Novel reaction device for preparing polyglycolic acid

Abstract

The utility model provides a novel reaction device for preparing polyglycolic acid, which comprises a reaction kettle, a condenser, a drying tower and a circulating pump, the reaction kettle comprises a kettle body and a jacket arranged outside the kettle body, the upper part of the kettle body is provided with a feed port, steam is introduced into the jacket, the top end of the kettle body is provided with a stirring motor, an output shaft of the motor is fixedly connected with a stirring paddle, and the stirring paddle is connected with the condenser. The top of the kettle body is connected with the bottom of the condenser through a pipeline, the top end of the condenser is connected with the drying tower through a pipeline, the lower end of the drying tower is provided with a tail gas outlet to form a gas phase loop, the bottom of the kettle body is provided with a discharging pipe, the discharging pipe is connected with a circulating pump, and the output end of the circulating pump is connected to the bottom of the drying tower. The top of the drying tower is connected with the top end of the kettle body to form a liquid phase loop. The condenser is designed, so that raw materials and oligomers separated from a reaction system in the reaction process are condensed and then return to the reaction kettle to continuously participate in the reaction, thereby reducing the loss of the raw materials and intermediate products, improving the product yield and reducing reaction residues.

Description

Technical Field

[0001] The utility model relates to the technical field of polyglycolic acid preparation, in particular to a novel reaction device for preparing polyglycolic acid. Background Art

[0002] Polyglycolic acid (PGA) is the simplest linear aliphatic polyester among polyhydroxyalkanoates. It has good biocompatibility and biodegradability. It plays an important role in the field of medical polymer materials such as drug controlled release, artificial skin and blood vessels, surgical sutures, and fixation of tissues and organs in vivo.

[0003] Polyglycolic acid is the earliest commercialized raw material for the preparation of synthetic surgical sutures. Its synthesis is mainly based on two methods: direct condensation polymerization of glycolic acid and ring-opening polymerization of glycolide. The direct condensation polymerization method is simple to operate, but generally only oligomers with a relative molecular weight of tens to thousands can be obtained. Ring-opening polymerization of glycolide is a common method for obtaining high relative molecular weight PGA, but it also has many difficult to solve problems.

[0004] US Patent No. 5091544A discloses a method of increasing the reaction interface by introducing an inert gas flow to promote the rapid conversion of oligomers into cyclic monomers, and using a water-insoluble non-polar solvent to recover the cyclic monomers from the gas flow, and then further purifying the glycolide to obtain the glycolide and then performing ring-opening polymerization to prepare polyglycolic acid. However, due to the slow generation rate of cyclic dimers and the low glycolide yield, the polyglycolic acid product prepared by this method has high cost and low efficiency. US Patent No. 4727163A discloses a method of preparing glycolide, an upstream raw material of polyglycolic acid, by heating a copolymer of glycolic acid and a high-temperature resistant polyether. Although the high-temperature resistant polyether can be reused by adding glycolic acid for copolymerization multiple times, a large amount of polyether is consumed. At the same time, many side reactions occur in the polymer at high temperature, such as isomerization and carbonization of the polymer, resulting in a large amount of impurities in the obtained glycolide crude product, which is difficult to purify and separate, and the reactor and equipment pipelines are difficult to clean, which reduces the production efficiency of polyglycolic acid. The main problem mentioned above is that the generation reaction control of the intermediate product in the production process of polyglycolic acid is not well solved, such as the timely removal of water generated in the reaction process, serious loss of reaction materials, reaction heat and mass transfer, etc., resulting in the production of products with low molecular weight, low yield, high residue, serious blockage of equipment pipelines, high energy consumption and high cost. Utility Model Content

[0005] In view of the shortcomings of the prior art, the utility model provides a novel reaction device for preparing polyglycolic acid. In order to achieve the above-mentioned purpose, the utility model adopts the following technical solutions:

[0006] A novel reaction device for preparing polyglycolic acid comprises a reactor, a condenser, a drying tower and a circulation pump. The reactor comprises a reactor body and a jacket arranged outside the reactor body. A feed inlet is arranged at the top of the reactor body, steam is passed through the jacket, a stirring motor is installed at the top of the reactor body, a stirring paddle is fixedly connected to the output shaft of the motor, the top of the reactor body is connected to the bottom of the condenser through a pipeline, the top of the condenser is connected to the drying tower through a pipeline, a tail gas outlet is arranged at the lower end of the drying tower to form a gas phase loop, a discharge pipe is arranged at the bottom of the reactor body, the discharge pipe is connected to the circulation pump, the output end of the circulation pump is connected to the bottom of the drying tower, and the top of the drying tower is connected to the top of the reactor body to form a liquid phase loop.

[0007] Furthermore, the body of the reactor is made of polytetrafluoroethylene, polystyrene, 304 stainless steel, glass-lined or ceramic.

[0008] Furthermore, the stirring paddle is tangent to the inner wall of the kettle body, and the blade type of the stirring paddle is frame type, anchor type, turbine type or three-blade backward curved type.

[0009] Furthermore, the condenser is a water-cooled condenser, a water inlet is provided at the bottom of the condenser, a water outlet is provided at the top of the condenser, and the type of the condenser is a folded plate type, a double tube type, a U-shaped tube type, or a sleeve type.

[0010] Furthermore, the drying medium of the drying tower is molecular sieve, resin, silica gel or activated alumina.

[0011] Furthermore, the circulation pump is a centrifugal pump, a mixed flow pump, an axial flow pump, or an electromagnetic pump.

[0012] Compared with the prior art, the utility model has the following beneficial effects:

[0013] 1. The kettle body is made of anti-sticky material, which can greatly reduce the reaction raw materials and products hanging on the wall and reduce the reaction residue;

[0014] 2. The design of the condenser can allow the raw materials and oligomers that escape from the reaction system to condense and return to the reactor to continue the reaction, thereby reducing the loss of raw materials and intermediates, improving product yields, and reducing reaction residues;

[0015] 3. The design of the drying tower replaces the traditional vacuum dehydration device, which greatly avoids the large loss of reaction materials under vacuum conditions, improves the utilization rate of raw materials, and can more quickly and fully remove the water generated by the reaction, thereby increasing the polymerization rate and product molecular weight. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The utility model is further described below in conjunction with the accompanying drawings and embodiments:

[0017] Figure 1 It is a schematic diagram of the structural flow of an embodiment of the utility model.

[0018] In the above drawings: reactor 1, condenser 2, drying tower 3, circulating pump 4, kettle body 5, jacket 6, feed inlet 7, stirring paddle 8, tail gas outlet 9, discharge pipe 10, water inlet 11, water outlet 12, steam inlet 13. DETAILED DESCRIPTION

[0019] The technical solution of the present utility model is further described below in conjunction with the accompanying drawings and embodiments.

[0020] Example 1

[0021] Please refer to Figure 1 As shown, a novel reaction device for preparing polyglycolic acid comprises a reactor 1, a condenser 2, a drying tower 3 and a circulating pump 4. The reactor 1 comprises a reactor body 5 and a jacket 6 arranged outside the reactor body 5. A feed inlet 7 is arranged on the upper part of the reactor body 5. Steam is passed through the jacket 6. A stirring motor is installed at the top of the reactor body 5. A stirring paddle 8 is fixedly connected to the output shaft of the motor. The top of the reactor body 5 is connected to the bottom of the condenser 2 through a pipeline. The top of the condenser 2 is connected to the drying tower 3 through a pipeline. The lower end of the drying tower 3 is provided with an exhaust gas outlet 9 to form a gas phase loop. A discharge pipe 10 is provided at the bottom of the reactor body 5. The discharge pipe 10 is connected to the circulating pump 4. The output end of the circulating pump 4 is connected to the bottom of the drying tower 3. The top of the drying tower 3 is connected to the top of the reactor body 5 to form a liquid phase loop.

[0022] The low-pressure steam in the jacket 6 of the reactor 1 is provided by the workshop boiler, with a pressure of 0.35Mpa. After the product in the reactor 1 meets the requirements, it starts to be discharged to the product packaging area through the discharge port. All external connecting pipelines of the device are insulated. After the reactor 1 is filled with materials, the feed is closed, the steam inlet 13 of the jacket 6 is opened, and heating is started. When the temperature in the kettle body 5 exceeds 80°C, stirring is started, and the temperature is continued to rise to 160°C. After the temperature stabilizes, the reaction is kept warm for 8 hours. At this time, a large amount of liquid condenses and refluxes in the condenser 2. After the reaction is completed, the circulating pump 4 is turned on to start conveying the material in the reactor 1 to the drying tower 3. The material dried in the drying tower 3 is returned to the reactor 1. After 2.5 hours of circulation, the temperature is continued to rise to 220°C. When there is no obvious liquid evaporation in the reactor 1, that is, when there is no liquid condensation and reflux in the condenser 2, the circulation is stopped, the circulating pump 4 is turned off, and the product discharge port is opened to start discharging the product. After testing, the molecular weight of the polyglycolic acid product is 125,000, and the product yield is 85.9%, which meets the product quality requirements.

[0023] Preferably, the body 5 of the reactor 1 is made of polytetrafluoroethylene or polystyrene or 304 stainless steel or glass lining or ceramic. Such materials have good anti-adhesion performance and acid corrosion resistance, can prevent heavy materials from adhering to the reactor 1, avoid coking, and have a good protective effect on acidic substances such as carboxylic acid raw materials and dimers present in the reaction process.

[0024] Preferably, the stirring paddle 8 is tangent to the inner wall of the kettle body 5, and the blade type of the stirring paddle 8 is frame type, anchor type, turbine type, or three-blade backward curved type. Its structure can play a good wall scraping effect and reduce the wall hanging of materials.

[0025] Preferably, the condenser 2 is a water-cooled condenser 2, a water inlet 11 is provided at the lower part of the condenser 2, a water outlet 12 is provided at the upper part, and the type of the condenser 2 is a folded plate type, a double tube type, a U-shaped tube type, or a sleeve type. The shell of the condenser 2 is made of 316L stainless steel, which has fast heat transfer and high heat exchange efficiency, ensuring that the reaction raw materials and intermediate products evaporated during the reaction process can be quickly condensed and refluxed to the reactor 1. The water inlet 11 is connected to the boiler circulating water to save resources. The temperature of the boiler circulating water is controlled at 80-85°C. This cooling temperature can ensure that the low-boiling point reaction materials are condensed into liquid and refluxed to the reactor 1 to continue to participate in the polymerization reaction. The water inlet 11 is located at the lower part of the shell, and the water outlet 12 is located at the upper part of the shell. The boiler circulating water enters from the lower part and exits from the upper part, which improves the condensation effect.

[0026] Preferably, the drying medium of the drying tower 3 is a molecular sieve or a resin or a silica gel or an activated alumina. The tower body is made of high-strength Hastelloy, which has high strength and corrosion resistance, ensuring the high mechanical strength and tolerance of the drying tower 3. The drying tower 3 is equipped with a drying medium such as a molecular sieve or a resin or a silica gel or an activated alumina. The drying medium has a fast water absorption rate and a large water absorption capacity, and can quickly and completely remove the water produced by the reaction, thereby increasing the polymerization reaction rate; the tail gas outlet 9 is located at the lower part of the tower body, and the tail gas inlet is connected to the top of the condenser 2. The tail gas coming out of the top of the condenser 2 is a non-condensable gas with a higher temperature. These high-temperature gases can provide heat for the drying tower 3, so that the drying tower 3 has a certain temperature, prevents the material from solidifying, and saves energy.

[0027] Preferably, the circulation pump 4 is a centrifugal pump, a mixed flow pump, an axial flow pump, or an electromagnetic pump. The circulation pump 4 is a set of two high-temperature and corrosion-resistant high-power centrifugal pumps, mixed flow pumps, axial flow pumps, or electromagnetic pumps to ensure the transportation of materials.

[0028] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the utility model rather than to limit it. Although the utility model has been described in detail with reference to the preferred embodiments, ordinary technicians in the field should understand that the technical solution of the utility model can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the utility model, which should be included in the scope of the claims of the utility model.

Claims

1. A novel reaction device for preparing polyglycolic acid, characterized in that: The invention comprises a reactor, a condenser, a drying tower and a circulation pump. The reactor comprises a reactor body and a jacket arranged outside the reactor body. A feed inlet is arranged on the upper part of the reactor body, steam is passed through the jacket, a stirring motor is installed on the top of the reactor body, a stirring paddle is fixedly connected to the output shaft of the motor, the top of the reactor body is connected to the bottom of the condenser through a pipeline, the top of the condenser is connected to the drying tower through a pipeline, a tail gas outlet is arranged at the lower end of the drying tower to form a gas phase loop, a discharge pipe is arranged at the bottom of the reactor body, the discharge pipe is connected to the circulation pump, the output end of the circulation pump is connected to the bottom of the drying tower, and the top of the drying tower is connected to the top of the reactor body to form a liquid phase loop.

2. A novel reaction device for preparing polyglycolic acid according to claim 1, characterized in that: The body of the reactor is made of polytetrafluoroethylene, polystyrene, 304 stainless steel, glass lining or ceramic.

3. A novel reaction device for preparing polyglycolic acid according to claim 1, characterized in that: The stirring paddle is tangent to the inner wall of the kettle body, and the blade type of the stirring paddle is frame type, anchor type, turbine type or three-blade backward curved type.

4. A novel reaction device for preparing polyglycolic acid according to claim 1, characterized in that: The condenser is a water-cooled condenser, a water inlet is arranged at the bottom of the condenser, and a water outlet is arranged at the top of the condenser. The type of the condenser is a folded plate type, a double tube type, a U-shaped tube type, or a sleeve type.

5. A novel reaction device for preparing polyglycolic acid according to claim 1, characterized in that: The drying medium of the drying tower is molecular sieve, resin, silica gel or activated alumina.

6. A novel reaction device for preparing polyglycolic acid according to claim 1, characterized in that: The circulating pump is a centrifugal pump, a mixed flow pump, an axial flow pump or an electromagnetic pump.

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