A polyester polyol production apparatus

Abstract

The utility model provides a kind of polyester polyol production device, it is essentially a one-pot multi-tower type technical scheme, the reaction kettle of prior art is reformed to single esterification tower, at least two levels of esterification tower of introduction series connection, specific including reaction kettle, at least two levels of esterification tower and vacuum unit, each level esterification tower is set up feed inlet, gas phase discharge port and tower bottom liquid phase outlet, the tower bottom liquid phase outlet of former stage esterification tower is connected with the feed inlet of rear stage esterification tower, gas phase discharge port is connected with the feed inlet of first stage esterification tower, the tower bottom liquid phase outlet of last stage esterification tower is connected with reaction kettle.One-pot multi-tower type technical scheme, both shorten the total time of production, and can effectively remove polyether, acetal, phenolic byproduct, effectively improve the product quality stability of polyester polyol.

Description

Technical Field

[0001] This utility model belongs to the field of polymer compound technology, and relates to polyester polyols, and more particularly to a polyester polyol production apparatus. Background Technology

[0002] Currently, the industrial production of polyester polyols mainly uses a batch process, which involves two stages. Batch reaction equipment includes... Figure 1 As shown, in the first stage, polyol and diacid are esterified in a reactor. In the second stage, under vacuum conditions, polycondensation is carried out to form a low-acid-value polyester polyol. The gaseous material in the reactor enters the esterification tower, which separates the water, by-products and reaction liquid formed by the esterification reaction. The water and some by-products at the top of the esterification tower enter the reflux tank through the condenser. Some by-products and reaction liquid are returned to the reactor to continue the reaction. When the acid value, hydroxyl value and moisture content of the product in the reactor reach the target set value, the reaction is stopped and the product is discharged.

[0003] Currently, polyester polyols prepared by the batch method have the problem of unstable product quality. The instability is mainly reflected in the following aspects: 1) The reaction rate is slow and the total production time is long. The reaction is carried out at high temperature for a long time, which leads to high color of polyester polyol and large fluctuations in PDI within and between batches; 2) Byproducts such as polyether, acetal and phenol are not completely removed, which leads to the polyurethane raw material B (containing isocyanate component) prepared from polyester polyol as raw material having a white appearance, short shelf life and high requirements for storage conditions.

[0004] In conclusion, a new type of polyester polyol production device needs to be developed. Utility Model Content

[0005] To address the shortcomings of existing technologies, this utility model provides a polyester polyol production device, which is essentially a one-reactor-multiple-tower technology solution. It modifies the existing technology by configuring a single esterification tower in the reactor and introduces at least two esterification towers in series. This not only shortens the total production time but also effectively removes byproducts such as polyether, acetal, and phenols, thereby effectively improving the product quality stability of polyester polyols.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] The purpose of this utility model is to provide a polyester polyol production apparatus, including a reaction vessel, at least two esterification towers connected in series, and a vacuum unit;

[0008] Each esterification tower has a feed inlet, a vapor outlet, and a bottom liquid outlet. The bottom liquid outlet of the previous esterification tower is connected to the feed inlet of the next esterification tower. Each vapor outlet is used to discharge water and / or byproducts.

[0009] The reactor is provided with at least a feed inlet, a gas outlet, and a return reaction liquid inlet; the gas outlet is connected to the feed inlet of the first-stage esterification tower, and the return reaction liquid inlet is connected to the bottom liquid outlet of the last-stage esterification tower.

[0010] The reactor is connected to the vacuum unit.

[0011] As an optional technical solution of this utility model, the polyester polyol production device includes 2 to 6 esterification towers connected in series.

[0012] As an optional technical solution of this utility model, the gas phase outlet of the reactor is connected to the inlet of the first-stage esterification tower through a first pipeline; the gas phase outlet of the reactor is connected to the vacuum unit through a second pipeline, which passes through a condenser and a reflux tank in sequence, and a vacuum control valve is installed on the second pipeline.

[0013] As an optional technical solution of this utility model, the reactor is provided with a first gas phase outlet and a second gas phase outlet. The first gas phase outlet is connected to the feed inlet of the first-stage esterification tower. The second gas phase outlet is connected to the vacuum unit after passing through a condenser and a reflux tank in sequence. A vacuum control valve is provided on the connecting pipeline between the second gas phase outlet and the condenser.

[0014] As an optional technical solution of this utility model, the gas phase discharge outlets of each esterification tower are connected to a condenser and a reflux tank in sequence, respectively, to condense and recover the water and / or by-products discharged from each esterification tower.

[0015] As an optional technical solution of this utility model, the gas phase outlet of the last esterification tower is connected to the first condenser and the first reflux tank in sequence, and the gas phase outlets of the remaining esterification towers are connected to the second condenser and the second reflux tank in sequence after the corresponding pipelines are combined.

[0016] As an optional technical solution of this utility model, the gas phase outlet of the reactor is connected to the vacuum unit through a second pipeline, which passes through a second condenser and a second reflux tank in sequence.

[0017] As an optional technical solution of this utility model, the second gas phase outlet is connected to the vacuum unit after passing through the second condenser and the second reflux liquid tank in sequence.

[0018] As an optional technical solution of this utility model, a protective condenser is provided between the reflux tank and the vacuum unit, and an exhaust port with an exhaust valve is added to the outlet of the protective condenser.

[0019] As an optional technical solution of this utility model, an acid value monitor and / or a hydroxyl value monitor are installed inside the reaction vessel.

[0020] As an optional technical solution of this utility model, a stirrer is provided inside the reaction vessel.

[0021] As an optional technical solution of this utility model, a reaction liquid control valve is provided on the pipeline corresponding to the return reaction liquid inlet.

[0022] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0023] This invention provides a polyester polyol production device, which is essentially a one-reactor-multiple-tower technical solution. It modifies the existing technology of configuring a single esterification tower in the reactor by introducing at least two esterification towers in series. This not only shortens the total production time but also effectively removes by-products such as polyether, acetal, and phenol, resulting in a polyester polyol with good quality stability. When applied to polyurethane raw material B, material B remains clear and transparent and has a long shelf life. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of a polyester polyol production apparatus in the prior art described in the background section;

[0025] Figure 2 This is a schematic diagram of the polyester polyol production apparatus described in Embodiment 1 of this utility model;

[0026] Figure 3 This is a schematic diagram of the polyester polyol production apparatus described in Embodiment 2 of this utility model;

[0027] Among them, 1-reaction vessel; 2-first-stage esterification tower; 3-second-stage esterification tower; 4-third-stage esterification tower; 5-first condenser; 6-second condenser; 7-first reflux tank; 8-second reflux tank; 9-protective condenser; 10-vacuum unit; 11-vacuum control valve; 12-reaction liquid control valve; 13-exhaust valve; 14-vent valve; 15-pump; 16-fourth-stage esterification tower. Detailed Implementation

[0028] To make the technical solution, objectives, and advantages of this utility model clearer, the present utility model will be further described in detail below through specific embodiments and in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present utility model.

[0029] In the description of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0030] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. In the fields of electricity and communication, they can refer to a wired connection or a wireless connection. For those skilled in the art, the specific meaning of the above terms in this utility model can be understood according to the specific circumstances.

[0031] This invention provides a polyester polyol production apparatus, including a reactor, at least two esterification towers connected in series, and a vacuum unit. The esterification towers are conventional separation towers, such as sieve plate towers. Each esterification tower has a feed inlet, a gas phase outlet, and a bottom liquid phase outlet. The bottom liquid phase outlet of the preceding esterification tower is connected to the feed inlet of the following esterification tower. Each gas phase outlet is used to discharge water and / or byproducts. Preferably, the feed inlet of each esterification tower is located in the middle or lower part of the esterification tower, the gas phase outlet is located in the upper or top part of the esterification tower, and the bottom liquid phase outlet is preferably located at the bottom or lower side of the tower. The reactor is equipped with at least a feed inlet, a gas phase outlet, and a return reaction liquid inlet. The gas phase outlet is connected to the feed inlet of the first-stage esterification tower, and the return reaction liquid inlet is connected to the bottom liquid outlet of the last-stage esterification tower. The feed inlet is used to input reactants and / or output reaction products. A separate outlet for outputting reaction products may also be provided. The gas phase outlet is located at the top or upper part of the reactor, and the return reaction liquid inlet is located at the upper or lower part of the reactor. The reactor is connected to a vacuum unit, which is a conventional vacuum supply device capable of providing a vacuum degree of -0.1 to 0 MPa within the reactor.

[0032] This invention develops a multi-tower single-reactor technology solution, which modifies the existing single esterification tower configuration in the reactor by introducing at least two esterification towers connected in series. This not only shortens the total production time but also effectively removes byproducts such as polyether, acetal, and phenol, thereby significantly improving the product quality stability of polyester polyols.

[0033] In some alternative technical solutions, the polyester polyol production unit includes 2 to 6 esterification towers connected in series, such as 2, 3, 4, 5, or 6 stages. Six stages or less are sufficient to meet the production needs of various polyester polyols. More than 6 stages are also applicable, but this will increase capital investment.

[0034] In some alternative technical solutions, the gas phase outlet of the reactor is connected to the inlet of the first-stage esterification tower via a first pipeline. The gas phase outlet of the reactor is connected to the vacuum unit via a second pipeline, which passes sequentially through a condenser and a reflux tank. A vacuum control valve is installed on the second pipeline. Specifically, the first and second pipelines share a single gas phase outlet, i.e., the two pipelines are connected in parallel, and the pipeline connected to the vacuum unit is individually controlled by a vacuum control valve. Of course, a control valve can be installed on the first pipeline as needed.

[0035] In some alternative technical solutions, the reactor is provided with a gas phase outlet connected to the first-stage esterification tower and a gas phase outlet connected to the vacuum unit. That is, the reactor is provided with a first gas phase outlet and a second gas phase outlet. The first gas phase outlet is connected to the inlet of the first-stage esterification tower, and the second gas phase outlet is connected to the vacuum unit after passing through a condenser and a reflux tank in sequence. A vacuum control valve is provided on the connecting pipeline between the second gas phase outlet and the condenser.

[0036] In some optional technical solutions, the gas phase discharge outlets of each esterification tower are connected sequentially to a condenser and a reflux tank to condense and recover the water and / or byproducts discharged from each esterification tower.

[0037] In some alternative technical solutions, the material entering the reflux tank requires further processing. The gas phase discharges from each stage can be liquefied and recycled separately into different reflux tanks, or they can be combined according to actual needs. For example, the gas phase discharge outlet of the last esterification tower is connected sequentially to the first condenser and the first reflux tank, and the corresponding pipelines of the gas phase discharge outlets of the remaining esterification towers are merged and connected sequentially to the second condenser and the second reflux tank.

[0038] For example, the gas phase outlet of the reactor is connected to the vacuum unit via a second pipeline, passing sequentially through a second condenser and a second reflux tank. Alternatively, the second gas phase outlet is connected to the vacuum unit via a second condenser and a second reflux tank.

[0039] It should be noted that the gas phase discharge from the final esterification tower mainly consists of byproducts with larger molecular weights. These can be condensed and recovered separately from the water and / or byproducts discharged from other esterification towers, depending on production needs. Furthermore, during the polycondensation reaction in the reactor, the water and / or byproducts discharged using the vacuum unit can share the second condenser and second reflux tank with other esterification towers, achieving equipment integration. Moreover, the tops of the first and second reflux tanks are respectively connected to venting pipes equipped with vent valves.

[0040] In some alternative technical solutions, a catalyst inlet is provided at the bottom of the last-stage esterification tower, and / or, a catalyst inlet is provided on the pipeline corresponding to the feed inlet of the last-stage esterification tower.

[0041] It should be noted that by opening a catalyst inlet on the relevant structure of the last-stage esterification tower, the catalyst can be added to the liquid phase system of the last-stage gas-liquid separation before the esterification reaction ends. This allows the catalyst to be evenly dispersed in the liquid phase before being returned to the esterification reaction system, preparing for the upcoming vacuum polycondensation reaction. This helps to shorten the total production time and can effectively improve the product quality stability of polyester polyols.

[0042] In some alternative technical solutions, a protective condenser is provided between the reflux tank and the vacuum unit, and an exhaust port with an exhaust valve is added to the outlet of the protective condenser.

[0043] In some alternative technical solutions, an acid value monitor and / or a hydroxyl value monitor, such as a conventionally used online near-infrared spectrometer, is installed inside the reaction vessel to detect the acid value and hydroxyl value of the polymer.

[0044] It should be noted that the online near-infrared spectrometer is used to monitor the hydroxyl and acid values ​​of the reaction system during the reaction stage, and to determine whether the product quality of polyester polyol meets the standards.

[0045] In some alternative technical solutions, a stirrer, such as a conventional vertical stirrer, is installed inside the reactor.

[0046] In some alternative technical solutions, a reaction liquid control valve is installed on the pipeline corresponding to the return reaction liquid inlet.

[0047] Example 1

[0048] This embodiment provides a polyester polyol production apparatus, such as... Figure 2As shown, the system includes a reactor 1, three esterification towers connected in series, and a vacuum unit 10. The reactor 1 has a feed inlet (not shown in the figure), and its upper part is equipped with a first gas phase outlet, a second gas phase outlet, and a return reaction liquid inlet. Along the material flow direction, the three esterification towers connected in series are, in sequence, a first-stage esterification tower 2, a second-stage esterification tower 3, and a third-stage esterification tower 4. Each esterification tower has a feed inlet at the bottom, a gas phase outlet at the top, and a bottom liquid phase outlet.

[0049] The bottom liquid outlet of the first-stage esterification tower 2 is connected to the feed inlet of the second-stage esterification tower 3. The bottom liquid outlet of the second-stage esterification tower 3 is connected to the feed inlet of the third-stage esterification tower 4. The bottom liquid outlet of the third-stage esterification tower 4 is connected to the return reaction liquid inlet of the reactor 1. The first gas phase outlet of the reactor 1 is connected to the feed inlet of the first-stage esterification tower 2.

[0050] The gas phase outlet of the third-stage esterification tower 4 is sequentially connected to the first condenser 5 and the first reflux tank 7. The gas phase outlets of the first-stage esterification tower 2, the second-stage esterification tower 3, and the second gas phase outlet of the reactor 1 are connected sequentially to the second condenser 6 and the second reflux tank 8. A control valve (not shown in the figure) is also installed on the connecting pipeline between the gas phase outlets of the first-stage esterification tower 2 and the second-stage esterification tower 3. A vacuum control valve 11 is installed on the connecting pipeline between the second gas phase outlet of the reactor 1 and the second condenser 6. The tops of the first reflux tank 7 and the second reflux tank 8 are respectively connected to venting pipelines equipped with venting valves 14. The top of the second reflux tank 8 has an additional gas phase outlet and is connected to the vacuum unit 10. A protective condenser 9 is installed on the pipeline between the second reflux tank 8 and the vacuum unit 10, and an exhaust port with an exhaust valve 13 is added at the outlet of the protective condenser 9. The protective condenser 9 can prevent residual gas phase from entering the vacuum unit 10.

[0051] Pumps 15 are installed between the bottom liquid outlet of the first-stage esterification tower 2 and the feed inlet of the second-stage esterification tower 3, between the bottom liquid outlet of the second-stage esterification tower 3 and the feed inlet of the third-stage esterification tower 4, the outlet of the first reflux tank 7, and the outlet of the second reflux tank 8, respectively, to realize material flow.

[0052] A reaction liquid control valve 12 is installed on the connecting pipeline between the bottom liquid outlet of the third-stage esterification column 4 and the return reaction liquid inlet of the reactor 1. An online near-infrared spectrometer and a conventional vertical stirrer are installed inside the reactor 1.

[0053] Application Example 1

[0054] The batch polyester polyol production process using the polyester polyol production apparatus described in Example 1 includes the following:

[0055] First stage reaction: Vacuum unit 10 is shut down, vacuum control valve 1 is closed, and according to the target settings, polyol (ethylene glycol and diethylene glycol, mass ratio 5:9) and polyacid (adipic acid, mass ratio of adipic acid to ethylene glycol 4:1) are added to reactor 1. The stirrer is turned on, and the temperature is raised to begin the esterification reaction. The acid value of the reaction system is 20-40 mg KOH / g, and the first stage reaction ends. During the first stage reaction, the gas phase in reactor 1 enters the first-stage esterification tower 2 through the first gas phase outlet. The top temperature of the first-stage esterification tower 2 is controlled at 100-110℃, and the bottom temperature at 160-200℃. The top gas phase of the first-stage esterification tower 2 (mainly water generated in the reaction) is cooled by the second condenser 6 and then enters the second reflux tank 8. The liquid phase from the bottom of the first-stage esterification column 2 is pumped to the second-stage esterification column 3 via pump 15. The top temperature of the second-stage esterification column 3 is controlled at 100–120°C, and the bottom temperature at 180–240°C. The vapor phase from the top of the second-stage esterification column 3 (mainly by-reaction products) is cooled by the second condenser 6 and then enters the second reflux tank 8. The liquid phase from the bottom of the second-stage esterification column 3 is pumped to the third-stage esterification column 4 via pump 15. The top temperature of the third-stage esterification column 4 is controlled at 100–120°C, and the bottom temperature at 200–260°C. The vapor phase from the top of the third-stage esterification column 4 (mainly by-reaction products) is cooled by the first condenser 5 and then enters the first reflux tank 7. The liquid phase from the bottom of the third-stage esterification column 4 is returned to the reactor 1 through a pipeline equipped with a reaction liquid control valve 12.

[0056] Second stage: The first gas phase outlet of reactor 1 is closed, the catalyst is added to reactor 1, the vacuum control valve 1 is opened, the vacuum unit 10 is turned on, the reactor temperature is kept constant, the vacuum degree is controlled at -0.1 to 0 MPa, and the polycondensation is stopped when the indicators are qualified: hydroxyl value = 72 to 79 mg KOH / g, acid value = 0.1 to 0.5 mg KOH / g, and moisture content is less than 0.05%. This completes the batch process for producing polyester polyols for one batch. The total production time for one batch is 11 hours.

[0057] The polyester polyol produced in Application Example 1 was mixed with MDI at a mass ratio of 1:1, and the mixture remained clear and transparent after 6 months of normal storage.

[0058] Example 2

[0059] This embodiment provides a polyester polyol production apparatus, such as... Figure 3 As shown, the difference from Example 1 is that it includes four esterification towers connected in series. Along the material flow direction, the four esterification towers connected in series are, in sequence, the first esterification tower 2, the second esterification tower 3, the third esterification tower 4, and the fourth esterification tower 16.

[0060] Application Example 2

[0061] The batch polyester polyol production process using the polyester polyol production apparatus described in Example 2 differs from Application Example 1 in the following ways: 1) The top temperature of the third-stage esterification tower 4 is controlled at 100–120°C, and the bottom temperature at 180–240°C; 2) The vapor phase at the top of the third-stage esterification tower 4 is cooled by the second condenser 6 and then enters the second reflux tank 8, while the liquid phase at the bottom of the third-stage esterification tower 4 is pumped by pump 15 to the fourth-stage esterification tower 16, with the top temperature of the fourth-stage esterification tower 16 controlled at 100–120°C and the bottom temperature at 200–260°C; 3) The catalyst originally added to the reactor 1 is added to the liquid phase at the bottom of the fourth-stage esterification tower 16. The rest is the same as in Application Example 1 and will not be repeated. The total production time for one batch is 10 hours.

[0062] The polyester polyol produced in Application Example 2 was mixed with MDI at a mass ratio of 1:1, and the mixture remained clear and transparent after 6 months of normal storage.

[0063] Comparative Example 1

[0064] A batch polyester polyol production apparatus using existing technology is employed. Specifically, the first and second esterification towers of Example 1 are left idle, and the first gas phase outlet of reactor 1 is connected to the inlet of the third esterification tower 4. The process parameters of the third esterification tower 4 are the same as those in Example 1.

[0065] Comparative Application Example 1

[0066] The batch polyester polyol production process was carried out using the polyester polyol production apparatus described in Comparative Example 1. The difference from Application Example 1 is that the first-stage esterification tower 2 and the second-stage esterification tower 3 were left idle, and the process parameters of the third-stage esterification tower 4 were the same as in Example 1. Everything else was the same as in Application Example 1 and will not be repeated. The total production time for one batch was 14 hours.

[0067] The polyester polyol produced in Comparative Application Example 1 was mixed with MDI at a mass ratio of 1:1. After being stored normally for 3 months, the mixture appeared cloudy and whitish.

[0068] This invention provides a polyester polyol production device, which is essentially a one-reactor-multiple-tower technical solution. It modifies the existing technology of configuring a single esterification tower in the reactor by introducing at least two esterification towers in series. This not only shortens the total production time but also effectively removes by-products such as polyether, acetal, and phenol. Moreover, the polyester polyol production device of this invention effectively improves the product quality stability of polyester polyols.

[0069] The above description is only a specific embodiment of the present utility model, but the protection scope of the present utility model is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present utility model fall within the protection and disclosure scope of the present utility model.

Claims

1. A polyester polyol production apparatus, characterized in that, Includes a reaction vessel, at least two stages of esterification towers connected in series, and a vacuum unit; Each esterification tower has a feed inlet, a gas phase outlet, and a bottom liquid phase outlet. The bottom liquid phase outlet of the previous esterification tower is connected to the feed inlet of the next esterification tower. The reactor is provided with at least a feed inlet, a gas outlet, and a return reaction liquid inlet; the gas outlet is connected to the feed inlet of the first-stage esterification tower, and the return reaction liquid inlet is connected to the bottom liquid outlet of the last-stage esterification tower. The reactor is connected to the vacuum unit.

2. The polyester polyol production apparatus according to claim 1, characterized in that, The polyester polyol production unit includes 2 to 6 esterification towers connected in series.

3. The polyester polyol production apparatus according to claim 1, characterized in that, The gas phase outlet of the reactor is connected to the feed inlet of the first-stage esterification tower via a first pipeline; the gas phase outlet of the reactor is connected to the vacuum unit via a second pipeline, passing through a condenser and a reflux tank in sequence, and a vacuum control valve is installed on the second pipeline. Alternatively, the reactor may be provided with a first gas phase outlet and a second gas phase outlet. The first gas phase outlet is connected to the inlet of the first-stage esterification tower, and the second gas phase outlet is connected to the vacuum unit after passing through a condenser and a reflux tank in sequence. A vacuum control valve is provided on the connecting pipeline between the second gas phase outlet and the condenser.

4. The polyester polyol production apparatus according to claim 3, characterized in that, The gas phase outlets of each esterification tower are connected sequentially to the condenser and the reflux tank.

5. The polyester polyol production apparatus according to claim 3 or 4, characterized in that, The vapor outlet of the last esterification tower is connected in sequence to the first condenser and the first reflux tank. The vapor outlets of the remaining esterification towers are connected in sequence to the second condenser and the second reflux tank, either by connecting the corresponding pipelines or by directly connecting them in sequence.

6. The polyester polyol production apparatus according to claim 5, characterized in that, The gas phase outlet of the reactor is connected to the vacuum unit via a second pipeline, passing through a second condenser and a second reflux tank in sequence; or, the second gas phase outlet is connected to the vacuum unit via a second condenser and a second reflux tank in sequence.

7. The polyester polyol production apparatus according to claim 3, characterized in that, A protective condenser is installed between the reflux tank and the vacuum unit, and an exhaust port with an exhaust valve is added to the outlet of the protective condenser.

8. The polyester polyol production apparatus according to claim 1, characterized in that, An acid value monitor and / or a hydroxyl value monitor are installed inside the reaction vessel.

9. The polyester polyol production apparatus according to claim 1, characterized in that, A stirrer is installed inside the reaction vessel.

10. The polyester polyol production apparatus according to claim 1, characterized in that, A reaction liquid control valve is installed on the pipeline corresponding to the return reaction liquid inlet.

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