A production device and method for metal particles and glycolide

Abstract

The application relates to the technical field of organic synthesis, in particular to a metal particle and a production device and a preparation method of glycolide. The metal particle comprises a main body and a first side base arranged at one end of the main body; the cross-sectional area of the main body is smaller than that of the first side base; the main body is a hollow structure; an insulated electric heating wire is arranged in the main body; and the insulated electric heating wire is composed of an electric heating wire and an insulation layer covering the electric heating wire. The metal particle can obtain high-purity glycolide, solve the problems of coking and carbonization in the oligomer cracking process and solvent cracking and subsequent separation caused by the addition of high-boiling-point solvents, simplify the production process, broaden the application prospect of the product, promote the industrialization process of the product, and has very important social and economic value.

Description

Technical Field

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

[0002] Polyglycolic acid (PGA) possesses excellent biodegradability, biocompatibility, heat resistance, and gas barrier properties. As a simple and commercially available biodegradable material, it can be used in various applications such as packaging materials, biodegradable films, disposable tableware, surgical sutures, and internal fixation devices for fractures. However, due to the late start and technological backwardness of China's PGA-related fields, there is currently no mature synthesis process for PGA products, and the products mainly rely on imports, resulting in high prices. PGA can be synthesized through two methods: direct polycondensation, which yields PGA by polycondensing glycolic acid monomers in a single step, but the polymer has a low molecular weight and a dark color, making it unusable; and glycolide ring-opening polymerization, which can produce PGA with a higher molecular weight, but currently, glycolide synthesis generally suffers from low yield and easy carbonization, resulting in high production costs. Patent application CN105272958A discloses a method for preparing glycolide, which includes four processes: normal compression polymerization, reduced compression polymerization, enhanced condensation polymerization, and high-temperature depolymerization. Glycolide can be obtained through this method, but the reaction cycle is long, especially in the high-temperature depolymerization stage. Due to the excessively long depolymerization time, a large amount of oligoglycolic acid is carbonized, which puts a great burden on the equipment and greatly reduces the yield.

[0003] Therefore, solving the coking and carbonization problem in the oligomer pyrolysis process, simplifying the production process, and improving the product yield are of great significance for the promotion and application of polyglycolic acid. However, there are currently no reports or patents on a successful simplified process for the synthesis of glycolide. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a production apparatus and preparation method for metal particles and glycolide. Using the metal particles provided by the present invention, high-purity glycolide can be obtained, while solving the problems of coking and carbonization in the oligomer pyrolysis process, as well as the problems of solvent pyrolysis and subsequent separation caused by the addition of high-boiling-point solvents, thus simplifying the production process.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A metal particle includes a body and a first side matrix disposed at one end of the body;

[0007] The cross-sectional area of ​​the main body is smaller than the cross-sectional area of ​​the first side substrate.

[0008] In this invention, the metal particles also include a second side matrix disposed at the other end of the main body.

[0009] In this invention, the main body is a cylinder;

[0010] The first side substrate and the second side substrate are spheres or quasi-spheres, preferably spheres;

[0011] The main body is a hollow structure;

[0012] The main body is equipped with an insulating heating wire inside;

[0013] The insulated heating wire consists of a heating wire and an insulating layer covering the heating wire.

[0014] In this invention, both the first side matrix and the second side matrix are hollow structures;

[0015] The diameter of the sphere of the metal particle is 1 mm to 100 mm, preferably 30 mm, and the length of the main body of the metal particle is 0.05 to 2 m, preferably 0.2 m.

[0016] The main body of the metal particles is selected from one or more of chromium and its alloys, nickel and its alloys, titanium and its alloys, and iron and its alloys, preferably one or more of stainless steel 304, stainless steel 306, stainless steel 316, stainless steel 2507 or double carbon steel. In one embodiment of the present invention, the main body is made of stainless steel 2507.

[0017] The side matrix of the metal particles is selected from one or more of chromium and its alloys, nickel and its alloys, titanium and its alloys, and iron and its alloys, preferably one or more of stainless steel 304, stainless steel 306, stainless steel 316, stainless steel 2507 or double carbon steel. In one embodiment of the present invention, the side matrix is ​​made of stainless steel 2507.

[0018] The diameter of the heating wire is 0.2–8 mm, preferably 2 mm;

[0019] The resistance of the heating wire is 0.02 to 30 Ω / m, preferably 0.34 Ω / m;

[0020] The interior of the metal particle body preferably contains 1 to 10 heating wires;

[0021] The heating wire is preferably made of one or more of the following materials: iron-chromium-aluminum alloy wire, nickel-chromium alloy wire, and manganese-copper wire.

[0022] The present invention does not have special requirements for the shape of the heating wire, as long as it can generate heat after being energized. The heating wire is preferably in the shape of a helical spring.

[0023] The insulating layer completely covers the heating wire. The present invention does not have special requirements for the material of the insulating layer, as long as it is non-conductive, preferably insulating varnish.

[0024] In an embodiment of the invention, the main body of the metal particle is cylindrical, with a length of 0.2m. One end of the main body is connected to a sphere, and the other end is also connected to a sphere. Both spheres have a diameter of 30mm. The main body and spheres of the metal particle are made of stainless steel 2507. Both the main body and spheres have a hollow structure. Inside the metal particle is a nickel-chromium alloy heating wire coated with insulating varnish. The nickel-chromium alloy heating wire is cylindrical and spiral spring-shaped, with a resistance of 0.34Ω / m and a wire diameter of 2mm. During use, the two ends of the heating wire are connected to a power source via wires. When electricity is applied, the current does work and consumes electrical energy, generating heat.

[0025] The present invention also provides an apparatus for producing glycolide, comprising:

[0026] Reactor;

[0027] A first heating device is installed at the reactor inlet;

[0028] A second heating device is installed inside the reactor;

[0029] The second heating device includes metal particles;

[0030] The metal particle includes a main body and a first side matrix disposed at one end of the main body;

[0031] The cross-sectional area of ​​the main body is smaller than the cross-sectional area of ​​the first side substrate;

[0032] The main body is a hollow structure;

[0033] The main body is equipped with an insulating heating wire inside;

[0034] The insulated heating wire consists of a heating wire and an insulating layer covering the heating wire.

[0035] In this invention, the second heating device includes a layer of metal particles;

[0036] The metal particle layer is formed by multiple metal particles along a certain direction; the metal particle layer is preferably distributed in layers within the production device; the main body of the metal particles is preferably parallel to the flow direction of the material.

[0037] The first side matrix of the metal particles is welded to the inner wall of the reactor;

[0038] The second heating device includes 3 to 100 layers of metal particles.

[0039] Due to its inherent performance limitations, the heating wire cannot be securely welded inside the reactor. Therefore, it needs to be placed within the main body to form metal particles. These metal particles can generate heat when energized, thus greatly increasing the heating area of ​​the material in the reaction section, improving the reaction rate of the material in the reactor, and reducing carbonization and coking during the material reaction process.

[0040] In this invention, the metal particles further include a second side matrix disposed at the other end of the main body; the second side matrix of the metal particles is preferably welded to the inner wall of the reactor.

[0041] The main body is a cylinder;

[0042] The first side substrate and the second side substrate are spheres or quasi-spheres, preferably spheres;

[0043] The ratio of the diameter of the sphere of the metal particle to the length of the main body is 1:(5~2000).

[0044] In this invention, the diameter of the sphere of the metal particle is 1 mm to 100 mm, preferably 30 mm, and the length of the main body of the metal particle is 0.05 to 2 m, preferably 0.2 m.

[0045] The main body of the metal particles is selected from one or more of chromium and its alloys, nickel and its alloys, titanium and its alloys, and iron and its alloys, preferably one or more of stainless steel 304, stainless steel 306, stainless steel 316, stainless steel 2507 or double carbon steel. In one embodiment of the present invention, the main body is made of stainless steel 2507.

[0046] The side matrix of the metal particles is selected from one or more of chromium and its alloys, nickel and its alloys, titanium and its alloys, and iron and its alloys, preferably one or more of stainless steel 304, stainless steel 306, stainless steel 316, stainless steel 2507 or double carbon steel. In one embodiment of the present invention, the side matrix is ​​made of stainless steel 2507.

[0047] The diameter of the heating wire is 0.2–8 mm, preferably 2 mm;

[0048] The resistance of the heating wire is 0.02 to 30 Ω / m, preferably 0.34 Ω / m;

[0049] The interior of the metal particle body preferably contains 1 to 10 heating wires;

[0050] The heating wire is preferably made of one or more of the following materials: iron-chromium-aluminum alloy wire, nickel-chromium alloy wire, and manganese-copper wire.

[0051] The present invention does not have special requirements for the shape of the heating wire, as long as it can generate heat when energized. The heating wire is preferably in the shape of a helical spring.

[0052] The insulating layer completely covers the heating wire. The present invention does not have special requirements for the material of the insulating layer, as long as it is non-conductive, preferably insulating varnish.

[0053] In an embodiment of the invention, the main body of the metal particle is cylindrical, with a length of 0.2m. One end of the main body is connected to a sphere, and the other end is also connected to a sphere. Both spheres have a diameter of 30mm. The main body and spheres of the metal particle are made of stainless steel 2507. Both the main body and spheres have a hollow structure. Inside the metal particle is a nickel-chromium alloy heating wire coated with insulating varnish. The nickel-chromium alloy heating wire is cylindrical and spiral spring-shaped, with a resistance of 0.34Ω / m and a wire diameter of 2mm. During use, the two ends of the heating wire are connected to a power source via wires. When electricity is applied, the current does work and consumes electrical energy, generating heat.

[0054] In this invention, the apparatus for producing glycolide preferably includes a first reactor and a second reactor whose inlet is connected to the outlet of the first reactor;

[0055] The outlet of the first reactor and the inlet of the second reactor are connected by a pipeline, and the product of the first reactor, oligoglycolic acid, enters the second reactor through the pipeline.

[0056] The first reactor is preferably a first reaction vessel; the second reactor is preferably a second reaction vessel.

[0057] The apparatus for producing glycolide of the present invention further includes:

[0058] A first power transmission device is installed at the feed inlet of the first reactor; the first power transmission device is capable of transporting glycolic acid monomers to the first reactor, and the first power transmission device is preferably a melt pump;

[0059] A first heating device is installed at the feed inlet of the first reactor. The first heating device is a heat exchanger for heating a single feed. The discharge port of the first power transmission device and the feed inlet of the first heating device are connected by a pipeline. The outlet of the first heating device and the inlet of the first reactor are connected by a pipeline. The first heating device is preferably a first heat exchanger.

[0060] The second heat exchanger has its inlet connected to the outlet of the first heat exchanger and the inlet of the first reactor via a tee. The second heat exchanger is used for heating the oligomer monomers.

[0061] The first centrifugal pump is installed at the outlet of the second heat exchanger. The first centrifugal pump is used for single-unit circulation heating. The material is transferred to the second heat exchanger through the first centrifugal pump and then enters the first reactor to complete the circulation. The inlet of the first centrifugal pump and the outlet of the second heat exchanger are connected by a pipeline.

[0062] A first collecting device is installed at the small molecule outlet of the first reactor; the first collecting device and the first reactor are connected by a pipeline; the outlet of the first collecting device is the first outlet.

[0063] A first vacuum system is installed at the small molecule outlet of the first collection device. The outlet of the first vacuum system is connected to the feed of the first collection device through a pipeline. The first vacuum system is used to remove small molecules generated in the first reactor, establish a vacuum environment, and improve the polymerization efficiency of glycolic acid monomers. The small molecules removed by the first vacuum system include at least one of water, methanol, and ethanol.

[0064] The apparatus for producing glycolide of the present invention further includes:

[0065] The third heat exchanger is connected to the outlet of the first reactor and the outlet of the first centrifugal pump via a tee; the third heat exchanger is used for heating the pyrolysis of oligoglycolic acid.

[0066] A second centrifugal pump is installed at the outlet of the third heat exchanger. The second centrifugal pump is used for single-unit circulation heating. The material is transferred to the third heat exchanger through the second centrifugal pump and enters the second reactor to complete the circulation. The second centrifugal pump and the third heat exchanger are connected by a pipeline. The inlet of the third heat exchanger and the inlet of the second reactor are connected by a pipeline.

[0067] A second collection device is installed at the small molecule outlet of the second reactor; the second collection device and the second reactor are connected by a pipeline; the outlet of the second collection device is the second outlet.

[0068] The second vacuum system is installed at the small molecule outlet of the second collection device. The outlet of the second vacuum system is connected to the feed of the second collection device through a pipeline. The second vacuum system is used to remove small molecules generated in the second reactor, establish a vacuum environment, and improve the cracking rate of oligoglycolic acid.

[0069] The bottom of the second reactor is the third discharge port, which is used for the discharge of oligomeric glycolic acid residue.

[0070] In this invention, the metal particles are distributed in layers in the first reaction vessel and the second reaction vessel, wherein the number of layers of metal particles in the first reaction vessel is 3 to 100, and the number of layers of metal particles in the second reaction vessel is 3 to 100.

[0071] This invention also provides a method for preparing glycolide, comprising:

[0072] Under energized conditions, metal particles are mixed with glycolic acid oligomers and depolymerized to obtain glycolide;

[0073] The metal particle includes a main body and a first side matrix disposed at one end of the main body;

[0074] The cross-sectional area of ​​the main body is smaller than the cross-sectional area of ​​the first side substrate;

[0075] The main body is a hollow structure;

[0076] The main body is equipped with an insulating heating wire inside;

[0077] The insulated heating wire consists of a heating wire and an insulating layer covering the heating wire.

[0078] In this invention, the preparation process of the glycolide is preferably carried out in a reactor;

[0079] The first side matrix of the metal particles is welded to the inner wall of the reactor to form a layered structure;

[0080] The number of layers in the layered structure is 3 to 100.

[0081] Metal particles can generate heat when energized, thus greatly increasing the heating area of ​​the material in the reaction section, improving the reaction rate of the material in the reactor, and reducing carbonization and coking during the reaction process.

[0082] The metal particles also include a second side matrix disposed at the other end of the main body;

[0083] The main body is a cylinder;

[0084] The first side substrate and the second side substrate are spheres or quasi-spheres, preferably spheres;

[0085] The ratio of the diameter of the sphere of the metal particle to the length of the main body is 1:(5~2000).

[0086] In this invention, the diameter of the sphere of the metal particle is 1 mm to 100 mm, preferably 30 mm, and the length of the main body of the metal particle is 0.05 to 2 m, preferably 0.2 m.

[0087] The main body of the metal particles is selected from one or more of chromium and its alloys, nickel and its alloys, titanium and its alloys, and iron and its alloys, preferably one or more of stainless steel 304, stainless steel 306, stainless steel 316, stainless steel 2507 or double carbon steel. In one embodiment of the present invention, the main body is made of stainless steel 2507.

[0088] The side matrix of the metal particles is selected from one or more of chromium and its alloys, nickel and its alloys, titanium and its alloys, and iron and its alloys, preferably one or more of stainless steel 304, stainless steel 306, stainless steel 316, stainless steel 2507 or double carbon steel. In one embodiment of the present invention, the side matrix is ​​made of stainless steel 2507.

[0089] The diameter of the heating wire is 0.2–8 mm, preferably 2 mm;

[0090] The resistance of the heating wire is 0.02 to 30 Ω / m, preferably 0.34 Ω / m;

[0091] The interior of the metal particle body preferably contains 1 to 10 heating wires;

[0092] The heating wire is preferably made of one or more of the following materials: iron-chromium-aluminum alloy wire, nickel-chromium alloy wire, and manganese-copper wire.

[0093] The present invention does not have special requirements for the shape of the heating wire, as long as it can generate heat after being energized. The heating wire is preferably in the shape of a helical spring.

[0094] The insulating layer completely covers the heating wire. The present invention does not have special requirements for the material of the insulating layer, as long as it is non-conductive, preferably insulating varnish.

[0095] In an embodiment of the invention, the main body of the metal particle is cylindrical, with a length of 0.2m. One end of the main body is connected to a sphere, and the other end is also connected to a sphere. Both spheres have a diameter of 30mm. The main body and spheres of the metal particle are made of stainless steel 2507. Both the main body and spheres have a hollow structure. Inside the metal particle is a nickel-chromium alloy heating wire coated with insulating varnish. The nickel-chromium alloy heating wire is cylindrical and spiral spring-shaped, with a resistance of 0.34Ω / m and a wire diameter of 2mm. During use, the two ends of the heating wire are connected to a power source via wires. When electricity is applied, the current does work and consumes electrical energy, generating heat.

[0096] The volume ratio of the glycolic acid oligomer to the metal particles is (1-50):100, preferably 1:2.

[0097] This invention prepares glycolide using glycolic acid oligomers and metal particles as raw materials. Before mixing the metal particles with the glycolic acid oligomers, the metal particles are heated to 120–280°C, preferably 240–270°C; the heating rate is 30–50°C / min.

[0098] In this invention, the number-average molecular weight of the glycolic acid oligomer is 400–10000 g / mol, preferably 2900–4300 g / mol.

[0099] In this invention, the depolymerization is carried out under vacuum conditions, with a vacuum degree of 10 to 500 Pa, preferably 300 Pa. The depolymerization temperature is 180 to 300 °C, preferably 240 to 270 °C, and the time is 5 to 60 min.

[0100] In this invention, the depolymerization is carried out in the presence of a lubricant; the mass ratio of the lubricant to the glycolic acid oligomer is (0.2-4):1;

[0101] The lubricant includes fluorinated polyethers and solid lubricants;

[0102] Fluorinated polyethers are preferably perfluoropolyethers; solid lubricants include polytetrafluoroethylene, and more preferably include one or more of boron nitride, graphite, fluorinated graphite, molybdenum disulfide, and tungsten disulfide;

[0103] The mass ratio of fluorinated polyether to solid lubricant is (60-90):(10-40); in the solid lubricant, polytetrafluoroethylene accounts for 50-95 wt%.

[0104] Both the polytetrafluoroethylene and the solid lubricant are powders;

[0105] The particle size of the polytetrafluoroethylene powder and the solid lubricant powder is 3–20 μm.

[0106] Introducing high-temperature resistant grease as a lubricant in the pyrolysis section provides good lubrication for the pyrolysis reactor, avoids coking and carbonization of oligoglycolic acid in the reactor, improves the pyrolysis yield of glycolide, and has a self-cleaning effect on the reactor. It can be used for the industrial production of glycolide.

[0107] The present invention does not impose any special restrictions on the source of the glycolic acid oligomer; it can be purchased on the market or prepared according to methods known to those skilled in the art.

[0108] In this invention, the glycolic acid oligomer is prepared by the following method: under energized conditions, glycolic acid monomers, catalysts and metal particles are mixed and subjected to a polycondensation reaction to obtain glycolic acid oligomer.

[0109] The metal particle includes a main body and a first side matrix disposed at one end of the main body;

[0110] The cross-sectional area of ​​the main body is smaller than the cross-sectional area of ​​the first side substrate;

[0111] The main body is a hollow structure;

[0112] The main body is equipped with an insulating heating wire inside;

[0113] The insulated heating wire consists of a heating wire and an insulating layer covering the heating wire.

[0114] In this invention, the preparation process of the glycolide is preferably carried out in a reactor;

[0115] The first side matrix of the metal particles is welded to the inner wall of the reactor to form a layered structure;

[0116] The number of layers in the layered structure is 3 to 100.

[0117] Metal particles can generate heat when energized, thus greatly increasing the heating area of ​​the material in the reaction section, improving the reaction rate of the material in the reactor, and reducing carbonization and coking during the reaction process.

[0118] The metal particles also include a second side matrix disposed at the other end of the main body;

[0119] The main body is a cylinder;

[0120] The first side substrate and the second side substrate are spheres or quasi-spheres, preferably spheres;

[0121] The ratio of the diameter of the sphere of the metal particle to the length of the main body is 1:(5~2000).

[0122] In this invention, the diameter of the sphere of the metal particle is 1 mm to 100 mm, preferably 30 mm, and the length of the main body of the metal particle is 0.05 to 2 m, preferably 0.2 m.

[0123] The main body of the metal particles is selected from one or more of chromium and its alloys, nickel and its alloys, titanium and its alloys, and iron and its alloys, preferably one or more of stainless steel 304, stainless steel 306, stainless steel 316, stainless steel 2507 or double carbon steel. In one embodiment of the present invention, the main body is made of stainless steel 2507.

[0124] The side matrix of the metal particles is selected from one or more of chromium and its alloys, nickel and its alloys, titanium and its alloys, and iron and its alloys, preferably one or more of stainless steel 304, stainless steel 306, stainless steel 316, stainless steel 2507 or double carbon steel. In one embodiment of the present invention, the side matrix is ​​made of stainless steel 2507.

[0125] The diameter of the heating wire is 0.2–8 mm, preferably 2 mm;

[0126] The resistance of the heating wire is 0.02 to 30 Ω / m, preferably 0.34 Ω / m;

[0127] The interior of the metal particle body preferably contains 1 to 10 heating wires;

[0128] The heating wire is preferably made of one or more of the following materials: iron-chromium-aluminum alloy wire, nickel-chromium alloy wire, and manganese-copper wire.

[0129] The present invention does not have any special requirements on the shape of the heating wire, as long as it can generate heat after being energized. The heating wire is preferably in the shape of a spiral spring.

[0130] In an embodiment of the invention, the main body of the metal particle is cylindrical, with a length of 0.2m. One end of the main body is connected to a sphere, and the other end is also connected to a sphere. Both spheres have a diameter of 30mm. The main body and spheres of the metal particle are made of stainless steel 2507. Both the main body and spheres have a hollow structure. Inside the metal particle is a nickel-chromium alloy heating wire coated with insulating varnish. The nickel-chromium alloy heating wire is cylindrical and spiral spring-shaped, with a resistance of 0.34Ω / m and a wire diameter of 2mm. During use, the two ends of the heating wire are connected to a power source via wires. When electricity is applied, the current does work and consumes electrical energy, generating heat.

[0131] The volume ratio of the glycolic acid monomer to the metal particles is (1-50):100, preferably 1:2.

[0132] In this invention, the glycolic acid monomers include glycolic acid, methyl glycolate, or ethyl glycolate; the catalyst is selected from one or more 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. In one embodiment, the catalyst accounts for 0.01 to 10 wt% of the glycolic acid monomers. In another embodiment, the catalyst accounts for 0.1 to 5 wt% of the glycolic acid monomers.

[0133] In one embodiment, the polycondensation reaction is carried out under cyclic heating conditions. In one embodiment, the polycondensation reaction takes 2–20 hours, at a temperature of 100–220°C, and at a pressure of 1–5000 Pa.

[0134] In one embodiment, the polycondensation reaction takes 3 to 10 hours, at a temperature of 120 to 200°C, and at a pressure of 2000 to 4500 Pa.

[0135] In one embodiment, the polycondensation reaction continues for 2–20 hours at a temperature of 100–220°C and a pressure of 1–5000 Pa. In another embodiment, the polycondensation reaction continues for 5–15 hours at a temperature of 120–200°C and a pressure of 100–2000 Pa.

[0136] The metal particles of this invention consist of a main body and a side matrix at one end of the main body, with metal wires inside the main body. When using these metal particles to prepare glycolide, under energized conditions, the metal particles can continuously supply heat to the glycolic acid oligomer, increasing the melting rate of the glycolic acid oligomer and thus accelerating the reaction. Traditional glycolide preparation methods use high-boiling-point solvents during the pyrolysis process, which easily cause product contamination. The introduction of metal particles avoids the use of solvents, yielding high-purity glycolide, while also avoiding the separation process between glycolide and solvent, thus improving production efficiency. Due to the large specific surface area of ​​the metal particles, the problem of excessive residence time and carbonization of glycolic acid oligomers during melting and pyrolysis due to poor mass and heat transfer can be solved, increasing the melting and pyrolysis speed of oligoglycolic acid, reducing production costs, broadening the application prospects of the product, and promoting the industrialization process, thus possessing significant socio-economic value. Attached Figure Description

[0137] Figure 1 This is a diagram of the apparatus for preparing glycolide according to an embodiment of the present invention, wherein M1 is a melt pump, HE1 is a first heat exchanger, R1 is a first reactor, N1 is metal particles in the first reactor, GT1 is a first collection device, V1 is a first vacuum system, E1 is a first outlet, HE2 is a second heat exchanger, M2 is a first centrifugal pump, R2 is a second reactor, N2 is metal particles in the second reactor, HE3 is a third heat exchanger, M3 is a second centrifugal pump, GT2 is a second collection device, E2 is a second outlet, V2 is a second vacuum system, and E3 is a third outlet.

[0138] Figure 2 This is a schematic diagram of the metal particles in an embodiment of the present invention, wherein A and B are the ends of the heating wire, which are connected to the power supply through wires;

[0139] Figure 3 This is a gas chromatogram of glycolide prepared in Example 1 of the present invention. Detailed Implementation

[0140] 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.

[0141] 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.

[0142] The apparatus for preparing glycolide in the embodiments of the present invention is as follows: Figure 1 As shown, M1 is a melt pump for monomer feeding, HE1 is the first heat exchanger for heating the monomer feed, R1 is the first reactor for the oligomerization reaction of glycolic acid monomers, HE2 is the second heat exchanger for heating the monomer oligomerization, M2 is the first centrifugal pump for circulating heating of the monomer, and N1 represents metal particles in the first reactor. The metal particles are as follows: Figure 2 As shown, the metal particles consist of a cylindrical body and spheres connected to both ends of the body. Both the body and spheres are made of 2507 stainless steel. The diameter of the spheres is 30mm, and the length of the body is 0.2m. Both the body and spheres are hollow. Inside each metal particle is a nickel-chromium alloy heating wire coated with insulating varnish. The grade of the nickel-chromium alloy heating wire is Cr20Ni80, and its shape is a cylindrical spiral spring. The wire diameter is 2mm, and the resistance is 0.34Ω / m. A and B are the ends of the heating wire. During use, the A and B ends of the heating wire are connected to the power supply via wires. When energized, the current does work and consumes electrical energy as it flows through the resistor, generating heat. Multiple spheres of the metal particles are welded to the wall of the first reaction vessel, forming a layer of metal particles. This layer is distributed in layers within the production device, with the body of the metal particles parallel to the flow direction of the material. The number of layers is... The system consists of three metal particles that continuously heat the material. GT1 is the first collecting device for collecting small molecules generated from oligomerization of monomers. E1 is the first discharge port for discharging small molecules. V1 is the first vacuum system for the oligomerization reaction of glycolic acid monomers. R2 is the second reactor for the pyrolysis reaction of oligoglycolic acid. HE3 is the third heat exchanger for the pyrolysis of oligoglycolic acid. M3 is the second centrifugal pump for circulating heating of glycolic acid oligomers. N2 consists of metal particles in the second reactor. Multiple metal particles are welded to the wall of the second reactor to form a metal particle layer, with three layers. The metal particles in the second reactor are the same type and have the same distribution as those in the first reactor. The metal particles continuously heat the material. GT2 is the second collecting device for collecting glycolide generated from the pyrolysis of oligoglycolic acid. E2 is the second discharge port for discharging glycolide. V2 is the second vacuum system for the pyrolysis reaction of oligoglycolic acid. E3 is the third discharge port for discharging oligoglycolic acid residue.

[0143] The method for preparing glycolide of the present invention includes:

[0144] 1) Adopting such Figure 1 The reaction apparatus shown delivers glycolic acid monomers and catalysts to reactor R1 via melt pump M1 and heat exchanger HE1. Vacuum is drawn using the first vacuum system V1, and the material is heated using heat exchanger HE2. Under energized conditions, the metal particles generate heat, and the material is transferred to heat exchanger HE2 and layered metal particles via centrifugal pump M2 at the bottom of the reactor for circulating heating to obtain oligoglycolic acid.

[0145] 2) After the oligoglycolic acid melts in reactor R1, it enters reactor R2. In section R2, a vacuum is drawn using the second vacuum system V2, and the material is heated using heat exchanger HE3. Under energized conditions, the metal particles generate heat, and the oligoglycolic acid is transferred to heat exchanger HE3 and the layered metal particles through centrifugal pump M3 at the bottom of the reactor for circulating heating, completing the depolymerization and obtaining glycolide.

[0146] 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.

[0147] 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.

[0148] The acid value of glycolide was tested using a Metrohm 905 potentiometric titrator. The electrode was a non-aqueous glass electrode; the titrant was an anhydrous methanol solution of 0.01 mol / L potassium methoxide; and the solvent was a mixture of dichloromethane and anhydrous methanol at a volume ratio of 4:1.

[0149] Example 1

[0150] 1.1 The reaction apparatus used in this embodiment is shown in the diagram below. Figure 1As shown, 20 kg of 70% glycolic acid and catalyst (10 g zinc oxide + 20 g stannous benzoate) were fed into reactor R1 via melt pump M1 and heat exchanger HE1. The temperature of heat exchanger HE1 was set to 150°C. The material was continuously transported to heat exchanger HE2 for circulation heating via centrifugal pump M2 at the bottom of the reactor. The temperature of heat exchanger HE2 was set to 160°C. The temperature of the reactor was also set to 160°C. The temperature of the metal particles was controlled to 160°C by electricity. The reaction was carried out for 4 hours under normal pressure. Then, a vacuum reaction was carried out using vacuum system V1 at P = 3000 Pa. After 4 hours, the vacuum degree was increased to P = 700 Pa, and the polycondensation reaction was continued for 10 hours to obtain 10.6 kg of oligoglycolic acid.

[0151] The oligoglycolic acid obtained in this invention was analyzed by gel permeation chromatography, and the number average molecular weight of the polyglycolic acid was found to be 3700 g / mol.

[0152] 1.2 The oligoglycolic acid from Example 1.1 was heated to 220°C. After the oligoglycolic acid was completely melted, it was transported through a pipeline to reactor R2. R2 contained 3 kg of high-temperature resistant lubricating grease (the mass ratio of perfluoropolyether oil, polytetrafluoroethylene powder, and boron nitride was 65:30:5). The oligoglycolic acid was continuously transported to heat exchanger HE3 for circulating heating through centrifugal pump M3 at the bottom of the reactor. The temperature of heat exchanger HE3 was set to 230°C, the temperature of reactor R2 was set to 230°C, and the temperature of the metal particles was controlled by electricity at 240°C. The feed rate was 2 kg / h. Vacuum was evacuated using the V2 vacuum system to carry out the depolymerization reaction at P = 300 Pa. After the feeding was completed, the depolymerization reaction continued. After 2 hours, the glycolide stopped distilling out, and the reaction was stopped. The pyrolysis residue was discharged from the system through outlet E3, yielding 9.9 kg of glycolide, with a yield of 92.7%.

[0153] Gas chromatography was used to analyze the glycolide prepared in Example 1. The results showed that the glycolide purity was 98.3%, with the remainder consisting of light components (glycolic acid monomers) and heavy components (glycolic acid oligomers), as shown in Table 1. Figure 3 As shown in Table 1, the gas chromatographic data of the glycolide prepared in Example 1 of this invention are as follows: Figure 3 This is a gas chromatogram of the glycolide prepared in Example 1 of the present invention.

[0154] Table 1 Gas chromatographic data of glycolide prepared in Example 1 of this invention

[0155] name Duration of stay area %area 3.028 29 0.50 4.178 55 0.93 Glycolide 4.542 5797 98.31 4.595 6 0.10 4.692 10 0.17

[0156] The acidity of the glycolide prepared in Example 1 of this invention was tested according to the above method. The test result showed that the acid value of glycolide was 28 ppm.

[0157] Comparative Example 1

[0158] 1.1 The reaction apparatus used in this comparative example is shown in the diagram below. Figure 1 As shown, the experimental procedure was carried out according to the steps in Example 1, except that solid metal particles were used instead of the metal particles in Example 1. The metal particles in this comparative example were made of stainless steel 2507. 20 kg of 70% glycolic acid and catalyst (10 g zinc oxide + 20 g stannous benzoate) were fed into reactor R1 via melt pump M1 and heat exchanger HE1. The temperature of heat exchanger HE1 was set to 150°C. The material was continuously pumped to heat exchanger HE2 via centrifugal pump M2 at the bottom of the reactor for circulating heating. The temperature of heat exchanger HE2 was set to 160°C, and the reactor temperature was also set to 160°C. The reaction was carried out under normal pressure for 4 hours. Then, a vacuum was applied using vacuum system V1 to induce a polycondensation reaction at P = 3000 Pa. After 4 hours, the vacuum was increased to P = 700 Pa, and the polycondensation reaction continued for 10 hours, yielding 10.7 kg of oligoglycolic acid.

[0159] The oligoglycolic acid obtained in this comparative example was analyzed by gel permeation chromatography, and the number average molecular weight of the polyglycolic acid was determined to be 1800 g / mol.

[0160] 1.2 The oligoglycolic acid in Comparative Example 1.1 was heated to 220℃. After the oligoglycolic acid was completely melted, it was transported through a pipeline to reactor R2. R2 contained 3 kg of high-temperature resistant lubricating grease (the mass ratio of perfluoropolyether oil, polytetrafluoroethylene powder, and boron nitride was 65:30:5). The oligoglycolic acid was continuously transported to heat exchanger HE3 for circulating heating through centrifugal pump M3 at the bottom of the reactor. The temperature of heat exchanger HE3 was set to 230℃, the temperature of reactor R2 was set to 230℃, and the feed rate was 2 kg / h. Vacuum was applied using the V2 vacuum system to carry out the depolymerization reaction at P = 300 Pa. After the feeding was completed, the depolymerization reaction continued. The reaction was stopped after 2 hours. The pyrolysis residue was discharged from the system through outlet E3, yielding 8.3 kg of glycolide, with a yield of 77.7%.

[0161] Gas chromatography was used to test the glycolide prepared in this comparative example. The results showed that the glycolide purity was 87.3%, with the remainder being light components (glycolic acid monomers) and heavy components (glycolic acid oligomers).

[0162] The acidity of the glycolide prepared in this comparative example was tested according to the above method. The test result showed that the acid value of glycolide was 358 ppm.

[0163] Comparative Example 2

[0164] The reaction apparatus used in this comparative example is shown in the diagram below. Figure 1As shown, the experimental procedure was carried out according to the steps in Example 1. The difference from Example 1 is that an electric heating wire was used instead of the metal particles in Example 1. The electric heating wire in this comparative example is the same as the electric heating wire in the metal particles of Example 1. During the experiment, it was found that due to the high viscosity of the material, the electric heating wire broke during the cyclic heating process, causing partial damage to the equipment and interrupting the reaction. Therefore, it is not feasible to use a heating wire instead of the hollow heatable metal ball in the reaction system of the present invention.

[0165] Example 2

[0166] 2.1 The reaction apparatus used in this embodiment is shown in the diagram below. Figure 1 As shown, 20 kg of 70% glycolic acid and catalyst (10 g zinc chloride + 20 g stannous chloride) were fed into reactor R1 via melt pump M1 and heat exchanger HE1. The temperature of heat exchanger HE1 was set to 145°C. The material was continuously transported to heat exchanger HE2 for circulation heating via centrifugal pump M2 at the bottom of the reactor. The temperature of heat exchanger HE2 was set to 150°C. The temperature of the reactor was also set to 150°C. The temperature of the metal particles was controlled by electricity at 160°C. The reaction was carried out for 4 hours under normal pressure. Then, a vacuum was drawn using vacuum system V1 to carry out a polycondensation reaction at P = 3000 Pa. After 4 hours, the vacuum was increased to P = 700 Pa, and the polycondensation reaction was continued for 12 hours to obtain 10.5 kg of oligoglycolic acid.

[0167] The oligoglycolic acid obtained in this invention was analyzed by gel permeation chromatography, and the number average molecular weight of the polyglycolic acid was determined to be 3300 g / mol.

[0168] 2.2 The oligoglycolic acid from Example 2.1 was heated to 220°C. After the oligoglycolic acid was completely melted, it was transported through a pipeline to reactor R2. R2 contained 3 kg of high-temperature resistant lubricating grease (the mass ratio of perfluoropolyether oil, polytetrafluoroethylene powder, and boron nitride was 70:25:5). The oligoglycolic acid was continuously transported to heat exchanger HE3 for circulating heating through centrifugal pump M3 at the bottom of the reactor. The temperature of heat exchanger HE3 was set to 240°C, the temperature of reactor R2 was set to 240°C, and the temperature of the metal particles was controlled to 240°C by electricity. The feed rate was 2 kg / h, and P = 300 Pa. After the feeding was completed, the depolymerization reaction continued. After 2 hours, the glycolide stopped distilling out, and the reaction was stopped. The pyrolysis residue was discharged from the system through outlet E3, yielding 10.1 kg of glycolide, with a yield of 94.5%.

[0169] The glycolide prepared in Example 2 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 monomers) and heavy components (glycolic acid oligomers).

[0170] The acidity of the glycolide prepared in Example 2 of this invention was tested according to the above method. The test result showed that the acid value of glycolide was 36 ppm.

[0171] Example 3

[0172] 3.1 The reaction apparatus used in this embodiment is shown in the diagram below. Figure 1 As shown, 20 kg of 70% glycolic acid and catalyst (10 g antimony trioxide + 20 g stannous octoate) were fed into reactor R1 via melt pump M1 and heat exchanger HE1. The temperature of heat exchanger HE1 was set to 160°C. The material was continuously transported to heat exchanger HE2 for circulation heating via centrifugal pump M2 at the bottom of the reactor. The temperature of heat exchanger HE2 was set to 170°C. The temperature of the reactor was also set to 170°C. The temperature of the metal particles was controlled to 170°C by electricity. The reaction was carried out for 2 hours under normal pressure. Then, a vacuum reaction was carried out using vacuum system V1 at P = 3000 Pa. After 4 hours, the vacuum degree was increased to P = 700 Pa, and the polycondensation reaction was continued for 9 hours to obtain 10.4 kg of oligoglycolic acid.

[0173] The oligoglycolic acid obtained in this invention was analyzed by gel permeation chromatography, and the number average molecular weight of the polyglycolic acid was found to be 4200 g / mol.

[0174] 3.2 The oligoglycolic acid from Example 3.1 was heated to 230°C. After the oligoglycolic acid was completely melted, it was transported through a pipeline to reactor R2. R2 contained 4 kg of high-temperature resistant lubricating grease (the mass ratio of perfluoropolyether oil, polytetrafluoroethylene powder, and boron nitride was 75:20:5). The oligoglycolic acid was continuously transported to heat exchanger HE3 for circulating heating through centrifugal pump M3 at the bottom of the reactor. The temperature of heat exchanger HE3 was set to 250°C, the temperature of reactor R2 was set to 250°C, and the temperature of the metal particles was controlled to 250°C by electricity. The feed rate was 3 kg / h. Vacuum was evacuated using the V2 vacuum system to carry out the depolymerization reaction at P = 300 Pa. After the feeding was completed, the depolymerization reaction continued. After 1.5 h, the glycolide stopped distilling out, and the reaction was stopped. The pyrolysis residue was discharged from the system through outlet E3, yielding 10 kg of glycolide with a yield of 93.6%.

[0175] The glycolide prepared in Example 3 of this invention was subjected to gas chromatography testing. The test results showed that the glycolide purity was 98.5%, with the remainder being light components (glycolic acid monomers) and heavy components (glycolic acid oligomers).

[0176] The acidity of the glycolide prepared in Example 3 of this invention was tested according to the above method. The test result showed that the acid value of glycolide was 29 ppm.

[0177] Example 4

[0178] 4.1 The reaction apparatus used in this embodiment is shown in the diagram below. Figure 1As shown, 20 kg of 70% glycolic acid and catalyst (10 g antimony acetate + 20 g tin oxide) were fed into reactor R1 via melt pump M1 and heat exchanger HE1. The temperature of heat exchanger HE1 was set to 170°C. The material was continuously transported to heat exchanger HE2 for circulation heating via centrifugal pump M2 at the bottom of the reactor. The temperature of heat exchanger HE2 was set to 180°C. The temperature of the reactor was also set to 180°C. The temperature of the metal particles was controlled to 180°C by electricity. The reaction was carried out for 2 hours under normal pressure. Then, a vacuum reaction was carried out using vacuum system V1 at P = 3000 Pa. After 4 hours, the vacuum degree was increased to P = 700 Pa, and the polycondensation reaction was continued for 6 hours to obtain 10.2 kg of oligomeric glycolic acid.

[0179] The oligoglycolic acid obtained in this invention was analyzed by gel permeation chromatography, and the number average molecular weight of the polyglycolic acid was found to be 4300 g / mol.

[0180] 4.2 The oligoglycolic acid from Example 4.1 was heated to 230°C. After the oligoglycolic acid was completely melted, it was transported through a pipeline to reactor R2. R2 contained 4 kg of high-temperature resistant lubricating grease (the mass ratio of perfluoropolyether oil, polytetrafluoroethylene powder, and graphite was 80:17:3). The oligoglycolic acid was continuously transported to heat exchanger HE3 for circulating heating through centrifugal pump M3 at the bottom of the reactor. The temperature of heat exchanger HE3 was set to 260°C, the temperature of the reactor was set to 260°C, and the temperature of the metal particles was controlled by electricity at 260°C. The feed rate was 3 kg / h. Vacuum was evacuated using the V2 vacuum system to carry out the depolymerization reaction at P = 300 Pa. After the feeding was completed, the depolymerization reaction continued. After 1 hour, the glycolide stopped distilling out, and the reaction was stopped. The pyrolysis residue was discharged from the system through outlet E3, yielding 9.8 kg of glycolide, with a yield of 91.8%.

[0181] The glycolide prepared in Example 4 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 monomers) and heavy components (glycolic acid oligomers).

[0182] The acidity of the glycolide prepared in Example 4 of this invention was tested according to the above method. The test result showed that the acid value of glycolide was 21 ppm.

[0183] Example 5

[0184] 5.1 The reaction apparatus used in this embodiment is shown in the diagram below. Figure 1As shown, 20 kg of 100% methyl glycolate and catalyst (10 g zinc acetate + 20 g tin acetate) were fed into reactor R1 via melt pump M1 and heat exchanger HE1. The temperature of heat exchanger HE1 was set to 140°C. The material was continuously transported to heat exchanger HE2 for circulation heating via centrifugal pump M2 at the bottom of the reactor. The temperature of heat exchanger HE2 was set to 140°C. The temperature of the reactor was also set to 140°C. The temperature of the metal particles was controlled to 140°C by electricity. The reaction was carried out for 4 hours under normal pressure. Then, a vacuum was drawn using vacuum system V1 to carry out a polycondensation reaction at P = 6000 Pa. After 4 hours, the vacuum was increased to P = 700 Pa, and the polycondensation reaction was continued for 12 hours to obtain 12.9 kg of oligomeric glycolic acid.

[0185] The oligoglycolic acid obtained in this invention was analyzed by gel permeation chromatography, and the number average molecular weight of the polyglycolic acid was found to be 2900 g / mol.

[0186] 5.2 The oligoglycolic acid from Example 5.1 was heated to 230°C. After the oligoglycolic acid was completely melted, it was transported through a pipeline to reactor R2. R2 contained 5 kg of high-temperature resistant lubricating grease (the mass ratio of perfluoropolyether oil, polytetrafluoroethylene powder, and graphite was 75:19:6). The oligoglycolic acid was continuously transported to heat exchanger HE3 for circulating heating through centrifugal pump M3 at the bottom of the reactor. The temperature of heat exchanger HE3 was set to 230°C, the temperature of reactor R2 was set to 230°C, and the temperature of the metal particles was controlled by electricity at 240°C. The feed rate was 2 kg / h. Vacuum was evacuated using the V2 vacuum system to carry out the depolymerization reaction at P = 300 Pa. After the feeding was completed, the depolymerization reaction continued. After 2 hours, the glycolide stopped distilling out, and the reaction was stopped. The pyrolysis residue was discharged from the system through outlet E3, yielding 11.9 kg of glycolide, with a yield of 92.4%.

[0187] The glycolide prepared in Example 5 of this invention was subjected to gas chromatography testing. The test results showed that the glycolide purity was 96.1%, with the remainder being light components (glycolic acid monomers) and heavy components (glycolic acid oligomers).

[0188] The acidity of the glycolide prepared in Example 5 of this invention was tested according to the above method. The test result showed that the acid value of glycolide was 31 ppm.

[0189] Example 6

[0190] 6.1 The reaction apparatus used in this embodiment is shown in the diagram below. Figure 1As shown, 20 kg of 100% methyl glycolate and catalyst (10 g stannous chloride + 20 g zinc acetate) were fed into reactor R1 via melt pump M1 and heat exchanger HE1. The temperature of heat exchanger HE1 was set to 150°C. The material was continuously pumped to heat exchanger HE2 via centrifugal pump M2 at the bottom of the reactor for circulating heating. The temperature of heat exchanger HE2 was set to 150°C. The temperature of the reactor was also set to 150°C. The temperature of the metal particles was controlled to 150°C by electricity. The reaction was carried out for 4 hours under normal pressure. Then, a vacuum was drawn using vacuum system V1 to carry out a polycondensation reaction at P = 6000 Pa. After 4 hours, the vacuum was increased to P = 700 Pa, and the polycondensation reaction was continued for 12 hours to obtain 12.8 kg of oligomeric glycolic acid.

[0191] The oligoglycolic acid obtained in this invention was analyzed by gel permeation chromatography, and the number average molecular weight of the polyglycolic acid was determined to be 3200 g / mol.

[0192] 6.2 The oligoglycolic acid from Example 6.1 was heated to 230°C. After the oligoglycolic acid was completely melted, it was transported through a pipeline to reactor R2. R2 contained 5 kg of high-temperature resistant lubricating grease (the mass ratio of perfluoropolyether oil, polytetrafluoroethylene powder, and graphite was 70:22:8). The oligoglycolic acid was continuously transported to heat exchanger HE3 for circulating heating through centrifugal pump M3 at the bottom of the reactor. The temperature of heat exchanger HE3 was set to 240°C, the temperature of reactor R2 was set to 240°C, and the temperature of the metal particles was controlled to 240°C by electricity. The feed rate was 2 kg / h. Vacuum was evacuated using the V2 vacuum system to carry out the depolymerization reaction at P = 300 Pa. After the feeding was completed, the depolymerization reaction continued. After 2 hours, the glycolide stopped distilling out, and the reaction was stopped. The pyrolysis residue was discharged from the system through outlet E3, yielding 11.8 kg of glycolide, with a yield of 91.6%.

[0193] The glycolide prepared in Example 6 of this invention was subjected to gas chromatography. The test results showed that the glycolide purity was 96.3%, with the remainder being light components (glycolic acid monomers) and heavy components (glycolic acid oligomers).

[0194] The acidity of the glycolide prepared in Example 6 of this invention was tested according to the above method, and the result showed that the acid value of glycolide was 24 ppm.

[0195] Example 7

[0196] 7.1 The reaction apparatus used in this embodiment is shown in the diagram below. Figure 1As shown, 20 kg of 100% methyl glycolate and catalyst (10 g zinc lactate + 20 g stannous benzoate) were fed into reactor R1 via melt pump M1 and heat exchanger HE1. The temperature of heat exchanger HE1 was set to 160°C. The material was continuously transported to heat exchanger HE2 for circulation heating via centrifugal pump M2 at the bottom of the reactor. The temperature of heat exchanger HE2 was set to 160°C. The temperature of the reactor was also set to 160°C. The temperature of the metal particles was controlled to 160°C by electricity. The reaction was carried out for 3 hours under normal pressure. Then, a vacuum reaction was carried out using vacuum system V1 at P = 6000 Pa. After 4 hours, the vacuum degree was increased to P = 700 Pa, and the polycondensation reaction was continued for 12 hours to obtain 12.6 kg of oligomeric glycolic acid.

[0197] The oligoglycolic acid obtained in this invention was analyzed by gel permeation chromatography, and the number average molecular weight of the polyglycolic acid was found to be 3500 g / mol.

[0198] 7.2 The oligoglycolic acid from Example 7.1 was heated to 230°C. After the oligoglycolic acid was completely melted, it was transported through a pipeline to reactor R2. R2 contained 6 kg of high-temperature resistant lubricating grease (the mass ratio of perfluoropolyether oil, polytetrafluoroethylene powder, and molybdenum disulfide was 65:26:9). The oligoglycolic acid was continuously transported to heat exchanger HE3 for circulating heating through centrifugal pump M3 at the bottom of the reactor. The temperature of heat exchanger HE3 was set to 250°C, the temperature of reactor R2 was set to 250°C, and the temperature of the metal particles was controlled to 250°C by electricity. The feed rate was 2 kg / h. Vacuum was evacuated using the V2 vacuum system to carry out the depolymerization reaction at P = 300 Pa. After the feeding was completed, the depolymerization reaction continued. After 1.5 h, the glycolide stopped distilling out, and the reaction was stopped. The pyrolysis residue was discharged from the system through outlet E3, yielding 12 kg of glycolide, with a yield of 93.2%.

[0199] The glycolide prepared in Example 7 of this invention was subjected to gas chromatography. The test results showed that the glycolide purity was 97.2%, with the remainder being light components (glycolic acid monomers) and heavy components (glycolic acid oligomers).

[0200] The acidity of the glycolide prepared in Example 7 of this invention was tested according to the above method. The test result showed that the acid value of glycolide was 19 ppm.

[0201] Example 8

[0202] 8.1 The reaction apparatus used in this embodiment is shown in the diagram below. Figure 1As shown, 20 kg of 100% methyl glycolate and catalyst (10 g antimony acetate + 20 g stannous octoate) were fed into reactor R1 via melt pump M1 and heat exchanger HE1. The temperature of heat exchanger HE1 was set to 170°C. The material was continuously transported to heat exchanger HE2 for circulation heating via centrifugal pump M2 at the bottom of the reactor. The temperature of heat exchanger HE2 was set to 170°C. The temperature of the reactor was also set to 170°C. The temperature of the metal particles was controlled to 170°C by electricity. The reaction was carried out for 2 hours under normal pressure. Then, a vacuum was drawn using vacuum system V1 to carry out a polycondensation reaction at P = 6000 Pa. After 4 hours, the vacuum was increased to P = 700 Pa, and the polycondensation reaction was continued for 11 hours to obtain 12.4 kg of oligomeric glycolic acid.

[0203] The oligoglycolic acid obtained in this invention was analyzed by gel permeation chromatography, and the number average molecular weight of the polyglycolic acid was determined to be 3900 g / mol.

[0204] 8.2 The oligoglycolic acid from Example 8.1 was heated to 230°C. After the oligoglycolic acid was completely melted, it was transported through a pipeline to reactor R2. R2 contained 6 kg of high-temperature resistant lubricating grease (the mass ratio of perfluoropolyether oil, polytetrafluoroethylene powder, and molybdenum disulfide was 60:33:7). The oligoglycolic acid was continuously transported to heat exchanger HE3 for circulating heating through centrifugal pump M3 at the bottom of the reactor. The temperature of heat exchanger HE3 was set to 260°C, the temperature of reactor R2 was set to 260°C, and the temperature of the metal particles was controlled to 260°C by electricity. The feed rate was 3 kg / h. Vacuum was evacuated using the V2 vacuum system to carry out the depolymerization reaction at P = 300 Pa. After the feeding was completed, the depolymerization reaction continued. After 1 hour, the glycolide stopped distilling out, and the reaction was stopped. The pyrolysis residue was discharged from the system through outlet E3, yielding 12.2 kg of glycolide, with a yield of 94.7%.

[0205] The glycolide prepared in Example 8 of this invention was subjected to gas chromatography. The test results showed that the glycolide purity was 96.6%, and the remainder consisted of light components (glycolic acid monomers) and heavy components (glycolic acid oligomers).

[0206] The acidity of the glycolide prepared in Example 8 of this invention was tested according to the above method. The test result showed that the acid value of glycolide was 28 ppm.

[0207] Example 9

[0208] 9.1 The reaction apparatus used in this embodiment is shown in the diagram below. Figure 1As shown, 20 kg of 100% ethyl glycolate and catalyst (20 g antimony chloride + 40 g stannous benzoate) were fed into reactor R1 via melt pump M1 and heat exchanger HE1. The temperature of heat exchanger HE1 was set to 140°C. The material was continuously pumped to heat exchanger HE2 via centrifugal pump M2 at the bottom of the reactor for circulating heating. The temperature of heat exchanger HE2 was set to 140°C. The temperature of the reactor was also set to 140°C. The temperature of the metal particles was controlled at 140°C by electricity. The reaction was carried out under normal pressure for 4 hours. Then, the heat exchanger, reactor, and metal particles were heated to 160°C respectively. Vacuum was applied using vacuum system V1 to carry out polycondensation reaction at P = 4000 Pa. After 4 hours, the vacuum was increased to P = 700 Pa, and the polycondensation reaction was continued for 10 hours to obtain 11.2 kg of oligoglycolic acid.

[0209] The oligoglycolic acid obtained in this invention was analyzed by gel permeation chromatography, and the number average molecular weight of the polyglycolic acid was found to be 3100 g / mol.

[0210] 9.2 The oligoglycolic acid from Example 9.1 was heated to 230°C. After the oligoglycolic acid was completely melted, it was transported through a pipeline to reactor R2. R2 contained 5.5 kg of high-temperature resistant lubricating grease (the mass ratio of perfluoropolyether oil, polytetrafluoroethylene powder, and molybdenum disulfide was 63:32:5). The oligoglycolic acid was continuously transported to heat exchanger HE3 for circulating heating through centrifugal pump M3 at the bottom of the reactor. The temperature of heat exchanger HE3 was set to 240°C, the temperature of reactor R2 was set to 240°C, and the temperature of the metal particles was controlled to 240°C by electricity. The feed rate was 2 kg / h. Vacuum was evacuated using the V2 vacuum system to carry out the depolymerization reaction at P = 300 Pa. After the feeding was completed, the depolymerization reaction continued. After 2 hours, the glycolide stopped distilling out, and the reaction was stopped. The pyrolysis residue was discharged from the system through outlet E3, yielding 10.4 kg of glycolide, with a yield of 93.3%.

[0211] The glycolide prepared in Example 9 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 monomers) and heavy components (glycolic acid oligomers).

[0212] The acidity of the glycolide prepared in Example 9 of this invention was tested according to the above method. The test result showed that the acid value of glycolide was 33 ppm.

[0213] Example 10

[0214] 10.1 The reaction apparatus used in this embodiment is shown in the diagram below. Figure 1As shown, 20 kg of 100% ethyl glycolate and catalyst (20 g antimony trioxide + 40 g zinc acetate) were fed into reactor R1 via melt pump M1 and heat exchanger HE1. The temperature of heat exchanger HE1 was set to 150°C. The material was continuously pumped to heat exchanger HE2 via centrifugal pump M2 at the bottom of the reactor for circulation heating. The temperature of heat exchanger HE2 was set to 150°C. The temperature of the reactor was also set to 150°C. The temperature of the metal particles was controlled at 150°C by electricity. The reaction was carried out for 3 hours under normal pressure. Then, the heat exchanger, reactor, and metal particles were heated to 160°C. Vacuum was applied using vacuum system V1 to carry out polycondensation reaction at P = 4000 Pa. After 4 hours, the vacuum was increased to P = 700 Pa, and the polycondensation reaction was continued for 12 hours to obtain 11.1 kg of oligoglycolic acid.

[0215] The oligoglycolic acid obtained in this invention was analyzed by gel permeation chromatography, and the number average molecular weight of the polyglycolic acid was determined to be 3600 g / mol.

[0216] 10.2 The oligoglycolic acid from Example 10.1 was heated to 230°C. After the oligoglycolic acid was completely melted, it was transported through a pipeline to reactor R2. R2 contained 4.5 kg of high-temperature resistant lubricating grease (the mass ratio of perfluoropolyether oil, polytetrafluoroethylene powder, and tungsten disulfide was 66:31:3). The oligoglycolic acid was continuously transported to heat exchanger HE3 for circulating heating through centrifugal pump M3 at the bottom of the reactor. The temperature of heat exchanger HE3 was set to 250°C, the temperature of reactor R2 was set to 250°C, and the temperature of the metal particles was controlled to 250°C by electricity. The feed rate was 2 kg / h. Vacuum was evacuated using the V2 vacuum system to carry out the depolymerization reaction at P = 300 Pa. After the feeding was completed, the depolymerization reaction continued. After 1.5 h, the glycolide stopped distilling out, and the reaction was stopped. The pyrolysis residue was discharged from the system through outlet E3, yielding 10.5 kg of glycolide, with a yield of 94.2%.

[0217] The glycolide prepared in Example 10 of this invention was subjected to gas chromatography testing. The test results showed that the glycolide purity was 96.5%, with the remainder being light components (glycolic acid monomers) and heavy components (glycolic acid oligomers).

[0218] The acidity of the glycolide prepared in Example 10 of this invention was tested according to the above method. The test result showed that the acid value of glycolide was 26 ppm.

[0219] Example 11

[0220] 11.1 The reaction apparatus used in this embodiment is shown in the diagram below. Figure 1As shown, 20 kg of 100% ethyl glycolate and catalyst (20 g stannous chloride + 40 g zinc acetylacetonate) were fed into reactor R1 via melt pump M1 and heat exchanger HE1. The temperature of heat exchanger HE1 was set to 160°C. The material was continuously pumped to heat exchanger HE2 via centrifugal pump M2 at the bottom of the reactor for circulation heating. The temperature of heat exchanger HE2 was set to 160°C. The temperature of the reactor was also set to 160°C. The temperature of the metal particles was controlled at 160°C by electricity. The reaction was carried out for 3 hours under normal pressure. Then, the heat exchanger, reactor, and metal particles were heated to 170°C. Vacuum was applied using vacuum system V1 to carry out polycondensation reaction at P = 4000 Pa. After 4 hours, the vacuum was increased to P = 700 Pa, and the polycondensation reaction was continued for 10 hours to obtain 10.9 kg of oligoglycolic acid.

[0221] The oligoglycolic acid obtained in this invention was analyzed by gel permeation chromatography, and the number average molecular weight of the polyglycolic acid was determined to be 3900 g / mol.

[0222] 11.2 The oligoglycolic acid from Example 11.1 was heated to 230°C. After the oligoglycolic acid was completely melted, it was transported through a pipeline to reactor R2. R2 contained 3.5 kg of high-temperature resistant lubricating grease (the mass ratio of perfluoropolyether oil, polytetrafluoroethylene powder, and tungsten disulfide was 69:27:4). The oligoglycolic acid was continuously transported to heat exchanger HE3 for circulating heating through centrifugal pump M3 at the bottom of the reactor. The temperature of heat exchanger HE3 was set to 260°C, the temperature of reactor R2 was set to 260°C, and the temperature of the metal particles was controlled to 260°C by electricity. The feed rate was 3 kg / h. Vacuum was evacuated using the V2 vacuum system to carry out the depolymerization reaction at P = 300 Pa. After the feeding was completed, the depolymerization reaction continued. After 1 hour, the glycolide stopped distilling out, and the reaction was stopped. The pyrolysis residue was discharged from the system through outlet E3, yielding 10.7 kg of glycolide, with a yield of 96.1%.

[0223] The glycolide prepared in Example 11 of this invention was subjected to gas chromatography testing. The test results showed that the glycolide purity was 97.4%, with the remainder being light components (glycolic acid monomers) and heavy components (glycolic acid oligomers).

[0224] 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.

[0225] Example 12

[0226] 12.1 The reaction apparatus used in this embodiment is shown in the diagram below. Figure 1As shown, 20 kg of 100% ethyl glycolate and catalyst (40 g stannous benzoate + 80 g antimony acetate) were fed into reactor R1 via melt pump M1 and heat exchanger HE1. The temperature of heat exchanger HE1 was set to 170°C. The material was continuously transported to heat exchanger HE2 for circulation heating via centrifugal pump M2 at the bottom of the reactor. The temperature of heat exchanger HE2 was set to 170°C. The temperature of the reactor was also set to 170°C. The temperature of the metal particles was controlled to 170°C by electricity. The reaction was carried out for 2 hours under normal pressure. Then, a vacuum was drawn using vacuum system V1 to carry out a polycondensation reaction at P = 4000 Pa. After 4 hours, the vacuum was increased to P = 700 Pa, and the polycondensation reaction was continued for 12 hours to obtain 10.8 kg of oligoglycolic acid.

[0227] The oligoglycolic acid obtained in this invention was analyzed by gel permeation chromatography, and the number average molecular weight of the polyglycolic acid was found to be 4100 g / mol.

[0228] 12.2 The oligoglycolic acid from Example 12.1 was heated to 230°C. After the oligoglycolic acid was completely melted, it was transported through a pipeline to reactor R2. R2 contained 2.5 kg of high-temperature resistant lubricating grease (the mass ratio of perfluoropolyether oil, polytetrafluoroethylene powder, and tungsten disulfide was 72:22:6). The oligoglycolic acid was continuously transported to heat exchanger HE3 for circulating heating through centrifugal pump M3 at the bottom of the reactor. The temperature of heat exchanger HE3 was set to 270°C, the temperature of reactor R2 was set to 270°C, and the temperature of the metal particles was controlled to 270°C by electricity. The feed rate was 3 kg / h. Vacuum was evacuated using the V2 vacuum system to carry out the depolymerization reaction at P = 300 Pa. After the feeding was completed, the depolymerization reaction continued. After 0.5 h, the glycolide stopped distilling out, and the reaction was stopped. The pyrolysis residue was discharged from the system through outlet E3, yielding 10.2 kg of glycolide, with a yield of 91.5%.

[0229] Gas chromatography was used to test the glycolide prepared in Example 12 of the present invention. The test results showed that the glycolide purity was 96.8%, and the remainder consisted of light components (glycolic acid monomers) and heavy components (glycolic acid oligomers).

[0230] The acidity of the glycolide prepared in Example 12 of this invention was tested according to the above method. The test result showed that the acid value of glycolide was 22 ppm.

[0231] 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 preparing glycolide, characterized in that, include: Under energized conditions, metal particles are heated to 120~280℃, mixed with glycolic acid oligomers, and depolymerized to obtain glycolide. The metal particle includes a main body and a first side matrix disposed at one end of the main body; The cross-sectional area of ​​the main body is smaller than the cross-sectional area of ​​the first side substrate; The main body is a hollow structure; The main body is equipped with an insulating heating wire inside; The insulated heating wire consists of a heating wire and an insulating layer covering the heating wire; The preparation process of the glycolide is carried out in a reactor; the first side matrix of the metal particles is welded to the inner wall of the reactor, and the main body of the metal particles is parallel to the flow direction of the material to form a layered structure; the number of layers in the layered structure is 3 to 100.

2. The method for preparing glycolide according to claim 1, characterized in that, The metal particles also include a second side matrix disposed at the other end of the main body.

3. The method for preparing glycolide according to claim 2, characterized in that, The main body is a cylinder; The first and second side substrates are spheres or quasi-spheres.

4. The method for preparing glycolide according to claim 3, characterized in that, The diameter of the sphere of the metal particle is 1mm to 100mm, and the length of the main body is 0.05 to 2m; The main body of the metal particles is selected from one or more of chromium and its alloys, nickel and its alloys, titanium and its alloys, and iron and its alloys. The side matrix of the metal particles is selected from one or more of chromium and its alloys, nickel and its alloys, titanium and its alloys, and iron and its alloys.

5. The method for preparing glycolide according to any one of claims 1-4, characterized in that, The diameter of the heating wire is 0.2~8mm; The resistance of the heating wire is 0.02~30Ω / m.

6. The method for preparing glycolide according to claim 1, characterized in that, The depolymerization is carried out under vacuum conditions, with a vacuum degree of 10~500Pa, a depolymerization temperature of 180~300℃, and a time of 5~60min; The depolymerization occurs in the presence of a lubricant. The lubricant includes fluorinated polyethers and solid lubricants; The number-average molecular weight of the glycolic acid oligomer is 400~10000 g / mol.

7. An apparatus for producing glycolide, characterized in that, include: Reactor; A first heating device is installed at the reactor inlet; A second heating device is installed inside the reactor; The second heating device includes metal particles; The metal particle includes a main body and a first side matrix disposed at one end of the main body; The cross-sectional area of ​​the main body is smaller than the cross-sectional area of ​​the first side substrate; The main body is a hollow structure; The main body is equipped with an insulating heating wire inside; The insulated heating wire consists of a heating wire and an insulating layer covering the heating wire.

8. The apparatus for producing glycolide according to claim 7, characterized in that, The second heating device includes a layer of metal particles; The metal particle layer is formed by multiple metal particles along a certain direction.

9. The apparatus for producing glycolide according to claim 8, characterized in that, The second heating device includes 3 to 100 layers of metal particles.

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