Preparation method of highly flame-retardant phosphazene-based polyether polyols
Using a polyhydroxyphosphazene derivative generated by the reaction of hexachlorocyclotriphosphazene with water as an initiator, the ring-opening polymerization of propylene oxide can be directly initiated, solving the problems of complex processes and high costs in existing technologies. This enables the preparation of highly efficient flame-retardant polyether polyols, which are suitable for high-end applications.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHANDONG INOV NEW MATERIALS CO LTD
- Filing Date
- 2025-12-29
- Publication Date
- 2026-05-26
Smart Images
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Abstract
Description
Technical Field
[0001] This invention relates to the field of polyurethane production technology, specifically to a method for preparing highly flame-retardant phosphazene-based polyether polyols. Background Technology
[0002] Flame-retardant polyether polyols are key raw materials for synthesizing polyurethane materials. Their performance directly determines whether polyurethane products can meet the stringent requirements of downstream applications. In scenarios such as sealing battery packs for new energy vehicles and thermal insulation of building exterior walls, polyurethanes need to possess excellent flame retardancy, stability, and mechanical properties. In the current market, traditional flame-retardant polyethers either fail to meet standards due to insufficient flame retardancy efficiency or are unsuitable for high-end scenarios due to the difficulty in balancing performance. Therefore, developing flame-retardant polyether synthesis technology that combines high-efficiency flame retardancy, long-term stability, and low cost has become a core demand for the industry to break through development bottlenecks.
[0003] Patent CN111423556A discloses a reactive nitrogen-phosphorus polyol grafting method for highly flame-retardant polyurethane. The core process consists of three steps: first, p-hydroxybenzaldehyde and hexachlorocyclotriphosphazene undergo a substitution reaction to produce terminal aldehyde-terminated cyclotriphosphazene; then, it undergoes a Schiff base condensation reaction with melamine to generate an amino-terminated melamine-cyclotriphosphazene polymer; finally, it undergoes a ring-opening reaction with propylene oxide to obtain a melamine polyol-cyclotriphosphazene polymer. This polymer combines the synergistic flame retardancy of nitrogen and phosphorus with the branching effect of polyols, and can participate in the main chain polymerization of polyether polyols and isocyanate monomers, giving the polyurethane excellent flame retardancy. However, the process has significant limitations: it requires three steps of "substitution-condensation-ring-opening," each step of which requires extremely high precision in environmental and parameter control. Slight fluctuations in humidity and temperature can lead to residual aldehyde groups or uneven molecular weight distribution. Moreover, compared to a one-step grafting process, the scrap rate is higher, increasing the difficulty and cost risk of industrial production management.
[0004] Currently, the industry has not yet developed a technical solution for "directly initiating the ring-opening polymerization of propylene oxide using the polyhydroxy product from the direct reaction of hexachlorocyclotriphosphazene and water as an initiator." However, the phosphazene intermediate generated from the reaction of hexachlorocyclotriphosphazene and water naturally contains multiple active hydroxyl groups. This not only fully retains the flame-retardant properties of high phosphorus and nitrogen content but can also be directly used as an initiator in the construction of the polyether backbone, fundamentally solving the bottlenecks of existing technologies such as "complex processes, high costs, and poor flame-retardant durability." Therefore, exploring this novel synthetic route has become a core direction for the industry to meet the flame-retardant needs of high-end applications. Summary of the Invention
[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a method for preparing highly flame-retardant phosphazene-based polyether polyols. This method introduces nitrogen, phosphorus, and chlorine groups during the synthesis of the polyether, "embedding" flame-retardant elements into the main chain and side chains of the polyether polyol molecule, achieving inherent flame retardancy and reducing the migration and combustion hazards of flame retardants. It also allows for precise control of the polyether structure, optimizing product performance, and improving compatibility with downstream systems, balancing flame retardancy and mechanical properties, and broadening application scenarios.
[0006] This invention is achieved using the following technical solution:
[0007] The preparation method of the high flame-retardant phosphazene-based polyether polyol includes the following steps:
[0008] (a) In the presence of an acid-binding agent, hexachlorocyclotriphosphazene undergoes a nucleophilic substitution reaction with water to generate a polyhydroxyl-containing phosphazene derivative as an initiator;
[0009] (b) Under the action of a catalyst, the phosphazene derivative initiator obtained in step (a), or a mixed initiator composed of the phosphazene derivative and other small molecule polyols, is used to initiate the ring-opening polymerization of propylene oxide to obtain the highly flame-retardant phosphazene-based polyether polyol.
[0010] In step (a), the molar ratio of water to hexachlorocyclotriphosphazene is (3-6):1.
[0011] The acid-binding agent in step (a) is triethylamine or anhydrous sodium carbonate; and the molar ratio of the acid-binding agent to water is (1.1-1.2):1.
[0012] Step (a) is carried out in an organic solvent, wherein the organic solvent is anhydrous acetonitrile or tetrahydrofuran, and the amount of solvent used is 5-10 times the mass of hexachlorocyclotriphosphazene.
[0013] The other small molecule polyols in step (b) are selected from one or more of 1,4-butanediol, ethylene glycol, diethylene glycol, glycerol, propylene glycol, diethanolamine, and hexanediol.
[0014] The catalyst in step (b) is an alkaline catalyst, selected from one or more of triethylamine, N,N-dimethylbenzylamine, and dimethylcyclohexylamine. The amount of alkaline catalyst added is 0.8-1.0 wt. of the total amount of mixed initiator and total amount of propylene oxide.
[0015] The ring-opening polymerization in step (b) includes:
[0016] First polymerization stage: Polymerization is carried out by adding a portion of propylene oxide at 80-85℃ and 0.1-0.4MPa pressure;
[0017] Second polymerization stage: Heat to 100-110℃ and add the remaining propylene oxide under a pressure of 0.1-0.4MPa to continue polymerization.
[0018] The method for preparing the highly flame-retardant phosphazene-based polyether polyol further includes, after the second polymerization stage, a step of bubbling with nitrogen at a pressure of -0.08 MPa to -0.1 MPa to remove residual small molecule substances.
[0019] The reaction in step (a) is carried out at 60-90°C for 6-12 hours.
[0020] Specifically, the preparation method of highly flame-retardant phosphazene-based polyether polyol includes the following steps:
[0021] (1) Add hexachlorocyclotriphosphazene and solvent to a three-necked flask, replace with nitrogen and stir until clear, slowly add a mixture of deionized water and acid-binding agent, heat to 60-90℃ after the addition is complete, keep the temperature for 6-12h, filter to remove the generated salt, remove the solvent by vacuum distillation to obtain hydroxyphosphazene derivative.
[0022] (2) Add hydroxyphosphazene derivatives and other small molecule polyols as mixed initiators to the reactor, and polymerize with propylene oxide under the action of an alkaline catalyst. The polymerization temperature of the first stage is 80-85℃, the polymerization pressure is 0.1-0.4MPa, and the internal pressure is 1-2h after the feed is completed to obtain phosphazene-based polyether polyol intermediate.
[0023] (3) Heat to 100-110℃, maintain pressure at 0.1-0.4MPa, add propylene oxide again, and when the reaction pressure remains basically unchanged after the feed is completed, pressurize to 0.2-0.3MPa and react for 2-3 hours. Use nitrogen to bubble and remove residual small molecules to obtain high flame retardant phosphazene polyether polyol.
[0024] In step (1), the droplet acceleration of the mixture of deionized water and acid-binding agent is controlled at 1-2 drops / second.
[0025] In step (3), nitrogen gas is bubbled to maintain the pressure of the reactor at -0.08MPa to -0.1MPa.
[0026] Compared with the prior art, the beneficial effects of the present invention are:
[0027] (1) The hydrolysis products of hexachlorocyclotriphosphazene contain nitrogen, phosphorus and chlorine flame retardant elements. As an initiator, it can be inserted into the polyether backbone to avoid the migration problem of traditional external flame retardants, significantly improve the limiting oxygen index of polyether products, reduce the release of smoke and toxic gases during combustion, and be suitable for high-risk scenarios such as building insulation and electronic packaging.
[0028] (2) The hydrolysis product is a multifunctional hydroxy compound, which can precisely control the initiation site of propylene oxide polymerization, flexibly customize the functionality, molecular weight distribution and branching degree of polyether, and specifically improve the key properties of downstream polyurethane products such as compressive strength and dimensional stability.
[0029] (3) The viscosity and hydroxyl value of the synthesized polyether are easy to control, and it has good miscibility with polyether components such as isocyanate and foaming agent; and the phosphorus and chlorine groups in the molecule can work synergistically with antioxidants and other additives to ensure flame retardancy while avoiding loss of mechanical properties, thus broadening the application scenarios of high-end polyurethane.
[0030] (4) There is no need to convert hexachlorocyclotriphosphazene into complex derivatives. Its hydrolysis product can be used directly as the starting agent, which shortens the reaction steps. The polymerization process has fewer side reactions and higher product purity, which reduces subsequent purification processes and lowers production energy consumption and costs. Detailed Implementation
[0031] To make the objectives and technical solutions of this invention clearer, the invention will be further described in detail below. Unless otherwise specified, the raw materials used in the embodiments and comparative examples are all commercially available products.
[0032] Hexachlorocyclotriphosphazene, a commercially available product of Wuhan Camic Technology Co., Ltd.
[0033] Example 1
[0034] The preparation method of the high flame-retardant phosphazene-based polyether polyol includes the following steps:
[0035] (1) Using a three-necked flask equipped with a mechanical stirrer, reflux condenser, constant pressure dropping funnel and nitrogen protection, 347.66 g of hexachlorocyclotriphosphazene and 1738.3 g of anhydrous acetonitrile were added to the three-necked flask. After nitrogen purging, the mixture was stirred until clear. A mixture of 54 g of deionized water and 333.9 g of triethylamine was added dropwise at a rate of 1 drop / second. After the addition was completed, the temperature was raised to 60 °C and the reaction was maintained for 6 h. The generated salt was removed by filtration, and the solvent and trace amounts of water were removed by vacuum distillation to obtain the hydroxyphosphazene derivative. The intermediate was chemically titrated and its hydroxyl value was determined to be 530 mg KOH / g.
[0036] (2) 292.16g of hydroxyphosphazene derivative, 215g of 1,4-butanediol, and 52g of ethylene glycol were added to the reactor as a mixed initiator. 6g of triethylamine and 5g of N,N-dimethylbenzylamine were used as the alkaline catalyst. 226.5g of propylene oxide was pre-dropped. The polymerization temperature was 82.5±2.5℃, and the polymerization pressure was 0.25±0.15MPa. After the feed was completed, the internal pressure was maintained for 1 hour to obtain a phosphazene-based polyether polyol intermediate.
[0037] (3) Raise the temperature inside the autoclave to 105±5℃, maintain the pressure at 0.25±0.15MPa, add 528.6g of propylene oxide again, and after the feeding is completed, when the reaction pressure is basically unchanged, pressurize to 0.2MPa, react for 2h, and remove residual small molecules by bubbling with nitrogen to obtain high flame retardant phosphazene polyether polyol.
[0038] Example 2
[0039] The preparation method of the high flame-retardant phosphazene-based polyether polyol includes the following steps:
[0040] (1) Using a three-necked flask equipped with a mechanical stirrer, reflux condenser, constant pressure dropping funnel and nitrogen protection, 347.66 g of hexachlorocyclotriphosphazene and 2607.45 g of tetrahydrofuran were added to the three-necked flask. After nitrogen replacement, the mixture was stirred until clear. A mixture of 81 g of deionized water and 548.5 g of anhydrous sodium carbonate was added dropwise at a rate of 1.5 drops / second. After the addition was completed, the temperature was raised to 75 °C and the reaction was maintained at this temperature for 9 h. The generated salt was removed by filtration, and the solvent and trace amounts of water were removed by vacuum distillation to obtain the hydroxyphosphazene derivative. The intermediate was chemically titrated, and its hydroxyl value was determined to be 956 mg KOH / g.
[0041] (2) Add 264.4g of hydroxyphosphazene derivative and 215g of diethylene glycol to the reactor as a mixed initiator. Use 9.5g of N,N-dimethylbenzylamine as the alkaline catalyst. Pre-drop 213g of propylene oxide. The polymerization temperature is 82.5±2.5℃ and the polymerization pressure is 0.25±0.15MPa. After the feed is completed, the internal pressure is maintained for 1.5h to obtain phosphazene-based polyether polyol intermediate.
[0042] (3) Raise the temperature inside the autoclave to 105±5℃, maintain the pressure at 0.25±0.15MPa, add 497g of propylene oxide again, and after the feeding is completed, when the reaction pressure is basically unchanged, pressurize to 0.3MPa and react for 3h. Nitrogen gas is bubbled to remove residual small molecules to obtain high flame retardant phosphazene polyether polyol.
[0043] Example 3
[0044] The preparation method of the high flame-retardant phosphazene-based polyether polyol includes the following steps:
[0045] (1) Using a three-necked flask equipped with a mechanical stirrer, reflux condenser, constant pressure dropping funnel and nitrogen protection, 347.66 g of hexachlorocyclotriphosphazene and 3476.6 g of anhydrous acetonitrile were added to the three-necked flask. After nitrogen purging, the mixture was stirred until clear. A mixture of 108 g of deionized water and 728.56 g of triethylamine was added dropwise at a rate of 2 drops / second. After the addition was completed, the temperature was raised to 90 °C and the reaction was maintained for 12 h. The generated salt was removed by filtration, and the solvent and trace amounts of water were removed by vacuum distillation to obtain the hydroxyphosphazene derivative. The intermediate was chemically titrated and its hydroxyl value was determined to be 1356 mg KOH / g.
[0046] (2) 236.66g of hydroxyphosphazene derivative, 143g of glycerol, and 30g of propylene glycol were added to the reactor as a mixed initiator. 9g of dimethylcyclohexylamine was used as the alkaline catalyst, and 195g of propylene oxide was pre-dropped. The polymerization temperature was 82.5±2.5℃, the polymerization pressure was 0.25±0.15MPa, and the internal pressure was maintained for 2 hours after the feed was completed to obtain a phosphazene-based polyether polyol intermediate.
[0047] (3) Raise the temperature inside the autoclave to 105±5℃, maintain the pressure at 0.25±0.15MPa, add 456g of propylene oxide again, and after the feeding is completed, when the reaction pressure is basically unchanged, pressurize to 0.25MPa and react for 2.5h. Nitrogen gas is bubbled to remove residual small molecules to obtain high flame retardant phosphazene polyether polyol.
[0048] Comparative Example 1
[0049] (1) Using a three-necked flask equipped with a mechanical stirrer, reflux condenser, constant pressure dropping funnel and nitrogen protection, 347.66 g of hexachlorocyclotriphosphazene and 2607.45 g of tetrahydrofuran were added to the three-necked flask. After nitrogen replacement, the mixture was stirred until clear. A mixture of 18 g of deionized water and 121.9 g of anhydrous sodium carbonate was added dropwise at a rate of 1.5 drops / second. After the addition was completed, the temperature was raised to 75 °C and the reaction was maintained at this temperature for 9 h. The generated salt was removed by filtration, and the solvent and trace amounts of water were removed by vacuum distillation to obtain the hydroxyphosphazene derivative. The intermediate was chemically titrated, and its hydroxyl value was determined to be 180 mg KOH / g.
[0050] (2) Add 329.2g of hydroxyphosphazene derivative and 295g of glycerol to the reactor as a mixed initiator, use 12g of N,N-dimethylbenzylamine as the alkaline catalyst, pre-drop 256g of propylene oxide, the polymerization temperature is 82.5±2.5℃, the polymerization pressure is 0.25±0.15MPa, and the internal pressure is maintained for 1.5h after the feeding is completed to obtain phosphazene-based polyether polyol intermediate.
[0051] (3) Raise the temperature inside the autoclave to 105±5℃, maintain the pressure at 0.25±0.15MPa, add 597g of propylene oxide again, and after the feeding is completed, when the reaction pressure is basically unchanged, pressurize to 0.3MPa and react for 3h. Nitrogen gas is bubbled to remove residual small molecules to obtain high flame retardant phosphazene polyether polyol.
[0052] Comparative Example 2
[0053] (1) Add 100g glycerol and 200g propylene glycol to the reactor as a mixed initiator, use 10g dimethylcyclohexylamine as the alkaline catalyst, and pre-drop 265g propylene oxide. The polymerization temperature is 82.5±2.5℃, the polymerization pressure is 0.25±0.15MPa, and the internal pressure is maintained for 2h after the feed is completed to obtain a polyether polyol intermediate.
[0054] (2) Raise the temperature inside the autoclave to 105±5℃, maintain the pressure at 0.25±0.15MPa, add 619g of propylene oxide again, and after the feeding is completed, when the reaction pressure is basically unchanged, pressurize to 0.25MPa and react for 2.5h. Nitrogen gas is bubbled to remove residual small molecules to obtain polyether polyol.
[0055] The hydroxyl value and viscosity test results of the synthesized polyether polyols are shown in Table 1 below:
[0056] Table 1. Test results of sample indicators for Examples 1-3 and Comparative Examples 1-2
[0057]
[0058] The polyether polyols synthesized in Examples 1-3 and Comparative Examples 1-2 were formulated into composite materials according to the formulations and proportions in Table 2 to obtain component A. The catalyst PC-8 was a commercially available product of Wanhua Chemical (Yantai) Sales Co., Ltd., the silicone oil S36 was a commercially available product of Shanghai Maihao New Material Technology Co., Ltd., and component B PM200 was a commercially available product of Wanhua Chemical (Yantai) Sales Co., Ltd. After mixing component A and component B in a 1:1 ratio and foaming, rigid foam polyether polyol samples were obtained. Table 2 shows the proportions of component A in Examples 1-3 and Comparative Examples 1-2 (by mass).
[0059] Table 2. Proportioning of Material A in Examples 1-3 and Comparative Examples 1-2
[0060]
[0061] After the A and B materials obtained according to the formula in Table 2 above are mixed evenly, a foaming test is carried out to verify the compressive strength, limiting oxygen index and self-extinguishing time of the foam. The relevant performance test results are shown in Table 3.
[0062] Mechanical performance testing: The cured polyurethane foams of Examples 1-3, Comparative Example 1 and Comparative Example 2 were cut into 50mm×50mm×50mm cubes and subjected to compression performance testing.
[0063] Limiting oxygen index test: The oxygen index of the samples was tested using a WK5155A digital display oxygen index meter according to the GB-T2406-1993 standard. The cured polyurethane foam of Examples 1-3, Comparative Example 1 and Comparative Example 2 was cut into 100mm×20mm×20mm cubes.
[0064] Self-extinguishing test: The cured polyurethane foams of Examples 1-3, Comparative Examples 1 and 2 were cut into 100mm × 20mm × 20mm cubes. Their self-extinguishing ability (how long they burned before self-extinguishing) was determined by a vertical burning test according to the following test method. The samples were held vertically on a rack with their lower ends suspended freely. Each sample was burned under the influence of a flame oriented at approximately 90° relative to the sample and towards its lower end. The self-extinguishing time (if self-extinguishing occurred) was then recorded. The performance test results of Examples 1-3 and Comparative Examples 1-2 are shown in Table 3.
[0065] Table 3 Performance test results of Examples 1-3 and Comparative Examples 1-2
[0066]
[0067] As shown in Table 3, through Examples 1-3, Comparative Example 1 and Comparative Example 2, the performance of the initiator after adding the hydroxyphosphazene derivative was significantly improved compared with that without the addition of the hydroxyphosphazene derivative.
[0068] Because hydroxyphosphazene derivatives introduce nitrogen, phosphorus, and chlorine elements during the synthesis of polyether polyols, the hydroxyl intermediates generated by hydrolysis initiate polymerization, and the flame retardant elements combine with the polyether backbone without migration issues. Furthermore, phosphorus and chlorine can synergistically retard flames, improve efficiency, and reduce combustion hazards. In addition, hexachlorocyclotriphosphazene itself contains a rigid phosphazene ring, which generates a polyhydroxy initiator after hydrolysis. The resulting polyether contains this rigid structure, which reacts with isocyanate to build a strong supporting skeleton, thereby improving the foam compression strength.
[0069] As can be seen from Examples 1-3, the foam performance in Example 2 is the best. The reason is that at this degree of substitution, 1-2 chlorine atoms are retained in the molecule, while 4-5 hydroxyl groups are generated. The hydroxyl groups act as active sites for polymerization, effectively initiating the ring-opening polymerization of propylene oxide, ensuring that flame-retardant elements (phosphorus and chlorine) are stably incorporated into the polyether backbone. During combustion, the residual chlorine atoms and phosphorus atoms form a synergistic flame-retardant effect. The phosphorus element promotes the formation of a char layer to isolate oxygen, while the chlorine atoms release free radicals to inhibit the combustion chain reaction. The combination of the two greatly improves the flame-retardant efficiency.
[0070] Comparative Example 1 shows that a low degree of substitution and insufficient hydroxyl groups result in poor polymerization activity, and the low phosphorus content makes it difficult to form an effective char layer. Example 3 shows that when the degree of substitution is close to 6, although there are sufficient hydroxyl groups, there is no chlorine element for synergy, and the flame retardancy relies solely on phosphorus, which is weaker than the phosphorus-chlorine synergistic system. Therefore, a degree of substitution of 4-5 can balance polymerization feasibility and flame retardant synergy, achieving the best flame retardant effect.
Claims
1. A method for preparing a highly flame-retardant phosphazene-based polyether polyol, characterized in that, Includes the following steps: a. In the presence of an acid-binding agent, hexachlorocyclotriphosphazene undergoes a nucleophilic substitution reaction with water to generate a phosphazene derivative containing multiple hydroxyl groups, which serves as the initiator. Specifically, hexachlorocyclotriphosphazene and solvent are added to a three-necked flask, purged with nitrogen, and stirred until clear. A mixture of deionized water and the acid-binding agent is slowly added dropwise. After the addition is complete, the temperature is raised to 60-90℃, and the reaction is maintained at this temperature for 6-12 hours. The generated salt is removed by filtration, and the solvent is removed by vacuum distillation to obtain the final product. b. Under the action of a catalyst, the phosphazene derivative initiator obtained in step a, or a mixed initiator composed of the phosphazene derivative and other small molecule polyols, is used to initiate the ring-opening polymerization of propylene oxide to obtain the highly flame-retardant phosphazene-based polyether polyol. In step a, the molar ratio of water to hexachlorocyclotriphosphazene is (3-6):1; The acid-binding agent in step a is triethylamine or anhydrous sodium carbonate; and the molar ratio of the acid-binding agent to water is (1.1-1.2):
1. Step a is carried out in an organic solvent, wherein the organic solvent is anhydrous acetonitrile or tetrahydrofuran; The ring-opening polymerization in step b includes: First polymerization stage: Polymerization is carried out by adding a portion of propylene oxide at 80-85℃ and 0.1-0.4MPa pressure; Second polymerization stage: Heat to 100-110℃ and add the remaining propylene oxide under a pressure of 0.1-0.4MPa to continue polymerization.
2. The method for preparing the highly flame-retardant phosphazene-based polyether polyol according to claim 1, characterized in that, The other small molecule polyols in step b are selected from one or more of 1,4-butanediol, ethylene glycol, diethylene glycol, glycerol, propylene glycol, diethanolamine, and hexanediol.
3. The method for preparing the highly flame-retardant phosphazene-based polyether polyol according to claim 1, characterized in that, The catalyst in step b is an alkaline catalyst, selected from one or more of triethylamine, N,N-dimethylbenzylamine, and dimethylcyclohexylamine.
4. The method for preparing the highly flame-retardant phosphazene-based polyether polyol according to claim 1, characterized in that, After the second polymerization stage is completed, a step of bubbling with nitrogen at a pressure of -0.08 MPa to -0.1 MPa is also included to remove residual small molecules.