Preparation method of polyether carbonate polyol

Abstract

The present invention provides a method for preparing a polyether carbonate polyol, and belongs to the technical field of synthetic materials. The preparation method provided by the present invention uses an ionic liquid and a Lewis acid as a dual catalyst system, and adopts ring-opening polymerization of ethylene carbonate to prepare the polyether carbonate polyol without adding an additional initiator or chain transfer agent. The method innovatively proposes a dual catalyst system, which prompts ethylene carbonate to release ethylene glycol by itself and efficiently converts it into polyether carbonate polyol, effectively overcoming the shortcomings of the existing catalyst system, such as low activity, long reaction time, and inability to be recycled, and effectively improving the conversion efficiency of ethylene carbonate.

Description

Technical Field

[0001] The invention belongs to the technical field of synthetic materials, and in particular relates to a method for preparing polyether carbonate polyol. Background Art

[0002] As the raw material of polyurethane materials, oligomer polyols are divided into three categories according to the main chain structure: polyether polyols, polyester polyols and polycarbonate polyols. Among them, polycarbonate polyurethane has good tensile properties, abrasion resistance and solvent resistance. Because the molecular chain segments are embedded with carbonate groups, it also has excellent biodegradability and can be used as coatings, adhesives or leather slurries.

[0003] In recent years, the preparation of polyether carbonate polyols by copolymerization of carbon dioxide and epoxide has attracted much attention from the scientific research community and the industry. This type of research mainly uses carbon dioxide and propylene oxide or ethylene oxide to copolymerize under catalyst conditions to obtain polyols with carbonate bonds and ether bond structures. For example, patents CN103781818B and CN107428928B of Covestro Germany Co., Ltd. obtain polyether carbonate polyols by adding alkylene oxide and carbon dioxide in the presence of a double metal cyanide (DMC) catalyst or in the presence of a metal complex catalyst based on metal zinc and / or cobalt. Chinese patent CN105542142B uses a rare earth-doped double metal cyanide catalyst system and a chain transfer agent.

[0004] However, this new type of polyol using carbon dioxide as a raw material not only requires high pressure during the reaction process, but also has problems with its own structure: (1) the polyol has poor reactivity, and the terminal hydroxyl groups of the prepared polyol are mainly secondary hydroxyl groups, resulting in low activity of the polyol when reacting with isocyanate; (2) it is necessary to add a small molecule initiator and a chain transfer agent, and there is no method for separating unreacted ethylene carbonate and a method for catalyzing the reaction;

[0005] (3) Due to the high glass transition temperature of this type of polyol, the polyurethane material prepared therefrom has poor low temperature resistance and insufficient toughness, which limits its application range. Therefore, it is urgent for the art to provide a method for preparing polyether carbonate polyols with simple reaction conditions, high conversion rate, and easy separation of the reaction product from the raw materials and the catalyst system. Summary of the invention

[0006] The invention provides a method for preparing polyether carbonate polyols. The method innovatively proposes a dual catalyst system to promote ethylene carbonate to release ethylene glycol by itself and efficiently convert it into polyether carbonate polyols, effectively overcoming the shortcomings of the existing catalyst system such as low activity, long reaction time and inability to be recycled, and effectively improving the conversion efficiency of ethylene carbonate.

[0007] In order to achieve the above object, the present invention provides a method for preparing polyether carbonate polyol, which is prepared by ring-opening polymerization of ethylene carbonate using ionic liquid and Lewis acid as a dual catalyst system without adding additional initiator or chain transfer agent.

[0008] As a preference, the method comprises the following steps:

[0009] The reaction conditions are mild. After the reaction is completed, the unreacted ethylene carbonate, polyether carbonate polyol and catalyst system are separated by molecular distillation, and then the catalyst system is extracted with ethyl acetate. The specific steps are as follows:

[0010] At 45-60°C, add ionic liquid and Lewis acid catalyst system to ethylene carbonate, stir evenly, introduce nitrogen protection, and heat reaction under stirring;

[0011] After the reaction is completed, the reaction liquid is separated by molecular distillation to obtain light component unreacted ethylene carbonate and heavy component polyether carbonate polyol;

[0012] 1 to 10 parts by weight of an acetate solvent is added to the heavy component polyether carbonate polyol for extraction. After extraction and concentration, an extracted and recovered catalyst system and polyether carbonate polyol are obtained respectively.

[0013] Preferably, the ionic liquid is an imidazolium ionic liquid bromide, selected from at least one of 1-ethyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium bromide, 1-butyl-2-methyl-3-methylimidazolium bromide, 1-n-hexyl-3-methylimidazolium bromide, 1-benzyl-3-methylimidazolium bromide, 1-(2-hydroxyethyl)-3-methylimidazolium bromide and 1,2-dimethyl-3-propyl-imidazolium bromide.

[0014] Preferably, the Lewis acid is at least one selected from potassium bromide, magnesium bromide, calcium bromide, manganese bromide, copper bromide, ferric chloride, aluminum chloride, cesium chloride and cesium bromide.

[0015] Preferably, the molar amount of the added ionic liquid is 0.05% to 5% of the mass of ethylene carbonate; and the mass of the added Lewis acid is 0.01% to 10% of the mass of ethylene carbonate.

[0016] It is understandable that the amount of the above-mentioned ionic liquid added needs to be strictly limited to the above-mentioned range. Too much will not only increase the cost, but also introduce high-temperature degradation products of the ionic liquid. Too little will result in too low activity, which is not conducive to the conversion of ethylene carbonate. Similarly, too much Lewis acid added will cause the decomposition of ethylene carbonate, and the solubility of Lewis acid is limited. Too little will not be able to synergize with the ionic liquid.

[0017] Preferably, the heating reaction temperature is 140 to 230° C., preferably 160 to 220° C., more preferably 170 to 210° C., and the reaction time is 1 to 20 h.

[0018] Preferably, the molecular distillation is carried out at a vacuum degree of 1 to 2000 Pa and a temperature of 140 to 200°C, preferably at a vacuum degree of 1 to 1000 Pa and a temperature of 150 to 180°C.

[0019] Preferably, the acetate solvent is selected from at least one of methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate and tert-butyl acetate, and its usage is 1 to 10 times, preferably 1 to 5 times, the mass of the polyether carbonate polyol.

[0020] Preferably, the structural formula of the obtained polyether carbonate polyol is as follows:

[0021] (CH 2 CH 2 O) x (CH 2 CH 2 OC(O)O) y

[0022] Among them, the ratio of x:y is 5-8, and the number average molecular weight is 1900-2400.

[0023] Preferably, the carbon dioxide unit content in the obtained polyether carbonate polyol is 12wt%-15wt%, and the ethylene carbonate conversion rate is ≥95%.

[0024] Compared with the prior art, the advantages and positive effects of the present invention are:

[0025] 1. The preparation method of the polyether carbonate polyol provided by the present invention uses a simple and easily available ionic liquid and Lewis acid as a dual catalyst system, and adopts the ring-opening polymerization of ethylene carbonate to prepare the polyether carbonate polyol without adding an initiator and a chain transfer agent.

[0026] 2. In the method provided by the present invention, the ionic liquid is an imidazole bromide salt, and the Lewis acid is zinc bromide, magnesium bromide, etc. The two substances act synergistically to form a homogeneous system, activate the carbonyl group, promote the release of ethylene glycol from ethylene carbonate itself, and efficiently convert it into polyether carbonate polyols.

[0027] 3. After the reaction is completed, the method provided by the present invention can also effectively separate the product and the incompletely converted ethylene carbonate by molecular distillation.

[0028] 4. The method provided by the present invention can effectively overcome the shortcomings of the existing catalyst system, such as low activity, long reaction time, and inability to be recycled, has good catalytic activity, and effectively improves the conversion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is the hydrogen nuclear magnetic resonance spectrum of the polyether carbonate polyol provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] Example 1

[0032] In a 500 ml round-bottom flask, heat 100 g of ethylene carbonate to 45°C, which is now in liquid state. Add 0.11 g of ionic liquid 1-ethyl-3-methylimidazolium bromide and 0.2 g of anhydrous magnesium bromide, introduce nitrogen protection, stir, heat to 190°C, and react for 4 hours.

[0033] The reaction solution was transferred to a molecular distillation sampling tank, kept at 50°C, the vacuum degree was set to 900 Pa, the temperature was set to 170°C, and the light component collected was 3g of ethylene carbonate, and the heavy component was mainly 60g of polyether carbonate polyol.

[0034] Add 5 times the weight of ethyl acetate to the polyether carbonate polyol, put it into a separatory funnel, mix it evenly, and then let it stand for stratification and collect it separately. The lower layer is the viscous polyether carbonate polyol, which is transferred to a round-bottom flask and kept under vacuum for 2 hours to remove the residual ethyl acetate. The upper layer is the ethyl acetate phase, which is transferred to a round-bottom flask and the ethyl acetate solvent is removed by rotary evaporation under the conditions of -0.09Mpa and a water bath temperature of 45°C to obtain an ionic liquid and Lewis acid catalyst system that is extracted and recovered.

[0035] The number average molecular weight of the polyether carbonate polyol was determined to be 2100 by GPC. The carbon dioxide unit content in the polyol obtained in this example was about 12 wt % by NMR. The hydrogen NMR spectrum was as follows: Figure 1 shown.

[0036] Example 2

[0037] In a 500 ml round-bottom flask, heat 100 g of ethylene carbonate to 50°C, which is now in liquid state. Add 1.20 g of ionic liquid 1-butyl-3-methylimidazolium bromide and 2.10 g of anhydrous magnesium bromide, introduce nitrogen protection, stir, heat to 140°C, and react for 4 hours.

[0038] The reaction solution was transferred to a molecular distillation sampling tank, kept at 50°C, the vacuum degree was set to 1500 Pa, the temperature was set to 200°C, and the light component collected was 2g of ethylene carbonate, and the heavy component was mainly 61g of polyether carbonate polyol.

[0039] Add 6 times the weight of methyl acetate to the polyether carbonate polyol, put it into a separatory funnel, mix well, and then let it stand for stratification and collect them separately. The lower layer is the viscous polyether carbonate polyol, which is transferred to a round-bottom flask and kept under vacuum for 2 hours to remove the residual ethyl acetate. The upper layer is the ethyl acetate phase, which is transferred to a round-bottom flask and the methyl acetate solvent is removed by rotary evaporation under the conditions of -0.09Mpa and a water bath temperature of 45°C to obtain an ionic liquid and Lewis acid catalyst system that is extracted and recovered.

[0040] The molecular weight of the polyether carbonate polyol was determined by GPC, and the number average molecular weight was 2400. The content of carbon dioxide units in the polyol obtained in this example was determined by nuclear magnetic resonance (NMR) to be about 15 wt %.

[0041] Example 3

[0042] In a 500 ml round-bottom flask, heat 100 g of ethylene carbonate to 50°C, which is now in liquid state. Add 0.65 g of ionic liquid 1-butyl-2-methyl-3-methylimidazolium bromide and 1.02 g of anhydrous magnesium bromide, then introduce nitrogen protection, stir, heat to 170°C, and react for 4 hours.

[0043] The reaction solution was transferred to a molecular distillation sampling tank, kept at 50°C, set the vacuum degree to 500 Pa, and the temperature to 150°C. The light component collected was 3g of ethylene carbonate, and the heavy component was mainly 58g of polyether carbonate polyol.

[0044] Add 7 times the weight of ethyl acetate to the polyether carbonate polyol, put it in a separatory funnel, mix it evenly, and then let it stand for stratification and collect it separately. The lower layer is the viscous polyether carbonate polyol, which is transferred to a round-bottom flask and kept under vacuum for 2 hours to remove the residual ethyl acetate. The upper layer is the ethyl acetate phase, which is transferred to a round-bottom flask and the ethyl acetate solvent is removed by rotary evaporation under the conditions of -0.09Mpa and a water bath temperature of 45°C to obtain an ionic liquid and Lewis acid catalyst system that is extracted and recovered.

[0045] The molecular weight of the polyether carbonate polyol was determined by GPC, and the number average molecular weight was 2200. The content of carbon dioxide units in the polyol obtained in this example was determined by nuclear magnetic resonance (NMR) to be about 13 wt %.

[0046] Example 4

[0047] In a 500 ml round-bottom flask, heat 100 g of ethylene carbonate to 60°C, which is now in liquid state. Add 2.62 g of ionic liquid 1-butyl-2-methyl-3-methylimidazolium bromide and 0.2 g of anhydrous magnesium bromide, then introduce nitrogen protection, stir, heat to 190°C, and react for 4 hours.

[0048] The reaction solution was transferred to a molecular distillation sampling tank, kept at 50°C, the vacuum degree was set to 900 Pa, the temperature was set to 170°C, and the light component collected was 2g of ethylene carbonate, and the heavy component was mainly 60g of polyether carbonate polyol.

[0049] Add 6 times the weight of ethyl acetate to the polyether carbonate polyol, put it in a separatory funnel, mix it evenly, and then let it stand for stratification and collect it separately. The lower layer is the viscous polyether carbonate polyol, which is transferred to a round-bottom flask and kept under vacuum for 2 hours to remove the residual ethyl acetate. The upper layer is the ethyl acetate phase, which is transferred to a round-bottom flask and the ethyl acetate solvent is removed by rotary evaporation under the conditions of -0.09Mpa and a water bath temperature of 45°C to obtain an ionic liquid and Lewis acid catalyst system that is extracted and recovered.

[0050] The molecular weight of the polyether carbonate polyol was determined by GPC, and the number average molecular weight was 1900. The content of carbon dioxide units in the polyol obtained in this example was determined by nuclear magnetic resonance (NMR) to be about 12 wt %.

[0051] Example 5

[0052] In a 500 ml round-bottom flask, heat 100 g of ethylene carbonate to 50°C, which is now in liquid state. Add 0.13 g of ionic liquid 1-butyl-2-methyl-3-methylimidazolium bromide and 0.2 g of anhydrous aluminum chloride, then introduce nitrogen protection, stir, heat to 210°C, and react for 4 hours.

[0053] The reaction solution was transferred to a molecular distillation sampling tank, kept at 50°C, the vacuum degree was set to 400 Pa, the temperature was set to 200°C, and the light component collected was 1g of ethylene carbonate, and the heavy component was mainly 62g of polyether carbonate polyol.

[0054] Add 10 times the weight of ethyl acetate to the polyether carbonate polyol, put it into a separatory funnel, mix it evenly, and then let it stand for stratification and collect it separately. The lower layer is the viscous polyether carbonate polyol, which is transferred to a round-bottom flask and kept under vacuum for 2 hours to remove the residual ethyl acetate. The upper layer is the ethyl acetate phase, which is transferred to a round-bottom flask and the ethyl acetate solvent is removed by rotary evaporation under the conditions of -0.09Mpa and a water bath temperature of 45°C to obtain an ionic liquid and Lewis acid catalyst system that is extracted and recovered.

[0055] The molecular weight of the polyether carbonate polyol was determined by GPC, and the number average molecular weight was 1950. The carbon dioxide unit content in the polyol obtained in this example was about 12 wt % as determined by nuclear magnetic resonance.

[0056] Example 6

[0057] In a 500 ml round-bottom flask, heat 100 g of ethylene carbonate to 50°C, which is now in liquid state. Add 0.05 g of ionic liquid 1-(2-hydroxyethyl)-3-methylimidazolium bromide and 0.01 g of anhydrous ferric chloride, introduce nitrogen protection, stir, heat to 230°C, and react for 4 hours.

[0058] The reaction solution was transferred to a molecular distillation sampling tank, kept at 50°C, the vacuum degree was set to 2000 Pa, the temperature was set to 200°C, and the light component collected was 5g of ethylene carbonate, and the heavy component was mainly 54g of polyether carbonate polyol.

[0059] Add 10 times the weight of ethyl acetate to the polyether carbonate polyol, put it into a separatory funnel, mix it evenly, and then let it stand for stratification and collect it separately. The lower layer is the viscous polyether carbonate polyol, which is transferred to a round-bottom flask and kept under vacuum for 2 hours to remove the residual ethyl acetate. The upper layer is the ethyl acetate phase, which is transferred to a round-bottom flask and the ethyl acetate solvent is removed by rotary evaporation under the conditions of -0.09Mpa and a water bath temperature of 45°C to obtain an ionic liquid and Lewis acid catalyst system that is extracted and recovered.

[0060] The molecular weight of the polyether carbonate polyol was determined by GPC, and the number average molecular weight was 2300. The content of carbon dioxide units in the polyol obtained in this example was determined by nuclear magnetic resonance (NMR) to be about 13 wt %.

[0061] Comparative Example 1

[0062] In a 500 ml round-bottom flask, heat 100 g of ethylene carbonate to 50°C, which is now in liquid state. Add 0.13 g of ionic liquid 1-ethyl-3-methylimidazolium bromide, introduce nitrogen protection, stir, heat to 210°C, and react for 4 hours.

[0063] The reaction solution was transferred to a molecular distillation sampling tank, kept at 50°C, the vacuum degree was set to 2000 Pa, the temperature was set to 200°C, and the light component collected was 55g of ethylene carbonate, and the heavy component was mainly 23g of polyether carbonate polyol.

[0064] Comparative Example 2

[0065] In a 500 ml round-bottom flask, heat 100 g of ethylene carbonate to 50°C. At this time, it is in a liquid state. Add 0.15 g of anhydrous magnesium bromide salt and introduce nitrogen protection. Stir and heat to 210°C. React for 4 hours.

[0066] The reaction solution was transferred to a molecular distillation sampling tank, kept at 50°C, set the vacuum degree to 2000 Pa, and the temperature to 200°C. The light component collected was 99 g of ethylene carbonate, and there was basically no polyether carbonate polyol.

[0067] The catalytic effects of the dual catalytic systems of ionic liquid and Lewis acid involved in the above Examples 1-6 and Comparative Examples 1-2 were tested, and the test results are shown in Table 1.

[0068] Table 1 Experimental results of ionic liquid and Lewis acid catalysis

[0069]

[0070]

[0071] Combined with the data in Table 1, it can be seen that compared with using only one catalyst, the dual catalyst system of the present invention can significantly improve the conversion rate of ethylene carbonate, mainly because the two substances work synergistically to form a homogeneous system, activate the carbonyl group, promote ethylene carbonate to release ethylene glycol, and efficiently convert it into polyether carbonate polyols.

Claims

1. A method for preparing polyether carbonate polyols, It is characterized in that It is prepared by ring-opening polymerization of ethylene carbonate using ionic liquid and Lewis acid as a dual catalyst system without adding additional initiator or chain transfer agent. The ionic liquid is selected from at least one of 1-ethyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium bromide, 1-butyl-2-methyl-3-methylimidazolium bromide, and 1-(2-hydroxyethyl)-3-methylimidazolium bromide; the Lewis acid is selected from at least one of anhydrous magnesium bromide, anhydrous ferric chloride, and anhydrous aluminum chloride.

2. The preparation method according to claim 1, It is characterized in that The following steps are involved: The reaction conditions are mild. After the reaction is completed, unreacted ethylene carbonate and polyether carbonate polyol are separated by molecular distillation, and then the catalyst system is extracted with ethyl acetate. The specific steps are as follows: At 45-60°C, add ionic liquid and Lewis acid catalyst system to ethylene carbonate, stir evenly, introduce nitrogen protection, and heat reaction under stirring; After the reaction is completed, the reaction liquid is separated by molecular distillation to obtain light component unreacted ethylene carbonate and heavy component polyether carbonate polyol; 1 to 10 parts by weight of an acetate solvent is added to the heavy component polyether carbonate polyol for extraction. After extraction and concentration, an extracted and recovered catalyst system and polyether carbonate polyol are obtained respectively.

3. The preparation method according to claim 2, It is characterized in that The molar amount of the added ionic liquid is 0.05% to 5% of the mass of ethylene carbonate; the mass of the added Lewis acid is 0.01% to 10% of the mass of ethylene carbonate.

4. The preparation method according to claim 2, It is characterized in that The heating reaction temperature is 140-230°C, and the reaction time is 1-20h.

5. The preparation method according to claim 2, It is characterized in that The molecular distillation is carried out at a vacuum degree of 1 to 2000 Pa and a temperature of 140 to 200°C.

6. The preparation method according to claim 2, It is characterized in that The acetate solvent is selected from at least one of methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate and tert-butyl acetate, and its usage is 1 to 10 times the mass of the polyether carbonate polyol.

7. The preparation method according to any one of claims 1 to 6, It is characterized in that The structural formula of the obtained polyether carbonate polyol is as follows: (CH 2 CH 2 O) x (CH 2 CH 2 OC(O)O) y Among them, the ratio of x:y is 5-8, and the number average molecular weight is 1900-2400.

8. The preparation method according to claim 7, It is characterized in that The carbon dioxide unit content in the obtained polyether carbonate polyol is 12wt%-15wt%, and the ethylene carbonate conversion rate is ≥95%.

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