A device and method for producing glycolide

Abstract

This invention belongs to the field of organic synthesis technology, specifically relating to a production apparatus and method for glycolide. The glycolide production apparatus of this invention includes: a reactor; the reactor comprising a first reaction section and a second reaction section separated by a partition, the outlet of the first reaction section and the inlet of the second reaction section being connected; and a heating device disposed at the inlet of the first reaction section. Compared with the prior art, the glycolide production apparatus of this invention employs a specific structure and connection relationship, using a one-pot process to prepare glycolide, realizing the centralized conduction of multiple reactions in the same reactor, solving the pipeline blockage problem caused by using multiple reactors. Simultaneously, this apparatus enables continuous glycolide production.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis technology, and more specifically, to an apparatus and method for producing glycolide. Background Technology

[0002] Polyglycolic acid (PGA), also known as polyglycolic acid, possesses excellent biocompatibility, gas barrier properties, and biodegradability, making it a viable alternative to medical and general-purpose resin materials. Furthermore, PGA is composed of easily hydrolyzable ester bonds, resulting in a relatively flexible main chain that is readily biodegradable, exhibiting excellent tissue compatibility. There are two main routes for the synthesis of PGA: one involves direct dehydration polymerization of glycolic acid monomers, but this method yields PGA with a low molecular weight and dark color, hindering practical applications; the other route involves first oligomerizing glycolic acid monomers to obtain glycolic acid oligomers, then depolymerizing them at high temperatures to obtain glycolide, followed by ring-opening polymerization of glycolide to obtain PGA. This method yields high-molecular-weight, high-performance PGA products. However, the preparation of glycolide monomers is currently difficult and costly, significantly limiting the use of PGA materials. Patent US2668162 discloses a method for preparing glycolide, which involves first oligomerizing glycolic acid, then crushing the oligomers into powder, and finally depolymerizing them to obtain glycolide. In the process of preparing glycolide using this method, the pipeline is prone to blockage due to the problem of solid transport. Moreover, the addition of solids significantly reduces the temperature of the pyrolysis reactor and the pyrolysis efficiency of the reactor.

[0003] Patent application (CN87107549A) discloses a method for preparing glycolide, which involves reacting glycolic acid or its ester with a polyether to form a copolymer, followed by depolymerization to obtain glycolide. This method has a fast reaction rate and high yield; however, the introduction of the polyether causes its decomposition during the pyrolysis process, resulting in glycolide containing a large amount of polyether decomposition byproducts, thus affecting the purity of the product.

[0004] Patent application (CN104981465A) discloses a method for preparing glycolide, in which polyethylene glycol ether is heated to the depolymerization temperature of polyglycolic acid, then mixed with polyglycolic acid to form a solution. After depolymerization, glycolide and polyethylene glycol are simultaneously distilled off from the reactor, followed by separation and recovery of glycolide. This method increases the production cost of glycolide, and the glycolide is unstable during the separation process from the solvent, which can easily lead to glycolide polymerization.

[0005] Therefore, finding a simple and effective method to prepare glycolide is of great significance. This method can reduce the use of multiple reaction devices, lower production costs, solve the problem of material clogging pipelines during glycolide production, address the issue of discontinuous one-pot glycolide preparation, and reduce carbonization and impurity introduction during glycolic acid oligomer pyrolysis, thereby improving product yield and purity. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide an apparatus and method for producing glycolide, which can realize continuous preparation of glycolide, solve the problem of pipeline blockage during the preparation process, and avoid carbonization of the product during the pyrolysis process.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] An apparatus for producing glycolide, comprising:

[0009] Reactor;

[0010] The reactor includes a first reaction section and a second reaction section separated by a partition, and the outlet of the first reaction section and the inlet of the second reaction section are connected.

[0011] A heating device is installed at the inlet of the first reaction section.

[0012] In this invention, the reactor can be sealed to create a vacuum environment, which is beneficial for the polymerization of glycolic acid monomers and the depolymerization of oligoglycolic acid.

[0013] The first reaction section is used for the polymerization of glycolic acid monomers to generate oligomeric glycolic acid products. The second reaction section is used for the depolymerization of glycolic acid oligomers to generate glycolide products. The heating device is used for heating the glycolic acid monomer polymerization process, and the heating device is preferably a heat exchanger.

[0014] In this invention, the glycolide production apparatus further includes a valve disposed on the baffle plate; the valve is connected to the baffle plate by means of flange or welding; the valve is preferably a back pressure valve, with a pressure range of 0.05–0.6 MPa. The back pressure valve is used to regulate the flow of material between the first reaction section and the second reaction section, as well as the pressure in the first and second reaction sections. When the pressure in the first reaction section rises to the pressure range of the back pressure valve, the back pressure valve will automatically open, and the material will enter the second reaction section from the first reaction section through the back pressure valve.

[0015] The apparatus for producing glycolide of the present invention further includes:

[0016] The first vacuum system is installed in the first reaction section;

[0017] A second vacuum system is installed in the second reaction section;

[0018] The inlet of the first vacuum system is connected to the first reaction section via a pipeline. The first vacuum system is used to remove small molecules generated in the first reaction section and to establish a vacuum environment within the first reaction section, thereby improving the polymerization efficiency of glycolic acid monomers. The inlet of the second vacuum system is connected to the second reaction section via a pipeline. The second vacuum system is used to establish a vacuum environment within the second reaction section, thereby improving the depolymerization efficiency of oligoglycolic acid.

[0019] The small molecules excluded by the first vacuum system include at least one of water, methanol, and ethanol.

[0020] The glycolide production apparatus of the present invention further includes: a power transmission device disposed at the inlet of the first reaction section; the transmission device is capable of transporting glycolic acid monomers to the first reaction section, and the power transmission device is preferably a melt pump.

[0021] In this invention, staggered baffles are provided in the first reaction section;

[0022] In the first reaction section, the number of baffles is 6 to 120; the first reaction section consists of R1 section and R2 section, wherein the ratio of the number of baffles in R1 section to R2 section is 1:1 to 9:1; in the first reaction section, every two baffles are connected by a vacuum pipeline to the material and the first vacuum system.

[0023] In this invention, the second reaction section is provided with staggered baffles, and the last baffle of the second reaction section is connected to a material discharge port;

[0024] In the second reaction section, the number of baffles is 3 to 30. This invention sets up staggered baffles in the first and second reaction sections. Each baffle has a material conveying port between its end and the reactor wall. The material below is conveyed to the baffle above through the conveying port. The staggered baffles, with their gaps, form a serpentine channel, greatly increasing the residence time of the material in the reaction section, allowing the material to react fully in the reactor. Simultaneously, the continuous movement of the material reduces carbonization and coking during the reaction process.

[0025] The present invention also provides a method for producing glycolide, comprising:

[0026] Using the above-mentioned apparatus, glycolic acid monomers are polymerized under heating to obtain glycolic acid oligomers, and then the glycolic acid oligomers are depolymerized under heating to obtain glycolide.

[0027] This invention uses glycolic acid monomers as raw materials, polymerizes the glycolic acid monomers under heating to obtain glycolic acid oligomers; the flow rate of the glycolic acid monomers is preferably 0.1-10 m / h; the heating is preferably carried out using a heat exchanger; the number average molecular weight of the glycolic acid oligomers is 800-10000 g / mol, preferably 2900-4200 g / mol.

[0028] The glycolic acid monomer is selected from one or more of glycolic acid, methyl glycolate, and ethyl glycolate; the purity of the glycolic acid monomer is preferably 100%; in one embodiment, the glycolic acid monomer is glycolic acid;

[0029] The polymerization is carried out in the presence of a catalyst; the catalyst is a metal composite catalyst; the catalyst is selected from at least two of stannous chloride, stannous octoate, stannous benzoate, tin oxide, tin acetate, zinc chloride, zinc acetate, zinc lactate, zinc acetylacetonate, zinc oxide, antimony trioxide, antimony acetate, antimony chloride, and lanthanum acetate, preferably at least two of stannous benzoate, stannous chloride, zinc oxide, zinc chloride, stannous octoate, antimony acetate, tin oxide, tin acetate, zinc lactate, antimony chloride, antimony trioxide, and zinc acetylacetonate; in one embodiment, the catalyst is stannous benzoate and antimony trioxide, and the mass ratio of stannous benzoate to antimony trioxide is preferably 4:5; in one embodiment, the catalyst is antimony acetate and tin oxide, and the mass ratio of antimony acetate to tin oxide is preferably 4:3; in one embodiment, the catalyst is zinc acetate and tin acetate, and the mass ratio of zinc acetate to tin acetate is preferably 7:5; in one embodiment, the catalyst is stannous chloride and antimony acetate, and the mass ratio of stannous chloride to antimony acetate is preferably 4:3;

[0030] The mass ratio of the catalyst to the glycolic acid monomer is (0.01-10):100, preferably (0.01-0.7):100.

[0031] In this invention, the polymerization is carried out in the presence of a solvent; the decomposition temperature of the solvent is >300°C; the mass ratio of the solvent to the glycolic acid monomer is (1-9):(1-5), preferably (1-9):1;

[0032] The solvent is a substituted or unsubstituted silicone oil; the number average molecular weight of the substituted or unsubstituted silicone oil is preferably 1000-10000 g / mol; the solvent is preferably phenyl silicone oil, in which the molar fraction of phenyl is 5%-50%; the phenyl silicone oil is diphenyl silicone oil or methylphenyl silicone oil, preferably diphenyl silicone oil.

[0033] In this invention, the polymerization is carried out under vacuum conditions, with a vacuum degree of 1 to 5000 Pa, preferably 1000 Pa; a temperature of 120 to 240°C, preferably 140 to 240°C; and a time of 20 min to 20 h.

[0034] The polymerization reaction preferably involves first polymerizing the raw materials, followed by a second polymerization. The first polymerization is carried out under vacuum conditions, with a vacuum level of 1–5000 Pa, a temperature of 120–200 °C, and a time of 10 min–15 h. The second polymerization is carried out under vacuum conditions, with a vacuum level of 1–5000 Pa, a temperature of 200–250 °C, and a time of 10 min–5 h. In this invention, glycolic acid oligomers are depolymerized under heating to obtain glycolide. The flow rate of the glycolic acid oligomers is preferably 0.5–3 m / h. The depolymerization is carried out under vacuum conditions, with a vacuum level of 1–1000 Pa, preferably 300 Pa; a temperature of 200–300 °C, preferably 240–280 °C; and a time of 10 min–2 h.

[0035] In one embodiment of the present invention, the apparatus for producing glycolide is as follows: Figure 1 As shown, B1 is a static mixer, M1 is a melt pump, HE1 is a heat exchanger, R1 and R2 are connected in series to form the first reaction section, forming an integral structure. The length ratio of R1 to R2 is 2:1. The first reaction section is equipped with staggered baffles. There are 6 baffles in R1 and 3 baffles in R2. R3 is the second reaction section, V1 is the first vacuum system, and V2 is the second vacuum system.

[0036] The production apparatus provided by this invention employs a specific structure and connection relationship, and uses a one-pot process to prepare glycolide, that is, the polymerization of glycolic acid monomers and the depolymerization of oligomeric glycolic acid are both carried out in the same reactor. This technical solution realizes that multiple reactions are concentrated in one reactor, solving the problem of pipeline blockage caused by using multiple reactors. At the same time, this apparatus realizes continuous preparation of glycolide, solving the problem that conventional one-pot methods cannot produce continuously, saving process flow, reducing production costs, and improving production efficiency.

[0037] This invention utilizes silicone oil solvent to increase the reaction rate of glycolic acid monomer condensation during polymerization and depolymerization, thereby increasing the heating area of ​​oligoglycolic acid and thus improving the depolymerization rate of oligoglycolic acid. As a result, there is less coking and carbonization. Moreover, the silicone oil solvent is stable and will not decompose within the temperature range of this invention, nor will it evaporate with glycolide. This avoids the product contamination problem caused by the introduction of high-boiling-point solvents during the pyrolysis of glycolic acid oligomers. The production apparatus and production method provided by this invention can be used for the industrial production of glycolide. Attached Figure Description

[0038] Figure 1 This is the production apparatus for synthesizing glycolide in Example 1 of the present invention;

[0039] Figure 2 This is a liquid chromatogram of glycolide in Example 13 of the present invention. Detailed Implementation

[0040] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0041] To further illustrate the present invention, the following embodiments are provided for detailed description. All raw materials used in the following embodiments of the present invention are commercially available products.

[0042] The molecular weight of the polymers in the embodiments of the present invention was determined by gel permeation chromatography (GPC) using a series of linear Styragel columns (HT2 and HT4) and a Waters 410 HPLC pump with a Waters 2414RI detector. Hexafluoroisopropanol was used as the mobile phase, and the flow rate was 1 mL / min at 25 °C. Monodisperse polystyrene standards were used for universal correction.

[0043] The purity of glycolide was tested using a gas chromatograph (PerkinElmer, Clarus 590): PerkinElmer Instruments Ltd. Chromatographic operating conditions: carrier gas: N2, column temperature: 140℃, FID temperature: 250℃, injector temperature: 250℃, column flow rate: 0.5 mL / min, split ratio: 20:1.

[0044] The acid value of glycolide was tested using a Metrohm 905 potentiometric titrator: Electrode: non-aqueous glass electrode; Titrate: 0.01 mol / L potassium methoxide in anhydrous methanol solution; Solvent: dichloromethane and anhydrous methanol mixed at a volume ratio of 4:1.

[0045] Example 1

[0046] The apparatus for producing glycolide in this embodiment of the invention is as follows: Figure 1As shown, B1 is a static mixer, M1 is a melt pump, the inlet of M1 and the outlet of B1 are connected by a pipeline, HE1 is a heat exchanger, the inlet of HE1 and the outlet of M1 are connected by a pipeline, R1 and R2 are connected in series to form the first reaction section, forming an integral structure, the length ratio of R1 to R2 is 2:1, the inlet of R1 and the outlet of HE1 are connected by a pipeline, the first reaction section is equipped with staggered baffles, there are 6 baffles in R1 section and 3 baffles in R2 section, the inlet of R3 and the outlet of R2 are connected by a back pressure valve E1, R3 is the second reaction section, R3 is equipped with staggered baffles, there are 3 baffles in R3 section, V1 is the first vacuum system, the vacuum pipeline of V1 is connected to R2 section by a pipeline, V2 is the second vacuum system, the vacuum pipeline of V2 is located at the top of the vessel and is connected to R3 by a pipeline.

[0047] The process of preparing glycolide using the above-mentioned apparatus is as follows:

[0048] 1) Glycolic acid monomers, catalysts and solvents are mixed in static mixer B1, and then transported to R1 section of the first reaction section through melt pump M1 and heat exchanger HE1. Vacuum is drawn using the first vacuum system V1, and the material is heated using the first heat exchanger HE1. The material is conveyed upward along the baffles in a push flow manner. There is a material conveying port between the end of each baffle and the vessel wall. The material below is conveyed to the baffle above through the conveying port. The flow velocity of the material in the first reaction section is 0.1 to 10 m / h. After the R1 and R2 sections of reaction are completed, oligoglycolic acid is obtained.

[0049] 2) Oligoglycolic acid enters the second reaction section, i.e., section R3, through the back pressure valve E1. In section R3, the second vacuum system V2 is used to evacuate the vacuum. Oligoglycolic acid continues to be conveyed on the baffle and completes depolymerization. The flow rate of the material in the second reaction section is 0.1 to 10 m / h, and glycolide is obtained.

[0050] Example 2

[0051] 2.1 10 kg of 100% glycolic acid, 20 kg of diphenyl silicone oil, and catalyst (5 g stannous chloride + 5 g zinc oxide) were fed into the R1 section of the reactor via a static mixer, melt pump, and heat exchanger. The heat exchanger temperature was 150 degrees Celsius, and the reactor temperature was 160 degrees Celsius. A vacuum system (V1) was used to evacuate the reactor for polycondensation reaction. The pressure was 1000 Pa, and the material flow rate was 0.2 m / h. After the R1 section reaction was completed, the material directly entered the R2 section of the reactor. The material flow rate was 0.2 m / h, and the temperature of the R2 section was 220 degrees Celsius, yielding oligomeric glycolic acid.

[0052] The oligoglycolic acid obtained in this invention was analyzed by gel permeation chromatography, and the number average molecular weight of the oligoglycolic acid was found to be 3200 g / mol.

[0053] 2.2 The oligoglycolic acid obtained from the R2 stage reaction is fed into the R3 stage of the reactor through the back pressure valve E1. The back pressure valve is set to a pressure of 0.1 MPa. The reaction is carried out by evacuating the vacuum system V2. The reactor temperature is 240 degrees Celsius, the material flow rate is 0.6 m / h, and P = 300 Pa. The glycolide is collected through the V2 vacuum system, and the pyrolysis residue is discharged from the system through the outlet E2.

[0054] The glycolide prepared in Example 2 of this invention was subjected to gas chromatography. The test results showed that the glycolide purity was 96.7%, and the remainder consisted of light components (glycolic acid) and heavy components (glycolic acid oligomers).

[0055] The acidity of the glycolide prepared in Example 2 of this invention was tested according to the above method, and the result was that the acid value of glycolide was 34 ppm.

[0056] Example 3

[0057] 3.1 10 kg of 100% glycolic acid, 30 kg of diphenyl silicone oil, and catalyst (8 g zinc chloride + 5 g antimony trioxide) were fed into the R1 section of the reactor via a static mixer, melt pump, and heat exchanger. The heat exchanger temperature was 160 degrees Celsius, and the reactor temperature was 170 degrees Celsius. A vacuum system (V1) was used to evacuate the reactor for polycondensation reaction. The pressure was 1000 Pa, and the material flow rate was 0.3 m / h. After the R1 section reaction was completed, the material directly entered the R2 section of the reactor. The material flow rate was 0.3 m / h, and the temperature of the R2 section was 230 degrees Celsius, yielding oligomeric glycolic acid.

[0058] The oligoglycolic acid obtained in this invention was analyzed by gel permeation chromatography, and the number average molecular weight of the oligoglycolic acid was found to be 3500 g / mol.

[0059] 3.2 The oligoglycolic acid obtained from the R2 stage reaction is fed into the R3 stage of the reactor through the back pressure valve E1. The back pressure valve is set to a pressure of 0.1 MPa. The reaction is carried out by evacuating the vacuum system V2. The reactor temperature is 250 degrees Celsius, the material flow rate is 0.7 m / h, and P = 300 Pa. The glycolide is collected through the V2 vacuum system, and the pyrolysis residue is discharged from the system through the outlet E2.

[0060] The glycolide prepared in Example 3 of this invention was subjected to gas chromatography. The test results showed that the glycolide purity was 97.7%, and the remainder consisted of light components (glycolic acid) and heavy components (glycolic acid oligomers).

[0061] The acidity of the glycolide prepared in Example 3 of this invention was tested according to the above method, and the result was that the acid value of glycolide was 23 ppm.

[0062] Example 4

[0063] 4.1 10 kg of 100% glycolic acid, 40 kg of diphenyl silicone oil, and catalyst (10 g stannous octoate + 5 g zinc chloride) were fed into the R1 section of the reactor via a static mixer, melt pump, and heat exchanger. The heat exchanger temperature was 170 degrees Celsius, and the reactor temperature was 170 degrees Celsius. A vacuum system (V1) was used to evacuate the reactor for polycondensation reaction. The pressure was 1000 Pa, and the material flow rate was 0.4 m / h. After the R1 section reaction was completed, the material directly entered the R2 section of the reactor. The material flow rate was 0.4 m / h, and the temperature of the R2 section was 220 degrees Celsius, yielding oligomeric glycolic acid.

[0064] The oligoglycolic acid obtained in this invention was analyzed by gel permeation chromatography, and the number average molecular weight of the oligoglycolic acid was found to be 3900 g / mol.

[0065] 4.2 The oligoglycolic acid obtained from the R2 stage reaction is fed into the R3 stage of the reactor through the back pressure valve E1. The back pressure valve is set to 0.1 MPa. Vacuum is applied using the V2 vacuum system for the reaction. The reactor temperature is 260 degrees Celsius, the material flow rate is 0.8 m / h, and P = 300 Pa. The glycolide is collected through the V2 vacuum system, and the pyrolysis residue is discharged from the system through outlet E2. Gas chromatography was used to test the glycolide prepared in Example 4 of this invention. The test results showed that the glycolide purity was 96.3%, with the remainder being light components (glycolic acid) and heavy components (glycolic acid oligomers).

[0066] The acidity of the glycolide prepared in Example 4 of this invention was tested according to the above method, and the result was that the acid value of glycolide was 32 ppm.

[0067] Example 5

[0068] 5.1 10 kg of 100% methyl glycolate, 15 kg of diphenyl silicone oil, and catalyst (12 g antimony acetate + 8 g tin oxide) were fed into section R1 of the reactor via a static mixer, melt pump, and heat exchanger. The heat exchanger temperature was 140 degrees Celsius, and the reactor temperature was 140 degrees Celsius. A vacuum system (V1) was used to evacuate the reactor for polycondensation reaction. The pressure was 1000 Pa, and the material flow rate was 0.2 m / h. After the reaction in section R1 was completed, the material directly entered section R2 of the reactor. The material flow rate was 0.2 m / h, and the temperature in section R2 was 210 degrees Celsius, yielding oligomeric glycolic acid.

[0069] The oligoglycolic acid obtained in this invention was analyzed by gel permeation chromatography, and the number average molecular weight of the oligoglycolic acid was found to be 3100 g / mol.

[0070] 5.2 The oligoglycolic acid obtained from the R2 stage reaction is fed into the R3 stage of the reactor through the back pressure valve E1. The back pressure valve is set to 0.1 MPa. Vacuum is applied using the V2 vacuum system for the reaction. The reactor temperature is 270 degrees Celsius, the material flow rate is 1 m / h, and P = 300 Pa. The glycolide is collected through the V2 vacuum system, and the pyrolysis residue is discharged from the system through outlet E2. Gas chromatography was used to test the glycolide prepared in Example 5 of this invention. The test results showed that the glycolide purity was 95.4%, with the remainder being light components (glycolic acid and methyl glycolate) and heavy components (glycolic acid oligomers).

[0071] The acidity of the glycolide prepared in Example 5 of this invention was tested according to the above method, and the result was that the acid value of glycolide was 29 ppm.

[0072] Example 6

[0073] 6.1 10 kg of 100% methyl glycolate, 30 kg of diphenyl silicone oil, and catalyst (14 g zinc acetate + 10 g tin acetate) were fed into section R1 of the reactor via a static mixer, melt pump, and heat exchanger. The heat exchanger temperature was 150 degrees Celsius, and the reactor temperature was 150 degrees Celsius. A vacuum system (V1) was used to evacuate the reactor for polycondensation reaction. The pressure was 1000 Pa, and the material flow rate was 0.2 m / h. After the reaction in section R1 was completed, the material was directly fed into section R2 of the reactor. The material flow rate was 0.2 m / h, and the temperature in section R2 was 230 degrees Celsius, yielding oligomeric glycolic acid.

[0074] The oligoglycolic acid obtained in this invention was analyzed by gel permeation chromatography, and the number average molecular weight of the oligoglycolic acid was found to be 3300 g / mol.

[0075] 6.2 The oligoglycolic acid obtained from the R2 stage reaction is fed into the R3 stage of the reactor through the back pressure valve E1. The back pressure valve is set to 0.1 MPa. Vacuum is applied using the V2 vacuum system for the reaction. The reactor temperature is 280 degrees Celsius, the material flow rate is 1.3 m / h, and P = 300 Pa. The glycolide is collected through the V2 vacuum system, and the pyrolysis residue is discharged from the system through outlet E2. Gas chromatography was used to test the glycolide prepared in Example 6 of this invention. The test results showed that the glycolide purity was 96.1%, with the remainder being light components (glycolic acid and methyl glycolate) and heavy components (glycolic acid oligomers).

[0076] The acidity of the glycolide prepared in Example 6 of this invention was tested according to the above method, and the result was that the acid value of glycolide was 36 ppm.

[0077] Example 7

[0078] 7.1 10 kg of 100% methyl glycolate, 20 kg of methylphenyl silicone oil, and catalyst (16 g stannous chloride + 10 g zinc lactate) are fed into section R1 of the reactor via a static mixer, melt pump, and heat exchanger. The heat exchanger temperature is 160 degrees Celsius, and the reactor temperature is 160 degrees Celsius. A vacuum system (V1) is used to evacuate the reactor for polycondensation reaction. P = 1000 Pa, and the material flow rate is 0.2 m / h. After the reaction in section R1 is completed, the material directly enters section R2 of the reactor. The material flow rate is 0.2 m / h, and the temperature in section R2 is 220 degrees Celsius, yielding oligomeric glycolic acid.

[0079] The oligoglycolic acid obtained in this invention was analyzed by gel permeation chromatography, and the number average molecular weight of the oligoglycolic acid was found to be 3600 g / mol.

[0080] 7.2 The oligoglycolic acid obtained from the R2 stage reaction is fed into the R3 stage of the reactor through the back pressure valve E1. The back pressure valve is set to 0.1 MPa. Vacuum is applied using the V2 vacuum system for the reaction. The reactor temperature is 240 degrees Celsius, the material flow rate is 0.5 m / h, and P = 300 Pa. The glycolide is collected through the V2 vacuum system, and the pyrolysis residue is discharged from the system through outlet E2. Gas chromatography was used to test the glycolide prepared in Example 7 of this invention. The test results showed that the glycolide purity was 97.4%, with the remainder being light components (glycolic acid and methyl glycolate) and heavy components (glycolic acid oligomers).

[0081] The acidity of the glycolide prepared in Example 7 of this invention was tested according to the above method, and the result was that the acid value of glycolide was 21 ppm.

[0082] Example 8

[0083] 8.1 10 kg of 100% methyl glycolate, 30 kg of methylphenyl silicone oil, and catalyst (20 g antimony chloride + 15 g zinc oxide) were fed into section R1 of the reactor via a static mixer, melt pump, and heat exchanger. The heat exchanger temperature was 170 degrees Celsius, and the reactor temperature was 170 degrees Celsius. A vacuum system (V1) was used to evacuate the reactor for polycondensation reaction. The pressure was 1000 Pa, and the material flow rate was 0.4 m / h. After the reaction in section R1 was completed, the material was directly fed into section R2 of the reactor. The material flow rate was 0.4 m / h, and the temperature in section R2 was 230 degrees Celsius, yielding oligomeric glycolic acid.

[0084] The oligoglycolic acid obtained in this invention was analyzed by gel permeation chromatography, and the number average molecular weight of the oligoglycolic acid was found to be 3800 g / mol.

[0085] 8.2 The oligoglycolic acid obtained from the R2 stage reaction is fed into the R3 stage of the reactor through the back pressure valve E1. The back pressure valve is set to 0.1 MPa. Vacuum is applied using the V2 vacuum system for the reaction. The reactor temperature is 250 degrees Celsius, the material flow rate is 0.6 m / h, and P = 300 Pa. The glycolide is collected through the V2 vacuum system, and the pyrolysis residue is discharged from the system through outlet E2. The glycolide prepared in Example 8 of this invention is subjected to gas chromatography testing. The test results show that the glycolide purity is 96.5%, with the remainder being light components (glycolic acid and methyl glycolate) and heavy components (glycolic acid oligomers).

[0086] The acidity of the glycolide prepared in Example 8 of this invention was tested according to the above method, and the result was that the acid value of glycolide was 19 ppm.

[0087] Example 9

[0088] 9.1 10 kg of 100% ethyl glycolate, 40 kg of methylphenyl silicone oil, and catalyst (25 g stannous chloride + 20 g zinc acetylacetonate) were fed into section R1 of the reactor via a static mixer, melt pump, and heat exchanger. The heat exchanger temperature was 150 degrees Celsius, and the reactor temperature was 150 degrees Celsius. A vacuum system (V1) was used to evacuate the reactor for polycondensation reaction. The pressure was 1000 Pa, and the material flow rate was 0.2 m / h. After the reaction in section R1 was completed, the material directly entered section R2 of the reactor. The material flow rate was 0.2 m / h, and the temperature in section R2 was 210 degrees Celsius, yielding oligomeric glycolic acid.

[0089] The oligoglycolic acid obtained in this invention was analyzed by gel permeation chromatography, and the number average molecular weight of the oligoglycolic acid was found to be 3000 g / mol.

[0090] 9.2 The oligoglycolic acid obtained from the R2 stage reaction is fed into the R3 stage of the reactor through the back pressure valve E1. The back pressure valve is set to 0.1 MPa. Vacuum is applied using the V2 vacuum system for the reaction. The reactor temperature is 260 degrees Celsius, the material flow rate is 0.8 m / h, and P = 300 Pa. The glycolide is collected through the V2 vacuum system, and the pyrolysis residue is discharged from the system through outlet E2. The glycolide prepared in Example 9 of this invention is subjected to gas chromatography testing. The test results show that the glycolide purity is 97.1%, with the remainder being light components (glycolic acid and ethyl glycolate) and heavy components (glycolic acid oligomers).

[0091] The acidity of the glycolide prepared in Example 9 of this invention was tested according to the above method, and the result was that the acid value of glycolide was 25 ppm.

[0092] Example 10

[0093] 10.1 10 kg of 100% ethyl glycolate, 50 kg of methylphenyl silicone oil, and catalyst (30 g stannous benzoate + 15 g antimony trioxide) were fed into section R1 of the reactor via a static mixer, melt pump, and heat exchanger. The heat exchanger temperature was 160 degrees Celsius, and the reactor temperature was 160 degrees Celsius. A vacuum system (V1) was used to evacuate the reactor for polycondensation reaction. The pressure was 1000 Pa, and the material flow rate was 0.2 m / h. After the reaction in section R1 was completed, the material directly entered section R2 of the reactor. The material flow rate was 0.2 m / h, and the temperature in section R2 was 220 degrees Celsius, yielding oligomeric glycolic acid.

[0094] The oligoglycolic acid obtained in this invention was analyzed by gel permeation chromatography, and the number average molecular weight of the oligoglycolic acid was found to be 3600 g / mol.

[0095] 10.2 The oligoglycolic acid obtained from the R2 stage reaction is fed into the R3 stage of the reactor through the back pressure valve E1. The back pressure valve is set to 0.1 MPa. Vacuum is applied using the V2 vacuum system for the reaction. The reactor temperature is 270 degrees Celsius, the material flow rate is 0.9 m / h, and P = 300 Pa. The glycolide is collected through the V2 vacuum system, and the pyrolysis residue is discharged from the system through outlet E2. The glycolide prepared in Example 10 of this invention was subjected to gas chromatography testing. The test results showed that the glycolide purity was 95.9%, with the remainder being light components (glycolic acid and ethyl glycolate) and heavy components (glycolic acid oligomers).

[0096] The acidity of the glycolide prepared in Example 10 of this invention was tested according to the above method, and the result was that the acid value of glycolide was 28 ppm.

[0097] Example 11

[0098] 11.1 10 kg of 100% glycolic acid, 70 kg of methylphenyl silicone oil, and catalyst (35 g antimony acetate + 20 g zinc chloride) are fed into the R1 section of the reactor via a static mixer, melt pump, and heat exchanger. The heat exchanger temperature is 170 degrees Celsius, and the reactor temperature is 170 degrees Celsius. A vacuum system (V1) is used to evacuate the reactor for polycondensation reaction. P = 1000 Pa, and the material flow rate is 0.4 m / h. After the R1 section reaction is completed, the material directly enters the R2 section of the reactor. The material flow rate is 0.4 m / h, and the temperature of the R2 section is 230 degrees Celsius, yielding oligomeric glycolic acid.

[0099] The oligoglycolic acid obtained in this invention was analyzed by gel permeation chromatography, and the number average molecular weight of the oligoglycolic acid was found to be 3700 g / mol.

[0100] 11.2 The oligoglycolic acid obtained from the R2 stage reaction is fed into the R3 stage of the reactor through the back pressure valve E1. The back pressure valve is set to 0.1 MPa. Vacuum is applied using the V2 vacuum system for the reaction. The reactor temperature is 280 degrees Celsius, the material flow rate is 1.2 m / h, and P = 300 Pa. The glycolide is collected through the V2 vacuum system, and the pyrolysis residue is discharged from the system through outlet E2. The glycolide prepared in Example 11 of this invention is subjected to gas chromatography. The test results show that the glycolide purity is 96.4%, with the remainder being light components (glycolic acid) and heavy components (glycolic acid oligomers).

[0101] The acidity of the glycolide prepared in Example 11 of this invention was tested according to the above method, and the result was that the acid value of glycolide was 17 ppm.

[0102] Example 12

[0103] 12.1 10 kg of 100% glycolic acid, 90 kg of diphenyl silicone oil, and catalyst (40 g stannous chloride + 30 g antimony acetate) are fed into the R1 section of the reactor via a static mixer, melt pump, and heat exchanger. The heat exchanger temperature is 170 degrees Celsius, and the reactor temperature is 170 degrees Celsius. A vacuum system (V1) is used to evacuate the reactor for polycondensation reaction. P = 1000 Pa, and the material flow rate is 0.2 m / h. After the R1 section reaction is completed, the material directly enters the R2 section of the reactor. The material flow rate is 0.2 m / h, and the temperature of the R2 section is 240 degrees Celsius, yielding oligomeric glycolic acid.

[0104] The oligoglycolic acid obtained in this invention was analyzed by gel permeation chromatography, and the number average molecular weight of the oligoglycolic acid was found to be 4200 g / mol.

[0105] 12.2 The oligoglycolic acid obtained from the R2 stage reaction is fed into the R3 stage of the reactor through the back pressure valve E1. The back pressure valve is set to 0.1 MPa. Vacuum is applied using the V2 vacuum system for the reaction. The reactor temperature is 260 degrees Celsius, the material flow rate is 0.8 m / h, and P = 300 Pa. The glycolide is collected through the V2 vacuum system, and the pyrolysis residue is discharged from the system through outlet E2. The glycolide prepared in Example 12 of this invention was subjected to gas chromatography testing. The test results showed that the glycolide purity was 98.1%, with the remainder being light components (glycolic acid) and heavy components (glycolic acid oligomers).

[0106] The acidity of the glycolide prepared in Example 12 of this invention was tested according to the above method, and the result was that the acid value of glycolide was 15 ppm.

[0107] Example 13

[0108] 13.1 10 kg of 100% glycolic acid, 10 kg of diphenyl silicone oil, and catalyst (4 g stannous benzoate + 5 g antimony trioxide) are fed into the R1 section of the reactor via a static mixer, melt pump, and heat exchanger. The heat exchanger temperature is 140 degrees Celsius, and the reactor temperature is 160 degrees Celsius. A vacuum system (V1) is used to evacuate the reactor for polycondensation reaction. P = 1000 Pa, and the material flow rate is 0.1 m / h. After the R1 section reaction is completed, the material directly enters the R2 section of the reactor. The material flow rate is 0.1 m / h, and the temperature of the R2 section is 210 degrees Celsius, yielding oligomeric glycolic acid.

[0109] The oligoglycolic acid obtained in this invention was analyzed by gel permeation chromatography, and the number average molecular weight of the oligoglycolic acid was found to be 2900 g / mol.

[0110] 13.2 The oligoglycolic acid obtained from the R2 stage reaction is fed into the R3 stage of the reactor through the back pressure valve E1. The back pressure valve is set to 0.1 MPa. Vacuum is applied using the V2 vacuum system for the reaction. The reactor temperature is 230 degrees Celsius, the material flow rate is 0.5 m / h, and P = 300 Pa. The glycolide is collected through the V2 vacuum system, and the pyrolysis residue is discharged from the system through outlet E2. Gas chromatography was used to test the glycolide prepared in Example 13 of this invention. The test results showed that the glycolide purity was 97.2%, with the remainder being light components (glycolic acid) and heavy components (glycolic acid oligomers), as shown in Table 1 and... Figure 2 As shown.

[0111] Table 1

[0112] glycolic acid 3.095 5 0.18 Glycolide 4.522 2556 97.2 Glycolic acid oligomers 5.352 69 2.62

[0113] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for producing glycolide, characterized in that, The following apparatus was used to prepare glycolide: The inlet of the melt pump and the outlet of the static mixer are connected by a pipeline. The inlet of the heat exchanger and the outlet of the melt pump are connected by a pipeline. Sections R1 and R2 are connected in series to form the first reaction section, forming an integral structure. The inlet of R1 and the outlet of the heat exchanger are connected by a pipeline. The first reaction section is equipped with staggered baffles. The inlet of R3 and the outlet of R2 are connected by a back pressure valve. Section R3 is the second reaction section. The R3 section is equipped with staggered baffles. The vacuum pipeline of the first vacuum system is connected to section R2 by a pipeline. The vacuum pipeline of the second vacuum system is located at the top of the vessel and is connected to R3 by a pipeline. The pressure of the back pressure valve is 0.05~0.6MPa. The process of preparing glycolide using the above-mentioned apparatus is as follows: 1) Glycolic acid monomers, catalysts, and solvents are mixed in a static mixer, and then transported to section R1 of the first reaction stage via a melt pump and heat exchanger. A vacuum is created using a first vacuum system, and the material is heated using the heat exchanger. The material is conveyed upwards along the baffles in a plug flow manner. Each baffle has a material conveying port between its end and the reactor wall. The material below is conveyed to the upper baffle through the conveying port. After completing the reactions in sections R1 and R2, oligoglycolic acid is obtained. The solvent is diphenyl silicone oil or methylphenyl silicone oil. 2) Oligoglycolic acid enters the second reaction section, namely R3 section, through the back pressure valve E1. In R3 section, the second vacuum system is used to evacuate the vacuum, and the oligoglycolic acid continues to be transported on the baffle and completes depolymerization to obtain glycolide.

2. The production method according to claim 1, characterized in that, The length ratio of segment R1 to segment R2 is 2:

1.

3. The production method according to claim 1, characterized in that, In step 1), the flow velocity of the material in the first reaction section is 0.1~10m / h.

4. The production method according to claim 1, characterized in that, In step 1), the vacuum level of the vacuum pump is 1~5000Pa, and the heating temperature is 140~240℃.

5. The production method according to claim 1, characterized in that, In step 1), the mass ratio of the catalyst to the glycolic acid monomer is (0.01~0.7):

100.

6. The production method according to claim 1, characterized in that, In step 1), the mass ratio of the solvent to the glycolic acid monomer is (1~9):

1.

7. The production method according to claim 1, characterized in that, In step 2), the flow rate of the oligoglycolic acid is 0.5~3m / h.

8. The production method according to claim 1, characterized in that, In step 2), the vacuum level of the vacuum pump is 1~1000Pa and the temperature is 240~280℃.

9. The production method according to claim 1, characterized in that, The oligoglycolic acid has a number average molecular weight of 800-10000 g / mol; the glycolic acid monomer is selected from one or more of glycolic acid, methyl glycolate, and ethyl glycolate; the polymerization is carried out in the presence of a catalyst; the catalyst is selected from at least two of stannous chloride, stannous octoate, stannous benzoate, tin oxide, tin acetate, zinc chloride, zinc acetate, zinc lactate, zinc acetylacetone, zinc oxide, antimony trioxide, antimony acetate, antimony chloride, and lanthanum acetate.

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