A bio-based polyol and its preparation method and application in waterborne polyurethane coatings

Abstract

The present invention belongs to the technical field of polyurethane coatings, and specifically relates to a bio-based polyol and a preparation method thereof and an application thereof in waterborne polyurethane coatings. A secondary alcohol is used as a first ring-opening reagent, and the secondary alcohol is subjected to a ring-opening reaction with epoxidized vegetable oil in a first microreactor of a microchannel modular reaction device under the action of a catalyst to obtain a polyol; an alcohol containing a quaternary ammonium salt is used as a second ring-opening reagent, and the alcohol containing a quaternary ammonium salt is subjected to a ring-opening reaction with the polyol to obtain a bio-based polyol. The present invention adopts a novel ring-opening reagent, and the bio-based polyol prepared has a novel structure, is moderate and evenly distributed, has a low viscosity, can replace traditional petrochemical polyols, and the waterborne polyurethane coating prepared by the bio-based polyol prepared by the present invention has significantly improved performance.

Description

Technical Field

[0001] The invention belongs to the technical field of polyurethane coatings, and specifically relates to a bio-based polyol and a preparation method thereof and application thereof in waterborne polyurethane coatings. Background Art

[0002] Polyurethane is a polymer with repeating structural units of carbamate segments made by the reaction of isocyanate and polyol. Polyurethane products are divided into two categories: foamed products and non-foamed products. Foamed products include soft, hard, and semi-hard polyurethane foam plastics; non-foamed products include coatings, adhesives, synthetic leather, elastomers, and elastic fibers. Polyurethane materials have excellent performance, a wide range of uses, and a wide variety of products, among which polyurethane coatings are the most widely used.

[0003] In recent years, with the increase of people's environmental awareness and their concern for their own health, coupled with the strict requirements of environmental regulations on the emission of volatile organic compounds (VOC) and the content of harmful solvents, the application of polyurethane coatings containing solvents and organic fillers has been greatly restricted, prompting polyurethane coatings to develop in the direction of water-based, powdered and high solid content. Among them, water-based polyurethane coatings use water as a dispersion medium and are highly valued by the coating industry because of their safety, non-toxicity, no solvent volatilization, environmental friendliness, and good water resistance. The development of water-based polyurethane coatings has become one of the hot spots in the field of polyurethane coatings in recent years.

[0004] However, the existing waterborne polyurethane coatings mostly use petroleum as raw material to prepare polyols, which consumes a large amount of petroleum resources, and the use of petroleum to prepare polyols has the problems of complex process and serious pollution. Natural oils are currently recognized and the only renewable petroleum substitute, and among natural oils, vegetable oils have the best performance. Therefore, by using vegetable oil polyols to introduce vegetable oil molecules into polyurethane materials with ring-opening reagents, it can not only solve the problems of shortage of petroleum resources and environmental pollution, but also increase the added value of vegetable oil products.

[0005] The preparation of polyurethane is mainly the polymerization process of polyols and isocyanates. The traditional polyurethane system mainly uses petrochemical polyether or polyester polyols and isocyanates as two main raw materials. Catalysts, surfactants and other additives are added to the coating to regulate the polymerization process and affect the material properties. However, when using vegetable oil polyol raw materials to develop polyurethane, the monomer itself has the properties of a surfactant, which helps in the dispersibility of water-based polyurethane coatings. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a bio-based polyol in view of the deficiencies in the prior art.

[0007] Another technical problem to be solved by the present invention is to provide a method for preparing the above-mentioned bio-based polyol.

[0008] A further technical problem to be solved by the present invention is to provide application of the above bio-based polyol in the preparation of waterborne polyurethane coatings.

[0009] Invention idea: In order to improve the mechanical properties of downstream products of polyester polyols, a simple secondary alcohol is selected as the first ring-opening reagent to carry out the ring-opening reaction of the epoxy group, and then a primary alcohol containing a quaternary ammonium salt is used to carry out the ring-opening reaction of the residual epoxy group to obtain a class of vegetable oil polyol products with an epoxy value close to 0. In order to avoid non-selective ring opening in the ring-opening reaction and produce cross-linking side reactions, the present invention adopts micro-reaction technology and selects a microchannel modular reaction device as a reaction device to further control the ring-opening group.

[0010] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0011] The present invention discloses a method for preparing a bio-based polyol, comprising the following steps:

[0012] (1) dissolving a first ring-opening reagent and a catalyst in 1,4-dioxane to obtain a first mixed solution; pumping the epoxidized vegetable oil and the first mixed solution into a first microreactor of a microchannel modular reaction device to perform a first ring-opening reaction to obtain a reaction effluent containing a polyol;

[0013] (2) dissolving a second ring-opening reagent in 1,4-dioxane to obtain a second mixed solution; and simultaneously pumping the second mixed solution and the reaction effluent containing the polyol obtained in step (1) into a second microreactor of the microchannel modular reaction device to perform a second ring-opening reaction to obtain the product.

[0014] Specifically, in step (1), the first ring-opening reagent is any one of isopropanol, 2-butanol and 2-pentanol; the catalyst is any one of fluoroboric acid, phosphoric acid, phosphotungstic acid and lipase CALB or a combination thereof, preferably fluoroboric acid; the epoxidized vegetable oil is any one of epoxidized olive oil, epoxidized peanut oil, epoxidized rapeseed oil, epoxidized cottonseed oil, epoxidized soybean oil, epoxidized coconut oil, epoxidized palm oil, epoxidized sesame oil, epoxidized corn oil and epoxidized sunflower oil or a combination thereof, preferably epoxidized soybean oil or epoxidized cottonseed oil.

[0015] Specifically, in step (1), in step (1), the mass volume ratio of the first ring-opening reagent to 1,4-dioxane is 1g:3-6mL; the mass ratio of the epoxidized vegetable oil to the catalyst is 1:0.02; and the molar ratio of the epoxy group in the epoxidized vegetable oil to the first ring-opening reagent is 1:0.7-0.9.

[0016] Specifically, in step (1), the flow rate of the epoxidized vegetable oil pumped into the first microreactor of the microchannel modular reaction device is 0.19-0.74 mL / min; the flow rate of the first mixed liquid pumped into the first microreactor of the microchannel modular reaction device is 0.23-0.92 mL / min; the volume of the first microreactor is 5-20 mL, preferably 5-15 mL; the reaction temperature of the first ring-opening reaction is 80-120° C., preferably 80-100° C.

[0017] Specifically, in step (2), the second ring-opening reagent is an alcohol containing a quaternary ammonium salt; the alcohol containing a quaternary ammonium salt is any one of choline bromide, (3-hydroxypropyl)trimethylammonium bromide, (4-hydroxybutyl)trimethylammonium bromide, (2-hydroxyethyl)pyridinium bromide and (3-hydroxypropyl)pyridinium bromide, preferably choline bromide or (2-hydroxyethyl)pyridinium bromide.

[0018] Specifically, the molar ratio of the epoxy groups in the epoxidized vegetable oil in step (1) to the second ring-opening reagent in step (2) is 1:0.3-0.5.

[0019] Specifically, in step (2), the mass volume ratio of the second ring-opening reagent to 1,4-dioxane is 1 g: 4 to 10 mL; the flow rate of the second mixed solution pumped into the second microreactor of the microchannel modular reaction device is 0.4 to 1.6 mL / min; the volume of the second microreactor is 5 to 20 mL, preferably 10 to 20 mL; the reaction temperature of the second ring-opening reaction is 80 to 120° C., preferably 90 to 110° C.

[0020] Wherein, in step (2), the flow rate of the reaction effluent containing polyol obtained in step (1) pumped into the second microreactor of the microchannel modular reaction device is: the sum of the flow rate of the epoxy vegetable oil pumped into the first microreactor of the microchannel modular reaction device and the flow rate of the first mixed liquid pumped into the first microreactor of the microchannel modular reaction device.

[0021] Specifically, the microchannel modular reaction device includes a first feed pump, a second feed pump, a third feed pump, a first micromixer, a second micromixer, a microreaction pipeline, a tubular temperature control module, a first microreactor, a second microreactor and a receiver; wherein the first feed pump and the second feed pump are connected in parallel to the first micromixer, and the first micromixer and the first microreactor are connected through a microreaction pipeline; the first microreactor and the third feed pump are connected in parallel to the second micromixer, and the second micromixer, the second microreactor and the receiver are connected in series through the microreaction pipeline.

[0022] The models of the first micromixer and the second micromixer are preferably slit plate mixer LH25; the models of the first microreactor and the second microreactor are preferably Vapotech.

[0023] The reaction temperatures of the first microreactor and the second microreactor are controlled by heating in an oil bath.

[0024] The reaction effluent of the second microreactor was concentrated to 1 / 2 volume, ethyl acetate was added, and then the concentrated reaction effluent was washed with 5wt% sodium bicarbonate solution and water in turn, layered, the organic phase was dried, filtered, and concentrated to obtain bio-based polyols.

[0025] The bio-based polyols prepared by the above preparation method are also within the protection scope of the present invention.

[0026] Furthermore, the present invention also provides the use of the above-mentioned bio-based polyol in the preparation of waterborne polyurethane coatings.

[0027] Among them, in the application of the above-mentioned bio-based polyol in the preparation of waterborne polyurethane coatings, the method for preparing waterborne polyurethane coatings can refer to patent CN202011238146.1, or the following method can be used:

[0028] (i) mixing a bio-based polyol and an isocyanate in an organic solvent, and adding a catalyst to react to obtain a prepolymer mixture;

[0029] (ii) adding epoxy resin, flame retardant and hydrophilic chain extender to the prepolymer mixed solution obtained in step (i) to carry out polymerization reaction to obtain a polymer mixed solution;

[0030] (iii) adding a neutralizing agent to the polymer mixture obtained in step (ii) until it becomes neutral, then adding water to emulsify it, and evacuating the mixture to obtain the product.

[0031] The use of the above-mentioned bio-based polyols in the preparation of waterborne polyurethane coatings is also within the protection scope of the present invention.

[0032] Beneficial effects:

[0033] (1) The bio-based polyol prepared by the novel ring-opening reagent of the present invention contains an ester structure, which is beneficial to the mechanical properties of the product. A quaternary ammonium salt and an ether bond are introduced, thereby increasing the mechanical properties of the polyurethane material. At the same time, the ring-opening reagent contains a secondary alcohol, thereby increasing the toughness of the bio-based polyol.

[0034] (2) The present invention adopts a new type of ring-opening reagent to prepare a bio-based polyol with a novel structure. The polyol is moderate and evenly distributed, has a low viscosity, and can replace traditional petrochemical polyols. The performance of the polyurethane coating prepared by the bio-based polyol prepared by the present invention is significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments, and the above and / or other advantages of the present invention will become more clear.

[0036] Figure 1 Diagram of the microchannel modular reaction device. DETAILED DESCRIPTION

[0037] The present invention can be better understood according to the following examples. However, it is easy for those skilled in the art to understand that the contents described in the examples are only used to illustrate the present invention, and should not and will not limit the present invention described in detail in the claims.

[0038] The concentration of fluoroboric acid used in the present invention is 40 wt %.

[0039] The relevant determination methods of the prepared bio-based polyol and polyurethane coating materials of the present invention are as follows:

[0040] (1) Measure the hydroxyl value according to GB / T 12008.3-2009;

[0041] (2) Measure viscosity according to GB / T 12008.7-2010;

[0042] (3) Determine the actual drying time of the coating according to GB / T 1728-1979 (1989);

[0043] (4) Determine the pencil hardness of the coating according to GB / T 6739-2006;

[0044] (5) Determine the impact resistance of the coating according to GB / T 1732-1993;

[0045] (6) The flexibility of the coating was determined according to GB / T 1731-1993.

[0046] The microchannel modular reaction device described in the following embodiments includes a first feed pump, a second feed pump, a third feed pump, a first micromixer, a second micromixer, a microreaction pipeline, a tubular temperature control module, a first microreactor, a second microreactor and a receiver; wherein the first feed pump and the second feed pump are connected in parallel to the first micromixer, and the first micromixer and the first microreactor are connected through a microreaction pipeline; the first microreactor and the third feed pump are connected in parallel to the second micromixer, and the second micromixer, the second microreactor and the receiver are connected in series through a microreaction pipeline. See the specific microchannel modular reaction device diagram. Figure 1 .

[0047] The models of the first micromixer and the second micromixer are preferably slit plate mixer LH25; the models of the first microreactor and the second microreactor are preferably Vapotech.

[0048] The reaction temperatures of the first microreactor and the second microreactor are controlled by heating in an oil bath.

[0049] Among them, the first feed pump, the second feed pump and the third feed pump are precise and low-arterial feed pumps, the first feed pump is responsible for pumping the epoxidized vegetable oil, the second feed pump is responsible for pumping the first mixed liquid, and the third feed pump is responsible for pumping the second mixed liquid.

[0050] Example 1

[0051] (1) 19.5 g of isopropanol and 2 g of fluoroboric acid solution were dissolved in 100 mL of 1,4-dioxane solution to obtain a first mixed solution. The temperature was controlled to be 90°C, and 100 g of epoxidized soybean oil (epoxy value 6.5%) and the first mixed solution were simultaneously pumped into the first microreactor of the microchannel modular reaction device for ring-opening reaction, wherein the feed rate of the epoxidized soybean oil was 0.37 mL / min, the feed rate of the first mixed solution was 0.46 mL / min, and the volume of the first microreactor was 10 mL. After the reaction was completed, a reaction effluent containing polyols was obtained.

[0052] 22.4 g of choline bromide was dissolved in 200 mL of 1,4-dioxane solution to obtain a second mixed solution. The temperature was adjusted to 100 ° C, and the reaction effluent containing polyols and the second mixed solution were pumped into the second microreactor of the microchannel modular reaction device for ring-opening reaction, wherein the inlet rate of the second mixed solution was 0.8 mL / min, and the volume of the second microreactor was 15 mL. After the reaction, the reaction effluent was concentrated to 200 mL, 200 mL of ethyl acetate was added, and it was washed with 50 mL of 5% sodium bicarbonate solution, and then washed with water twice, adding 50 mL each time, layered, dried the organic phase, filtered, and concentrated to obtain a bio-based polyol with a hydroxyl value of 152 mg KOH / g and a viscosity of 1604 mPa·s.

[0053] (2) Preparation of bio-based waterborne polyurethane coatings:

[0054] 65 parts of bio-based polyol (prepared in Example 1) and 60 parts of isophorone diisocyanate (IPDI) were mixed in 30 parts of acetone and 2 parts of dibutyltin dilaurate were added, and the mixture was reacted at 50°C for 2 hours to obtain a prepolymer mixture. 15 parts of epoxy resin I, 18 parts of flame retardant casein and 9 parts of hydrophilic chain extender dihydroxy half ester were added to the prepolymer mixture, and the mixture was reacted at 50°C for 3 hours to obtain a polymer mixture. After cooling the polymer mixture to 30°C, 25 parts of neutralizing agent triethylamine were added to neutralize it to neutrality, and 30 parts of deionized water were added to emulsify it at high speed shear to form a polyurethane emulsion. The polyurethane emulsion was distilled under reduced pressure to remove acetone to obtain a bio-based waterborne polyurethane coating. The prepared coating was applied to a metal plate for testing.

[0055] Example 2

[0056] (1) 18 g of isopropanol and 2 g of fluoroboric acid solution were dissolved in 100 mL of 1,4-dioxane solution to obtain a first mixed solution. The temperature was controlled to be 90° C. 100 g of epoxidized cottonseed oil (epoxy value 6.0%) and the first mixed solution were simultaneously pumped into the first microreactor of the microchannel modular reaction device for ring-opening reaction, wherein the feed rate of the epoxidized cottonseed oil was 0.39 mL / min, the feed rate of the first mixed solution was 0.44 mL / min, and the volume of the first microreactor was 10 mL. After the reaction was completed, a reaction effluent containing polyols was obtained.

[0057] 20.7g of choline bromide was dissolved in 200mL of 1,4-dioxane solution to obtain a second mixed solution. The temperature was adjusted to 100°C, and the reaction effluent containing polyols and the second mixed solution were pumped into the second microreactor of the microchannel modular reaction device for ring-opening reaction, wherein the inlet rate of the second mixed solution was 0.8mL / min, and the volume of the second microreactor was 15mL. After the reaction, the reaction effluent was concentrated to 200mL, 200mL of ethyl acetate was added, and it was washed with 50mL of 5% sodium bicarbonate solution, and then washed with water twice, adding 50mL each time, layered, dried the organic phase, filtered, and concentrated to obtain a bio-based polyol with a hydroxyl value of 142mg KOH / g and a viscosity of 1382mPa·s.

[0058] (2) Preparation of bio-based waterborne polyurethane coatings:

[0059] 65 parts of bio-based polyol (prepared in Example 2) and 60 parts of isophorone diisocyanate (IPDI) were mixed in 30 parts of acetone and 2 parts of dibutyltin dilaurate were added, and the mixture was reacted at 50°C for 2 hours to obtain a prepolymer mixture. 15 parts of epoxy resin I, 18 parts of flame retardant casein and 9 parts of hydrophilic chain extender dihydroxy half ester were added to the prepolymer mixture, and the mixture was reacted at 50°C for 3 hours to obtain a polymer mixture. After cooling the polymer mixture to 30°C, 25 parts of neutralizing agent triethylamine were added to neutralize it to neutrality, and 30 parts of deionized water were added to high-speed shear emulsification to form a polyurethane emulsion. The polyurethane emulsion was distilled under reduced pressure to remove acetone to obtain a bio-based waterborne polyurethane coating. The prepared coating was applied to a metal plate for testing.

[0060] Example 3

[0061] (1) 21.1 g of 2-butanol and 2 g of fluoroboric acid solution were dissolved in 100 mL of 1,4-dioxane solution to obtain a first mixed solution. The temperature was controlled to be 90° C. 100 g of epoxidized soybean oil (epoxy value 6.5%) and the first mixed solution were simultaneously pumped into the first microreactor of the microchannel modular reaction device for ring-opening reaction, wherein the feed rate of the epoxidized soybean oil was 0.36 mL / min, the feed rate of the first mixed solution was 0.47 mL / min, and the volume of the first microreactor was 10 mL. After the reaction was completed, a reaction effluent containing polyols was obtained.

[0062] Dissolve 29.9g of choline bromide in 200mL of 1,4-dioxane solution to obtain a second mixed solution. Adjust the temperature to 100°C, and pump the obtained reaction effluent containing polyols and the second mixed solution into the second microreactor of the microchannel modular reaction device for ring-opening reaction, wherein the inlet rate of the second mixed solution is 0.8mL / min, and the volume of the second microreactor is 15mL. After the reaction, concentrate the reaction effluent to 200mL, add 200mL of ethyl acetate, wash with 50mL of 5% sodium bicarbonate solution, and then wash with water twice, adding 50mL each time, separate the layers, dry the organic phase, filter, and concentrate to obtain a bio-based polyol with a hydroxyl value of 140mg KOH / g and a viscosity of 1338mPa·s.

[0063] (2) Preparation of bio-based waterborne polyurethane coatings:

[0064] 65 parts of vegetable oil polyol (prepared in Example 3) and 60 parts of isophorone diisocyanate (IPDI) were mixed in 30 parts of acetone and 2 parts of dibutyltin dilaurate were added, and the mixture was reacted at 50°C for 2 hours to obtain a prepolymer mixture. 15 parts of epoxy resin I, 18 parts of flame retardant casein and 9 parts of hydrophilic chain extender dihydroxy half ester were added to the prepolymer mixture, and the mixture was reacted at 50°C for 3 hours to obtain a polymer mixture. After cooling the polymer mixture to 30°C, 25 parts of neutralizing agent triethylamine were added to neutralize it to neutrality, and 30 parts of deionized water were added to high-speed shear emulsification to form a polyurethane emulsion. The polyurethane emulsion was distilled under reduced pressure to remove acetone to obtain a bio-based waterborne polyurethane coating. The prepared coating was applied to a metal plate for testing.

[0065] Example 4

[0066] (1) 20.8 g of 2-butanol and 2 g of fluoroboric acid solution were dissolved in 100 mL of 1,4-dioxane solution to obtain a first mixed solution. The temperature was controlled to be 90° C. 100 g of epoxidized cottonseed oil (epoxy value 6.0%) and the first mixed solution were simultaneously pumped into the first microreactor of the microchannel modular reaction device for ring-opening reaction, wherein the feed rate of the epoxidized cottonseed oil was 0.39 mL / min, the feed rate of the first mixed solution was 0.44 mL / min, and the volume of the first microreactor was 10 mL. After the reaction was completed, a reaction effluent containing polyols was obtained.

[0067] 27.6g of choline bromide was dissolved in 200mL of 1,4-dioxane solution to obtain a second mixed solution. The temperature was adjusted to 100°C, and the reaction effluent containing polyols and the second mixed solution were pumped into the second microreactor of the microchannel reaction device for ring-opening reaction, wherein the inlet rate of the second mixed solution was 0.8mL / min, and the volume of the second microreactor was 15mL. After the reaction, the reaction effluent was concentrated to 200mL, 200mL of ethyl acetate was added, and it was washed with 50mL of 5% sodium bicarbonate solution, and then washed with water twice, adding 50mL each time, layered, dried the organic phase, filtered, and concentrated to obtain a bio-based polyol with a hydroxyl value of 136mg KOH / g and a viscosity of 1248mPa·s.

[0068] (2) Preparation of bio-based waterborne polyurethane coatings:

[0069] 65 parts of vegetable oil polyol (prepared in Example 4) and 60 parts of isophorone diisocyanate (IPDI) were mixed in 30 parts of acetone and 2 parts of dibutyltin dilaurate were added, and the mixture was reacted at 50°C for 2 hours to obtain a prepolymer mixture. 15 parts of epoxy resin I, 18 parts of flame retardant casein and 9 parts of hydrophilic chain extender dihydroxy half ester were added to the prepolymer mixture, and the mixture was reacted at 50°C for 3 hours to obtain a polymer mixture. After cooling the polymer mixture to 30°C, 25 parts of neutralizing agent triethylamine were added to neutralize it to neutrality, and 30 parts of deionized water were added to high-speed shear emulsification to form a polyurethane emulsion. The polyurethane emulsion was decompressed and distilled to remove acetone to obtain a bio-based waterborne polyurethane coating. The prepared coating was applied to a metal plate for testing.

[0070] Example 5

[0071] (1) 30.4 g of 2-pentanol and 2 g of fluoroboric acid solution were dissolved in 100 mL of 1,4-dioxane solution to obtain a first mixed solution. The temperature was controlled to be 90° C. 100 g of epoxidized soybean oil (epoxy value 6.5%) and the first mixed solution were simultaneously pumped into the first microreactor of the microchannel modular reaction device for ring-opening reaction, wherein the feed rate of the epoxidized soybean oil was 0.35 mL / min, the feed rate of the first mixed solution was 0.48 mL / min, and the volume of the first microreactor was 10 mL. After the reaction was completed, a reaction effluent containing polyols was obtained.

[0072] 26.2g of choline bromide was dissolved in 200mL of 1,4-dioxane solution to obtain a second mixed solution. The temperature was adjusted to 100°C, and the reaction effluent containing polyols and the second mixed solution were pumped into the second microreactor of the microchannel modular reaction device for ring-opening reaction, wherein the inlet rate of the second mixed solution was 0.8mL / min, and the volume of the second microreactor was 15mL. After the reaction, the reaction effluent was concentrated to 200mL, 200mL of ethyl acetate was added, and it was washed with 50mL of 5% sodium bicarbonate solution, and then washed with water twice, adding 50mL each time, layered, dried the organic phase, filtered, and concentrated to obtain a bio-based polyol with a hydroxyl value of 144mg KOH / g and a viscosity of 1404mPa·s.

[0073] (2) Preparation of bio-based waterborne polyurethane coatings:

[0074] 65 parts of vegetable oil polyol (prepared in Example 5) and 60 parts of isophorone diisocyanate (IPDI) were mixed in 30 parts of acetone and 2 parts of dibutyltin dilaurate were added, and the mixture was reacted at 50°C for 2 hours to obtain a prepolymer mixture. 15 parts of epoxy resin I, 18 parts of flame retardant casein and 9 parts of hydrophilic chain extender dihydroxy half ester were added to the prepolymer mixture, and the mixture was reacted at 50°C for 3 hours to obtain a polymer mixture. After cooling the polymer mixture to 30°C, 25 parts of neutralizing agent triethylamine were added to neutralize it to neutrality, and 30 parts of deionized water were added to high-speed shear emulsification to form a polyurethane emulsion. The polyurethane emulsion was decompressed and distilled to remove acetone to obtain a bio-based waterborne polyurethane coating. The prepared coating was applied to a metal plate for testing.

[0075] Example 6

[0076] (1) 29.7 g of 2-pentanol and 2 g of fluoroboric acid solution were dissolved in 100 mL of 1,4-dioxane solution to obtain a first mixed solution. The temperature was controlled to be 90° C. 100 g of epoxidized cottonseed oil (epoxy value 6.0%) and the first mixed solution were simultaneously pumped into the first microreactor of the microchannel modular reaction device for ring-opening reaction, wherein the feed rate of the epoxidized cottonseed oil was 0.37 mL / min, the feed rate of the first mixed solution was 0.46 mL / min, and the volume of the first microreactor was 10 mL. After the reaction was completed, a reaction effluent containing polyols was obtained.

[0077] 20.7g of choline bromide was dissolved in 200mL of 1,4-dioxane solution to obtain a second mixed solution. The temperature was adjusted to 100°C, and the reaction effluent containing polyols and the second mixed solution were pumped into the second microreactor of the microchannel modular reaction device for ring-opening reaction, wherein the inlet rate of the second mixed solution was 0.8mL / min, and the volume of the second microreactor was 15mL. After the reaction, the reaction effluent was concentrated to 200mL, 200mL of ethyl acetate was added, and it was washed with 50mL of 5% sodium bicarbonate solution, and then washed with water twice, adding 50mL each time, layered, dried the organic phase, filtered, and concentrated to obtain a bio-based polyol with a hydroxyl value of 138mg KOH / g and a viscosity of 1298mPa·s.

[0078] (2) Preparation of bio-based waterborne polyurethane coatings:

[0079] 65 parts of vegetable oil polyol (prepared in Example 6) and 60 parts of isophorone diisocyanate (IPDI) were mixed in 30 parts of acetone and 2 parts of dibutyltin dilaurate were added, and the mixture was reacted at 50°C for 2 hours to obtain a prepolymer mixture. 15 parts of epoxy resin I, 18 parts of flame retardant casein and 9 parts of hydrophilic chain extender dihydroxy half ester were added to the prepolymer mixture, and the mixture was reacted at 50°C for 3 hours to obtain a polymer mixture. After cooling the polymer mixture to 30°C, 25 parts of neutralizing agent triethylamine were added to neutralize it to neutrality, and 30 parts of deionized water were added to high-speed shear emulsification to form a polyurethane emulsion. The polyurethane emulsion was distilled under reduced pressure to remove acetone to obtain a bio-based waterborne polyurethane coating. The prepared coating was applied to a metal plate for testing.

[0080] Example 7

[0081] (1) 18.3 g of isopropanol and 2 g of fluoroboric acid solution were dissolved in 100 mL of 1,4-dioxane solution to obtain a first mixed solution. The temperature was controlled to be 90°C, and 100 g of epoxidized soybean oil (epoxy value 6.5%) and the first mixed solution were simultaneously pumped into the first microreactor of the microchannel modular reaction device for ring-opening reaction, wherein the feed rate of the epoxidized soybean oil was 0.37 mL / min, the feed rate of the first mixed solution was 0.46 mL / min, and the volume of the first microreactor was 10 mL. After the reaction was completed, a reaction effluent containing polyols was obtained.

[0082] 41.4 g (2-hydroxyethyl) pyridinium bromide was dissolved in 200 mL of 1,4-dioxane solution to obtain a second mixed solution. The temperature was adjusted to 100 ° C, and the reaction effluent containing polyols and the second mixed solution were pumped into the second microreactor of the microchannel modular reaction device for ring-opening reaction, wherein the inlet rate of the second mixed solution was 0.8 mL / min, and the volume of the second microreactor was 15 mL. After the reaction, the reaction effluent was concentrated to 200 mL, 200 mL of ethyl acetate was added, and it was washed with 50 mL of 5% sodium bicarbonate solution, and then washed with water twice, adding 50 mL each time, layered, dried the organic phase, filtered, and concentrated to obtain a bio-based polyol with a hydroxyl value of 131 mg KOH / g and a viscosity of 1161 mPa·s.

[0083] (2) Preparation of bio-based waterborne polyurethane coatings:

[0084] 65 parts of vegetable oil polyol (prepared in Example 7) and 60 parts of isophorone diisocyanate (IPDI) were mixed in 30 parts of acetone and 3 parts of dibutyltin dilaurate were added, and the mixture was reacted at 50°C for 2 hours to obtain a prepolymer mixture. 15 parts of epoxy resin I, 18 parts of flame retardant casein and 9 parts of hydrophilic chain extender dihydroxy half ester were added to the prepolymer mixture, and the mixture was reacted at 50°C for 3 hours to obtain a polymer mixture. After cooling the polymer mixture to 30°C, 25 parts of neutralizing agent triethylamine were added to neutralize it to neutrality, and 30 parts of deionized water were added to high-speed shear emulsification to form a polyurethane emulsion. The polyurethane emulsion was decompressed and distilled to remove acetone to obtain a bio-based waterborne polyurethane coating. The prepared coating was applied to a metal plate for testing.

[0085] Example 8

[0086] (1) 19.5 g of isopropanol and 2 g of fluoroboric acid solution were dissolved in 100 mL of 1,4-dioxane solution to obtain a first mixed solution. The temperature was controlled to be 90°C, and 100 g of epoxidized soybean oil (epoxy value 6.5%) and the first mixed solution were simultaneously pumped into the first microreactor of the microchannel modular reaction device for ring-opening reaction, wherein the feed rate of the epoxidized soybean oil was 0.37 mL / min, the feed rate of the first mixed solution was 0.46 mL / min, and the volume of the first microreactor was 10 mL. After the reaction was completed, a reaction effluent containing polyols was obtained.

[0087] 24.9g (2-hydroxyethyl) pyridinium bromide was dissolved in 200mL of 1,4-dioxane solution to obtain a second mixed solution. The temperature was adjusted to 100°C, and the reaction effluent containing polyols and the second mixed solution were pumped into the second microreactor of the microchannel modular reaction device for ring-opening reaction, wherein the inlet rate of the second mixed solution was 0.8mL / min, and the volume of the second microreactor was 15mL. After the reaction, the reaction effluent was concentrated to 200mL, 200mL of ethyl acetate was added, and it was washed with 50mL of 5% sodium bicarbonate solution, and then washed with water twice, adding 50mL each time, layered, dried the organic phase, filtered, and concentrated to obtain a bio-based polyol with a hydroxyl value of 135mg KOH / g and a viscosity of 1308mPa·s.

[0088] (2) Preparation of bio-based waterborne polyurethane coatings:

[0089] 65 parts of vegetable oil polyol (prepared in Example 8) and 60 parts of isophorone diisocyanate (IPDI) were mixed in 30 parts of acetone and 2 parts of dibutyltin dilaurate were added, and the mixture was reacted at 50°C for 2 hours to obtain a prepolymer mixture. 15 parts of epoxy resin I, 18 parts of flame retardant casein and 9 parts of hydrophilic chain extender dihydroxy half ester were added to the prepolymer mixture, and the mixture was reacted at 50°C for 3 hours to obtain a polymer mixture. After cooling the polymer mixture to 30°C, 25 parts of neutralizing agent triethylamine were added to neutralize it to neutrality, and 30 parts of deionized water were added to emulsify it at high speed shear to form a polyurethane emulsion. The polyurethane emulsion was decompressed and distilled to remove acetone to obtain a bio-based waterborne polyurethane coating. The prepared coating was applied to a metal plate for testing.

[0090] Example 9

[0091] (1) 19.5 g of isopropanol and 2 g of fluoroboric acid solution were dissolved in 100 mL of 1,4-dioxane solution to obtain a first mixed solution. The temperature was controlled to be 80°C, and 100 g of epoxidized soybean oil (epoxy value 6.5%) and the first mixed solution were simultaneously pumped into the first microreactor of the microchannel modular reaction device for ring-opening reaction, wherein the feed rate of the epoxidized soybean oil was 0.37 mL / min, the feed rate of the first mixed solution was 0.46 mL / min, and the volume of the first microreactor was 10 mL. After the reaction was completed, a reaction effluent containing polyols was obtained.

[0092] 22.4 g of choline bromide was dissolved in 200 mL of 1,4-dioxane solution to obtain a second mixed solution. The temperature was adjusted to 90 ° C, and the reaction effluent containing polyols and the second mixed solution were pumped into the second microreactor of the microchannel modular reaction device for ring-opening reaction, wherein the inlet rate of the second mixed solution was 0.8 mL / min, and the volume of the second microreactor was 15 mL. After the reaction, the reaction effluent was concentrated to 200 mL, 200 mL of ethyl acetate was added, and it was washed with 50 mL of 5% sodium bicarbonate solution, and then washed with water twice, adding 50 mL each time, layered, dried the organic phase, filtered, and concentrated to obtain a bio-based polyol with a hydroxyl value of 147 mg KOH / g and a viscosity of 1488 mPa·s.

[0093] (2) Preparation of bio-based waterborne polyurethane coatings:

[0094] 65 parts of bio-based polyol (prepared in Example 9) and 60 parts of isophorone diisocyanate (IPDI) were mixed in 30 parts of acetone and 2 parts of dibutyltin dilaurate were added, and the mixture was reacted at 50°C for 2 hours to obtain a prepolymer mixture. 15 parts of epoxy resin I, 18 parts of flame retardant casein and 9 parts of hydrophilic chain extender dihydroxy half ester were added to the prepolymer mixture, and the mixture was reacted at 50°C for 3 hours to obtain a polymer mixture. After cooling the polymer mixture to 30°C, 25 parts of neutralizing agent triethylamine were added to neutralize it to neutrality, and 30 parts of deionized water were added to high-speed shear emulsification to form a polyurethane emulsion. The polyurethane emulsion was distilled under reduced pressure to remove acetone to obtain a bio-based waterborne polyurethane coating. The prepared coating was applied to a metal plate for testing.

[0095] Example 10

[0096] (1) 19.5 g of isopropanol and 2 g of fluoroboric acid solution were dissolved in 100 mL of 1,4-dioxane solution to obtain a first mixed solution. The temperature was controlled to be 100° C. 100 g of epoxidized soybean oil (epoxy value 6.5%) and the first mixed solution were simultaneously pumped into the first microreactor of the microchannel modular reaction device for ring-opening reaction, wherein the feed rate of the epoxidized soybean oil was 0.37 mL / min, the feed rate of the first mixed solution was 0.46 mL / min, and the volume of the first microreactor was 10 mL. After the reaction was completed, a reaction effluent containing polyols was obtained.

[0097] 22.4 g of choline bromide was dissolved in 200 mL of 1,4-dioxane solution to obtain a second mixed solution. The temperature was adjusted to 110 ° C, and the reaction effluent containing polyols and the second mixed solution were pumped into the second microreactor of the microchannel modular reaction device for ring-opening reaction, wherein the inlet rate of the second mixed solution was 0.8 mL / min, and the volume of the second microreactor was 15 mL. After the reaction, the reaction effluent was concentrated to 200 mL, 200 mL of ethyl acetate was added, and it was washed with 50 mL of 5% sodium bicarbonate solution, and then washed with water twice, adding 50 mL each time, layered, dried the organic phase, filtered, and concentrated to obtain a bio-based polyol with a hydroxyl value of 142 mg KOH / g and a viscosity of 1392 mPa·s.

[0098] (2) Preparation of bio-based waterborne polyurethane coatings:

[0099] 65 parts of bio-based polyol (prepared in Example 10) and 60 parts of isophorone diisocyanate (IPDI) were mixed in 30 parts of acetone and 2 parts of dibutyltin dilaurate were added, and the mixture was reacted at 50°C for 2 hours to obtain a prepolymer mixture. 15 parts of epoxy resin I, 18 parts of flame retardant casein and 9 parts of hydrophilic chain extender dihydroxy half ester were added to the prepolymer mixture, and the mixture was reacted at 50°C for 3 hours to obtain a polymer mixture. After cooling the polymer mixture to 30°C, 25 parts of neutralizing agent triethylamine were added to neutralize it to neutrality, and 30 parts of deionized water were added to high-speed shear emulsification to form a polyurethane emulsion. The polyurethane emulsion was distilled under reduced pressure to remove acetone to obtain a bio-based waterborne polyurethane coating. The prepared coating was applied to a metal plate for testing.

[0100] Embodiment 11

[0101] (1) 19.5 g of isopropanol and 2 g of fluoroboric acid solution were dissolved in 100 mL of 1,4-dioxane solution to obtain a first mixed solution. The temperature was controlled to be 90°C, and 100 g of epoxidized soybean oil (epoxy value was 6.5%) and the first mixed solution were simultaneously pumped into the first microreactor of the microchannel modular reaction device for ring-opening reaction, wherein the feed rate of the epoxidized soybean oil was 0.74 mL / min, the feed rate of the first mixed solution was 0.92 mL / min, and the volume of the first microreactor was 15 mL. After the reaction was completed, a reaction effluent containing polyols was obtained.

[0102] 22.4 g of choline bromide was dissolved in 200 mL of 1,4-dioxane solution to obtain a second mixed solution. The temperature was adjusted to 100 ° C, and the reaction effluent containing polyols and the second mixed solution were pumped into the second microreactor of the microchannel modular reaction device for ring-opening reaction, wherein the inlet rate of the second mixed solution was 1.6 mL / min, and the volume of the second microreactor was 20 mL. After the reaction, the reaction effluent was concentrated to 200 mL, 200 mL of ethyl acetate was added, and it was washed with 50 mL of 5% sodium bicarbonate solution, and then washed with water twice, adding 50 mL each time, layered, dried the organic phase, filtered, and concentrated to obtain a bio-based polyol with a hydroxyl value of 140 mg KOH / g, a viscosity of 1384 mPa·s, and an epoxy value of 0.1.

[0103] (2) Preparation of bio-based waterborne polyurethane coatings:

[0104] 65 parts of bio-based polyol (prepared in Example 11) and 60 parts of isophorone diisocyanate (IPDI) were mixed in 30 parts of acetone and 2 parts of dibutyltin dilaurate were added, and the mixture was reacted at 50°C for 2 hours to obtain a prepolymer mixture. 15 parts of epoxy resin I, 18 parts of flame retardant casein and 9 parts of hydrophilic chain extender dihydroxy half ester were added to the prepolymer mixture, and the mixture was reacted at 50°C for 3 hours to obtain a polymer mixture. After cooling the polymer mixture to 30°C, 25 parts of neutralizing agent triethylamine were added to neutralize it to neutrality, and 30 parts of deionized water were added to high-speed shear emulsification to form a polyurethane emulsion. The polyurethane emulsion was distilled under reduced pressure to remove acetone to obtain a bio-based waterborne polyurethane coating. The prepared coating was applied to a metal plate for testing.

[0105] Example 12

[0106] (1) 19.5 g of isopropanol and 2 g of fluoroboric acid solution were dissolved in 100 mL of 1,4-dioxane solution to obtain a first mixed solution. The temperature was controlled to be 90°C, and 100 g of epoxidized soybean oil (epoxy value 6.5%) and the first mixed solution were simultaneously pumped into the first microreactor of the microchannel modular reaction device for ring-opening reaction, wherein the feed rate of the epoxidized soybean oil was 0.19 mL / min, the feed rate of the first mixed solution was 0.23 mL / min, and the volume of the first microreactor was 5 mL. After the reaction was completed, a reaction effluent containing polyols was obtained.

[0107] 22.4 g of choline bromide was dissolved in 200 mL of 1,4-dioxane solution to obtain a second mixed solution. The temperature was adjusted to 100 ° C, and the reaction effluent containing polyols and the second mixed solution were pumped into the second microreactor of the microchannel modular reaction device for ring-opening reaction, wherein the inlet rate of the second mixed solution was 0.4 mL / min, and the volume of the second microreactor was 10 mL. After the reaction, the reaction effluent was concentrated to 200 mL, 200 mL of ethyl acetate was added, and it was washed with 50 mL of 5% sodium bicarbonate solution, and then washed with water twice, adding 50 mL each time, layered, dried the organic phase, filtered, and concentrated to obtain a bio-based polyol with a hydroxyl value of 144 mg KOH / g and a viscosity of 1443 mPa·s.

[0108] (2) Preparation of bio-based waterborne polyurethane coatings:

[0109] 65 parts of bio-based polyol (prepared in Example 12) and 60 parts of isophorone diisocyanate (IPDI) were mixed in 30 parts of acetone and 2 parts of dibutyltin dilaurate were added, and the mixture was reacted at 50°C for 2 hours to obtain a prepolymer mixture. 15 parts of epoxy resin I, 18 parts of flame retardant casein and 9 parts of hydrophilic chain extender dihydroxy half ester were added to the prepolymer mixture, and the mixture was reacted at 50°C for 3 hours to obtain a polymer mixture. After cooling the polymer mixture to 30°C, 25 parts of neutralizing agent triethylamine were added to neutralize it to neutrality, and 30 parts of deionized water were added to high-speed shear emulsification to form a polyurethane emulsion. The polyurethane emulsion was distilled under reduced pressure to remove acetone to obtain a bio-based waterborne polyurethane coating. The prepared coating was applied to a metal plate for testing.

[0110] Comparative Example 1

[0111] The preparation method of bio-based polyol is the same as that of Example 1, except that the reaction device is a conventional reaction bottle.

[0112] (1) 19.5 g of isopropanol and 2 g of fluoroboric acid solution were dissolved in 100 mL of 1,4-dioxane solution to obtain a first mixed solution. 100 g of epoxidized soybean oil (epoxy value 6.5%) and the first mixed solution were added to a reaction bottle for ring-opening reaction, the temperature of the reaction bottle was adjusted to 120°C, and the reaction was carried out for 5 h. Subsequently, 22.4 g of choline bromide dissolved in 200 mL of 1,4-dioxane solution was added to the reaction system for ring-opening reaction, the temperature was adjusted to 120°C, and the reaction time was 3 h. After the reaction was completed, the reaction effluent was concentrated to 200 mL, 200 mL of ethyl acetate was added, and it was washed with 50 mL of 5% sodium bicarbonate solution, and then washed with water twice, adding 50 mL each time, layering, drying the organic phase, suction filtering, and concentrating to obtain a bio-based polyol with a hydroxyl value of 108 mg KOH / g and a viscosity of 2018 mPa·s.

[0113] (2) Preparation of bio-based waterborne polyurethane coatings:

[0114] 65 parts of vegetable oil polyol (prepared in comparative example 1) and 60 parts of isophorone diisocyanate (IPDI) were mixed in 30 parts of acetone and 2 parts of dibutyltin dilaurate were added, and the mixture was reacted at 50°C for 2 hours to obtain a prepolymer mixture. 15 parts of epoxy resin I, 18 parts of flame retardant casein and 9 parts of hydrophilic chain extender dihydroxy half ester were added to the prepolymer mixture, and the mixture was reacted at 50°C for 3 hours to obtain a polymer mixture. After cooling the polymer mixture to 30°C, 25 parts of neutralizing agent triethylamine were added to neutralize it to neutrality, and 30 parts of deionized water were added to emulsify it at high speed shear to form a polyurethane emulsion. The polyurethane emulsion was decompressed and distilled to remove acetone to obtain a bio-based waterborne polyurethane coating. The prepared coating was applied to a metal plate for testing.

[0115] Comparative Example 2

[0116] The preparation method of bio-based polyol is the same as that of Example 2, except that the reaction device is a conventional reaction bottle.

[0117] (1) 18 g of isopropanol and 2 g of fluoroboric acid solution were dissolved in 100 mL of 1,4-dioxane solution to obtain a first mixed solution. 100 g of epoxidized cottonseed oil (epoxy value of 6.0%) and the first mixed solution were added to a reaction bottle for ring-opening reaction, and the temperature of the reaction bottle was adjusted to 120°C for 5 h. 20.7 g of choline bromide was added to 200 mL of 1,4-dioxane solution for ring-opening reaction, and the temperature was adjusted to 120°C for 3 h. The reaction effluent was concentrated to 200 mL, 200 mL of ethyl acetate was added, and it was washed with 50 mL of 5% sodium bicarbonate solution, and then washed with water twice, adding 50 mL each time, layering, drying the organic phase, filtering, and concentrating to obtain a bio-based polyol with a hydroxyl value of 98 mgKOH / g and a viscosity of 2189 mPa·s.

[0118] (2) Preparation of vegetable oil-based polyurethane coatings:

[0119] 65 parts of vegetable oil polyol (prepared in comparative example 2) and 60 parts of isophorone diisocyanate (IPDI) were mixed in 30 parts of acetone and 2 parts of dibutyltin dilaurate were added, and the mixture was reacted at 50°C for 2 hours to obtain a prepolymer mixture. 15 parts of epoxy resin I, 18 parts of flame retardant casein and 9 parts of hydrophilic chain extender dihydroxy half ester were added to the prepolymer mixture, and the mixture was reacted at 50°C for 3 hours to obtain a polymer mixture. After cooling the polymer mixture to 30°C, 25 parts of neutralizing agent triethylamine were added to neutralize it to neutrality, and 30 parts of deionized water were added to emulsify it at high speed shear to form a polyurethane emulsion. The polyurethane emulsion was decompressed and distilled to remove acetone to obtain a bio-based waterborne polyurethane coating. The prepared coating was applied to a metal plate for testing.

[0120] The performance indicators of the bio-based polyols prepared in Examples 1 to 12 and Comparative Examples 1 to 2 are shown in Table 1, and the performance indicators of the bio-based waterborne polyurethane coatings prepared are shown in Table 2.

[0121] Table 1 Performance indicators of bio-based polyols prepared in Examples 1 to 12 and Comparative Examples 1 to 2

[0122]

[0123]

[0124] Table 2 Performance indicators of bio-based polyurethane coatings prepared in Examples 1 to 12 and Comparative Examples 1 to 2

[0125] Test items Drying time (h) Pencil hardness Impact resistance (50cm) Flexibility(mm) Example 1 4 2H pass 1 Example 2 4 2H pass 1 Example 3 4 2H pass 1 Example 4 4 H pass 1 Example 5 4 2H pass 1 Example 6 4 H pass 1 Example 7 4 H pass 1 Example 8 4 H pass 1 Example 9 4 2H pass 1 Example 10 4 H pass 1 Embodiment 11 4 H pass 1 Example 12 4 H pass 1 Comparative Example 1 6 HB Not passed 2 Comparative Example 2 6.5 B Not passed 3

[0126] From the data in the table, we know that the bio-based polyols prepared in conventional reaction bottles have low hydroxyl values, severe attenuation, and more cross-linking side reactions, which lead to larger molecular weights. The viscosity of the bio-based polyols is high, and the reaction in the reaction bottle is uncontrollable.

[0127] The present invention provides a bio-based polyol and a preparation method thereof and a method for using the bio-based polyol in a waterborne polyurethane coating. There are many methods and approaches to implement the technical solution. The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be considered as the scope of protection of the present invention. All components not specified in this embodiment can be implemented by existing technologies.

Claims

1. A method for preparing a bio-based polyol, characterized in that: The following steps are involved: (1) dissolving a first ring-opening reagent and a catalyst in 1,4-dioxane to obtain a first mixed solution; and simultaneously pumping the epoxidized vegetable oil and the first mixed solution into a first microreactor of a microchannel modular reaction device to perform a first ring-opening reaction to obtain a reaction effluent containing a polyol; (2) dissolving a second ring-opening reagent in 1,4-dioxane to obtain a second mixed solution; and simultaneously pumping the second mixed solution and the reaction effluent containing the polyol obtained in step (1) into a second microreactor of the microchannel modular reaction device to perform a second ring-opening reaction, thereby obtaining; The first ring-opening reagent is any one of isopropanol, 2-butanol and 2-pentanol; the catalyst is any one of fluoroboric acid, phosphoric acid, phosphotungstic acid and lipase CALB or a combination of several thereof; The second ring-opening reagent is an alcohol containing a quaternary ammonium salt; the alcohol containing a quaternary ammonium salt is any one of choline bromide, (3-hydroxypropyl)trimethylammonium bromide, (4-hydroxybutyl)trimethylammonium bromide, (2-hydroxyethyl)pyridinium bromide and (3-hydroxypropyl)pyridinium bromide.

2. The preparation method according to claim 1, characterized in that: In step (1), the epoxidized vegetable oil is any one of epoxidized olive oil, epoxidized peanut oil, epoxidized rapeseed oil, epoxidized cottonseed oil, epoxidized soybean oil, epoxidized coconut oil, epoxidized palm oil, epoxidized sesame oil, epoxidized corn oil and epoxidized sunflower oil, or a combination of several of them.

3. The preparation method according to claim 1, characterized in that: In step (1), the mass volume ratio of the first ring-opening reagent to 1,4-dioxane is 1 g: 3-6 mL; the mass ratio of the epoxidized vegetable oil to the catalyst is 1: 0.02; and the molar ratio of the epoxy group in the epoxidized vegetable oil to the first ring-opening reagent is 1: 0.7-0.

9.

4. The preparation method according to claim 1, characterized in that: In step (1), the flow rate of the epoxidized vegetable oil pumped into the first microreactor of the microchannel modular reaction device is 0.19-0.74 mL / min; the flow rate of the first mixed liquid pumped into the first microreactor of the microchannel modular reaction device is 0.23-0.92 mL / min; the volume of the first microreactor is 5-20 mL; and the reaction temperature of the first ring-opening reaction is 80-120°C.

5. The preparation method according to claim 1, characterized in that: The molar ratio of the epoxy group in the epoxidized vegetable oil in step (1) to the second ring-opening reagent in step (2) is 1:0.3-0.

5.

6. The preparation method according to claim 1, characterized in that: In step (2), the mass volume ratio of the second ring-opening reagent to 1,4-dioxane is 1 g:4-10 mL; the flow rate of the second mixed solution pumped into the second microreactor of the microchannel modular reaction device is 0.4-1.6 mL / min; the volume of the second microreactor is 5-20 mL; and the reaction temperature of the second ring-opening reaction is 80-120°C.

7. The preparation method according to claim 1, characterized in that: The microchannel modular reaction device comprises a first feed pump, a second feed pump, a third feed pump, a first micromixer, a second micromixer, a microreaction pipeline, a tubular temperature control module, a first microreactor, a second microreactor and a receiver; wherein the first feed pump and the second feed pump are connected in parallel to the first micromixer, and the first micromixer and the first microreactor are connected through the microreaction pipeline; the first microreactor and the third feed pump are connected in parallel to the second micromixer, and the second micromixer, the second microreactor and the receiver are connected in series through the microreaction pipeline.

8. The bio-based polyol prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the bio-based polyol according to claim 8 in the preparation of waterborne polyurethane coatings.

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