Reclaimed polyols, combined polyethers, polyurethane compositions, polyurethane foams, and methods of making the same

Abstract

The application provides a regenerated polyol, a combined polyether, a polyurethane composition, a polyurethane foam and a preparation method thereof. The regenerated polyol is prepared by the following method: waste PET raw materials, alcoholysis agent and alcoholysis catalyst are mixed and subjected to alcoholysis reaction to obtain PET alcoholysis product; the PET alcoholysis product is subjected to esterification reaction with organic acid anhydride at a mass ratio of 1:(0.08-0.12) to obtain regenerated polyol with a hydroxyl value of 300 mgKOH / g-350 mgKOH / g. The application realizes accurate control of the hydroxyl value of the regenerated polyol, which is similar to the hydroxyl value of the traditional petroleum-based polyether polyol, and the reaction activity of the regenerated polyol and isocyanate is highly matched, so that the substitution rate of the regenerated polyol to the traditional petroleum-based polyether polyol can be improved, the raw material cost is significantly reduced, efficient recycling of waste PET is realized, and economic and environmental values are combined.

Description

Technical Field

[0001] This application belongs to the field of polyurethane technology, and particularly relates to a recycled polyol, a combined polyether, a polyurethane composition, a polyurethane foam, and a method for preparing the same. Background Technology

[0002] Polyurethane foam, due to its excellent properties such as lightweight, thermal insulation, and cushioning, is widely used in building insulation, automotive interiors, and packaging materials. Traditional polyurethane foam primarily uses petroleum-based polyether polyols as raw materials; however, petroleum resources are non-renewable, and with the escalating global energy crisis, raw material costs continue to rise. Simultaneously, plastic waste pollution is becoming increasingly serious, with polyethylene terephthalate (PET) bottles being produced in enormous quantities, and the low recycling rate of waste PET bottles causing a severe environmental burden.

[0003] Currently, some technologies have been developed to prepare recycled polyols from recycled PET and apply them to polyurethane foam systems to replace some of the petroleum-based polyether polyols in traditional polyether blends. However, existing technologies still have the following drawbacks: recycled polyols prepared from recycled PET have a low substitution rate in polyether blends due to poor structural regularity and difficulty in controlling hydroxyl value, and cannot fully leverage the cost advantages of recycling waste materials. Summary of the Invention

[0004] This application provides a recycled polyol, a combined polyether, a polyurethane composition, a polyurethane foam, and a method for preparing the same, to address the problem of low substitution rates of existing recycled polyols based on recycled PET.

[0005] In a first aspect, embodiments of this application provide a recycled polyol, which is prepared by the following method: waste PET raw materials, alcoholysis agent and alcoholysis catalyst are mixed and then subjected to alcoholysis reaction to obtain PET alcoholysis product; the PET alcoholysis product is subjected to esterification reaction with organic acid anhydride at a mass ratio of 1:(0.08~0.12) to obtain a recycled polyol with a hydroxyl value of 300mgKOH / g~350mgKOH / g.

[0006] Optionally, the mass ratio of the waste PET raw material, the alcoholysis agent, and the alcoholysis catalyst is 1:(1.2~1.5):(0.005~0.01); and / or, the alcoholysis reaction temperature is 160℃~180℃, and the reaction time is 2h~3h; and / or, the alcoholysis agent includes a diol, which is selected from one or more of ethylene glycol, propylene glycol, 1,4-butanediol, diethylene glycol, 1,3-propanediol, and neopentyl glycol; and / or, the alcoholysis catalyst is selected from one or more of zinc oxide, zinc acetate, magnesium oxide, calcium oxide, lead acetate, and tetrabutyl titanate; and / or, the waste PET raw material is obtained from waste PET bottles after washing, crushing, and drying.

[0007] Optionally, the esterification reaction temperature is 120℃~140℃, and the reaction time is 1.5h~2.5h; and / or, the organic acid anhydride is selected from one or more of phthalic anhydride, succinic anhydride, maleic anhydride, fumaric anhydride, adipic anhydride, and trimellitic anhydride; and / or, after the esterification reaction is completed, impurities are removed by vacuum distillation to obtain the regenerated polyol, wherein the vacuum distillation pressure is -0.08MPa~-0.1MPa, and the distillation temperature is 150℃~170℃.

[0008] Secondly, embodiments of this application also provide a combined polyether, the combined polyether comprising a polyol composition, the polyol composition comprising the above-mentioned recycled polyol.

[0009] Optionally, the combined polyether further includes a titanate coupling agent.

[0010] Optionally, the mass ratio of the titanate coupling agent to the polyol composition is (0.3~0.5):100; and / or, the titanate coupling agent is selected from one or more of isopropyl tristearoyl titanate, isopropyl tris(dioctyl pyrophosphoyloxy) titanate, tetraisopropyl di(dioctyl phosphite) titanate, di(dioctyl pyrophosphoyloxy) ethylene titanate, isopropyl tris(stearoyloxy) titanate, and octylphosphonate monoalkoxy titanate.

[0011] Optionally, the polyol composition further includes bio-based polyether polyol and petroleum-based polyether polyol, wherein the mass ratio of the recycled polyol, the bio-based polyether polyol and the petroleum-based polyether polyol is (40~50):(20~30):(20~40).

[0012] Optionally, the sum of the masses of the recycled polyol and the bio-based polyether polyol accounts for more than 70% of the total mass of the polyol composition; and / or, the hydroxyl value of the bio-based polyether polyol is 280 mg KOH / g to 320 mg KOH / g, and the hydroxyl value of the petroleum-based polyether polyol is 310 mg KOH / g to 350 mg KOH / g; and / or, the bio-based polyether polyol is selected from one or more of castor oil-based polyether polyol, soybean oil-based polyether polyol, palm oil-based polyether polyol, rapeseed oil-based polyether polyol, linseed oil-based polyether polyol, and rosin-based polyether polyol; and / or, the petroleum-based polyether polyol is selected from one or more of polyether polyol 4110, polyether polyol 330N, polyether polyol 3050, polyether polyol 210, polyether polyol 403, and polyether polyol 630.

[0013] Optionally, the polyether composition further includes at least one of a catalyst, a blowing agent, and a foam stabilizer, wherein the mass ratio of the catalyst to the polyol composition is (0.5~1):100, the mass ratio of the blowing agent to the polyol composition is (3~5):100, and the mass ratio of the foam stabilizer to the polyol composition is (1~2):100.

[0014] Optionally, the catalyst comprises an organic amine catalyst selected from one or more of dimethylcyclohexylamine, triethylenediamine, N-methylmorpholine, bis(dimethylaminoethyl) ether, triethanolamine, N-ethylmorpholine, and diethanolamine; and / or, the blowing agent is selected from one or more of organic and inorganic blowing agents, the organic blowing agent comprising one or more of 1,1,1,3,3-pentafluoropropane, cyclopentane, isopentane, n-pentane, and 1,3,3,3-tetrafluoropropene, and the inorganic blowing agent comprising water; and / or, the foam stabilizer is selected from one or more of silicone surfactants L-580, L-6880, L-6900, L-6988, DC-193, B-8404, and B-8462.

[0015] Thirdly, embodiments of this application also provide a polyurethane composition comprising isocyanate and the above-described combined polyether.

[0016] Optionally, the mass ratio of the polyether to the isocyanate is 1:(1~1.2); and / or, the NCO content of the isocyanate is 28wt%~32wt%.

[0017] Fourthly, embodiments of this application also provide a polyurethane foam, which is obtained by foaming the above-mentioned polyurethane composition.

[0018] Fifthly, embodiments of this application also provide a method for preparing polyurethane foam, the method comprising the following steps:

[0019] S100. Waste PET raw materials, alcoholysis agent and alcoholysis catalyst are mixed and then subjected to alcoholysis reaction to obtain PET alcoholysis product; S200. The PET alcoholysis product is esterified with an organic acid anhydride at a mass ratio of 1:(0.08~0.12) to obtain a recycled polyol with a hydroxyl value of 300mgKOH / g~350mgKOH / g. S300. The recycled polyol is mixed with a foaming agent to obtain a combined polyether; S400. The combined polyether is mixed with isocyanate and foamed to obtain polyurethane foam.

[0020] Optionally, step S100 includes: mixing waste PET raw materials, alcoholysis agent and alcoholysis catalyst at a mass ratio of 1:(1.2~1.5):(0.005~0.01), and carrying out alcoholysis reaction at 160℃~180℃ and 0.1MPa~0.3MPa for 2h~3h to obtain PET alcoholysis product; and / or, in step S100, the waste PET raw materials are obtained from waste PET bottles after washing, crushing and drying.

[0021] Optionally, step S200 includes: mixing the PET alcoholysis product with an organic acid anhydride at a mass ratio of 1:(0.08~0.12), and carrying out an esterification reaction at 120℃~140℃ for 1.5h~2.5h to obtain the regenerated polyol; and / or, in step S200, after the esterification reaction is completed, impurities are removed by vacuum distillation to obtain the regenerated polyol, wherein the pressure of vacuum distillation is -0.08MPa~-0.1MPa, and the distillation temperature is 150℃~170℃.

[0022] Optionally, step S300 includes: mixing the recycled polyol, bio-based polyether polyol, and petroleum-based polyether polyol to obtain a polyol composition; mixing the polyol composition with a titanate coupling agent, stirring and reacting at 80°C to 100°C for 0.5h to 0.8h, then adding a catalyst, a foaming agent, and a foam stabilizer, continuing to stir for 0.5h to 0.8h, and cooling to 23°C to 27°C to obtain a combined polyether; and / or, step S400 includes: mixing the combined polyether with isocyanate at a mass ratio of 1:(1 to 1.2), stirring at 25°C to 35°C for 5s to 10s, and then foaming and curing at 23°C to 27°C for 12h to 24h to obtain polyurethane foam.

[0023] The recycled polyols, combined polyethers, polyurethane compositions, polyurethane foams, and their preparation methods provided in this application are obtained by alcoholystolysis of waste PET raw materials followed by esterification. The hydroxyl value of the recycled polyols is precisely controlled to be 300 mg KOH / g to 350 mg KOH / g. This hydroxyl value range is similar to that of traditional petroleum-based polyether polyols and has a high reactivity with isocyanates. This can improve the substitution rate of recycled polyols for traditional petroleum-based polyether polyols, significantly reduce raw material costs, and achieve efficient recycling of waste PET, thus possessing both economic and environmental value. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of this application. Those skilled in the art can obtain other drawings based on these drawings without creative effort. In the following description, the same reference numerals denote the same parts.

[0025] Figure 1 This is a flowchart illustrating the preparation method of polyurethane foam provided in an embodiment of this application. Detailed Implementation

[0026] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0027] In the description of this application, unless otherwise stated, directional terms such as "upper" and "lower" specifically refer to the drawing directions in the accompanying drawings. Additionally, in the description of this application, the term "comprising" means "including but not limited to". The term "exemplary" is used to mean "serving as an example, illustration, or description," and any embodiment described as "exemplary" is not necessarily to be construed as being more preferred or advantageous than other embodiments. The term "and / or" includes any and all combinations of one or more of the associated listed items. The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features; thus, features defined with "first" or "second" may explicitly or implicitly include one or more of the stated features.

[0028] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, which applies regardless of the range.

[0029] When using existing technologies to prepare recycled polyols from recycled PET, the hydroxyl value of the prepared recycled polyols is usually 250mgKOH / g~280mgKOH / g, which cannot be precisely controlled to be close to the hydroxyl value of traditional petroleum-based polyether polyols (310mgKOH / g~350mgKOH / g). This results in a low substitution rate of recycled polyols for traditional petroleum-based polyether polyols (≤25%).

[0030] This application provides a recycled polyol based on recycled PET. The recycled polyol is prepared by the following method: waste PET raw material, alcoholysis agent and alcoholysis catalyst are mixed and then subjected to alcoholysis reaction to obtain PET alcoholysis product; the PET alcoholysis product is subjected to esterification reaction with organic acid anhydride at a mass ratio of 1:(0.08~0.12) to obtain a recycled polyol with a hydroxyl value of 300mgKOH / g~350mgKOH / g.

[0031] The recycled polyol provided in this application is prepared by sequentially performing alcoholysis and esterification reactions on waste PET raw materials (i.e., alcoholysis followed by esterification modification of waste PET raw materials). The hydroxyl value of the recycled polyol is precisely controlled to be 300mgKOH / g~350mgKOH / g. This hydroxyl value range is similar to that of traditional petroleum-based polyether polyols (310mgKOH / g~350mgKOH / g) and highly matched with the reactivity of isocyanates. This can improve the substitution rate of recycled polyols for traditional petroleum-based polyether polyols, significantly reduce raw material costs, and achieve efficient recycling of waste PET, thus possessing both economic and environmental value.

[0032] For example, the mass ratio of the PET alcoholysis product to the organic acid anhydride can be 1:0.08, 1:0.09, 1:0.10, 1:0.11, 1:0.12, or any two of the aforementioned ratios; the hydroxyl value of the recycled polyol can be 300 mg KOH / g, 310 mg KOH / g, 320 mg KOH / g, 330 mg KOH / g, 340 mg KOH / g, 350 mg KOH / g, or any two of the aforementioned ratios.

[0033] Optionally, the waste PET raw material can be obtained by washing, crushing, and drying waste PET bottles. For example, the waste PET raw material can be waste PET bottle fragments (particle size of 2mm~5mm).

[0034] In some embodiments of this application, the mass ratio of the waste PET raw material, the alcoholysis agent, and the alcoholysis catalyst is 1:(1.2~1.5):(0.005~0.01). This setting facilitates the thorough and effective alcoholysis of the waste PET raw material, thereby improving the recovery rate of the waste PET raw material. Exemplarily, the mass ratio of the waste PET raw material, the alcoholysis agent, and the alcoholysis catalyst can be 1:1.2:0.005, 1:1.2:0.0075, 1:1.2:0.01, 1:1.35:0.005, 1:1.35:0.0075, 1:1.35:0.01, 1:1.5:0.005, 1:1.5:0.0075, 1:1.5:0.01, or any range between the aforementioned two ratios.

[0035] Optionally, the alcoholysis reaction is carried out at a temperature of 160℃~180℃, a pressure of 0.1MPa~0.3MPa, and a reaction time of 2h~3h. By setting the temperature and time of the alcoholysis reaction within the above range, this application facilitates the full progress of the alcoholysis reaction and improves the recovery rate of waste PET raw materials.

[0036] For example, the temperature of the alcoholysis reaction can be 160℃, 162℃, 165℃, 168℃, 170℃, 172℃, 175℃, 178℃, 180℃ or any range between two of the aforementioned values; the pressure can be 0.1MPa, 0.15MPa, 0.2MPa, 0.25MPa, 0.3MPa or any range between two of the aforementioned values; and the time of the alcoholysis reaction can be 2h, 2.1h, 2.2h, 2.3h, 2.4h, 2.5h, 2.6h, 2.7h, 2.8h, 2.9h, 3h or any range between two of the aforementioned values.

[0037] Optionally, the alcoholysis agent comprises a diol, which may be selected from one or more of ethylene glycol, propylene glycol, 1,4-butanediol, diethylene glycol (i.e., diethylene glycol monohydrate), 1,3-propanediol, and neopentyl glycol. When the alcoholysis agent is a mixture of two substances selected from ethylene glycol, propylene glycol, 1,4-butanediol, diethylene glycol (i.e., diethylene glycol monohydrate), 1,3-propanediol, and neopentyl glycol, the mass ratio of the two substances is 1:(0.5~1), for example, it can be 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, or any range between the aforementioned two ratios.

[0038] Optionally, the alcoholysis catalyst may be selected from one or more of zinc oxide, zinc acetate, magnesium oxide, calcium oxide, lead acetate, and tetrabutyl titanate. When the alcoholysis catalyst is composed of two of these substances, the mass ratio of the two substances may be 1:(0.8~1.2), for example, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, or any range between the aforementioned two ratios.

[0039] In some embodiments of this application, the esterification reaction temperature is 120℃~140℃, and the reaction time is 1.5h~2.5h. By setting the temperature and time of the esterification reaction within the above range, this application facilitates the full conduct of the esterification reaction, thereby precisely controlling the hydroxyl value of the regenerated polyol to be 300mgKOH / g~350mgKOH / g.

[0040] For example, the temperature of the esterification reaction can be 120°C, 122°C, 125°C, 128°C, 130°C, 132°C, 135°C, 138°C, 140°C, or any range between two of the aforementioned values, and the time of the esterification reaction can be 1.5h, 1.6h, 1.7h, 1.8h, 1.9h, 2h, 2.1h, 2.2h, 2.3h, 2.4h, 2.5h, or any range between two of the aforementioned values.

[0041] Optionally, the organic anhydride is selected from one or more of phthalic anhydride, succinic anhydride (i.e., succinic anhydride), maleic anhydride, fumaric anhydride, adipic anhydride, and trimellitic anhydride.

[0042] Optionally, after the esterification reaction is completed, impurities are removed by vacuum distillation to obtain the regenerated polyol. The pressure of the vacuum distillation is -0.08 MPa to -0.1 MPa, and the distillation temperature is 150°C to 170°C. This application improves the purity of the obtained regenerated polyol by removing impurities through vacuum distillation after the esterification reaction, thus obtaining a regenerated polyol with higher purity. For example, the pressure of the vacuum distillation can be -0.08 MPa, -0.085 MPa, -0.09 MPa, -0.095 MPa, -0.1 MPa, or any range between two of the aforementioned values, and the distillation temperature can be 150°C, 152°C, 155°C, 158°C, 160°C, 162°C, 165°C, 168°C, 170°C, or any range between two of the aforementioned values.

[0043] This application also provides a composite polyether comprising a polyol composition, wherein the polyol composition comprises the aforementioned recycled polyol. Since this composite polyether employs all the technical solutions of the above embodiments, it possesses at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated upon here.

[0044] In some embodiments of this application, the combined polyether further includes a titanate coupling agent. Existing recycled polyols based on recycled PET have poor compatibility with isocyanates, especially after increasing the substitution rate, which easily leads to uneven reaction during foaming. This results in defects in the polyurethane foam such as surface bubbles, large and uneven cell size, and a significant decrease in mechanical properties, limiting its application in high-requirement fields. This application addresses this by including a titanate coupling agent in the combined polyether. The titanate coupling agent molecule contains alkoxy and isocyanate groups. The alkoxy group can combine with the hydroxyl group of the recycled polyol, and the isocyanate group can react with the isocyanate, forming a bridging effect. This significantly improves the compatibility between the recycled polyol and isocyanate, enhances the uniformity of the foaming reaction, improves the cell uniformity of the polyurethane foam, and ensures the stability of the mechanical properties of the polyurethane foam.

[0045] Understandably, this application employs a two-step modification process involving alcoholysis and esterification of waste PET raw materials to precisely control the hydroxyl value of the recycled polyol to 300 mg KOH / g~350 mg KOH / g. Simultaneously, the addition of a titanate coupling agent significantly improves the compatibility between the recycled polyol and isocyanate, enabling the replacement rate of the recycled polyol with traditional petroleum-based polyether polyols to reach 40%~50%. This not only breaks through the existing technology's replacement rate limitations but also solves the problem of decreased polyurethane foam performance under high replacement rates.

[0046] Optionally, the mass ratio of the titanate coupling agent to the polyol composition is (0.3~0.5):100. Exemplarily, the mass ratio of the titanate coupling agent to the polyol composition can be 0.3:100, 0.35:100, 0.4:100, 0.45:100, 0.5:100, or any range between the aforementioned two ratios.

[0047] Optionally, the titanate coupling agent is selected from one or more of isopropyl tristearoyl titanate, isopropyl tris(dioctyl pyrophosphoyloxy) titanate, tetraisopropyl di(dioctyl phosphite) titanate, di(dioctyl pyrophosphoyloxy) ethylene titanate, isopropyl tris(stearoyloxy) titanate, and octylphosphonic monoalkoxy titanate.

[0048] In some embodiments of this application, the polyol composition further includes bio-based polyether polyol and petroleum-based polyether polyol, with the mass ratio of the recycled polyol, the bio-based polyether polyol, and the petroleum-based polyether polyol being (40~50):(20~30):(20~40). Existing polyether compositions containing recycled polyols based on recycled PET have a low proportion of bio-based components and insufficient environmental friendliness. This application combines recycled polyols with bio-based polyether polyols while retaining a portion of petroleum-based polyether polyols to ensure system stability, thereby forming a polyether system that combines environmental friendliness and performance stability.

[0049] For example, the mass ratio of the recycled polyol, the bio-based polyether polyol, and the petroleum-based polyether polyol can be 40:20:40, 40:25:35, 40:30:30, 45:20:35, 45:25:30, 45:30:25, 50:20:30, 50:25:25, 50:30:20, or any range between the two aforementioned ratios.

[0050] Optionally, the sum of the masses of the recycled polyol and the bio-based polyether polyol accounts for more than 70% of the total mass of the polyol composition. For example, the sum of the masses of the recycled polyol and the bio-based polyether polyol accounts for 70%, 75%, 80%, 85%, 90%, 95% of the total mass of the polyol composition, or a range between any two of the aforementioned values.

[0051] Understandably, in existing polyether compositions containing recycled PET-based polyols, the total proportion of recycled and bio-based components is less than 50%, which is insufficient to meet the current high global environmental, social, and governance (ESG) requirements for enterprises and is detrimental to their sustainable development. This application achieves a total bio-based + recycled component proportion of ≥70% by controlling the sum of the mass of recycled polyols and bio-based polyether polyols to account for more than 70% of the total mass of the polyol composition. This improves the system's environmental friendliness, meets global ESG requirements for enterprises, and enhances their market competitiveness. At the same time, it retains a portion of petroleum-based polyether polyols to ensure system stability, forming a polyether system that combines environmental friendliness and performance stability.

[0052] Optionally, the hydroxyl value of the bio-based polyether polyol is 280 mgKOH / g to 320 mgKOH / g, and the hydroxyl value of the petroleum-based polyether polyol is 310 mgKOH / g to 350 mgKOH / g. By controlling the hydroxyl value of the bio-based polyether polyol to 280 mgKOH / g to 320 mgKOH / g and the hydroxyl value of the petroleum-based polyether polyol to 310 mgKOH / g to 350 mgKOH / g, this application can better match the reactivity of isocyanates, forming a suitable crosslinking density, and balancing the compressive strength and environmental friendliness of the polyurethane foam.

[0053] For example, the hydroxyl value of the bio-based polyether polyol can be 280 mg KOH / g, 285 mg KOH / g, 290 mg KOH / g, 300 mg KOH / g, 305 mg KOH / g, 310 mg KOH / g, 315 mg KOH / g, 320 mg KOH / g, or any range between two of the aforementioned values; the hydroxyl value of the petroleum-based polyether polyol can be 310 mg KOH / g, 315 mg KOH / g, 320 mg KOH / g, 325 mg KOH / g, 330 mg KOH / g, 335 mg KOH / g, 340 mg KOH / g, 345 mg KOH / g, 350 mg KOH / g, or any range between two of the aforementioned values.

[0054] Optionally, the bio-based polyether polyol is selected from one or more of castor oil-based polyether polyol, soybean oil-based polyether polyol, palm oil-based polyether polyol, rapeseed oil-based polyether polyol, linseed oil-based polyether polyol, and rosin-based polyether polyol.

[0055] Optionally, the petroleum-based polyether polyol is selected from one or more of polyether polyol 4110, polyether polyol 330N, polyether polyol 3050, polyether polyol 210, polyether polyol 403 and polyether polyol 630.

[0056] In some embodiments of this application, the combined polyether further includes a blowing agent, wherein the mass ratio of the blowing agent to the polyol composition is (3~5):100. By employing the aforementioned blowing agent, the combined polyether of this application facilitates the formation of a uniform and dense cell structure within the foam system, resulting in excellent mechanical properties of the polyurethane foam. Exemplarily, the mass ratio of the blowing agent to the polyol composition can be 3:100, 3.5:100, 4:100, 4.5:100, 5:100, or any range between the aforementioned values.

[0057] Optionally, the foaming agent is selected from one or more organic and inorganic foaming agents. The organic foaming agent includes one or more of 1,1,1,3,3-pentafluoropropane, cyclopentane, isopentane, n-pentane, and 1,3,3,3-tetrafluoropropylene (HFO-1234ze), and the inorganic foaming agent includes water. When the foaming agent includes both organic and inorganic foaming agents, the mass ratio of the inorganic foaming agent to the organic foaming agent is 1:(0.5~1), for example, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, or any range between the aforementioned values, to suit the requirements for foaming efficiency and foam density.

[0058] In some embodiments of this application, the combined polyether further includes a catalyst, wherein the mass ratio of the catalyst to the polyol composition is (0.5~1):100. By employing the aforementioned catalyst, the combined polyether of this application facilitates control of the reaction rate during the preparation of polyurethane foam using this combined polyether. Exemplarily, the mass ratio of the catalyst to the polyol composition can be 0.5:100, 0.6:100, 0.7:100, 0.8:100, 0.9:100, 1:100, or any range between two of the aforementioned values.

[0059] Optionally, the catalyst includes an organic amine catalyst, which may be selected from one or more of dimethylcyclohexylamine, triethylenediamine, diethanolamine, triethanolamine, N-methylmorpholine, N-ethylmorpholine, and bis(dimethylaminoethyl) ether. When any two of the aforementioned substances are used as the catalyst, the mass ratio of the two substances may be 1:1.

[0060] In some embodiments of this application, the combined polyether further includes a foam stabilizer, wherein the mass ratio of the foam stabilizer to the polyol composition is (1~2):100. By employing the aforementioned foam stabilizer, this application can improve cell stability, prevent cell collapse or merging during foaming, thereby facilitating the formation of a cross-linked skeleton and resulting in polyurethane foam with good mechanical properties. Exemplarily, the mass ratio of the foaming agent to the polyol composition can be 1:100, 1.1:100, 1.2:100, 1.3:100, 1.4:100, 1.5:100, 1.6:100, 1.7:100, 1.8:100, 1.9:100, 2:100, or any range between the aforementioned two values.

[0061] Optionally, the foam stabilizer may be selected from one or more of the following silicone surfactants: L-580, L-6880, L-6900, L-6988, DC-193, B-8404, and B-8462. Specifically, the silicone surfactants L-580, L-6880, L-6900, and L-6988 are manufactured by Momentive; the silicone surfactant DC-193 is manufactured by Dow Corning; and the silicone surfactants B-8404 and B-8462 are manufactured by Evonik.

[0062] Specifically, when the foam stabilizer is composed of two of the aforementioned organosilicon surfactants, the mass ratio of the two organosilicon surfactants can be 1:(0.5~1), for example, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1 or any range between the aforementioned two ratios.

[0063] This application also provides a polyurethane composition comprising isocyanate and the aforementioned combined polyether. Since this polyurethane composition employs all the technical solutions of the above embodiments, it possesses at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated upon here.

[0064] In some embodiments of this application, the mass ratio of the polyether to the isocyanate is 1:(1~1.2). By controlling the mass ratio of the polyether to the isocyanate within the above range, when polyurethane foam is prepared using this polyurethane composition, the reactivity of the isocyanate and the polyether is moderate, resulting in polyurethane foam with good mechanical properties. Exemplarily, the mass ratio of the polyether to the isocyanate can be 1:1, 1:1.11, 1:1.12, 1:1.13, 1:1.14, 1:1.15, 1:1.16, 1:1.17, 1:1.18, 1:1.19, 1:1.2, or any range between the aforementioned two ratios.

[0065] Optionally, the NCO content of the isocyanate is 28wt% to 32wt%. For example, the NCO content of the isocyanate can be 28wt%, 28.5wt%, 29wt%, 29.5wt%, 30wt%, 30.5wt%, 31wt%, 31.5wt%, 32wt%, or any range between the aforementioned two values.

[0066] Optionally, the isocyanate may include one or more of polymethylene polyphenyl isocyanate (PAPI), diphenylmethane diisocyanate (MDI), isophorone diisocyanate (IPDI), and toluene diisocyanate (TDI).

[0067] This application also provides a polyurethane foam, which is obtained by foaming the above-described polyurethane composition. Since this polyurethane foam adopts all the technical solutions of all the above embodiments, it possesses at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated upon here.

[0068] This application also provides a method for preparing polyurethane foam, such as... Figure 1 As shown, the method for preparing the polyurethane foam includes the following steps: S100. Waste PET raw materials, alcoholysis agent and alcoholysis catalyst are mixed and then subjected to alcoholysis reaction to obtain PET alcoholysis product; S200. The PET alcoholysis product is esterified with an organic acid anhydride at a mass ratio of 1:(0.08~0.12) to obtain a recycled polyol with a hydroxyl value of 300mgKOH / g~350mgKOH / g. S300. The recycled polyol is mixed with a foaming agent to obtain a combined polyether; S400. The combined polyether is mixed with isocyanate and foamed to obtain polyurethane foam.

[0069] The polyurethane foam preparation method provided in this application involves first breaking the PET molecular chains through alcoholysis of waste PET raw materials to obtain hydroxyl-containing alcoholysis products, and then modifying them by esterification with organic acid anhydrides to obtain recycled polyols. This method precisely controls the hydroxyl value of the recycled polyol to be 300 mg KOH / g to 350 mg KOH / g, a range similar to that of traditional petroleum-based polyether polyols (310 mg KOH / g to 350 mg KOH / g). Furthermore, it highly matches the reactivity of isocyanates, thereby increasing the substitution rate of recycled polyols for petroleum-based polyether polyols, significantly reducing raw material costs, and simultaneously achieving efficient recycling of waste PET, thus possessing both economic and environmental value.

[0070] In some embodiments of this application, step S100 includes: mixing waste PET raw materials, alcoholysis agent and alcoholysis catalyst at a mass ratio of 1:(1.2~1.5):(0.005~0.01), and carrying out alcoholysis reaction for 2h~3h (e.g. 2h, 2.5h or 3h) at 160℃~180℃ (e.g. 160℃, 165℃, 170℃, 175℃ or 180℃, etc.) and 0.1MPa~0.3MPa (e.g. 0.1MPa, 0.2MPa, 0.3MPa, etc.) to obtain PET alcoholysis product.

[0071] Optionally, in step S100, the waste PET raw material is obtained by washing, crushing, and drying waste PET bottles. Specifically, waste PET bottles can be washed, crushed, and dried to obtain waste PET fragments, which are the waste PET raw material.

[0072] In some embodiments of this application, step S200 includes: mixing the PET alcoholysis product with an organic acid anhydride at a mass ratio of 1:(0.08~0.12), and carrying out an esterification reaction at 120℃~140℃ (e.g. 120℃, 125℃, 130℃, 135℃ or 140℃, etc.) for 1.5h~2.5h (e.g. 1.5h, 2h or 2.5h, etc.) to obtain the regenerated polyol.

[0073] Optionally, in step S200, after the esterification reaction is completed, impurities are removed by vacuum distillation to obtain the regenerated polyol. The pressure of the vacuum distillation is -0.08 MPa to -0.1 MPa, and the distillation temperature is 150°C to 170°C. For example, the pressure of the vacuum distillation can be -0.08 MPa, -0.085 MPa, -0.09 MPa, -0.095 MPa, -0.1 MPa, or any range between two of the aforementioned values, and the distillation temperature can be 150°C, 152°C, 155°C, 158°C, 160°C, 162°C, 165°C, 168°C, 170°C, or any range between two of the aforementioned values.

[0074] In some embodiments of this application, step S300 includes: mixing the recycled polyol, bio-based polyether polyol, and petroleum-based polyether polyol to obtain a polyol composition; mixing the polyol composition with a titanate coupling agent, stirring and reacting at 80°C to 100°C (e.g., 80°C, 85°C, 90°C, 95°C, or 100°C) for 0.5h to 0.8h (e.g., 0.5h, 0.6h, 0.7h, or 0.8h); adding a catalyst, a foaming agent, and a foam stabilizer; continuing stirring for another 0.5h to 0.8h (e.g., 0.5h, 0.6h, 0.7h, or 0.8h); and cooling to 23°C to 27°C (e.g., 23°C, 24°C, 25°C, 26°C, or 27°C) to obtain a combined polyether.

[0075] Optionally, step S400 includes: mixing the combined polyether with isocyanate at a mass ratio of 1:(1~1.2) (e.g., 1:1, 1:1.1, or 1:1.2, etc.), stirring for 5s~10s (e.g., 5s, 6s, 7s, 8s, 9s, or 10s, etc.) at 25℃~35℃ (e.g., 25℃, 26℃, 27℃, 28℃, 29℃, 30℃, 31℃, 32℃, 33℃, 34℃, or 35℃, etc.), and then foaming and curing for 12h~24h (e.g., 12h, 15h, 18h, 20h, 22h, or 24h, etc.) at 23℃~27℃ (e.g., 23℃, 24℃, 25℃, 26℃, or 27℃, etc.) to obtain polyurethane foam.

[0076] The technical solutions and effects of this application will be described in detail below through specific embodiments and comparative examples. The following embodiments are only some embodiments of this application and are not intended to limit this application.

[0077] Raw material preparation: Alcoholization agent: Ethylene glycol (AR), purchased from Sinopharm Chemical Reagent Co., Ltd.

[0078] Alcohololysis catalyst: Zinc oxide (AR), purchased from Sinopharm Chemical Reagent Co., Ltd.

[0079] Organic acid anhydride: Phthalic anhydride (AR), purchased from Sinopharm Chemical Reagent Co., Ltd.

[0080] Bio-based polyether polyol: Castor oil-based polyether polyol with a hydroxyl value of 300 mg KOH / g, purchased from Changhua Chemical Technology Co., Ltd.

[0081] Petroleum-based polyether polyol: Polyether polyol 4110, with a hydroxyl value of 330 mg KOH / g, was purchased from Wuhan Lanabai Pharmaceutical Chemical Co., Ltd.

[0082] Titanate coupling agent: Isopropyl tristearate titanate (industrial grade), purchased from Nanjing Shuguang Chemical Group Co., Ltd.

[0083] Catalyst: Dimethylcyclohexylamine (industrial grade), purchased from BASF AG.

[0084] Foaming agent: distilled water (industrial grade), purchased from Hangzhou Wahaha Group Co., Ltd.

[0085] Foam stabilizer: L-580 silicone surfactant (industrial grade), purchased from BASF AG.

[0086] Isocyanate: Polymerized MDI (NCO content 30wt%, industrial grade), purchased from Wanhua Chemical Group Co., Ltd.

[0087] Example 1 (1) After cleaning and crushing the waste PET bottles, and drying them at 80°C for 2 hours, waste PET fragments with a particle size of 3.5 mm are obtained, which are the waste PET raw materials. (2) Mix waste PET fragments with ethylene glycol at a mass ratio of 1:1.3, then add 0.8% zinc oxide by mass of waste PET fragments, and carry out alcoholysis reaction at 170℃ and 0.2MPa for 2.5h to obtain PET alcoholysis product; (3) Add 10% of its mass of phthalic anhydride to the PET alcoholysis product, carry out esterification reaction at 130℃ for 2h, and then remove impurities by vacuum distillation at -0.09MPa and 160℃ for 1h to obtain regenerated polyol. (4) By mass, 45 parts of recycled polyol, 25 parts of castor oil-based polyether polyol and 30 parts of polyether polyol 4110 are mixed, 0.4 parts of isopropyl tristearate titanate are added, and the mixture is stirred at 90°C for 0.8 h. Then, 0.7 parts of dimethylcyclohexylamine, 4 parts of distilled water and 1.5 parts of organosilicon surfactant L-580 are added, and the mixture is stirred for another 0.5 h. The mixture is then cooled to 25°C to obtain the combined polyether. (5) Mix the polyether and polymeric MDI at a mass ratio of 1:1.1, stir at 30°C for 8 seconds, then inject into a mold and foam and cure at 25°C for 20 hours to obtain polyurethane foam.

[0088] Example 2 Example 2 is basically the same as Example 1, except that: in Example 2, the mass ratio of waste PET raw material, alcoholysis agent and alcoholysis catalyst is 1:1.2:0.008, the mass of phthalic anhydride is 8% of the mass of PET alcoholysis product, and the amount of isopropyl tristearate titanate added is 0.2 parts.

[0089] Example 3 Example 3 is basically the same as Example 1, except that: in Example 3, the mass ratio of waste PET raw material, alcoholysis agent and alcoholysis catalyst is 1:1.5:0.01, the mass of phthalic anhydride is 12% of the mass of PET alcoholysis product, and the amount of isopropyl tristearate titanate added is 0.6 parts.

[0090] Example 4 Example 4 is basically the same as Example 1, except that: in Example 4, the amount of recycled polyol added is 45 parts, the amount of castor oil-based polyether polyol added is 30 parts, the amount of petroleum-based polyether polyol added is 25 parts, and the amount of isopropyl tristearate titanate added is 0.3 parts.

[0091] Example 5 Example 5 is basically the same as Example 1, except that: in Example 5, the amount of recycled polyol added is 50 parts, the amount of castor oil-based polyether polyol added is 30 parts, the amount of petroleum-based polyether polyol added is 20 parts, and the amount of isopropyl tristearate titanate added is 0.5 parts.

[0092] Comparative Example 1 (1) After cleaning and crushing the waste PET bottles, and drying them at 80°C for 2 hours, waste PET fragments with a particle size of 3.5 mm are obtained, which are the waste PET raw materials. (2) The waste PET fragments and ethylene glycol were mixed at a mass ratio of 1:1.3, and then 0.8% zinc oxide of the waste PET fragments were added. The alcoholysis reaction was carried out at 170℃ and 0.2MPa for 2.5h to obtain a recycled polyol with a hydroxyl value of 270mgKOH / g. (3) By mass, 45 parts of recycled polyol and 55 parts of polyether polyol 4110 are mixed and stirred at 90°C for 0.8h. Then, 0.7 parts of dimethylcyclohexylamine, 4 parts of distilled water and 1.5 parts of organosilicon surfactant L-580 are added and stirred for another 0.5h. The mixture is then cooled to 25°C to obtain the combined polyether. (4) Mix the polyether and polymeric MDI at a mass ratio of 1:1.1, stir at 30°C for 8 seconds, then inject into a mold and foam and cure at 25°C for 20 hours to obtain polyurethane foam.

[0093] Comparative Example 2 Comparative Example 2 is basically the same as Example 1, except that isopropyl tristearate titanate was not added in step (4) of Comparative Example 2.

[0094] Comparative Example 3 Comparative Example 3 is basically the same as Example 1, except that: no castor oil-based polyether polyol was added in step (4) of Comparative Example 3, and the amount of polyether polyol 4110 added was 55 parts.

[0095] Comparative Example 4 (1) By mass, 100 parts of polyether polyol 4110 and 0.4 parts of isopropyl tristearate titanate were mixed and stirred at 90°C for 0.8h. Then, 0.7 parts of dimethylcyclohexylamine, 4 parts of distilled water and 1.5 parts of organosilicon surfactant L-580 were added and stirred for another 0.5h. The mixture was then cooled to 25°C to obtain the combined polyether. (2) Mix the polyether and polymeric MDI at a mass ratio of 1:1.1, stir at 30°C for 8 seconds, then inject into a mold and foam and cure at 25°C for 20 hours to obtain polyurethane foam.

[0096] Performance tests were conducted on the recycled polyols and polyurethane foams from Examples 1-5 and Comparative Examples 1-4. The test results are detailed in Table 1 below. The test items included: hydroxyl value of the recycled polyol, substitution rate of the recycled polyol for petroleum-based polyether polyol, reduction in raw material cost, cell uniformity and compressive strength of the polyurethane foam, and the total proportion of recycled and bio-based materials.

[0097] The method for testing the hydroxyl value of regenerated polyols is as follows: according to GB / T 12008.3-2009, the potentiometric titration method is used. After the sample undergoes an acylation reaction, excess acid is titrated with a standard alkaline solution, and the hydroxyl value is calculated based on the volume consumed.

[0098] The test method for cell uniformity is as follows: using a foam cell analyzer, take a slice of the center of the polyurethane foam, take a microscopic image, use image analysis software to statistically analyze the cell diameter distribution, and calculate the proportion of cells that meet the target particle size range, which is the cell uniformity of the polyurethane foam.

[0099] The test method for compressive strength is as follows: according to GB / T 8813-2022, the compressive strength of polyurethane foam is determined under the condition of a loading rate of 10 mm / min.

[0100] The total percentage of recycled polyols and bio-based polyols is calculated as follows: (sum of the mass of recycled polyols and bio-based polyether polyols / total mass of the polyol composition) × 100%.

[0101] Table 1

[0102] As shown in Table 1: The hydroxyl values ​​of the recycled polyols in Examples 1-5 were 300 mg KOH / g to 350 mg KOH / g, while the hydroxyl value of the recycled polyol in Comparative Example 1 was 270 mg KOH / g. The substitution rate of Examples 1-5 (45%-50%) was higher than that of Comparative Example 1 (25%), and the cost of Examples 1-5 was significantly lower than that of Comparative Example 1. This indicates that Examples 1-5, which produced recycled polyols by alcoholystomosis of waste PET raw materials followed by esterification, can precisely control the hydroxyl value of the recycled polyols to make them similar to those of petroleum-based polyether polyols, and significantly improve the reactivity matching with isocyanates, thereby achieving a stable reaction under a high substitution rate.

[0103] The cell uniformity (85%~94%) of the polyurethane foams in Examples 1~5 was higher than that of the polyurethane foam in Comparative Example 2 (78%), and the compressive strength (0.30MPa~0.38MPa) of the polyurethane foams in Examples 1~5 was higher than that of the polyurethane foam in Comparative Example 2 (0.22MPa). This indicates that by adding titanate coupling agent, the cell uniformity and compressive strength of the polyurethane foams in Examples 1~5 can be improved.

[0104] The polyurethane foams of Examples 1, 4, and 5 exhibited higher cell uniformity (90%~94%) and compressive strength (0.35MPa~0.38MPa) than the polyurethane foam of Example 2 (85% and 0.30MPa). The polyurethane foam of Example 3 showed similar cell uniformity (93%) and compressive strength (0.37MPa) to those of Examples 1, 4, and 5, indicating no significant performance improvement but increased cost. This demonstrates that Examples 1, 4, and 5, by controlling the amount of titanate coupling agent added to 0.3wt%~0.5wt% of the polyol composition, effectively improved the compatibility between recycled polyol and isocyanate, enhanced the cell uniformity and compressive strength of the polyurethane foam, and simultaneously controlled costs.

[0105] In Examples 1-5, the total proportion of bio-based and recycled polyols was 70%-80%, which meets ESG requirements. However, in Comparative Example 3, the total proportion of bio-based and recycled polyols was only 45%, which does not meet ESG requirements. Furthermore, the cost reduction ratio of Examples 1-5 (30%-35%) was similar to that of Comparative Example 3 (30%). This indicates that Examples 1-5 achieved a synergistic improvement in environmental performance and cost advantages by compounding recycled polyols with bio-based polyether polyols, with a total proportion of bio-based and recycled polyols ≥70%.

[0106] In Examples 1 and 3-5, with a substitution rate of 45%-50% and a cost reduction of 30%-35%, the cell uniformity of the polyurethane foam (90%-94%) is similar to that of the polyurethane foam in Comparative Example 4 (95%), and the compressive strength (0.35MPa-0.38MPa) is similar to that of the polyurethane foam in Comparative Example 4 (0.4MPa). At the same time, the proportion of bio-based + recycled-based materials (70%-80%) meets ESG requirements, achieving a synergistic unity of "environmental protection, cost reduction, and high performance", which has significant advantages over existing technologies.

[0107] In summary, this application has, but is not limited to, the following advantages: 1. Environmental and low-carbon benefits: It realizes the efficient recycling and utilization of waste PET raw materials, replaces 40%~50% of petroleum-based polyether polyols with recycled polyols, and blends recycled polyols with bio-based polyether polyols. The total proportion of bio-based + recycled polyols is ≥70%, which significantly reduces the consumption of non-renewable resources and carbon emissions, improves environmental protection, and meets ESG environmental and low-carbon requirements. 2. Significant cost advantages: Raw material costs can be reduced by about 30% compared to existing technologies, achieving both economic and environmental benefits; 3. Excellent mechanical properties: The compatibility is optimized by titanate coupling agent, so that the cell uniformity of polyurethane foam is ≥92%, which solves the defects of surface bubbles and uneven cell uniformity in the existing technology. In addition, the compressive strength of polyurethane foam is ≥0.3MPa, with stable performance, which can meet the application requirements of multiple fields such as building insulation and automotive interior.

[0108] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0109] The above provides a detailed description of the recycled polyols, combined polyethers, polyurethane compositions, polyurethane foams, and their preparation methods provided in the embodiments of this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A recycled polyol, characterized in that, The regenerated polyol is prepared by the following method: Waste PET raw materials, alcoholysis agent and alcoholysis catalyst are mixed and then subjected to alcoholysis reaction to obtain PET alcoholysis products; The PET alcoholysis product was esterified with an organic acid anhydride at a mass ratio of 1:(0.08~0.12) to obtain a recycled polyol with a hydroxyl value of 300mgKOH / g~350mgKOH / g.

2. The regenerated polyol according to claim 1, characterized in that, The mass ratio of the waste PET raw material, alcoholysis agent, and alcoholysis catalyst is 1:(1.2~1.5):(0.005~0.01); And / or, the alcoholysis reaction is carried out at a temperature of 160℃~180℃, a pressure of 0.1MPa~0.3MPa, and a reaction time of 2h~3h; And / or, the alcoholysis agent comprises a diol selected from one or more of ethylene glycol, propylene glycol, 1,4-butanediol, diethylene glycol, 1,3-propanediol, and neopentyl glycol; And / or, the alcoholysis catalyst is selected from one or more of zinc oxide, zinc acetate, magnesium oxide, calcium oxide, lead acetate and tetrabutyl titanate; And / or, the waste PET raw material is obtained from waste PET bottles after washing, crushing and drying.

3. The recycled polyol according to claim 1, characterized in that, The esterification reaction is carried out at a temperature of 120℃~140℃ for a reaction time of 1.5h~2.5h. And / or, the organic acid anhydride is selected from one or more of phthalic anhydride, succinic anhydride, maleic anhydride, fumaric anhydride, adipic anhydride and trimellitic anhydride; And / or, after the esterification reaction is completed, impurities are removed by vacuum distillation to obtain the regenerated polyol, wherein the vacuum distillation pressure is -0.08MPa to -0.1MPa and the distillation temperature is 150℃ to 170℃.

4. A composite polyether, characterized in that, The composition includes a polyol composition comprising the recycled polyol according to any one of claims 1 to 3.

5. The composite polyether according to claim 4, characterized in that, The polyether composition also includes a titanate coupling agent.

6. The composite polyether according to claim 5, characterized in that, The mass ratio of the titanate coupling agent to the polyol composition is (0.3~0.5):100; And / or, the titanate coupling agent is selected from one or more of isopropyl tristearoyl titanate, isopropyl tris(dioctyl pyrophosphoyloxy) titanate, tetraisopropyl di(dioctyl phosphite) titanate, di(dioctyl pyrophosphoyloxy) ethylene titanate, isopropyl tris(stearoyloxy) titanate and octylphosphonic monoalkoxy titanate.

7. The composite polyether according to claim 4, characterized in that, The polyol composition further includes bio-based polyether polyol and petroleum-based polyether polyol, wherein the mass ratio of the recycled polyol, the bio-based polyether polyol and the petroleum-based polyether polyol is (40~50):(20~30):(20~40).

8. The composite polyether according to claim 7, characterized in that, The sum of the masses of the recycled polyol and the bio-based polyether polyol accounts for more than 70% of the total mass of the polyol composition; And / or, the hydroxyl value of the bio-based polyether polyol is 280 mg KOH / g to 320 mg KOH / g, and the hydroxyl value of the petroleum-based polyether polyol is 310 mg KOH / g to 350 mg KOH / g; And / or, the bio-based polyether polyol is selected from one or more of castor oil-based polyether polyol, soybean oil-based polyether polyol, palm oil-based polyether polyol, rapeseed oil-based polyether polyol, linseed oil-based polyether polyol and rosin-based polyether polyol; And / or, the petroleum-based polyether polyol is selected from one or more of polyether polyol 4110, polyether polyol 330N, polyether polyol 3050, polyether polyol 210, polyether polyol 403 and polyether polyol 630.

9. The composite polyether according to claim 4, characterized in that, The combined polyether further includes at least one of a catalyst, a blowing agent, and a foam stabilizer, wherein the mass ratio of the catalyst to the polyol composition is (0.5~1):100, the mass ratio of the blowing agent to the polyol composition is (3~5):100, and the mass ratio of the foam stabilizer to the polyol composition is (1~2):

100.

10. The composite polyether according to claim 9, characterized in that, The catalyst includes an organic amine catalyst, which is selected from one or more of dimethylcyclohexylamine, triethylenediamine, N-methylmorpholine, bis(dimethylaminoethyl) ether, triethanolamine, N-ethylmorpholine, and diethanolamine; And / or, the foaming agent is selected from one or more of organic and inorganic foaming agents, wherein the organic foaming agent includes one or more of 1,1,1,3,3-pentafluoropropane, cyclopentane, isopentane, n-pentane and 1,3,3,3-tetrafluoropropene, and the inorganic foaming agent includes water; And / or, the foam stabilizer is selected from one or more of the following: silicone surfactant L-580, silicone surfactant L-6880, silicone surfactant L-6900, silicone surfactant L-6988, silicone surfactant DC-193, silicone surfactant B-8404, and silicone surfactant B-8462.

11. A polyurethane composition, characterized in that, The polyurethane composition comprises isocyanate and the combined polyether according to any one of claims 4 to 10.

12. The polyurethane composition according to claim 11, characterized in that, The mass ratio of the combined polyether to the isocyanate is 1:(1~1.2); And / or, the NCO content of the isocyanate is 28wt%~32wt%.

13. A polyurethane foam, characterized in that, The polyurethane foam is obtained by foaming the polyurethane composition according to any one of claims 11 to 12.

14. A method for preparing polyurethane foam, characterized in that, Includes the following steps: S100. Waste PET raw materials, alcoholysis agent and alcoholysis catalyst are mixed and then subjected to alcoholysis reaction to obtain PET alcoholysis product; S200. The PET alcoholysis product is esterified with an organic acid anhydride at a mass ratio of 1:(0.08~0.12) to obtain a recycled polyol with a hydroxyl value of 300mgKOH / g~350mgKOH / g. S300. The recycled polyol is mixed with a foaming agent to obtain a combined polyether; S400. The combined polyether is mixed with isocyanate and foamed to obtain polyurethane foam.

15. The method for preparing polyurethane foam according to claim 14, characterized in that, Step S100 includes: mixing waste PET raw materials, alcoholysis agent and alcoholysis catalyst at a mass ratio of 1:(1.2~1.5):(0.005~0.01), and carrying out alcoholysis reaction at 160℃~180℃ and 0.1MPa~0.3MPa for 2h~3h to obtain PET alcoholysis product; And / or, in step S100, the waste PET raw material is obtained from waste PET bottles after washing, crushing and drying.

16. The method for preparing polyurethane foam according to claim 14 or 15, characterized in that, Step S200 includes: mixing the PET alcoholysis product with an organic acid anhydride at a mass ratio of 1:(0.08~0.12), and carrying out an esterification reaction at 120℃~140℃ for 1.5h~2.5h to obtain the regenerated polyol; And / or, in step S200, after the esterification reaction is completed, impurities are removed by vacuum distillation to obtain the regenerated polyol, wherein the pressure of vacuum distillation is -0.08MPa to -0.1MPa and the distillation temperature is 150℃ to 170℃.

17. The method for preparing polyurethane foam according to claim 14, characterized in that, Step S300 includes: mixing the recycled polyol, bio-based polyether polyol, and petroleum-based polyether polyol to obtain a polyol composition; mixing the polyol composition with a titanate coupling agent, stirring and reacting at 80°C to 100°C for 0.5h to 0.8h, then adding a catalyst, a foaming agent, and a foam stabilizer, continuing to stir for 0.5h to 0.8h, and cooling to 23°C to 27°C to obtain a combined polyether. And / or, step S400 includes: mixing the combined polyether with isocyanate at a mass ratio of 1:(1~1.2), stirring at 25℃~35℃ for 5s~10s, and then foaming and curing at 23℃~27℃ for 12h~24h to obtain polyurethane foam.

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