Method for preparing bio-based polyol and use of bio-based polyol

Abstract

The present invention relates to the technical field of the preparation of polyols. Disclosed are a method for preparing a bio-based polyol and a use of the bio-based polyol. In the present invention, a tartrate is selected as a first ring-opening reagent to carry out a first ring-opening reaction on an epoxy group, a second ring-opening reagent containing a secondary alcohol is then used to carry out a second ring-opening reaction, and finally, a primary alcohol is used to carry out a third ring-opening reaction on the rest epoxy group to obtain a bio-based polyol product having an epoxy value close to 0. The bio-based polyol prepared in the present invention is moderate, has a uniform distribution and a relatively low viscosity, and can replace traditional petrochemical polyols. A polyurethane coating prepared from the bio-based polyol prepared by the method of the present invention has remarkably improved performance.

Description

Preparation method and application of bio-based polyol Technical Field

[0001] The present invention relates to the technical field of polyol preparation, and in particular to a preparation method and application of bio-based polyol. Background Art

[0002] Polyurethane is a polymer with repeating urethane segments, produced by the reaction of polyols and isocyanates. Polyurethane products are categorized into two main categories: foamed and non-foamed. Foamed products include soft, rigid, and semi-rigid polyurethane foams; non-foamed products include coatings, adhesives, synthetic leather, elastomers, and elastic fibers. Isocyanates, one of the two monomers used in polyurethane synthesis, are relatively rare, primarily MDI and TDI. The other monomer, polyols, are a diverse and varied product, with diverse downstream applications and room for further research.

[0003] The development of vegetable oil polyols is considered to be an effective way to develop bio-based materials. As an important monomer of bio-based polyurethane materials, it is derived from vegetable oil through chemically modified molecular structure. It is an important renewable resource. It reacts with isocyanate compounds to form polyurethane and is a good alternative raw material for petroleum-based polyols.

[0004] At present, there are many brands of bio-based polyurethane foam products on the market. However, in the field of coatings, the development of bio-based polyols derived from plant oils is relatively slow, especially in anti-corrosion coatings. At present, the polyurethane coatings developed using bio-based polyols are difficult to coordinate in terms of hardness, toughness, anti-corrosion and other aspects.

[0005] Researchers have conducted extensive research in this field. The main methods for synthesizing vegetable oil polyols are: 1) Using the basic core of triglycerides, vegetable oils and polyols are subjected to alcoholysis reactions to generate polyhydroxy compounds. This scheme can obtain high-functionality polyol monomers, but the hydroxyl distribution is uneven and uncontrollable, which limits its application; 2) Using ozone to oxidize unsaturated double bonds in vegetable oils to generate polyhydroxy compounds with terminal hydroxyl groups. This scheme can obtain highly active terminal hydroxyl groups, but the atom economy is poor and the functionality is low, which greatly limits its downstream application; 3) Oxidizing vegetable oils to epoxidized vegetable oils, and then generating polyhydroxy compounds through reactions such as ring opening. This scheme has high atom economy and has the advantages of flexibility, structural controllability and molecular diversity, and has become the main method for developing bio-based polyols.

[0006] The long-chain groups in the vegetable oil structure replace the repeating units of traditional petrochemical polyol polyethers or polyesters. The triglyceride core in the structure has a star-shaped spatial conformation, which endows downstream polyurethanes with more functional properties and application potential. However, vegetable oil polyols often suffer from performance drawbacks, primarily due to the uncontrollable reaction process. During the functional group conversion process, multiple epoxy and ester groups often participate in multiple side reactions. This makes the designed molecular structure difficult to construct using traditional chemical methods, significantly limiting the quality of the polyol. Mixing with traditional petrochemical polyols is often necessary to achieve a certain application effect. Analysis of the reaction mechanism suggests that the main reason is that oil esters often have poor miscibility with the reaction reagents and low reactivity, resulting in long and intensive reactions. However, the influence of multiple functional groups in the structure makes it difficult to balance reaction selectivity and conversion rate, resulting in poor process control, resulting in poor molecular uniformity, high viscosity, and significant differences in macroscopic and microscopic indicators between individual molecules. Therefore, even though vegetable oil prices are often lower than those of the monomers containing petrochemical repeating units, it is difficult to obtain vegetable oil polyol products that have both cost and quality advantages. It is necessary to control product quality through chemical process control. In this reaction system, the use of micro-reaction technology to intensify the chemical reaction process and continuously and precisely control it is an effective solution.

[0007] Generally speaking, polyurethane products formed by polyester polyols are superior to those formed by polyether polyols in terms of mechanical strength. The possible reason is the potential effect of hydrogen bonds formed between the ester groups in the polyols and the ammonia in the isocyanate. Therefore, it is possible to consider the ring-opening reaction between epoxy vegetable oil and a ring-opening reagent with an ester group, and to adjust the hydroxyl value by adjusting the structure of the ring-opening reagent to give it a certain functionality. Of course, the increase in hydroxyl value helps to improve strength and hardness, but may lead to an increase in polyol viscosity and a decrease in toughness. In addition, previous studies have shown that if there are residual epoxy groups, it helps to improve corrosion resistance, but leads to a decrease in functionality. In summary, the adjustment of functionality in the structure, the proportion of residual epoxy groups, the number and spatial arrangement of ester groups, the hydroxyl value and the spatial arrangement of hydroxyl groups will all have a great impact on the results, and these parameters affect each other, but there is a lack of a complete structure-activity relationship, which is the main reason for the limited development of this field.

[0008] At present, since vegetable oil components are not single and the structure-activity relationship is unclear, the quality control of polyol products can only be carried out through reaction process control and macro-indicator regulation. Therefore, controlling product uniformity through process control as much as possible is important for the development of new polyol products and downstream applications. Summary of the Invention

[0009] In view of the deficiencies of the prior art, the present invention provides a method for preparing a bio-based polyol and its application.

[0010] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0011] In one aspect, the present invention provides a method for preparing a bio-based polyol, comprising the following steps:

[0012] Step 1: mixing epoxidized vegetable oil with a catalyst to obtain a first mixed solution, dissolving a first ring-opening reagent in an organic solvent to obtain a second mixed solution; and simultaneously pumping the first mixed solution and the second mixed solution into a first microreactor of a microchannel modular reaction device to perform a first ring-opening reaction to obtain a first reaction effluent.

[0013] Step 2: dissolving a second ring-opening reagent in an organic solvent to obtain a third mixed solution; simultaneously pumping the third mixed solution and the first reaction effluent into a second microreactor of a microchannel modular reaction device to perform a second ring-opening reaction to obtain a second reaction effluent; the first ring-opening reagent is at least one of dimethyl tartrate, diethyl tartrate, and diisopropyl tartrate; and the second ring-opening reagent is 1,2-propylene glycol;

[0014] Step 3: dissolving a third ring-opening reagent in an organic solvent to obtain a fourth mixed liquid; simultaneously pumping the fourth mixed liquid and the second reaction effluent into a third microreactor of the microchannel modular reaction device to perform a third ring-opening reaction to obtain a third reaction effluent; the third ring-opening reagent is at least one of methanol and ethanol;

[0015] Step 4: The third reaction effluent is concentrated to a certain volume, a certain volume of ethyl acetate is added, and the mixture is washed with a sodium bicarbonate solution and then water. The layers are separated, and the organic phase is dried, filtered, and concentrated to obtain a bio-based polyol.

[0016] Preferably, the epoxidized vegetable oil is at least 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.

[0017] Preferably, the organic solvent is at least one of ethyl acetate, dichloromethane, dichloroethane, chloroform, n-hexane, tetrahydrofuran, 1,4-dioxane, carbon tetrachloride, toluene, and xylene; and the catalyst is at least one of fluoroboric acid, phosphoric acid, phosphotungstic acid, and lipase CALB.

[0018] Preferably, the mass volume ratio (g / ml) of the first ring-opening reagent to the organic solvent is 1:0.5-2; the mass ratio of the epoxidized vegetable oil to the catalyst is 1:0.02-0.1; and the volume of the first microreactor in the epoxidized vegetable oil is 5-20 ml.

[0019] Preferably, in the first ring-opening reaction, the reaction temperature is 80-120° C., and the reaction time is 3-15 min.

[0020] Preferably, the molar ratio of the epoxy groups in the epoxidized vegetable oil to the second ring-opening reagent is 1:0.1-0.2; and the mass volume ratio (g / ml) of the second ring-opening reagent to the organic solvent is 1:1-4.

[0021] Preferably, in the second ring-opening reaction, the reaction temperature is 80-120° C., and the reaction time is 3-15 min.

[0022] Preferably, the molar ratio of the epoxy groups in the epoxidized vegetable oil to the third ring-opening reagent is 1:0.4-0.6; and the mass volume ratio (g / ml) of the third ring-opening reagent to the organic solvent is 1:4-8.

[0023] Preferably, in the third ring-opening reaction, the reaction temperature is 80-120° C., and the reaction time is 3-15 min.

[0024] Preferably, the microchannel modular reaction device includes a first feed pump, a second feed pump, a third feed pump, a fourth feed pump, a first micromixer, a second micromixer, a third micromixer, a microreaction pipe, a tubular temperature control module, a first microreactor, a second microreactor, a third 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 pipe; the first microreactor and the third feed pump are connected in parallel to the second micromixer, and the second micromixer and the second microreactor are connected through a microreaction pipe; the second microreactor and the fourth feed pump are connected in parallel to the third micromixer, and the third micromixer, the third microreactor and the receiver are connected in series through a microreaction pipe.

[0025] The first, second, and third micromixers are preferably slit plate mixers LH25. The first, second, and third microreactors are preferably Vapotech. The volumes of the first, second, and third microreactors are all 5-20 ml. The reaction temperatures of the first, second, and third microreactors are all controlled by heating in an oil bath.

[0026] On the other hand, the present invention also provides the use of the bio-based polyol prepared according to the preparation method in the preparation of polyurethane coatings.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] To improve the mechanical properties of polyester polyol downstream products, the present invention uses a tartaric acid ester as the first ring-opening reagent to carry out a first ring-opening reaction of epoxy groups, then uses a second ring-opening reagent containing a secondary alcohol to carry out a second ring-opening reaction, and finally uses a primary alcohol to carry out a third ring-opening reaction of the remaining epoxy groups, thereby obtaining a vegetable oil polyol product with an epoxy value close to zero. To avoid non-selective ring opening during the ring-opening reaction and the resulting cross-linking side reaction, the present invention utilizes micro-reaction technology and a microchannel modular reaction device as the reaction equipment to further control the ring-opening groups.

[0029] 2. The bio-based polyol prepared by the novel ring-opening reagent of the present invention contains an ester structure, which has a certain synergistic effect on the structural properties of the product. At the same time, the selected ring-opening reagent contains a secondary alcohol, which can improve the toughness of the bio-based polyol.

[0030] 3. 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 method of the present invention is significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0032] FIG1 is a flow chart of a method for preparing a bio-based polyol according to an embodiment of the present invention. DETAILED DESCRIPTION

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0034] The relevant determination methods of the prepared bio-based polyols and polyurethane coatings of the present invention are as follows:

[0035] (1) Measure the hydroxyl value according to GB / T 12008.3-2009;

[0036] (2) Measure viscosity according to GB / T 12008.7-2010;

[0037] (3) Determine the coating's drying time according to GB / T 1728-1979 (1989);

[0038] (4) Determine the pencil hardness of the coating according to GB / T 6739-2006;

[0039] (5) Determine the impact resistance of the coating according to GB / T 1732-1993;

[0040] (6) Determine the flexibility of the coating according to GB / T 1731-1993.

[0041] With reference to Figure 1, the microchannel reactions of the following embodiments and comparative examples are all realized based on a microchannel modular reaction device, which includes a first feed pump, a second feed pump, a third feed pump, a fourth feed pump, a first micromixer, a second micromixer, a third micromixer, a microreaction pipeline, a tubular temperature control module, a first microreactor, a second microreactor, a third 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 and the second microreactor are connected through a microreaction pipeline; the second microreactor and the fourth feed pump are connected in parallel to the third micromixer, and the third micromixer, the third microreactor and the receiver are connected in series through a microreaction pipeline.

[0042] The first, second, and third micromixers are all slit plate mixers LH25; the first, second, and third microreactors are all Vapotech models. The reaction temperatures of the first, second, and third microreactors are all controlled by oil bath heating. The first, second, third, and fourth feed pumps are all precise and low-pressure feed pumps. The first feed pump is responsible for pumping the first mixed liquid, the second feed pump is responsible for pumping the second mixed liquid, the third feed pump is responsible for pumping the third mixed liquid, and the fourth feed pump is responsible for pumping the fourth mixed liquid.

[0043] Example 1: Preparation of bio-based polyols:

[0044] Step 1: Mix 100g of epoxidized soybean oil (epoxy value 6.5%) and 0.2g of fluoroboric acid (20mg, 50%) to produce a first mixed solution. Mix 28.55g of diisopropyl tartrate and 29ml of 1,4-dioxane to produce a second mixed solution. Adjust the temperature of the first microreactor to 100°C, and simultaneously pump the first and second mixed solutions into the 10ml first microreactor at rates of 1ml / min and 0.56ml / min, respectively, to carry out a first ring-opening reaction, yielding a first reaction effluent.

[0045] Step 2: 4.64 g of 1,2-propylene glycol and 14 ml of 1,4-dioxane were mixed to obtain a third mixed solution. The temperature of the second microreactor was adjusted to 100° C. The third mixed solution and the first reaction effluent were simultaneously pumped into a 15 ml second microreactor at a rate of 0.18 ml / min to perform a second ring-opening reaction to obtain a second reaction effluent.

[0046] Step 3: 7.16 g of methanol and 29 ml of 1,4-dioxane were mixed to obtain a fourth mixed solution. The temperature of the third microreactor was adjusted to 100° C., and the fourth mixed solution and the second reaction effluent were simultaneously pumped into a 20 ml third microreactor at a rate of 0.35 ml / min to perform a third ring-opening reaction to obtain a third reaction effluent.

[0047] Step 4: After the reaction, the third reaction effluent was concentrated to 200 ml, 200 ml of ethyl acetate was added, and the mixture was washed with 50 ml of 5% sodium bicarbonate solution and then washed twice with water, adding 50 ml each time. The layers were separated, and the organic phase was dried, filtered, and concentrated to obtain a bio-based polyol with a hydroxyl value of 226 mg KOH / g and a viscosity of 796 mPa·s.

[0048] Preparation of bio-based polyurethane coating: Based on a molar ratio of NCO to OH functional groups of 1.25:1, the bio-based polyol obtained in this example was mixed with an isocyanate. A catalyst was added at a concentration of 3‰ of the polyol mass. The mixture was allowed to react for 2 hours to produce a prepolymer mixture. A hydrophilic chain extender was added to the prepolymer mixture and allowed to react for 3 hours to produce a polymer mixture. A neutralizing agent was added to neutralize the polymer mixture. A diluent was then added and emulsified at high shear to form a polyurethane emulsion. The polyurethane emulsion was sprayed onto a steel substrate. A single spray application resulted in a dry film thickness of 60 μm. The mixture was then allowed to stand for 168 hours in a laboratory environment before testing.

[0049] Example 2: Preparation of bio-based polyols:

[0050] Step 1: Mix 100g of epoxidized soybean oil (epoxy value 6%) and 0.2g of fluoroboric acid (20mg, 50%) to produce a first mixed solution. Mix 27.06g of diethyl tartrate and 27ml of 1,4-dioxane to produce a second mixed solution. Adjust the temperature of the first microreactor to 100°C. Pump the first and second mixed solutions simultaneously into the 10ml first microreactor at rates of 1ml / min and 0.53ml / min, respectively, to carry out a first ring-opening reaction, yielding a first reaction effluent.

[0051] Step 2: 4.28 g of 1,2-propylene glycol and 13 ml of 1,4-dioxane were mixed to obtain a third mixed solution. The temperature of the second microreactor was adjusted to 100° C. The third mixed solution and the first reaction effluent were simultaneously pumped into a 15 ml second microreactor at a rate of 0.17 ml / min to perform a second ring-opening reaction to obtain a second reaction effluent.

[0052] Step 3: 6.01 g of methanol and 24 ml of 1,4-dioxane were mixed to obtain a fourth mixed solution. The temperature of the third microreactor was adjusted to 100° C. The fourth mixed solution and the second reaction effluent were simultaneously pumped into a 20 ml third microreactor at a rate of 0.29 ml / min to perform a third ring-opening reaction to obtain a third reaction effluent.

[0053] Step 4: After the reaction, the third reaction effluent was concentrated to 200 ml, 200 ml of ethyl acetate was added, and the mixture was washed with 50 ml of 5% sodium bicarbonate solution and then washed twice with water, adding 50 ml each time. The layers were separated, and the organic phase was dried, filtered, and concentrated to obtain a bio-based polyol with a hydroxyl value of 217 mg KOH / g and a viscosity of 759 mPa·s.

[0054] Preparation of bio-based polyurethane coating: Based on a molar ratio of NCO to OH functional groups of 1.25:1.05, the bio-based polyol obtained in this example was mixed with an isocyanate. A catalyst was added at a concentration of 3‰ of the polyol mass. The mixture was allowed to react for 2 hours to produce a prepolymer mixture. A hydrophilic chain extender was added to the prepolymer mixture and allowed to react for 3 hours to produce a polymer mixture. A neutralizing agent was added to neutralize the polymer mixture. A diluent was then added and emulsified at high shear to form a polyurethane emulsion. The polyurethane emulsion was sprayed onto a steel substrate. A single spray application resulted in a dry film thickness of 80 μm. The mixture was then allowed to stand for 168 hours in a laboratory environment before testing.

[0055] Example 3: Preparation of bio-based polyols:

[0056] Step 1: Mix 100g of epoxidized soybean oil (epoxy value 6.5%) and 0.2g of fluoroboric acid (20mg, 50%) to produce a first mixed solution. Mix 24.61g of dimethyl tartrate and 25ml of 1,4-dioxane to produce a second mixed solution. Adjust the temperature of the first microreactor to 100°C, and simultaneously pump the first and second mixed solutions into the 10ml first microreactor at rates of 1ml / min and 0.48ml / min, respectively, to carry out a first ring-opening reaction, yielding a first reaction effluent.

[0057] Step 2: 4.95 g of 1,2-propylene glycol and 15 ml of 1,4-dioxane were mixed to obtain a third mixed solution. The temperature of the second microreactor was adjusted to 100° C. The third mixed solution and the first reaction effluent were simultaneously pumped into a 15 ml second microreactor at a rate of 0.19 ml / min to perform a second ring-opening reaction to obtain a second reaction effluent.

[0058] Step 3: 6.51 g of methanol and 26 ml of 1,4-dioxane were mixed to obtain a fourth mixed solution. The temperature of the third microreactor was adjusted to 100° C., and the fourth mixed solution and the second reaction effluent were simultaneously pumped into a 20 ml third microreactor at a rate of 0.31 ml / min to perform a third ring-opening reaction to obtain a third reaction effluent.

[0059] Step 4: After the reaction, the third reaction effluent was concentrated to 200 ml, 200 ml of ethyl acetate was added, and the mixture was washed with 50 ml of 5% sodium bicarbonate solution and then washed twice with water, adding 50 ml each time. The layers were separated, and the organic phase was dried, filtered, and concentrated to obtain a bio-based polyol with a hydroxyl value of 241 mg KOH / g and a viscosity of 864 mPa·s.

[0060] Preparation of bio-based polyurethane coating: Based on a molar ratio of NCO to OH functional groups of 1.25:1, the bio-based polyol obtained in this example was mixed with an isocyanate. A catalyst was added at a concentration of 3‰ of the polyol mass. The mixture was allowed to react for 2 hours to produce a prepolymer mixture. A hydrophilic chain extender was added to the prepolymer mixture and allowed to react for 3 hours to produce a polymer mixture. A neutralizing agent was added to neutralize the polymer mixture. A diluent was then added and emulsified at high shear to form a polyurethane emulsion. The polyurethane emulsion was sprayed onto a steel substrate. A single spray application resulted in a dry film thickness of 60 μm. The mixture was then allowed to stand for 168 hours in a laboratory environment before testing.

[0061] Example 4: Preparation of bio-based polyols:

[0062] Step 1: Mix 100g of epoxidized soybean oil (epoxy value 6%) and 0.2g of fluoroboric acid (20mg, 50%) to produce a first mixed solution. Mix 28.99g of diisopropyl tartrate and 29ml of 1,4-dioxane to produce a second mixed solution. Adjust the temperature of the first microreactor to 100°C, and simultaneously pump the first and second mixed solutions into the 10ml first microreactor at rates of 1ml / min and 0.57ml / min, respectively, to carry out a first ring-opening reaction, yielding a first reaction effluent.

[0063] Step 2: 4.85 g of 1,2-propylene glycol and 15 ml of 1,4-dioxane were mixed to obtain a third mixed solution. The temperature of the second microreactor was adjusted to 100° C. The third mixed solution and the first reaction effluent were simultaneously pumped into a 15 ml second microreactor at a rate of 0.19 ml / min to perform a second ring-opening reaction to obtain a second reaction effluent.

[0064] Step 3: 8.64 g of ethanol and 35 ml of 1,4-dioxane were mixed to obtain a fourth mixed solution. The temperature of the third microreactor was adjusted to 100° C., and the fourth mixed solution and the second reaction effluent were simultaneously pumped into a 20 ml third microreactor at a rate of 0.42 ml / min to perform a third ring-opening reaction to obtain a third reaction effluent.

[0065] Step 4: After the reaction, the third reaction effluent was concentrated to 200 ml, 200 ml of ethyl acetate was added, and the mixture was washed with 50 ml of 5% sodium bicarbonate solution and then washed twice with water, adding 50 ml each time. The layers were separated, and the organic phase was dried, filtered, and concentrated to obtain a bio-based polyol with a hydroxyl value of 203 mg KOH / g and a viscosity of 768 mPa·s.

[0066] Preparation of bio-based polyurethane coating: Based on a molar ratio of NCO to OH functional groups of 1.25:1, the bio-based polyol obtained in this example was mixed with an isocyanate. A catalyst was added at a concentration of 3‰ of the polyol mass. The mixture was allowed to react for 2 hours to produce a prepolymer mixture. A hydrophilic chain extender was added to the prepolymer mixture and allowed to react for 3 hours to produce a polymer mixture. A neutralizing agent was added to neutralize the polymer mixture. A diluent was then added and emulsified at high shear to form a polyurethane emulsion. The polyurethane emulsion was sprayed onto a steel substrate. A single spray application resulted in a dry film thickness of 60 μm. The mixture was then allowed to stand for 168 hours in a laboratory environment before testing.

[0067] Example 5: Preparation of bio-based polyols:

[0068] Step 1: Mix 100g of epoxidized soybean oil (epoxy value 6.5%) and 0.2g of fluoroboric acid (20mg, 50%) to produce a first mixed solution. Mix 33.51g of diisopropyl tartrate and 34ml of 1,4-dioxane to produce a second mixed solution. Adjust the temperature of the first microreactor to 100°C, and simultaneously pump the first and second mixed solutions into the 10ml first microreactor at rates of 1ml / min and 0.66ml / min, respectively, to carry out a first ring-opening reaction, yielding a first reaction effluent.

[0069] Step 2: 4.64 g of 1,2-propylene glycol and 14 ml of 1,4-dioxane were mixed to obtain a third mixed solution. The temperature of the second microreactor was adjusted to 100° C. The third mixed solution and the first reaction effluent were simultaneously pumped into a 15 ml second microreactor at a rate of 0.18 ml / min to perform a second ring-opening reaction to obtain a second reaction effluent.

[0070] Step 3: 8.42 g of ethanol and 34 ml of 1,4-dioxane were mixed to obtain a fourth mixed solution. The temperature of the third microreactor was adjusted to 100° C., and the fourth mixed solution and the second reaction effluent were simultaneously pumped into a 20 ml third microreactor at a rate of 0.41 ml / min to perform a third ring-opening reaction to obtain a third reaction effluent.

[0071] Step 4: After the reaction, the third reaction effluent was concentrated to 200 ml, 200 ml of ethyl acetate was added, and the mixture was washed with 50 ml of 5% sodium bicarbonate solution and then washed twice with water, adding 50 ml each time. The layers were separated, and the organic phase was dried, filtered, and concentrated to obtain a bio-based polyol with a hydroxyl value of 228 mg KOH / g and a viscosity of 807 mPa·s.

[0072] Preparation of bio-based polyurethane coating: Based on a molar ratio of NCO to OH functional groups of 1.25:1, the bio-based polyol obtained in this example was mixed with an isocyanate. A catalyst was added at a concentration of 3‰ of the polyol mass. The mixture was allowed to react for 2 hours to produce a prepolymer mixture. A hydrophilic chain extender was added to the prepolymer mixture and allowed to react for 3 hours to produce a polymer mixture. A neutralizing agent was added to neutralize the polymer mixture. A diluent was then added and emulsified at high shear to form a polyurethane emulsion. The polyurethane emulsion was sprayed onto a steel substrate. A single spray application resulted in a dry film thickness of 60 μm. The mixture was then allowed to stand for 168 hours in a laboratory environment before testing.

[0073] Example 6: Preparation of bio-based polyols:

[0074] Step 1: Mix 100g of epoxidized soybean oil (epoxy value 6%) and 0.2g of fluoroboric acid (20mg, 50%) to produce a first mixed solution. Mix 26.72g of dimethyl tartrate and 27ml of 1,4-dioxane to produce a second mixed solution. Adjust the temperature of the first microreactor to 100°C, and simultaneously pump the first and second mixed solutions into the 10ml first microreactor at rates of 1ml / min and 0.52ml / min, respectively, to carry out a first ring-opening reaction, yielding a first reaction effluent.

[0075] Step 2: 5.71 g of 1,2-propylene glycol and 17 ml of 1,4-dioxane were mixed to obtain a third mixed solution. The temperature of the second microreactor was adjusted to 100° C. The third mixed solution and the first reaction effluent were simultaneously pumped into a 15 ml second microreactor at a rate of 0.22 ml / min to perform a second ring-opening reaction to obtain a second reaction effluent.

[0076] Step 3: 6.91 g of ethanol and 28 ml of 1,4-dioxane were mixed to obtain a fourth mixed solution. The temperature of the third microreactor was adjusted to 100° C. The fourth mixed solution and the second reaction effluent were simultaneously pumped into a 20 ml third microreactor at a rate of 0.34 ml / min to perform a third ring-opening reaction to obtain a third reaction effluent.

[0077] Step 4: After the reaction, the third reaction effluent was concentrated to 200 ml, 200 ml of ethyl acetate was added, and the mixture was washed with 50 ml of 5% sodium bicarbonate solution and then washed twice with water, adding 50 ml each time. The layers were separated, and the organic phase was dried, filtered, and concentrated to obtain a bio-based polyol with a hydroxyl value of 229 mg KOH / g and a viscosity of 772 mPa·s.

[0078] Preparation of bio-based polyurethane coating: Based on a molar ratio of NCO to OH functional groups of 1.25:1, the bio-based polyol obtained in this example was mixed with an isocyanate. A catalyst was added at a concentration of 3‰ of the polyol mass. The mixture was allowed to react for 2 hours to produce a prepolymer mixture. A hydrophilic chain extender was added to the prepolymer mixture and allowed to react for 3 hours to produce a polymer mixture. A neutralizing agent was added to neutralize the polymer mixture. A diluent was then added and emulsified at high shear to form a polyurethane emulsion. The polyurethane emulsion was sprayed onto a steel substrate. A single spray application resulted in a dry film thickness of 60 μm. The mixture was then allowed to stand for 168 hours in a laboratory environment before testing.

[0079] Comparative Example 1: Preparation of bio-based polyols:

[0080] Step 1: Mix 100 g of epoxidized soybean oil (epoxy value 6.5%) and 0.2 g of fluoroboric acid (20 mg, 50%) to prepare a first mixed solution; mix 28.55 g of diisopropyl tartrate and 29 ml of 1,4-dioxane to prepare a second mixed solution; add the first and second mixed solutions to a reactor and perform a ring-opening reaction at 100°C for 2 hours;

[0081] Step 2: 10.82 g of 1,2-propylene glycol and 32 ml of 1,4-dioxane were mixed to obtain a third mixed solution, and the third mixed solution was added to the reactor to continue the ring-opening reaction at 100° C. for 2 h;

[0082] Step 3: 4.56 g of methanol and 18 ml of 1,4-dioxane were mixed to obtain a fourth mixed solution, and the fourth mixed solution was added to the reactor to continue the ring-opening reaction at 100° C. for 2 h;

[0083] Step 4: After the reaction, the reaction solution was concentrated to 200 ml, 200 ml of ethyl acetate was added, and the solution was washed with 50 ml of 5% sodium bicarbonate solution and then washed twice with water, adding 50 ml each time. The layers were separated, and the organic phase was dried, filtered, and concentrated to obtain a bio-based polyol with a hydroxyl value of 147 mg KOH / g and a viscosity of 1049 mPa·s.

[0084] Preparation of bio-based polyurethane coating: Based on a molar ratio of NCO to OH functional groups of 1.25:1, the bio-based polyol obtained in this comparative example was mixed with isocyanate. A catalyst was added at a concentration of 3‰ of the polyol mass and allowed to react for 2 hours to produce a prepolymer mixture. A hydrophilic chain extender was added to the prepolymer mixture and allowed to react for 3 hours to produce a polymer mixture. A neutralizing agent was added to neutralize the polymer mixture to a neutral state. A diluent was then added and emulsified at high shear to form a polyurethane emulsion. This polyurethane emulsion was sprayed onto a steel substrate, achieving a dry film thickness of 60 microns. The coating was then left in a laboratory for 168 hours before testing.

[0085] Comparative Example 2: Preparation of bio-based polyols:

[0086] Step 1: 100 g of epoxidized soybean oil (epoxy value 6%) and 0.2 g of fluoroboric acid (20 mg, 50%) were mixed to obtain a first mixed solution; 14.27 g of 1,2-propylene glycol and 14 ml of 1,4-dioxane were mixed to obtain a second mixed solution; the temperature of a first microreactor was adjusted to 100°C, and the first mixed solution and the second mixed solution were simultaneously pumped into the 10 ml first microreactor at rates of 1 ml / min and 0.28 ml / min, respectively, to carry out a first ring-opening reaction to obtain a first reaction effluent;

[0087] Step 2: 6.01 g of methanol and 18 ml of 1,4-dioxane were mixed to obtain a third mixed solution. The temperature of the second microreactor was adjusted to 100° C. The third mixed solution and the first reaction effluent were simultaneously pumped into a 15 ml second microreactor at a rate of 0.23 ml / min to perform a second ring-opening reaction to obtain a second reaction effluent.

[0088] Step 3: After the reaction, the second reaction effluent was concentrated to 200 ml, 200 ml of ethyl acetate was added, and the mixture was washed with 50 ml of 5% sodium bicarbonate solution and then washed twice with water, adding 50 ml each time. The layers were separated, and the organic phase was dried, filtered, and concentrated to produce a bio-based polyol with a hydroxyl value of 252 mg KOH / g and a viscosity of 652 mPa·s.

[0089] Preparation of bio-based polyurethane coating: Based on a molar ratio of NCO to OH functional groups of 1.25:1, the bio-based polyol obtained in this comparative example was mixed with isocyanate. A catalyst was added at a concentration of 3‰ of the polyol mass and allowed to react for 2 hours to produce a prepolymer mixture. A hydrophilic chain extender was added to the prepolymer mixture and allowed to react for 3 hours to produce a polymer mixture. A neutralizing agent was added to neutralize the polymer mixture to a neutral state. A diluent was then added and emulsified at high shear to form a polyurethane emulsion. This polyurethane emulsion was sprayed onto a steel substrate, achieving a dry film thickness of 60 microns. The coating was then left in a laboratory for 168 hours before testing.

[0090] Comparative Example 3: Preparation of bio-based polyols:

[0091] Step 1: 100 g of epoxidized soybean oil (epoxy value 6.5%) and 0.2 g of fluoroboric acid (20 mg, 50%) were mixed to obtain a first mixed solution; 47.58 g of diisopropyl tartrate and 48 ml of 1,4-dioxane were mixed to obtain a second mixed solution; the temperature of a first microreactor was adjusted to 100°C, and the first mixed solution and the second mixed solution were simultaneously pumped into the 10 ml first microreactor at rates of 1 ml / min and 0.93 ml / min, respectively, to carry out a first ring-opening reaction to obtain a first reaction effluent;

[0092] Step 2: 6.51 g of methanol and 20 ml of 1,4-dioxane were mixed to obtain a third mixed solution. The temperature of the second microreactor was adjusted to 100° C. The third mixed solution and the first reaction effluent were simultaneously pumped into a 15 ml second microreactor at a rate of 0.26 ml / min to perform a second ring-opening reaction to obtain a second reaction effluent.

[0093] Step 3: After the reaction, the second reaction effluent was concentrated to 200 ml, 200 ml of ethyl acetate was added, and the mixture was washed with 50 ml of 5% sodium bicarbonate solution and then washed twice with water, adding 50 ml each time. The layers were separated, and the organic phase was dried, filtered, and concentrated to produce a bio-based polyol with a hydroxyl value of 213 mg KOH / g and a viscosity of 825 mPa·s.

[0094] Preparation of bio-based polyurethane coating: Based on a molar ratio of NCO to OH functional groups of 1.25:1, the bio-based polyol obtained in this comparative example was mixed with isocyanate. A catalyst was added at a concentration of 3‰ of the polyol mass and allowed to react for 2 hours to produce a prepolymer mixture. A hydrophilic chain extender was added to the prepolymer mixture and allowed to react for 3 hours to produce a polymer mixture. A neutralizing agent was added to neutralize the polymer mixture to a neutral state. A diluent was then added and emulsified at high shear to form a polyurethane emulsion. This polyurethane emulsion was sprayed onto a steel substrate, achieving a dry film thickness of 60 microns. The coating was then left in a laboratory for 168 hours before testing.

[0095] Comparative Example 4: Preparation of bio-based polyols:

[0096] Step 1: 100 g of epoxidized soybean oil (epoxy value 6%) and 0.2 g of fluoroboric acid (20 mg, 50%) were mixed to obtain a first mixed solution; 43.92 g of diisopropyl tartrate and 44 ml of 1,4-dioxane were mixed to obtain a second mixed solution; the temperature of the first microreactor was adjusted to 100°C, and the first mixed solution and the second mixed solution were simultaneously pumped into the 10 ml first microreactor at rates of 1 ml / min and 0.86 ml / min, respectively, to carry out a first ring-opening reaction to obtain a first reaction effluent;

[0097] Step 2: 14.27 g of 1,2-propylene glycol and 43 ml of 1,4-dioxane were mixed to obtain a third mixed solution. The temperature of the second microreactor was adjusted to 100° C. The third mixed solution and the first reaction effluent were simultaneously pumped into a 15 ml second microreactor at a rate of 0.55 ml / min to perform a second ring-opening reaction to obtain a second reaction effluent.

[0098] Step 3: After the reaction, the second reaction effluent was concentrated to 200 ml, 200 ml of ethyl acetate was added, and the mixture was washed with 50 ml of 5% sodium bicarbonate solution and then washed twice with water, adding 50 ml each time. The layers were separated, and the organic phase was dried, filtered, and concentrated to produce a bio-based polyol with a hydroxyl value of 249 mg KOH / g and a viscosity of 727 mPa·s.

[0099] Preparation of bio-based polyurethane coating: Based on a molar ratio of NCO to OH functional groups of 1.25:1, the bio-based polyol obtained in this comparative example was mixed with isocyanate. A catalyst was added at a concentration of 3‰ of the polyol mass and allowed to react for 2 hours to produce a prepolymer mixture. A hydrophilic chain extender was added to the prepolymer mixture and allowed to react for 3 hours to produce a polymer mixture. A neutralizing agent was added to neutralize the polymer mixture to a neutral state. A diluent was then added and emulsified at high shear to form a polyurethane emulsion. This polyurethane emulsion was sprayed onto a steel substrate, achieving a dry film thickness of 60 microns. The coating was then left in a laboratory for 168 hours before testing.

[0100] The performance indicators of the bio-based polyols prepared in Examples 1-6 and Comparative Examples 1-4 are shown in Table 1, and the performance indicators of the bio-based polyurethane coatings prepared are shown in Table 2.

[0101] Table 1 Performance indicators of bio-based polyols prepared in Examples 1-6 and Comparative Examples 1-4

[0102]

[0103] Table 2 Performance indicators of bio-based polyurethane coatings prepared in Examples 1-6 and Comparative Examples 1-4

[0104]

[0105] From the data in Tables 1 and 2, it can be seen that the bio-based polyols prepared in conventional reactors have low hydroxyl values, severe attenuation, and more cross-linking side reactions, which lead to an increase in molecular weight, high viscosity of the bio-based polyols, and uncontrollable reactions in the reactor.

[0106] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A preparation method of a bio-based polyol, characterized in that, Comprising the following steps Step 1: Mix epoxy vegetable oil with a catalyst to obtain a first mixed solution, and dissolve a first ring-opening reagent in an organic solvent to obtain a second mixed solution; simultaneously pump the first mixed solution and the second mixed solution into a first microreactor of a microchannel modular reaction device respectively to carry out a first ring-opening reaction to obtain a first reaction effluent; the first ring-opening reagent is at least one of dimethyl tartrate, diethyl tartrate, and diisopropyl tartrate; Step 2: Dissolve a second ring-opening reagent in an organic solvent to obtain a third mixed solution; simultaneously pump the third mixed solution and the first reaction effluent into a second microreactor of the microchannel modular reaction device respectively to carry out a second ring-opening reaction to obtain a second reaction effluent; the second ring-opening reagent is 1,2-propanediol; Step 3: Dissolve a third ring-opening reagent in an organic solvent to obtain a fourth mixed solution; simultaneously pump the fourth mixed solution and the second reaction effluent into a third microreactor of the microchannel modular reaction device respectively to carry out a third ring-opening reaction to obtain a third reaction effluent; the third ring-opening reagent is at least one of methanol and ethanol; Step 4: Concentrate the third reaction effluent to a certain volume, add a certain volume of ethyl acetate, wash successively with sodium bicarbonate solution and water, separate the layers, dry, filter by suction, and concentrate the organic phase to obtain a bio-based polyol.

2. The preparation method according to claim 1, characterized in that, The epoxy vegetable oil is at least one 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 oil.

3. The preparation method according to claim 1 or 2, characterized in that, The organic solvent is at least one of ethyl acetate, dichloromethane, dichloroethane, chloroform, n-hexane, tetrahydrofuran, 1,4-dioxane, carbon tetrachloride, toluene, and xylene; the catalyst is at least one of fluoboric acid, phosphoric acid, phosphotungstic acid, and lipase CALB.

4. The preparation method according to claim 1 or 2, characterized in that, The mass-volume ratio (g / ml) of the first ring-opening reagent to the organic solvent is 1:0.5 - 2; the mass ratio of the epoxy vegetable oil to the catalyst is 1:0.02 - 0.1; the molar ratio of the epoxy group in the epoxy vegetable oil to the first ring-opening reagent is 1:0.3 - 0.

4.

5. The preparation method according to claim 1 or 2, characterized in that, In the first ring-opening reaction, the reaction temperature is 80 - 120°C, and the reaction time is 3 - 15 min.

6. The preparation method according to claim 1 or 2, characterized in that, The molar ratio of the epoxy group in the epoxy vegetable oil to the second ring-opening reagent is 1:0.1 - 0.2; the mass-volume ratio (g / ml) of the second ring-opening reagent to the organic solvent is 1:1 - 4.

7. The preparation method according to claim 1 or 2, characterized in that, In the second ring-opening reaction, the reaction temperature is 80 - 120°C, and the reaction time is 3 - 15 min.

8. The preparation method according to claim 1 or 2, characterized in that, The molar ratio of the epoxy group in the epoxy vegetable oil to the third ring-opening reagent is 1:0.4 - 0.6; the mass-volume ratio (g / ml) of the third ring-opening reagent to the organic solvent is 1:4 - 8.

9. The preparation method according to claim 1 or 2, characterized in that In the third ring-opening reaction, the reaction temperature is 80 - 120°C, and the reaction time is 3 - 15 min.

10. Use of the bio-based polyol prepared by the preparation method according to any one of claims 1 - 9 in the preparation of polyurethane coatings.

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