Preparation method of vegetable oil polyol and application of vegetable oil polyol in polyurethane anti-corrosive coating

Abstract

Disclosed is a preparation method using a microreactor, of a vegetable oil polyol comprising mixing an epoxy vegetable oil, such as epoxy soybean oil, and an acid catalyst, such as fluoboric acid, int

Description

The present invention belongs to the field of chemical synthesis, and particularly relates to a preparation method of a vegetable oil polyol and an application of the vegetable oil polyol in a polyurethane anti-corrosive coating. BACKGROUND Polyurethane is a polymer with repeating structural units of carbamate chain segment, which is prepared by a reaction of a polyol and isocyanate. Polyurethane products are divided into foaming products and non-foaming products. The foaming products comprise soft, hard and semi-hard polyurethane foam plastics; and the non-foaming products comprise coatings, adhesives, synthetic leather, elastomers, elastic fibers, and the like. The isocyanate, one of two monomers in synthesis of the polyurethane has relatively few product types, mainly comprising MDI, TDI, and the like; and the polyol, the other monomer, has wide varieties, different qualities and diversified downstream applications, thus having a room for further research. Long-chain groups in a vegetable oil structure replace repeating units of traditional petrochemical polyol polyether or polyester, and a basic mother nucleus of triglyceride in the structure has a star-shaped spatial conformation, which gives downstream polyurethane more functional properties and application space. However, a vegetable oil polyol often has performance defects, the main reason is an uncontrollable reaction process, and many epoxy groups and ester groups often participate in multiple side reaction processes in a functional group transformation process, leading to a difficulty in constructing a designed molecular structure by a traditional chemical method, which greatly limits the quality of polyol, and often requires mixed use with the traditional petrochemical polyol to achieve a certain application effect. According to analysis of reaction mechanism, the main reason is that oil ester is often poorly miscible with a reaction reagent, but the reaction activity is low, leading to a long-term high-intensity reaction. However, due to an influence of multiple functional groups in the structure, it is difficult to balance a reaction selectivity and a transformation rate, and the process is poorly controlled, resulting in poor molecular uniformity, high viscosity, and a great difference between a macro indicator and a micro indicator of a single molecule. Therefore, even though the price of vegetable oil is often lower than that of a monomer of petrochemical repeating unit, it is difficult to obtain a vegetable oil polyol product with advantages in cost and quality, and it is necessary to control the product quality through chemical process control. SUMMARY The technical problem to be solved by the present invention is to provide a preparation method of a vegetable oil polyol by a micro-channel reaction device aiming at the defects in the prior art, so as to avoid a cross-linking side reaction caused by non-selective ring opening of secondary hydroxyl groups and other epoxy groups generated in a ring-opening reaction. In order to solve the above technical problem, the present invention discloses a preparation method of a vegetable oil polyol, wherein the preparation method comprises the following steps of: mixing epoxy vegetable oil and an acid catalyst into a first mixed solution; dissolving a 2,3-dihydroxy succinic acid diester compound in an organic solvent to obtain a second mixed solution; respectively pumping the first mixed solution and the second mixed solution into a first micro-reactor of a micro-channel reaction device at the same time for a first ring-opening reaction to obtain a first reaction solution; and pumping a third mixed solution obtained by dissolving long-chain hydroxy fatty acid ester in the organic solvent and the first reaction solution into a second micro-reactor of the micro-channel reaction device at the same time for a continuous second ring-opening reaction, and collecting a reaction solution obtained. The epoxy vegetable oil is any one or a combination of several of epoxy olive oil, epoxy peanut oil, epoxy rapeseed oil, epoxy cottonseed oil, epoxy soybean oil, epoxy coconut oil, epoxy palm oil, epoxy sesame oil, epoxy corn oil and epoxy sunflower seed oil; the acid catalyst is any one or a combination of several of fluoboric acid, concentrated sulfuric acid, p-toluenesulfonic acid, methanesulfonic acid and benzenesulfonic acid; the 2,3-dihydroxy succinic acid diester compound is 2,3-dihydroxy succinic acid dimethyl ester or 2,3-dihydroxy succinic acid diisobutyl ester; the organic solvent is any one or a combination of several of ethyl acetate, di chloromethane, di chloroethane, chloroform, n-hexane, tetrahydrofuran, 1,4-di oxane, carbon tetrachloride, toluene and xylene; and the long-chain hydroxyl fatty acid ester is any one or a combination of several of methyl 14-hydroxymyristate and / or ethyl 14-hydroxymyristate. Specifically, a mass percentage of the acid catalyst and the epoxy vegetable oil is 0.02 to 0.1%: 1. Specifically, in the second mixed solution, a mass-volume ratio of the 2,3-dihydroxy succinic acid diester compound to the organic solvent is 1: 0.5 to 2. Specifically, in the third mixed solution, a mass-volume ratio of the long-chain hydroxyl fatty acid ester to the organic solvent is 1: 1 to 4. Specifically, a reaction molar ratio of epoxy groups in the epoxy vegetable oil to the 2,3-dihydroxy succinic acid diester compound is 1: 0.7 to 0.8. Specifically, a reaction molar ratio of epoxy groups in the epoxy vegetable oil to the long-chain hydroxyl fatty acid ester is 1: 0.1 to 0.2. Specifically, the micro-channel reaction device adopted in the present invention comprises a first feed pump, a second feed pump, a third feed pump, a micro-reaction pipeline, a first micro-mixer, a second micro-mixer, a first micro-reactor, a second micro-reactor and a receiver; the first feed pump and the second feed pump are connected to the first micro-mixer; the first reaction solution and the third feed pump are connected to the second micro-mixer; and the micro-mixer, the micro-reactor and the receiver are all connected in series through a pipeline in sequence. The micro-mixer is a conventional Y-shaped mixer or T-shaped mixer; and a model of the micro-reactor is Vapotech, and a micro-structure heat exchanger (coaxial heat exchanger) is adopted. Specifically, volumes of the first micro-reactor and the second micro-reactor are both 5 mL to 20 mL. Preferably, in the present invention, the first ring-opening reaction is carried out at a reaction temperature of 80°C to 110°C and lasts for 3 minutes to 15 minutes; and the second ring-opening reaction is carried out at a reaction temperature of 80°C to 110°C and lasts for 3 minutes to 15 minutes. A reaction outflow of the micro-reactor is subjected to liquid separation, and an organic phase is neutralized with acid, subjected to liquid separation, dried, and subjected to rotary evaporation to obtain the vegetable oil polyol. Further, a vegetable oil polyol prepared by the above preparation method also falls within the scope of protection of the present invention. Further, an application of the vegetable oil polyol prepared above in preparing a polyurethane coating also falls within the scope of protection of the present invention. Beneficial effects: (1) According to the present invention, a ring-opening reagent with a polyhydroxy and polyester structure is used as a first ring-opening reagent to ensure that a degree of functionality is improved and a hydroxyl value is easily regulated, the ring-opening reaction of most easily reactive epoxy groups is completed through process control, and then the high-activity long-chain hydroxyl fatty acid ester is used to carry out the ring-opening reaction on residual epoxy groups with weak reactivity, so as to obtain a vegetable oil polyol product with a residual epoxy value of about 0.5 to 1. In order to avoid the cross-linking side reaction caused by non-selective ring opening of secondary hydroxyl groups and other epoxy groups generated in the ring-opening reaction, the inventor adopted the micro-reaction technology and selected the micro-channel reaction device as the reaction device to further control the ring-opening groups. In the prepared vegetable oil polyol, the polyester groups are introduced, and a higher hydroxyl value is maintained, and meanwhile, a certain epoxy value residue is realized, so that mechanical properties of polyurethane materials are improved, certain toughness of polyurethane products is maintained, and good corrosion resistance is achieved. (2) According to the present invention, two specific ring-opening reagents are used for a cascade reaction, the prepared vegetable oil polyol is novel in structure, the polyol is moderate, uniform in distribution and low in viscosity, and can replace a traditional petrochemical polyol, and the vegetable oil polyol prepared in the present invention is used for preparing the polyurethane anti-corrosive coating and has strong mechanical properties and high toughness, so that the comprehensive performance is obviously improved. BRIEF DESCRIPTION OF THE DRAWINGS The present invention is further described in detail hereinafter with reference to the drawings and specific embodiments, and the advantages of the above and / or other aspects of the present invention will be clearer. FIG. lisa schematic diagram of a micro-channel reaction device adopted in the present invention. DETAILED DESCRIPTION The present invention can be better understood according to the following embodiments. However, those skilled in the art easily understand that the contents described in the embodiments are only used to illustrate the present invention, and shall not and will not limit the present invention described in detail in the claims. Related determination methods for prepared vegetable oil polyol and polyurethane material in the present invention are as follows: (1) A hydroxyl value is determined according to GB / T 12008.3-2009. (2) A viscosity is determined according to GB / T 12008.7-2010. (3) Surface drying time of a coating is determined according to GB / T 1728-2020 (Method B). (4) Hard drying time of the coating is determined according to GB / T 1728-1979 (Method A). (5) A VOC content is determined according to GB / T 23985-2009 (8.3). (6) A surface hardness of the coating is determined according to GB / T 6739-2006. (7) Impact resistance of the coating is determined according to GB / T 1732-2020. (8) Toughness of the coating is determined according to GB / T 1731-2020 (4). (9) Adhesion of the coating is determined according to GB / T 5210-2006. (10) A neutral salt spray corrosion resistance experiment is determined according to GB / T 1771-2007. Example 1 (1) Preparation of vegetable oil polyol: epoxy soybean oil (10 mL, epoxy value 6.2%, epoxy group 38.4 mmol) and fluoboric acid (20 mg, 50%) were mixed to obtain a first mixed solution, 2,3-dihydroxy succinic acid dimethyl ester (5.13 g, 28.8 mmol) and ethyl acetate (10 mL) were mixed to obtain a second mixed solution, a reactor temperature was adjusted to 100°C, and the first mixed solution and the second mixed solution were pumped into a microreactor with a volume of 10 mL in a micro-channel reaction device at rates of 1 mL / min and 1.15 mL / min respectively for a ring-opening reaction, so as to obtain a first reaction solution. Methyl 14-hydroxymyristate (1.47 g, 5.7 mmol) and ethyl acetate (20 mL) were mixed to obtain a third mixed solution, the reactor temperature was adjusted to 100°C, and the third mixed solution was pumped at a rate of 2 mL / min together with the first reaction solution into a micro-reactor with a volume of 15 mL in the micro-channel reaction device for a ringopening reaction. An obtained reaction solution was washed with sodium bicarbonate solution (30 mL, 10%) and water (30 mLx2) in sequence, and an organic phase was dried and concentrated to obtain a soybean oil polyol, which had a hydroxyl value of 210 mgKOH / g, an epoxy value of 0.6 and a viscosity of 808 mPa»s. (2) Preparation of vegetable oil-based polyurethane coating: a certain amount of vegetable oil polyol was mixed with isocyanate MDI (according to a molar ratio of NCO functional groups to OH functional groups of 1.25: 1 to 1.05), and then a catalyst (3%o of polyol mass) was added to react for 2 hours to obtain a prepolymer mixed solution. A certain amount of hydrophilic chain extender and other additives were added into the prepolymer mixed solution to react for 3 hours to obtain a polymer mixed solution, a proper amount of neutralizer was added to neutralize the polymer mixed solution to neutrality, and a diluent was added for high-speed shear emulsification to form a polyurethane emulsion. A substrate of steel plate was sprayed once, a dry film thickness was 60 pm to 80 pm, and the coating was tested after standing in a laboratory environment for 168 hour. Example 2 (1) Preparation of vegetable oil polyol: epoxy soybean oil (10 mL, epoxy value 6.2%, epoxy group 38.4 mmol) and fluoboric acid (20 mg, 50%) were mixed to obtain a first mixed solution, 2,3-dihydroxy succinic acid dimethyl ester (4.78g, 26.9mmol) and ethyl acetate (10 mL) were mixed to obtain a second mixed solution, a reactor temperature was adjusted to 100°C, and the first mixed solution and the second mixed solution were pumped into a microreactor with a volume of 10 mL in a micro-channel reaction device at rates of 1 mL / min and 1.14 mL / min respectively for a ring-opening reaction, so as to obtain a first reaction solution. Methyl 14-hydroxymyristate (1.99g, 7.7mmol) and ethyl acetate (20 mL) were mixed to obtain a third mixed solution, the reactor temperature was adjusted to 100°C, and the third mixed solution was pumped at a rate of 2 mL / min together with the first reaction solution into a micro-reactor with a volume of 15 mL in the micro-channel reaction device for a ring-opening reaction. An obtained reaction solution was washed with sodium bicarbonate solution (30 mL, 10%) and water (30 mLx2) in sequence, and an organic phase was dried and concentrated to obtain a soybean oil polyol, which had a hydroxyl value of 205 mgKOH / g, an epoxy value of 0.7 and a viscosity of 692 mPa»s. (2) Preparation of vegetable oil-based polyurethane coating: the polyurethane coating was prepared according to the general method of (2) in Example 1. Example 3 (1) Preparation of vegetable oil polyol: epoxy soybean oil (10 mL, epoxy value 6.2%, epoxy group 38.4 mmol) and fluoboric acid (20 mg, 50%) were mixed to obtain a first mixed solution, 2,3-dihydroxy succinic acid dimethyl ester (5.47g, 30.7mmol) and ethyl acetate (10 mL) were mixed to obtain a second mixed solution, a reactor temperature was adjusted to 100°C, and the first mixed solution and the second mixed solution were pumped into a microreactor with a volume of 10 mL in a micro-channel reaction device at rates of 1 mL / min and 1.16 mL / min respectively for a ring-opening reaction, so as to obtain a first reaction solution. Methyl 14-hydroxymyristate (1.03g, 4.0mmol) and ethyl acetate (20 mL) were mixed to obtain a third mixed solution, the reactor temperature was adjusted to 100°C, and the third mixed solution was pumped at a rate of 2 mL / min together with the first reaction solution into a micro-reactor with a volume of 15 mL in the micro-channel reaction device for a ring-opening reaction. An obtained reaction solution was washed with sodium bicarbonate solution (30 mL, 10%) and water (30 mLx2) in sequence, and an organic phase was dried and concentrated to obtain a soybean oil polyol, which had a hydroxyl value of 220 mgKOH / g, an epoxy value of 0.6 and a viscosity of 1026 mPa»s. (2) Preparation of vegetable oil-based polyurethane coating: the polyurethane coating was prepared according to the general method of (2) in Example 1. Example 4 (1) Preparation of vegetable oil polyol: epoxy soybean oil (10 mL, epoxy value 6.2%, epoxy group 38.4 mmol) and fluoboric acid (20 mg, 50%) were mixed to obtain a first mixed solution, 2,3-dihydroxy succinic acid dimethyl ester (4.78g, 26.9mmol) and ethyl acetate (10 mL) were mixed to obtain a second mixed solution, a reactor temperature was adjusted to 100°C, and the first mixed solution and the second mixed solution were pumped into a microreactor with a volume of 10 mL in a micro-channel reaction device at rates of 1 mL / min and 1.14 mL / min respectively for a ring-opening reaction, so as to obtain a first reaction solution. Methyl 14-hydroxymyristate (1,47g, 5.7mmol) and ethyl acetate (20 mL) were mixed to obtain a third mixed solution, the reactor temperature was adjusted to 100°C, and the third mixed solution was pumped at a rate of 2 mL / min together with the first reaction solution into a micro-reactor with a volume of 15 mL in the micro-channel reaction device for a ring-opening reaction. An obtained reaction solution was washed with sodium bicarbonate solution (30 mL, 10%) and water (30 mLx2) in sequence, and an organic phase was dried and concentrated to obtain a soybean oil polyol, which had a hydroxyl value of 203 mgKOH / g, an epoxy value of 0.8 and a viscosity of 653 mPa»s. (2) Preparation of vegetable oil-based polyurethane coating: the polyurethane coating was prepared according to the general method of (2) in Example 1. Example 5 (1) Preparation of vegetable oil polyol: epoxy soybean oil (10 mL, epoxy value 6.2%, epoxy group 38.4 mmol) and fluoboric acid (20 mg, 50%) were mixed to obtain a first mixed solution, 2,3-dihydroxy succinic acid dimethyl ester (5.47g, 30.7mmol) and ethyl acetate (10 mL) were mixed to obtain a second mixed solution, a reactor temperature was adjusted to 100°C, and the first mixed solution and the second mixed solution were pumped into a microreactor with a volume of 10 mL in a micro-channel reaction device at rates of 1 mL / min and 1.16 mL / min respectively for a ring-opening reaction, so as to obtain a first reaction solution. Methyl 14-hydroxymyristate (1.99g, 7.7mmol) and ethyl acetate (20 mL) were mixed to obtain a third mixed solution, the reactor temperature was adjusted to 100°C, and the third mixed solution was pumped at a rate of 2 mL / min together with the first reaction solution into a micro-reactor with a volume of 15 mL in the micro-channel reaction device for a ring-opening reaction. An obtained reaction solution was washed with sodium bicarbonate solution (30 mL, 10%) and water (30 mLx2) in sequence, and an organic phase was dried and concentrated to obtain a soybean oil polyol, which had a hydroxyl value of 218 mgKOH / g, an epoxy value of 0.5 and a viscosity of 988 mPa»s. (2) Preparation of vegetable oil-based polyurethane coating: the polyurethane coating was prepared according to the general method of (2) in Example 1. Example 6 (1) Preparation of vegetable oil polyol: epoxy soybean oil (10 mL, epoxy value 6.2%, epoxy group 38.4 mmol) and fluoboric acid (20 mg, 50%) were mixed to obtain a first mixed solution, 2,3-dihydroxy succinic acid dimethyl ester (5.13 g, 28.8 mmol) and ethyl acetate (10 mL) were mixed to obtain a second mixed solution, a reactor temperature was adjusted to 80°C, and the first mixed solution and the second mixed solution were pumped into a micro-reactor with a volume of 10 mL in a micro-channel reaction device at rates of 1 mL / min and 1.15 mL / min respectively for a ring-opening reaction, so as to obtain a first reaction solution. Methyl 14-hydroxymyristate (1.47 g, 5.7 mmol) and ethyl acetate (20 mL) were mixed to obtain a third mixed solution, the reactor temperature was adjusted to 80°C, and the third mixed solution was pumped at a rate of 2 mL / min together with the first reaction solution into a micro-reactor with a volume of 15 mL in the micro-channel reaction device for a ringopening reaction. An obtained reaction solution was washed with sodium bicarbonate solution (30 mL, 10%) and water (30 mL^2) in sequence, and an organic phase was dried and concentrated to obtain a soybean oil polyol, which had a hydroxyl value of 201 mgKOH / g, an epoxy value of 0.9 and a viscosity of 628 mPa»s. (2) Preparation of vegetable oil-based polyurethane coating: the polyurethane coating was prepared according to the general method of (2) in Example 1. Example 7 (1) Preparation of vegetable oil polyol: epoxy soybean oil (10 mL, epoxy value 6.2%, epoxy group 38.4 mmol) and fluoboric acid (20 mg, 50%) were mixed to obtain a first mixed solution, 2,3-dihydroxy succinic acid dimethyl ester (5.13 g, 28.8 mmol) and ethyl acetate (10 mL) were mixed to obtain a second mixed solution, a reactor temperature was adjusted to 110°C, and the first mixed solution and the second mixed solution were pumped into a microreactor with a volume of 10 mL in a micro-channel reaction device at rates of 1 mL / min and 1.15 mL / min respectively for a ring-opening reaction, so as to obtain a first reaction solution. Methyl 14-hydroxymyristate (1.47, 5.7 mmol) and ethyl acetate (20 mL) were mixed to obtain a third mixed solution, the reactor temperature was adjusted to 110°C, and the third mixed solution was pumped at a rate of 2 mL / min together with the first reaction solution into a micro-reactor with a volume of 15 mL in the micro-channel reaction device for a ring-opening reaction. An obtained reaction solution was washed with sodium bicarbonate solution (30 mL, 10%) and water (30 mLx2) in sequence, and an organic phase was dried and concentrated to obtain a soybean oil polyol, which had a hydroxyl value of 208 mgKOH / g, an epoxy value of 0.7 and a viscosity of 784 mPa»s. (2) Preparation of vegetable oil-based polyurethane coating: the polyurethane coating was prepared according to the general method of (2) in Example 1. Example 8 (1) Preparation of vegetable oil polyol: epoxy soybean oil (10 mL, epoxy value 6.2%, epoxy group 38.4 mmol) and fluoboric acid (20 mg, 50%) were mixed to obtain a first mixed solution, 2,3-dihydroxy succinic acid dimethyl ester (5.13 g, 28.8 mmol) and ethyl acetate (10 mL) were mixed to obtain a second mixed solution, a reactor temperature was adjusted to 100°C, and the first mixed solution and the second mixed solution were pumped into a microreactor with a volume of 10 mL in a micro-channel reaction device at rates of 2 mL / min and 2.3 mL / min respectively for a ring-opening reaction, so as to obtain a first reaction solution. Methyl 14-hydroxymyristate (1.47 g, 5.7 mmol) and ethyl acetate (20 mL) were mixed to obtain a third mixed solution, the reactor temperature was adjusted to 100°C, and the third mixed solution was pumped at a rate of 4 mL / min together with the first reaction solution into a micro-reactor with a volume of 20 mL in the micro-channel reaction device for a ringopening reaction. An obtained reaction solution was washed with sodium bicarbonate solution (30 mL, 10%) and water (30 mL^2) in sequence, and an organic phase was dried and concentrated to obtain a soybean oil polyol, which had a hydroxyl value of 200 mgKOH / g, an epoxy value of 1 and a viscosity of 576 mPa»s. (2) Preparation of vegetable oil-based polyurethane coating: the polyurethane coating was prepared according to the general method of (2) in Example 1. Example 9 (1) Preparation of vegetable oil polyol: epoxy soybean oil (10 mL, epoxy value 6.2%, epoxy group 38.4 mmol) and fluoboric acid (20 mg, 50%) were mixed to obtain a first mixed solution, 2,3-dihydroxy succinic acid dimethyl ester (5.13 g, 28.8 mmol) and ethyl acetate (10 mL) were mixed to obtain a second mixed solution, a reactor temperature was adjusted to 100°C, and the first mixed solution and the second mixed solution were pumped into a microreactor with a volume of 10 mL in a micro-channel reaction device at rates of 0.5 mL / min and 0.58 mL / min respectively for a ring-opening reaction, so as to obtain a first reaction solution. Methyl 14-hydroxymyristate (1.47 g, 5.7 mmol) and ethyl acetate (20 mL) were mixed to obtain a third mixed solution, the reactor temperature was adjusted to 100°C, and the third mixed solution was pumped at a rate of 1 mL / min together with the first reaction solution into a micro-reactor with a volume of 15 mL in the micro-channel reaction device for a ring opening reaction. An obtained reaction solution was washed with sodium bicarbonate solution (30 mL, 10%) and water (30 mLx2) in sequence, and an organic phase was dried and concentrated to obtain a soybean oil polyol, which had a hydroxyl value of 207 mgKOH / g, an epoxy value of 0.5 and a viscosity of 792 mPa»s. (2) Preparation of vegetable oil-based polyurethane coating: the polyurethane coating was prepared according to the general method of (2) in Example 1. Example 10 (1) Preparation of vegetable oil polyol: epoxy soybean oil (10 mL, epoxy value 6.2%, epoxy group 38.4 mmol) and fluoboric acid (20 mg, 50%) were mixed to obtain a first mixed solution, 2,3-dihydroxy succinic acid diisobutyl ester (7.55g, 28.8 mmol) and ethyl acetate (10 mL) were mixed to obtain a second mixed solution, a reactor temperature was adjusted to 100°C, and the first mixed solution and the second mixed solution were pumped into a microreactor with a volume of 10 mL in a micro-channel reaction device at rates of 1 mL / min and 1.16 mL / min respectively for a ring-opening reaction, so as to obtain a first reaction solution. Methyl 14-hydroxymyristate (1.47 g, 5.7 mmol) and ethyl acetate (20 mL) were mixed to obtain a third mixed solution, the reactor temperature was adjusted to 100°C, and the third mixed solution was pumped at a rate of 2 mL / min together with the first reaction solution into a micro-reactor with a volume of 15 mL in the micro-channel reaction device for a ringopening reaction. An obtained reaction solution was washed with sodium bicarbonate solution (30 mL, 10%) and water (30 mLx2) in sequence, and an organic phase was dried and concentrated to obtain a soybean oil polyol, which had a hydroxyl value of 185 mgKOH / g, an epoxy value of 0.6 and a viscosity of 558 mPa»s. (2) Preparation of vegetable oil-based polyurethane coating: the polyurethane coating was prepared according to the general method of (2) in Example 1. Example 11 (1) Preparation of vegetable oil polyol: epoxy soybean oil (10 mL, epoxy value 6.2%, epoxy group 38.4 mmol) and fluoboric acid (20 mg, 50%) were mixed to obtain a first mixed solution, 2,3-dihydroxy succinic acid dimethyl ester (5.13 g, 28.8 mmol) and ethyl acetate (10 mL) were mixed to obtain a second mixed solution, a reactor temperature was adjusted to 100°C, and the first mixed solution and the second mixed solution were pumped into a micro reactor with a volume of 10 mL in a micro-channel reaction device at rates of 1 mL / min and 1.15 mL / min respectively for a ring-opening reaction, so as to obtain a first reaction solution. Ethyl 14-hydroxymyristate (1.55 g, 5.7 mmol) and ethyl acetate (20 mL) were mixed to obtain a third mixed solution, the reactor temperature was adjusted to 100°C, and the third mixed solution was pumped at a rate of 2 mL / min together with the first reaction solution into a micro-reactor with a volume of 15 mL in the micro-channel reaction device for a ring-opening reaction. An obtained reaction solution was washed with sodium bicarbonate solution (30 mL, 10%) and water (30 mLx2) in sequence, and an organic phase was dried and concentrated to obtain a soybean oil polyol, which had a hydroxyl value of 211 mgKOH / g, an epoxy value of 0.7 and a viscosity of 853 mPa»s. (2) Preparation of vegetable oil-based polyurethane coating: the polyurethane coating was prepared according to the general method of (2) in Example 1. Example 12 (1) Preparation of vegetable oil polyol: epoxy cottonseed oil (13 mL, epoxy value 5.1%, epoxy group 38.4 mmol) and fluoboric acid (20 mg, 50%) were mixed to obtain a first mixed solution, 2,3-dihydroxy succinic acid dimethyl ester (5.13 g, 28.8 mmol) and ethyl acetate (10 mL) were mixed to obtain a second mixed solution, a reactor temperature was adjusted to 100°C, and the first mixed solution and the second mixed solution were pumped into a microreactor with a volume of 10 mL in a micro-channel reaction device at rates of 1.3 mL / min and 1.15 mL / min respectively for a ring-opening reaction, so as to obtain a first reaction solution. Methyl 14-hydroxymyristate (1.47 g, 5.7 mmol) and ethyl acetate (20 mL) were mixed to obtain a third mixed solution, the reactor temperature was adjusted to 100°C, and the third mixed solution was pumped at a rate of 2 mL / min together with the first reaction solution into a micro-reactor with a volume of 15 mL in the micro-channel reaction device for a ringopening reaction. An obtained reaction solution was washed with sodium bicarbonate solution (30 mL, 10%) and water (30 mLx2) in sequence, and an organic phase was dried and concentrated to obtain a soybean oil polyol, which had a hydroxyl value of 188 mgKOH / g, an epoxy value of 0.6 and a viscosity of 789 mPa»s. (2) Preparation of vegetable oil-based polyurethane coating: the polyurethane coating was prepared according to the general method of (2) in Example 1. Example 13 (1) Preparation of vegetable oil polyol: epoxy sunflower seed oil (10 mL, epoxy value 6.0%, epoxy group 38.2mmol) and fluoboric acid (20 mg, 50%) were mixed to obtain a first mixed solution, 2,3-dihydroxy succinic acid dimethyl ester (5.13 g, 28.8 mmol) and ethyl acetate (10 mL) were mixed to obtain a second mixed solution, a reactor temperature was adjusted to 100°C, and the first mixed solution and the second mixed solution were pumped into a micro-reactor with a volume of 10 mL in a micro-channel reaction device at rates of 1 mL / min and 1.15 mL / min respectively for a ring-opening reaction, so as to obtain a first reaction solution. Methyl 14-hydroxymyristate (1.47 g, 5.7 mmol) and ethyl acetate (20 mL) were mixed to obtain a third mixed solution, the reactor temperature was adjusted to 100°C, and the third mixed solution was pumped at a rate of 2 mL / min together with the first reaction solution into a micro-reactor with a volume of 15 mL in the micro-channel reaction device for a ring-opening reaction. An obtained reaction solution was washed with sodium bicarbonate solution (30 mL, 10%) and water (30 mL^2) in sequence, and an organic phase was dried and concentrated to obtain a soybean oil polyol, which had a hydroxyl value of 207 mgKOH / g, an epoxy value of 0.5 and a viscosity of 812 mPa»s. (2) Preparation of vegetable oil-based polyurethane coating: the polyurethane coating was prepared according to the general method of (2) in Example 1. Example 14 (1) Preparation of vegetable oil polyol: epoxy rapeseed oil (13.5 mL, epoxy value 4.9%, epoxy group 38.4 mmol) and fluoboric acid (20 mg, 50%) were mixed to obtain a first mixed solution, 2,3-dihydroxy succinic acid dimethyl ester (5.13 g, 28.8 mmol) and ethyl acetate (10 mL) were mixed to obtain a second mixed solution, a reactor temperature was adjusted to 100°C, and the first mixed solution and the second mixed solution were pumped into a microreactor with a volume of 10 mL in a micro-channel reaction device at rates of 1.35 mL / min and 1.15 mL / min respectively for a ring-opening reaction, so as to obtain a first reaction solution. Methyl 14-hydroxymyristate (1.47, 5.7 mmol) and ethyl acetate (20 mL) were mixed to obtain a third mixed solution, the reactor temperature was adjusted to 100°C, and the third mixed solution was pumped at a rate of 2 mL / min together with the first reaction solution into a micro-reactor with a volume of 15 mL in the micro-channel reaction device for a ringopening reaction. An obtained reaction solution was washed with sodium bicarbonate solution (30 mL, 10%) and water (30 mL*2) in sequence, and an organic phase was dried and concentrated to obtain a soybean oil polyol, which had a hydroxyl value of 182 mgKOH / g, an epoxy value of 0.5 and a viscosity of 991 mPa»s. (2) Preparation of vegetable oil-based polyurethane coating: the polyurethane coating was prepared according to the general method of (2) in Example 1. Example 15 (1) Preparation of vegetable oil polyol: epoxy corn oil (12.3 mL, epoxy value 5.2%, epoxy group 38.4mmol) and fluoboric acid (20 mg, 50%) were mixed to obtain a first mixed solution, 2,3-dihydroxy succinic acid dimethyl ester (5.13 g, 28.8 mmol) and ethyl acetate (10 mL) were mixed to obtain a second mixed solution, a reactor temperature was adjusted to 100°C, and the first mixed solution and the second mixed solution were pumped into a microreactor with a volume of 10 mL in a micro-channel reaction device at rates of 1.23 mL / min and 1.15 mL / min respectively for a ring-opening reaction, so as to obtain a first reaction solution. Methyl 14-hydroxymyristate (1.47 g, 5.7 mmol) and ethyl acetate (20 mL) were mixed to obtain a third mixed solution, the reactor temperature was adjusted to 100°C, and the third mixed solution was pumped at a rate of 2 mL / min together with the first reaction solution into a micro-reactor with a volume of 15 mL in the micro-channel reaction device for a ringopening reaction. An obtained reaction solution was washed with sodium bicarbonate solution (30 mL, 10%) and water (30 mL^2) in sequence, and an organic phase was dried and concentrated to obtain a soybean oil polyol, which had a hydroxyl value of 188 mgKOH / g, an epoxy value of 0.5 and a viscosity of 792 mPa»s. (2) Preparation of vegetable oil-based polyurethane coating: the polyurethane coating was prepared according to the general method of (2) in Example 1. Example 16 (1) Preparation of vegetable oil polyol: epoxy peanut oil (14.4 mL, epoxy value 4.5%, epoxy group 38.4 mmol) and fluoboric acid (20 mg, 50%) were mixed to obtain a first mixed solution, 2,3-dihydroxy succinic acid dimethyl ester (5.13 g, 28.8 mmol) and ethyl acetate (10 mL) were mixed to obtain a second mixed solution, a reactor temperature was adjusted to 100°C, and the first mixed solution and the second mixed solution were pumped into a microreactor with a volume of 10 mL in a micro-channel reaction device at rates of 1.44 mL / min and 1.15 mL / min respectively for a ring-opening reaction, so as to obtain a first reaction solution. Methyl 14-hydroxymyri state (1.47 g, 5.7 mmol) and ethyl acetate (20 mL) were mixed to obtain a third mixed solution, the reactor temperature was adjusted to 100°C, and the third mixed solution was pumped at a rate of 2 mL / min together with the first reaction solution into a micro-reactor with a volume of 15 mL in the micro-channel reaction device for a ringopening reaction. An obtained reaction solution was washed with sodium bicarbonate solution (30 mL, 10%) and water (30 mL^2) in sequence, and an organic phase was dried and concentrated to obtain a soybean oil polyol, which had a hydroxyl value of 168 mgKOH / g, an epoxy value of 0.6 and a viscosity of 655 mPa»s. (2) Preparation of vegetable oil-based polyurethane coating: the polyurethane coating was prepared according to the general method of (2) in Example 1. Comparative Example 1 (1) Preparation of vegetable oil polyol: epoxy soybean oil (10 mL, epoxy value 6.2%, epoxy group 38.4 mmol), fluoboric acid (20 mg, 50%), 2,3-dihydroxy succinic acid dimethyl ester (5.13 g, 28.8 mmol) and ethyl acetate (30 mL) were allowed to react at 100°C for 6 hours, then added with methyl 14-hydroxymyristate (1.47 g, 5.7 mmol) to continuously react for 4 hours, and cooled to room temperature. An obtained reaction solution was washed with sodium bicarbonate solution (30 mL, 10%) and water (30 mLx2) in sequence, and an organic phase was dried and concentrated to obtain a soybean oil polyol, which had a hydroxyl value of 121 mgKOH / g, an epoxy value of 1.3 and a viscosity of 1650 mPa»s. (2) Preparation of vegetable oil-based polyurethane coating: the polyurethane coating was prepared according to the general method of (2) in Example 1. Comparative Example 2 (1) Preparation of vegetable oil polyol: epoxy soybean oil (10 mL, epoxy value 6.2%, epoxy group 38.4 mmol) and fluoboric acid (20 mg, 50%) were mixed to obtain a first mixed solution, 2,3-dihydroxy succinic acid dimethyl ester (4.10 g, 23.0 mmol) and ethyl acetate (10 mL) were mixed to obtain a second mixed solution, a reactor temperature was adjusted to 100°C, and the first mixed solution and the second mixed solution were pumped into a microreactor with a volume of 10 mL in a micro-channel reaction device at rates of 1 mL / min and 1.14 mL / min respectively for a ring-opening reaction, so as to obtain a first reaction solution. Methyl 14-hydroxymyri state (1.47 g, 5.7 mmol) and ethyl acetate (20 mL) were mixed to obtain a third mixed solution, the reactor temperature was adjusted to 100°C, and the third mixed solution was pumped at a rate of 2 mL / min together with the first reaction solution into a micro-reactor with a volume of 15 mL in the micro-channel reaction device for a ringopening reaction. An obtained reaction solution was washed with sodium bicarbonate solution (30 mL, 10%) and water (30 mL^2) in sequence, and an organic phase was dried and concentrated to obtain a soybean oil polyol, which had a hydroxyl value of 152 mgKOH / g, an epoxy value of 1.6 and a viscosity of 512 mPa»s. (2) Preparation of vegetable oil-based polyurethane coating: the polyurethane coating was prepared according to the general method of (2) in Example 1. Comparative Example 3 (1) Preparation of vegetable oil polyol: epoxy soybean oil (10 mL, epoxy value 6.2%, epoxy group 38.4 mmol) and fluoboric acid (20 mg, 50%) were mixed to obtain a first mixed solution, 2,3-dihydroxy succinic acid dimethyl ester (6.15g, 34.6mmol) and ethyl acetate (10 mL) were mixed to obtain a second mixed solution, a reactor temperature was adjusted to 100°C, and the first mixed solution and the second mixed solution were pumped into a microreactor with a volume of 10 mL in a micro-channel reaction device at rates of 1 mL / min and 1.17 mL / min respectively for a ring-opening reaction, so as to obtain a first reaction solution. Methyl 14-hydroxymyristate (0.99g, 4.0mmol) and ethyl acetate (20 mL) were mixed to obtain a third mixed solution, the reactor temperature was adjusted to 100°C, and the third mixed solution was pumped at a rate of 2 mL / min together with the first reaction solution into a micro-reactor with a volume of 15 mL in the micro-channel reaction device for a ring-opening reaction. An obtained reaction solution was washed with sodium bicarbonate solution (30 mL, 10%) and water (30 mLx2) in sequence, and an organic phase was dried and concentrated to obtain a soybean oil polyol, which had a hydroxyl value of 160 mgKOH / g, an epoxy value of 1.2 and a viscosity of 1856 mPa»s. (2) Preparation of vegetable oil-based polyurethane coating: the polyurethane coating was prepared according to the general method of (2) in Example 1. Comparative Example 4 (1) Preparation of vegetable oil polyol: epoxy soybean oil (10 mL, epoxy value 6.2%, epoxy group 38.4 mmol) and fluoboric acid (20 mg, 50%) were mixed to obtain a first mixed solution, 2,3-dihydroxy succinic acid dimethyl ester (5.13 g, 28.8 mmol) and ethyl acetate (10 mL) were mixed to obtain a second mixed solution, a reactor temperature was adjusted to 100°C, and the first mixed solution and the second mixed solution were pumped into a microreactor with a volume of 10 mL in a micro-channel reaction device at rates of 1 mL / min and 1.15 mL / min respectively for a ring-opening reaction, so as to obtain a first reaction solution. Methyl 14-hydroxymyristate (3g, 11.6mmol) and ethyl acetate (20 mL) were mixed to obtain a third mixed solution, the reactor temperature was adjusted to 100°C, and the third mixed solution was pumped at a rate of 2 mL / min together with the first reaction solution into a micro-reactor with a volume of 15 mL in the micro-channel reaction device for a ring-opening reaction. An obtained reaction solution was washed with sodium bicarbonate solution (30 mL, 10%) and water (30 mL^2) in sequence, and an organic phase was dried and concentrated to obtain a soybean oil polyol, which had a hydroxyl value of 158 mgKOH / g, an epoxy value of 1.1 and a viscosity of 1711 mPa»s. (2) Preparation of vegetable oil-based polyurethane coating: the polyurethane coating was prepared according to the general method of (2) in Example 1. Property indexes of polyurethane coatings prepared in Examples 1 to 16 and Comparative Examples 1 to 4 referred to Table 1. Table 1 Property indexes of vegetable oil-based polyurethane coatings prepared in examples and comparative examples Test item Exampl e 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Example 10 Example 11 Surface drying time (h) 1 1 1 1 1 1 1 1 1 1 1 Hard drying time (h) 4 4 4 4 4 4 4 4 4 4 4 Surface hardness 2H 2H 3H H 2H H 2H H 2H H 2H Toughness (mm) 1 1 1 1 1 1 1 1 1 1 1 Impact resistance (Front, 50 cm) Passed Passed Passed Passed Passed Passed Passed Passed Passed Passed Passed Adhesion (MPa) 14 13 14 10 15 11 11 10 13 11 12 Salt spray resistance (h) 300 300 300 300 290 300 240 300 290 280 300 Table 1 (Continued Table) Property indexes of vegetable oil-based polyurethane coatings prepared in examples and comparative examples Test item Example 12 Example 13 Example 14 Example 15 Example 16 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Surface drying time (h) Hard drying time (h) 1 4 1 4 1 4 1 4 1 4 1 4 1 6 1 4 1 4 Surface hardness H 2H H H H F F F F Toughness (mm) 1 1 1 1 1 2 2 2 2 Impact resistance (front and back, 50 cm) Passed Passed Passed Passed Passed Not passed Not passed Not passed Not passed Adhesion (MPa) 11 13 12 12 11 12 9 15 13 Salt spray resistance (h) 300 300 300 300 300 180 210 220 220 It could be seen from the data in Table 1 that, in a conventional reaction bottle, due to an uncontrollable process, there were many cross-linking side reactions, leading to serious attenuation of hydroxyl value, large viscosity, and performance reduction of vegetable oilbased polyurethane coating. In the present invention, a micro-reaction technology was adopted, a dosage of the ring-opening reagent was controlled, and there was a little epoxy value residue, so that the prepared vegetable oil polyol was introduced with the polyester groups, the hydroxyl value was higher, and the mechanical properties and toughness of the polyurethane material were improved, thus achieving good corrosion resistance. The present invention provides an idea and a method for a preparation method of a vegetable oil polyol and an application of the vegetable oil polyol in a polyurethane anticorrosive coating, with many methods and ways to realize the technical solution specifically. Those described above are merely the preferred embodiments of the present invention, and it should be pointed out that those of ordinary skills in the art may further make improvements and decorations without departing from the principle of the present invention, and these improvements and decorations should also be regarded as the scope of protection of the present invention. All the unspecified components in the embodiments can be realized by the prior art.

Claims

1. A preparation method of a vegetable oil polyol, wherein the preparation method comprises the following steps of: mixing epoxy vegetable oil and an acid catalyst into a first mixed solution; dissolving a 2,3-dihydroxy succinic acid diester compound in an organic solvent to obtain a second mixed solution; respectively pumping the first mixed solution and the second mixed solution into a first micro-reactor of a micro-channel reaction device at the same time for a first ring-opening reaction to obtain a first reaction solution; and pumping a third mixed solution obtained by dissolving long-chain hydroxy fatty acid ester in the organic solvent and the first reaction solution into a second micro-reactor of the micro-channel reaction device at the same time for a continuous second ring-opening reaction, and collecting a reaction solution obtained.

2. The preparation method of the vegetable oil polyol according to claim 1, wherein the epoxy vegetable oil is any one or a combination of several of epoxy olive oil, epoxy peanut oil, epoxy rapeseed oil, epoxy cottonseed oil, epoxy soybean oil, epoxy coconut oil, epoxy palm oil, epoxy sesame oil, epoxy corn oil and epoxy sunflower seed oil; the acid catalyst is any one or a combination of several of fluoboric acid, concentrated sulfuric acid, p-toluenesulfonic acid, methanesulfonic acid and benzenesulfonic acid; the 2,3-dihydroxy succinic acid diester compound is 2,3-dihydroxy succinic acid dimethyl ester or 2,3-dihydroxy succinic acid diisobutyl ester; the organic solvent is any one or a combination of several of ethyl acetate, di chloromethane, di chloroethane, chloroform, n-hexane, tetrahydrofuran, 1,4-dioxane, carbon tetrachloride, toluene and xylene; and the long-chain hydroxyl fatty acid ester is any one or a combination of several of methyl 14-hydroxymyristate and / or ethyl 14-hy droxy my ri state.

3. The preparation method of the vegetable oil polyol according to claim 1, wherein a mass percentage of the acid catalyst and the epoxy vegetable oil is 0.02 to 0.1%: 1.

4. The preparation method of the vegetable oil polyol according to claim 1, wherein a mass-volume ratio of the 2,3-dihydroxy succinic acid diester compound to the organic solvent is 1: 0.5 to 2.

5. The preparation method of the vegetable oil polyol according to claim 1, wherein a mass-volume ratio of the long-chain hydroxyl fatty acid ester to the organic solvent is 1: 1 to 4.

6. The preparation method of the vegetable oil polyol according to claim 1, wherein a reaction molar ratio of epoxy groups in the epoxy vegetable oil to the 2,3-dihydroxy succinic acid diester compound is 1: 0.7 to 0.8.

7. The preparation method of the vegetable oil polyol according to claim 1, wherein a reaction molar ratio of epoxy groups in the epoxy vegetable oil to the long-chain hydroxyl fatty acid ester is 1: 0.1 to 0.2.

8. The preparation method of the vegetable oil polyol according to claim 1, wherein volumes of the first micro-reactor and the second micro-reactor are both 5 mL to 20 mL; the first ring-opening reaction is carried out at a reaction temperature of 80°C to 110°C and lasts for 3 minutes to 15 minutes; and the second ring-opening reaction is carried out at a reaction temperature of 80°C to 110°C and lasts for 3 minutes to 15 minutes.

9. A vegetable oil polyol prepared by the preparation method according to any one of claims 1 to 8.

10. An application of the vegetable oil polyol according to claim 9 in preparing a polyurethane coating.T +44(0)30 0300 2000

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