Preparation method of alkane diol random polyether

Abstract

The invention belongs to the technical field of organic synthesis, and discloses a preparation method of alkane diol random polyether. The preparation method comprises the following steps: adding an initiator alkane diol, a main catalyst and a cocatalyst into a reaction kettle, adding ethylene oxide and epoxypropane, controlling the feeding time to be 4-8 hours, controlling the feeding rate of the ethylene oxide to be linearly increased to 40-65 g / 10 min from 10-30 g / 10 min, and controlling the feeding rate of the epoxypropane to be linearly reduced to 10-30 g / 10 min from 40-65 g / 10 min. According to the preparation method provided by the invention, ethylene oxide and propylene oxide are taken as comonomers, and the random copolyether with uniformly distributed molecular chain sequences is prepared in a compound base catalysis system through a special feeding mode. The random copolyether is high in random degree, low in surface tension, high in emulsion stability and narrow in molecular weight distribution; and the preparation method can follow the post-treatment method of the traditional alkali catalysis process, and has the advantages of simple process and low cost.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis technology, specifically relating to a method for preparing random polyethers of alkane diols. Background Technology

[0002] Propylene glycol random polyether, as a high-performance polymeric surfactant, is widely used in various industrial fields such as chemical fibers, metal processing, and detergents. This is mainly due to the excellent emulsifying ability, low toxicity, low foaming properties, and good dispersibility brought about by the random structure of its ethylene oxide (EO) and propylene oxide (PO). Specifically, in the chemical fiber and textile industry, it is used as a smoothing agent and leveling agent in oils; in metal processing, it is a key component in the formulation of cutting coolants, playing a role in emulsification and lubrication; in the detergent field, its low-foaming characteristics make it very suitable for the formulation of industrial cleaning agents and defoamers.

[0003] In traditional alkaline catalytic processes (such as those using KOH or NaOH as catalysts) for the preparation of EO / PO copolyethers, it is difficult to produce products with higher randomness because the reactivity of ethylene oxide (EO) is much higher than that of propylene oxide (PO) (reactivity ratio rEO>rPO). To obtain random copolymers with a more uniform sequence distribution, the art typically requires expensive, water- and initiator-sensitive bimetallic cyanide complex catalysts (DMC). DMC catalyst processes are complex, have high requirements for the EO / PO ratio, and post-treatment cannot utilize mature alkaline catalytic neutralization and decolorization processes, increasing production costs and operational complexity.

[0004] The higher the randomness of propylene glycol random polyethers, the stronger their emulsifying stability. Because the hydrophilic EO units and lipophilic PO units in their molecular chains are randomly distributed, when adsorbed at the oil-water interface, the entire molecular chain must adopt multiple conformations to simultaneously satisfy the requirement that the hydrophilic groups extend into the aqueous phase and the lipophilic groups extend into the oil phase. This "multi-point anchoring" method allows the molecular chains to spread more fully at the interface, resulting in a higher interfacial adsorption density and a denser and stronger interfacial film. This robust interfacial film effectively prevents droplets from coalescing upon collision, thus making the emulsion more stable. However, as an emulsifier, the emulsifying performance of current propylene glycol random polyethers still needs further improvement.

[0005] Therefore, developing a method for preparing highly randomized EO / PO copolyethers based on a traditional alkaline catalytic system through process innovation has significant industrial application value. Summary of the Invention

[0006] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a method for preparing alkane diol random polyethers. The alkane diol random polyethers prepared by the present invention have high randomness, low surface tension, strong emulsification stability, and narrow molecular weight distribution; moreover, the preparation method provided by the present invention can utilize the post-processing of traditional alkaline catalytic processes, and the process is simple and low-cost.

[0007] This invention provides a method for preparing random polyethers of alkane diols.

[0008] Specifically, a method for preparing an alkane diol random polyether includes the following steps: (1) Add the initiator alkane diol, main catalyst and co-catalyst to the reaction vessel, heat, and dehydrate and activate; (2) After evacuating the reactor, heat it to the reaction temperature, add ethylene oxide and propylene oxide, and control the feeding time to 4-8 hours. From the start of feeding to the end of feeding, control the feeding rate of ethylene oxide to increase linearly from 10-30 g / 10 min to 40-65 g / 10 min, and control the feeding rate of propylene oxide to decrease linearly from 40-65 g / 10 min to 10-30 g / 10 min. (3) After feeding is completed, the material is kept warm and matured, and then post-processed to obtain alkane diol random polyether; The main catalyst is an alkali metal hydroxide, and the co-catalyst includes polyethylene glycol; the amount of the main catalyst is 0.05%-0.55% of the total mass of the initiator alkane diol, the ethylene oxide and the propylene oxide, and the amount of the co-catalyst is 3%-30% of the mass of the main catalyst.

[0009] In some embodiments of the present invention, the initiator alkane diol in step (1) is a C2-C3 alkane diol, such as ethylene glycol, 1,2-propanediol and 1,3-propanediol.

[0010] In some embodiments of the present invention, the heating process in step (1) is: stirring and heating to 70-90°C.

[0011] In some embodiments of the present invention, the alkali metal hydroxide includes KOH and NaOH.

[0012] In some embodiments of the present invention, the amount of the main catalyst is 0.1%-0.5% of the total mass of the initiator alkane diol, the ethylene oxide and the propylene oxide.

[0013] In some embodiments of the present invention, the amount of the co-catalyst is 4%-25% of the mass of the main catalyst.

[0014] In some embodiments of the present invention, the co-catalyst comprises polyethylene glycol 400.

[0015] In some embodiments of the present invention, the reaction temperature in step (2) is 95-120°C; preferably, the reaction temperature is 100-115°C.

[0016] In some embodiments of the present invention, the molar ratio of ethylene oxide to propylene oxide in step (2) is 1:(0.3-2). Preferably, the molar ratio of ethylene oxide to propylene oxide in step (2) is 1:(0.51-1.76).

[0017] In some embodiments of the present invention, when propylene glycol is used as the initiator, the feeding time in step (2) is controlled to be 5-7 hours. From the start of feeding to the end of feeding, the EO feeding rate linearly increases from 20-30 g / 10 min to 50-65 g / 10 min, and the PO feeding rate linearly decreases from 50-65 g / 10 min to 20-30 g / 10 min. Preferably, in step (2), the feeding time is controlled to be 5-7 hours. From the start of feeding to the end of feeding, the EO feeding rate linearly increases from 23-28 g / 10 min to 55-60 g / 10 min, and the PO feeding rate linearly decreases from 55-60 g / 10 min to 23-28 g / 10 min.

[0018] In some embodiments of the present invention, the heat preservation and curing process in step (3) is to keep the reactor at 95-120°C for 1-3 hours until the pressure inside the reactor no longer decreases; preferably, the heat preservation and curing process in step (3) is to keep the reactor at 100-115°C for 1-3 hours until the pressure inside the reactor no longer decreases.

[0019] In some embodiments of the present invention, the post-treatment in step (3) includes neutralization, decolorization, dehydration, and filtration. The post-treatment process is the same as that of conventional alkaline catalytic post-treatment and has no special features. Specifically, it can be carried out in the following steps: heat the polyether to 70-80°C, add 2%-15% (relative to the mass of the polyether) of deionized water and stir for 20-40 min; then add phosphoric acid for neutralization (molar ratio with alkaline catalysis 1:1) and stir for 20-40 min; then add 0.3%-1% (relative to the mass of the polyether) of magnesium silicate adsorbent and stir for 20-40 min; finally, heat and dehydrate under reduced pressure until the temperature reaches 90-110°C and the vacuum reaches -0.098 MPa, keep warm for 0.5-2 h, and then cool down to 55-65°C for filtration.

[0020] This invention uses alkali metal hydroxide as the main catalyst and polyethylene glycol 400 as the co-catalyst, employing a gradient-rate feeding method to add ethylene oxide (EO) and propylene oxide (PO) to prepare alkane diol random polyethers. The co-catalyst PEG-400, acting as a phase transfer catalyst, complexes with K+, improving the catalyst's solubility and the dispersion of active centers in the reaction system, making the chain growth reaction more synchronous and creating conditions for a bulk homogeneous reaction. While traditional uniform feeding can maintain a constant total pressure, it cannot solve the fluctuations in liquid phase composition caused by the difference in EO / PO reaction rates. The gradient-rate feeding method of this invention, by pre-compensating for the difference in reaction rates, maintains the concentration ratio of the two monomers in the liquid phase at an ideal state, thereby achieving true random copolymerization. Specifically, this invention employs dynamic gradient feeding, with the instantaneous feeding rates of EO and PO independently adjusted by a control system. Throughout the feeding period, the instantaneous feeding rate of ethylene oxide (EO) increases linearly from slow to fast over time; correspondingly, the instantaneous feeding rate of propylene oxide (PO) decreases linearly from fast to slow over time. This is intended to compensate for the faster consumption of EO, so that the concentration ratio of the two monomers in the reaction system is always maintained at the optimal level consistent with the composition of the target product.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The preparation method provided by the present invention uses ethylene oxide (EO) and propylene oxide (PO) as comonomers to prepare a random copolymer ether with a uniform molecular chain sequence distribution in a compound alkali catalytic system through a special feeding method. The random copolymer ether has high randomness, low surface tension, strong emulsion stability, and narrow molecular weight distribution; moreover, the preparation method can adopt the post-processing method of traditional alkali catalytic process, and the process is simple and low cost.

[0022] (2) The preparation method provided by this invention can continue to use traditional alkaline catalytic devices and retain the post-processing of traditional alkaline catalytic processes, without the need for redesigning and improving equipment or optimizing the post-processing. This invention achieves a product structure with high randomness that was originally required by DMC catalysts through the combined use of the main catalyst alkali metal hydroxide and the co-catalyst polyethylene glycol 400 and clever process control. Moreover, this method is low in cost and has a simple post-processing; the prepared copolyether has a narrower molecular weight distribution and better emulsification and wetting properties. Detailed Implementation

[0023] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

[0024] Unless otherwise specified, the raw materials, reagents or apparatus used in the following examples and comparative examples are available from conventional commercial sources or can be obtained by existing known methods.

[0025] Example 1 A method for preparing a propylene glycol random polyether includes the following steps: (1) Catalyst compounding and activation: 76g of propylene glycol as the initiator, 6.15g (0.2%) of potassium hydroxide as the main catalyst, and 1.54g (25%) of PEG-400 as the co-catalyst were added to the reactor, stirred and heated to 85°C, and dehydrated and activated under vacuum for 1 hour; (2) Dynamic gradient feed reaction: After activation, the reactor is evacuated and then heated to 110°C. Ethylene oxide and propylene oxide are introduced at the same time to carry out the reaction. The feed time is controlled at 6h. The feed rate of ethylene oxide (EO) is linearly increased from 25g / 10min to 58g / 10min (total EO 1500g), and the feed rate of propylene oxide (PO) is linearly decreased from 58g / 10min to 25g / 10min (total PO 1500g). The reaction pressure does not exceed 0.35MPa. (3) Curing and post-treatment: After the monomers EO and PO are added, continue to cure at 100℃ for 2 hours until the pressure in the reactor no longer decreases, and then end the reaction. Follow the conventional alkaline catalytic post-treatment process: heat the polyether to 75℃, add 10% (relative to the mass of polyether) of deionized water and stir for 30 min; then add phosphoric acid to neutralize (molar ratio of 1:1 with the alkaline catalytic amount) and stir for 30 min; then add 0.8% (relative to the mass of polyether) of magnesium silicate adsorbent and stir for 30 min. Finally, dehydrate under reduced pressure at 100℃, maintain the vacuum at -0.098 MPa for 1 h, then cool to 60℃ and filter to obtain EO / PO random copolymer.

[0026] Example 2 A method for preparing a propylene glycol random polyether includes the following steps: (1) Catalyst compounding and activation: 76g of propylene glycol as the initiator, 3.08g (0.1%) of potassium hydroxide as the main catalyst, and 0.77g (25%) of PEG-400 as the co-catalyst were added to the reactor, stirred and heated to 85°C, and dehydrated and activated under vacuum for 1 hour; (2) Dynamic gradient feed reaction: After activation, the reactor is evacuated and then heated to 110°C. Ethylene oxide and propylene oxide are introduced at the same time to carry out the reaction. The feed time is controlled at 6h. The feed rate of ethylene oxide (EO) is linearly increased from 25g / 10min to 58g / 10min (total EO 1500g), and the feed rate of propylene oxide (PO) is linearly decreased from 58g / 10min to 25g / 10min (total PO 1500g). The reaction pressure does not exceed 0.35MPa. (3) Curing and post-treatment: After the monomers EO and PO are added, continue to cure at 100℃ for 2 hours until the pressure in the reactor no longer decreases, and then end the reaction. Follow the conventional alkaline catalytic post-treatment process: heat the polyether to 75℃, add 10% (relative to the mass of polyether) of deionized water and stir for 30 min; then add phosphoric acid to neutralize (molar ratio of 1:1 with the alkaline catalytic amount) and stir for 30 min; then add 0.8% (relative to the mass of polyether) of magnesium silicate adsorbent and stir for 30 min. Finally, dehydrate under reduced pressure at 100℃, maintain the vacuum at -0.098 MPa for 1 h, then cool to 60℃ and filter to obtain EO / PO random copolymer.

[0027] Example 3 A method for preparing a propylene glycol random polyether includes the following steps: (1) Catalyst compounding and activation: 76g of propylene glycol as the initiator, 6.15g (0.2%) of potassium hydroxide as the main catalyst, and 0.25g (4%) of PEG-400 as the co-catalyst were added to the reactor, stirred and heated to 85°C, and dehydrated and activated under vacuum for 1 hour; (2) Dynamic gradient feed reaction: After activation, the reactor is evacuated and then heated to 110°C. Ethylene oxide and propylene oxide are introduced at the same time to carry out the reaction. The feed time is controlled at 6h. The feed rate of ethylene oxide (EO) is linearly increased from 25g / 10min to 58g / 10min (total EO 1500g), and the feed rate of propylene oxide (PO) is linearly decreased from 58g / 10min to 25g / 10min (total PO 1500g). The reaction pressure does not exceed 0.35MPa. (3) Curing and post-treatment: After the monomers EO and PO are added, continue to cure at 100℃ for 2 hours until the pressure in the reactor no longer decreases, and then end the reaction. Follow the conventional alkaline catalytic post-treatment process: heat the polyether to 75℃, add 10% (relative to the mass of polyether) of deionized water and stir for 30 min; then add phosphoric acid to neutralize (molar ratio of 1:1 with the alkaline catalytic amount) and stir for 30 min; then add 0.8% (relative to the mass of polyether) of magnesium silicate adsorbent and stir for 30 min. Finally, dehydrate under reduced pressure at 100℃, maintain the vacuum at -0.098 MPa for 1 h, then cool to 60℃ and filter to obtain EO / PO random copolymer.

[0028] Example 4 A method for preparing a propylene glycol random polyether includes the following steps: (1) Catalyst compounding and activation: 76g of propylene glycol as the initiator, 6.15g (0.2%) of potassium hydroxide as the main catalyst, and 1.6g (26%) of PEG-400 as the co-catalyst were added to the reactor, stirred and heated to 85°C, and dehydrated and activated under vacuum for 1 hour; (2) Dynamic gradient feed reaction: After activation, the reactor is evacuated and then heated to 110°C. Ethylene oxide and propylene oxide are introduced at the same time to carry out the reaction. The feed time is controlled at 6h. The feed rate of ethylene oxide (EO) is linearly increased from 25g / 10min to 58g / 10min (total EO 1500g), and the feed rate of propylene oxide (PO) is linearly decreased from 58g / 10min to 25g / 10min (total PO 1500g). The reaction pressure does not exceed 0.35MPa. (3) Curing and post-treatment: After the monomers EO and PO are added, continue to cure at 100℃ for 2 hours until the pressure in the reactor no longer decreases, and then end the reaction. Follow the conventional alkaline catalytic post-treatment process: heat the polyether to 75℃, add 10% (relative to the mass of polyether) of deionized water and stir for 30 min; then add phosphoric acid to neutralize (molar ratio of 1:1 with the alkaline catalytic amount) and stir for 30 min; then add 0.8% (relative to the mass of polyether) of magnesium silicate adsorbent and stir for 30 min. Finally, dehydrate under reduced pressure at 100℃, maintain the vacuum at -0.098 MPa for 1 h, then cool to 60℃ and filter to obtain EO / PO random copolymer.

[0029] Example 5 A method for preparing ethylene glycol random polyether includes the following steps: (1) Catalyst compounding and activation: 62g of initiator ethylene glycol, 10.3g (0.5%) of main catalyst sodium hydroxide and 0.515g (5%) of co-catalyst PEG-400 were added to the reactor, stirred and heated to 75°C, and dehydrated and activated under vacuum for 1 hour; (2) Dynamic gradient feed reaction: After activation, the reactor is evacuated and then heated to 100°C. Ethylene oxide and propylene oxide are introduced at the same time to carry out the reaction. The feed time is controlled at 5h. The feed rate of ethylene oxide (EO) is linearly increased from 20g / 10min to 60g / 10min (total EO 1200g), and the feed rate of propylene oxide (PO) is linearly decreased from 43g / 10min to 10g / 10min (total PO 800g). The reaction pressure does not exceed 0.35MPa. (3) Curing and post-treatment: After the monomers EO and PO are added, continue to cure at 100℃ for 2 hours until the pressure in the reactor no longer decreases, and then end the reaction. Follow the conventional alkaline catalytic post-treatment process: heat the polyether to 75℃, add 10% (relative to the mass of polyether) of deionized water and stir for 30 min; then add phosphoric acid to neutralize (molar ratio of 1:1 with the alkaline catalytic amount) and stir for 30 min; then add 0.8% (relative to the mass of polyether) of magnesium silicate adsorbent and stir for 30 min. Finally, dehydrate under reduced pressure at 100℃, maintain the vacuum at -0.098 MPa for 1 h, then cool to 60℃ and filter to obtain EO / PO random copolymer.

[0030] Example 6 A method for preparing ethylene glycol random polyether includes the following steps: (1) Catalyst compounding and activation: 62g of initiator ethylene glycol, 6.2g (0.3%) of main catalyst sodium hydroxide and 0.62g (10%) of co-catalyst PEG-400 were added to the reactor, stirred and heated to 75°C, and dehydrated and activated under vacuum for 1 hour; (2) Dynamic gradient feed reaction: After activation, the reactor is evacuated and then heated to 100°C. Ethylene oxide and propylene oxide are introduced at the same time to carry out the reaction. The feed time is controlled at 5h. The feed rate of ethylene oxide (EO) is linearly increased from 20g / 10min to 60g / 10min (total EO 1200g), and the feed rate of propylene oxide (PO) is linearly decreased from 43g / 10min to 10g / 10min (total PO 800g). The reaction pressure does not exceed 0.35MPa. (3) Curing and post-treatment: After the monomers EO and PO are added, continue to cure at 100℃ for 2 hours until the pressure in the reactor no longer decreases, and then end the reaction. Follow the conventional alkaline catalytic post-treatment process: heat the polyether to 75℃, add 10% (relative to the mass of polyether) of deionized water and stir for 30 min; then add phosphoric acid to neutralize (molar ratio of 1:1 with the alkaline catalytic amount) and stir for 30 min; then add 0.8% (relative to the mass of polyether) of magnesium silicate adsorbent and stir for 30 min. Finally, dehydrate under reduced pressure at 100℃, maintain the vacuum at -0.098 MPa for 1 h, then cool to 60℃ and filter to obtain EO / PO random copolymer.

[0031] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that EO and PO were premixed in a feed tank and added to the reactor at a constant rate, with the feeding time controlled at 6 hours. Other conditions were the same as in Example 1.

[0032] Comparative Example 2 The difference between Comparative Example 2 and Example 2 is that 3.85g of catalyst KOH was added, but no co-catalyst PEG-400 was added. All other conditions were the same as in Example 2.

[0033] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that EO and PO were added to the reactor at a rate of 41.5 g / 10 min, while other conditions were the same as in Example 1.

[0034] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that before introducing ethylene oxide and propylene oxide, the temperature is first raised to 90°C (i.e., the reaction temperature is 90°C), while other conditions are the same as in Example 1.

[0035] Comparative Example 5 The difference between Comparative Example 5 and Example 1 is that before introducing ethylene oxide and propylene oxide, the temperature is first raised to 130°C (i.e., the reaction temperature is 130°C), while other conditions are the same as in Example 1.

[0036] Comparative Example 6 The difference between Comparative Example 6 and the Example is that the amount of KOH as the main catalyst is 18.46 g (0.6%), the amount of PEG-400 is 4.62 g (25%), and the other conditions are the same as in Example 1.

[0037] Product performance testing The polyether products prepared in the above examples and comparative examples were subjected to performance tests, as detailed below: (1) Stability test: Mix the product with white oil (or liquid paraffin) and water in a certain ratio (4:4:92), emulsify by high-speed shearing (8000 rpm, 3 min), and then place it in a graduated cylinder. Measurement index: Record the time required for the volume of the aqueous phase separated from the emulsion to reach 10%. The longer the time, the better the emulsion stability.

[0038] (2) Surface tension (mN / m): Measured in accordance with GB / T 38722-2020.

[0039] (3) Color (Pt-Co): Determined according to GB / T 9282.1-2008.

[0040] (4) Distribution coefficient (PDI): Determined in accordance with GB / T 21863-2008.

[0041] (5) Hydroxyl value (mgKOH / g): determined according to GB / T 7383-2007.

[0042] Table 1

[0043] As shown in Table 1, the alkane diol random polyether prepared by this invention has a narrow molecular weight distribution, high randomness, low surface tension, and strong emulsification stability, which is significantly better than that of the comparative example. A comparison of Examples 1 and 4 shows that when the amount of the co-catalyst PEG exceeds 25%, the emulsification stability of the product decreases, indicating that excessive co-catalyst affects the product's distribution coefficient, thus reducing emulsification stability. Comparative Example 2 and Example 2 show that, under the same conditions, the addition of the co-catalyst increases the product's emulsification stability and reduces the molecular distribution coefficient.

[0044] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for preparing an alkane diol random polyether, characterized in that, Includes the following steps: (1) Add the initiator alkane diol, main catalyst and co-catalyst to the reaction vessel, heat, and dehydrate and activate; (2) After evacuating the reactor, heat it to the reaction temperature, add ethylene oxide and propylene oxide, and control the feeding time to 4-8 hours. From the start of feeding to the end of feeding, control the feeding rate of ethylene oxide to increase linearly from 10-30 g / 10 min to 40-65 g / 10 min, and control the feeding rate of propylene oxide to decrease linearly from 40-65 g / 10 min to 10-30 g / 10 min. (3) After feeding is completed, the material is kept warm and matured, and then post-processed to obtain alkane diol random polyether; The main catalyst is an alkali metal hydroxide, and the co-catalyst includes polyethylene glycol; the amount of the main catalyst is 0.05%-0.55% of the total mass of the initiator alkane diol, the ethylene oxide and the propylene oxide, and the amount of the co-catalyst is 3%-30% of the mass of the main catalyst.

2. The preparation method according to claim 1, characterized in that, The alkali metal hydroxides include KOH and / or NaOH.

3. The preparation method according to claim 1 or 2, characterized in that, The amount of the main catalyst is 0.1%-0.5% of the total mass of the initiator alkane diol, the ethylene oxide, and the propylene oxide.

4. The preparation method according to claim 3, characterized in that, The amount of the co-catalyst is 4%-25% of the mass of the main catalyst.

5. The preparation method according to claim 4, characterized in that, The co-catalyst includes polyethylene glycol 400.

6. The preparation method according to claim 1, characterized in that, The reaction temperature in step (2) is 95-120℃.

7. The preparation method according to claim 1, characterized in that, The molar ratio of ethylene oxide to propylene oxide in step (2) is 1:(0.3-2).

8. The preparation method according to any one of claims 1, 2, 4, and 5, characterized in that, In step (2), the feeding time is controlled to be 5-7 hours. From the start of feeding to the end of feeding, the EO feeding rate increases linearly from 23-28g / 10min to 55-60g / 10min, and the PO feeding rate decreases linearly from 55-60g / 10min to 23-28g / 10min.

9. The preparation method according to claim 1, characterized in that, The heat preservation and curing process described in step (3) is to keep the temperature at 95-120℃ for 1-3 hours until the pressure inside the reactor no longer decreases.

10. The preparation method according to claim 1, characterized in that, The post-processing described in step (3) includes neutralization, decolorization, dehydration, and filtration.

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