Semi-continuous nylon polymerization device

Abstract

The invention discloses a semi-continuous nylon polymerization device, which overcomes the defects of batch polymerization and continuous polymerization at present, keeps the advantages of the batch polymerization and continuous polymerization at the same time, and comprises a monomer preheater, two or more prepolymerization reactors, a continuous melt heat exchanger, a continuous melt de-ashing flash evaporator and a continuous post-polymerizer, the two or more prepolymerization reaction kettles are sequentially communicated, the monomer preheater is communicated with the first prepolymerization reaction kettle, the last prepolymerization reaction kettle is communicated with the melt heat exchanger, the melt heat exchanger is communicated with the melt deliming flash evaporator, the melt deliming flash evaporator is communicated with the continuous post-polymerizer, and the continuous post-polymerizer is communicated with the continuous post-polymerizer. A concentration kettle is arranged between the monomer preheater and the first prepolymerization reaction kettle, the prepolymerization reaction kettle adopts a jacketed heating pressure-resistant reaction kettle, and feeding and discharging of the first prepolymerization reaction kettle adopt intermittent operation; and the prepolymerization kettle starting from the second prepolymerization kettle adopts intermittent feeding and continuous discharging, and is widely applied to the field of nylon production.

Description

Technical Field

[0001] The invention relates to a semi-continuous nylon polymerization device, belonging to the technical field of nylon production. Background Art

[0002] The existing nylon production equipment mainly includes two types: intermittent polymerization and continuous polymerization.

[0003] The intermittent polymerization process is to add nylon monomer, water and related additives into an intermittent reactor, and then the process of heating, pressure maintenance, pressure relief and post-polymerization are all carried out in the reactor. At present, intermittent polymerization is mostly used in small-scale production of nylon products. The main reason is that the intermittent polymerization equipment is simple to operate and can produce most nylon resins, including nylon 6, energy 6, long carbon chain nylon, high-temperature nylon and nylon elastomers, etc. The production variety is easy to change, the reactor is easy to clean, and the cleaning time and cycle are short. The disadvantage is that the heat exchange area of ​​the reactor is small, and the time required for the material in the reactor to release pressure and heat up from high-pressure pre-polymerization to post-polymerization is very long, especially for high-melting point polymers such as high-temperature nylon. It is particularly difficult to reach a material temperature higher than its melting point. In addition, changes in the liquid level of the reactor are prone to produce black spots, and the quality of each reactor batch is more or less different; the single-line production capacity is small.

[0004] The continuous polymerization process is that the nylon monomer passes through the preheater, prepolymerization reactor, flash evaporator and post-polymerizer and other process equipment, and then is pelletized and dried. The process characteristics are convenient process automation control, stable process conditions and reactor liquid level, stable slice quality indicators, good whiteness, and few black spots; the spinning grade slice titanium dioxide is well dispersed and the slice spinnability is good; the single line production capacity is large. The disadvantage is that the large single line output makes it inconvenient to change the product variety production and the replacement cost is high; the reactor is also inconvenient to clean, the cleaning cycle is long, and the operation is inconvenient.

[0005] The semi-continuous core of the Chinese patent "A semi-continuous nylon 66 polymerization device" with publication number CN207108892U and the semi-continuous nylon 66 polymerization device with publication number CN207102570U is obtained through the primary and secondary concentration kettles, while the polymerization kettle is still operated intermittently, the pressure relief of the reactor and the post-polymerization heating time are relatively long, and the production efficiency is still not high. Summary of the invention

[0006] The present invention overcomes the shortcomings of the prior art and provides a semi-continuous nylon polymerization device, which overcomes the disadvantages of the above-mentioned intermittent polymerization and continuous polymerization and maintains the advantages of the two.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is: a semi-continuous nylon polymerization device, comprising a monomer preheater, two or more prepolymerization reactors, a continuous melt heat exchanger, a continuous melt deashing flash evaporator and a continuous post-polymerizer, the two or more prepolymerization reactors are connected in sequence, the monomer preheater is connected to the first prepolymerization reactor, the last prepolymerization reactor is connected to the melt heat exchanger, the melt heat exchanger is connected to the melt deashing flash evaporator, the melt deashing flash evaporator is connected to the continuous post-polymerizer, a concentrating kettle is arranged between the monomer preheater and the first prepolymerization reactor, the concentrating kettle is used to remove excess water in the monomer, the prepolymerization reactor adopts a jacketed heating pressure-resistant reactor, the first prepolymerization reactor is fed and discharged by intermittent operation; the prepolymerization reactors starting from the second prepolymerization reactor adopt intermittent feeding and continuous discharging.

[0008] Furthermore, the heating medium of the jacketed heating pressure-resistant reactor includes biphenyl, biphenyl ether, heat-conducting oil, and heat-conducting salt bath.

[0009] Furthermore, the continuous post-polymerizer includes two types of reactors: vertical and horizontal.

[0010] Furthermore, the melt heat exchanger adopts a shell-and-tube heat exchanger or a plate heat exchanger.

[0011] Furthermore, the continuous post-polymerizer adopts a continuous vertical polymerizer or a continuous horizontal polymerizer, the continuous horizontal polymerizer includes a screw-type reaction extruder, and the continuous post-polymerizer is sequentially connected with pelletizing, dehydration and drying, and packaging.

[0012] Furthermore, the monomer preheater heats the incoming monomer to the target temperature, removes excess water through the concentrator, and then sequentially enters the first prepolymerization reactor to the last prepolymerization reactor. The prepolymerization reactor adopts a jacketed heating pressure-resistant reactor. The temperature and pressure of the prepolymerization reactor are set according to the requirements of the target reactant. The prepolymerization reactor can be stirred or not stirred. The volume of the prepolymerization reactor can be designed accordingly according to the production capacity requirements. The feeding and discharging of the first prepolymerization reactor are both operated intermittently; the feeding from the second prepolymerization reactor to the last prepolymerization reactor are operated intermittently and the discharging is continuous; The melt heat exchanger can quickly increase the melt temperature to the target value in a short time. The melt deashing flash evaporator can quickly convert small molecular substances in the melt, mainly water, into gas and discharge it, so that the molecular weight of the melt increases rapidly. The volatilization of water will take away a large amount of heat. It must be ensured that the heat taken away by the volatilization of water causes the temperature of the melt to drop to still be above the melting point of the material. The continuous post-polymerizer is sequentially connected to pelletizing, dehydration and drying, and packaging to obtain the finished product.

[0013] Compared with the prior art, the present invention has the following beneficial effects: the prepolymerization feed of the present invention adopts an intermittent method, the postpolymerization adopts a continuous polymerization method, the conversion from intermittent polymerization to continuous polymerization starts from the discharge of the second prepolymerization kettle or even the third and fourth prepolymerization kettles, and then rapidly and continuously flashes for deashing, continuously postpolymerizes, and continuously pelletizes, dehydrates, dries and packages. It has the advantages of simple intermittent polymerization process equipment, convenient product replacement, convenient reactor cleaning, etc., as well as stable postpolymerization liquid level, good product whiteness, few black spots, and large single-line production capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The present invention will be further described below in conjunction with the accompanying drawings.

[0015] Figure 1 It is a schematic diagram of the framework structure of the present invention.

[0016] Figure 2 The process flow of the semi-continuous nylon polymerization device of the present invention is as follows Figure 1 Figure 3 The process flow of the semi-continuous nylon polymerization device of the present invention is as follows Figure 2 In the figure: M1 is monomer, M2 is polymer slice, R1 is monomer preheater, R2 is concentration kettle, R3a and R3b are prepolymerization kettles, R4 is melt heat exchanger, R5 is melt deashing flash evaporator, R6 is continuous post-polymerization reactor ( Figure 2 R6 is a horizontal continuous post-polymerizer. Figure 3 Among them, R6 is a vertical continuous post-polymerizer and R7 is a pelletizer. DETAILED DESCRIPTION

[0017] The present invention will be further described below in conjunction with specific embodiments.

[0018] like Figure 1As shown, the present invention is a semi-continuous nylon polymerization device, comprising a monomer preheater, two or more prepolymerization reactors, a continuous melt heat exchanger, a continuous melt deashing flash evaporator and a continuous post-polymerizer, the two or more prepolymerization reactors are connected in sequence, the monomer preheater is connected to the first prepolymerization reactor, the first prepolymerization reactor is fed and discharged by intermittent operation; the prepolymerization reactors starting from the second prepolymerization reactor are fed intermittently and discharged continuously, the last prepolymerization reactor is connected to the melt heat exchanger, the melt heat exchanger is a shell and tube heat exchanger or a plate heat exchanger, the melt heat exchanger and the melt deashing flash evaporator are connected by a continuous melt heat exchanger, and the melt heat exchanger is connected to the melt deashing flash evaporator. The melt deashing flash evaporator is connected to a continuous post-polymerizer, the continuous post-polymerizer includes two types of reactors, a vertical reactor and a horizontal reactor, the continuous post-polymerizer adopts a continuous vertical polymerizer or a continuous horizontal polymerizer, the continuous horizontal polymerizer includes a screw reaction extruder, and the continuous post-polymerizer is sequentially connected with pelletizing, dehydration and drying, and packaging, a concentrating kettle is arranged between the monomer preheater and the first pre-polymerization reactor, the concentrating kettle is used to remove excess water in the monomer, the pre-polymerization reactor adopts a jacketed heating pressure-resistant reactor, and the heating medium of the jacketed heating pressure-resistant reactor includes biphenyl, biphenyl ether, heat transfer oil, and heat transfer salt bath.

[0019] The workflow of the present invention is as follows: Monomer—monomer preheater—concentration kettle—prepolymerization kettle 1, 2...—melt heat exchanger—melt deashing flash evaporator—continuous post-polymerizer—granulation—dehydration and drying—packaging.

[0020] The monomer reaches the target temperature through the preheater, removes excess water through the concentrator, and then enters the prepolymerization reactor (first, second...). The prepolymerization reactor can be a jacketed heating pressure reactor. The temperature and pressure of the prepolymerization reactor are set according to the requirements of the target reactant. The prepolymerization reactor can be stirred or not. The volume of the prepolymerization reactor can be designed accordingly according to the production capacity requirements. The first prepolymerization reactor uses intermittent feeding and discharging; the second (or third...) prepolymerization reactor can use intermittent feeding and continuous discharging, which is the key to changing the polymerization process from intermittent polymerization to continuous polymerization. The jacketed heating medium of the reactor can be biphenyl, biphenyl ether or other heat transfer oil, heat transfer salt bath, etc.

[0021] Melt heat exchangers generally use shell-and-tube heat exchangers or plate heat exchangers, etc., which have a large heat exchange area and can quickly raise the melt temperature to the target value in a short time. The heat exchange medium can be biphenyl, biphenyl ether or other heat transfer oils, heat transfer salt baths, etc.

[0022] The melt deashing flash evaporator can quickly turn the small molecular substances in the melt, mainly water, into gaseous state and discharge them, so that the molecular weight of the melt increases rapidly. The efficiency and effect of deashing are very important for the increase of the molecular weight of the melt and the production efficiency and product quality of the post-polymerization. The volatilization of water will take away a lot of heat. It is necessary to ensure that the heat taken away by the volatilization of water causes the temperature of the melt to drop to still be above the melting point of the material.

[0023] The continuous post-polymerizer can be a continuous vertical polymerizer or a continuous horizontal polymerizer. Continuous pelletizing, dehydration, drying and packaging, this patent has the advantages of simple intermittent polymerization process equipment, convenient product replacement, easy cleaning of the reactor, etc., as well as stable post-polymerization liquid level, good product whiteness, few black spots, and large single-line production capacity.

[0024] The present invention can be used for the polymerization of various nylons, including the polymerization production of aliphatic chain nylons such as nylon 6, nylon 66, nylon 56, etc., long carbon chain nylons such as nylon 610, nylon 612, nylon 1010, nylon 1212, nylon 1012, nylon 11, nylon 12, etc., and high temperature nylons such as nylon 46, nylon 5T, nylon 6T, nylon 9T, nylon 10T and nylon 12T.

[0025] The following is a detailed explanation taking nylon 66 polymerization as an example.

[0026] like Figure 2 and Figure 3 As shown, the nylon 66 salt solution M1 with a concentration of 30%-65% passes through the preheater R1 to reach the target temperature (130℃-200℃); a part of the water is removed through the concentration kettle R2, and the concentration reaches 65%-85%. The temperature of the concentration kettle R2 is 130℃-200℃, and the pressure is 0.4MPa-1.0MPa; then it enters the prepolymerization kettle R3a and R3b. These prepolymerization kettles can adopt jacketed heating pressure-resistant reactors. The working temperature of the prepolymerization reactor is 150℃-300℃, the working pressure is 0.1MPa-10.0MPa, and the working time is 0.5 hour-10.0 hours; the prepolymerization reactor can be stirred or not, and the volume of the reactor can be designed accordingly according to the production capacity requirements. The first prepolymerization reactor adopts intermittent operation for feeding and discharging; the second (or third...) prepolymerization reactor can adopt intermittent feeding and continuous discharging, which is the key to change the polymerization process from intermittent polymerization to continuous polymerization (any method involving intermittent feeding and continuous discharging of prepolymerization reactors violates this patent). The jacketed heating medium of the reactor can adopt biphenyl, biphenyl ether or other heat-conducting oil, heat-conducting salt bath, etc.

[0027] The melt is continuously discharged from the second (or third...) prepolymerization reactor R3b and enters the melt heat exchanger R4 through the melt pump. The melt heat exchanger R4 generally adopts a shell-and-tube heat exchanger or a plate heat exchanger, etc., which has a large heat exchange area and can quickly increase the melt temperature to the target value of 270℃-310℃ in a short time. The melt heat exchange time is 0.1 minutes-30 minutes. The heat exchange medium can be biphenyl, biphenyl ether or other heat transfer oil, heat transfer salt bath, etc.

[0028] After the melt at a temperature of 270℃-310℃ comes out of the heat exchanger R4, it continuously enters the melt deashing flash evaporator R5. The melt pressure is normal pressure. The small molecular substances in the melt, mainly water, quickly turn into gaseous state and are discharged, which makes the molecular weight of the melt increase rapidly. The efficiency and effect of deashing are very important for the increase of melt molecular weight and the production efficiency and product quality of post-polymerization. The volatilization of water will take away a lot of heat. It is necessary to ensure that the heat taken away by the volatilization of water causes the melt temperature to drop and still be above the melting point of the material. The melt temperature control range is 270℃-300℃, and the flashing time of the melt in the flash evaporator R5 is 0.1 minutes-30 minutes.

[0029] After the melt comes out of the melt deashing flash evaporator, the melt temperature is controlled within the range of 270℃-300℃ and enters the continuous post-polymerizer R6. Figure 2 It is a continuous vertical polymerizer. Figure 3 It is a continuous horizontal polymerizer. The melt temperature in the post-polymerizer is the same as or slightly higher than the melt temperature coming out of the flash evaporator, and is controlled at 275°C - 300°C. The post-polymerization time is 5 minutes - 2 hours.

[0030] After the melt comes out of the continuous post-polymerizer, it passes through the melt valve and melt metering pump, and enters the pelletizer R7 for pelletizing into slices M2, and then dehydrated, dried and packaged. The obtained nylon 66 slices M2 have a melting point of 260-265℃, a relative viscosity of 2.3-3.0 (tested with 93% concentrated sulfuric acid), an end amino content of 15-75meq. / kg, a yellow index of <1.0, and a density of 1.14kg / dm3.

[0031] The present invention has the advantages of simple intermittent polymerization process equipment, convenient product replacement, convenient reaction kettle cleaning, etc., as well as stable post-polymerization liquid level, good product whiteness, few black spots, and large single-line production capacity.

[0032] The embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

Claims

1. A semi-continuous nylon polymerization device, characterized in that: It includes a monomer preheater, two or more prepolymerization reactors, a continuous melt heat exchanger, a continuous melt deashing flash evaporator and a continuous post-polymerizer. The two or more prepolymerization reactors are connected in sequence. The monomer preheater is connected to the first prepolymerization reactor, and the last prepolymerization reactor is connected to the melt heat exchanger. The melt heat exchanger is connected to the melt deashing flash evaporator, and the melt deashing flash evaporator is connected to the continuous post-polymerizer. A concentrating kettle is arranged between the monomer preheater and the first prepolymerization reactor. The concentrating kettle is used to remove excess water in the monomer. The prepolymerization reactor adopts a jacketed heating pressure-resistant reactor. The feeding and discharging of the first prepolymerization reactor are both intermittently operated; the prepolymerization reactors starting from the second prepolymerization reactor adopt intermittent feeding and continuous discharging.

2. A semi-continuous nylon polymerization device according to claim 1, characterized in that: The heating medium of the jacketed heating pressure-resistant reactor includes biphenyl, biphenyl ether, heat-conducting oil and heat-conducting salt bath.

3. A semi-continuous nylon polymerization device according to claim 1, characterized in that: The continuous post-polymerizer includes two types of reactors: vertical and horizontal.

4. A semi-continuous nylon polymerization device according to claim 1, characterized in that: The melt heat exchanger is a shell-and-tube heat exchanger or a plate heat exchanger.

5. A semi-continuous nylon polymerization device according to claim 1, characterized in that: The continuous post-polymerizer adopts a continuous vertical polymerizer or a continuous horizontal polymerizer. The continuous horizontal polymerizer includes a screw-type reaction extruder, and the continuous post-polymerizer is sequentially connected with pelletizing, dehydration and drying, and packaging.

6. A semi-continuous nylon polymerization device according to claim 5, characterized in that: The monomer preheater heats the incoming monomer to the target temperature, removes excess water through the concentrator, and then sequentially enters the first prepolymerization reactor to the last prepolymerization reactor. The prepolymerization reactor adopts a jacketed heating pressure-resistant reactor. The temperature and pressure of the prepolymerization reactor are set according to the requirements of the target reactant. The prepolymerization reactor can be stirred or not stirred. The volume of the prepolymerization reactor can be designed accordingly according to the production capacity requirements. The feeding and discharging of the first prepolymerization reactor are both operated intermittently; the feeding from the second prepolymerization reactor to the last prepolymerization reactor are operated intermittently and the discharging is continuous; The melt heat exchanger can quickly increase the melt temperature to the target value in a short time. The melt deashing flash evaporator can quickly convert small molecular substances in the melt, mainly water, into gas and discharge it, so that the molecular weight of the melt increases rapidly. The volatilization of water will take away a large amount of heat. It must be ensured that the heat taken away by the volatilization of water causes the temperature of the melt to drop to still be above the melting point of the material. The continuous post-polymerizer is sequentially connected to pelletizing, dehydration and drying, and packaging to obtain the finished product.

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