Flame-retardant hard foam polyether polyol ester as well as preparation method and application thereof

Abstract

The invention discloses flame-retardant hard foam polyether polyol ester as well as a preparation method and application thereof. The preparation method of the polyether polyol ester comprises the following steps: taking hexachlorotripolyphosphazene and hydroxy acid as raw materials, and reacting under the action of a metal chloride catalyst to obtain an intermediate; and carrying out polymerization reaction on the intermediate serving as an initiator and oxyalkylene under the action of a polymerization catalyst to prepare the polyether polyol ester. The polyether polyol ester is prepared by taking a reactant of phosphonitrilic chloride trimer and hydroxy acid as an initiator and carrying out polymerization reaction with oxyalkylene, and the prepared foam has higher flame retardance and foam strength due to the particularity of a molecular structure.

Description

Technical Field

[0001] This invention relates to a polyether polyol ester, and more particularly to a flame-retardant rigid foam polyether polyol ester, its preparation method and application, belonging to the field of polyether polyol technology. Background Technology

[0002] Rigid polyurethane foam is widely used in insulation applications such as refrigerators, freezers, refrigerated trucks, and refrigerated containers due to its advantages including extremely low thermal conductivity, high compressive strength, and simple manufacturing process. Refrigerated trucks and containers, as crucial transport vehicles in cold chain logistics, face increasingly stringent market demands for safety, operational stability, and flame-retardant properties. This necessitates that rigid polyurethane foam not only possess excellent thermal insulation and flame-retardant properties but also provide structural strength.

[0003] Current technology makes it difficult to improve the overall performance of all these aspects simultaneously. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention first proposes a flame-retardant rigid foam polyether polyol ester and its preparation method. The polyether polyol ester is prepared by polymerization with an oxidized olefin using a reactant containing hexachlorotriphosphazene and carboxylic acid as an initiator. Due to the unique molecular structure of the foam prepared from this polyether polyol ester, a char layer is rapidly formed upon exposure to high-temperature flames, effectively blocking the transfer of high-temperature heat and improving flame retardancy. Furthermore, the conjugation effect in the nitrogen-phosphorus heterocyclic structure and the benzene ring structure in the aromatic carboxylic acid effectively enhance the foam's structural strength.

[0005] Secondly, this invention also provides the application of flame-retardant rigid foam polyether polyol ester in the preparation of rigid polyurethane foam. To achieve the above objectives, the technical solution adopted by this invention is as follows:

[0006] As a first aspect of the present invention, a method for preparing flame-retardant rigid foam polyether polyol ester is provided, comprising the following steps:

[0007] Using hexachlorotriphosphazene and hydroxy acid as raw materials, an intermediate was obtained by reaction under the action of a metal chloride catalyst;

[0008] Subsequently, using this intermediate as a starting agent, it undergoes a polymerization reaction with oxidized olefins under the action of a polymerization catalyst to obtain polyether polyol esters.

[0009] In some preferred preparation methods, the molar ratio of hexachlorotriphosphazene to hydroxy acid is 1:1-6;

[0010] Preferably, the hydroxy acid is selected from aliphatic hydroxy acids or aromatic hydroxy acids;

[0011] Preferably, the aliphatic hydroxy acid is selected from one or more of lactic acid (α-hydroxypropionic acid), glycolic acid (hydroxyacetic acid), β-hydroxybutyric acid, γ-hydroxybutyric acid, tartaric acid (dihydroxybutyric acid), and citric acid;

[0012] Preferably, the aromatic hydroxy acid is selected from one or more of p-hydroxycinnamic acid, caffeic acid, ferulic acid, sinapic acid, chlorogenic acid, salicylic acid, aristolochic acid, tyrosine, and p-hydroxybenzoic acid.

[0013] The metal chloride catalyst is selected from one or more of magnesium chloride (MgCl2), ferrous chloride (FeCl2), and nickel chloride (NiCl2), and the preferred amount is 1-3% of the mass of hexachlorotriphosphazene.

[0014] In some preferred preparation methods, the reaction temperature of the hexachlorotriphosphazene and the hydroxy acid is 105-125°C, and the reaction time is 1-3 hours.

[0015] In some preferred preparation methods, the oxidized olefin is one or more selected from ethylene oxide, propylene oxide, butane oxide, and tetrahydrofuran;

[0016] Preferably, the amount of the oxidized olefin is 2-8 times the molar amount of the hydroxy acid;

[0017] Preferably, the polymerization catalyst is an alkaline catalyst and / or a bimetallic complex catalyst, more preferably one or more of potassium hydroxide, sodium hydroxide, potassium alkoxide, sodium alkoxide, MMC, and DMC;

[0018] Preferably, the amount of the polymerization catalyst is 1-3% of the mass of the hydroxy acid.

[0019] Preferably, the polymerization reaction is divided into an esterification addition reaction stage and a vacuum curing stage. The esterification addition reaction is as follows: the intermediate of the reaction between hexachlorotriphosphazene and hydroxy acid is reacted with the polymerization catalyst in a reaction vessel completely purged with nitrogen, and the mixture is stirred and heated to 120-150°C. A portion of oxidized olefins (e.g., 5-15% of the total amount of oxidized olefins) is added and reacted for 1-4 hours. After the esterification addition reaction is completed, the temperature is raised to 180-200°C, the remaining oxidized olefins are added, and the polymerization reaction is carried out under a pressure not exceeding 0.8 MPa. Subsequently, the mixture is cured and the byproduct water and unreacted oxidized olefins are distilled off.

[0020] The above polymerization process is relatively conventional and easy to adjust for those skilled in the art, without considering the selection of the initiator. For specific details, please refer to the various solutions disclosed in the known technology. No specific restrictions are imposed here.

[0021] It is worth noting that the reaction between the hexachlorotriphosphazene and the hydroxy acid is highly complete. Based on the consideration of saving reaction steps, the unreacted raw materials can be directly fed into the polymerization reaction for the next step of the reaction without separation. The light components can be removed in one step during the vacuum polycondensation stage.

[0022] In addition, after the polymerization reaction is complete and the curing is finished, the polyether polyol ester is obtained through conventional post-processing steps such as neutralization, adsorption dehydration, and filtration. Suitable neutralizing agents include phosphoric acid, lactic acid, and acetic acid; suitable adsorbents include magnesium silicate, magnesium polysilicate, aluminum polysilicate, and diatomaceous earth; suitable filtration equipment includes, for example, a vacuum filter, preferably performed under a vacuum of -0.09 MPa for a filtration time of 1-2.5 hours. The filtrate is collected after filtration to obtain the polyether polyol ester.

[0023] As a second aspect of the present invention, a flame-retardant rigid foam polyether polyol ester prepared according to the method is also provided, preferably having a functionality of 1-6, a hydroxyl value of 140-340 mgKOH / g, and a viscosity of 2000–8000 mPa*s at 25°C.

[0024] As a third aspect of the present invention, a flame-retardant rigid polyurethane foam is also provided, which is prepared from raw materials containing the aforementioned polyether polyol ester.

[0025] A flame-retardant rigid polyurethane foam, the raw materials of which include: a polyisocyanate component and a combined polyether component;

[0026] The polyether component described herein includes A) a polyol, B) a blowing agent, and optionally C) an additive;

[0027] In some preferred embodiments of the invention, the mass ratio of the polyisocyanate component to the combined polyether component is (1-1.5):1;

[0028] Preferably, the polyisocyanate component is polymeric MDI or liquefied modified MDI, and more preferably one or more of Wanhua PM200, PM400, and PM700;

[0029] Wherein, A) the polyol includes the flame-retardant rigid foam polyether polyol ester described above; preferably, the flame-retardant rigid foam polyether polyol ester has a mass content of 5 to 45 wt% in A) the polyol.

[0030] In some preferred embodiments of the invention, A) the polyol further includes at least one of the following: a polyether polyol starting with sucrose, a polyether polyol starting with sorbitol, a polyether polyol starting with propylene glycol, and a polyester polyol starting with phthalic anhydride.

[0031] Preferably, the polyether polyol using sucrose as an initiator is a polyether polyol prepared by polymerization of propylene oxide and / or ethylene oxide with sucrose as an initiator, having a molecular weight of 400-900, a functionality of 4.5-6, and a hydroxyl value of 300-450 mgKOH / g; preferably, the mass fraction of the polyether polyol using sucrose as an initiator in polyol A) is ≤40wt% (e.g., 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, etc.), more preferably 5-40wt%;

[0032] Preferably, the polyether polyol using sorbitol as an initiator is a polyether polyol prepared by polymerization of propylene oxide and / or ethylene oxide with sorbitol as an initiator, having a molecular weight of 600-700, a functionality of 4.5-6, and a hydroxyl value of 400-500 mgKOH / g; preferably, the mass fraction of the polyether polyol using sorbitol as an initiator in polyol A) is ≤30wt% (e.g., 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, etc.), more preferably 5-30wt%;

[0033] Preferably, the polyether polyol using propylene glycol as an initiator is a polyether polyol prepared by polymerizing propylene glycol with propylene oxide and / or ethylene oxide, with a molecular weight of 400-1100, a functionality of 1.5-2, and a hydroxyl value of 100-300 mgKOH / g; preferably, the mass fraction of the polyether polyol using propylene glycol as an initiator in polyol A) is ≤30wt% (e.g., 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, etc.), preferably 5-30wt%, more preferably 5-25%.

[0034] Preferably, the polyester polyol using phthalic anhydride as an initiator has a molecular weight of 300-500, a functionality of 2, and a hydroxyl value of 220-350 mgKOH / g; the polyester polyol using phthalic anhydride as an initiator is preferably one or more of Stepan PS-3152, PS-2452, and PS-2352; preferably, the mass fraction of the polyester polyol using phthalic anhydride as an initiator in A) the polyol is ≤20wt% (e.g., 5wt%, 10wt%, 15wt%, 20wt%, etc.), more preferably 5-20wt%, and more preferably 8-20%.

[0035] Preferably, B) the amount of foaming agent is 5-15% of the mass of the combined polyether components, more preferably 8-14%;

[0036] Preferably, the amount of additive C) is 10-20% of the mass of the polyether component, more preferably 12-15%;

[0037] In some preferred embodiments of the invention, the foaming agent is one or more of cyclopentane, isopentane, and n-pentane, or a mixture of at least one of cyclopentane, isopentane, and n-pentane and water.

[0038] In some preferred embodiments of the invention, the additive is one or more of flame retardants, surfactants, and catalysts;

[0039] Preferably, the flame retardant is tri(chloroisopropyl) phosphate and / or triethyl phosphate;

[0040] Preferably, the surfactant is a siloxane, and more preferably one or more of B8546, B84813, AK88310, and AK88719;

[0041] Preferably, the catalyst is an amine and / or a metal salt and / or water, more preferably one or more of the following: dimethylaminoethyl ether, pentamethyldiethylenetriamine, N,N-dimethylcyclohexylamine, triethylenediamine, TMR-2, N,N-dimethylbenzylamine, potassium formate, potassium acetate, potassium isooctanoate, and water.

[0042] Finally, the present invention also provides a method for preparing flame-retardant rigid polyurethane foam, comprising the following steps:

[0043] (1) Mix the polyol, foaming agent and optional additives evenly to obtain the combined polyether component;

[0044] (2) Mix the polyether component and the polyisocyanate component, foam, and mold.

[0045] In some preferred embodiments, the foaming temperature for mixing the polyether component and the polyisocyanate component is 15-25°C.

[0046] The beneficial effects of this invention are as follows:

[0047] The polyurethane rigid foam provided by this invention exhibits stable gel time and core density, with a smooth and controllable foaming process, demonstrating excellent industrial applicability. The cyclic structure of hexachlorotriphosphazene (HCCP) contains alternating phosphorus and nitrogen atoms. The intermediates generated after its reaction with carboxylic acid retain the phosphazene skeleton. Therefore, during foam combustion, phosphorus decomposes at high temperatures to generate PO· free radicals, which capture H· and HO· free radicals from the combustion chain reaction, interrupting the combustion reaction. Nitrogen decomposes to produce non-combustible gases such as NH3 and N2, diluting the oxygen concentration. Simultaneously, the phosphazene structure promotes carbonization, forming a dense char layer that isolates heat and oxygen. The HCCP-derived initiator, acting as the rigid core of the polyether chain, possesses a cyclic phosphazene skeleton with high thermal stability (decomposition temperature > 250℃), delaying material thermal degradation and enhancing structural stability. The covalent connection between the polyether chain and the phosphazene core further prevents molecular chain slippage, enhancing the integrity of the char layer. The intermediates generated by the reaction of HCCP with carboxylic acids contain multiple active sites (such as hydroxyl groups), which can be used as multifunctional initiators to initiate the polymerization of oxidized olefins and form star-shaped or hyperbranched polyether structures. This highly cross-linked network can uniformly disperse stress, reduce the risk of local breakage, and further enhance the rigidity of the molecular chain.

[0048] The flexibility of the polyether chains and the rigidity of the phosphazene core form a "flexible-rigid" structure: the flexible chain segments absorb impact energy, while the rigid core prevents crack propagation, achieving a balance between strength and toughness. Simultaneously, the phosphazene structure preferentially carbonizes during combustion, while the decomposition gases from the polyether chains assist in expanding the char layer, forming a multi-level flame-retardant barrier; ensuring that the foam has a high flame-retardant effect while its strength is greatly improved.

[0049] More importantly, while maintaining a low thermal conductivity and a high oxygen index, the polyurethane foam of this invention still has improved compressive strength and flexural strength. Therefore, the foam has the advantages of fine pores, high strength and good flame retardancy, and can be widely used in the field of insulation material preparation, such as insulation layers for refrigerated containers and refrigerated trucks. Detailed Implementation

[0050] The present invention will be further illustrated below with specific embodiments. These embodiments are merely illustrative and do not limit the scope of the invention.

[0051] Unless otherwise specified, the raw material information in the following embodiments is derived from commercially available finished products. Among them:

[0052] Polyether polyol A1: Hexachlorotriphosphazene was added dropwise to glycolic acid under the catalysis of ferrous chloride, with a molar ratio of hexachlorotriphosphazene to glycolic acid of 1:3. The amount of ferrous chloride was 1% of the mass of hexachlorotriphosphazene. The reaction was carried out at 110°C for 2 hours to obtain an intermediate. The intermediate and potassium hydroxide were mixed in a reactor, with the amount of potassium hydroxide being 1% of the mass of glycolic acid. The mixture was purged with nitrogen and evacuated. The mixture was then stirred and heated to 140°C. A portion of propylene oxide (10% of the total mass of propylene oxide) was then added, with the total molar amount of propylene oxide being twice the molar amount of glycolic acid. The mixture was allowed to mature for 2 hours. After maturation, the remaining propylene oxide was added and the temperature was raised to 180°C. The pressure was maintained at 0.8 MPa, and the polymerization reaction was carried out for 2 hours. The mixture was then allowed to mature under vacuum to remove light component impurities. After aging, phosphoric acid was added for neutralization, followed by the addition of magnesium silicate for adsorption and dehydration. After stirring and filtration, polyether polyol A1 was obtained; functionality 3, hydroxyl value 235 mg KOH / g, viscosity 4200 mPa*s (25℃).

[0053] Polyether polyol A2: Hexachlorotriphosphazene and p-hydroxybenzoic acid were added dropwise at a molar ratio of 1:1 under the action of magnesium chloride catalyst (hexachlorotriphosphazene was added dropwise to p-hydroxybenzoic acid). The reaction was carried out at 120°C for 2 hours to obtain an intermediate, wherein the amount of magnesium chloride was 1.5% of the mass of hexachlorotriphosphazene. The intermediate and DMC were mixed in a reactor, wherein the amount of DMC was 2% of the mass of p-hydroxybenzoic acid. The reactor was purged with nitrogen and evacuated, then stirred and heated to 130°C. Subsequently, a portion of propylene oxide (accounting for 10% of the total mass of propylene oxide) was added, and the total molar amount of propylene oxide was 5 times the molar amount of p-hydroxybenzoic acid. The mixture was aged for 2 hours. After aging was completed, the remaining propylene oxide was added and the temperature was raised to 180°C. The pressure was maintained at 0.8 MPa, and the polymerization reaction was carried out for 2 hours. The mixture was then aged under vacuum to remove light component impurities. After aging, phosphoric acid was added for neutralization, followed by the addition of magnesium silicate for adsorption and dehydration. After stirring and filtration, polyether polyol A2 was obtained; functionality 1, hydroxyl value 140 mg KOH / g, viscosity at 25℃ 2200 mPa*s.

[0054] Polyether polyol A3: Hexachlorotriphosphazene and lactic acid were added dropwise at a molar ratio of 1:6 under the action of magnesium chloride catalyst (hexachlorotriphosphazene was added dropwise to the lactic acid) and reacted at 125°C for 2 hours to obtain an intermediate; the amount of magnesium chloride was 2% of the mass of hexachlorotriphosphazene. The intermediate and sodium hydroxide were mixed in a reactor, the amount of sodium hydroxide being 3% of the mass of lactic acid. The reactor was purged with nitrogen and evacuated, then stirred and heated to 150°C. Subsequently, a portion of propylene oxide (10% of the total mass of propylene oxide) was added, the total molar amount of propylene oxide being 3 times the molar amount of lactic acid, and the mixture was aged for 2 hours. After aging was completed, the remaining propylene oxide was added and the temperature was raised to 200°C. The pressure was maintained at 0.8 MPa, and the polymerization reaction was carried out for 2 hours. Then, the mixture was evacuated and aged to remove light component impurities. After aging, phosphoric acid was added for neutralization, followed by the addition of magnesium silicate for adsorption and dehydration. After stirring and filtration, polyether polyol A3 was obtained; functionality 6, hydroxyl value 337 mg KOH / g, viscosity at 25℃ 6600 mPa*s.

[0055] Polyether polyol B1: R2839, with sucrose as the initiator, hydroxyl value 380mgKOH / g, functionality 5.5, viscosity 11000mpa*s, Wanhua Chemical (Yantai) Rongwei;

[0056] Polyether polyol B2: R4110, with sucrose as the initiator, hydroxyl value 440mgKOH / g, functionality 4.5, viscosity 3000mpa*s, Wanhua Chemical (Yantai) Rongwei;

[0057] Polyether polyol C1: R2380, with sorbitol as the initiator, hydroxyl value 480mgKOH / g, functionality 5.4, viscosity 25000mpa*s, Wanhua Chemical (Yantai) Rongwei;

[0058] Polyether polyol C2: R6245, with sorbitol as the initiator, hydroxyl value 450mgKOH / g, functionality 5.4, viscosity 23000mpa*s, Wanhua Chemical (Yantai) Rongwei;

[0059] Polyether polyol D1: A210, with propylene glycol as the initiator, hydroxyl value 110mgKOH / g, functionality 2, viscosity 250mpa*s, Wanhua Chemical (Yantai) Rongwei;

[0060] Polyether polyol D2: C2004, with propylene glycol as the initiator, hydroxyl value 280mgKOH / g, functionality 2, viscosity 80mpa*s, Wanhua Chemical (Yantai) Rongwei;

[0061] Polyester polyol E1: PS-2352, with phthalic anhydride as the initiator, functionality 2, hydroxyl value 235mgKOH / g, viscosity 3500mp*s, Stephan;

[0062] Polyester polyol E2: PS-3152, with phthalic anhydride as the initiator, functionality 2, hydroxyl value 315mgKOH / g, viscosity 4200mp*s, Stephan;

[0063] TCPP flame retardant: Yake Technology;

[0064] B8545 silicone oil: Evonik Specialty Chemicals (Shanghai) Co., Ltd.;

[0065] Composite catalyst A: a mixture of pentamethyldiethylenetriamine, dimethylcyclohexylamine, and TMR-2 in a mass ratio of 1:5:1, Evonik Specialty Chemicals (Shanghai) Co., Ltd.

[0066] Composite catalyst B: a mixture of dimethylaminoethyl ether, dimethylcyclohexylamine, and potassium acetate in a mass ratio of 1:10:2, Evonik Specialty Chemicals (Shanghai) Co., Ltd.

[0067] Cyclopentane: Meilong Chemical;

[0068] n-Pentane: Meilong Chemical;

[0069] PM200: Wanhua Chemical.

[0070]

Examples S1-S6

[0071] Prepare the raw materials according to the formula in Table 1, and mix them thoroughly after heating each material to 21℃. Pour the mixture into a 35cm*35cm*10cm foaming mold for foaming at 38℃ and a material density of 48kg / m³. 3 To prepare rigid polyurethane foam.

[0072] Table 1. Raw material formulations (g) in Examples S1-S6

[0073]

[0074] Comparative Example D1

[0075] Polyurethane rigid foam was prepared by foaming according to the same formulation and method as in Example S1, except that polyether polyol A1 was not added and the amount of polyether polyol D1 was increased accordingly to ensure that the total mass of the combined polyether components remained unchanged.

[0076] Comparative Example D2

[0077] Polyurethane rigid foam was prepared by foaming according to a formula and method that is basically the same as that in Example S1, except that the polyether polyol A1 was replaced with the same mass of flame retardant polyol FR212 (Wanhua Chemical (Yantai) Rongwei Polyurethane Co., Ltd.).

[0078] The performance tests shown in Table 2 were performed on the polyurethane rigid foams prepared in Examples S1-S6 and Comparative Examples D1-D2. The test results are as follows. The relevant test methods mainly include:

[0079] (1) Gel time: Wanhua Chemical (Yantai) Rongwei Polyurethane Co., Ltd. Enterprise Standard Q / 0600YPU 026-2022

[0080] (2) Foam core density: Wanhua Chemical (Yantai) Rongwei Polyurethane Co., Ltd. Enterprise Standard Q / 0600YPU 026-2022

[0081] (3) Thermal conductivity: ASTM C518

[0082] (4) Oxygen index: GB / T 2406-009

[0083] (5) Compressive strength: GB / T 8813-2008

[0084] (6) Bending strength: GB / T 8812-2008

[0085] Table 2. Performance Test Results

[0086]

[0087] As can be seen from the performance test results of D2 and D1 in Table 2, the introduction of conventional flame-retardant polyether improves the oxygen index to a certain extent, but it will cause some damage to the foam strength. It is difficult to improve both at the same time, which cannot fully meet the requirements of refrigerated trucks, refrigerated containers and other transport carriers for high-strength support materials.

[0088] The test results of S1-S6 show that the oxygen index of the polyurethane rigid foam obtained by the present invention is not only significantly improved by more than two percentage points compared with D1, which significantly improves the flame retardancy of the foam, but also improves the compressive strength and flexural strength at the same time, solving the pain points of the industry. The obtained polyurethane rigid foam is particularly suitable for applications such as refrigerated trucks and refrigerated containers that have high requirements for both flame retardancy and foam strength.

[0089] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a polyether polyol ester, characterized in that, Includes the following processes: Hexachlorotriphosphazene and hydroxy acids were reacted under the action of metal chlorides to obtain an intermediate; then, the intermediate was used as an initiator to undergo a polymerization reaction with oxidized olefins under the action of a polymerization catalyst to obtain polyether polyol esters.

2. The preparation method according to claim 1, characterized in that, The molar ratio of hexachlorotriphosphazene and hydroxy acid is 1:1-6; Preferably, the carboxyl acid is selected from at least one of aliphatic hydroxy acids or aromatic hydroxy acids; Preferably, the aliphatic hydroxy acid is selected from one or more of lactic acid, glycolic acid, β-hydroxybutyric acid, γ-hydroxybutyric acid, tartaric acid, and citric acid; Preferably, the aromatic hydroxy acid is selected from one or more of p-hydroxycinnamic acid, caffeic acid, ferulic acid, sinapic acid, chlorogenic acid, salicylic acid, aristolochic acid, tyrosine, and p-hydroxybenzoic acid.

3. The preparation method according to claim 1 or 2, characterized in that, The metal chloride is selected from one or more of ferrous chloride, magnesium chloride, and nickel chloride, and the amount used is 1-3% of the weight of hexachlorotriphosphazene. Preferably, the reaction temperature of hexachlorotriphosphazene and hydroxy acid is 105-125℃, and the reaction time is 1-3 hours.

4. The preparation method according to claim 1 or 2, characterized in that, The oxidized olefin is one or more selected from ethylene oxide, propylene oxide, butane oxide, and tetrahydrofuran; Preferably, the amount of the oxidized olefin is 2-8 times the molar amount of the hydroxy acid; Preferably, the polymerization catalyst is an alkaline catalyst and / or a bimetallic complex catalyst, more preferably one or more of potassium hydroxide, sodium hydroxide, potassium alkoxide, sodium alkoxide, MMC, and DMC; Preferably, the amount of the polymerization catalyst is 1-3% of the mass of the hydroxy acid.

5. The preparation method according to any one of claims 1-4, characterized in that, The polymerization reaction first involves stirring and heating the intermediate and polymerization catalyst in a reactor to 120-150°C, adding a portion of the oxidized olefins (e.g., 5-15% of the total oxidized olefins) and reacting for 1-4 hours; then heating to 180-200°C, adding the remaining oxidized olefins, and carrying out the polymerization reaction while maintaining a pressure not exceeding 0.8 MPa, followed by ripening and distilling off the byproducts water and unreacted oxidized olefins.

6. A polyether polyol ester prepared by the method according to any one of claims 1-5, characterized in that, Functionality is 1-6, hydroxyl value is 140-340 mgKOH / g, and viscosity at 25℃ is 2000-8000 mPa*s.

7. A flame-retardant rigid polyurethane foam, characterized in that, Its raw materials include a polyisocyanate component and a combined polyether component, wherein the combined polyether component includes A) a polyol, B) a foaming agent and optionally C) an additive; wherein A) the polyol includes a polyether polyol ester prepared by the preparation method according to any one of claims 1-5; preferably, the polyether polyol ester has a mass content of 5-45 wt% in A) the polyol; Preferably, B) the amount of foaming agent used is 5-15% of the mass of the combined polyether components; Preferably, the amount of additive C) is 10-20% of the mass of the polyether component.

8. The flame-retardant rigid polyurethane foam according to claim 7, characterized in that, A) Polypolyols also include at least one of the following: polyether polyols starting with sucrose, polyether polyols starting with sorbitol, polyether polyols starting with propylene glycol, and polyester polyols starting with phthalic anhydride. Preferably, the polyether polyol using sucrose as an initiator is a polyether polyol prepared by polymerization of propylene oxide and / or ethylene oxide with sucrose as an initiator, having a molecular weight of 400-900, a functionality of 4.5-6, and a hydroxyl value of 300-450 mgKOH / g; preferably, the mass fraction of the polyether polyol using sucrose as an initiator in polyol A) is ≤40wt%, preferably 5-40wt%; Preferably, the polyether polyol with sorbitol as the initiator is a polyether polyol prepared by polymerization of propylene oxide and / or ethylene oxide with sorbitol as the initiator, having a molecular weight of 600-700, a functionality of 4.5-6, and a hydroxyl value of 400-500 mgKOH / g; preferably, the mass fraction of the polyether polyol with sorbitol as the initiator in polyol A) is ≤30wt%, preferably 5-30wt%; Preferably, the polyether polyol using propylene glycol as an initiator is a polyether polyol prepared by polymerizing propylene glycol with propylene oxide and / or ethylene oxide, with a molecular weight of 400-1100, a functionality of 1.5-2, and a hydroxyl value of 100-300 mgKOH / g; preferably, the mass fraction of the polyether polyol using propylene glycol as an initiator in polyol A) is ≤30wt%, preferably 5-30wt%. Preferably, the polyester polyol using phthalic anhydride as an initiator has a molecular weight of 300-500, a functionality of 2, and a hydroxyl value of 220-350 mgKOH / g; more preferably, the mass fraction of the polyester polyol using phthalic anhydride as an initiator in polyol A) is ≤20wt%, preferably 5-20wt%.

9. The flame-retardant rigid polyurethane foam according to any one of claims 7-8, characterized in that, The foaming agent is one or more of cyclopentane, isopentane, and n-pentane, or a mixture of at least one of cyclopentane, isopentane, and n-pentane and water; and / or The additive is one or more of flame retardants, surfactants, and catalysts; Preferably, the flame retardant is tri(chloroisopropyl) phosphate and / or triethyl phosphate; Preferably, the surfactant is a siloxane, and more preferably at least one of B8546, B84813, AK88310, and AK88719; Preferably, the catalyst is an amine and / or a metal salt and / or water, more preferably one or more of the following: dimethylaminoethyl ether, pentamethyldiethylenetriamine, N,N-dimethylcyclohexylamine, triethylenediamine, TMR-2, N,N-dimethylbenzylamine, potassium formate, potassium acetate, potassium isooctanoate, and water.

10. The flame-retardant rigid polyurethane foam according to any one of claims 7-9, characterized in that, The mass ratio of the polyisocyanate component to the combined polyether component is (1-1.5):1; Preferably, the polyisocyanate component is polymeric MDI or liquefied modified MDI, and more preferably at least one of Wanhua PM200, PM400 and PM700.

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