Pre-polymerization reactor for polyamide polymer production

Abstract

The utility model relates to a prepolymerization reactor for polyamide polymer production, and belongs to the technical field of polyamide polymer production equipment. The prepolymerization reactor comprises a reaction tower, a feeding device is arranged at the top end of the reaction tower, a discharging opening is formed in the bottom end of the reaction tower, a plurality of layers of circular tower trays are arranged in the reaction tower in the axial direction, a stirring shaft is arranged along the axis, stirring blades are fixedly installed on the stirring shaft corresponding to each layer of circular tower tray, and the stirring blades are arranged on the stirring shaft. A plurality of vertically-through air holes are formed in each layer of circular tower tray, a through liquid chute is further formed in each circular tower tray in the radial direction, an air inlet is formed in the bottom of the reaction tower, and an air outlet is formed in the top of the reaction tower. The prepolymerization reactor designed by the utility model is beneficial to timely discharge of prepolymerization reaction heat and small molecule byproducts, and the quality of reactant polymers is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of polyamide polymer production equipment, and particularly relates to a prepolymerization reactor for polyamide polymer production. Background Art

[0002] Due to its excellent physical and mechanical properties and chemical stability, polyamide polymers play a huge role in the development of various industrial applications such as optical fiber cables, bulletproof protection, rubber skeletons, friction seals, and composite materials. In industrial production, low-temperature solution polycondensation is usually used for synthesis. First, terephthaloyl chloride (TPC) and p-phenylenediamine (PPD) are subjected to a prepolymerization reaction in a composite system of solvent N-methylpyrrolidone (NMP) and co-solvent calcium chloride, and then the prepolymer is sent into a twin-screw extruder for further reaction to obtain polyamide resin. Since TPC is very active and the polycondensation reaction with PPD is extremely fast, once the monomers come into contact, the reaction can occur, and a large amount of heat is released in a short time. If the temperature at the initial stage of the reaction cannot be controlled well, it will cause premature gelation of the reaction system, hinder the growth of molecular chains, and reduce the quality of PPTA resin.

[0003] At present, the prepolymerization reactors commonly used in industrial production are generally reaction kettles or twin-screw extruders. Reaction kettles are generally closed and operated intermittently. By agitating with a stirring paddle, the concentration distribution gradient of the reaction monomers in the reaction system is balanced, and the small-molecule by-products generated by the reaction are discharged from the reaction system by means of vacuum pumping. This method not only has low production efficiency, but also as the reaction progresses, the mixing effect of the reaction monomers becomes poor after the viscosity of the reaction system increases, and the small-molecule by-products generated by the reaction are not easily discharged, thus affecting the quality of PPTA resin. The twin-screw extruder can achieve continuous production, but its special groove structure and the heat transfer method of the external jacket refrigerant are not conducive to taking away the heat generated inside the reactants in time. At the same time, the shearing action of the screw will also input more heat to the reactants, forming an obvious temperature gradient in the screw groove, which not only increases the energy consumption of the device, but also affects the performance of the polymerization product. Summary of the Invention

[0004] To solve the problems in the prior art, the utility model patent designs a prepolymerization reactor for polyamide polymer production to solve the problems of poor heat dissipation capacity of the prepolymerization reactor, poor discharge effect of reaction small-molecule by-products, and affecting the quality of the polymerization product.

[0005] The technical solution adopted by the present utility model is as follows: The prepolymerization reactor includes a reaction tower. A feeding device is arranged at the top end of the reaction tower, and a discharging port is opened at the bottom end. A plurality of layers of circular trays are arranged axially in the reaction tower, and a stirring shaft is arranged along the axis. Stirring blades are fixedly installed on the stirring shaft corresponding to each layer of circular tray. Through holes are opened on each layer of circular tray and penetrate up and down. An air inlet is opened at the bottom of the reaction tower, and an air outlet is opened at the top.

[0006] Further, a plurality of air holes penetrating up and down are opened on each layer of circular tray of the reaction tower, and a through-flow liquid groove is also opened along the radial direction on the circular tray.

[0007] Further, the liquid flow grooves of each layer of circular trays of the reaction tower are staggered by 30° circumferentially from top to bottom in sequence.

[0008] Further, the stirring blade is a cross-shaped four-blade scraper, and the four-blade scraper is arranged close to the upper side of the circular tray.

[0009] Further, the bottom edges of three of the four blades of the four-blade scraper are serrated, and the other blade is a complete rectangular scraper.

[0010] Further, when the four-blade scraper is installed, the rectangular scraper is located at the clockwise circumferential rear side of the liquid flow groove of the upper-layer circular tray.

[0011] Further, the feeding device includes a TPC reaction liquid buffer tank and a PPDA reaction liquid buffer tank. The TPC reaction liquid buffer tank and the PPDA reaction liquid buffer tank are respectively connected to a metering pump and an atomizing nozzle through pipelines. The atomizing nozzles of the two are arranged at the top of the reaction tower, and the spray ports are arranged opposite to each other.

[0012] Further, the circular tray is of a hollow structure, and a cavity is arranged inside. Temperature control gas inlets and temperature control gas outlets are respectively arranged at the symmetric two ends of the bottom side of the circular tray.

[0013] Further, the atomizing nozzle is a two-fluid nozzle. A high-pressure gas source is connected to the feed pipeline of the atomizing nozzle. The high-pressure gas source is one or more of nitrogen, argon, helium or CO2. The TPC reaction liquid buffer tank and the PPDA reaction liquid buffer tank are respectively provided with cooling jackets, and a circulating cooling medium is passed through the cooling jackets.

[0014] Further, the air inlet and the air outlet of the reaction tower are connected through a pipeline of a protective gas recycling system.

[0015] Compared with the prior art, the improvement of a prepolymerization reactor for polyamide polymer production designed by the present utility model patent lies in:

[0016] First, a reaction solution buffer tank is set in the reactor. The metering pump is used to feed the reaction liquid into the reaction tower at a designed ratio in the way of liquid spray feeding, which avoids the aggregation of reactants and uneven concentration distribution caused by solid feeding, and at the same time ensures the uniformity and stability of the ratio between reaction monomers, and the materials are in full contact and mixing; moreover, cooling jackets are set in the reaction solution buffer tanks, and cooling media are passed through them to facilitate the control of the temperature of each reaction liquid.

[0017] Second, the atomizing nozzle of the reactor adopts a two-fluid nozzle, which can spray the protective gas and the reaction liquid into the reaction tower after mixing, improving the atomization effect while facilitating the control of the ratio of reaction monomers and further controlling the reaction temperature.

[0018] Third, an air inlet is opened at the bottom of the reaction tower for introducing low-temperature protective gas, which can timely carry away the small-molecule by-products and reaction heat generated by the reaction, control the reaction temperature, and promote the forward progress of the reaction; at the same time, the protective gas flowing from bottom to top can slow down the falling speed of the materials, and to a certain extent, extend the residence time of the materials in the reactor, which is beneficial to increasing the molecular weight of the prepolymer.

[0019] Fourth, liquid flow grooves are set on the circular trays of each layer in the reaction tower, and the liquid flow grooves of the circular trays of different layers are arranged in a staggered manner, which can effectively extend the falling path and residence time of the reaction materials, and is beneficial to the full reaction of the reaction materials; a number of air holes evenly arranged on the trays can increase the contact area between the reaction materials and the low-temperature protective gas, strengthen mass transfer and heat transfer, and at the same time, the bubbles bulging out can also play a certain role in mixing and disturbing, facilitating the uniform mixing of reaction monomers; moreover, the circular trays adopt a hollow structure, and temperature control gas inlets and outlets are set at the bottom, which can more accurately control the temperature of the trays and then accurately control the temperature of the reaction system.

[0020] Fifth, four-blade scrapers are set on the upper side of each layer of trays in the reaction tower. Driven by the stirring shaft, the materials on the trays are stirred - formed into a film - stirred again by three serrated scrapers, so that the materials form a uniform film on the tray surface, increasing the contact area between the reaction materials and the low-temperature protective gas, and at the same time facilitating the timely discharge of small-molecule by-products. Then, the fourth rectangular scraper scrapes up the liquid film on the tray surface, making it enter the lower tray through the liquid flow groove, ensuring that no materials adhere to the tray surface and avoiding the influence of overlong residence time and excessive reaction of the materials on the product quality. Description of the Drawings

[0021] Figure 1 It is a schematic structural diagram of a prepolymerization reactor for polyamide polymer production.

[0022] Figure 2 It is a schematic structural diagram of the circular tray and stirring shaft of a prepolymerization reactor for polyamide polymer production.

[0023] Figure 3 It is a schematic structural diagram of a four - blade scraper for a prepolymerization reactor used in the production of polyamide polymers.

[0024] In the figure, 1 is the reaction tower, 2 is the circular tray, 3 is the stirring shaft, 11 is the air inlet, 12 is the air outlet, 13 is the discharge port, 21 is the air hole, 22 is the liquid flow tank, 31 is the stirring motor, 32 is the four - blade scraper, 321 is the serrated scraper, 322 is the rectangular scraper, 41 is the TPC reaction liquid buffer tank, 42 is the PPDA reaction liquid buffer tank, 43 is the atomizing nozzle, 5 is the protective gas treatment system, 51 is the circulating fan, 52 is the temperature - controlled gas inlet pipeline, 53 is the temperature - controlled gas outlet pipeline. Specific embodiments

[0025] The following further describes the present utility model in conjunction with the attached drawings and specific embodiments. The technical solutions in the embodiments of the present utility model are clearly and completely described. The described embodiments are only a part of the embodiments of the present invention, rather than all of them. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0026] As Figure 1 、 2 As shown in FIGS. 16, 17, and 3, an embodiment of a prepolymerization reactor for the production of polyamide polymers is designed in the patent of the present utility model. In this embodiment, the prepolymerization reactor includes a reaction tower 1. The top of the reaction tower 1 is provided with a feeding device, and the bottom is provided with a discharge port 13. A rotary discharge valve is installed at the discharge port 13. Inside the reaction tower 1, multiple layers of circular trays 2 are arranged axially along the axis, and a stirring shaft 3 is arranged along the axis. An air inlet 11 is opened at the bottom of the reaction tower 1, and an air outlet 12 is opened at the top. The air inlet 11 and the air outlet 12 are connected by a pipeline of the protective gas recycling system.

[0027] The feeding device includes a TPC reaction liquid buffer tank 41 and a PPDA reaction liquid buffer tank 42. The TPC reaction liquid buffer tank 41 and the PPDA reaction liquid buffer tank 42 are respectively provided with cooling jackets, and a circulating cooling medium is passed through the cooling jackets to maintain the temperature in the reaction liquid buffer tank at - 10~10°C. At the same time, protective gas is also passed through the reaction liquid buffer tanks. The TPC reaction liquid buffer tank 41 and the PPDA reaction liquid buffer tank 42 are respectively connected with metering pumps and atomizing nozzles 43. The atomizing nozzles 43 of the two are arranged at the top of the reaction tower, and the spray ports are arranged opposite to each other, avoiding the stirring shaft 3 inside the reaction tower 1 when setting. The atomizing nozzle 43 is a two - fluid nozzle, and a high - pressure protective gas source is connected to its feed pipeline. The protective gas source can be selected from one or several of nitrogen, argon, helium, or CO2.

[0028] On each layer of the circular tray 2 in the reaction tower 1, a number of vertically penetrating air holes 21 are evenly distributed, and a radially penetrating liquid flow groove 22 is also provided on the circular tray 2. The liquid flow grooves 22 of each layer of circular trays 2 in the reaction tower 1 are offset by 30° circumferentially from top to bottom in sequence. In addition, the circular tray 2 is a hollow structure with a cavity inside, and a temperature control gas inlet and a temperature control gas outlet are respectively provided at both symmetric ends of the bottom side of the circular tray 2.

[0029] The top end of the stirring shaft 3 is connected with a stirring motor 31, and the stirring motor 31 is installed and fixed at the center of the top of the reaction tower 1. The stirring shaft 3 sequentially passes through the centers of each layer of circular trays 2 and is connected thereto through a sealed bearing, and a stirring blade is fixedly installed thereon corresponding to each layer of circular trays 2. The stirring blade is a four-blade scraper 32 in a cross shape, and the four-blade scraper 32 is arranged closely against the upper side of the circular tray 2 and is fixedly connected to the stirring shaft 3 through a clamp at the center. Three of the four blades of the four-blade scraper 32 are serrated scrapers 321 with serrated bottoms, and the other blade is a complete rectangular scraper 322. The four-blade scraper 32 rotates clockwise under the drive of the stirring motor 31, and when installed, its rectangular scraper 322 is located at the clockwise circumferential rear side of the liquid flow groove 22 of the upper-layer circular tray 2. So as to ensure that the materials falling on each layer of circular tray 2 are successively agitated into a film by the 3 serrated scrapers 321 and then scraped up and pushed to the liquid flow groove 22 by the rectangular scraper 322.

[0030] The protective gas recycling system includes a protective gas treatment system 5 and a circulation fan 51 connected by pipelines. The protective gas treatment system 5 includes an alkali washing tank, a dryer, a gas buffer tank and a refrigeration unit connected by pipelines in sequence. The air inlet end pipeline of the alkali washing tank is butted against the air outlet 12 of the reaction tower 1, the air outlet end of the refrigeration unit is butted against the circulation fan 51, and the air outlet end pipeline of the circulation fan 51 is butted against the air inlet 11 of the reaction tower 1. In addition, the air outlet end of the circulation fan 51 is butted against the temperature control gas inlet of each layer of circular trays 2 through a branched temperature control gas inlet pipeline 52, and the temperature control gas outlet of each layer of circular trays 2 is butted against the air inlet end pipeline of the alkali washing tank through a temperature control gas outlet pipeline 53. The air inlet end of the refrigeration unit is additionally connected to a protective gas source through a protective gas supply pipeline, and the protective gas source can be selected from one or more of nitrogen, argon, helium or CO2.

[0031] When the pre-polymerization reactor for producing polyamide polymers disclosed in the utility model patent is in production, its technological steps are as follows:

[0032] (1)Reaction solution preparation: Dehydrate the N-methylpyrrolidone solvent used in production to ensure that the water content is below 100 ppm. Then dissolve anhydrous calcium chloride in N-methylpyrrolidone to obtain a composite solvent. Under the protection of an inert gas, add p-phenylenediamine and terephthaloyl chloride monomers to the composite solvent respectively according to the calculated ratio, and continuously stir for 15 - 20 minutes to uniformly dissolve p-phenylenediamine and terephthaloyl chloride in the mixed solution, obtaining NMP / CaCl2 / PPDA reaction solution and NMP / CaCl2 / TPC reaction solution, and store them in two reaction solution buffer tanks respectively. Control the temperature of the reaction solution at -10~10°C through the cooling medium in the jacket, and an inert gas is also introduced into the reaction solution buffer tanks.

[0033] (2)Reaction solution feeding: Control the metering pumps to send the p-phenylenediamine reaction solution and terephthaloyl chloride reaction solution into two two-fluid atomizing nozzles arranged oppositely inside the top of the reaction tower respectively according to the calculated ratio, mix them with the introduced low-temperature inert gas and spray out, realizing the atomization, collision and mixing of the reaction solutions in the reaction tower.

[0034] (3)Prepolymerization reaction: At the moment when the two atomized reaction solutions collide, a polymerization reaction occurs, releasing a large amount of reaction heat and acidic small molecule by-products. The reaction solution droplets fall to the first layer of circular tray under the action of gravity. The stirring motor drives the four-blade scraper closely attached to the circular tray to rotate through the stirring shaft. The reaction materials falling on the circular tray are first mixed under the action of the three-blade serrated scraper, and at the same time, a liquid film is formed on the surface of the circular tray under the action of surface tension. After repeating the process of stirring and mixing - film formation three times, under the action of the fourth rectangular scraper, the liquid film on the tray surface is scraped up, pushed into the liquid flow groove of the circular tray, enters the lower circular tray, and falls layer by layer along each layer of circular trays. During the process of the reaction materials falling layer by layer, the four-blade scraper closely attached to each layer of tray will stir and mix the reaction materials three times, further improving the reaction effect. At the same time, the liquid film form not only increases the heat exchange area between the reaction materials and the inert gas, which is beneficial to the control of the reaction system temperature, but also is conducive to the timely removal of the small molecule by-products generated by the reaction, and is beneficial to the increase of the molecular weight of the reaction product.

[0035] (4)Discharge of reaction product: Under the action of gravity, the reaction materials fall to the conical blanking area at the bottom of the reaction tower, and are discharged from the reaction tower through a rotary discharge valve and enter the next process.

[0036] (5) Circulation of protective gas: After being cooled by the refrigeration unit, the protective gas is controlled at a temperature of -10~0℃ and transported by the circulating fan. It is sent into the reaction tower from the air inlet of the reaction tower, passes through the pores of the circular tower plate and rises layer by layer, and conducts mass and heat transfer with the liquid film of the reaction materials on the surface of the circular tower plate. A screen is provided at the air inlet of the reaction tower to prevent the reaction materials from accumulating at the air inlet. The protective gas, which is continuously heated up along the tower body, is discharged from the air outlet at the top of the reaction tower with the acidic small molecular by-products produced by the reaction and enters the protective gas treatment system. A liquid mist demister is provided at the air outlet to prevent the reaction liquid from being carried away by the protective gas flow and affecting the monomer ratio of the reaction. The other route is divided into multiple strands along the temperature-controlled gas inlet pipeline, which enter the cavity inside the circular tower plate from the temperature-controlled gas inlet at the bottom of each circular tower plate, and are discharged from the temperature-controlled gas outlet on the other side. After merging with the protective gas discharged from the outlet of the reaction tower through the temperature-controlled gas outlet pipeline, they enter the protective gas treatment system together, first pass through the alkaline washing tank to remove the acidic small molecule by-products contained therein, and then enter the dryer to remove the moisture entrained in the protective gas. The purified protective gas enters the gas buffer tank, and then is sent to the reaction tower by the circulating fan after being cooled by the refrigeration unit, completing the closed-loop circulation of the protective gas.

[0037] The above contents are only preferred embodiments of the present invention and cannot be used to limit the scope of implementation of the present invention. That is, any simple equivalent changes and modifications made according to the claims and description of the present invention are still within the scope of the present invention.

Claims

1. A prepolymerization reactor for polyamide polymer production, characterized in that: The prepolymerization reactor comprises a reaction tower, wherein a feeding device is arranged at the top of the reaction tower, and a discharge port is opened at the bottom. A plurality of layers of circular tower plates are arranged axially in the reaction tower, and a stirring shaft is arranged along the axis. A stirring blade is fixedly installed on the stirring shaft corresponding to each layer of circular tower plates, and each layer of circular tower plates is provided with holes and grooves that pass through from top to bottom. An air inlet is opened at the bottom of the reaction tower, and an air outlet is opened at the top.

2. A prepolymerization reactor for polyamide polymer production according to claim 1, characterized in that: A plurality of vertically penetrating air holes are provided on each circular tower plate of the reaction tower, and a penetrating liquid flow groove is also provided on the circular tower plate in a radial direction.

3. A prepolymerization reactor for polyamide polymer production according to claim 2, characterized in that: The liquid flow grooves of each layer of the circular tower plate of the reaction tower are staggered by 30 degrees in the circumferential direction from top to bottom.

4. A prepolymerization reactor for polyamide polymer production according to claim 3, characterized in that: The stirring blade is a cross-shaped four-blade scraper, and the four-blade scraper is arranged close to the upper side of the circular tower plate.

5. A prepolymerization reactor for polyamide polymer production according to claim 4, characterized in that: The bottom edges of three blades of the four-blade scraper are serrated, and the other blade is a complete rectangular scraper.

6. A prepolymerization reactor for polyamide polymer production according to claim 5, characterized in that: When the four-blade scraper is installed, the rectangular scraper is located at the clockwise circumferential rear side of the liquid flow groove of the upper circular tower plate.

7. A prepolymerization reactor for polyamide polymer production according to claim 6, characterized in that: The feeding device includes a TPC reaction liquid buffer tank and a PPDA reaction liquid buffer tank, and the TPC reaction liquid buffer tank and the PPDA reaction liquid buffer tank are respectively connected to a metering pump and an atomizing nozzle by pipelines. The atomizing nozzles of the two are arranged at the top of the reaction tower, and the nozzles are arranged relative to each other.

8. A prepolymerization reactor for polyamide polymer production according to claim 7, characterized in that: The circular tower plate is a hollow structure with a cavity arranged inside. A temperature-controlled gas inlet and a temperature-controlled gas outlet are respectively arranged at two symmetrical ends of the bottom side of the circular tower plate.

9. A prepolymerization reactor for polyamide polymer production according to claim 8, characterized in that: The atomizing nozzle is a two-fluid nozzle, and a high-pressure gas source is connected to the feed pipeline of the atomizing nozzle. The high-pressure gas source is one or more of nitrogen, argon, helium or CO2. The TPC reaction liquid buffer tank and the PPDA reaction liquid buffer tank are respectively provided with cooling interlayers, and a circulating cooling medium is passed through the cooling interlayers.

10. A prepolymerization reactor for polyamide polymer production according to claim 1, characterized in that: The air inlet and the air outlet of the reaction tower are connected through a protective gas recycling system pipeline.

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