Branched organic urea compounds, methods of making and using the same, and block castor oil-based polyester polyols, methods of making the same, and bio-based polyurethane materials

Abstract

The application belongs to the technical field of polyurethane materials, and particularly relates to a branched organic urea compound and a preparation method and application thereof, a block castor oil-based polyester polyol and a preparation method thereof, and a bio-based polyurethane material. The branched organic urea compound provided by the application has a structure shown in formula I. The branched organic urea compound provided by the application is used as a catalyst for preparing the block castor oil-based polyester polyol, has the characteristics of being free of metal, high efficiency, environmental protection, no need for post-treatment, flame retardation, and convenient industrial production, can be used to prepare a cheap and easily obtained reactive flame-retardant castor oil-based polyester polyol, and can improve the performance of the bio-based polyurethane, including chemical resistance, heat resistance, flexibility, adhesion, and flame retardation.

Description

Technical Field

[0001] This invention belongs to the field of polyurethane materials technology, specifically relating to branched organic urea compounds and their preparation methods and applications, block castor oil-based polyester polyols and their preparation methods, and bio-based polyurethane materials. Background Technology

[0002] Castor oil is a natural triglyceride with hydroxyl groups and long fatty acid chains in its molecular structure. As a type of non-edible vegetable oil, it has advantages such as high relative density, high flash point, low freezing point, green and environmentally friendly properties, renewability, good biodegradability, and low ecotoxicity. It can be used to replace petrochemical-based polyester polyols in the preparation of various functional polyurethane materials.

[0003] However, due to the disadvantages of castor oil, such as low hydroxyl value, poor reactivity, easy shrinkage, and poor flame retardancy, its practical application is limited. By preparing derivatives through transesterification, its hydroxyl value, mechanical properties, and crosslinking density of polyurethane materials can be improved.

[0004] Catalyst selection is crucial for the transesterification synthesis of castor oil-based polyester polyols. Commonly used catalysts include alkoxide catalysts of alkali metals and alkaline earth metals, organotitanium catalysts, organotin catalysts, organosammonium catalysts, and other organometallic compound catalysts. These catalysts have high catalytic activity, but they also have drawbacks such as difficulty in catalyst separation, impact on polyurethane performance, and heavy metal pollution that can harm human health. When using catalysts such as small-molecule organic amines, they have the advantages of high activity and low reaction temperature, but they also have disadvantages such as difficulty in post-processing separation, impact on the properties of polyurethane materials (including chemical resistance, heat resistance, flexibility, and adhesion), and easy catalyst migration. Summary of the Invention

[0005] The purpose of this invention is to provide branched organic urea compounds and their preparation methods and applications, block castor oil-based polyester polyols and their preparation methods, and bio-based polyurethane materials. The branched organic urea compounds provided by this invention, as catalysts for the preparation of block castor oil-based polyester polyols, have the advantages of being metal-free, having high catalytic activity, and requiring no post-treatment. At the same time, the branched organic urea compounds can play a flame-retardant role and have good compatibility, which can significantly improve the performance of bio-based polyurethane materials, including chemical resistance, heat resistance, flexibility, adhesion, and flame retardancy.

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

[0007] This invention provides a branched organic urea compound having the structure shown in Formula I:

[0008]

[0009] This invention provides a method for preparing the branched organic urea compound described above, comprising the following steps:

[0010] In a protective gas atmosphere, 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, an organic solvent, and m-toluene isocyanate were mixed and reacted to obtain the branched organic urea compound.

[0011] This invention provides the application of the branched organic urea compound described in the above technical solution or the branched organic urea compound prepared by the preparation method described in the above technical solution as a catalyst in the preparation of castor oil-based polyester polyols.

[0012] This invention provides a method for preparing block castor oil-based polyester polyols, comprising the following steps:

[0013] Castor oil, catalyst, and block copolymer are mixed and subjected to transesterification to obtain the block castor oil-based polyester polyol.

[0014] The catalyst is a branched organic urea compound, which has the structure shown in Formula I:

[0015]

[0016] The block composition includes one or more of nitrogen-containing straight-chain polyols, nitrogen-containing branched polyols, and nitrogen-containing heterocyclic polyols.

[0017] Preferably, the castor oil has an acid value ≤ 2.0 mg KOH / g and a hydroxyl value of 154–170 mg KOH / g;

[0018] The block composition includes one or more of the following: cashew nut shell oil Mannich polyol, 1,3,5-tris(2-hydroxyethyl)cyanuric acid, tetrahydroxyethyl ethylenediamine, hydroxyethyl hexahydrotriazine, and N,N,N,N-tetra(2-hydroxypropyl)-p-phenylenediamine;

[0019] The cashew nut shell oil Mannich polyol has a hydroxyl value of 240–480 mg KOH / g, the 1,3,5-tris(2-hydroxyethyl)cyanuric acid has a hydroxyl value of 630–650 mg KOH / g, the tetrahydroxyethylethylenediamine has a hydroxyl value of 940–955 mg KOH / g, the hydroxyethyl hexahydrotriazine has a hydroxyl value of 760–770 mg KOH / g, and the N,N,N,N-tetra(2-hydroxypropyl)p-phenylenediamine has a hydroxyl value of 650–665 mg KOH / g.

[0020] The mass ratio of castor oil to block is 45-75:15-40.

[0021] Preferably, the mass ratio of castor oil to catalyst is 45-75:0.01-0.08.

[0022] Preferably, the transesterification reaction includes a first-stage transesterification reaction and a second-stage transesterification reaction performed sequentially; the temperature of the first-stage transesterification reaction is 60–170°C, the time is 8–15 h, and the first-stage transesterification reaction is carried out in a protective gas atmosphere; the temperature of the second-stage transesterification reaction is 60–170°C, the time is 1–8 h, and the second-stage transesterification reaction is carried out under vacuum conditions with a vacuum degree of -0.1 to -0.085 MPa.

[0023] After the transesterification reaction is completed, a transesterification reaction solution is obtained. After obtaining the transesterification reaction solution, the process further includes: breaking the vacuum of the transesterification reaction solution and heating it, then removing impurities under vacuum conditions, and cooling it to obtain the block castor oil-based polyester polyol. The impurity removal temperature is 130-220°C, the time is 2-6 hours, and the vacuum degree is -0.1--0.09 MPa.

[0024] The present invention provides a block castor oil-based polyester polyol prepared by the preparation method described in the above technical solution.

[0025] Preferably, the block castor oil-based polyester polyol has a hydroxyl value of 180-400 mg KOH / g and an acid value of ≤1.5 mg KOH / g.

[0026] This invention provides a bio-based polyurethane material, wherein the polyester polyol segments constituting the bio-based polyurethane material include the block castor oil-based polyester polyol described in the above technical solution.

[0027] This invention provides a branched organic urea compound having the structure shown in Formula I. The branched organic urea compound with the structure shown in Formula I provided by this invention, as a catalyst for preparing castor oil-based polyester polyols, features metal-free properties, high efficiency, environmental friendliness, no need for post-treatment, and flame retardancy. It can be used to prepare inexpensive and readily available reactive flame-retardant castor oil-based polyester polyols, thereby enhancing the competitiveness of the bio-based polyurethane industry.

[0028] This invention provides a method for preparing block castor oil-based polyester polyol, comprising the following steps: mixing castor oil, a catalyst, and a block copolymer to undergo an ester exchange reaction to obtain the block castor oil-based polyester polyol. This invention uses a branched organic urea compound with the structure shown in Formula I as a catalyst, which has the advantages of high catalytic activity, being metal-free, flame-retardant, and not affecting the performance of polyurethane. The catalyst used in this invention contains a branched, cyclic stereostructure and has a suitable steric hindrance effect, enabling it to catalyze a directional, single ester exchange reaction between the block copolymer and castor oil. That is, the catalyst can effectively catalyze the ester exchange reaction between the block copolymer and castor oil, while minimally catalyzing the reaction between the block copolymer and diglyceride, one of the products of the ester exchange reaction, thereby obtaining a mixture of diglyceride and block castor oil-based polyester polyol. This effectively reduces the formation of small molecules such as glycerol and monoglycerides, improving the performance (including chemical resistance, heat resistance, flexibility, and adhesion) of the polyurethane prepared from the block castor oil-based polyester polyol prepared by this invention.

[0029] Meanwhile, this invention uses nitrogen-containing or nitrogen-heterocyclic block copolymers and castor oil as raw materials. Through selective transesterification, castor oil fatty acid segments are introduced into the molecular structure of the block copolymers to prepare a bio-based branched, multifunctional, low-molecular-weight, and highly reactive block castor oil-based polyester polyol containing both nitrogen-containing or nitrogen-heterocyclic polyester segments and long side-chain segments of castor oil fatty acids. This polyol can react well with isocyanate (NCO) groups to prepare bio-based polyurethane materials. Furthermore, by introducing nitrogen-containing or nitrogen-heterocyclic polyester segments, the chemical resistance, flame retardancy, flexibility, and adhesion of the block castor oil-based polyester polyol are improved.

[0030] The preparation method of block castor oil-based polyester polyol provided by this invention is simple, the raw materials are widely available and easy to obtain, and it is safer and more environmentally friendly to humans and nature, and has broad application prospects. Detailed Implementation

[0031] This invention provides a branched organic urea compound having the structure shown in Formula I:

[0032]

[0033] In this invention, unless otherwise specified, all raw materials / components used in the preparation are commercially available products well known to those skilled in the art.

[0034] This invention provides a method for preparing the branched organic urea compound described above, comprising the following steps:

[0035] In a protective gas atmosphere, 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, an organic solvent, and m-toluene isocyanate are mixed and reacted to obtain the branched organic urea compound. In this invention, the protective gas preferably includes nitrogen and / or a rare gas, wherein the rare gas can be argon; in the examples, the protective gas can be nitrogen. The organic solvent is preferably tetrahydrofuran; in the examples, anhydrous tetrahydrofuran can be used. The molar ratio of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine to m-toluene isocyanate is preferably 100:360. This invention does not have special requirements regarding the amount of organic solvent used, as long as the reaction proceeds smoothly. In this invention, the mixing preferably includes: dissolving the 2,4,6-tris(4-aminophenyl)-1,3,5-triazine in a portion of an organic solvent to obtain a 2,4,6-tris(4-aminophenyl)-1,3,5-triazine solution; dissolving the m-toluene isocyanate in the remaining organic solvent to obtain a m-toluene isocyanate solution; and adding the m-toluene isocyanate solution dropwise to the 2,4,6-tris(4-aminophenyl)-1,3,5-triazine solution. The reaction preferably includes sequentially performing a first-stage reaction and a second-stage reaction. The temperature of the first-stage reaction can be room temperature (20–30°C), and the time is preferably 15–20 hours. The second-stage reaction is preferably carried out under reflux conditions, and the time of the second-stage reaction is preferably 8–10 hours. In this invention, after the reaction is completed, a reaction solution is obtained; after obtaining the reaction solution, the invention preferably further includes: desolventizing the reaction solution and then sequentially washing and drying it to obtain the branched organic urea compound. The desolventizing is preferably carried out under vacuum conditions. The washing reagent is preferably diethyl ether. The preferred method for drying is oven drying.

[0036] This invention provides the application of the branched organic urea compound described in the above technical solution or the branched organic urea compound prepared by the preparation method described in the above technical solution as a catalyst in the preparation of castor oil-based polyester polyols.

[0037] This invention provides a method for preparing block castor oil-based polyester polyols, comprising the following steps:

[0038] Castor oil, catalyst, and block copolymer are mixed and subjected to transesterification to obtain the block castor oil-based polyester polyol.

[0039] The catalyst is a branched organic urea compound, which has the structure shown in Formula I:

[0040]

[0041] The block composition includes one or more of nitrogen-containing straight-chain polyols, nitrogen-containing branched polyols, and nitrogen-containing heterocyclic polyols.

[0042] In this invention, the acid value of the castor oil is preferably ≤2.0 mgKOH / g, more preferably ≤1.5 mgKOH / g. The hydroxyl value of the castor oil is preferably 154-170 mgKOH / g, more preferably 156-167 mgKOH / g.

[0043] In this invention, the block composition preferably includes one or more of cashew nut shell oil Mannich polyol, 1,3,5-tris(2-hydroxyethyl)cyanuric acid, tetrahydroxyethyl ethylenediamine, hydroxyethyl hexahydrotriazine, and N,N,N,N-tetra(2-hydroxypropyl)p-phenylenediamine.

[0044] In this invention, the cashew nut shell oil Mannich polyol is a cashew nut shell oil bio-based polyol synthesized by the Mannich reaction of cashew nut shell oil, formaldehyde and diethanolamine.

[0045] In this invention, the preferred method for preparing N,N,N,N-tetra(2-hydroxypropyl)-p-phenylenediamine includes: adding 1085g (10mol) of p-phenylenediamine and 1000mL of toluene to a high-pressure reactor equipped with a thermometer, mechanical stirrer, cooling and heating facilities; stirring and heating to 30-55°C under N2 protection; gradually pressing 2382g (41mol) of propylene oxide into the reactor; completing the addition within 4 hours; continuing the reaction for 6 hours; waiting for the pressure in the reactor to decrease; raising the temperature to 100°C and continuing the reaction for 4 hours; then turning on the vacuum pump to remove low-boiling-point substances under negative pressure to obtain 3237.7g of N,N,N,N-tetra(2-hydroxypropyl)-p-phenylenediamine, with a yield of 95.1%.

[0046] In this invention, the hydroxyl value of the cashew nut shell oil Mannich polyol is preferably 240–480 mg KOH / g, and in the examples it can be 430 mg KOH / g. The hydroxyl value of the 1,3,5-tris(2-hydroxyethyl)cyanuric acid is preferably 630–650 mg KOH / g, and in the examples it can be 644 mg KOH / g. The hydroxyl value of the tetrahydroxyethylethylenediamine is preferably 940–955 mg KOH / g. The hydroxyl value of the hydroxyethyl hexahydrotriazine is preferably 760–770 mg KOH / g. The hydroxyl value of the N,N,N,N-tetra(2-hydroxypropyl)p-phenylenediamine is preferably 650–665 mg KOH / g, and in the examples it can be 659 mg KOH / g. This invention uses the aforementioned high hydroxyl value, multifunctionality, and thermal stability block copolymers as raw materials to prepare block castor oil-based polyester polyols. The resulting bio-based polyurethane materials, prepared from these block castor oil-based polyester polyols, exhibit excellent chemical resistance, heat resistance, flexibility, and adhesion. The preferred mass ratio of castor oil to block copolymers is 45–75:15–40, more preferably 50–70:18–35, and even more preferably (2.4–5):1. In the examples, the ratios can be 30:12.5, 30:8.5, 30:6, 30:12, or 30:11. The mass ratio of castor oil to the catalyst is preferably 45–75:0.01–0.08, more preferably 50–70:0.02–0.05, further preferably (1000–3500):1, and most preferably (1200–3000):1. In the embodiments, it can be 30:0.01, 30:0.015, 30:0.02, or 30:0.025. In this invention, the mixing is preferably carried out in a protective gas atmosphere, which preferably includes nitrogen and / or a rare gas, wherein the rare gas can be argon, and in the embodiments, the protective gas can be nitrogen.

[0047] In this invention, the transesterification reaction preferably includes a first-stage transesterification reaction and a second-stage transesterification reaction performed sequentially. The temperature of the first-stage transesterification reaction is preferably 60–170°C, more preferably 70–160°C, and even more preferably 80–150°C; in the embodiment, it can be 110°C. The duration of the first-stage transesterification reaction is preferably 8–15 h, more preferably 9–13 h, and even more preferably 10–12 h; in the embodiment, it can be 11 h. The heating rate to the temperature of the first-stage transesterification reaction is preferably 15–25°C / h, more preferably 25°C / h; in the embodiment, it can be 20°C / h. The first-stage transesterification reaction is preferably carried out in a protective gas atmosphere, which preferably includes nitrogen and / or a rare gas, wherein the rare gas can be argon; in the embodiment, the protective gas can be nitrogen.

[0048] In this invention, the temperature of the second-stage transesterification reaction is preferably 60–170°C, more preferably 70–160°C. The time of the second-stage transesterification reaction is preferably 1–8 h, more preferably 3–7 h, and even more preferably 3–6 h; in the examples, it can be 4 h. The second-stage transesterification reaction is preferably carried out under vacuum conditions, with a vacuum degree preferably -0.1 to -0.085 MPa, more preferably -0.1 to -0.09 MPa.

[0049] In this invention, after the transesterification reaction is completed, a transesterification reaction solution is obtained. Preferably, the invention further includes: breaking the vacuum of the transesterification reaction solution, heating it, then removing impurities under vacuum conditions, and cooling it to obtain the block castor oil-based polyester polyol. In this invention, the gas used to break the vacuum is preferably nitrogen and / or a rare gas, wherein the rare gas can be argon; in the embodiments, nitrogen is used to break the vacuum. The heating rate is preferably 20–30 °C / h, more preferably 25 °C / h. The impurity removal temperature is preferably 130–220 °C, more preferably 150–210 °C. The impurity removal time is preferably 2–6 h, more preferably 3–5 h, and in the embodiments, it can be 4 h. The vacuum degree for impurity removal is preferably -0.1 to -0.09 MPa, more preferably -0.1 to -0.095 MPa.

[0050] The transesterification reaction product obtained in this invention contains block castor oil-based polyester polyol, diglyceride, and catalyst. The block castor oil-based polyester polyol, diglyceride, and catalyst in the transesterification reaction product obtained in this invention do not need to be separated. This invention uses the block castor oil-based polyester polyol, diglyceride, and catalyst as the block castor oil-based polyester polyol product prepared in this invention for the preparation of bio-based polyurethane materials.

[0051] The present invention provides a block castor oil-based polyester polyol prepared by the preparation method described in the above technical solution.

[0052] The block castor oil-based polyester polyol product provided by the present invention is preferably a mixture comprising block castor oil-based polyester polyol, diglyceride and catalyst.

[0053] In this invention, the hydroxyl value of the block castor oil-based polyester polyol is preferably 180–400 mg KOH / g, and in the examples it can be 242 mg KOH / g. The acid value of the block castor oil-based polyester polyol is preferably ≤1.5 mg KOH / g, and in the examples it can be 0.5 mg KOH / g.

[0054] In this invention, the viscosity of the block castor oil-based polyester polyol at 25°C is preferably 600 mPa·s to 4000 mPa·s, and in the examples it can be 980 mPa·s, 1380 mPa·s, 860 mPa·s or 1080 mPa·s.

[0055] In this invention, the average relative molecular mass of the block castor oil-based polyester polyol is 500 g / mol to 850 g / mol, and in the examples it can be 662 g / mol, 596 g / mol, 655 g / mol or 635 g / mol.

[0056] This invention provides a bio-based polyurethane material, wherein the polyester polyol segments constituting the bio-based polyurethane material include the block castor oil-based polyester polyol described in the above technical solution.

[0057] The raw materials for preparing the bio-based polyurethane material provided by this invention preferably include polyester polyol and isocyanate, wherein the polyester polyol preferably includes the block castor oil-based polyester polyol described in the above technical solution. The isocyanate is preferably diphenylmethane diisocyanate.

[0058] In this invention, the isocyanate index (R value) for preparing the bio-based polyurethane material is preferably 1.1.

[0059] This invention provides a method for preparing the bio-based polyurethane material described in the above-mentioned technical solution, preferably comprising the following steps: mixing the block castor oil-based polyester polyol and isocyanate, degassing, and then curing to obtain the bio-based polyurethane material. The curing preferably includes sequentially performing a first-stage curing and a second-stage curing. The first-stage curing temperature is preferably room temperature, and the time is preferably 5–7 hours. The second-stage curing temperature is preferably 45–55°C, and the time is preferably 12–16 hours.

[0060] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0061] The preparation method of the branched organic urea catalyst with the structure shown in Formula I used in the following examples is as follows:

[0062] Under nitrogen protection, 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (35.4 g, 100 mmol) and anhydrous tetrahydrofuran (100 mL) were added to a 500 mL three-necked flask and mixed thoroughly. Under vigorous stirring, a mixed solution of m-toluene isocyanate (47.9 g, 360 mmol) and anhydrous tetrahydrofuran (150 mL) was slowly added dropwise. After reacting at room temperature for 20 h, the mixture was slowly heated to reflux for 10 h. The tetrahydrofuran was then evaporated to dryness under vacuum. 300 mL of diethyl ether was then added, and the mixture was stirred for 2 h. After washing, filtering, and drying, a white solid (71 g) of branched organic urea catalyst was obtained.

[0063] Example 1:

[0064] 30 kg of castor oil was added to a dry stainless steel reactor filled with nitrogen. 0.010 kg of branched organic urea catalyst and 12.5 kg of cashew nut shell oil Mannich polyol block with a hydroxyl value of 430 mg KOH / g were added to the reactor. The reactor was heated to 110 °C at a rate of 20 °C / h and the reaction was maintained for 11 h. Then, the reactor was evacuated and the reaction was continued for 4 h under a vacuum of -0.09 MPa.

[0065] After purging with nitrogen to break the vacuum, the reactor was heated to 210°C at a rate of 25°C / h, and impurities were removed under a high vacuum of -0.1MPa for 4 hours. After cooling, block castor oil-based polyester polyol was obtained.

[0066] The block castor oil-based polyester polyol prepared in this embodiment has a hydroxyl value of 242 mg KOH / g, an acid value of 0.5 mg KOH / g, a viscosity (25℃) of 980 mPa·s, and an average relative molecular mass of 662 g / mol.

[0067] Example 2:

[0068] 30 kg of castor oil was added to a dry stainless steel reactor filled with nitrogen. 0.015 kg of branched organic urea catalyst and 8.5 kg of 1,3,5-tris(2-hydroxyethyl)cyanuric acid block copolymer with a hydroxyl value of 644 mg KOH / g were added to the reactor. The reactor was heated to 110 °C at a rate of 20 °C / h and held for 11 h. Then, the reactor was evacuated and the reaction was continued for 4 h under a vacuum of -0.09 MPa.

[0069] After purging with nitrogen to break the vacuum, the reactor was heated to 210°C at a rate of 25°C / h, and impurities were removed under a high vacuum of -0.1MPa for 4 hours. After cooling, block castor oil-based polyester polyol was obtained.

[0070] The block castor oil-based polyester polyol prepared in this embodiment has a hydroxyl value of 270 mg KOH / g, an acid value of 0.4 mg KOH / g, a viscosity (25℃) of 1380 mPa·s, and an average relative molecular mass of 596 g / mol.

[0071] Example 3:

[0072] 30 kg of castor oil was added to a dry stainless steel reactor filled with nitrogen. 0.015 kg of branched organic urea catalyst, 6 kg of cashew nut shell oil Mannich polyol with a hydroxyl value of 430 mg KOH / g, and 4.5 kg of 1,3,5-tris(2-hydroxyethyl)cyanuric acid block copolymer with a hydroxyl value of 644 mg KOH / g were added to the reactor. The reactor was heated to 110°C at a rate of 20°C / h and held for 11 h. Then, a vacuum was drawn and the reaction was continued for 4 h under a vacuum of -0.09 MPa.

[0073] After purging with nitrogen to break the vacuum, the reactor was heated to 210°C at a rate of 25°C / h, and impurities were removed under a high vacuum of -0.1MPa for 4 hours. After cooling, block castor oil-based polyester polyol was obtained.

[0074] The block castor oil-based polyester polyol prepared in this embodiment has a hydroxyl value of 256 mg KOH / g, an acid value of 0.5 mg KOH / g, a viscosity (25℃) of 1160 mPa·s, and an average relative molecular mass of 627 g / mol.

[0075] Example 4:

[0076] 30 kg of castor oil was added to a dry stainless steel reactor filled with nitrogen. 0.025 kg of branched organic urea catalyst and 11 kg of N,N,N,N-tetra(2-hydroxypropyl)-p-phenylenediamine block with a hydroxyl value of 659 mg KOH / g were added to the reactor. The reactor was heated to 110 °C at a rate of 20 °C / h and held for 11 h. Then, a vacuum was drawn and the reaction was continued for 4 h under a vacuum of -0.09 MPa.

[0077] After purging with nitrogen to break the vacuum, the reactor was heated to 210°C at a rate of 25°C / h, and impurities were removed under a high vacuum of -0.1MPa for 4 hours. After cooling, block castor oil-based polyester polyol was obtained.

[0078] The block castor oil-based polyester polyol prepared in this embodiment has a hydroxyl value of 296 mg KOH / g, an acid value of 0.5 mg KOH / g, a viscosity (25℃) of 1080 mPa·s, and an average relative molecular mass of 635 g / mol.

[0079] Comparative Example 1 (using branched organic urea catalyst, reducing the amount of nitrogen-containing block catalyst added):

[0080] 30 kg of castor oil was added to a dry stainless steel reactor filled with nitrogen. 0.015 kg of branched organic urea catalyst, 3.2 kg of cashew nut shell oil Mannich polyol with a hydroxyl value of 430 mg KOH / g, and 2.1 kg of 1,3,5-tris(2-hydroxyethyl)cyanuric acid block copolymer with a hydroxyl value of 644 mg KOH / g were added to the reactor. The reactor was heated to 110 °C at a rate of 20 °C / h and held for 11 h. Then, a vacuum was applied and the reaction was continued for 4 h under a vacuum of -0.09 MPa.

[0081] After purging with nitrogen to break the vacuum, the reactor was heated to 210°C at a rate of 25°C / h, and impurities were removed under a high vacuum of -0.1MPa for 4 hours. After cooling, block castor oil-based polyester polyol was obtained.

[0082] The block castor oil-based polyester polyol prepared in this comparative example has a hydroxyl value of 215 mg KOH / g, an acid value of 0.4 mg KOH / g, a viscosity (25℃) of 930 mPa·s, and an average relative molecular mass of 730 g / mol.

[0083] Comparative Example 2 (using a conventional catalyst with reduced nitrogen-containing block composition):

[0084] 30 kg of castor oil was added to a dry stainless steel reactor filled with nitrogen. 0.015 kg of dibutyltin dilaurate catalyst, 3.2 kg of cashew nut shell oil Mannich polyol with a hydroxyl value of 430 mg KOH / g, and 2.1 kg of 1,3,5-tris(2-hydroxyethyl)cyanuric acid block copolymer with a hydroxyl value of 644 mg KOH / g were added to the reactor. The reactor was heated to 110°C at a rate of 20°C / h and held for 11 h. Then, a vacuum was applied and the reaction was continued for 4 h under a vacuum of -0.09 MPa.

[0085] After purging with nitrogen to break the vacuum, the reactor was heated to 210°C at a rate of 25°C / h, and impurities were removed under a high vacuum of -0.1MPa for 4 hours. After cooling, block castor oil-based polyester polyol was obtained.

[0086] The block castor oil-based polyester polyol prepared in this comparative example has a hydroxyl value of 213 mg KOH / g, an acid value of 0.5 mg KOH / g, a viscosity (25℃) of 940 mPa·s, and an average relative molecular mass of 726 g / mol.

[0087] Application example:

[0088] The performance of the block castor oil-based polyester polyols prepared in Examples 1-4 and Comparative Examples 1-2 was tested. The test method was as follows: nitrogen gas was introduced into the reaction bottle, and the block castor oil-based polyester polyols prepared in Examples 1-4 and Comparative Examples 1-2 were mixed with diphenylmethane diisocyanate curing agent at an R value of 1.1 and stirred evenly. After removing air bubbles by vacuuming, an adhesion test was conducted. Then, the mixture was poured into the corresponding test molds and cured at room temperature for 5-7 hours. The reaction was then continued in a drying oven at 45-55°C for 12-16 hours. After cooling and demolding, the corresponding bio-based polyurethane materials were obtained. The sample specifications conformed to GB / T 1040.1-2018 and GB / T2406.2-2009. The oxygen index of the samples was tested using an oxygen index meter, and the tensile strength of the bio-based polyurethane materials was tested using a WAW-C universal testing machine. The test results are shown in Table 1.

[0089] Table 1. Performance test results of Examples 1-5 and Comparative Examples 1-2

[0090]

[0091] As shown in Table 1, the bio-based polyurethane materials prepared from castor oil-based polyester polyols in Examples 1-4 have superior chemical resistance, heat resistance, flexibility, and adhesion, and also have high flame retardancy. A comparison of the oxygen index data of Comparative Example 1 and Comparative Example 2 shows that the branched organic urea catalyst has certain flame retardancy.

[0092] As can be seen from the above embodiments, the branched organic urea catalyst used in this invention has advantages such as low reaction temperature, high catalytic activity, small addition amount, metal-free, flame retardant, and no impact on polyurethane performance. Containing a branched, cyclic stereostructure, it exhibits a suitable steric hindrance effect, enabling it to catalyze a directional, single transesterification reaction between the block copolymer and castor oil, thereby obtaining diglyceride and castor oil-based block copolymer polyester polyol molecular structures. This significantly reduces the formation of small molecules such as glycerol and monoglycerides, improving the performance of the polyurethane prepared from the castor oil-based block copolymer polyester polyol.

[0093] This invention involves adding nitrogen-containing or nitrogen-heterocyclic block copolymers and branched organic urea catalysts to castor oil for selective transesterification, followed by impurity removal and dehydration under high vacuum and heating. By introducing castor oil fatty acid segments into the block copolymer molecular structure, a bio-based branched, multifunctional, low-molecular-weight, and highly reactive polyester polyol is synthesized, containing both nitrogen-containing or nitrogen-heterocyclic polyester segments and long side-chain segments of castor oil fatty acids.

[0094] The block copolymers cashew nut shell oil Mannich polyol, 1,3,5-tris(2-hydroxyethyl)cyanuric acid, hydroxyethyl hexahydrotriazine, tetrahydroxyethyl ethylenediamine, and N,N,N,N-tetra(2-hydroxypropyl)p-phenylenediamine used in this invention are all small molecule raw materials with high hydroxyl value, multifunctionality, and good thermal stability containing nitrogen or nitrogen heterocycles. The resulting castor oil-based block polyester polyol has excellent chemical resistance, heat resistance, flexibility, and adhesion.

[0095] The method for preparing castor oil-based block polyester polyols of the present invention is simple, the raw materials are widely available and readily available, and it is safer and more environmentally friendly to humans and nature, and has broad application prospects.

[0096] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing a block castor oil-based polyester polyol, characterized in that, Includes the following steps: Castor oil, a catalyst, and a block copolymer are mixed and subjected to transesterification to obtain the block castor oil-based polyester polyol. The block copolymer is one or more of cashew nut shell oil Mannich polyol, 1,3,5-tris(2-hydroxyethyl)cyanuric acid, and N,N,N,N-tetra(2-hydroxypropyl)-p-phenylenediamine. The cashew nut shell oil Mannich polyol has a hydroxyl value of 240-480 mg KOH / g, the 1,3,5-tris(2-hydroxyethyl)cyanuric acid has a hydroxyl value of 630-650 mg KOH / g, and the N,N,N,N-tetra(2-hydroxypropyl)-p-phenylenediamine has a hydroxyl value of 650-665 mg KOH / g. The mass ratio of castor oil to the block copolymer is 45-75:15-40. The catalyst is a branched organic urea compound, which has the structure shown in Formula I: Equation I.

2. The preparation method according to claim 1, characterized in that, The preparation method of the branched organic urea compound includes the following steps: In a protective gas atmosphere, 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, an organic solvent, and m-toluene isocyanate were mixed and reacted to obtain the branched organic urea compound.

3. The preparation method according to claim 1, characterized in that, The castor oil has an acid value ≤2.0 mgKOH / g and a hydroxyl value of 154~170 mgKOH / g.

4. The preparation method according to claim 1, characterized in that, The mass ratio of castor oil to catalyst is 45~75:0.01~0.

08.

5. The preparation method according to any one of claims 1, 3, and 4, characterized in that, The transesterification reaction includes a first-stage transesterification reaction and a second-stage transesterification reaction performed sequentially. The first-stage transesterification reaction is carried out at a temperature of 60~170 °C for 8~15 h in a protective gas atmosphere. The second-stage transesterification reaction is carried out at a temperature of 60~170 °C for 1~8 h in a vacuum atmosphere with a vacuum degree of -0.1~-0.085 MPa. After the transesterification reaction is completed, a transesterification reaction solution is obtained. After obtaining the transesterification reaction solution, the process further includes: breaking the vacuum of the transesterification reaction solution and heating it, then removing impurities under vacuum conditions, and cooling it to obtain the block castor oil-based polyester polyol. The impurity removal temperature is 130~220 ℃, the time is 2~6 h, and the vacuum degree is -0.1~-0.09 MPa.

6. The block castor oil-based polyester polyol prepared by the preparation method according to any one of claims 1 to 5.

7. The block castor oil-based polyester polyol according to claim 6, characterized in that, The block castor oil-based polyester polyol has a hydroxyl value of 180~400 mg KOH / g and an acid value of ≤1.5 mg KOH / g.

8. A bio-based polyurethane material, characterized in that, The polyester polyol segments constituting the bio-based polyurethane material include the block castor oil-based polyester polyols as described in claim 6 or 7.

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