A reaction kettle, a method for preparing water-dispersible alkyd protective coating by using the reaction kettle and a protective coating obtained by using the method

Abstract

The application discloses a reaction kettle, a method for preparing water-dispersible alkyd protective paint by using the reaction kettle and the protective paint obtained by using the method, and relates to the technical field of paint preparation. The reaction kettle comprises a kettle body, a kettle cover and a jacket assembly. The kettle cover is installed on the kettle body. A jacket assembly for adjusting the reaction temperature is installed on the outer wall of the kettle body. A driving mechanism for driving the jacket assembly to switch different temperature heat conduction surfaces is further installed on the kettle body. A stirring mechanism for stirring materials is installed on the kettle cover. A heat preservation assembly for heat preservation is arranged outside the jacket assembly. The reaction kettle can quickly regulate the reaction temperature by the arrangement of the jacket assembly and the driving mechanism, thereby improving the timeliness and accuracy of the reaction temperature regulation, and further improving the quality of the alkyd protective paint.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of paint preparation, in particular to a reaction kettle, a method for preparing water-dispersible alkyd protective paint by using the reaction kettle and the protective paint obtained by using the method. BACKGROUND

[0002] Alkyd resin is prepared by polycondensation of polyfunctional alcohol, polybasic acid and vegetable oil or vegetable oil acid. During the preparation of alkyd resin, the reaction temperature needs to be adjusted multiple times. The existing reaction kettle is provided with a fixed jacket outside the kettle body. The reaction temperature is controlled by circulating heat-conducting medium (such as heat-conducting oil, water or gas) into the fixed jacket. This temperature control method needs to adjust the temperature of the heat-conducting medium. The heat-conducting medium needs a certain time to heat up and cool down. When the number of reaction temperature changes is large and the temperature control requirement is high, it is difficult to meet the requirement of rapid control of reaction temperature. If the reaction temperature needs to be adjusted, the heat-conducting medium in the fixed jacket needs to be replaced after waiting for the heat-conducting medium to heat up or cool down, so that the kettle body can play a main role in temperature control and adjustment. In fact, the reaction materials in the kettle body are still reacting at the previous temperature during this buffer period. The reaction kettle is difficult to rapidly and accurately adjust the reaction temperature, which has a certain impact on the quality of the alkyd resin and alkyd protective paint. SUMMARY

[0003] The present application aims to provide a water-dispersible alkyd protective paint which is not easy to break emulsion, so as to solve the problems existing in the prior art in the background.

[0004] To achieve the above-mentioned purpose, the present application provides the following technical scheme:

[0005] A reaction kettle comprises a kettle body, a kettle cover and a jacket assembly. The kettle cover is installed on the kettle body. A jacket assembly for adjusting the reaction temperature is installed on the outer wall of the kettle body. A driving mechanism for driving the jacket assembly to switch different temperature heat-conducting surfaces is installed on the kettle body. A stirring mechanism for stirring the materials is installed on the kettle cover. A heat preservation assembly for heat preservation of the jacket assembly is installed outside the jacket assembly.

[0006] Preferably, the jacket assembly comprises a mounting ring mounted on the side wall of the kettle body, a sliding frame, a sliding rail and a thermal insulation plate, the sliding frame is circumferentially and equidistantly distributed on the mounting ring, the sliding rail is mounted on the sliding frame, a sliding block is slidably connected to the sliding rail, a temperature guide block is connected to the sliding block through a shaft, the outer wall of the temperature guide block is provided with a circular arc surface capable of being attached to the outer wall of the kettle body, and the inside of the temperature guide block is a hollow cavity, the thermal insulation plate divides the inside of the temperature guide block into two or more cavities, each cavity is provided with an independent temperature guide medium inlet and outlet, the temperature guide medium inlets and outlets of the corresponding cavities of the temperature guide block on the mounting ring are connected in series through pipelines, a first gear is connected to the shaft of the temperature guide block through a one-way bearing, and a rack capable of being engaged with the first gear is connected to the sliding frame.

[0007] Preferably, the driving mechanism comprises a rotating ring, a driving frame and a gear ring, the rotating ring is rotatably connected to the kettle body, the driving frame is circumferentially and equidistantly connected to the rotating ring, the connecting shaft of the temperature guide block slides in the driving frame, the gear ring is fixedly connected to the rotating ring, and a first motor is mounted on the kettle body.

[0008] Preferably, the stirring mechanism comprises a stirring rod, a stirring blade and a second motor, the stirring rod is rotatably connected to the kettle cover, the stirring blade is connected to the stirring rod, and a second motor for driving the stirring rod to rotate is mounted on the kettle cover.

[0009] Preferably, the heat preservation assembly comprises a heat preservation block, a return spring and a push block, the heat preservation block is slidably connected to the sliding frame, and the heat preservation block can be attached to and separated from the surface of the temperature guide block, the inside of the sliding block is provided with a return spring for driving the heat preservation block and the temperature guide block to slide close to each other, and the inside of the sliding block is further provided with a push block for driving the heat preservation block and the temperature guide block to move away from each other, a push rod is connected to the push block, and a driving plate for pushing the push rod is connected to the sliding frame.

[0010] Preferably, the kettle cover is provided with a feeding port and a temperature detector, and the bottom of the kettle body is provided with a discharging port.

[0011] The application also provides a method for preparing a water-dispersible alkyd resin, comprising the following steps:

[0012] S1: 28-32 parts by weight of linolenic acid, 10-12 parts by weight of epoxy resin, 0.1-0.2 parts by weight of zinc oxide, 2-3 parts by weight of dimethylbenzene, 3-5 parts by weight of benzoic acid, 10-12 parts by weight of pentaerythritol, 9-10 parts by weight of phthalic anhydride, 14-15 parts by weight of sec-butyl alcohol and 13-15 parts by weight of ethylene glycol butyl ether are weighed;

[0013] S2: linoleic acid, epoxy resin, zinc oxide, dimethylbenzene, sec-butyl alcohol and ethylene glycol butyl ether are added into a reaction kettle, the temperature is raised to 190 DEG C and kept for 2h, then benzoic acid, pentaerythritol and phthalic anhydride are added, the temperature is raised to 180-200 DEG C, and kept until the acid value is 10-15 mgKOH / g, and then the temperature is reduced to below 150 DEG C to obtain an epoxy modified alkyd resin;

[0014] S3: the epoxy modified alkyd resin is water-based to obtain a water-dispersible alkyd resin;

[0015] The reaction kettle is controlled in temperature by a variable jacket.

[0016] Preferably, the specific steps for water-based modification of the epoxy modified alkyd resin are as follows: 3-4 parts by weight of styrene, 10-12 parts by weight of methacrylic acid, 2-3 parts by weight of acrylic acid, 1-2 parts by weight of butyl acrylate and 0.3-0.6 parts by weight of benzoyl peroxide are weighed and mixed to form a mixed solution, the epoxy modified alkyd resin in the reaction kettle is heated to 120 DEG C, the mixed solution is added dropwise into the reaction kettle and kept for 1h, the reaction is stopped when the solid content of the modified alkyd resin is 70% and the acid value is 45 mgKOH / g, and the modified alkyd resin is diluted with distilled water to a solid content of 40% when the temperature is reduced to 50 DEG C to obtain a water-dispersible alkyd resin.

[0017] The application also provides a water-dispersible alkyd protective coating which is not easy to break emulsion and comprises the following components: 50 parts by weight of water-dispersible alkyd resin, 1 part by weight of water-based dispersing agent, 0.3 part by weight of water-based defoaming agent, 3 parts by weight of pigment powder, 5 parts by weight of talc, 12 parts by weight of precipitated barium sulfate, 10 parts by weight of zinc phosphate, 0.5 part by weight of water-based catalyst, 0.2 part by weight of anti-flash rust agent, 0.2 part by weight of thickening agent and 10 parts by weight of deionized water.

[0018] Compared with the prior art, the application has the following beneficial effects:

[0019] 1、The reaction kettle in the application can realize rapid regulation of reaction temperature through the setting of the jacket assembly and the driving mechanism, the temperature regulation time and the circulation time of the temperature regulation medium in the jacket are saved by setting multiple cavities in the temperature guide block and adjusting the temperature regulation medium in the cavity to the required temperature in advance, so that the material in the kettle body can quickly reach the required reaction temperature when rapid temperature regulation is needed, the timeliness and accuracy of the reaction temperature regulation are improved, and the quality of the alkyd protective coating is improved, and the alkyd protective coating is not easy to break emulsion and the stability of the coating is improved through reasonable use amount of film forming additives and proportioning of other components.

[0020] 2、The reaction kettle in the application can carry out heat preservation treatment on the heat conduction block and the kettle body through the setting of the heat preservation assembly, reduces the loss of energy, and can promote the kettle body to reach the required reaction temperature more quickly, and because the outer wall of the heat conduction block is provided with a plurality of arc surfaces, the heat preservation block needs to be separated from the heat conduction block when the heat conduction block switches the heat conduction surface, and the heat preservation block needs to be attached to the heat conduction block after the switching is completed, the driving mechanism can synchronously drive the heat conduction block to switch the heat conduction surface and the automatic separation and attachment of the heat preservation block and the heat conduction block, without adding an independent power and control mechanism to the heat preservation assembly, thereby reducing the cost of the reaction kettle, and the heat preservation block and the heat conduction block can keep stable separation and attachment timing, thereby improving the working stability of the reaction kettle. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 and Figure 2 is the overall structure schematic diagram of different angles of the application.

[0022] Figure 3 is the partial enlarged structure schematic diagram of A in the application. Figure 1

[0023] Figure 4 is the kettle body cross-section structure schematic diagram of the application.

[0024] Figure 5 is the partial structure schematic diagram of the jacket assembly of the application.

[0025] Figure 6 is the partial enlarged structure schematic diagram of B in the application. Figure 5

[0026] Figure 7 is the driving mechanism structure schematic diagram of the application.

[0027] Figure 8 is the slider cross-section structure schematic diagram of the application.

[0028] Figure 9 is the heat conduction block cross-section structure schematic diagram of the application.

[0029] Figure 10 is the flow chart of preparing the water dispersible alkyd protective coating of the application.

[0030] ​​In the figure: 1, kettle body; 2, kettle cover; 3, jacket assembly; 31, mounting ring; 32, sliding frame; 33, sliding rail; 34, sliding block; 35, temperature guide block; 36, first gear; 37, rack; 38, temperature insulation plate; 4, driving mechanism; 41, rotating ring; 42, driving frame; 43, gear ring; 44, first motor; 45, second gear; 5, stirring mechanism; 51, stirring rod; 52, stirring blade; 53, second motor; 6, feed inlet; 7, temperature detector; 8, discharge outlet; 9, heat preservation assembly; 91, heat preservation block; 92, return spring; 93, push block; 94, push rod; 95, driving plate. DETAILED DESCRIPTION

[0031] In order to make the technical means, creative features, purposes and effects of the present application easy to understand, the present application is further described below in conjunction with specific embodiments.

[0032] Please refer to Figures 1-10 The present application provides a technical solution:

[0033] A reaction kettle, comprising a kettle body 1, a kettle cover 2 and a jacket assembly 3, the kettle cover 2 is installed on the kettle body 1, the kettle cover 2 is provided with a feed inlet 6 and a temperature detector 7, and the bottom of the kettle body 1 is provided with a discharge outlet 8; the outer wall of the kettle body 1 is provided with a jacket assembly 3 for adjusting the reaction temperature, the jacket assembly 3 comprises a mounting ring 31, a sliding frame 32, a sliding rail 33 and a temperature insulation plate 38 mounted on the side wall of the kettle body 1, the sliding frame 32 is circumferentially and equidistantly distributed on the mounting ring 31, the sliding rail 33 is mounted on the sliding frame 32, the sliding rail 33 is slidably connected with a sliding block 34, the sliding block 34 is connected with a temperature guide block 35 through a shaft, the outer wall of the temperature guide block 35 is provided with a circular arc surface capable of being attached to the outer wall of the kettle body 1, and the inside of the temperature guide block 35 is a hollow cavity, the temperature insulation plate 38 divides the inside of the temperature guide block 35 into two or more cavities, each cavity is provided with an independent temperature guide medium inlet and outlet, the temperature guide medium inlets and outlets of the cavities corresponding to the temperature guide block 35 on the mounting ring 31 are connected in series through pipelines, the shaft of the temperature guide block 35 is connected with a first gear 36 through a one-way bearing, and the sliding frame 32 is connected with a rack 37 capable of being engaged with the first gear 36, three cavities are provided in the temperature guide block 35 in the present solution, and independent temperature guide media are introduced into the three cavities, and the rotation of the temperature guide block 35 is used to realize the control of the reaction temperature.

[0034] The kettle body 1 is also provided with a driving mechanism 4 for driving the jacket assembly 3 to switch different temperature heat conduction surfaces, the driving mechanism 4 comprises a rotating ring 41, a driving frame 42 and a gear ring 43, the rotating ring 41 is rotationally connected to the kettle body 1, the driving frame 42 is circumferentially equidistantly connected to the rotating ring 41, the connecting shaft on the temperature guide block 35 slides in the driving frame 42, the rotating ring 41 is fixedly connected with the gear ring 43, the kettle body 1 is provided with a first motor 44, the output end of the first motor 44 is keyed with a second gear 45 engaged with the gear ring 43, the setting of the driving mechanism 4 facilitates synchronous control of the rotation and switching of all the temperature guide blocks 35, and the switched temperature guide surface is attached to the kettle body 1, and the attachment and separation of the heat preservation assembly 9 and the jacket assembly 3 can be simultaneously realized.

[0035] The kettle cover 2 is provided with a stirring mechanism 5 for stirring the material, the stirring mechanism 5 comprises a stirring rod 51, a stirring blade 52 and a second motor 53, the stirring rod 51 is rotationally connected to the kettle cover 2, the stirring rod 51 is connected with the stirring blade 52, and the kettle cover 2 is provided with a second motor 53 for driving the stirring rod 51 to rotate, the stirring mechanism 5 facilitates the stirring and mixing of the material, so that the material reaction is more sufficient.

[0036] The jacket assembly 3 is externally provided with a heat preservation assembly 9 for heat preservation, the heat preservation assembly 9 comprises a heat preservation block 91, a return spring 92 and a push block 93, the heat preservation block 91 is slidingly connected to the sliding frame 32, and the heat preservation block 91 can be attached to and separated from the surface of the temperature guide block 35, the sliding block 34 is internally provided with the return spring 92 for driving the heat preservation block 91 to slide close to the temperature guide block 35, and the sliding block 34 is further provided with the push block 93 for pushing the heat preservation block 91 and the temperature guide block 35 to move away from each other, the push block 93 is connected with a push rod 94, the sliding frame 32 is connected with a driving plate 95 for pushing the push rod 94, the heat preservation block 91 and the temperature guide block 35 are correspondingly arranged, the heat preservation assembly 9 can heat preservation the temperature guide medium in the temperature guide block 35, reduce the energy loss, promote the kettle body 1 to reach the required reaction temperature more quickly, and because the outer wall of the temperature guide block 35 is provided with a plurality of arc surfaces, the heat preservation block 91 needs to be separated from the temperature guide block 35 when the temperature guide block 35 switches the heat conduction surface, and the heat preservation block 91 needs to be attached to the temperature guide block 35 for heat preservation after the switching is completed, the driving mechanism 4 can synchronously drive the temperature guide block 35 to switch the heat conduction surface and the automatic separation and attachment of the heat preservation block 91 and the temperature guide block 35, without the need to additionally provide independent power and control mechanism for the heat preservation assembly 9, thereby reducing the cost of the reaction kettle, and the heat preservation block 91 and the temperature guide block 35 can be kept in stable separation and attachment time, thereby facilitating the rotation switching and heat preservation treatment of the temperature guide block 35.

[0037] A method for preparing a water-dispersible alkyd resin, comprising the following steps:

[0038] S1: 28-32 parts by weight of linolenic acid, 10-12 parts by weight of epoxy resin, 0.1-0.2 parts by weight of zinc oxide, 2-3 parts by weight of dimethylbenzene, 3-5 parts by weight of benzoic acid, 10-12 parts by weight of pentaerythritol, 9-10 parts by weight of phthalic anhydride, 14-15 parts by weight of sec-butyl alcohol, 13-15 parts by weight of ethylene glycol butyl ether;

[0039] S2: the linolenic acid, epoxy resin, zinc oxide, dimethylbenzene, sec-butyl alcohol and ethylene glycol butyl ether are added to the reaction kettle, the temperature is raised to 190℃ and maintained for 2h, then the benzoic acid, pentaerythritol and phthalic anhydride are added and the temperature is raised to 180-200℃, and maintained until the acid value is 10-15mgKOH / g, then the temperature is reduced to below 150℃ to obtain an epoxy-modified alkyd resin;

[0040] S3: the epoxy-modified alkyd resin is water-based to obtain a water-dispersible alkyd resin;

[0041] The reaction kettle controls the reaction temperature by a variable jacket.

[0042] The specific steps of water-based modification of the epoxy-modified alkyd resin are as follows: 3-4 parts by weight of styrene, 10-12 parts by weight of methacrylic acid, 2-3 parts by weight of acrylic acid, 1-2 parts by weight of butyl acrylate and 0.3-0.6 parts by weight of benzoyl peroxide are weighed and mixed to form a mixed solution, the epoxy-modified alkyd resin in the reaction kettle is heated to 120℃, the mixed solution is added dropwise into the reaction kettle and kept for 1h, the reaction is stopped when the solid content of the modified alkyd resin is 70% and the acid value is 45mgKOH / g, the temperature is reduced to 50℃, and distilled water is added to dilute the modified alkyd resin to a solid content of 40% to obtain a water-dispersible alkyd resin.

[0043] A water-dispersible alkyd protective coating which is not easy to break emulsion, comprising the following components: 50 parts by weight of water-dispersible alkyd resin, 1 part by weight of water-based dispersant, 0.3 parts by weight of water-based defoamer, 3 parts by weight of pigment powder, 5 parts by weight of talc, 12 parts by weight of precipitated barium sulfate, 10 parts by weight of zinc phosphate, 0.5 parts by weight of water-based catalyst, 0.2 parts by weight of anti-flash rust agent, 0.2 parts by weight of thickening agent and 10 parts by weight of deionized water.

[0044] The working process of the above reaction kettle is as follows:

[0045] The materials are added into the kettle body 1 through the feeding port 6, the second motor 53 is started to drive the stirring rod 51 to rotate, so that the stirring rod 51 drives the stirring blade 52 to stir and mix the materials; different temperature guide temperature medium is introduced into the three cavities of the temperature guide block 35, the cavity of the temperature guide block 35 which is in contact with the kettle body 1 controls the reaction temperature, so that the materials react at the set temperature, and the guide temperature medium in the other two cavities reaches the next control temperature before the previous reaction temperature ends.

[0046] When the reaction temperature needs to be quickly regulated, the first motor 44 is started to drive the second gear 45 to rotate, the second gear 45 drives the rotating ring 41 to rotate through the gear ring 43, so that the rotating ring 41 drives the driving frame 42 connected thereon to rotate, the driving frame 42 has a certain angle relative to the sliding frame 32, the driving frame 42 drives the sliding block 34 to slide on the slide rail 33, so that the temperature guide block 35 moves away from the kettle body 1, in the process of sliding of the sliding block 34, the driving plate 95 pushes the push rod 94, so that the inclined surface provided on the push block 93 pushes the heat preservation block 91, so that the heat preservation block 91 slides on the sliding block 34 and separates from the temperature guide block 35.

[0047] When the first gear 36 on the temperature guide block 35 engages with the rack 37, the first gear 36 drives the temperature guide block 35 to rotate in the process of moving, and stops rotating after rotating 120°, so that the other face of the temperature guide block 35 corresponding to the cavity reaching the regulated temperature faces the kettle body 1; the first motor 44 reversely rotates to reversely rotate the rotating ring 41, the driving frame 42 drives the temperature guide block 35 to slide close to the kettle body 1, until the temperature guide block 35 is attached to the surface of the kettle body 1, in this process, the temperature guide block 35 does not rotate under the action of the one-way bearing, the temperature guide medium in the temperature guide block 35 that has reached the regulated temperature is used to regulate the reaction temperature in the kettle body 1, so that the reaction temperature is quickly and efficiently regulated, when the temperature guide block 35 is attached to the surface of the kettle body 1, the heat preservation block 91 is reset under the action of the reset spring 92 and is attached to the temperature guide block 35, so as to play a heat preservation role on the temperature guide block 35 and the kettle body 1.

[0048] Although the embodiments of the present application have been shown and described, it can be understood by those skilled in the art that various changes, modifications, replacements and variations can be made to the embodiments without departing from the principles and spirits of the present application, the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A reaction vessel, characterized in that, The reactor includes a vessel body (1), a vessel cover (2), and a jacket assembly (3). The vessel cover (2) is installed on the vessel body (1). The jacket assembly (3) for adjusting the reaction temperature is installed on the outer wall of the vessel body (1). The vessel body (1) is also equipped with a drive mechanism (4) for driving the jacket assembly (3) to switch different temperature heat conduction surfaces. The vessel cover (2) is equipped with a stirring mechanism (5) for stirring the material. The jacket assembly (3) is equipped with a heat preservation component (9) for heat preservation. The jacket assembly (3) includes an mounting ring (31), a sliding frame (32), a slide rail (33), and a heat insulation plate (38) mounted on the side wall of the vessel body (1). The sliding frame (32) is equidistantly distributed on the mounting ring (31) around its circumference. The slide rail (33) is mounted on the sliding frame (32). A slider (34) is slidably connected to the slide rail (33). A heat-conducting block (35) is connected to the slider (34) via a shaft. The outer wall of the heat-conducting block (35) is provided with a circular shape that can fit against the outer wall of the vessel body (1). The temperature-conducting block (35) has an arc surface and a hollow cavity inside. The insulation plate (38) divides the inside of the temperature-conducting block (35) into two or more cavities. Each cavity is provided with an independent temperature-conducting medium inlet and outlet. The temperature-conducting medium inlet and outlet of the cavity corresponding to the temperature-conducting block (35) on the mounting ring (31) are connected in series through pipes. The shaft of the temperature-conducting block (35) is connected to a first gear (36) through a one-way bearing. The sliding frame (32) is connected to a rack (37) that can mesh with the first gear (36). The driving mechanism (4) includes a rotating ring (41), a driving frame (42), and a gear ring (43). The rotating ring (41) is rotatably connected to the vessel body (1). The driving frame (42) is circumferentially connected to the rotating ring (41). The connecting shaft on the temperature-conducting block (35) slides inside the driving frame (42). The gear ring (43) is fixedly connected to the rotating ring (41). A first motor (44) is installed on the vessel body (1). The output end of the first motor (44) is keyed to a second gear (45) that meshes with the gear ring (43). The heat preservation component (9) includes a heat preservation block (91), a reset spring (92), and a push block (93). The heat preservation block (91) is slidably connected to the sliding frame (32), and the heat preservation block (91) can be attached to and separated from the surface of the heat-conducting block (35). The slider (34) is provided with a reset spring (92) for driving the heat preservation block (91) and the heat-conducting block (35) to slide closer together. The slider (34) is also provided with a push block (93) for pushing the heat preservation block (91) and the heat-conducting block (35) away from each other. A push rod (94) is connected to the push block (93), and a drive plate (95) for pushing the push rod (94) is connected to the sliding frame (32).

2. The reaction vessel according to claim 1, characterized in that: The stirring mechanism (5) includes a stirring rod (51), a stirring blade (52) and a second motor (53). The stirring rod (51) is rotatably connected to the lid (2), and the stirring blade (52) is connected to the stirring rod (51). The lid (2) is equipped with a second motor (53) for driving the stirring rod (51) to rotate.

3. A reaction vessel according to claim 1, characterized in that: The lid (2) is provided with a feed inlet (6) and a thermometer (7), and the bottom of the body (1) is provided with a discharge outlet (8).

4. A method for preparing a water-dispersible alkyd resin using the reaction vessel according to any one of claims 1-3, characterized in that, Includes the following steps: S1: Weigh out the following materials: 28-32 parts by weight of linoleic acid, 10-12 parts by weight of epoxy resin, 0.1-0.2 parts by weight of zinc oxide, 2-3 parts by weight of xylene, 3-5 parts by weight of benzoic acid, 10-12 parts by weight of pentaerythritol, 9-10 parts by weight of phthalic anhydride, 14-15 parts by weight of sec-butanol, and 13-15 parts by weight of ethylene glycol butyl ether. S2: Linoleic acid, epoxy resin, zinc oxide, xylene, sec-butanol and ethylene glycol butyl ether are added to a reaction vessel, the temperature is raised to 190°C and held for 2 hours, then benzoic acid, pentaerythritol and phthalic anhydride are added and the temperature is raised to 180~200°C and held until the acid value is 10~15mgKOH / g. The temperature is then lowered to below 150°C to obtain epoxy-modified alkyd resin. S3: Water-based epoxy-modified alkyd resin is obtained to produce water-dispersible alkyd resin; The reaction vessel controls the reaction temperature using a variable jacket.

5. The method for preparing a water-dispersible alkyd resin according to claim 4, characterized in that, The specific steps for water-based epoxy-modified alkyd resin are as follows: Weigh out 3-4 parts by weight of styrene, 10-12 parts by weight of methacrylic acid, 2-3 parts by weight of acrylic acid, 1-2 parts by weight of butyl acrylate and 0.3-0.6 parts by weight of benzoyl peroxide and mix them to form a mixture. Heat the epoxy-modified alkyd resin in the reactor to 120°C, add the mixture dropwise to the reactor and keep it at this temperature for 1 hour. When the solid content of the modified alkyd resin is 70% and the acid value is 45 mg KOH / g, stop the reaction, cool it down to 50°C, and add distilled water to dilute the modified alkyd resin to a solid content of 40% to obtain water-dispersible alkyd resin.

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