Preparation method of polyether polyol

Abstract

The invention discloses a preparation method of polyether polyol, which can effectively alleviate the problem that polyether becomes pink through ozone atmosphere protection in a polymerization reaction stage, and further can prepare a clear and transparent polyether polyol product by improving a catalyst and establishing acidic peroxy ligand in-situ oxidation in a catalyst preparation stage.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of polyether polyol synthesis, and particularly relates to a preparation method of polyether polyol. BACKGROUND

[0002] As a key raw material for synthesizing polyurethane, polyether polyol is widely used in the fields of foam plastics, elastomers, coatings, etc. However, the traditional production process of polyether polyol uses alkali metal catalysts (such as KOH), which has the defects of low reaction efficiency, wide molecular weight distribution (PDI > 1.2), and high unsaturation (> 0.05 meq / g). Although double metal cyanide catalysts (DMC, such as Zn3[Co(CN)6]2) can efficiently prepare polyether with high molecular weight, narrow distribution, and low unsaturation, the active center Co 3+ is easily reduced to pink Co 2+ , resulting in the powdering phenomenon of polyether products.

[0003] The improvement direction of the known prior art is mainly to improve the catalytic activity and shorten the reaction induction period, and does not have the core goal of "stabilizing the valence state of cobalt and eliminating powdering". For example, patent CN115003413B introduces peroxide in the catalyst preparation step, mainly to enhance the initial reaction efficiency of the catalyst. In addition, common technical means such as adding auxiliary ligands to improve the stability of the catalyst, or strictly controlling the water content of the raw material system, although they optimize the performance of the catalyst from different angles, their original intention is not directly aimed at "stabilizing the valence state of cobalt ions and completely eliminating product discoloration", which cannot effectively improve the problem of polyether powdering.

[0004] Therefore, it is of great industrial significance to develop a DMC catalyst that can not only eliminate high molecular impurities but also inhibit the powdering phenomenon. SUMMARY

[0005] The purpose of the present application is to provide a preparation method of a high-stability anti-discoloration double metal catalyst (DMC), which can effectively slow down the problem of polyether powdering through ozone atmosphere protection during the polymerization reaction stage, and further establish "in-situ oxidation of acidic peroxide ligand during the catalyst preparation stage" by improving the catalyst, to prepare clear and transparent polyether polyol products.

[0006] To achieve the above application purposes, the present application adopts the following technical solutions:

[0007] A preparation method of polyether polyol, comprising the following steps:

[0008] 1) in the reaction kettle, add initiator and bimetallic catalyst, heat to 90-100℃, stirring until the material is uniformly dispersed, continuously into the reaction kettle containing 1-10 ppm by volume of ozone in nitrogen, remove the water and other volatile impurities in the initiator and catalyst for 1-3h;

[0009] 2) heat to 120-145℃, stop the ozone-containing nitrogen gas with a volume fraction of 1-10ppm, control the system under 0.001MPa to 0.05MPa, add part of the epoxide to induce the reaction;

[0010] 3) then add the remaining epoxide, ring-opening polymerization, get polyether polyol.

[0011] The content of ozone in the present application is its volume fraction.

[0012] In the present application, the pressure is gauge pressure unless otherwise specified.

[0013] Preferably, the initiator is a polyether with a molecular weight greater than 400g / mol.

[0014] Preferably, the amount of initiator added is 1 / 4 to 1 / 2 of the volume of the reaction kettle.

[0015] Preferably, the bimetallic catalyst is a DMC catalyst with a main structure of cobalt zinc cyanide.

[0016] Preferably, the amount of bimetallic catalyst added is 50-200ppm of the mass of the initiator.

[0017] Preferably, in step (1), the water and other volatile impurities in the initiator and catalyst can be removed by a vacuum system, and the system pressure is maintained by continuously introducing ozone-containing nitrogen gas, and the system pressure is 0.001MPa to 0.05MPa;

[0018] Preferably, the system pressure in step 2) before adding part of the epoxide is 0.001MPa to 0.05MPa;

[0019] Preferably, the reaction pressure is maintained at 0.1-0.5Mpa after adding part of the epoxide in step 2).

[0020] Preferably, the mass of the epoxide added in step 2) is 5-30% of the mass of the initiator.

[0021] Preferably, the epoxide is ethylene oxide and / or propylene oxide.

[0022] Preferably, in step 3), according to the prior art, it is generally believed that the induction reaction is successful when the pressure drops to about half of the initial pressure, at which point the epoxide is added to the reaction vessel.

[0023] Preferably, in the step 3), the reaction temperature is 100-180℃, preferably 120-140℃, and the pressure is 0.1-0.6MPa (gauge pressure), preferably 0.1-0.3MPa. The reaction is continued until the pressure no longer decreases, to obtain the polyether polyol product.

[0024] Preferably, the bimetallic catalyst uses an alcohol containing a peroxide bond and a polyether polyol as ligands.

[0025] Preferably, the alcohol containing a peroxide bond is tert-butyl hydroperoxide or tert-butyl hydroperoxide.

[0026] The preparation method of the bimetallic catalyst comprises the following steps:

[0027] A. Adding a zinc salt solution into a cyanide salt solution to obtain a precipitate;

[0028] B. Adding an inorganic acid into the product of step A) to adjust the pH value of the system to an acidic environment of 3.0-5.0, and then adding an organic ligand containing a peroxide bond and a polyether polyol, and stirring to react;

[0029] C. Filtering, washing and drying the product of step B) to obtain the bimetallic catalyst.

[0030] Preferably, in step B), the inorganic acid is added before the organic ligand containing a peroxide bond and the polyether polyol. This specific order is intended to create an acidic environment to facilitate the decomposition of the subsequently added organic ligand containing a peroxide bond to generate free radicals, and to realize the in-situ oxidation of cobalt ions in the catalyst (Co 2+ →Co 3+ ), thereby blocking the reduction path from the source.

[0031] In the above preparation method, the zinc salt in step A) is zinc chloride, zinc sulfate or zinc nitrate; and the cyanide salt is a cyanide of cobalt, preferably potassium cobalt cyanide or sodium cobalt cyanide, preferably potassium cobalt cyanide.

[0032] In the above preparation method, the molar feeding ratio of the zinc salt to the cyanide salt in step A) is 2:1-9:1, preferably 3:1-8:1; the reaction temperature is 20-80℃, and the reaction time is 10min-5h, preferably the reaction temperature is 30-60℃, and the time is 1-2h.

[0033] In the above preparation method, the inorganic acid in step B) is phosphoric acid, hydrochloric acid or sulfuric acid, preferably phosphoric acid; the organic ligand containing a peroxide bond is tert-butyl hydroperoxide or tert-butyl hydroperoxide; and the polyether polyol comprises one or more of polypropylene glycol and polyethylene glycol.

[0034] The preparation method, in step B), the pH value is adjusted to 3.0-5.0, preferably 3.0-4.0;

[0035] Preferably, the amount of the organic ligand containing a peroxide bond accounts for 5%-25% of the total liquid mass in step A), and the polyether polyol accounts for 1%-30% of the total liquid mass in step A); preferably, the amount of the organic ligand containing a peroxide bond accounts for 5%-15% of the total liquid mass in step A), and the polyether polyol accounts for 2%-10% of the total liquid mass in step A);

[0036] Preferably, the molecular weight of the polyether polyol is 400-2000 g / mol;

[0037] Preferably, the reaction time of step B) is 1-2 h, and the reaction temperature is 30-60°C.

[0038] The preparation method, in step C), the double metal catalyst is obtained by washing with a washing liquid containing 0.1-1.0 wt% ammonium persulfate (pH=6.0-7.0) and water in sequence until neutral, and then drying and crushing.

[0039] In the drying process in step C), the temperature is 50-150°C, preferably 80-100°C.

[0040] The catalyst obtained by the above method is a white powder with high catalytic activity, and the polyether product obtained by catalysis is colorless, clear and transparent, and free of high molecular weight tailing.

[0041] The present application has the following beneficial effects:

[0042] 1. The present application creatively proposes a double inhibition synergistic mechanism of "in-situ oxidation of acidic peroxide ligand in the catalyst preparation stage" and "ozone atmosphere protection in the polymerization reaction stage". First, in the catalyst preparation stage, a specific acidic environment is created by adding acid first, and then adding a peroxide ligand to make it decompose to generate ·O2 - , realizing in-situ oxidation of Co 2+ →Co 3+ , and pre-stabilizing the valence state of cobalt. Then, in the catalytic polymerization process, a trace amount of ozone atmosphere is introduced to continuously inhibit the re-reduction of cobalt in the reaction process, thereby completely blocking the reduction path of cobalt from the source and process dimensions, and the obtained polyether product is completely free of pink color.

[0043] 2. The polyether polyol prepared by the present application has a clear and transparent appearance, a narrow molecular weight distribution, and a low unsaturation degree, and is suitable for the synthesis of high-end polyurethane materials.

[0044] 3. The catalyst preparation process of the present application is simple, green and environmentally friendly, and the washing process does not require organic solvents, and there is no risk of antioxidant migration. DETAILED DESCRIPTION

[0045] The application will be further described in connection with the following examples.

[0046] The high molecular impurity in the embodiments of the application refers to a byproduct component produced in the synthesis of the polyether polyol, which has a molecular weight much higher than that of the target polyether polyol main product.

[0047] The content of the high molecular impurity can be determined by gel permeation chromatography. Specifically, the sample is dissolved in tetrahydrofuran, and a GPC instrument equipped with a differential refractometer detector is used for calibration with a polystyrene standard sample. The high molecular weight impurity is defined as the component corresponding to all chromatographic peaks with a retention time earlier than the target polyether main peak in the GPC spectrum, and its content is calculated from the percentage of the peak area of the component in the total peak area.

[0048] Example 1

[0049] 1. Preparation of a bimetallic catalyst:

[0050] 1) 60 g of a 40 wt% K3[Co(CN)6] solution was added dropwise to 150 g of a 15 wt% ZnCl2 solution (Zn:Co = 5:1) at 40°C, and the reaction was performed for 1 h; 2+ :Co 3+ = 5:1), 40°C, reaction 1 h;

[0051] 2) The precipitate of step 1) was added with dilute phosphoric acid to adjust the pH value to 3.5, 20 g of tert-butyl hydroperoxide and 10 g of polypropylene glycol (MW = 1000) were added, and stirring was performed for 1 h;

[0052] 3) The precipitate solution of step 2) was filtered, washed with an aqueous solution containing 0.5 wt% ammonium persulfate and pure water until neutral, the filter cake was dried in a vacuum oven at 80°C for 4 hours, and the white catalyst powder was obtained by crushing, with a yield of 17.8 g.

[0053] 2. Synthesis of a polyether polyol:

[0054] 500 g of polypropylene glycol (MW = 600) was mixed with 0.025 g (50 ppm based on the initiator mass) of the bimetallic catalyst, and the mixture was uniformly dispersed by heating to 100°C under N2 protection. At this temperature, nitrogen gas containing 10 ppm of ozone was continuously introduced into the reaction kettle, and a vacuum system was started to control the system under a slight positive pressure (about 0.02 MPa) to continuously remove water and other volatile impurities for 2 hours.

[0055] After dehydration, the vacuum system was stopped, nitrogen gas containing 10 ppm of ozone was introduced, and the system was controlled under a slight positive pressure of 0.03 MPa. The reaction system was heated to 130°C, and 50 g of propylene oxide was added, and the pressure of the reaction kettle was controlled at 0.4 MPa.

[0056] After the pressure dropped by half, 450 g of propylene oxide was added, and the reaction temperature was controlled at 120-140 °C, and the pressure was controlled at 0.2-0.4 MPa (gauge pressure).

[0057] After the reaction was completed, the monomers were removed by vacuuming to obtain 922 g of clear and transparent polyether polyol product.

[0058] Example 2

[0059] 1. Preparation of bimetallic catalyst:

[0060] 1) 65 g of 35 wt% K3[Co(CN)6] solution was added dropwise to 180 g of 12 wt% ZnSO4 solution (Zn:Co = 6:1) at 45 °C, and the reaction was carried out for 1.5 h; 2+ :Co 3+ = 6:1) at 45 °C for 1.5 h;

[0061] 2) The precipitate from step 1) was added with dilute phosphoric acid to adjust the pH value to 3.8, 25 g of tert-butyl hydroperoxide and 15 g of polyethylene glycol (MW = 800) were added, and stirring was carried out for 1.5 h;

[0062] 3) The precipitate solution from step 2) was filtered, washed with an aqueous solution containing 0.3 wt% ammonium persulfate and pure water until neutral, and the filter cake was dried in a vacuum oven at 80 °C for 4 hours, and then pulverized to obtain 19.5 g of white catalyst powder.

[0063] 2. Synthesis of polyether polyol:

[0064] 500 g of polypropylene glycol (MW = 600) was mixed with 0.05 g (100 ppm based on the mass of the initiator) of bimetallic catalyst, and the temperature was raised to 100 °C under N2 protection and stirring was carried out to disperse uniformly. At this temperature, nitrogen gas containing 5 ppm of ozone was continuously introduced into the reaction kettle, and at the same time, the vacuum system was started, and the system was controlled at a slight positive pressure (about 0.01 MPa) to continuously remove water and other volatile impurities for 2.5 hours.

[0065] After the dehydration was completed, the vacuum system and the nitrogen gas containing 5 ppm of ozone were stopped, and the system was controlled at a slight positive pressure of 0.01 MPa. The reaction system was heated to 130 °C, 50 g of propylene oxide was added, and the pressure of the reaction kettle was controlled at 0.36 MPa.

[0066] After the pressure dropped by half, 450 g of propylene oxide was added, and the reaction temperature was controlled at 120-140 °C, and the pressure was controlled at 0.2-0.4 MPa (gauge pressure).

[0067] After the reaction was completed, the monomers were removed by vacuuming to obtain 932 g of clear and transparent polyether polyol product.

[0068] Example 3

[0069] 1. Preparation of bimetallic catalyst:

[0070] 1) To 200 g of 10 wt% ZnCl2solution, 75 g of 30 wt% K3[Co(CN)6] solution was added dropwise (Zn:Co = 4:1) at 50°C for 2 h; 2+ :Co 3+ = 4:1), 50°C, for 2 h;

[0071] 2) To the precipitate of step 1), dilute phosphoric acid was added to adjust the pH to 3.2, 30 g of t-butyl hydroperoxide and 20 g of polypropylene glycol (MW = 2000) were added, and stirred for 2 h;

[0072] 3) The precipitate solution of step 2) was filtered, washed with a 0.7 wt% ammonium persulfate aqueous solution at pH = 6.2 and pure water until neutral, and the filter cake was dried in a vacuum oven at 80°C for 4 h, and then pulverized to obtain 22 g of white catalyst powder.

[0073] 2. Synthesis of polyether polyol:

[0074] 500 g of polypropylene glycol (MW = 600) was mixed with 0.1 g (200 ppm based on the initiator mass) of bimetallic catalyst, and uniformly dispersed by heating to 100°C under N2protection. At this temperature, nitrogen gas containing 8 ppm ozone was continuously introduced into the reaction kettle, and a vacuum system was turned on to control the system at a slight positive pressure (about 0.04 MPa) to continuously remove water and other volatile impurities for 2.5 h.

[0075] After dehydration, the vacuum system and the nitrogen gas containing 8 ppm ozone were stopped, and the system was controlled at a slight positive pressure of 0.04 MPa. The reaction system was heated to 130°C, and 50 g of propylene oxide was added, and the pressure of the reaction kettle was controlled at 0.41 MPa.

[0076] After the pressure dropped by half, 450 g of propylene oxide was added, and the reaction temperature was controlled at 120-140°C, and the pressure was controlled at 0.2-0.4 MPa (gauge pressure).

[0077] After the reaction was completed, the monomers were removed by vacuum, and 941 g of clear and transparent polyether polyol product was obtained.

[0078] Comparative Example 1

[0079] Potassium cobalt cyanide + t-butyl alcohol + ozone

[0080] Catalyst preparation: same as Example 1, but t-butyl alcohol was used instead of t-butyl hydroperoxide in step 2).

[0081] Polyether polyol: under the same conditions as Example 1, a small amount of flocculent material was present in the obtained polyether polyol product, and the color was pink.

[0082] Comparative Example 2

[0083] Potassium cobalticyanide + t-butyl alcohol + no ozone

[0084] Catalyst preparation: same as Example 1, step

[0085] Polyether polyol: same as Example 1, but no ozone was passed before the reaction, and the resulting polyether polyol product contained a trace amount of flocculent matter and was pink in color.

[0086] Comparative Example 3

[0087] Potassium cobalticyanide + t-butyl alcohol + no ozone

[0088] Catalyst preparation: same as Comparative Example 1.

[0089] Polyether polyol: same as Example 1, but no ozone was passed before the reaction, and the resulting polyether polyol product contained a trace amount of flocculent matter and was pink in color.

[0090] The polyether polyols prepared in Examples 1-3 and Comparative Examples 1-2 were tested for unsaturation according to GB / T 12008.6-2010 Plastics - Polyether polyols - Part 6: Determination of unsaturation. The results are shown in Table 1.

[0091] Table 1 Test Results

[0092]

[0093] As can be seen from the test results of Examples 1, 2, 3 and Comparative Examples 1, 2, 3 in Table 1, the polyether polyols prepared using the bimetallic catalyst synthesized according to the present application are clear and transparent in appearance, and have low unsaturation, PDI and high molecular impurity content under the same conditions.

Claims

1. A method for preparing a polyether polyol, characterized in that, Includes the following steps: 1) Add the initiator and bimetallic catalyst to the reactor, heat to 90-100℃, stir until the material is evenly dispersed, and continuously introduce nitrogen gas containing 1-10 ppm ozone into the reactor to remove moisture and other volatile impurities from the initiator and catalyst for 1-3 hours. 2) Heat to 120-145℃ and add some epoxides to induce the reaction in a nitrogen atmosphere containing 1-10 ppm ozone by volume. 3) Then add the remaining epoxide and perform ring-opening polymerization to obtain polyether polyol.

2. The preparation method according to claim 1, characterized in that, The initiator is a polyether with a molecular weight greater than 400 g / mol; Preferably, the amount of the initiator added is 1 / 4 to 1 / 2 of the reactor volume; Preferably, the bimetallic catalyst is a DMC catalyst with cobalt zinc cyanide as its main structure; Preferably, the amount of the bimetallic catalyst added is 50-200 ppm of the initiator mass; Preferably, in step (1), moisture and other volatile impurities in the initiator and catalyst are removed by a vacuum system, and the system pressure is maintained by continuously introducing nitrogen containing ozone, with the system pressure being 0.001 MPa to 0.05 MPa; Preferably, before adding part of the epoxide in step 2), the system pressure is 0.001 MPa to 0.05 MPa; Preferably, in step 2), after adding a portion of the epoxide, the reaction pressure is maintained at 0.1-0.5 MPa; Preferably, the mass of the epoxide added in step 2) is 5-30% of the mass of the initiator.

3. The preparation method according to claim 1 or 2, characterized in that, The epoxide is ethylene oxide and / or propylene oxide; Preferably, in step 3), the reaction temperature is 100–180°C, more preferably 120–140°C, and the pressure is 0.1–0.6 MPa, more preferably 0.1–0.3 MPa.

4. The preparation method according to any one of claims 1-3, characterized in that, The bimetallic catalyst uses alcohols and polyether polyols containing peroxy bonds as ligands; Preferably, the alcohol containing a peroxy bond is peroxytert-butanol or tert-butyl hydroperoxide.

5. The preparation method according to any one of claims 1-4, characterized in that, The preparation method of the bimetallic catalyst includes the following steps: A. Adding a zinc salt solution to a cyanide salt solution yields a precipitate; B. First, add an inorganic acid to the product of step A) to adjust the pH of the system to an acidic environment of 3.0 to 5.0, and then add an organic ligand containing a peroxide bond and a polyether polyol, and stir the reaction. C. Filter, wash and dry the product from step B) to obtain the bimetallic catalyst; Preferably, in step B), the inorganic acid is added before the organic ligand containing the peroxide bond and the polyether polyol.

6. The preparation method according to claim 5, characterized in that, The zinc salt mentioned in step A) is zinc chloride, zinc sulfate, or zinc nitrate; the cyanide salt is cobalt cyanide, preferably potassium cobalt cyanide or sodium cobalt cyanide, with potassium cobalt cyanide being the most preferred. Preferably, in step A), the molar ratio of zinc salt to cyanide salt is 2:1 to 9:1, more preferably 3:1 to 8:1; the reaction temperature is 20 to 80°C and the reaction time is 10 min to 5 h, more preferably 30 to 60°C and 1 to 2 h. Preferably, the inorganic acid in step B) is phosphoric acid, hydrochloric acid, or sulfuric acid, with phosphoric acid being preferred; the organic ligand containing a peroxide bond is tert-butanol peroxide or tert-butyl hydroperoxide; and the polyether polyol comprises one or more of polypropylene glycol and polyethylene glycol. Preferably, in step B), the pH value is adjusted to 3.0–5.0, more preferably 3.0–4.0; Preferably, the amount of organic ligands containing peroxide bonds is 5% to 25% of the total liquid mass in step A), and the amount of polyether polyol is 1% to 30% of the total liquid mass in step A); more preferably, the amount of organic ligands containing peroxide bonds is 5% to 15% of the total liquid mass in step A), and the amount of polyether polyol is 2% to 10% of the total liquid mass in step A). Preferably, the polyether polyol has a molecular weight of 400-2000 g / mol.

7. The preparation method according to claim 5, characterized in that, The reaction time for step B) is 1-2 hours; the reaction temperature is 30-60℃. In the above preparation method, step C) involves washing the bimetallic catalyst successively with a washing solution containing 0.1-1.0 wt% ammonium persulfate and water until neutral, followed by drying and pulverization. The temperature during the drying process described in step C) is 50–150°C, preferably 80–100°C.

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