A method for synthesizing polyols based on natural vegetable oils and derivatives thereof

Abstract

The application discloses a method for synthesizing polyols based on natural plant oil and derivatives thereof, which is characterized by the following steps: taking plant oil or plant oil derivatives as oil raw materials, taking high-functionality hydroxyl compounds with a functionality of 6-8 and low-functionality hydroxyl compounds with a functionality of 2-3 as initiators, taking alkylene oxide as a monomer, taking DMC as a catalyst, and taking Fe3O4@mSiO2@STA as an acidic additive; and under the action of the catalyst and the acidic additive, the oil raw materials, the initiators and the monomer are subjected to ring-opening polymerization in water to obtain polyols based on plant oil and derivatives thereof. The method provided by the application is not only convenient in post-treatment and friendly to the environment, but also has a good synergistic effect between Fe3O4@mSiO2@STA and DMC, effectively avoids the deactivation of DMC, and makes the prepared polyols have better performance and be more suitable for preparing polyurethane products with excellent comprehensive performance, thus having extremely strong industrial application value.

Description

Technical Field

[0001] This invention relates to a method for synthesizing polyols based on natural plant oils and their derivatives, belonging to the field of plant oil-based polyol synthesis technology. Background Technology

[0002] Vegetable oils possess excellent physical and chemical properties, and are renewable, inexpensive, and abundant, making them widely used in the preparation of polyols. Vegetable oil-based polyols are chemical intermediates prepared from vegetable oils through chemical or biological modification. With the increasing scarcity of petroleum resources and growing environmental awareness, vegetable oil-based polyols are currently frequently used to replace traditional petroleum-based polyols in the preparation of lubricants, adhesives, resins, plastics, surfactants, and especially polyurethane products.

[0003] The epoxy ring-opening method is the most common method for preparing vegetable oil-based polyols. Its principle involves epoxidizing vegetable oil to produce vegetable oil-based polyols through ring-opening and hydroxylation reactions under the action of a catalyst and a ring-opening agent. Commonly used catalysts include inorganic acids (such as concentrated sulfuric acid, hydrochloric acid, perchloric acid, and fluoroboric acid) and organic acids (such as p-toluenesulfonic acid). Commonly used ring-opening agents include water, fatty alcohols (such as methanol and ethanol), fatty acids (such as formic acid and acetic acid), and alkanolamines. However, the epoxy ring-opening method also has certain drawbacks. For example, the acidic catalysts used during the reaction can easily corrode equipment, making separation difficult and generating acidic wastewater, causing environmental pollution.

[0004] Bimetallic cyanide complex catalysts (DMCs) are highly active catalysts for catalyzing the ring-opening of epoxides, and are widely used in the synthesis of low-unsaturation, high-molecular-weight polyether polyols due to their advantages such as high catalytic activity, low dosage, and simple post-processing. Therefore, using DMC as a catalyst represents a promising new direction for the synthesis of plant oil-based polyols. However, the application of DMC catalysts requires acidic conditions and a certain induction period. During the preparation of polyether polyols, DMC is highly susceptible to the influence of alkaline impurities, gradually deactivating and prolonging the induction period. This results in polyether products with high viscosity and alkalinity, or even complete deactivation of DMC, preventing further catalytic reaction. Currently, strong acids such as phosphoric acid and sulfuric acid are typically added to the reaction system as acidic auxiliaries to enable DMC to catalyze the reaction under acidic conditions. However, traditional acidic auxiliaries such as phosphoric acid have drawbacks such as strong corrosivity, inconvenient post-processing, environmental unfriendliness, and a tendency to cause side reactions. Therefore, it is necessary to develop a method for synthesizing polyols based on natural plant oils and their derivatives, using DMC as a catalyst without catalyst deactivation during the preparation process. Summary of the Invention

[0005] To address the aforementioned problems in the existing technology, the purpose of this invention is to provide a method for synthesizing polyols based on natural plant oils and their derivatives.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for synthesizing polyols based on natural plant oils and their derivatives involves using plant oils or plant oil derivatives as raw materials, high-functionality hydroxyl compounds with a functionality of 6-8 and low-functionality hydroxyl compounds with a functionality of 2-3 as initiators, epoxides as monomers, DMC as a catalyst, and Fe3O4@mSiO2@STA as an acidic auxiliary. The raw materials, initiators, and monomers undergo a ring-opening polymerization reaction in water under the action of the catalyst and the acidic auxiliary to obtain polyols based on plant oils and their derivatives.

[0008] The Fe3O4@mSiO2@STA is obtained by first coating a mesoporous silica shell on the surface of Fe3O4 to obtain Fe3O4@mSiO2, and then loading silicotungstic acid on the surface of Fe3O4@mSiO2.

[0009] One implementation scheme is as follows: the vegetable oil is selected from any one of palm oil, soybean oil, castor oil, rapeseed oil, cottonseed oil, sunflower seed oil, flaxseed oil, and cashew oil; the vegetable oil derivative is any one of hydroxylated vegetable oil and hydrogenated vegetable oil.

[0010] In one embodiment, the high-functionality hydroxyl compound is selected from one or more of sucrose, sorbitol, and mannitol; the low-functionality hydroxyl compound is selected from one or more of diethylene glycol, propylene glycol, dipropylene glycol, and glycerol.

[0011] In one embodiment, the epoxide is one or more of ethylene oxide, propylene oxide, and butane oxide.

[0012] In one embodiment, the mass ratio of oil feedstock: high-functionality hydroxyl compound: low-functionality hydroxyl compound: epoxide alkane: catalyst: auxiliary agent is (150-450): (20-150): (10-50): (300-500): (0.03-0.05): (0.05-0.5).

[0013] One embodiment of the preparation of Fe3O4@mSiO2@STA includes the following steps:

[0014] 1) Under nitrogen protection, ferric chloride hexahydrate and ferrous chloride tetrahydrate were dissolved in water, heated to 55-65℃, ammonia was added to adjust the pH to be greater than 12, and the reaction was kept at the temperature and stirred for 20-40 minutes. Sodium citrate was added, and the reaction was kept at the temperature and stirred for 1-2 hours. The reaction was then stopped, magnetically separated, washed, and dried to obtain Fe3O4 powder.

[0015] 2) Fe3O4 powder was uniformly dispersed in anhydrous ethanol to obtain Fe3O4 ethanol sol; tetraethyl orthosilicate was dispersed in ethanol to obtain tetraethyl orthosilicate ethanol solution; hexadecyltrimethylammonium bromide and sodium citrate were dissolved in an aqueous ethanol solution, and then Fe3O4 ethanol sol was added and stirred to mix evenly. Then ammonia water was added and stirred to mix evenly. Then tetraethyl orthosilicate ethanol solution was added and the reaction was stirred at room temperature for 5-7 hours. The reaction was then stopped, magnetic separation was performed, and the powder was washed and dried to obtain Fe3O4@mSiO2 powder.

[0016] 3) Disperse silicotungstic acid in ethanol to obtain a silicotungstic acid ethanol solution. Impregnate Fe3O4@mSiO2 powder in the silicotungstic acid ethanol solution and ultrasonically disperse for 20-40 minutes. Rotary evaporate the resulting mixture until the solvent is completely evaporated. Place the solid obtained by evaporation in a muffle furnace for calcination and cool to room temperature to obtain Fe3O4@mSiO2@STA.

[0017] In a preferred embodiment, in step 1), the molar ratio of ferrous chloride tetrahydrate: ferric chloride hexahydrate: sodium citrate is 1:2:(0.2-0.5).

[0018] In a preferred embodiment, in step 2), the molar ratio of Fe3O4: cetyltrimethylammonium bromide: sodium citrate: tetraethyl orthosilicate is 1:(2-10):(1-3):(15-35).

[0019] In a preferred embodiment, in step 3), the mass ratio of Fe3O4@mSiO2 to silicotungstic acid is (1-4):1; the calcination temperature is 140-160℃, and the calcination time is 2-4 hours.

[0020] One embodiment of the preparation of polyols based on vegetable oils and their derivatives includes the following steps:

[0021] a) Stir the oil feedstock, high-functionality hydroxyl compound, and low-functionality hydroxyl compound at 80-100℃ for 1-3 hours to form a homogeneous mixture. Dehydrate the resulting mixture under vacuum at 110-120℃ for 1-3 hours until the water content of the system is ≤0.03%.

[0022] b) After dehydration, stop the vacuum, cool down to below 100℃, add acidic additives and catalyst, stir and mix evenly, then heat to 130-140℃, and quickly add some epoxy alkane under stirring to induce the reaction. After successful induction, continuously add the remaining epoxy alkane. During the feeding process, maintain the temperature at 130-140℃ and the pressure ≤ 0.5 MPa. After the feeding is completed, keep the reaction at the temperature for 1-3 hours.

[0023] c) After the reaction is complete, cool down to below 90°C, degas under vacuum for 1-2 hours, cool the product down to below 60°C, and perform magnetic separation to recover the acidic additives. Decolorize and filter the crude polyol obtained from the separation to obtain polyols based on vegetable oils and their derivatives.

[0024] Compared with the prior art, the present invention has the following significant advantages:

[0025] This invention uses vegetable oil or vegetable oil derivatives as raw materials, high-functionality hydroxyl compounds with a functionality of 6-8 and low-functionality hydroxyl compounds with a functionality of 2-3 as initiators, epoxides as monomers, DMC as a catalyst, and Fe3O4@mSiO2@STA as an acidic auxiliary. The raw materials, initiators, and monomers undergo ring-opening polymerization in water under the action of the catalyst and acidic auxiliary to obtain polyols based on vegetable oils and their derivatives. This process is not only convenient and environmentally friendly, but also exhibits a good synergistic effect between Fe3O4@mSiO2@STA and DMC, effectively avoiding DMC deactivation while resulting in better performance of the prepared polyols. These polyols are more suitable for preparing polyurethane products with excellent comprehensive properties such as mechanical properties, thermal stability, and appearance, and have strong industrial application value. Detailed Implementation

[0026] The technical solution of the present invention will be further described in detail and completely below with reference to the embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or as recommended by the manufacturer.

[0027] Example 1

[0028] I. Preparation of acidic additive Fe3O4@mSiO2@STA

[0029] 1) Under nitrogen protection, 2.70 g of ferric chloride hexahydrate and 1.00 g of ferrous chloride tetrahydrate were dissolved in 80 mL of water. The temperature was raised to 60 °C, and 10 mL of ammonia solution with a concentration of approximately 25-28 wt% was added to adjust the pH to greater than 12. The mixture was kept at this temperature and stirred for 30 minutes. Then, 0.5 g of sodium citrate was added, and the mixture was kept at this temperature and stirred for another hour. The reaction was then stopped, and the solid was magnetically separated. The obtained solid was washed with deionized water and ethanol alternately 3-5 times until the washing solution was neutral. The solid was then vacuum dried (at 60 °C overnight) to obtain Fe3O4 powder.

[0030] 2) The obtained Fe3O4 powder (approximately 1.0 g) was uniformly dispersed in 80 mL of anhydrous ethanol to obtain Fe3O4 ethanol sol; 2.0 mL of tetraethyl orthosilicate (a silicon source used for hydrolysis and polycondensation to form a silica shell) was dispersed in 10 mL of ethanol to obtain tetraethyl orthosilicate ethanol solution; 0.5 g Hexadecyltrimethylammonium bromide (a mesoporous template and dispersant stabilizer used to form micelles, guiding the condensation of silica on its surface to form a mesoporous structure, and acting as a cationic surfactant, it can adsorb onto the surface of Fe3O4 particles, helping Fe3O4 particles to be stably dispersed in the reaction system) and 0.28 g of sodium citrate (a co-surfactant and dispersant that helps hexadecyltrimethylammonium bromide better disperse Fe3O4 particles and adjusts the morphology of hexadecyltrimethylammonium bromide micelles, making them tightly and orderly adsorbed on the surface of Fe3O4 particles) were dissolved in an ethanol aqueous solution (40 mL deionized water + 120 mL ethanol). Then, Fe3O4 ethanol sol was added and stirred to mix evenly. Then, 2 mL of ammonia water (to provide an alkaline environment to catalyze the hydrolysis and polycondensation of tetraethyl orthosilicate) was added and stirred to mix evenly. Then, tetraethyl orthosilicate ethanol solution was added and the reaction was stirred at room temperature for 6 hours. The reaction was then stopped, and the solid was magnetically separated. The obtained solid was washed three times with deionized water and ethanol, and then vacuum dried to obtain Fe3O4@mSiO2 powder.

[0031] 3) Disperse 0.33g of silicotungstic acid in 15mL of ethanol to obtain a silicotungstic acid ethanol solution. Immerse 1g of Fe3O4@mSiO2 powder in the silicotungstic acid ethanol solution and ultrasonically disperse for 30 minutes. Slowly rotary evaporate the resulting mixture at 40℃ until the solvent is completely evaporated. Place the evaporated solid in a muffle furnace and heat it to 150℃ at a rate of 2℃ / min under an air atmosphere. Calcine at this temperature for 3 hours (to remove the mesoporous template agent hexadecyltrimethylammonium bromide, and simultaneously activate STA and firmly fix it in the mesoporous channels). Allow it to cool naturally to room temperature to obtain Fe3O4@mSiO2@STA.

[0032] II. Preparation of Polyols Based on Hydrogenated Castor Oil

[0033] a) 200g of hydrogenated castor oil (Jiangsu Qiangsheng Functional Chemical Co., Ltd.), 100g of sorbitol and 15g of propylene glycol were stirred at 85℃ for 1 hour to form a homogeneous mixture. The resulting mixture was then dehydrated under vacuum (approximately -0.095MPa) at 115℃ for 1.5 hours until the water content of the system was ≤0.03%.

[0034] b) After dehydration, stop the vacuum (use nitrogen to restore the pressure to a slight positive pressure of about 0.05 MPa), cool down to below 100℃, add 200 mg of acidic additive Fe3O4@mSiO2@STA and 40 mg of catalyst DMC (Jiangsu Bade Polyurethane Co., Ltd.), stir and mix evenly, then heat to 135℃, and quickly add 74 g of propylene oxide while stirring to induce the reaction. At this time, start monitoring the reaction status. When the temperature rises sharply (>5℃) and the pressure drops sharply (>0.1 MPa), it means that the induction is successful. After successful induction, continuously add the remaining 296 g of propylene oxide. During the feeding process, maintain the temperature at 135℃ and the pressure ≤0.3 MPa. The feeding time is about 2 hours. After the feeding is completed, keep the reaction at the temperature for 1.5 hours.

[0035] c) After the reaction is complete, the temperature is lowered to below 90°C and vacuum degassed for 1 hour. The product is then cooled to below 60°C and magnetically separated to recover the acidic additives. The crude polyol obtained is first decolorized and impurities adsorbed by passing it through a neutral alumina column, and then filtered through a 5μm filter bag to obtain a polyol based on hydrogenated castor oil.

[0036] Example 2

[0037] I. Preparation of acidic additive Fe3O4@mSiO2@STA

[0038] Same as Example 1

[0039] II. Preparation of polyols based on castor oil

[0040] a) Stir 300g castor oil (Jiangsu Qiangsheng Functional Chemical Co., Ltd.), 100g sucrose and 40g diethylene glycol at 95℃ for 2.5 hours to form a homogeneous mixture. Dehydrate the resulting mixture under vacuum (approximately -0.095MPa) at 115℃ for 2.5 hours until the water content of the system is ≤0.02%.

[0041] b) After dehydration, stop the vacuum (use nitrogen to restore the pressure to a slight positive pressure of about 0.05 MPa), quickly cool down to below 95°C, add 250 mg of acidic additive Fe3O4@mSiO2@STA and 45 mg of catalyst DMC (Jiangsu Bade Polyurethane Co., Ltd.), stir and mix evenly, then heat to 130°C, and quickly add 92 g of propylene oxide while stirring to induce the reaction. At this time, start monitoring the reaction status. When the temperature rises sharply (>5°C) and the pressure drops sharply (>0.1 MPa), it means that the induction is successful. After successful induction, continuously add the remaining 368 g of propylene oxide. During the feeding process, maintain the temperature at 130°C and the pressure ≤0.3 MPa. The feeding time is about 3 hours. After the feeding is completed, keep the reaction at the temperature for 1.5 hours.

[0042] c) After the reaction is complete, the temperature is lowered to below 85°C and vacuum degassed for 1.5 hours. The product is then cooled to below 60°C and magnetically separated to recover the acidic additives. The crude polyol obtained is first decolorized and impurities adsorbed by passing it through a neutral alumina column, and then filtered through a 5μm filter bag to obtain castor oil-based polyols.

[0043] Example 3

[0044] I. Preparation of acidic additive Fe3O4@mSiO2@STA

[0045] Same as Example 1

[0046] II. Preparation of Polyols Based on Hydroxylated Palm Oil

[0047] a) 250g of hydroxylated palm oil (Steppen Chemical (Nanjing) Co., Ltd.), 60g of sorbitol, 40g of sucrose, 25g of diethylene glycol and 15g of propylene glycol were stirred at 95°C for 2.5 hours to form a homogeneous mixture. The resulting mixture was then dehydrated under vacuum (approximately -0.095MPa) at 115°C for 2.5 hours until the water content of the system was ≤0.02%.

[0048] b) After dehydration, stop the vacuum (restore the pressure to a slight positive pressure of about 0.05 MPa using nitrogen), quickly cool down to below 100℃, add 300 mg of acidic additive Fe3O4@mSiO2@STA and 45 mg of catalyst DMC (Jiangsu Bade Polyurethane Co., Ltd.), stir and mix evenly, then heat to 135℃, and quickly add 86 g of propylene oxide while stirring to induce the reaction. At this time, start monitoring the reaction status. When the temperature rises sharply (>5℃) and the pressure drops sharply (>0.1 MPa), it means that the induction is successful. After successful induction, continuously add the remaining 344 g of propylene oxide, maintaining the temperature at 135℃ and the pressure ≤0.3 MPa during the feeding process. The feeding time is about 2.5 hours. After the feeding is completed, keep the reaction at the temperature for 1.5 hours.

[0049] c) After the reaction is complete, the temperature is lowered to below 90°C and vacuum degassed for 1.5 hours. The product is then cooled to below 60°C and magnetically separated to recover the acidic additives. The crude polyol obtained is first decolorized and impurities adsorbed by passing it through a neutral alumina column, and then filtered through a 5μm filter bag to obtain polyols based on hydroxylated palm oil.

[0050] Comparative Example 1

[0051] The difference between this comparative example and Example 1 is that the acidic auxiliary agent used in the preparation of the polyol is phosphoric acid. The specific preparation method of the polyol is as follows:

[0052] a) Same as Example 1;

[0053] b) After dehydration, stop the vacuum (use nitrogen to restore the pressure to a slight positive pressure of about 0.05 MPa), cool down to below 100℃, add 50 mg of 85% phosphoric acid, stir and mix evenly, then add 40 mg of catalyst DMC (Jiangsu Bade Polyurethane Co., Ltd.), stir and mix evenly, then heat up to 135℃, and quickly add 74 g of propylene oxide while stirring to induce the reaction. At this time, start monitoring the reaction status. When the temperature rises sharply (>5℃) and the pressure drops sharply (>0.1 MPa), it means that the induction is successful. After successful induction, continuously add the remaining 296 g of propylene oxide. During the feeding process, maintain the temperature at 135℃ and the pressure ≤0.3 MPa. The feeding time is about 2 hours. After the feeding is completed, keep the reaction at the temperature for 1.5 hours.

[0054] c) After the reaction is complete, the temperature is lowered to below 90°C, and the product is degassed under vacuum for 1 hour. The product is then cooled to below 60°C, and an alkaline adsorbent (powdered calcium carbonate) is added. The mixture is stirred for 1 hour to neutralize and adsorb the residual phosphoric acid. The adsorbent is removed by filtration. The crude polyol obtained by filtration is first decolorized and impurities are adsorbed by passing it through a neutral alumina column, and then filtered through a 5μm filter bag to obtain a polyol based on hydrogenated castor oil.

[0055] Comparative Example 2

[0056] The difference between this comparative example and Example 1 is that sulfuric acid is used as the acidic auxiliary agent in the preparation of the polyol. The specific preparation method of the polyol is as follows:

[0057] a) Same as Example 1;

[0058] b) After dehydration, stop the vacuum (use nitrogen to restore the pressure to a slight positive pressure of about 0.05 MPa), cool down to below 60°C, slowly add 50 mg of 98% sulfuric acid, stir to mix evenly, then add 40 mg of catalyst DMC (Jiangsu Bade Polyurethane Co., Ltd.), stir to mix evenly, then heat to 135°C, and quickly add 74 g of propylene oxide while stirring to induce the reaction. At this time, start monitoring the reaction status. When the temperature rises sharply (>5°C) and the pressure drops sharply (>0.1 MPa), it means that the induction is successful. After successful induction, continuously add the remaining 296 g of propylene oxide, maintaining the temperature at 135°C and the pressure ≤0.3 MPa during the feeding process. The feeding time is about 2 hours. After the feeding is completed, keep the reaction at the temperature for 1.5 hours.

[0059] c) After the reaction is complete, cool to below 90°C and degas under vacuum for 1 hour. Cool the resulting product to below 60°C and slowly add 5% sodium hydroxide aqueous solution while stirring until the pH of the system reaches 6-7. Wash the neutralized mixture with water 3-5 times. Dehydrate and dry the washed organic phase at 90-100°C under high vacuum (<-0.095 MPa) for 2-3 hours. After dehydration, cool the material to below 60°C and filter it through a 5μm filter bag to obtain a polyol based on hydrogenated castor oil.

[0060] Comparative Example 3

[0061] The difference between this comparative example and Example 1 is that the acidic auxiliary agent used in the preparation of the polyol is p-toluenesulfonic acid. The specific preparation method of the polyol is as follows:

[0062] a) Same as Example 1;

[0063] b) After dehydration, stop the vacuum (use nitrogen to restore the pressure to a slight positive pressure of about 0.05 MPa), cool down to below 100℃, add 50 mg of p-toluenesulfonic acid and 40 mg of catalyst DMC (Jiangsu Bade Polyurethane Co., Ltd.), stir and mix evenly, then heat to 135℃, and quickly add 74 g of propylene oxide while stirring to induce the reaction. At this time, start monitoring the reaction status. When the temperature rises sharply (>5℃) and the pressure drops sharply (>0.1 MPa), it means that the induction is successful. After successful induction, continuously add the remaining 296 g of propylene oxide. During the feeding process, maintain the temperature at 135℃ and the pressure ≤0.3 MPa. The feeding time is about 2 hours. After the feeding is completed, keep the reaction at the temperature for 1.5 hours.

[0064] c) After the reaction is complete, cool to below 90°C and degas under vacuum for 1 hour. Cool the resulting product to below 60°C and slowly add 5% sodium hydroxide aqueous solution under stirring until the pH of the system reaches 6-7. Wash the neutralized mixture with water 3-5 times. Decolorize and adsorb impurities by passing the washed organic phase through a neutral alumina column. Then dehydrate and dry under high vacuum at 90-100°C for 2-3 hours. Finally, filter through a 5μm filter bag to obtain a polyol based on hydrogenated castor oil.

[0065] Performance testing

[0066] The polyols prepared in Example 1 and Comparative Examples 1-3 were used to prepare polyurethane. Specifically, the polyols prepared in Example 1 and Comparative Examples 1-3 were dehydrated at 110°C under vacuum (-0.095 MPa) for 2 hours to ensure a moisture content of <0.03%. Then, under dry nitrogen protection, 100 parts by weight of the polyol were added to a reactor, the temperature was raised to 80°C, and 48 parts by weight of diphenylmethane diisocyanate were slowly added while stirring. The reaction was maintained at this temperature for 2 hours to obtain an isocyanate-terminated prepolymer. The temperature was lowered to 75°C, and 12 parts by weight of 1,4-butanediol, 0.05 parts by weight of stannous octoate, and 0.5 parts by weight of antioxidant 1010 were added while stirring at high speed. The mixture was stirred for 60 minutes to ensure thorough mixing. The resulting mixture was poured into a preheated (100°C) polytetrafluoroethylene mold. The mold was placed in a 100°C oven for 2 hours to cure, and then cured at room temperature to obtain polyurethane.

[0067] The tensile strength, elongation at break, stress at 100% elongation, and tear strength of the prepared polyurethane were tested according to GB / T528-2009. The glass transition temperature of the prepared polyurethane was tested using the DMA method. The 5% thermal weight loss temperature of the prepared polyurethane was tested using the TGA method. The color of the prepared polyurethane was tested using the platinum-cobalt colorimetric method. The test results are shown in Table 1.

[0068] Table 1 Performance test data of polyurethanes prepared using polyols from Examples 1 and Comparative Examples 1-3

[0069]

[0070] As shown in Table 1, the polyurethane prepared using the polyol of Example 1 exhibits superior mechanical properties (tensile strength, elongation at break, stress at 100% elongation, tear strength), dynamic thermomechanical properties (glass transition temperature), thermal stability (temperature at 5% thermal weight loss), and color compared to the polyurethanes prepared using the polyols of Comparative Examples 1-3. This is because the polyol preparation process in Example 1 utilizes a Fe3O4@mSiO2@STA+DMC catalytic system, while Comparative Examples 1-3 employ a conventional acid (phosphoric acid, sulfuric acid, and p-toluenesulfonic acid) + DMC catalytic system.

[0071] 1) The Fe3O4@mSiO2@STA used in Example 1 is a core-shell magnetic solid acid. The Fe3O4 core provides superparamagnetism, which allows Fe3O4@mSiO2@STA to be completely removed by magnetic separation. This not only makes post-processing convenient and recyclable, but also effectively avoids the problem of acid residue. In contrast, the phosphoric acid, sulfuric acid, and p-toluenesulfonic acid in Comparative Examples 1-3 are not only cumbersome to process and are easy to remain in polyols. The acidic residues will become degradation catalysts during polyurethane preparation, which will damage the thermal stability and mechanical properties of polyurethane.

[0072] 2) In Example 1, the mSiO2 shell in Fe3O4@mSiO2@STA has a high specific surface area and ordered channels. It can not only confine STA in the nanopores and prevent it from agglomerating and deactivating in the reaction medium, but also protect STA from high temperature or polar medium damage, improve its thermal stability and chemical stability. This makes the release and effect of its acidic sites during the reaction controlled and mild. Compared with phosphoric acid, sulfuric acid and p-toluenesulfonic acid in Comparative Examples 1-3, it can effectively avoid problems such as local over-acidity, violent exothermic reaction and side reactions (oxidation, dehydration, sulfonation). As a result, the polyol molecular chain prepared in Example 1 is regular and has good color. In turn, the final polyurethane product has better mechanical properties, dynamic thermomechanical properties, thermal stability and color.

[0073] 3) In Example 1, Fe3O4@mSiO2@STA, compared to the traditional acids in Comparative Examples 1-3, not only provides an acidic environment for DMC, but also exhibits a synergistic effect with DMC, specifically manifested in:

[0074] The mSiO2 shell of Fe3O4@mSiO2@STA provides a large adhesion and dispersion surface for DMC catalyst and reactants. The STA of Fe3O4@mSiO2@STA can stabilize the active centers formed between the oil feedstock and DMC through electrostatic interaction. The nanopores of Fe3O4@mSiO2@STA create a high local concentration of active centers (DMC) and reactant environment, thereby effectively improving the catalytic polymerization efficiency of DMC.

[0075] In Fe3O4@mSiO2@STA, the strong acidity of STA is effectively "tamed" within the nanopores of the mSiO2 shell, avoiding chain transfer and chain termination side reactions caused by free strong acid. This allows DMC to better exert its high selectivity. Furthermore, STA can assist DMC in stabilizing the polyol growth chain and reducing the polyol's unsaturation, resulting in a low degree of unsaturation in the prepared polyol. Consequently, the final polyurethane product exhibits better mechanical properties, dynamic thermomechanical properties, and thermal stability.

[0076] Fe3O4@mSiO2@STA provides DMC with uniformly dispersed active centers and a controlled acidic environment, making chain initiation and chain growth more synchronized during the polymerization reaction. This reduces the difference in reaction rates between different active centers and suppresses the isomerization side reaction of propylene oxide, thereby making the prepared polyol molecular chains more regular and effectively improving the mechanical properties, dynamic thermomechanical properties, and thermal stability of the final polyurethane product.

[0077] In summary, this invention uses vegetable oil or vegetable oil derivatives as raw materials, high-functionality hydroxyl compounds with a functionality of 6-8 and low-functionality hydroxyl compounds with a functionality of 2-3 as initiators, epoxides as monomers, DMC as a catalyst, and Fe3O4@mSiO2@STA as an acidic auxiliary. The raw materials, initiators, and monomers undergo ring-opening polymerization in water under the action of the catalyst and acidic auxiliary to obtain polyols based on vegetable oils and their derivatives. This process is not only convenient and environmentally friendly, but also exhibits a good synergistic effect between Fe3O4@mSiO2@STA and DMC, effectively avoiding DMC deactivation while resulting in better performance of the prepared polyols. These polyols are more suitable for preparing polyurethane products with excellent comprehensive properties such as mechanical properties, thermal stability, and appearance, and have strong industrial application value.

[0078] Finally, it should be noted that the above are only some preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A method for synthesizing polyols based on natural plant oils and their derivatives, characterized in that, The method uses vegetable oil or vegetable oil derivatives as oil feedstock, high-functionality hydroxyl compounds with a functionality of 6-8 and low-functionality hydroxyl compounds with a functionality of 2-3 as initiators, epoxides as monomers, DMC as catalyst, and Fe3O4@mSiO2@STA as acidic auxiliaries. The oil feedstock, initiator, and monomers undergo ring-opening polymerization in water under the action of the catalyst and acidic auxiliaries to obtain polyols based on vegetable oil and its derivatives. The Fe3O4@mSiO2@STA is obtained by first coating a mesoporous silica shell on the surface of Fe3O4 to obtain Fe3O4@mSiO2, and then loading silicotungstic acid on the surface of Fe3O4@mSiO2.

2. The method for synthesizing polyols based on natural plant oils and their derivatives according to claim 1, characterized in that, The vegetable oil is selected from any one of palm oil, soybean oil, castor oil, rapeseed oil, cottonseed oil, sunflower seed oil, flaxseed oil, and cashew oil; the vegetable oil derivative is any one of hydroxylated vegetable oil and hydrogenated vegetable oil.

3. The method for synthesizing polyols based on natural plant oils and their derivatives according to claim 1, characterized in that, The high-functionality hydroxyl compound is selected from one or more of sucrose, sorbitol, and mannitol; the low-functionality hydroxyl compound is selected from one or more of diethylene glycol, propylene glycol, dipropylene glycol, and glycerol.

4. The method for synthesizing polyols based on natural plant oils and their derivatives according to claim 1, characterized in that, The epoxide hydrocarbon is one or more of ethylene oxide, propylene oxide, and butane oxide.

5. The method for synthesizing polyols based on natural plant oils and their derivatives according to claim 1, characterized in that, The mass ratio of oil feedstock: high-functionality hydroxyl compound: low-functionality hydroxyl compound: epoxide alkane: catalyst: acidic additive is (150-450): (20-150): (10-50): (300-500): (0.03-0.05): (0.05-0.5).

6. The method for synthesizing polyols based on natural plant oils and their derivatives according to claim 1, characterized in that, The preparation of Fe3O4@mSiO2@STA includes the following steps: 1) Under nitrogen protection, ferric chloride hexahydrate and ferrous chloride tetrahydrate were dissolved in water, heated to 55-65℃, ammonia was added to adjust the pH to be greater than 12, and the reaction was kept at the temperature and stirred for 20-40 minutes. Sodium citrate was added, and the reaction was kept at the temperature and stirred for 1-2 hours. The reaction was then stopped, magnetically separated, washed, and dried to obtain Fe3O4 powder. 2) Fe3O4 powder was uniformly dispersed in anhydrous ethanol to obtain Fe3O4 ethanol sol; tetraethyl orthosilicate was dispersed in ethanol to obtain tetraethyl orthosilicate ethanol solution; hexadecyltrimethylammonium bromide and sodium citrate were dissolved in an aqueous ethanol solution, and then Fe3O4 ethanol sol was added and stirred to mix evenly. Then ammonia water was added and stirred to mix evenly. Then tetraethyl orthosilicate ethanol solution was added and the reaction was stirred at room temperature for 5-7 hours. The reaction was then stopped, magnetic separation was performed, and the powder was washed and dried to obtain Fe3O4@mSiO2 powder. 3) Disperse silicotungstic acid in ethanol to obtain a silicotungstic acid ethanol solution. Impregnate Fe3O4@mSiO2 powder in the silicotungstic acid ethanol solution and ultrasonically disperse for 20-40 minutes. Rotary evaporate the resulting mixture until the solvent is completely evaporated. Place the solid obtained by evaporation in a muffle furnace for calcination and cool to room temperature to obtain Fe3O4@mSiO2@STA.

7. The method for synthesizing polyols based on natural plant oils and their derivatives according to claim 6, characterized in that, In step 1), the molar ratio of ferrous chloride tetrahydrate: ferric chloride hexahydrate: sodium citrate is 1:2:(0.2-0.5).

8. The method for synthesizing polyols based on natural plant oils and their derivatives according to claim 6, characterized in that, In step 2), the molar ratio of Fe3O4: cetyltrimethylammonium bromide: sodium citrate: tetraethyl orthosilicate is 1:(2-10):(1-3):(15-35).

9. The method for synthesizing polyols based on natural plant oils and their derivatives according to claim 6, characterized in that, In step 3), the mass ratio of Fe3O4@mSiO2 to silicotungstic acid is (1-4):1; the calcination temperature is 140-160℃, and the calcination time is 2-4 hours.

10. The method for synthesizing polyols based on natural plant oils and their derivatives according to any one of claims 1-9, characterized in that, The preparation of the polyols based on vegetable oils and their derivatives includes the following steps: a) Stir the oil feedstock, high-functionality hydroxyl compound, and low-functionality hydroxyl compound at 80-100℃ for 1-3 hours to form a homogeneous mixture. Dehydrate the resulting mixture under vacuum at 110-120℃ for 1-3 hours until the water content of the system is ≤0.03%. b) After dehydration, stop the vacuum, cool down to below 100°C, add acidic additives and catalyst, stir and mix evenly, then heat to 130-140°C, and quickly add some epoxy alkane under stirring to induce the reaction. After successful induction, continuously add the remaining epoxy alkane. During the feeding process, maintain the temperature at 130-140°C and the pressure ≤ 0.5 MPa. After the feeding is completed, keep the reaction at the temperature for 1-3 hours. c) After the reaction is complete, cool down to below 90°C, degas under vacuum for 1-2 hours, cool the product down to below 60°C, and perform magnetic separation to recover the acidic additives. Decolorize and filter the crude polyol obtained from the separation to obtain polyols based on vegetable oils and their derivatives.

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