Preparation method and application of high-grade fatty acid monoester polyol using discarded oil as raw material

Abstract

The application discloses a preparation method and application of a high-grade fatty acid monoester flame-retardant polyol taking gutter oil as raw material, and comprises the following steps: adding a high-grade fatty acid monoester to a phosphorus-containing acid compound to react and adding an epoxy compound to react to obtain the high-grade fatty acid monoester flame-retardant polyol; the phosphorus-containing acid compound is anhydrous phosphoric acid or pyrophosphoric acid. The application can prepare a green, environment-friendly, high-efficiency and excellent-mechanical-property bio-based polyurethane flame retardant, solves the problems of low self-flame-retardant performance of the existing bio-based polyurethane, influence of adding a flame retardant on mechanical properties and safety hazards during use, and is a high-efficiency, excellent-mechanical-property and green bio-based polyurethane flame retardant.

Description

Technical Field

[0001] This invention relates to the field of polyurethane materials, specifically to a method for preparing advanced fatty acid monoester polyols using waste cooking oil as raw material and their applications. Background Technology

[0002] With the increasing global consumption of petroleum energy and the depletion of non-renewable resources such as petroleum, the prices of petroleum and petrochemical products continue to rise, drawing attention to reducing reliance on and use of petroleum-based plastic products. To fundamentally address this issue, researchers are exploring alternatives to petrochemical raw materials using green, sustainable, and renewable resources. With the increasing depletion of petroleum resources and increasingly stringent environmental legislation, there is an urgent need to develop environmentally friendly waterborne polyurethane (WPU) coatings.

[0003] With the increasing depletion of non-renewable fossil resources, the government's intensified efforts to control environmental pollution, and the rising demands for flame-retardant properties in materials, research on using renewable natural biomass resources to replace fossil resources in the preparation of environmentally friendly bio-based flame-retardant polyurethane foam insulation materials has received widespread attention. The main raw materials for bio-based polyols, such as biodiesel, vegetable oils, fatty acids, or dimer fatty acids, are widely available, including castor oil, peanut oil, soybean oil, olive oil, neem oil, and cottonseed oil.

[0004] However, bio-based polyurethane is a flammable material. Ordinary polyurethane has a very low limiting oxygen index (LOI), typically around 18%, making it highly susceptible to combustion. The combustion process is accompanied by the release of heat and smoke, and dripping molten material can cause secondary combustion. To address these issues, flame retardants are typically added to give bio-based polyurethane flame retardancy. This is done through physical incorporation during polymer synthesis, usually using halogenated or phosphorus- and nitrogen-containing compounds, as well as traditional flame retardants such as aluminum hydroxide and magnesium hydroxide. However, these physical flame retardants are often added in large quantities, easily precipitate, have poor compatibility with polyurethane, and affect the material's mechanical properties. Halogenated flame retardants, on the other hand, release large amounts of toxic gases during combustion, and their use has long been restricted internationally. Therefore, developing a novel, low-toxicity, highly atom-efficient, and environmentally friendly method is urgently needed. Summary of the Invention

[0005] Purpose of the invention: To address the problems existing in current flame retardants, this invention provides a method for preparing advanced fatty acid monoester polyols using waste cooking oil as raw material. This invention can prepare a green, environmentally friendly, highly efficient flame retardant, and excellent mechanical properties bio-based polyurethane flame retardant, solving the problems of low inherent flame retardancy of existing bio-based polyurethanes, the negative impact of adding flame retardants on mechanical properties, and safety hazards during use. This invention provides a highly efficient, environmentally friendly bio-based polyurethane flame retardant with excellent mechanical properties.

[0006] The present invention also provides the aforementioned higher fatty acid monoester polyols and their applications.

[0007] Technical solution: In order to achieve the above objectives, the present invention provides a method for preparing higher fatty acid monoester polyols using waste cooking oil as raw material, comprising the following steps: adding higher fatty acid monoesters dropwise to a phosphoric acid compound and reacting, then adding an epoxide compound and reacting to obtain higher fatty acid monoester polyols, wherein the phosphoric acid compound is anhydrous phosphoric acid or pyrophosphate.

[0008] The anhydrous phosphoric acid is phosphoric acid with a purity of ≥98%.

[0009] The higher fatty acid monoesters are derived from processed waste cooking oil, and the higher fatty acid monoesters include any one or more of methyl epoxide, methyl palmitate, methyl trans linoleate, and methyl stearate.

[0010] The epoxy compound is one or more of ethylene oxide, propylene oxide, epichlorohydrin, monohalogenated ethylene oxide, monohalogenated propylene oxide, dihalogenated ethylene oxide, and dihalogenated propylene oxide.

[0011] The molar ratio of the phosphoric acid compound, the higher fatty acid monoester, and the epoxide compound is 1:0.5-3:1.5-8.

[0012] Preferably, the molar ratio of the phosphoric acid compound, methyl methacrylate, and propylene oxide is 1.02:2.83:6.2.

[0013] The method for preparing higher fatty acid monoester polyols according to the present invention includes the following:

[0014] Take anhydrous phosphoric acid or pyrophosphoric acid, place it in a reaction apparatus, add higher fatty acid monoesters and epoxides, and keep the reaction at a constant temperature until the reaction is complete.

[0015] The process involves adding higher fatty acid monoesters dropwise at room temperature, and then maintaining the temperature at 50–100°C for 1–5 hours after the addition is complete. Then, epoxide compounds are added dropwise in three batches at 50–100°C, with each batch maintained at the temperature for 1–5 hours after the addition is complete.

[0016] Furthermore, after the reaction of the epoxy compound is complete and the temperature stabilizes, the epoxy compound is slowly and uniformly added dropwise. The dropping rate must be strictly controlled to prevent violent boiling. After the epoxy compound is added, the mixture is kept at the temperature for 1 to 5 hours to allow the reaction to proceed fully. A constant pressure dropping funnel should be used to add the epoxy compound, and the dropping rate should be controlled at one drop every 5 to 10 seconds. This is because the reaction is violent, and a dropping rate that is too fast will cause boiling and the epoxy compounds will react with each other.

[0017] Preferably, the preparation method includes the following steps:

[0018] (1) Place 52.00g of 85% phosphoric acid and 42.72g of xylene in a single-necked flask equipped with a magnetic separator, a water separator, and a condenser. Place the flask in an oil bath at 160℃ and start distillation for 12 hours. Stop distillation when the water level in the water separator stops changing. Separate the phosphoric acid and xylene solutions and take the lower layer to obtain anhydrous phosphoric acid with a purity of 98-99%.

[0019] (2) Take the phosphoric acid after the reaction in step (1) and put it into a four-necked flask equipped with a thermometer, a condenser and a stir bar. Add the higher fatty acid alkyl ester prepared from waste cooking oil dropwise at room temperature. After the addition is complete, keep it at 90°C for 4 hours. Then, add propylene oxide dropwise in three batches at 90°C. Keep it at 90°C for 2 hours after each batch is added.

[0020] The higher fatty acid monoester polyols prepared by the method described in this invention are higher fatty acid monoester polyols.

[0021] The higher fatty acid monoester polyol is a colorless or pale yellow viscous oligophosphophosphate containing one or two or more -P(O)OH structures in the middle of the chain.

[0022] The present invention relates to the application of the higher fatty acid monoester polyol as a flame retardant in the preparation of highly flame-retardant polyurethane foam.

[0023] The advanced fatty acid monoester bio-based flame-retardant polyol prepared by this invention using a specific method is a colorless or pale yellow, slightly viscous, clear oily liquid with an acid value ≤1 mgKOH / g. In the application of polyurethane foam, acids can prevent the normal function of the amine catalyst used in the foaming reaction, resulting in foam that does not rise, has inappropriate pore size, or becomes sticky and brittle. The flame retardant of this invention has a low acid value and does not affect the preparation of the foam or the basic properties of the material.

[0024] This invention relates to a bio-based flame-retardant polyol that can be added to polyurethane. The raw materials are derived from renewable resources, making it green and environmentally friendly. The introduction of environmentally friendly phosphorus allows it to decompose during combustion to produce phosphate molecules, thus exerting a flame-retardant effect and preventing the release of large amounts of toxic fumes during combustion. Simultaneously, the bio-based polyurethane undergoes dehydration and carbonization during combustion, forming a char layer on the surface of the burning material to isolate it from the combustion environment, further enhancing the flame-retardant effect. Therefore, an overall flame-retardant effect is achieved, exhibiting highly efficient flame retardancy. Moreover, this synthesized bio-based flame-retardant polyurethane is an intrinsic flame-retardant polyurethane, requiring no added flame retardants. This solves the problems of large amounts of flame retardants, easy precipitation, and low flame-retardant efficiency associated with traditional flame-retardant polyurethanes, ensuring the excellent mechanical properties of the polyurethane.

[0025] This invention is the first to prepare bio-based flame-retardant polyols using higher fatty acid monoesters prepared from waste cooking oil as raw materials. This not only effectively consumes and utilizes waste cooking oil, making it environmentally friendly, but also ensures that the flame retardant prepared from higher fatty acid monoesters retains the plasticizing properties of higher fatty acid monoesters, such as methyl oxyoxide, even after ring-opening. Adding it to polyurethane significantly enhances its mechanical properties and further improves its flame-retardant effect. Higher fatty acid monoesters have good compatibility with polyurethane and other materials, low volatility, and good stabilizing effects against light and heat, making them suitable for all polyvinyl chloride plastic products. Adding substances like methyl oxyoxide can significantly improve the physical properties of the product and extend its aging time. When used in conjunction with metal stabilizers such as barium, cadmium, and zinc, they exhibit good synergistic effects. Therefore, adding higher fatty acid alkyl esters to flame retardants can enhance the integration of the flame retardant with the material, making it less likely to precipitate and cause damage to the environment and material properties.

[0026] The advanced fatty acid monoesters prepared using waste cooking oil in this invention can also be made by directly using purchased pure advanced fatty acid monoesters and adding them to polyurethane. This will further improve the flame retardant and mechanical properties, but it will also further increase the cost.

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

[0028] This invention uses high-grade fatty acid monoesters extracted from gutter oil as raw materials. The raw materials are environmentally friendly, readily available, and inexpensive. Using gutter oil as raw materials for waste utilization greatly reduces costs and alleviates the difficulties in recycling and reusing gutter oil, thus reducing the environmental pollution problem.

[0029] This invention utilizes the ring-opening reaction of epoxy resin to prepare phosphorus-containing flame-retardant polyols. Compared to traditional methods of preparing flame-retardant polyols using phosphorus oxychloride and alcohols, this invention requires simpler conditions, eliminates the need for additional catalysts and solvents, and significantly reduces preparation costs. The raw materials are readily available, stable, and have low toxicity to humans. Furthermore, the hydroxyl-containing structure of the polyol allows it to function as a reactive flame retardant, enabling it to combine with polyurethane materials without easily releasing pollutants and causing environmental damage.

[0030] This invention is the first to use bio-based flame-retardant polyols prepared from high-grade fatty acid monoesters made from waste cooking oil as raw materials. These polyols can be added to polyurethane as both flame retardants and plasticizers, effectively improving the flame retardancy and mechanical properties of polyurethane products. Attached Figure Description

[0031] Figure 1 The infrared spectrum of the product of Example 1 of the present invention is shown. Detailed Implementation

[0032] The present invention will now be described in detail with reference to specific embodiments.

[0033] Unless otherwise specified, the experimental methods described in the embodiments are conventional methods; the reagents and materials described are commercially available unless otherwise specified.

[0034] Acid value determination method:

[0035] Weigh 0.2–0.5 g of the sample into an Erlenmeyer flask using an analytical balance. Add approximately 50 mL of anhydrous ethanol and shake the flask thoroughly to dissolve the sample completely. Heating may be necessary in some cases. Add one drop of homemade phenolphthalein indicator, shake well, and titrate with a 0.02 mol / L KOH-CH3CH2OH standard titration solution until the sample turns blue and remains so for 30 seconds. Perform a blank test simultaneously.

[0036] Calculation formula: Acid value (mg KOH·g) -1 = (Vsample - Vempty) × c × 56.11 / m

[0037] In the formula, Vsample represents the volume of alkaline standard solution used during sample titration, in mL.

[0038] Vempt — The volume of alkaline standard solution used in the titration of the blank sample, in mL.

[0039] c — Concentration of the alkaline standard solution, mol / L

[0040] m — Sample mass, g

[0041] 56.11 — The specific numerical value of the molar mass of potassium hydroxide, in g / mol.

[0042] The preparation method of epoxy methyl ester in this embodiment of the invention follows the method described in existing literature, namely, "Preparation of PVC Epoxy Fatty Acid Methyl Ester Plasticizer by Modification of Waste Cooking Oil," China Plastics, November 2014. The epoxy fatty acid methyl ester plasticizer prepared in Section 1.3 is the epoxy methyl ester of this invention. The prepared epoxy methyl ester has an epoxy value of 3.9%, an iodine value of 8.70 g / 100 g, and an acid value of 6.5 mg KOH / g. Other raw materials such as methyl palmitate, methyl trans-linoleate, and methyl stearate can also be prepared by referring to the aforementioned literature or other literature using waste cooking oil as a raw material. Alternatively, commercially available epoxy methyl ester can be used directly.

[0043] In the examples, the anhydrous phosphoric acid was phosphoric acid with a purity of 99%.

[0044] Example 1

[0045] 5g of anhydrous phosphoric acid was weighed and placed in a four-necked flask equipped with a mechanical stirrer, thermometer, and condenser. 14.74g of methyl methacrylate (MMA) was added using a constant-pressure dropping funnel. The liquid temperature was controlled at 70℃, and the reaction was maintained at 70℃ for 4 hours after the addition was completed. Then, 6.00g of propylene oxide was added dropwise in three batches, each time maintaining the temperature at 90℃ for 2 hours. Excess propylene oxide was removed by vacuum distillation to prepare MMA polyol. The final product had an acid value of 1.04 mg KOH / g.

[0046] Example 2

[0047] Referring to Example 1, 5g of anhydrous phosphoric acid was weighed and placed in a four-necked flask equipped with a mechanical stirrer, thermometer, and condenser. 14.74g of methyl methacrylate (MMA) was added using a constant-pressure dropping funnel. The liquid temperature was controlled at 90°C, and after the addition was complete, the reaction was maintained at 90°C for 4 hours. Then, 6.00g of propylene oxide was added dropwise in three batches, each batch maintained at 90°C for 2 hours. Excess propylene oxide was removed by vacuum distillation to prepare MMA polyol. The final product had an acid value of 0.95 mg KOH / g.

[0048] Example 3

[0049] Referring to Example 1, 5g of anhydrous phosphoric acid was weighed and placed in a four-necked flask equipped with a stirrer, thermometer, and condenser. 44.22g of methyl methacrylate (MMA) was added using a constant-pressure dropping funnel. The liquid temperature was controlled at 90°C, and the reaction was maintained at 90°C for 4 hours after the addition was completed. Then, 6g of propylene oxide was added dropwise three times using a constant-pressure dropping funnel, each time maintaining the temperature at 90°C for 2 hours. Excess propylene oxide was removed by vacuum distillation to prepare MMA polyol. The final product had an acid value of 0.40 mg KOH / g. In this example, increasing the amount of MMA effectively reduced the acid value.

[0050] The infrared spectrum of the product prepared in this embodiment is as follows: Figure 1 As shown. In the infrared spectrum of epoxy methyl ester, 3460 cm⁻¹ -1 The absorption peak at 2930 cm⁻¹ is a vibrational absorption peak of -OH, which may be caused by residual glycerol; -1 2855cm -1 These are the stretching vibration absorption peaks of the methyl and methylene groups, respectively; 1740 cm⁻¹ -1 This is the absorption peak of the C=O stretching vibration of fatty acid esters; 833 cm⁻¹ -1 The peak at 833 cm⁻¹ is a characteristic absorption peak for epoxy groups. Compared to epoxy methyl ester, the absorption peak of the hydroxyl group in epoxy-17 is stronger, reaching 833 cm⁻¹. -1 The absorption peak of the epoxy group disappears. Furthermore, at 1020 cm⁻¹... -1 The absorption peak at 1140 cm⁻¹ is POC. -1 The absorption peak is at P=O. These results indicate that methyl epoxide undergoes a ring-opening reaction with phosphoric acid, introducing phosphate ester groups onto the long chain of soybean oil methyl ester.

[0051] Example 4

[0052] Referring to Example 1, 5g of anhydrous phosphoric acid was weighed and placed in a four-necked flask equipped with a stirrer, thermometer, and condenser. 44.22g of epichlorohydrin was added using a constant-pressure dropping funnel. The liquid temperature was controlled at 90°C, and after the addition was complete, the reaction was maintained at 90°C for 4 hours. Then, 2.96g of epichlorohydrin was added dropwise three times using a constant-pressure dropping funnel, each time maintaining the temperature at 90°C for 3 hours. Excess epichlorohydrin was removed by vacuum distillation to prepare epichlorohydrin polyol. The final product had an acid value of 0.55mgKOH / g.

[0053] Example 5

[0054] Referring to Example 1, 5g of anhydrous phosphoric acid and 20g of 1,4-dioxane were weighed and placed in a four-necked flask equipped with a mechanical stirrer, thermometer, and condenser. 44.22g of epichlorohydrin was added using a constant-pressure dropping funnel. The liquid temperature was controlled at 90°C, and the reaction was maintained at 90°C for 4 hours after the addition. Then, 2.96g of epichlorohydrin was added dropwise three times using a constant-pressure dropping funnel, each time maintaining the temperature at 90°C for 3 hours. Excess epichlorohydrin was removed by vacuum distillation to prepare epichlorohydrin polyol. The final product had an acid value of 0.45mgKOH / g. In this example, the solvent 1,4-dioxane was added to make the phosphoric acid more dispersed, resulting in a more uniform reaction and a lower acid value.

[0055] Example 6

[0056] Example 6 uses the method of Example 3, but replaces anhydrous phosphoric acid with pyrophosphoric acid.

[0057] Example 7

[0058] Referring to Example 1, 5g of anhydrous phosphoric acid and 20g of 1,4-dioxane were weighed and placed in a four-necked flask equipped with a mechanical stirrer, thermometer, and condenser. 40.26g of methyl palmitate was added using a constant-pressure dropping funnel. The liquid temperature was controlled at 90°C, and the reaction was maintained at 90°C for 4 hours after the addition was completed. Then, 2.96g of epichlorohydrin was added dropwise three times using a constant-pressure dropping funnel, each time maintaining the temperature at 90°C for 3 hours. Excess epichlorohydrin was removed by vacuum distillation, and the final product had an acid value of 0.48mgKOH / g.

[0059] Example 8

[0060] Referring to Example 1, 5g of anhydrous phosphoric acid was weighed and placed in a four-necked flask equipped with a stirrer, thermometer, and condenser. 44.25g of trans-linoleic acid methyl ester was added using a constant-pressure dropping funnel. The liquid temperature was controlled at 90°C, and the reaction was maintained at 90°C for 4 hours after the addition was completed. Then, 6g of propylene oxide was added dropwise three times using a constant-pressure dropping funnel, each time maintaining the temperature at 90°C for 2 hours. Excess propylene oxide was removed by vacuum distillation, and the final product had an acid value of 0.50 mg KOH / g.

[0061] Example 9

[0062] Referring to Example 1, 5g of anhydrous phosphoric acid was weighed and placed in a four-necked flask equipped with a stirrer, thermometer, and condenser. 44.77g of methyl stearate was added using a constant-pressure dropping funnel. The liquid temperature was controlled at 90°C, and after the addition was complete, the reaction was maintained at 90°C for 4 hours. Then, 6g of propylene oxide was added dropwise three times using a constant-pressure dropping funnel, each time maintaining the temperature at 90°C for 2 hours. Excess propylene oxide was removed by vacuum distillation, and the final product had an acid value of 0.51mgKOH / g.

[0063] Example 10

[0064] Application of higher fatty acid monoester polyols in polyurethane foam

[0065] The raw materials used to prepare the polyurethane foam are all commercially available, and the method used is also a conventional polyurethane preparation method.

[0066] Among them: PPG 4110 (polyether 4110 polyether polyol) was purchased from Jining Huakai Resin Co., Ltd.; DBTDL (dibutyltin dilaurate, item number D100274) was purchased from Aladdin Co., Ltd.

[0067] TEOA (triethanolamine, product number T478536) was purchased from Aladdin Co., Ltd., AK 8805 (polyurethane foam stabilizer AK 8805) was purchased from Jiangsu Meiside Chemical Co., Ltd., n-hexane was purchased from Shanghai Lingfeng Chemical Reagent Co., Ltd., and PR (epoxy methyl ester flame retardant polyol prepared in Example 3 of this invention).

[0068] Table 1 Formulation of Flame-Retardant Polyurethane Foam

[0069] PPG 4110 (g) 60 60 60 60 Water (g) 0.6 0.6 0.6 0.6 DBTDL (g) 1.5 1.5 1.5 1.5 TEOA (g) 0.3 0.3 0.3 0.3 AK 8805 (g) 1.2 1.2 1.2 1.2 n-hexane (g) 6 6 6 6 PR (g) 0 7.2 15.6 24 PR (wt%) 0 10 18 25 Isocyanate index 1.2 1.2 1.2 1.2

[0070] The formulation of the polyurethane composite material is shown in Table 1. The R (R = -NCO / -OH) of the PU composite material is 1.2. First, the polyol, water, n-hexane, dibutyltin dilaurate (DBTDL), triethanolamine (TEOA), AK8805 (silicone oil, polyurethane foam stabilizer), and the flame retardant PR prepared in Example 3 were thoroughly mixed in a plastic beaker at 1000 rpm for 10 minutes to form a homogeneous mixture. Isocyanate was added to make the isocyanate index 1.2, and the mixture was stirred at 1500 rpm for 10 seconds. Then, the mixture was allowed to freely foam in the plastic beaker and cured at room temperature for 72 hours. Finally, the PU composite material was cut into standard sizes for testing.

[0071] Test Standards

[0072] (1) Limiting Oxygen Index Test

[0073] The limiting oxygen index (LOI) is an important indicator of the ease with which a material burns. A higher LOI value indicates that the material requires more oxygen to burn, making it more difficult to burn and exhibiting better flame retardant properties. The limiting oxygen index was tested using a JF-3 HC-2C instrument (Jiangning, China) according to ASTM D2863-97. The sample size was 100×10×10mm. 3 .

[0074] (2) Compression strength test

[0075] The compressive strength of the sample was tested according to ASTM D1621, and the sample size was 50×50×25mm. 3 The deformation is 10%.

[0076] To evaluate the flammability of the PU composite materials, Table 2 lists the LOI and UL-94 test results. PU-0 had an LOI value of 20.0%, failing the UL-94 test and exhibiting dripping phenomena. The high flammability of PU-0 is due to the large specific surface area and porous structure of polyurethane. However, after adding the flame retardant prepared according to this invention, the LOI value of PU-P continuously increased. When the flame retardant addition amount was 10-25 wt%, the LOI value of PU-P increased from 23.7% to 26.2%, a very significant effect.

[0077] Table 2. LOI and UL-94 results for PU composite materials.

[0078]

[0079] To evaluate the mechanical properties of the PU composites, Table 3 lists the compressive strength of the PU composites. Compared with PU-0 without flame retardant, the compressive strength of the polyurethane increased from 0.130 MPa to 0.265 MPa after adding flame retardant (PR), significantly improving the mechanical properties of the polyurethane foam. In fact, adding flame retardants to polyurethane foam affects its mechanical properties, and the greater the amount of flame retardant added, the greater the impact on mechanical properties. Many existing flame retardants lead to a decrease in the mechanical properties of polyurethane foam (such as compressive strength) (see Table 4 for details), and the higher the amount added, the lower the strength. For example, PUF-30 contains 30% flame retardant. However, the specific flame retardant prepared according to this invention, when added to polyurethane, can significantly enhance its mechanical properties and further improve the flame retardant effect. The epoxy methyl ester flame retardant in this invention has good compatibility with materials such as polyurethane, low volatility, and good stabilizing effect on light and heat. It is applicable to all polyvinyl chloride plastic products, can significantly improve the physical properties of the products and extend the aging time, and has a good synergistic effect when used in combination with metal stabilizers such as barium, cadmium and zinc.

[0080] Table 3 Compressive strength results of PU composite materials

[0081] PU-0 0.130 PU-P / 10 0.230 PU-P / 18 0.248 PI-P / 25 0.275

[0082] Table 4. Effects of flame retardant addition on the mechanical properties of polyurethane foam in existing technologies.

[0083]

[0084] Reference 1: Preparation and performance study of flame-retardant soybean oil-based rigid polyurethane foam, Huang Shizhao, Master's thesis, Hubei University, May 2019.

[0085] Reference 2: Synthesis of Triazine Ring Polyols and Their Application in Polyurethane, Xu Shaoshuai, Master's Thesis, Hubei University, May 2020.

[0086] Reference 3: Research on flame-retardant rigid polyurethane foam, Feng Yuelan, Chemical Propellants and Polymer Materials, Vol. 14, No. 4, 2016.

[0087] Reference 4: Preparation and performance study of flame-retardant rigid polyurethane foam, Liu Fengjiao, Master's thesis, Beijing University of Chemical Technology, June 2014.

Claims

1. A method for preparing flame-retardant polyols of higher fatty acid monoesters from waste cooking oil, characterized in that, Includes the following steps: Weigh 5g of anhydrous phosphoric acid and place it in a four-necked flask equipped with a stirrer, thermometer, and condenser. Add 44.22g of epoxy fatty acid methyl ester using a constant pressure dropping funnel, and control the liquid temperature at 90℃. After the addition is complete, keep the reaction at 90℃ for 4 hours. Then, add 6g of propylene oxide three times using a constant pressure dropping funnel, keeping the temperature at 90℃ for 2 hours each time. Remove excess propylene oxide by vacuum distillation to prepare epoxy fatty acid methyl ester polyol.

2. The application of the higher fatty acid monoester polyol of claim 1 as a flame retardant in the preparation of highly flame-retardant polyurethane foam; wherein the polyurethane foam composition is as shown below: 。

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