阅读说明：本技术 光气界面缩聚法pc低聚物废液回收利用的系统及方法 (System and method for recycling PC oligomer waste liquid by phosgene interfacial polycondensation method ) 是由 孙彩虹 李清利 姬生龙 肖彦 赵西宝 张明华 于 2020-03-27 设计创作，主要内容包括：本发明公开了一种光气界面缩聚法PC低聚物废液回收利用的系统及方法,系统,包括：依次连接的次品聚合物罐、进料泵、缓冲罐和聚合反应器,进料泵和缓冲罐之间的连接管线与闪蒸槽连接；冷却器,其进口与双酚A钠盐源连接,其出口与所述聚合反应器连接。采用以上系统将PC低聚物废液回收利用,再次参与聚合反应,回收制备聚碳酸酯产品,使低聚物废液全部产品化,可以取消脱挥单元蒸馏装置对低聚物废液的蒸馏作业点,可以彻底消除蒸馏后的低聚物渣料露天放置对周边环境产生的影响,最大程度降低环境污染,实现经济效益。(The invention discloses a system and a method for recycling PC oligomer waste liquid by a phosgene interfacial polycondensation method, wherein the system comprises the following steps: the defective polymer tank, the feeding pump, the buffer tank and the polymerization reactor are sequentially connected, and a connecting pipeline between the feeding pump and the buffer tank is connected with the flash tank; a cooler having an inlet connected to a bisphenol A sodium salt source and an outlet connected to the polymerization reactor. By adopting the system, the PC oligomer waste liquid is recycled, participates in polymerization reaction again, and is recycled to prepare polycarbonate products, so that the oligomer waste liquid is completely commercialized, the distillation operation point of a devolatilization unit distillation device on the oligomer waste liquid can be cancelled, the influence of open-air placement of the distilled oligomer slag on the surrounding environment can be thoroughly eliminated, the environmental pollution is reduced to the greatest extent, and the economic benefit is realized.)

1. A system for recycling PC oligomer waste liquid by a phosgene interfacial polycondensation method is characterized in that: the method comprises the following steps: a defective polymer tank, a feeding pump, a buffer tank and a polymerization reactor which are connected in sequence;

a cooler having an inlet connected to a bisphenol A sodium salt source and an outlet connected to the polymerization reactor.

2. The system for recycling PC oligomer waste liquid by using the phosgene interfacial polycondensation method according to claim 1, characterized in that: the outlet of the feeding pump is connected with a first branch pipeline and a second branch pipeline, the tail end of the first branch pipeline is communicated with the upper end of the inferior-quality polymer tank, and the tail end of the second branch pipeline is connected with the buffer tank.

3. The system for recycling PC oligomer waste liquid by using the phosgene interfacial polycondensation method according to claim 2, characterized in that: a backflow valve is arranged on the first branch pipeline, and a buffer tank hand valve is arranged on the second branch pipeline.

4. The system for recycling PC oligomer waste liquid by using the phosgene interfacial polycondensation method according to claim 1, characterized in that: and a valve is arranged on a connecting pipeline between the feeding pump and the buffer tank and a connecting pipeline of the flash tank.

5. The system for recycling PC oligomer waste liquid by using the phosgene interfacial polycondensation method according to claim 1, characterized in that: and an emptying valve is arranged at the top of the buffer tank.

6. The system for recycling PC oligomer waste liquid by using the phosgene interfacial polycondensation method according to claim 1, characterized in that: a metering pump is arranged between the buffer tank and the polymerization reactor.

7. A method for recycling PC oligomer waste liquid by a phosgene interfacial polycondensation method is characterized by comprising the following steps: the method comprises the following steps:

conveying oligomer waste liquid generated in the polycarbonate preparation process to a defective polymer tank for treatment;

conveying the treated oligomer waste liquid to a buffer tank for temporary storage, and introducing nitrogen to the top of the buffer tank to ensure that the upper part of the buffer tank is filled with nitrogen all the time;

and conveying the oligomer waste liquid in the buffer tank to the polymerization reactor to participate in the reaction again, and supplementing the cooled bisphenol A sodium salt in the reaction process.

8. The method for recycling the PC oligomer waste liquid by the phosgene interfacial polycondensation method according to claim 7, characterized in that: and when the liquid level in the buffer tank reaches 50-80%, starting the metering pump.

9. The method for recycling the PC oligomer waste liquid by the phosgene interfacial polycondensation method according to claim 8, characterized in that: and when the liquid level in the buffer tank reaches 80%, starting the metering pump.

10. The method for recycling the PC oligomer waste liquid by the phosgene interfacial polycondensation method according to claim 7, characterized in that: and (3) adjusting the flow of the metering pump to be stable, observing the layering condition of the polymer at the outlet of the flash evaporation tank pump, adding the oligomer for a certain time, sampling and detecting the molecular weight and the dispersity of the four-stage heavy phase, and tracking the melt index change of the granules.

Technical Field

The invention belongs to the technical field of polycarbonate preparation, and particularly relates to a system and a method for recycling PC oligomer waste liquid by a phosgene interfacial polycondensation method.

Background

The information in this background section is only for enhancement of understanding of the general background of the invention and is not necessarily to be construed as an admission or any form of suggestion that this information forms the prior art that is already known to a person of ordinary skill in the art.

Polycarbonate resin (PC for short) prepared by an interfacial polycondensation method of bisphenol A and phosgene is engineering plastic with excellent comprehensive performance, has good optical transparency and impact strength, excellent heat resistance, cold resistance, dimensional stability, electric insulation and other properties, and is widely applied to the fields of manufacturing automobile parts, optical parts, building plates, medical appliances, household appliances and the like. The production process flow of the polycarbonate mainly comprises the working procedures of reaction synthesis, washing separation, devolatilization drying, extrusion granulation and the like. During polycarbonate production, off-specification materials are prone to occur, particularly during initial start-up and during production fluctuations, and how to dispose of these off-specification materials has been a problem.

At present, a common treatment method is a distillation drying method, a distillation device in a devolatilization drying system is used for treating unqualified materials, in the process, waste residues left after distillation need to be aired for a long time, residual dichloromethane has a large smell, generated wastewater cannot be treated, and the surrounding environment is seriously affected. The waste residue that produces can only sell as the danger useless, if exceed the handling capacity and just can't deal with, can only regard as useless temporary storage of solid to handle, occupy a large amount of spaces.

Disclosure of Invention

In order to solve the technical problems in the prior art, the invention aims to provide a system and a method for recycling PC oligomer waste liquid by a phosgene interfacial polycondensation method. Thus not only solving the problem of environmental pollution, but also increasing economic benefits.

In order to achieve the above object, one or more embodiments of the present invention disclose the following technical solutions:

the invention provides a system for recycling PC oligomer waste liquid by a phosgene interfacial polycondensation method, which comprises the following steps: a defective polymer tank, a feeding pump, a buffer tank and a polymerization reactor which are connected in sequence;

a cooler having an inlet connected to a bisphenol A sodium salt source and an outlet connected to the polymerization reactor.

The second aspect of the invention provides a method for recycling PC oligomer waste liquid by a phosgene interfacial polycondensation method, which comprises the following steps:

conveying oligomer waste liquid generated in the polycarbonate preparation process to a defective polymer tank for treatment;

conveying the treated oligomer waste liquid to a buffer tank for temporary storage;

and conveying the oligomer waste liquid in the buffer tank to the polymerization reactor to participate in the reaction again, and supplementing the cooled bisphenol A sodium salt in the reaction process.

According to the detection, the polycarbonate is mostly oligomer and methylene dichloride except water in the unqualified material waste liquid generated in the initial start or during the production fluctuation, and contains a small amount of bisphenol A, caustic soda and sodium carbonate, so that the polycarbonate can be called oligomer waste liquid, and the oligomer waste liquid is alkaline as a whole.

It is found through experiments that the high molecular polymer is subjected to chain scission (forming a low molecular polymer with a short molecular chain, the molecular weight is below 20000) under alkaline conditions, that is, after the oligomer waste liquid is left for a period of time, part of the high molecular polymer is subjected to chain scission to generate the low molecular polymer, and the polymer with the short molecular chain can participate in the reaction again. The existing polymerization reaction principle, reaction conditions and field environment are comprehensively considered, so that the oligomer waste liquid can be returned to the polymerization reactor to participate in the reaction again, and the product recycling is realized. After the polymer solution prepared by the method is washed, separated, devolatilized and dried, all indexes of the generated sheet meet the existing standard.

Compared with the prior art, one or more technical schemes of the invention have the following beneficial effects:

by adopting the system, the PC oligomer waste liquid is recycled, the PC oligomer waste liquid participates in polymerization reaction again, and polycarbonate products are recycled, so that the oligomer waste liquid is completely commercialized, the distillation operation point of a devolatilization unit distillation device on the oligomer waste liquid can be cancelled, and frequent operation risks are reduced (slag materials distilled out from a distillation kettle need to be loaded into a ton bag once every three days, 4 workers need to continuously load the slag materials into the ton bag for 10 hours every time, and volatile dichloromethane in the loading process can influence the surrounding environment and human bodies). The influence of the distilled oligomer slag material placed in the open air on the surrounding environment can be thoroughly eliminated, the environmental pollution is reduced to the maximum extent, and the economic benefit is realized.

And the defective polymer tank is used for storing oligomer waste liquid generated in the process of driving or adjusting production.

And the flash evaporation tank temporarily stores the PC solution generated by the reaction in the polymerization reactor in the flash evaporation tank, and dichloromethane is added to reduce the concentration of the PC solution and simultaneously take away heat generated after the reaction to reduce the temperature of the solution.

The buffer tank is used for temporarily storing the oligomer waste liquid, so that the oligomer waste liquid can be quantitatively pumped into the polymer reactor by using a metering pump.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the invention and not to limit the invention.

Fig. 1 is a schematic overall structure diagram of a system according to an embodiment of the present invention.

The system comprises a polymerization reactor, a flash tank, a bisphenol A sodium salt cooler, a defective polymer tank, a defective feed pump inlet hand valve, a feed pump, a reflux valve, a buffer tank hand valve, a discharge valve, a buffer tank, a metering pump front hand valve, a metering pump rear hand valve, a metering pump inlet hand valve, a polymerization reactor, a flash tank, a bisphenol A sodium salt cooler and a feeding pump, wherein the feeding pump inlet hand valve is 1, the defective polymer tank is 2, the defective feed pump inlet.

Detailed Description

It is to be understood that the following detailed description is exemplary and is intended to provide further explanation of the invention as claimed. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

The invention provides a system for recycling PC oligomer waste liquid by a phosgene interfacial polycondensation method, which comprises the following steps: a defective polymer tank, a feeding pump, a buffer tank and a polymerization reactor which are connected in sequence;

a cooler having an inlet connected to a bisphenol A sodium salt source and an outlet connected to the polymerization reactor.

The buffer tank is used for counting the injection amount of the oligomer waste liquid through a metering pump; the defective polymer tank is physically far from the surge tank, and because the two tanks are in different cell boundaries and the metering pump has limited lift and flow, it is not possible to directly pump oligomer waste from the defective polymer tank into the polymerization reactor.

In some embodiments, the outlet of the feed pump is connected to a first branch line having an end communicating with the upper end of the inferior polymer tank and a second branch line having an end connected to the surge tank.

Furthermore, a return valve is arranged on the first branch pipeline, and a buffer tank hand valve is arranged on the second branch pipeline.

The first branch pipeline is communicated with the upper end of the defective polymer tank, the feeding pump acts after the return valve is opened, and the purpose of opening the return valve is to prevent the pump from being held back to cause pump damage.

In some embodiments, a valve is provided on the connecting line between the feed pump and the surge tank and the connecting pipe of the flash drum.

In some embodiments, the top of the buffer tank is provided with a blow valve. The valve can be used for introducing nitrogen into the tank, so that the nitrogen is filled above the liquid in the tank all the time, and the material is prevented from being oxidized.

In some embodiments, a metering pump is disposed between the surge tank and the polymerization reactor.

The second aspect of the invention provides a method for recycling PC oligomer waste liquid by a phosgene interfacial polycondensation method, which comprises the following steps:

conveying oligomer waste liquid generated in the polycarbonate preparation process to a defective polymer tank for treatment;

conveying the treated oligomer waste liquid to a buffer tank for temporary storage, and introducing nitrogen to the top of the buffer tank to ensure that the upper part of the buffer tank is filled with nitrogen all the time;

and conveying the oligomer waste liquid in the buffer tank to the polymerization reactor to participate in the reaction again, and supplementing the cooled bisphenol A sodium salt in the reaction process.

Conveying the PC solution in the polymerization reactor to a flash tank for temporary storage, and adding a dichloromethane solvent into the flash tank so as to reduce the concentration of the PC solution, absorb the heat released by the reaction and reduce the temperature of the PC solution.

After standing for a period of time, taking the PC solution from the flash tank to analyze the chemical index and the physical state of the PC solution, and judging whether the PC solution meets the relevant standards.

In some embodiments, the metering pump is turned on when the liquid level in the buffer tank reaches 80%. The liquid level in the buffer tank cannot be too low, should be at least more than 50%, but the tank cannot be full, according to practical experience, the metering pump is started, generally defined as 80% liquid level.

In some embodiments, the flow of the metering pump is adjusted to be stable, the polymer layering condition at the outlet of the flash evaporation tank pump is observed, after the oligomer is added for a certain time, the molecular weight and the dispersity of the four-stage heavy phase are detected by sampling, and the melt index change of the granules is tracked.