A kind of synthetic method of polyether polyol

Abstract

The present application belongs to the technical field of polyether polyol synthesis, and relates to a method for synthesizing polyether polyol. The method comprises the following steps: 1) mixing polyol, zinc oxide photocatalyst, reducing agent, and epoxy monomer to obtain polyether oligomer; 2) mixing the polyether oligomer obtained in step 1) with DMC catalyst and epoxy monomer to obtain polyether polyol. The present invention uses photocatalysis to replace the base-catalyzed polymerization in the traditional scheme to prepare the oligomer polyether polyol starter, realizes the one-pot preparation of polyether polyol, reduces the cumbersome post-treatment of the oligomer starter, and reduces the wastewater volume and process cycle of the polyether polyol production process.

Description

Technical Field

[0001] The present application belongs to the technical field of polyether polyol synthesis and relates to a method for synthesizing polyether polyol. Background Art

[0002] Polyether polyols are oligomers with ether bonds (-ROR-) in the main chain and more than 2 hydroxyl groups (-OH) in the end or side groups. They are formed by ring-opening polymerization with oxidized olefins under the action of a catalyst using low molecular weight polyols, polyamines or compounds containing active hydrogen as initiators. Oxidized olefins are mainly propylene oxide PO and ethylene oxide EO, among which propylene oxide is the most common. Polyol initiators include diols such as propylene glycol and ethylene glycol, triols such as glycerol and trimethylolpropane, and polyols such as pentaerythritol, xylitol, sorbitol, and sucrose; amine initiators include diethylamine, diethylenetriamine, etc. Polyether polyols of different functionalities can be obtained according to the number of active atoms contained in the initiator. The most commonly used polyethers in the preparation of polyurethane adhesives are polyoxypropylene diol and polyoxypropylene triol, and there is also polytetrahydrofuran diol. Polyurethane resin adhesives prepared with polyol esters have good water resistance, impact resistance and low temperature resistance.

[0003] The traditional production method of polyether polyols is to prepare polyether polyols by anionic ring-opening polymerization of oxidized olefins using active hydrogen-containing compounds as initiators in the presence of KOH catalyst. Although the catalyst price is relatively low, the refining time is long, the by-product content in the product is large, the quality of the polyether polyols is poor, and more importantly, it is impossible to produce polyether polyols with high relative molecular weight and low unsaturation, which seriously limits the application range of polyether polyols.

[0004] Double metal cyanide catalysts were successfully developed by General Rubber & Tire Company in the United States in the 1960s and used in the preparation of polyether polyols. The company has evaluated dozens of double metal cyanides, and the results show that single double metal cyanide has no catalytic activity, and only DMC and ligands form DMC complexes to show catalytic activity, and zinc cobalt cyanide complexes have the best performance. Before the 1990s, DMC catalysts were mainly zinc hexacyanocobaltate complexes coordinated with ethylene glycol dimethyl ether. Later, Asahi Glass Co., Ltd. of Japan proposed a DMC catalyst coordinated with tert-butanol; Arco used tert-butanol as a ligand in its patent US5470813A to prepare an amorphous DMC catalyst, and used polyether polymer compounds as ligands in US5482908A to further improve the activity of the double metal cyanide catalyst, and called the amorphous catalyst coordinated with tert-butanol and polyether polyols the third-generation DMC catalyst, that is, an ultra-high activity DMC catalyst; Bayer developed a process for the continuous production of low-unsaturation polyethers in WO0047649A1, bringing this technology to a new level.

[0005] The polyether products produced by DMC catalyst have lower unsaturation and faster rate than KOH, but they are easily affected by the water content in the system: when there is water in the system, water and PO will react to form 1,2-propylene glycol, which will form a stable chelate with DMC, thus making it lose its catalytic ability; similarly, when using small molecule initiators such as glycerol, because the hydroxyl groups they contain are close to each other, it is easy to form this chelate with DMC, resulting in a long induction period or the reaction cannot occur. Only when using high molecular weight polyols as initiators, it is difficult to form this chelate due to the large distance between the hydroxyl groups, so it will not affect the catalytic performance of DMC. In addition to using higher molecular weight starting polyols as the central structure of polyether polymerization, another solution is to first perform preliminary polymerization of ethylene glycol under alkaline catalytic conditions, use polymer polyols with a degree of polymerization of more than 300 as initiators, and then perform subsequent polymerization in the DMC catalytic system. For example, Bayer in CN101108896A and BASF in CN101535364A both use oligomers prepared from ethylene glycol as the starting raw materials for the reaction.

[0006] By initially polymerizing small molecules such as ethylene glycol to form polyether oligomers, it is possible to effectively avoid the formation of chelates between monomers and DMC catalysts, which can lead to catalyst deactivation. However, oligomers that are initially polymerized using base catalysis require certain post-treatments, mainly including: neutralizing residual base catalysts with acidic substances, removing generated salts with adsorbents, and then using high-temperature gas stripping to reduce the moisture in the material to below 500 ppm; the treatment process has extremely strict requirements for the water removal step, and a small amount of residual moisture will cause the epoxy structure to hydrolyze to form diols in subsequent reactions, and further lead to the deactivation of the DMC catalyst. Patent CN107200837A proposes a continuous production method to obtain a mixed product of oligomers and polymers, and use the oligomers in the product to circulate as the starting molecules for the reaction.

[0007] Photocatalytic polymerization is a type of free radical polymerization. Monomer molecules are activated into free radicals by light (or photosensitizer) and then undergo chain polymerization. Photopolymerization refers to the method of polymerizing monomers by photochemical reaction. This method can obtain pure polymers that do not contain various initiator residues. Patent CN104710609A uses TiO2 catalyst photocatalysis to achieve the production of polyethers, but the product is quite different from the DMC catalytic system.

[0008] Among all kinds of photocatalytic materials, ZnO has become one of the most popular materials due to its low price, good chemical and photochemical stability, and non-polluting materials. Zinc oxide has many different structures, such as nanowires, nanotubes, nanorods, and microspheres. Among them, ZnO mesoporous microspheres have broad application prospects in the field of photocatalysis due to their adjustable pore structure, high surface charge transfer rate, and high specific surface area. Summary of the invention

[0009] The present application is made to solve the above-mentioned problems, and aims to provide a method for synthesizing polyether polyols to solve the problems in the prior art.

[0010] The present invention provides a method for synthesizing a polyether polyol, the method comprising the following steps:

[0011] 1) mixing a polyol, a zinc oxide photocatalyst, a reducing agent, and an epoxy monomer to obtain a polyether oligomer;

[0012] 2) The polyether oligomer obtained in step 1) is mixed with a DMC catalyst and an epoxy monomer to obtain a polyether polyol.

[0013] In some embodiments of the present invention, in step 1), the polyol is selected from one or more of ethylene glycol, propylene glycol, glycerol, trimethylolpropane, pentaerythritol, xylitol, sorbitol, and sucrose.

[0014] In some embodiments of the present invention, in step 1), the zinc oxide photocatalyst is 1-2% by weight of the polyol.

[0015] In some embodiments of the present invention, in step 1), the zinc oxide photocatalyst is a mesoporous zinc oxide microsphere photocatalyst.

[0016] In some embodiments of the present invention, in step 1), the reducing agent is 0.1-0.2% by weight of the polyol.

[0017] In some embodiments of the present invention, in step 1), the epoxy monomer is 5-20 molar equivalents of the polyol.

[0018] In some embodiments of the present invention, in step 1), the reducing agent is selected from formaldehyde and / or hydrazine hydrate.

[0019] In some embodiments of the present invention, in step 1), the epoxy monomer is selected from ethylene oxide and / or propylene oxide.

[0020] In some embodiments of the present invention, in step 1), the reaction system is irradiated with natural light or ultraviolet light.

[0021] In some embodiments of the present invention, in step 1), the reaction temperature is 70-80°C.

[0022] In some embodiments of the present invention, in step 1), the reaction time is 2-3 hours.

[0023] In some embodiments of the present invention, the method for preparing the zinc oxide photocatalyst comprises: mixing a polymer, a water-soluble zinc salt, and an alcohol amine to obtain a zinc precursor solution, reacting at a certain temperature, and obtaining a zinc oxide photocatalyst after post-treatment.

[0024] In some embodiments of the present invention, the polymer is selected from one or two of polystyrene-polyethylene oxide polymer and polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer.

[0025] In some embodiments of the invention, the polymer is dissolved using alcohol.

[0026] In some embodiments of the present invention, the molar ratio of the polymer to the zinc precursor solution is (0.1-2):1.

[0027] In some embodiments of the present invention, the water-soluble zinc salt is selected from one or more of zinc nitrate, zinc acetate, zinc sulfate and zinc chloride.

[0028] In some embodiments of the present invention, the mass volume ratio of the polymer to the alcohol amine is (1-20) g: (0.1-1) mL.

[0029] In some embodiments of the present invention, the alcoholamine is selected from diethanolamine or triethanolamine.

[0030] In some embodiments of the present invention, the polymer, zinc salt and alcohol amine are mixed and dissolved and then stirred for 3-8 hours.

[0031] In some embodiments of the present invention, the reaction temperature is 100-200°C.

[0032] In some embodiments of the present invention, the reaction time is 12-48 hours.

[0033] In some embodiments of the present invention, the post-treatment includes filtering, washing, and drying.

[0034] In some embodiments of the present invention, in step 2), the polyether oligomer is mixed with a DMC catalyst to obtain a suspension, which is dried under reduced pressure at 110-160° C.; after drying, the suspension is cooled to the reaction temperature.

[0035] In some embodiments of the present invention, in step 2), the amount of DMC catalyst used is less than 0.02% of the total mass of the polyether oligomer and the epoxy monomer in step 2).

[0036] In some embodiments of the present invention, the amount of the epoxy monomer used in step 2) is 60-75 molar equivalents of the polyol.

[0037] In some embodiments of the present invention, in step 2), the epoxy monomer is added for 4-5 hours.

[0038] In some embodiments of the present invention, in step 2), the epoxy monomer is selected from propylene oxide and / or ethylene oxide.

[0039] In some embodiments of the present invention, in step 2), the reaction temperature is 85-140°C.

[0040] In some embodiments of the present invention, in step 2), a portion of the epoxy monomer is first added, and after the DMC catalyst is activated, the remaining epoxy monomer is added, during which the concentration of the free epoxy monomer is ensured not to exceed 5%.

[0041] In some embodiments of the present invention, step 2) further comprises recovering the epoxy monomer after the reaction is completed.

[0042] In some embodiments of the present invention, the recovery conditions are any one or more of the following:

[0043] Under nitrogen atmosphere;

[0044] The temperature is 120-200°C;

[0045] The pressure is 50mbar-0.5bar;

[0046] The time is 1-5h.

[0047] In some embodiments of the present invention, in step 1), after the reaction is completed, the step further includes filtering while hot to recover the zinc oxide photocatalyst; or; in step 2), after the reaction is completed, the step further includes filtering while hot to recover the zinc oxide photocatalyst.

[0048] This application has the following beneficial effects:

[0049] The present invention provides a new preparation method of polyether polyols, which uses photocatalysis to replace the base-catalyzed polymerization in the traditional scheme to prepare oligomeric polyether polyol initiators, thereby realizing the preparation of polyether polyols, reducing the cumbersome post-treatment of oligomeric initiators, and reducing the amount of wastewater and process cycle of the polyether polyol production process. The zinc oxide catalyst can be physically recovered after the reaction is completed, and it is not necessary to add acid for neutralization like the post-treatment of base catalysis, thereby avoiding the generation of salt and water in the system. When the first-stage reaction is completed, the illumination can be stopped immediately, and the DMC catalyst can be added to enter the subsequent polymerization step. DETAILED DESCRIPTION

[0050] Hereinafter, a specific embodiment of a method for synthesizing a polyether polyol is described in detail.

[0051] When DMC catalyst uses small molecule initiators such as ethylene glycol and glycerol, the two hydroxyl groups are close to each other and are easy to form chelates with Zn in DMC, which prolongs the induction period of the reaction or even makes the reaction impossible. Therefore, the substrate of the reaction must be a higher polyol without a chelate structure, or a polyether oligomer that has achieved a certain degree of polymerization of lower alcohols such as ethylene glycol using other conditions. At this time, due to the large distance between the hydroxyl groups, it is difficult to form this chelate, so it will not affect the catalytic performance of DMC. Moreover, the polyol oligomer that has undergone preliminary polymerization needs to be acidified to neutralize the alkalinity, and then washed with water to remove the residual salt, and then dried to make the water content of the material not higher than 500ppm, which is a cumbersome step.

[0052] The present invention provides a new preparation method of polyether polyols, which uses photocatalysis to replace the base-catalyzed polymerization in the traditional scheme to prepare oligomeric polyether polyol starters, thereby realizing a one-pot preparation of polyether polyols, reducing the cumbersome post-treatment of oligomeric starters, and reducing the amount of wastewater and process cycle of the polyether polyol production process.

[0053] Photocatalytic polymerization is a type of free radical polymerization. Monomers can be directly excited by light to cause polymerization, or photosensitizers and photoinitiators can be excited by light to cause polymerization. Zinc oxide is an important semiconductor oxide (broadband 37eV), and the excitation bond energy is 60meV at room temperature. After the catalyst is irradiated by light, it absorbs energy, electrons transition, and free electrons and holes are generated. Free electrons generate free radicals to participate in the reaction. In order to reduce the recombination of electrons and holes, a small amount of reducing agent needs to be added to eliminate holes and improve reaction efficiency.

[0054] The catalyst excitation process is stable and slow, which shortens the induction period of the polymerization reaction and accelerates the reaction start-up. On the other hand, the polymerization reaction proceeds slowly at a certain reaction speed, which makes the product quality stable, the molecular weight distribution narrow, and the volatility of the hydroxyl value small. The amount of free radicals generated during the polymerization process is based on light and is not affected by the system temperature. The starting and reaction temperatures of the reaction are both low. Because the amount of free radicals generated is relatively constant, the speed of the polymerization reaction is stable, the system pressure is reduced, the risk in the production process is reduced, and the safety is improved.

[0055] Most importantly, the zinc oxide photocatalyst can be physically recovered after the reaction is completed, without the need to add acid for neutralization as in the post-treatment of base catalysis, thus avoiding the generation of salt and water in the system. When the first stage of the reaction is completed, the illumination can be stopped immediately, and the DMC catalyst can be added to enter the subsequent polymerization step.

[0056] In summary, the present invention uses the above-mentioned photocatalytically obtained polyether polyol oligomer as a starting material, and after the above-mentioned reaction is completed after the light irradiation is removed, the prepared DMC catalyst solution can be directly added to the reaction, and a subsequent polymerization reaction is carried out and the zinc oxide photocatalyst is recovered after the reaction is completed, or the zinc oxide photocatalyst is recovered after the polyether oligomer is synthesized. On this basis, the present application is completed.

[0057] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0058] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0059] [Synthesis method of polyether polyol]

[0060] The present application provides a method for synthesizing a polyether polyol, the method comprising the following steps:

[0061] 1) mixing a polyol, a zinc oxide photocatalyst, a reducing agent, and an epoxy monomer to obtain a polyether oligomer;

[0062] 2) The polyether oligomer obtained in step 1) is mixed with a DMC catalyst and an epoxy monomer to obtain a polyether polyol.

[0063] In the method for synthesizing polyether polyol provided by the present invention, step 1) is to mix polyol, zinc oxide photocatalyst, reducing agent and epoxy monomer to obtain polyether oligomer. Specifically:

[0064] In step 1) of the present invention, the polyol is selected from one or more of ethylene glycol, propylene glycol, glycerol, trimethylolpropane, pentaerythritol, xylitol, sorbitol and sucrose.

[0065] In step 1) of the present invention, the zinc oxide photocatalyst is 1-2% by weight of the polyol. Alternatively, the zinc oxide photocatalyst can be, for example, 1-1.5% or 1.5-2% by weight of the polyol.

[0066] In step 1) of the present invention, the zinc oxide photocatalyst is a mesoporous zinc oxide microsphere photocatalyst.

[0067] In step 1) of the present invention, the zinc oxide photocatalyst can be directly purchased or prepared by the following method:

[0068] The preparation method of the zinc oxide photocatalyst comprises: mixing a polymer, a water-soluble zinc salt and an alcohol amine to obtain a zinc precursor solution, reacting at a certain temperature, and obtaining the zinc oxide photocatalyst after post-treatment.

[0069] In the preparation method of the zinc oxide photocatalyst provided by the present invention, the polymer is selected from one or two of polystyrene-polyethylene oxide polymer and polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer.

[0070] In the preparation method of the zinc oxide photocatalyst provided by the present invention, the polymer is dissolved in alcohol. The alcohol may be, for example, methanol, ethanol, etc. In some embodiments, the mass volume ratio of the polymer to the alcohol is (1-20) g: (100-1000) mL.

[0071] In the preparation method of the zinc oxide photocatalyst provided by the present invention, the molar ratio of the polymer to the zinc precursor solution is (0.1-2): 1. Optionally, the molar ratio of the polymer to the zinc precursor solution is (0.1-1): 1, (1-2): 1, (0.1-0.5): 1, (0.5-1): 1, (1-1.5): 1 or (1.5-2): 1, etc.

[0072] In the method for preparing the zinc oxide photocatalyst provided by the present invention, the water-soluble zinc salt is selected from one or more of zinc nitrate, zinc acetate, zinc sulfate and zinc chloride.

[0073] In the preparation method of the zinc oxide photocatalyst provided by the present invention, the mass volume ratio of the polymer to the alcohol amine is (1-20) g: (0.1-1) mL.

[0074] In the method for preparing the zinc oxide photocatalyst provided by the present invention, the alcoholamine is selected from diethanolamine or triethanolamine.

[0075] In the preparation method of the zinc oxide photocatalyst provided by the present invention, the polymer, the water-soluble zinc salt and the alcohol amine are mixed and dissolved, and then stirred for 3-8 hours. Optionally, the stirring is carried out for 3-5 hours, 5-8 hours, etc.

[0076] In the method for preparing the zinc oxide photocatalyst provided by the present invention, the reaction temperature is 100-200° C. Optionally, the reaction temperature is 100-120° C., 120-200° C., 120-150° C., 150-200° C., etc.

[0077] In the method for preparing the zinc oxide photocatalyst provided by the present invention, the reaction time is 12-48 hours. Optionally, the reaction time can be, for example, 12-24 hours or 24-48 hours.

[0078] In the preparation method of zinc oxide photocatalyst provided by the present invention, the post-treatment includes filtering, washing and drying. After filtering, white powder is obtained, and washing is performed by centrifugal washing with alcohol and water. The drying temperature is 50-100°C.

[0079] In a specific embodiment, for example, 1-20 g of polystyrene-polyoxyethylene polymer can be weighed, dissolved in 100 mL of methanol, and stirred until the polymer is completely dissolved. A water-soluble zinc salt is weighed and added according to a molar ratio of 0.1-2 between the polymer unit and the zinc precursor, and then 0.1-1 mL of diethanolamine or triethanolamine is added, and stirring is continued for 3 to 8 hours after dissolution to obtain a zinc precursor solution; the solution is placed in a reactor, reacted at 100 to 200 ° C for 12 to 48 hours, filtered to obtain a white powder, washed with alcohol and water by centrifugation, and dried at 50 to 100 ° C to obtain a mesoporous zinc oxide microsphere photocatalyst. The water-soluble zinc salt can be one of zinc nitrate, zinc acetate, zinc sulfate, and zinc chloride.

[0080] In step 1) of the present invention, the reducing agent is 0.1-0.2% by weight of the polyol. Alternatively, the reducing agent can be, for example, 0.1-0.15% or 0.15-0.2% by weight of the polyol.

[0081] In step 1) of the present invention, the reducing agent is selected from formaldehyde and / or hydrazine hydrate.

[0082] In step 1) of the present invention, the epoxy monomer is 5-20 molar equivalents of the polyol. Alternatively, the epoxy monomer can be, for example, 5-10 molar equivalents, 10-15 molar equivalents, or 15-20 molar equivalents of the polyol.

[0083] In step 1) of the present invention, the epoxy monomer is selected from ethylene oxide (EO) and / or propylene oxide (PO).

[0084] In step 1) of the present invention, the reaction system is irradiated with natural light or ultraviolet light. The ultraviolet light can be, for example, 378nm ultraviolet light. In the case of natural light, the power of the light source is 200-500W; it can be 200-300W or 300-500W, etc. In the case of ultraviolet light irradiation, the power of the light source is 85-125W.

[0085] In step 1) of the present invention, the reaction temperature is 70-80° C. Alternatively, the reaction temperature may be, for example, 70-75° C. or 75-80° C.

[0086] In step 1) of the present invention, the reaction time is 2-3 hours. Optionally, the reaction time can be, for example, 2-2.5 hours or 2.5-3 hours.

[0087] In a specific embodiment, for example, polyols (including ethylene glycol and glycerol, etc.) can be added to a reaction vessel, 1-2% of the weight of the polyols as a photocatalyst and 0.1-0.2% of a reducing agent can be added to the reaction vessel, ethylene oxide or propylene oxide can be introduced after nitrogen replacement, and the materials can be fully contacted and mixed uniformly by stirring and external circulation; the reaction system can be irradiated with natural light or 378nm ultraviolet light, and the temperature can be raised to 70-80°C, and the reaction can be maintained within this temperature range for 2-3 hours. The amount of ethylene oxide or propylene oxide added is determined according to the molecular weight of the polyether oligomer produced, which is 5-20 molar equivalents of the polyol.

[0088] The molecular weight of the polyether oligomer obtained in step 1) of the present invention may be, for example, 200-1000. Alternatively, the molecular weight of the polyether oligomer may be, for example, 200-300, 300-500 or 500-1000, etc.

[0089] In the method for synthesizing polyether polyols provided by the present invention, step 2) the polyether oligomer obtained in step 1) is mixed with a DMC catalyst and an epoxy monomer to obtain a polyether polyol. Specifically:

[0090] In step 2) of the present invention, the polyether oligomer is mixed with a DMC catalyst to obtain a suspension, which is dried under reduced pressure at 110-160° C. The temperature may be 110-130° C. or 130-160° C., etc. The drying time may be, for example, 1-5 hours, 1-2 hours or 2-5 hours.

[0091] In step 2) of the present invention, the mass of the DMC catalyst is less than 0.02% of the total mass of the polyether oligomer and the epoxy monomer in step 2) to meet the requirement that the concentration of the DMC catalyst in the final product is lower than 200 ppm.

[0092] In step 2) of the present invention, the amount of epoxy monomer used is 60-75 molar equivalents of the polyol used.

[0093] In step 2) of the present invention, the temperature is lowered to the reaction temperature after drying, and the reaction temperature can be, for example, 85-140° C., and can be 85-120° C., 85-100° C., 100-110° C., 110-120° C., 100-120° C., 120-130° C., 110-130° C., 130-140° C., etc. Preferably, it is 110-130° C. Then, a portion of epoxy monomer is added, and after the catalyst is successfully activated, the subsequent epoxy monomer is continuously added, during which the concentration of free propylene oxide is ensured not to exceed 5%.

[0094] The amount of the first part of epoxy monomer added is, for example, 0.1-0.5% of the total amount of epoxy monomer used in step 2.

[0095] The epoxy monomer is added for 4-5 hours, for example, 4-4.5 hours or 4.5-5 hours.

[0096] In step 2) of the present invention, the epoxy monomer is recovered after the reaction is completed. The recovery conditions include one or more of the following characteristics:

[0097] Under nitrogen atmosphere;

[0098] The temperature is 120-200°C; it can be selected as 120-150°C or 150-200°C, etc.

[0099] The pressure is 50mbar-0.5bar; optional is 50mbar-0.1bar, 0.1bar-0.3bar or 0.3bar-0.5bar, etc.

[0100] The time is 1-5h; it can be selected as 1-3h or 3-5h, etc.

[0101] In one specific embodiment, DMC catalytic polymerization: for example, the suspension obtained by mixing the prepared polyol oligomer and the DMC catalyst is dried under reduced pressure at 110-160°C for 1-5h. After the mixture is cooled to the reaction temperature, a small amount of epoxy monomer is added. After the catalyst is successfully activated, the subsequent propylene oxide is continued to be added, during which the concentration of free propylene oxide is ensured not to exceed 5%. All epoxy monomers are added within 4.5h. After the reaction is completed, the crude product is stripped with nitrogen at a temperature of 120-200°C and a pressure of 50mbar-0.5bar for 1-5h to recover the epoxy monomer. The amount of DMC catalyst used should be less than 0.02% of the raw material to meet the requirement that the DMC catalyst concentration in the final product is less than 50ppm. The epoxy monomer is propylene oxide or a mixture of propylene oxide and ethylene oxide, and the amount can be adjusted according to the target molecular weight.

[0102] In step 2) of the present invention, the DMC catalyst can be prepared, for example, by the following method:

[0103] The aqueous solution of potassium hexacyanocobaltate and the aqueous solution of zinc chloride are stirred and then centrifuged to collect the precipitate, and the precipitate is added to the aqueous solution of tert-butyl alcohol for several times and stirred, centrifuged and vacuum dried to obtain a DMC catalyst (double metal cyanide complex catalyst).

[0104] Specifically:

[0105] In the preparation of the DMC catalyst, the aqueous solution of potassium hexacyanocobaltate is a 5%-15% aqueous solution of potassium hexacyanocobaltate.

[0106] In the preparation of DMC catalyst, the zinc chloride aqueous solution is a 20-40% zinc chloride aqueous solution.

[0107] In the preparation of DMC catalyst, the molar ratio of potassium hexacyanocobaltate to zinc chloride is (1-5): 1. It can be (1-3): 1 or (3-5): 1.

[0108] In the preparation of the DMC catalyst, an aqueous solution of potassium hexacyanocobaltate and an aqueous solution of zinc chloride are combined, centrifuged, stirred, separated, and the precipitate is collected, which is defined as a primary precipitation.

[0109] In the preparation of DMC catalyst, tert-butanol aqueous solution is first added, stirred, and then centrifuged to collect the precipitate, which is defined as the secondary precipitation. The weight of the tert-butanol aqueous solution is 3-10 times that of the primary precipitation. The tert-butanol aqueous solution is a 50% tert-butanol aqueous solution. The stirring time can be, for example, 0.5-4h, optionally 0.5-2h or 2-4h, etc.

[0110] In the preparation of DMC catalyst, the tert-butanol aqueous solution is added to the secondary precipitate again, stirred, and then centrifuged to collect the precipitate, which is defined as the third precipitate. The weight of the tert-butanol aqueous solution is 3-10 times that of the secondary precipitate. The tert-butanol aqueous solution is a 50% tert-butanol aqueous solution. The heating temperature is 100-150°C, and can be 100-130°C or 130-150°C. The stirring time can be, for example, 0.5h.

[0111] In a specific embodiment, potassium hexacyanocobaltate is prepared as a 5%-15% aqueous solution; zinc chloride is prepared as a 20-40% aqueous solution; potassium hexacyanocobaltate and zinc chloride are weighed in a molar ratio of 1-5:1. The two solutions are combined and stirred for 40 minutes and then centrifuged to collect a primary precipitate. The primary precipitate is ground into powder using a mortar, stirred for 0.5-4 hours after adding 3-10 times the weight of a 50% tert-butanol aqueous solution, centrifuged again, and a secondary precipitate is collected; 3-10 times the weight of a 50% tert-butanol aqueous solution is added to the secondary precipitate again, heated to 100-150°C for 0.5 hours and then centrifuged. The resulting tertiary precipitate is vacuum dried to obtain a double metal cyanide complex catalyst.

[0112] In the present invention, in step 1), after the reaction is completed, the step further includes filtering while hot to recover the zinc oxide photocatalyst; or;

[0113] In step 2), after the reaction is completed, the zinc oxide photocatalyst is recovered by hot filtration, which is a one-pot reaction.

[0114] The beneficial effects of the present application are further illustrated below in conjunction with embodiments.

[0115] In order to make the invention purpose, technical scheme and beneficial technical effect of the present application clearer, the present application is further described in detail below in conjunction with the examples. However, it should be understood that the examples of the present application are only for explaining the present application, not for limiting the present application, and the examples of the present application are not limited to the examples given in the specification. The specific experimental conditions or operating conditions not specified in the examples are made under conventional conditions, or are made under the conditions recommended by the material supplier.

[0116] In addition, it should be understood that one or more method steps mentioned in this application do not exclude the existence of other method steps before or after the combination step or the insertion of other method steps between these explicitly mentioned steps, unless otherwise specified; it should also be understood that the combination connection relationship between one or more devices / apparatuses mentioned in this application does not exclude the existence of other devices / apparatuses before or after the combination device / apparatus or the insertion of other devices / apparatuses between these two explicitly mentioned devices / apparatuses, unless otherwise specified. Moreover, unless otherwise specified, the numbering of each method step is only a convenient tool for identifying each method step, and is not intended to limit the order of arrangement of each method step or the scope of implementation of this application. Changes or adjustments in their relative relationships shall also be regarded as the scope of implementation of this application without substantial changes in the technical content.

[0117] In the following examples, the reagents, materials and instruments used are all commercially available unless otherwise specified.

[0118] Unless otherwise specified, the purity of each product in each embodiment of the present application exceeds 98%.

[0119] Example 1: Preparation of photocatalyst

[0120] Weigh 100g of polystyrene-polyoxyethylene polymer, dissolve it in 1000mL of alcohol, and stir until the polymer is completely dissolved. Weigh 1.1eq (221g, 0.74mol) of zinc nitrate hexahydrate relative to the molar amount of the polymer unit and add it, then add 5mL of triethanolamine, continue stirring for 5h after dissolution, and obtain a zinc precursor solution. Place the solution in a reactor, react at 120°C for 24 hours, filter to obtain a white powder, rinse with alcohol and water by centrifugation, and dry at 50-100°C to obtain a zinc oxide photocatalyst.

[0121] Example 2: Photocatalytic initial polymerization, oligomer retention

[0122] Weigh 12.4kg of ethylene glycol, add it to a 150L pressure-resistant container with a peephole, then add 150g of zinc oxide photocatalyst particles prepared in Example 1 and 15g of anhydrous formaldehyde, introduce nitrogen to replace the air and then vent to normal pressure, add 58kg of propylene oxide, mix the materials evenly by stirring and external circulation, irradiate white light into the reaction system through a peephole, and heat the reaction system to 70°C to maintain the pressure in the reaction system at 2.5bar. Keep the temperature of the reaction system below 75°C, and turn off the illumination after 2.5 hours to stop the reaction. Filter and recover the zinc oxide catalyst while hot, wash with water and then dry. The prepared polyether oligomer is weighed, the residual propylene oxide monomer is recovered by vacuum distillation, and the residual monomer is vacuum-dried with an oil pump, and the propylene oxide conversion rate is calculated again by weighing.

[0123] Changing the light source conditions, comparing the effects of the reaction conditions on the conversion rate, as shown in Table 1:

[0124] Table 1

[0125] serial number Light Type Light source power / W PO conversion rate / % 2-1 White light 300 98.2 2-2 378nm 85 97.6 2-3 378nm 125 97.9 2-4 White light 100 15.3 2-5 White light 150 45.1

[0126] Example 3: DMC catalyst preparation

[0127] Prepare 148g of 11% potassium hexacyanocobaltate aqueous solution (0.05mol) and add it to 65g of 38.5% zinc chloride (0.184mol) aqueous solution, stir for 40min and then centrifuge to collect the precipitate. Grind the solid precipitate into powder using a mortar, stir for 2h after adding 5 times the weight of 50% tert-butanol aqueous solution, centrifuge again and collect the precipitate; add 5 times the weight of 50% tert-butanol aqueous solution to the solid, stir and heat to 130°C for 0.5h and then centrifuge. The obtained precipitate is vacuum dried to obtain a double metal cyanide complex (DMC) catalyst.

[0128] Example 4: Subsequent polymerization of oligomers using DMC catalysts

[0129] 7.04 kg of initiator polyol oligomer and 3.1 g of DMC catalyst were added to a 150 L reactor. The suspension obtained by mixing was dried at 130 ° C and reduced pressure (20 mbar) for 2 h. The mixture was cooled to 110 ° C and maintained, and then 200 g of propylene oxide was added. After the catalyst was successfully activated, the subsequent propylene oxide was gradually added, during which the concentration of free propylene oxide was ensured not to exceed 5%. A total of 87.2 kg of propylene oxide was added in 4.5 h. After the reaction was completed, the reactor was depressurized and the product was stripped at 150 ° C / 50 mbar for 3 h with the help of nitrogen. The product weight was 94.3 kg in total, M n =4708 g / mol; P D =1.08

[0130] Change the epoxy dosage and reaction temperature as shown in Table 2:

[0131] Table 2

[0132]

[0133]

[0134] Example 5: One-pot method of converting DMC system after initial photocatalytic polymerization and finally filtering out zinc oxide

[0135] Weigh 1.24 kg (20 mol) of ethylene glycol and add it to a 150 L reactor. Then add 15 g of zinc oxide photocatalyst particles and 1.5 g of anhydrous formaldehyde, introduce nitrogen to replace the air and vent to normal pressure, add 5.8 kg of propylene oxide, mix the materials evenly through stirring and external circulation, irradiate white light into the reaction system through a peep window, heat the reaction system to 70 ° C, and maintain the pressure in the reaction system at 2.5 bar. Keep the temperature of the reaction system below 75 ° C, and turn off the light after 2.5 hours to stop the reaction.

[0136] 3.1 g of DMC catalyst was weighed and added to the reactor. The suspension obtained by mixing was dried at 130°C and reduced pressure (20 mbar) for 2 h. The mixture was cooled to 110°C, and then 200 g of propylene oxide was added. After the catalyst was successfully activated, the subsequent propylene oxide was added, and the concentration of free propylene oxide was ensured not to exceed 5%. A total of 87.2 kg of propylene oxide was added within 4.5 h.

[0137] After the reaction is completed, the reactor is decompressed and filtered while hot to recover the zinc oxide catalyst, which is then washed with water and dried for storage. The crude product is stripped with nitrogen at 150°C / 50 mbar for 3 hours. The product weight is 93.9 kg, M n =4685 g / mol; P D =1.08.

[0138] The above implementations are preferred cases of the present application and are not intended to limit the protection scope of the present application. However, the present application is not limited to the specific details of the above implementations. Within the technical concept of the present application, the technical solution of the present application can be subjected to a variety of simple modifications, and these simple modifications all belong to the protection scope of the present application.

[0139] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this application will not further describe various possible combinations.

Claims

1. A method for synthesizing a polyether polyol, characterized in that: The method comprises the following steps: 1) mixing a polyol, a zinc oxide photocatalyst, a reducing agent, and an epoxy monomer to obtain a polyether oligomer; 2) The polyether oligomer obtained in step 1) is mixed with a DMC catalyst and an epoxy monomer to obtain a polyether polyol.

2. The method for synthesizing polyether polyol according to claim 1, characterized in that: In step 1), the polyol is selected from one or more of ethylene glycol, propylene glycol, glycerol, trimethylolpropane, pentaerythritol, xylitol, sorbitol and sucrose.

3. The method for synthesizing polyether polyol according to claim 1, characterized in that: Also includes any one or more of the following features: A1) in step 1), the zinc oxide photocatalyst is 1-2% by weight of the polyol; A2) in step 1), the zinc oxide photocatalyst is a mesoporous zinc oxide microsphere photocatalyst; A3) in step 1), the reducing agent is 0.1-0.2% by weight of the polyol; A4) in step 1), the epoxy monomer is 5-20 molar equivalents of the polyol; A5) In step 1), the reducing agent is selected from formaldehyde and / or hydrazine hydrate; A6) in step 1), the epoxy monomer is selected from ethylene oxide and / or propylene oxide; A7) In step 1), the reaction system is irradiated with natural light or ultraviolet light; A8) In step 1), the reaction temperature is 70-80°C; A9) In step 1), the reaction time is 2-3 hours.

4. The method for synthesizing polyether polyol according to claim 1, characterized in that: The preparation method of the zinc oxide photocatalyst comprises: mixing a polymer, a water-soluble zinc salt and an alcohol amine to obtain a zinc precursor solution, reacting at a certain temperature, and obtaining the zinc oxide photocatalyst after post-treatment.

5. The method for synthesizing polyether polyol according to claim 4, characterized in that: Also includes any one or more of the following features: B1) the polymer is selected from one or two of a polystyrene-polyethylene oxide polymer and a polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer; B2) the polymer is dissolved using alcohol; B3) the molar ratio of the polymer to the zinc precursor solution is (0.1-2):1; B4) the water-soluble zinc salt is selected from one or more of zinc nitrate, zinc acetate, zinc sulfate and zinc chloride; B5) the mass volume ratio of the polymer and the alcohol amine is (1-20) g: (0.1-1) mL; B6) the alcoholamine is selected from diethanolamine or triethanolamine; B7) mixing and dissolving the polymer, zinc salt and alcohol amine and stirring for 3-8 hours; B8) the reaction temperature is 100-200°C; B9) reaction time is 12-48 hours; B10) The post-treatment includes filtering, washing and drying.

6. The method for synthesizing polyether polyol according to claim 1, characterized in that: Also includes any one or more of the following features: C1) In step 2), the polyether oligomer is mixed with a DMC catalyst to obtain a suspension, which is dried under reduced pressure at 110-160° C.; after drying, the suspension is cooled to the reaction temperature; C2) in step 2), the amount of DMC catalyst used is less than 0.02% of the total mass of the polyether oligomer and the epoxy monomer in step 2); C3) the epoxy monomer used in step 2) is 60-75 molar equivalents of the polyol; C4) in step 2), the epoxy monomer is added for 4-5 hours; C5) In step 2), the epoxy monomer is selected from propylene oxide and / or ethylene oxide.

7. The method for synthesizing polyether polyol according to claim 6, characterized in that: Also includes any one or more of the following features: C11) In step 2), the reaction temperature is 85-140°C; C31) In step 2), a portion of the epoxy monomer is first added, and after the DMC catalyst is activated, the remaining portion of the epoxy monomer is added, during which the concentration of the free epoxy monomer is ensured not to exceed 5%.

8. The method for synthesizing polyether polyol according to claim 1, characterized in that: Step 2) also includes recovering the epoxy monomer after the reaction is completed.

9. The method for synthesizing polyether polyol according to claim 8, characterized in that: The recycling conditions are any one or more of the following: D1) Under nitrogen atmosphere; D2) temperature is 120-200°C; D3) pressure is 50mbar-0.5bar; D4) time is 1-5h.

10. The method for synthesizing polyether polyol according to claim 1, characterized in that: In step 1), after the reaction is completed, the step further includes filtering while hot to recover the zinc oxide photocatalyst; or; In step 2), after the reaction is completed, the step further includes filtering while hot to recover the zinc oxide photocatalyst.

Images