; Vinyl crosslinking monomers: N -Hydroxyethylacrylamide (HEEA), 1.8 g; Chain transfer agent: 3-mercapto-1-propanol, 0.18 g; Initiator: di-tert-butyl peroxide, 3 g; Silicone: β -(3,4-Epoxycyclohexyl)ethyltriethoxysilane (A-187): 5.48 g; Neutralizer: NN dimethylethanolamine (DMEA), 3.5 g; Deionized water: 116 g.

[0048] The preparation process is: (1) 18.2 g of dehydrated ricinoleic acid, 3.375 g of AA, 17 g of trimethylolpropane, 0.18 g of ZnO, 0.09 g of LiOH, and 0.18 g of hydroquinone were added to a 500 mL four-necked flask equipped with an electric stirrer, a condenser, a thermometer, and a water separator (stirring rate 150 r / min). The oil bath was heated to 200 °C, and the acid value was tested every 1 h. When the acid value of the system dropped to ≤15 mgKOH / g, the remaining linoleic acid was added and esterification was continued until the acid value was ≤8 mgKOH / g to obtain an alcohol ester.

[0049] (2) 3.93 g DGBE, 3.57 g PnB, 2.25 g AA and 5.48 g A-187 were added sequentially into a 250 mL four-necked flask equipped with an electric stirrer and a thermometer (stirring rate 150 r / min). The mixture was heated to 50 °C in a water bath and reacted for 1 h to obtain a silicone prepolymer reaction solution.

[0050] (3) Weigh 8.5 g of MMA, 7.5 g of BA, 1.8 g of HMMA, the remaining AA, 1.95 g of di-tert-butyl peroxide, 0.18 g of 3-mercapto-1-propanol, 4.8 g of DGBE, 4.2 g of PnB and a mixed solution of the prepolymer reaction solution in step (2), and mix them evenly.

[0051] (4) The temperature of the alkyd obtained in step (1) is adjusted to 140°C, and 4.8 g of DGBE and 4.2 g of PnB are added; 25 wt% of the mixed solution in step (3) is rapidly dripped into the alkyd for 25-30 min; then the remaining mixed solution is slowly dripped for 2-3 h, and then the remaining initiator and solvent are added, and the reaction is kept warm for 2-2.5 h to obtain a modified alkyd resin.

[0052] (5) Cooling to room temperature, adding 3.5 g of DMEA to step (4) while stirring until the pH is 8-9, adding deionized water and stirring evenly to obtain a waterborne alkyd resin dispersion.

[0053] Comparative Example 1 This comparative example provides a waterborne alkyd resin dispersion, which differs from Example 1 in that no acrylate and silicone prepolymer (unmodified waterborne alkyd resin dispersion) are added. The preparation steps are as follows, and the raw material components are calculated by weight: This comparative example provides a water-based alkyd resin dispersion, and the raw material components are as follows in parts by mass: Linoleic acid: 30g; Trimethylolpropane: 18g; Catalyst: zinc oxide (ZnO), lithium hydroxide (LiOH), 0.2g, 0.1g respectively; Inhibitor: 4-methoxyphenol, 0.2 g; Solvent: diethylene glycol monobutyl ether (DGBE), propylene glycol butyl ether (PnB), accounting for 11.8g and 9.19g respectively; Acrylic acid (AA): 3g; Neutralizing agent: NN dimethylethanolamine (DMEA), 2.1 g; Deionized water: 75g.

[0054] The preparation process is: (1) 18 g linoleic acid, 3 g AA, 18 g trimethylolpropane, 0.2 g ZnO, 0.1 g LiOH, 0.2 g 4-methoxyphenol, 11.8 g DGBE and 9.19 g PnB were added to a 500 mL four-necked flask equipped with an electric stirrer, a condenser, a thermometer and a water separator (stirring rate 150 r / min). The oil bath was heated to 200 °C and the acid value was tested every 1 h. When the acid value of the system dropped to ≤15 mgKOH / g, the remaining linoleic acid was added and esterification was continued until the acid value was ≤8 mgKOH / g to obtain an alkyd resin.

[0055] (2) Cool to room temperature, add 2.1 g DMEA while stirring until the pH is 8-9, add deionized water and stir evenly to obtain an unmodified waterborne alkyd resin dispersion.

[0056] Comparative Example 2 This comparative example provides a water-based alkyd resin dispersion, which is different from Example 1 in that no acrylic acid (AA) is added during the esterification of the alkyd ester, and the raw material components are as follows in parts by mass: This embodiment provides a water-based alkyd resin dispersion, and the raw material components are as follows in parts by mass: Linoleic acid: 30g; Trimethylolpropane: 18g; Catalyst: zinc oxide (ZnO), lithium hydroxide (LiOH), 0.2g, 0.1g respectively; Inhibitor: 4-methoxyphenol, 0.2 g; Solvent: diethylene glycol monobutyl ether (DGBE), propylene glycol butyl ether (PnB), accounting for 18g and 14g respectively; Butyl acrylate (BA): 8g; Methyl methacrylate (MMA): 10g; Acrylic acid (AA): 5g; Vinyl crosslinking monomers: N -Hydroxyethyl acrylamide (HEAA), 1.5 g; Chain transfer agent: dodecyl mercaptan (SH), 0.3 g; Initiator: azobisisobutyronitrile (AIBN), 2 g; Silicone: β -(3,4-Epoxycyclohexyl)ethyltriethoxysilane (A-186): 4.92 g; Neutralizer: NN dimethylethanolamine (DMEA), 4g; Deionized water: 120g.

[0057] The preparation process is: (1) 18 g linoleic acid, 18 g trimethylolpropane, 0.2 g ZnO, 0.1 g LiOH, and 0.2 g 4-methoxyphenol were added to a 500 mL four-necked flask equipped with an electric stirrer, a condenser, a thermometer, and a water separator (stirring rate 150 r / min). The oil bath was heated to 200 °C and the acid value was tested every 1 h. When the acid value of the system dropped to ≤15 mgKOH / g, the remaining linoleic acid was added and esterification was continued until the acid value was ≤8 mgKOH / g to obtain an alcohol ester.

[0058] (2) 3.6 g DGBE, 2.8 g PnB, 2.16 g AA and 4.92 g A-186 were added sequentially into a 250 mL four-necked flask equipped with an electric stirrer and a thermometer (stirring rate 150 r / min). The flask was heated to 38 °C in a water bath and reacted for 1.5 h to obtain a silicone prepolymer reaction solution.

[0059] (3) Weigh 10 MMA, 8 g BA, 1.5 g HEAA, the remaining AA, 1.4 g AIBN, 0.3 g SH, 5.4 g DGBE, 4.2 g PnB and the mixed solution of the prepolymer reaction solution in step (2), and mix them evenly; adjust the temperature of the alkyd ester to 88°C, and add 5.4 g DGBE and 4.2 g PnB.

[0060] (4) Quickly drip 1 / 5 of the mixed solution of step (3) into the alkyd ester over a period of 25-30 min; then slowly drip the remaining mixed solution over a period of 2-3 h, then add the remaining initiator and solvent, and keep the mixture warm for 2-2.5 h to obtain a modified alkyd resin.

[0061] (5) Cooling to room temperature, adding 4 g of DMEA to step (4) while stirring until the pH is 8-9, adding deionized water and stirring evenly to obtain a waterborne alkyd resin dispersion.

[0062] Comparative Example 3 This comparative example provides a water-based alkyd resin dispersion, which differs from Example 1 in that no vinyl monomer is added. N -Hydroxyethyl acrylamide (HEAA), the raw material components are as follows by mass: This embodiment provides a water-based alkyd resin dispersion, and the raw material components are as follows in parts by mass: Linoleic acid: 30g; Trimethylolpropane: 18g; Catalyst: zinc oxide (ZnO), lithium hydroxide (LiOH), 0.2g, 0.1g respectively; Inhibitor: 4-methoxyphenol, 0.2 g; Solvent: diethylene glycol monobutyl ether (DGBE), propylene glycol butyl ether (PnB), accounting for 18g and 14g respectively; Butyl acrylate (BA): 8g; Methyl methacrylate (MMA): 10g; Acrylic acid (AA): 8g; Chain transfer agent: dodecyl mercaptan (SH), 0.3 g; Initiator: azobisisobutyronitrile (AIBN), 2 g; Silicone: β-(3,4-Epoxycyclohexyl)ethyltriethoxysilane (A-186): 4.92 g; Neutralizer: NN dimethylethanolamine (DMEA), 4g; Deionized water: 120g.

[0063] The preparation process is: (1) 18 g linoleic acid, 3 g AA, 18 g trimethylolpropane, 0.2 g ZnO, 0.1 g LiOH, and 0.2 g 4-methoxyphenol were added to a 500 mL four-necked flask equipped with an electric stirrer, a condenser, a thermometer, and a water separator (stirring rate 150 r / min). The oil bath was heated to 200 °C and the acid value was tested every 1 h. When the acid value of the system dropped to ≤15 mgKOH / g, the remaining linoleic acid was added and esterification was continued until the acid value was ≤8 mgKOH / g to obtain an alcohol ester.

[0064] (2) 3.6 g DGBE, 2.8 g PnB, 2.16 g AA and 4.92 g A-186 were added sequentially into a 250 mL four-necked flask equipped with an electric stirrer and a thermometer (stirring rate 150 r / min). The flask was heated to 38 °C in a water bath and reacted for 1.5 h to obtain a silicone prepolymer reaction solution.

[0065] (3) Weigh 10 MMA, 8 g BA, the remaining AA, 1.4 g AIBN, 0.3 g SH, 5.4 g DGBE, 4.2 g PnB and the mixed solution of the prepolymer reaction solution in step (2), and mix them evenly; adjust the temperature of the alkyd ester to 88°C, and add 5.4 g DGBE and 4.2 g PnB.

[0066] (4) Quickly drip 1 / 5 of the mixed solution of step (3) into the alkyd ester over a period of 25-30 min; then slowly drip the remaining mixed solution over a period of 2-3 h, then add the remaining initiator and solvent, and keep the mixture warm for 2-2.5 h to obtain a modified alkyd resin.

[0067] (5) Cooling to room temperature, adding 4 g of DMEA to step (4) while stirring until the pH is 8-9, adding deionized water and stirring evenly to obtain a waterborne alkyd resin dispersion.

[0068] Comparative Example 4 This comparative example provides a water-based alkyd resin dispersion, which differs from Example 1 in that no silicone prepolymer is added, and the raw material components are as follows in parts by mass: This embodiment provides a water-based alkyd resin dispersion, and the raw material components are as follows in parts by mass: Linoleic acid: 30g; Trimethylolpropane: 18g; Catalyst: zinc oxide (ZnO), lithium hydroxide (LiOH), 0.2g, 0.1g respectively; Inhibitor: 4-methoxyphenol, 0.2 g; Solvent: diethylene glycol monobutyl ether (DGBE), propylene glycol butyl ether (PnB), accounting for 18g and 14g respectively; Butyl acrylate (BA): 8g; Methyl methacrylate (MMA): 10g; Acrylic acid (AA): 5.84 g; Vinyl crosslinking monomers: N -Hydroxyethyl acrylamide (HEAA), 1.5 g; Chain transfer agent: dodecyl mercaptan (SH), 0.3 g; Initiator: azobisisobutyronitrile (AIBN), 2 g; Neutralizer: NN dimethylethanolamine (DMEA), 4g; Deionized water: 120g.

[0069] The preparation process is: (1) 18 g linoleic acid, 3 g AA, 18 g trimethylolpropane, 0.2 g ZnO, 0.1 g LiOH, and 0.2 g 4-methoxyphenol were added to a 500 mL four-necked flask equipped with an electric stirrer, a condenser, a thermometer, and a water separator (stirring rate 150 r / min). The oil bath was heated to 200 °C and the acid value was tested every 1 h. When the acid value of the system dropped to ≤15 mgKOH / g, the remaining linoleic acid was added and esterification was continued until the acid value was ≤8 mgKOH / g to obtain an alcohol ester.

[0070] (2) Weigh 10 MMA, 8 g BA, 1.5 g HEAA, the remaining AA, 1.4 g AIBN, 0.3 g SH, 9 g DGBE, and 7 g PnB mixed solution and mix well; adjust the temperature of the alkyd ester to 88 °C and add 5.4 g DGBE and 4.2 g PnB.

[0071] (3) Quickly drip 1 / 5 of the mixed solution of step (3) into the alkyd ester for 25-30 min; then slowly drip the remaining mixed solution for 2-3 h, then add the remaining initiator and solvent, and keep the reaction at this temperature for 2-2.5 h to obtain a modified alkyd resin.

[0072] (4) Cool the mixture to room temperature, add 4 g DMEA while stirring until the pH is 8-9, add deionized water and stir evenly to obtain a waterborne alkyd resin dispersion.

[0073] The synthesis and preparation mechanism of the waterborne alkyd resin dispersion obtained in Examples 1-4 is as follows Figure 1 As shown: first, alkyd esters and modified silicone prepolymers containing active vinyl double bonds are synthesized, then the vinyl monomers and modified silicone prepolymers are evenly mixed, and gradually added dropwise into the alkyd esters in a "fast and slow" manner to carry out free radical polymerization, and the silicone prepolymers, acrylates and alkyd esters with higher polarity are connected by chemical modification to finally obtain silicone / acrylate modified alkyd resins.

[0074] The DSC and TAG of the waterborne alkyd resin paint films obtained in Example 1 and Comparative Example 4 are as follows: Figure 2 As shown: It can be seen that the glass transition temperature of the resin in Comparative Example 4 without the introduction of silicone A-186 is 1.2°C, while the glass transition temperature of the resin in Example 1 with the introduction of silicone A-186 is increased to 9.3°C; and the paint film in Comparative Example 4 without the introduction of silicone A-186 begins to decompose at 200°C and is basically completely decomposed at 485°C, while the paint film in Example 1 with the introduction of silicone A-186 begins to decompose at 220°C and is basically completely decomposed at 500°C. This is because the resin polymer molecules introduce siloxy groups during the free radical polymerization process, and the silyl groups containing Si-O bonds have higher bond energy, which can shield and protect the chain segments below them. This shows that the introduction of silicone A-186 in Example 1 improves the thermal stability of the resin.

[0075] The SEM and EDS images of the cross-sections of the waterborne alkyd resin paint films obtained in Example 1, Comparative Example 1 and Comparative Example 2 are as follows: Figure 3 Described: Figure (a) is a cross-sectional SEM image of the paint film of the unmodified waterborne alkyd resin of Example 1, Figure (b) is a cross-sectional SEM image of the paint film of the physically mixed waterborne alkyd resin of Example 2 (a mixed solution of vinyl monomer and unmodified silicone is gradually added dropwise to the alkyd resin without active double bonds in a "fast and slow" manner for polymerization), Figure (c) is a cross-sectional SEM image of the paint film of the chemically grafted modified waterborne alkyd resin of Example 1, Figure (d) is a cross-sectional N element EDS image of the paint film of the chemically grafted modified waterborne alkyd resin of Example 1, and Figure (e) is a cross-sectional Si element EDS image of the paint film of the chemically grafted modified waterborne alkyd resin of Example 1. From Figure (a), we can see that the cross section of the unmodified alkyd resin film is smooth and flat, from Figure (b), we can see that the cross section of the physically mixed paint film is uneven and even has particle aggregation, showing an obvious phase separation state, from Figure (c), we can see that the cross section of the chemically grafted alkyd resin film has a clear texture structure and is in a homogeneous state, from Figures (d) and (e), we can observe that the N and Si elements contained in the chemically grafted alkyd resin film are evenly distributed in the film.

[0076] The multi-crosslinked film-forming mechanism of the waterborne alkyd resin dispersion obtained in Examples 1-4 is as follows Figure 4As shown in the figure, the following network crosslinking occurs during the film formation process of the dispersion: (1) the unsaturated vegetable oil acid introduced into the synthetic alkyd absorbs oxygen under the action of a catalyst to self-crosslink and form a network structure; (2) the vinyl crosslinking monomer copolymerized on the main chain of the resin generates hydrogen bonds through its own amide group to self-crosslink and form a network structure; (3) the hydroxyl groups contained in the vinyl crosslinking monomer copolymerized on the main chain of the resin undergo dehydration condensation with the silanol groups produced by the hydrolysis of the organosilicon to crosslink and form a network structure; (4) the vinyl crosslinking monomer copolymerized on the main chain of the resin undergoes hydrolysis condensation to crosslink and form a network structure; (5) the silanol groups produced by the hydrolysis of the organosilicon copolymerized on the main chain of the resin crosslink the hydroxyl groups on the surface of the substrate to form anchor points. The above multiple crosslinking reactions enable the resin film to exhibit excellent comprehensive properties at appropriate concentrations.

[0077] To further illustrate the waterborne alkyd resin dispersion disclosed in the present invention, the present invention also conducted corresponding tests on the resin dispersions and paint film properties of Examples 1-4 and Comparative Examples 1-4, as described below.

[0078] Preparation of resin film: Pour the dispersion into the prepared template or cast iron sheet, use a wire rod to paint the film evenly, and dry it at room temperature for 39 hours, 50% relative humidity. The cast iron sheet is used as the substrate for testing adhesion, hardness, impact resistance, solvent wiping resistance, water resistance, and aging resistance. The cast iron sheet is polished with 400 mesh sandpaper before spraying, and then wiped clean with solvent. The dry film thickness is about 30 μm. The specimen for testing tensile strength is 20 mm wide, 220 mm long, 0. 5-1. 0 mm thick, and 60 mm apart.

[0079] Resin performance test: (1) The glass transition temperature and thermal weight loss of the resin were tested by differential scanning calorimetry and thermogravimetric analysis, respectively, with a heating rate of 10°C / min; (2) Resin thermal storage stability test: The thermal storage stability of the resins prepared in the examples and comparative examples was tested according to the method of GB / T 6753.3-1986; (3) The resin appearance is tested according to GB / T1772-1992 method.

[0080] Paint film performance test: (1) Paint film hardness test: The hardness of the resin paint films prepared in the examples and comparative examples was tested according to the method of GB / T6739-2006; (2) Impact resistance test of paint films: The flexibility of the resin paint films prepared in the examples and comparative examples was tested according to the method of GB / T 1732-1993; (3) Paint film adhesion test: The adhesion of the resin paint films prepared in the examples and comparative examples was tested according to the method of GB / T9286-2021; (4) Water resistance test of paint film: GB / T1733-1993 standard was used to test the water resistance of the resin paint films in the examples and comparative examples. If there was no blistering, no peeling, no rusting, and slight discoloration was allowed, it was considered to have passed the test; (5) Solvent resistance test of paint film: GB / T23989-2009 (Method B) standard was used to test the solvent resistance of the resin paint film in the examples and comparative examples. Two test panels were prepared from the same sample for parallel testing. The solvent used was xylene. The panels were wiped 25 times at room temperature. If one of the two test panels did not expose the substrate, it was rated as "passed"; (6) Paint film aging resistance test: GB / T 1865-2009 standard was used to test the aging resistance of the resin paint films in the examples and comparative examples, and the rating was carried out in accordance with the provisions of GB / T 1766-2008.

[0081] (7) Paint film tensile strength test: GB / T 1040.3-2006 standard was used, the tensile rate was 100 mm / min, each sample was tested 5 times, after discarding the maximum and minimum values, the average of the remaining three values ​​was taken as the final test result; (8) Test of paint film cross-linking degree: The cross-linking degree of the paint film was tested by Soxhlet extraction. Ethyl acetate was used as the solvent and a certain amount of paint film was weighed. After Soxhlet extraction for 24 h, the paint film was taken out and dried to a constant mass and weighed. The cross-linking degree was calculated according to formula (1).

[0082] Formula (1) Where: m 1 —Total mass of the paint film after extraction, g; m 2 —Total mass of the paint film before extraction, g.

[0083] The results of the above tests are shown in Table 1.

[0084] Among them, the difference between Comparative Example 1 and Example 1 is that the water-based alkyd resin dispersion in Comparative Example 1 is unmodified, and the proportions of other components remain unchanged; the difference between Comparative Example 2 and Example 1 is that the water-based alkyd resin dispersion prepared by the physical mixing method in Comparative Example 2, and the other components remain unchanged; the difference between Comparative Example 3 and Example 1 is that no vinyl crosslinking monomer (HEAA) is added in Comparative Example 3, and the other components remain unchanged; the difference between Comparative Example 4 and Example 1 is that no silicone (A-186) is added in Comparative Example 4, and the other components remain unchanged.

[0085] Table 1 Test results of Examples 1-4 and Comparative Examples 1-4 As can be seen from Table 1, the waterborne alkyd resin dispersion prepared by the present invention has good appearance and good storage stability, and the paint film has high hardness (H) and impact resistance (48 kg·cm), and also shows excellent aging resistance and medium resistance.

[0086] The present invention also makes a comprehensive comparison between Example 1 and Comparative Examples 1-4, which are as follows: (1) Example 1, Comparative Example 1 and Comparative Example 2, Comparative Example 1 is an unmodified waterborne alkyd resin, and Comparative Example 2 is a physically mixed waterborne alkyd resin. It can be seen from the SEM image that the cross section of the unmodified waterborne alkyd resin paint film is smooth and flat ( Figure 3 a) The cross section of the physically mixed waterborne alkyd resin paint film is uneven, and even particles aggregate, showing an obvious phase separation state ( Figure 3 b), while the cross section of the chemically grafted waterborne alkyd resin paint film has a distinct texture structure and is in a homogeneous state ( Figure 3 c), indicating that chemical bonds bind polymers with poor polarity together, effectively improving their compatibility. Compared with unmodified alkyd resins, physically mixed waterborne alkyd resins can undergo the above-mentioned multiple cross-linking film-forming reactions, making the paint film have a high degree of cross-linking (77%) and high hardness (H), but compared with chemically modified alkyd resins, the paint film has a low tensile strength (1.8MPa), and is not resistant to water, solvents, and aging. This is mainly because this polymer is a physical mixture of multiple polymers, which leads to a decrease in the degree of bonding between polymer chains, uneven distribution of reactive groups, and inability to fully exert the synergistic effect of polymers.

[0087] (2) Example 1, Comparative Example 3 and Comparative Example 4, Comparative Example 3 is a case where no vinyl crosslinking monomer (HEAA) is added, and other components remain unchanged, while Comparative Example 4 is a case where no silicone A-186 is added, and other components remain unchanged. As shown in Table 1, the waterborne alkyd resin dispersion without silicone A-186 has a small amount of sedimentation and crusting after storage at 50°C for 30 days (Comparative Example 4), while the waterborne alkyd resin dispersion with silicone A-186 has good thermal storage stability (Comparative Example 3), which is due to the cyclic molecule at one end of the silicone (A-186 or A-187) and the isopropyl group at the other end, which makes the polymer sterically hindered. In addition, compared with the unmodified waterborne alkyd resin, the hardness of the modified waterborne alkyd resin film without HEAA is significantly improved (B), and the impact resistance is 37 kg.cm, and the impact resistance of the modified waterborne alkyd resin film without silicone A-186 is significantly improved (42 kg.cm), and the hardness is 2B. It is not difficult to find that the introduction of HEAA improves the flexibility of the paint film more than the introduction of A-186. This is because the self-crosslinking of HEAA is formed by physical hydrogen bonds between or within molecules, which can dynamically disperse the impact resistance of the outside world; while the introduction of A-186 improves the hardness of the paint film more than the introduction of HEAA. This is because A-186 undergoes hydrolysis and condensation during the film formation process to form a large number of Si-O-Si bonds, which restricts the freedom of movement between polymer molecules, increases its rigidity, and can resist external pressure. Therefore, when HEAA and A-186 are introduced at the same time (Example 1), the hardness and impact resistance of the paint film are increased to H and 48 kg·cm respectively, making it show the characteristics of both rigidity and flexibility, and other properties are also significantly improved.

[0088] In summary, the water-based alkyd resin dispersion and preparation method proposed in the present invention can solve the technical problems of poor storage stability of water-based acrylic resin, difficulty in balancing the hardness and impact resistance of the paint film, poor aging resistance and medium resistance, etc. The prepared resin has good appearance, low cost, is green and environmentally friendly, and has broad market application value.

[0089] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a waterborne alkyd resin dispersion, characterized in that: Here are the steps: (1) unsaturated vegetable oil acid accounting for 50-70 wt% of the raw material components, acrylic acid accounting for 30-45 wt% of the raw material components, trimethylolpropane, a catalyst, and a polymerization inhibitor are mixed to carry out esterification reaction, and when the acid value of the system drops to ≤15 mgKOH / g, the remaining unsaturated vegetable oil acid is added, and the esterification is continued until the acid value is ≤8 mgKOH / g to obtain an alcohol acid ester; (2) mixing and reacting a solvent accounting for 15-25 wt% of the raw material components, acrylic acid accounting for 20-30 wt% of the raw material components, and organosilicon to obtain an organosilicon prepolymer reaction liquid; (3) uniformly mixing a mixed solution of methyl methacrylate, butyl acrylate, a vinyl crosslinking monomer, remaining acrylic acid, an initiator accounting for 65-75 wt % of the raw material components, a chain transfer agent, a solvent accounting for 25-35 wt % of the raw material components, and the silicone prepolymer reaction solution of step (2); (4) adjusting the temperature of the alkyd ester of step (1) to 80-140° C., adding 25-35 wt % of a solvent based on the raw material components, and then adding the mixed solution of step (3), the remaining solvent and the remaining initiator, and continuing the reaction for 2-2.5 h to obtain an alkyd resin; (5) The reaction system of step (4) is cooled to room temperature, a neutralizing agent is added while stirring until the pH value is 8-9, and deionized water is added and stirred evenly to obtain a waterborne alkyd resin dispersion.

2. The method for preparing the aqueous alkyd resin dispersion according to claim 1, characterized in that: The mass ratio of acrylic acid to alkyd ester in step (1) is 1:(17-22); the mass ratio of acrylic acid to alkyd ester in step (4) is 1:(2.1-2.4), the mass ratio of silicone to alkyd ester is 1:(8-12); the mass ratio of vinyl crosslinking monomer to acrylic acid ester is 1:(22-42).

3. The method for preparing the aqueous alkyd resin dispersion according to claim 1, characterized in that: The raw material components and weight parts of the water-based alkyd resin dispersion are: 22-30 parts of unsaturated vegetable oil acid, 16-18 parts of trimethylolpropane, 0.05-0.3 parts of catalyst, 0.1-0.2 parts of inhibitor, 28-32 parts of solvent, 6-8 parts of butyl acrylate, 8-10 parts of methyl methacrylate, 6-8 parts of acrylic acid, 3.69-4.92 parts of silicone, 1-2.2 parts of vinyl crosslinking monomer, 0.1-0.3 parts of chain transfer agent, 1-4 parts of initiator, 2-4 parts of neutralizer and 100-120 parts of deionized water.

4. The method for preparing a waterborne alkyd resin dispersion according to claim 1, characterized in that: The temperature of the esterification reaction in step (1) is 180-220° C.; the reaction conditions in step (2) are 35-50° C. and the reaction time is 1-2 hours.

5. The method for preparing the waterborne alkyd resin dispersion according to claim 1, characterized in that: In step (4), the mixed solution is added in two times. The first time, 15-25 wt% of the mixed solution is added, and the addition time is 25-30 min. The second time, the remaining mixed solution is added, and the addition time is 2-3 h.

6. The method for preparing the aqueous alkyd resin dispersion according to any one of claims 1 to 3, characterized in that: The unsaturated vegetable oil acid is dehydrated ricinoleic acid or linoleic acid, wherein the iodine value of the unsaturated vegetable oil is greater than 160 g / 100g.

7. The method for preparing the aqueous alkyd resin dispersion according to any one of claims 1 to 3, characterized in that: The organosilicon is β-(3,4-epoxycyclohexyl)ethyltriethoxysilane or β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; The vinyl crosslinking monomer is N - Hydroxymethyl acrylamide, N -Hydroxyethyl acrylamide or N -Methoxyacrylamide.

8. The method for preparing the aqueous alkyd resin dispersion according to any one of claims 1 to 3, characterized in that: The solvent is a combination of diethylene glycol monobutyl ether and propylene glycol butyl ether, and the mass ratio of the two is (1.1-1.5):1; the catalyst is a combination of zinc oxide and lithium hydroxide, and the mass ratio of the two is 2:1; the chain transfer agent is dodecyl mercaptan or 3-mercapto-1-propanol.

9. The method for preparing the aqueous alkyd resin dispersion according to any one of claims 1 to 3, characterized in that: The initiator is azobisisobutyronitrile, dibenzoyl peroxide or di-tert-butyl peroxide; the inhibitor is one or a combination of any two of p-hydroxyanisole, hydroquinone and 4-methoxyphenol; and the neutralizer is triethylamine or NN dimethylethanolamine.

10. A waterborne alkyd resin dispersion, characterized in that: The waterborne alkyd resin dispersion is prepared by the method according to any one of claims 1 to 9.

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