WO2022042565A1

WO2022042565A1 - Nylon 6 production process, system, and product

Info

Publication number: WO2022042565A1
Application number: PCT/CN2021/114359
Authority: WO
Inventors: 赵冉; 孙允南; 杨东昌; 张庆国; 马中星; 陈忠强; 周传山; 袁甫荣
Original assignee: 聊城鲁西聚酰胺新材料科技有限公司
Priority date: 2020-08-31
Filing date: 2021-08-24
Publication date: 2022-03-03
Also published as: CN112094406A

Abstract

The present application relates to the field of textile raw materials, and specifically provides a nylon 6 production process, a system, and a product. The nylon 6 production process comprises the following steps: caprolactam, water, a molecular weight regulator, benzylamine, and a flatting agent are used as reaction raw materials, and are preheated to enter a polymerization working section, a polymerization reaction is a two-stage polymerization process of first pressurizing and then depressurizing, and a solution generated in the process of depressurized polymerization is passed into pressurized polymerization; pelletizing is performed on a product after polymerization; extraction is performed on the water after pelletizing; and the solution after extraction is evaporated and passed into pressurized polymerization. The problem in the prior art that when producing nylon 6 by using a two-stage polymerization method, a large volume of moisture is generated in post polymerization, resulting in requiring multiple extraction towers to perform multi-step extraction, the extraction efficiency is low and heat sources are wasted is solved.

Description

A kind of nylon 6 production process and its system and product

technical field

The application relates to the field of textile raw materials, and specifically provides a nylon 6 production process, a system and a product thereof.

Background technique

The information disclosed in the Background of the Application is intended to enhance understanding of the general background of the application and should not necessarily be taken as an acknowledgement or any form of suggestion that this information is already known as the prior art to a person of ordinary skill in the art.

Nylon 6 was put into industrial production in 1943 and has developed rapidly due to its good physical properties and textile properties. Nylon 6 is formed by ring-opening polymerization of caprolactam, and its polymerization can be divided into two types according to the different ring-opening agents used: one is to use alkali substances as ring-opening agents, which is called alkali polymerization; Using water as a ring-opening agent is called hydrolysis polymerization. The production of nylon 6 chips for spinning generally adopts hydrolysis polymerization.

In the prior art, there are a one-stage method and a two-stage method for the production technology of caprolactam hydrolysis polymerization to prepare nylon 6, wherein, the one-stage method is a one-stage normal pressure polymerization process. The process is simple and the operation is convenient, but the polymerization reaction has a long residence time and can only produce low-viscosity resin. The two-stage method refers to the polymerization before pressure and the polymerization after normal pressure. The polymerization before pressure is conducive to the hydrolysis and ring opening of caprolactam, and the polymerization after normal pressure is conducive to dehydration to increase the viscosity of the resin. However, the inventors found that the two-stage polymerization method is due to In the post-polymerization process, a large amount of water is generated, and the water carries a large amount of small-molecule polycaprolactam, which can be used as a raw material. Therefore, in the prior art, the water generated by the post-polymerization is usually extracted, which often requires multi-step series extraction, and the extraction efficiency is relatively high. In addition, the heat is required for extraction, and the heat demand of multiple extraction towers is large, which brings great waste to industrial heat sources.

SUMMARY OF THE INVENTION

In the process of producing nylon 6 by two-stage polymerization method in the prior art, the post-polymerization produces a large amount of water, which causes the need for multiple extraction towers to carry out multi-step extraction, and the extraction efficiency is low and wastes the problem of heat source.

In one or some embodiments of the present application, a nylon 6 production process is provided, comprising the steps of:

1) preheating raw material caprolactam, water, molecular weight regulator, benzylamine and matting agent into a fluid mixture;

2) After preheating, the fluid mixture enters the polymerization section, and the polymerization reaction is a two-stage polymerization process with pre-pressurization and then decompression, and the decompression polymerization process continuously produces a solution, and the generated solution is passed into the pressurized polymerization;

3) Single-column extraction is carried out after granulating the product after the reduced pressure polymerization, the extracted solution is evaporated and then passed into the pressure polymerization, and the extracted solid phase particles are nylon 6.

In one or some embodiments of the present application, a system for realizing the above nylon 6 production process is provided, comprising a pressurized polymerizer, a decompression polymerizer, a pelletizer, an extraction tower, and an upper discharge port of the extraction tower connected in sequence. The evaporation device is connected, and the lower discharge port is communicated with the packaging section through a gas-phase conveying pipeline; the solution discharged from the decompression polymerizer is also passed into the evaporation device.

In one or some embodiments of the present application, a product prepared by the above-mentioned nylon 6 production process or the system of the above-mentioned nylon 6 production process is provided.

One or some of the technical solutions in the above-mentioned technical solutions have the following advantages or beneficial effects:

1) In order to reduce investment costs, realize energy saving and consumption reduction, and at the same time ensure the production of high-quality high-speed spinning semi-matte slices for civilian use, this application adopts two-stage polymerization, one-stage extraction, and one-stage drying process, and the polymerization tube has obvious heat transfer section and balance. The reaction rate is high and the distribution is uniform. The reaction time of the two-stage polymerization method itself is shorter than that of the one-stage continuous polymerization method. The one-stage continuous polymerization method has one polymerization tube, which is operated at normal pressure and produces a high viscosity of 2.7. The polymerization time is 20-22h. With reduced pressure operation, the highest viscosity is 3.5, the polymerization time is 1.3-4h, the recovery system adopts three-effect evaporation, and the polymerization molecular weight is uniform.

2) In this application, since the post-polymerization of the two-stage polymerization is changed to the post-polymerization under reduced pressure, the moisture generated in the post-polymerization process is greatly reduced, while the molecular weight of the nylon 6 is further improved, the moisture in the extraction process is reduced, and the multi-step is connected in series. The extraction is changed to a tower extraction, which reduces the use of industrial heat sources.

3) The present application improves the energy utilization efficiency and the economic effect of energy utilization through the step-by-step utilization of steam heat energy, so as to achieve the purpose of clean production, energy saving and consumption reduction. In the nylon 6 production process, 1.0MPa steam is used as the first-stage heat medium for three-effect evaporation, the steam evaporated from the first effect is used as the heat medium for the second-effect evaporation, and the steam evaporated from the second-effect is used as the heat medium for the three-effect evaporation. Efficient evaporation of the exhaust gas after gas-liquid separation is preheated relative to the extraction water, and the condensate is used to heat the fresh caprolactam raw material, and then the ammonium sulfate plant is used as a refrigerant for ammonium sulfate crystallization, so as to realize the sixth-order utilization of steam heat energy. Through the gradient utilization of steam energy, steam consumption is reduced. It has been proved by operation that the unit steam consumption of nylon 6 slices is about 0.9 tons, while the unit steam consumption of nylon 6 slices by other domestic enterprises is about 1.2 tons. The condensed water just provides refrigerant for caprolactam ammonium sulphate crystallization device, and at the same time reduces the energy consumption of caprolactam ammonium sulphate crystallization

4) The nylon 6 polymerization production process mainly includes the configuration of raw materials, pre-polymerization reaction, post-polymerization reaction, dicing, extraction, drying, pneumatic conveying, slice packaging and recovery of concentrated liquid. The application adopts two-stage synthesis and one-stage extraction. , A drying method to produce nylon 6 products. Among them, the recovery of concentrated liquid is the main energy-consuming unit. The content of caprolactam in the extraction water is about 8%-12%. Using 1.0MPa steam as the heat source, the caprolactam is concentrated to 70%-75% by means of multi-effect evaporation. After mixing, return to the front polymerization tube for recycling. In this process, steam consumption is the main energy consumption index. In order to reduce the comprehensive energy consumption of production, the comprehensive utilization of steam energy is carried out in different gradients, so as to improve the energy utilization efficiency and achieve the purpose of energy saving and consumption reduction.

Description of drawings

The accompanying drawings that constitute a part of the present application are used to provide further understanding of the present application, and the schematic embodiments and descriptions of the present application are used to explain the present application and do not constitute improper limitations on the present application.

1 is a flow chart of the nylon 6 production process described in one embodiment.

2 is a flow chart of the nylon 6 production process described in Example 1.

Fig. 3 is the connection structure diagram of the extraction tower described in Example 2 and the three-effect evaporation device.

Among them, 1. evaporator; 2. reboiler; 3. gas-liquid separator; 4. hot water heat exchanger; 5. extraction column; 6. caprolactam jacketed pipe; 7. caprolactam thiamine crystallization; 8. condensation liquid; 9.1.0MPa steam; 10.0.2MPa steam; 11. Desalted water; 12.110℃ hot water.

detailed description

The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative efforts shall fall within the protection scope of the present application.

In the prior art, in the process of producing nylon 6 by a two-stage polymerization method, a large amount of water is generated by post-polymerization, resulting in the need for multiple extraction towers to perform multi-step extraction, the problems of low extraction efficiency and waste of heat sources.

Preferably, the molecular weight regulator is acetic acid, and the matting agent is titanium dioxide.

Preferably, the extraction is a one-stage extraction, the nylon 6 after extraction is sliced and dried, and the slices are dried and then output.

Preferably, in step 1), the caprolactam is melted in a melting reactor, and during the melting process, the mixture of water, molecular weight regulator, benzylamine and matting agent is continuously added until the molten state becomes a fluid mixture, and the fluid mixture After preheating, it enters the polymerization section.

In the prior art, only caprolactam is often preheated, and the preheated caprolactam is mixed with other additives into the pressurized polymerizer. Reuse, often need to carry out processing such as concentration, cracking, in order to reduce the content of polycaprolactam; and different from this, this step is used as the processing section of the raw material in this application, in this raw material processing section, on the one hand, fresh caprolactam Continuously form fluid polymer with additives; on the other hand, the solution produced in the subsequent section (the solution produced by reduced pressure polymerization in the polymerization section and the solution produced by evaporation in the extraction section) continues to flow in and participate in the melting together with fresh caprolactam and additives In the process of forming a fluid, the polymer forming a fluid enters the polymerization section after preheating and continues to participate in the reaction as part of the raw materials. Such a treatment method enables the solution generated in the subsequent section, especially the solution generated after reduced pressure polymerization, to be reused without concentrating, cracking and other operations, and can also ensure that the produced nylon 6 chips meet the quality requirements, and save the process, Reduced costs and reduced energy consumption.

It is possible to directly return the aqueous solution containing low molecular weight polycaprolactam produced after the polymerization reaction of the present application to the pressurized polymerization section without any treatment (such as cracking treatment, etc.), which is an important step for realizing the continuous production of nylon 6 in the present application.

Preferably, in step 2), the pressurized polymerization includes: feeding the fluid mixture into a polymerization section to perform pressurized polymerization; the pressurized polymerization section is divided into upper and lower parts, the upper part is mainly for pressurized ring opening, and the lower part is carried out Addition reaction.

Preferably, the heat required for hydrolysis and ring opening is provided by the latent heat of the liquefaction of the gas-phase biphenyl-diphenyl ether at 260°C, and the lower part of the polyaddition reaction, and the exothermic reaction heat is taken away by the gasification of the liquid-phase biphenyl-biphenyl ether at 260°C.

Preferably, the pressurized open-loop pressure is 0.15-0.2 MPa.

Preferably, the residence time for the material to undergo the ring-opening reaction is 50-55 min.

Preferably, the residence time of the material for the polyaddition reaction is 2.5-4.5h.

Preferably, in step 2), the reduced-pressure polymerization comprises: the pressure-polymerized product is sent into the middle of the reduced-pressure polymerizer to carry out reduced-pressure polymerization, the reduced-pressure polymerization reaction is a condensation reaction, and the moisture generated during the reduced-pressure polymerization is removed from the reduced-pressure polymerization. The upper part of the vessel is discharged and passed into the pressurized polymerization for continuous reaction.

In order to speed up the polymerization process, the conventional treatment method in this area is to evaporate the water and caprolactam produced after the polymerization. In the pressurized polymerization, the steam at the top of the tower is condensed and then discharged to the sewage treatment station for treatment. This operation can timely remove the water produced by the polymerization and the caprolactam that did not participate in the reaction from the vacuum polymerization reaction, which is helpful to speed up the polymerization reaction. During the process, water and caprolactam are sent to the water concentration process, and after further cracking treatment operations are carried out, they are returned to the pressurized polymerization, and continue to be used as raw materials. However, the process is too complicated, the energy consumption is large, and the cost is also high.

In the polymerization section of the present application, the reduced-pressure polymerization is fed from the middle, the upper part is dehydrated with a negative pressure vacuum, and the liquid components are continuously precipitated, and the molten nylon 6 is precipitated from the bottom, and the precipitated liquid components are mainly water. Carrying a large amount of low molecular weight polycaprolactam, the lower the molecular weight of the polycaprolactam, the easier it is to be taken out. This part of the polycaprolactam is brought into the raw material processing section and processed as a raw material into the polymerization section, and continues to participate in the reaction, avoiding a large amount of low molecular weight polycaprolactam. Polycaprolactam undergoes a condensation reaction, which affects the distribution of molecular weight. At the same time, due to the dehydration of the condensation reaction in the post-polymerization process, the water is removed from the reactor in time, which promotes the reaction to proceed to the right and accelerates the reaction process. Compared with the prior art, the present application can not only remove water and low-molecular-weight polycaprolactam from the reduced-pressure polymerization reaction in time to speed up the reaction process, but also combine this part of the solution with fresh water without concentrating, cracking and other processing procedures. The caprolactam and additives are mixed to form a fluid polymer, which is preheated and fed back into the pressurized polymerization as part of the raw materials to continue to participate in the reaction.

Preferably, the reduced pressure polymerization utilizes negative pressure vacuum dehydration.

Preferably, the material is subjected to condensation reaction for a residence time of 2.5-3h.

Preferably, the extraction section uses steam as a power source.

Preferably, the steam is 1.0 MPa steam.

Preferably, 1.0MPa steam is used as the first-stage heat medium of the three-effect evaporation, the steam evaporated from the first effect is used as the heat medium of the second-effect evaporation, the evaporation from the second-effect evaporation is used as the heat medium of the third-effect evaporation, and the steam evaporated by the three-effect evaporation is used as the heat medium of the third-effect evaporation The gas phase after the separation of spent gas and liquid is preheated to the extraction water, and the condensate is used to heat the fresh caprolactam raw material, and then it goes to the ammonium sulfate plant to be the refrigerant for ammonium sulfate crystallization.

Preferably, the extraction tower is connected to a three-effect evaporation device, and the three-effect evaporation device is a device in which three sets of evaporators and reboilers are connected in series.

Preferably, the upper part of the extraction tower is connected with a three-effect evaporation device, and the bottom part is connected with a gas-liquid separator through a hot water heat exchanger, and the liquid phase of the gas-liquid separator is a caprolactam outlet.

Example 1

The present embodiment provides a nylon 6 production process, comprising the steps:

1) The raw materials caprolactam, water, acetic acid, benzylamine and titanium dioxide are preheated into a fluid mixture. The caprolactam is melted in a melting reactor, and during the melting process, the mixture of water, molecular weight regulator, benzylamine and matting agent is continuously added until the molten state becomes a fluid mixture.

2) After preheating, the fluid mixture enters the polymerization section, and the polymerization reaction is a two-stage polymerization process with pre-pressurization and then decompression. The decompression polymerization process continuously produces a solution, and the resulting solution is mixed with fresh caprolactam as a raw material to carry out step 1) A fluid mixture is formed after the treatment in the medium, which is preheated and passed into the pressurized polymerization.

The pressurized polymerization includes: feeding the fluid mixture into the polymerization section to carry out pressure polymerization; the pressurized polymerization section is divided into upper and lower parts, the upper part is mainly subjected to pressure ring-opening, and the lower part is subjected to addition polymerization; The pressure is 0.15-0.2MPa; the residence time of the material for ring-opening reaction is 50-55min; the residence time of the material for polyaddition reaction is 2.5-4.5h.

The heat required for hydrolysis and ring opening is provided by the latent heat of the liquefaction of the gas-phase biphenyl-diphenyl ether at 260°C, and the lower part of the polyaddition reaction, and the exothermic reaction heat is taken away by the gasification of the liquid-phase biphenyl-biphenyl ether at 260°C.

The reduced-pressure polymerization includes: the pressurized polymerization product is sent to the middle of the reduced-pressure polymerizer, and the reduced-pressure polymerization is carried out. The reduced-pressure polymerization reaction is a condensation reaction. The continuous reaction is carried out in the pressure polymerization; the material is subjected to condensation reaction and the residence time is 2.5-3h. Decompression polymerization utilizes negative pressure vacuum dehydration;

3) After granulating the product after the reduced-pressure polymerization, extraction is performed, the solution after the extraction is evaporated and then passed into the pressure-polymerization, and the extracted solid-phase particles are nylon 6. The extraction is a one-stage extraction, the nylon 6 after extraction is sliced and dried, and the slices are dried and then output.

The extraction section uses steam as the power source; the steam is 1.0MPa steam; 1.0MPa steam is used as the first-stage heat medium of the three-effect evaporation, the steam evaporated from the first effect is used as the heat medium of the second-effect evaporation, and the steam evaporated by the second effect is used as the heat medium for the second-effect evaporation. Evaporation is used as a three-effect heating medium, and the gas phase after the three-effect evaporation is used to preheat the extracted water, and the condensate is used to heat the fresh caprolactam raw material. .

The two-stage polymerization described in this example can produce high-speed spinning high-end polymers with a viscosity of 2.8-3.4.

Example 2

This embodiment provides a nylon 6 production device, which can realize the nylon 6 production process described in Example 1, including a pressurized polymerizer, a decompression polymerizer, a granulator, an extraction tower 5, which are connected in sequence. The upper discharge port of the extraction tower is connected to the evaporation device, and the lower discharge port is communicated with the packaging section through a gas phase conveying pipeline; the solution discharged from the reduced pressure polymerizer is also passed into the evaporation device.

The extraction tower 5 is connected with a three-effect evaporation device, and the three-effect evaporation device is a device in which three sets of evaporators 1 and reboilers 2 are connected in series. The upper part of the extraction tower 5 is connected with a three-effect evaporation device, and the bottom part is connected with the gas-liquid separator 3 through the hot water heat exchanger 4, and the liquid phase of the gas-liquid separator 3 is the caprolactam discharge port.

The above disclosures are only the preferred embodiments of the present application, and of course they cannot limit the scope of the rights of the present application. Therefore, equivalent changes made according to the patent scope of the present application are still within the scope of the present application.

Claims

A kind of nylon 6 production technology, is characterized in that, comprises the steps:

1) preheating raw material caprolactam, water, molecular weight regulator, benzylamine and matting agent into a fluid mixture;

2) After preheating, the fluid mixture enters the polymerization section, and the polymerization reaction is a two-stage polymerization process with pre-pressurization and then decompression, and the decompression polymerization process continuously produces a solution, and the generated solution is passed into the pressurized polymerization;

3) Single-column extraction is carried out after granulating the product after the reduced pressure polymerization, the extracted solution is evaporated and then passed into the pressure polymerization, and the extracted solid phase particles are nylon 6.
The nylon 6 production process according to claim 1, wherein the molecular weight regulator is acetic acid, and the matting agent is titanium dioxide.
The nylon 6 production process according to claim 1, wherein the extraction is a one-stage extraction, the nylon 6 after the extraction is sliced and dried, and the slices are dried and output.
Nylon 6 production process as claimed in claim 1, is characterized in that, in step 1), caprolactam is placed in melting reactor and melted, and in the melting process, continuous addition of water, molecular weight regulator, benzylamine and matting agent mixture until the molten state becomes fluid.
The nylon 6 production process according to claim 1, wherein in step 2), the pressurized polymerization comprises: feeding the fluid mixture into a polymerization section to carry out pressurized polymerization; the pressurized polymerization section is divided into upper and lower parts , the upper part is mainly subjected to pressure ring opening, and the lower part is polyaddition reaction;

Preferably, the heat required for hydrolysis and ring opening is provided by the latent heat of the liquefaction of the gas-phase biphenyl-diphenyl ether at 260°C, and the lower part of the polyaddition reaction, and the reaction heat is taken away by the gasification of the liquid-phase biphenyl-biphenyl ether at 260°C;

Preferably, the pressurized open-loop pressure is 0.15-0.2MPa;

Preferably, the residence time for the material to carry out the ring-opening reaction is 50-55min;

Preferably, the residence time of the material for the polyaddition reaction is 2.5-4.5h.
The nylon 6 production process as claimed in claim 1, wherein in step 2), the reduced-pressure polymerization comprises: the pressure-polymerized product is sent into the middle of the reduced-pressure polymerizer, and the reduced-pressure polymerization is carried out, and the reduced-pressure polymerization reaction is a condensation reaction , the moisture produced in the process of reduced pressure polymerization is discharged from the top of the reduced pressure polymerizer, and passed into the pressure polymerization for continuous reaction;

Preferably, the decompression polymerization utilizes negative pressure vacuum dehydration;

Preferably, the material is subjected to condensation reaction for a residence time of 2.5-3h.
The nylon 6 production technique of claim 1, wherein the extraction section uses steam as a power source;

Preferably, the steam is 1.0MPa steam;

Preferably, 1.0MPa steam is used as the first-stage heat medium of the three-effect evaporation, the steam evaporated from the first effect is used as the heat medium of the second-effect evaporation, the evaporation from the second-effect evaporation is used as the heat medium of the third-effect evaporation, and the steam evaporated by the three-effect evaporation is used as the heat medium of the third-effect evaporation The gas phase after the separation of spent gas and liquid is preheated to the extraction water, and the condensate is used to heat the fresh caprolactam raw material, and then it goes to the ammonium sulfate plant to be the refrigerant for ammonium sulfate crystallization.
A system for realizing the nylon 6 production process according to any one of claims 1-7, characterized in that it comprises a pressurized polymerizer, a decompression polymerizer, a pelletizer, an extraction tower, and the extraction tower connected in sequence. The upper outlet is connected to the evaporation device, and the lower outlet is communicated with the packaging section through a gas-phase conveying pipeline; the solution discharged from the decompression polymerizer is also passed into the evaporation device.
The system of nylon 6 production process according to claim 8, wherein the extraction tower is connected with a three-effect evaporation device, and the triple-effect evaporation device is a device in which three groups of evaporators and reboilers are connected in series;

Preferably, the upper part of the extraction tower is connected with a three-effect evaporation device, and the bottom part is connected with a gas-liquid separator through a hot water heat exchanger, and the liquid phase of the gas-liquid separator is a caprolactam discharge port.
The product obtained by the system of the nylon 6 production process described in any one of claims 1-7 or the nylon 6 production process described in claim 8 or 9.