A device for removing low molecular weight polymers from polystyrene circulating fluid

Abstract

The utility model belongs to the technical field of polystyrene production, and discloses a device for removing low molecular weight polymers in polystyrene circulating liquid, comprising a first-stage devolatilizer (1), a second-stage devolatilizer (2), a circulating condenser (3), a circulating condenser liquid collecting bag (4), a circulating liquid buffer tank (5), a low molecular weight polymer storage tank (6), a vacuum system tank (7), a newly added metering pump (8), and a prepolymerization reactor (9). The utility model can significantly reduce the content of low molecular weight polymers, and steadily improve the tensile strength and Vicat softening point of the product.

Description

Technical Field

[0001] The utility model belongs to the technical field of polystyrene production, and particularly relates to a device for removing low-molecular polymers in polystyrene circulating liquid. Background Art

[0002] High-impact polystyrene (HIPS) is a thermoplastic resin, which is prepared by adding polybutadiene rubber to styrene through a continuous bulk process and using thermal polymerization or initiator polymerization. Compared with general-purpose polystyrene, HIPS has greatly improved impact resistance and is widely used in electronic appliances, daily necessities and other fields.

[0003] The industrial production process of HIPS mainly consists of four stages: sol, polymerization, devolatilization and granulation. During the polymerization process, as time goes by, the viscosity of the system becomes too high and the device cannot produce. Therefore, a small amount of solvent needs to be added during the polymerization to control the viscosity of the system and ensure the normal polymerization.

[0004] The solvent used in the HIPS main unit is ethylbenzene, and the addition amount is about 10-20%. The polymerization conversion rate is generally controlled at about 80-90%, so about 10-20% of the styrene monomer will be recycled. In the production process, the styrene and ethylbenzene vapor evaporated from the prepolymerization reactor (R-101) and the styrene, ethylbenzene, and polymer vapor flashed from the first devolatilizer (DV-1) and the second devolatilizer (DV-2) are cooled by the condenser (E-6) and the condensate enters the buffer tank (T-6). This part is called circulating liquid. The circulating liquid is continuously sent back to R-101 for recycling by a pump.

[0005] After years of recycling, the circulating liquid will produce some low molecular weight polymers. These low molecular weight polymers will be sent back to the polymerization system to reduce the polymerization reaction rate and reduce the quality of the polymer. Therefore, the recovered styrene mixed solution needs to be completely discharged regularly. Such a process will increase raw material loss and cause a decline in product quality. Utility Model Content

[0006] The technical problem to be solved by the utility model is: how to remove low molecular weight polymers in the circulating fluid.

[0007] In order to solve the above technical problems, the specific technical solutions of the utility model are as follows:

[0008] A device for removing low molecular weight polymers in polystyrene circulating liquid, characterized in that it comprises a first stage devolatilizer 1, a second stage devolatilizer 2, a circulating condenser 3, a circulating condenser liquid collecting bag 4, a circulating liquid buffer tank 5, a low molecular weight polymer storage tank 6, a vacuum system tank 7, a newly added metering pump 8, and a prepolymerization reactor 9;

[0009] The first stage devolatilizer 1 and the second stage devolatilizer 2 are connected by a pipeline, and the gas phase outlets of both are connected to the inlet of the circulation condenser 3;

[0010] The circulating condenser liquid collecting bag 4 is arranged on the circulating condenser 3; the second stage devolatilizer 2 and the circulating condenser liquid collecting bag 4 are connected to the inlet of the circulating liquid delivery pump through a pipeline, and a valve 10 is arranged on the pipeline;

[0011] The inlet of the vacuum system tank 7 is connected to the circulation condenser 3, and the outlet is connected to the low molecular weight oligomer storage tank 6;

[0012] The inlet of the circulating liquid buffer tank 5 is connected to the circulating condenser 3, and the outlet is connected to the inlet of the circulating liquid delivery pump;

[0013] The outlet of the circulating liquid delivery pump is connected to the prepolymerization reactor 9;

[0014] The circulating condenser liquid collecting bag 4 and the second-stage devolatilizer 2 are connected to a newly added metering pump 8 through a pipeline, and the newly added metering pump 8 is connected to a low molecular weight polymer storage tank 6 .

[0015] Furthermore, a Roots blower is provided on the pipeline connecting the inlet of the vacuum system tank 7 and the circulation condenser 3 .

[0016] Furthermore, a devolatilizer material delivery pump is provided on the pipeline connecting the first stage devolatilizer 1 and the second stage devolatilizer 2 .

[0017] Furthermore, the speed of the newly added metering pump is 0-200rpm.

[0018] Furthermore, the stroke of the newly added metering pump is 0-100%.

[0019] Furthermore, the flow rate of the newly added metering pump is 100~1000m3 / h

[0020] The utility model has the following advantages: the content of low molecular weight polymers is greatly reduced, the tensile strength and Vicat softening point of the product are steadily improved, and a comprehensive comparison shows that the quality of the product is greatly improved; after the transformation, the number of times the circulating fluid is replaced is reduced from once a week to once a quarter, and the cycle of cleaning the storage tank is reduced from once every three years to no tank cleaning, thereby reducing the loss of raw materials and manpower. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The utility model is a schematic diagram of the structure of a device for removing low molecular weight polymers in polystyrene circulating fluid. DETAILED DESCRIPTION

[0022] In order to better understand the purpose, structure and function of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings.

[0023] like Figure 1 As shown, the device for removing low molecular weight polymers in polystyrene circulating liquid of the utility model includes a first-stage devolatilizer 1, a second-stage devolatilizer 2, a circulating condenser 3, a circulating condenser liquid collecting bag 4, a circulating liquid buffer tank 5, a low molecular weight polymer storage tank 6, a vacuum system tank 7, a newly added metering pump 8, and a prepolymerization reactor 9.

[0024] The first stage devolatilizer 1 and the second stage devolatilizer 2 are connected by a pipeline, and a devolatilizer material delivery pump P-4 is arranged on the pipeline connecting the two, and the gas phase outlets of the two are connected to the inlet of the circulation condenser 3;

[0025] The circulating condenser liquid collecting bag 4 is arranged on the circulating condenser 3; the second stage devolatilizer 2 and the circulating condenser liquid collecting bag 4 are connected to the inlet of the circulating liquid delivery pump P-6 through a pipeline, and a valve 10 is arranged on the pipeline;

[0026] The inlet of the vacuum system tank 7 is connected to the circulation condenser 3, and the outlet is connected to the low molecular weight oligomer storage tank 6;

[0027] The inlet of the circulating liquid buffer tank 5 is connected to the circulating condenser 3, and the outlet is connected to the inlet of the circulating liquid delivery pump P-6;

[0028] The outlet of the circulating liquid delivery pump P-6 is connected to the prepolymerization reactor 9;

[0029] The circulating condenser liquid collecting bag 4 and the second-stage devolatilizer 2 are connected to a newly added metering pump 8 through a pipeline, and the newly added metering pump 8 is connected to a low molecular weight polymer storage tank 6 .

[0030] The molten materials from the polymerization system enter the devolatilizers 1 and 2 in sequence. The gas phases in 1 and 2 enter the condenser 3 respectively. The high-boiling-point styrene oligomers and impurities are first condensed and enter the liquid collecting bag 4. The heavy components such as oligomers entrained in the flash gas of the devolatilizer 2 are condensed in the pipeline. The two liquid streams merge into the inlet of the circulating liquid delivery pump P-6 and are sent back to the prepolymerization reactor 9. The oligomers pollute the reaction system.

[0031] Add some red lines to mark the process, close valve 10, and send the condensate from the condenser liquid collecting bag 4 and the devolatilizer 2 to the storage tank 6 through the designed volume pump 8 to remove low molecular weight polymers in the circulating liquid.

[0032] Pipelines, metering pumps and low molecular weight polymer storage tanks are added between the two devolatilizers so that the flashed low molecular weight polymers are discharged into the low molecular weight polymer storage tanks separately and will not enter the polymerization system. After the device is put into use, the high impact polystyrene resin provided has the performance indicators of tensile strength ≥ 24MPa, Vicat softening point ≥ 88℃, and low molecular weight polymer content ≤ 0.35%.

[0033] Although the embodiments of the present invention are described in conjunction with the accompanying drawings, those skilled in the art may make several modifications and improvements without departing from the principle of the present invention, and these modifications and improvements should also be considered to belong to the protection scope of the present invention.

Claims

1. A device for removing low molecular weight polymers from polystyrene circulating fluid, characterized in that: It comprises a first-stage devolatilizer (1), a second-stage devolatilizer (2), a circulating condenser (3), a circulating condenser liquid collecting bag (4), a circulating liquid buffer tank (5), a low molecular weight polymer storage tank (6), a vacuum system tank (7), a newly added metering pump (8), and a prepolymerization reactor (9); The first stage devolatilizer (1) and the second stage devolatilizer (2) are connected via a pipeline, and the gas phase outlets of both are connected to the inlet of the circulation condenser (3); The circulating condenser liquid collecting bag (4) is arranged on the circulating condenser (3); the second stage devolatilizer (2) and the circulating condenser liquid collecting bag (4) are connected to the inlet of the circulating liquid delivery pump through a pipeline, and a valve (10) is arranged on the pipeline; The inlet of the vacuum system tank (7) is connected to the circulation condenser (3), and the outlet is connected to the low molecular weight polymer storage tank (6); The inlet of the circulating liquid buffer tank (5) is connected to the circulating condenser (3), and the outlet is connected to the inlet of the circulating liquid delivery pump; The outlet of the circulating liquid delivery pump is connected to the prepolymerization reactor (9); The circulating condenser liquid collecting bag (4) and the second-stage devolatilizer (2) are connected to a newly added metering pump (8) through a pipeline, and the newly added metering pump (8) is connected to a low molecular weight oligomer storage tank (6).

2. The device for removing low molecular weight polymers in polystyrene circulating fluid according to claim 1, characterized in that: A Roots blower is arranged on the pipeline connecting the inlet of the vacuum system tank (7) and the circulation condenser (3).

3. The device for removing low molecular weight polymers in polystyrene circulating fluid according to claim 1, characterized in that: A devolatilizer material conveying pump is arranged on the pipeline connecting the first stage devolatilizer (1) and the second stage devolatilizer (2).

4. The device for removing low molecular weight oligomers in polystyrene circulating fluid according to claim 1, characterized in that: The speed of the newly added metering pump is 0-200rpm.

5. The device for removing low molecular weight oligomers in polystyrene circulating fluid according to claim 1, characterized in that: The stroke of the newly added metering pump is 0-100%.

6. The device for removing low molecular weight oligomers in polystyrene circulating fluid according to claim 1, characterized in that: New metering pump flow rate 100~1000m 3 / h.

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