A method and apparatus for the production of polyglycolic acid

Abstract

The application provides a preparation method of polyglycolic acid, comprising the following steps: melting glycolide and an initiator, then entering a prepolymerization section of a reaction kettle for prepolymerization, then entering a polymerization section of the reaction kettle for polymerization, and finally performing devolatilization to obtain polyglycolic acid; the prepolymerization section and the polymerization section are respectively filled with a supported catalyst. The application also provides a preparation device of polyglycolic acid. The preparation method provided by the application adopts a fixed bed catalyst, the product is free of metal catalyst residues, the separation problem of the catalyst and the product is solved, and the catalyst can be reused; and the prepolymerization and the polymerization of the glycolide are performed in the same device by adopting a pipeline type reaction kettle, and the process is continuous, the pipeline blockage problem caused by material conveying between reactors is solved, the material quality instability problem caused by the frequent monomer explosive polymerization of the conventional kettle type polymerization is solved, and the continuous production of polyglycolic acid is realized.

Description

Technical Field

[0001] This invention relates to the field of polymer material synthesis technology, and in particular to a method and apparatus for preparing polyglycolic acid. Background Technology

[0002] Polyglycolic acid (PGA) is a synthetic polymer material with good biodegradability and biocompatibility. It has excellent processing performance, high mechanical strength and modulus, high solvent resistance and high gas barrier properties. In the medical field, it is mainly used as medical sutures and artificial bones. In the environmental materials field, it is used as a biodegradable plastic in packaging materials and degradable films.

[0003] The industrial production of polyglycolic acid typically involves multiple reactors. However, connecting multiple reactors often leads to pipeline blockages during material transport. Furthermore, the operation of multiple reactors significantly increases energy consumption and production costs. In addition, the preparation of polyglycolic acid requires mixing metal catalysts with glycolide, making it difficult to remove metals from the resulting product, which increases the difficulty of applying polyglycolic acid in the medical field.

[0004] Patent CN101374883B discloses a method for preparing aliphatic polyesters, which involves first ring-opening polymerization of cyclic esters, followed by solid-state polymerization in a twin-screw extruder, and finally melt-blending with a heat stabilizer to obtain the target product. This method lacks a polymer devolatilization device, resulting in high polymer monomer content and rapid degradation. Furthermore, solid-state polymerization easily causes pipeline blockage, hindering continuous production and impacting production efficiency.

[0005] Patent CN1111087579A discloses a method for preparing polyglycolic acid with low residual monomer content. This method involves introducing glycolide and a catalyst into a twin-screw extruder for polymerization, and a vacuum device is installed at the end of the extruder to remove monomers. However, due to the limited scalability of the screw's aspect ratio, this method cannot be scaled up for large-scale industrial production.

[0006] Therefore, an ideal medical-grade polyglycolic acid (PGA) apparatus needs to be capable of continuous production, solve the connection problem between multiple reactors, and avoid the introduction of metal catalysts. However, there are currently no reports or patents on successful synthetic apparatuses and methods for preparing PGA polymers that meet these requirements. Summary of the Invention

[0007] The technical problem solved by this invention is to provide a method for preparing polyglycolic acid. The preparation method provided by this application can realize the continuous production of polyglycolic acid and has low metal catalyst residue.

[0008] In view of this, this application provides a method for preparing polyglycolic acid, comprising the following steps:

[0009] The glycolide and initiator are melted and then fed into the prepolymerization section of the reactor for prepolymerization, followed by polymerization in the polymerization section of the reactor for polymerization, and finally devolatilization to obtain polyglycolic acid. The prepolymerization section and the polymerization section are respectively filled with a supported catalyst, the support for which is an oxide with a porous structure, and the catalyst is an octanoate.

[0010] Preferably, the support is one or more of alumina, silicon dioxide, titanium dioxide, and zirconium oxide in a cylindrical or square shape with a porous structure, and the catalyst is selected from one or more of stannous octoate, zinc octoate, antimony octoate, and lanthanum octoate.

[0011] Preferably, the preparation method of the supported catalyst is as follows:

[0012] The catalyst support is immersed in the catalyst solution, then hydrolyzed, and finally calcined to obtain the supported catalyst.

[0013] Preferably, the immersion temperature is 20–100°C and the time is 1–120 min, the hydrolysis temperature is 20–100°C and the time is 10–120 min, and the calcination temperature is 50–600°C and the time is 5–30 h.

[0014] Preferably, the initiator is selected from 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, pentaerythritol triacrylate, 3-chloro-2-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, 3-(acryloyloxy)-2-hydroxypropyl methacrylate, hydroxypropyl acrylate, 2-hydroxybutyl methacrylate, 2-methyl-2-acrylate-2-hydroxybutyl ester, 2-methyl-2-acrylate-2,3-dihydroxypropyl methacrylate, 6-hydroxyhexyl methacrylate, di(2-methyl-2-acrylate)-2-hydroxy-1,3-propanediol ester, 5-hydroxypentyl acrylate, hydroxypropyl methacrylate, 2-hydroxypropyl methacrylate, 2-buten-1-ol, 3-buten-1-ol, 4-penten- One or more of 1-ol, 5-hexen-1-ol, 6-hepten-1-ol, 7-octen-1-ol, 8-nonen-1-ol, 9-decaen-1-ol, 10-undecen-1-ol, dodecadienol, 2-methylallylol, 3-allyloxy-1,2-propanediol, ethylene glycol monoallyl ether, pentaerythritol triallyl ether, 2-methylene-1,3-propanediol, butenyl glycol, pentaerythritol allyl ether, 4-hexen-1-ol, and 3,7-dimethyloctane-2,6-dien-1-ol, wherein the molar ratio of the glycolide to the initiator is (100–10000):1, the temperature of the heat exchanger is 100–200°C, and the feed rate in the heat exchanger is 0.01–200 kg / min.

[0015] Preferably, the prepolymerization temperature is 100-200℃, the time is 10-120 min, and the pressure is 0.1-1 MPa; the polymerization temperature is 150-250℃, the time is 2-24 h, and the pressure is 0.1-1 MPa.

[0016] Preferably, the material passes through a heat exchanger before devolatilization, and the temperature of the heat exchanger is 220–300°C.

[0017] This application also provides an apparatus for preparing polyglycolic acid, comprising a reaction vessel and a devolatilization vessel connected in sequence. The reaction vessel is composed of a prepolymerization section and a polymerization section connected in series. The discharge end of the prepolymerization section is connected to the feed end of the polymerization section, and the discharge end of the polymerization section is connected to the feed section of the devolatilization vessel.

[0018] Preferably, the feed end of the preparation device is provided with a first heat exchanger and a static mixer in sequence, and a second heat exchanger is provided between the reaction vessel and the devolatilization vessel.

[0019] Preferably, the prepolymerization section is connected end to end by N1 pipes, where N1 = 1 to 10, and the polymerization section is connected end to end by N2 pipes, where N2 = 2 to 10.

[0020] This application provides a method for preparing polyglycolic acid (PGA), which involves melting glycolide and an initiator, then prepolymerizing them in the prepolymerization section of a reactor, followed by polymerization in the polymerization section, and finally devolatilization to obtain PGA. The method utilizes a supported fixed-bed catalyst, ensuring no metal catalyst residue in the PGA and solving the problem of catalyst-product separation. Furthermore, the prepolymerization and polymerization of glycolide are carried out continuously in the reactor, resolving pipeline blockage issues caused by material transport between reactors and addressing the problem of unstable material quality due to monomer burst polymerization common in conventional batch polymerization, thus achieving continuous production of PGA. Moreover, the use of unsaturated hydroxyl compounds as initiators during glycolide polymerization allows for double bond polymerization during ring-opening, increasing the polymer's molecular weight. This process can be used for the industrial production of medical-grade PGA. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the apparatus for preparing polyglycolic acid provided in an embodiment of the present invention. Detailed Implementation

[0022] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0023] In view of the problems of continuity and avoiding metal residues in polymers in existing polyglycolic acid (PGA) preparation methods, this application provides a method and apparatus for preparing PGA. The preparation method provided by this application achieves continuous production of PGA and reduces metal residues by performing prepolymerization and polymerization in a tubular reactor, with a supported catalyst fixed in the reactor to form a fixed-bed catalyst. Specifically, this invention discloses a method for preparing PGA, including the following steps:

[0024] The glycolide and initiator are melted and then fed into the prepolymerization section of the reactor for prepolymerization, followed by polymerization in the polymerization section of the reactor for polymerization, and finally devolatilization to obtain polyglycolic acid;

[0025] The prepolymerization section and the polymerization section are respectively filled with a supported catalyst, wherein the support for the supported catalyst is an oxide with a porous structure, and the catalyst is an octanoate.

[0026] In the preparation of polyglycolic acid, the supported catalyst is fixed on the polymerization plate of the reactor to form a fixed-bed catalyst. The support is specifically one or more of the following: cylindrical or square alumina, silica, titanium dioxide, and zirconium oxide, which have a porous structure. The catalyst is selected from one or more of stannous octoate, zinc octoate, antimony octoate, and lanthanum octoate. For example, the supported catalyst may specifically be selected from SnO2 / Al2O3, ZnO / Al2O3, La2O3 / Al2O3, or Sb2O3 / Al2O3.

[0027] The specific method for preparing the supported catalyst described in this application is as follows:

[0028] The catalyst support is immersed in the catalyst solution, then hydrolyzed, and finally calcined to obtain the supported catalyst.

[0029] In the preparation process of the above-mentioned supported catalyst, the catalyst support is impregnated in the catalyst solution at a temperature of 20–100°C for a time of 1–120 min, specifically at a temperature of 30–80°C for a time of 30–90 min; the hydrolysis temperature is 20–100°C for a time of 10–120 min, specifically at a temperature of 30–80°C for a time of 30–80 min; and the calcination temperature is 50–600°C for a time of 2–30 h, specifically at a temperature of 100–500°C for a time of 5–20 h.

[0030] In this application, the initiator is selected from 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, pentaerythritol triacrylate, 3-chloro-2-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, 3-(acryloyloxy)-2-hydroxypropyl methacrylate, hydroxypropyl acrylate, 2-hydroxybutyl methacrylate, 2-methyl-2-acrylate-2-hydroxybutyl ester, 2-methyl-2-acrylate-2,3-dihydroxypropyl methacrylate, 6-hydroxyhexyl methacrylate, di(2-methyl-2-acrylate)-2-hydroxy-1,3-propanediol ester, 5-hydroxypentyl acrylate, hydroxypropyl methacrylate, 2-hydroxypropyl methacrylate, 2-buten-1-ol, 3-buten-1-ol, 4-penten-1-ol, 5-hexen-1-ol, 6-hepten-1-ol, 7-octen-1-ol, etc. The initiator is selected from one or more of the following alcohols: 8-nonen-1-ol, 9-decaen-1-ol, 10-undecen-1-ol, dodecadienol, 2-methylallylol, 3-allyloxy-1,2-propanediol, ethylene glycol monoallyl ether, pentaerythritol triallyl ether, 2-methylene-1,3-propanediol, butenyldiol, pentaerythritol allyl ether, 4-hexen-1-ol, and 3,7-dimethyloctane-2,6-dien-1-ol; specifically, the initiator is selected from 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, pentaerythritol triacrylate, 3-chloro-2-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, 3-(acryloyloxy)-2-hydroxypropyl methacrylate, hydroxypropyl acrylate, 5-hexen-1-ol, 3-allyloxy-1,2-propanediol, or ethylene glycol monoallyl ether. The molar ratio of the glycolide to the initiator is (100-10000):1, specifically, the molar ratio of the glycolide to the initiator is (500-5000):1.

[0031] According to the present invention, after the glycolide and the initiator are melted in the first heat exchanger, the raw materials are fed into the prepolymerization section of the reactor via a static mixer for prepolymerization, and then into the polymerization section of the reactor for polymerization. The temperature of the first heat exchanger is 100-200°C, specifically, the temperature of the first heat exchanger is 110-160°C. The feed rate in the first heat exchanger is 0.01-200 kg / min, specifically, the feed rate is 0.02-100 kg / min. The prepolymerization temperature is 100–200℃, the time is 10–120 min, and the pressure is 0.1–1 MPa. Specifically, the prepolymerization temperature is 110–160℃, the time is 40–80 min, and the pressure is 0.2–0.8 MPa. The polymerization adopts a gradient temperature increase method, with the polymerization temperature being 150–250℃, the time being 2–24 h, and the pressure being 0.1–1 MPa. Specifically, the polymerization adopts a gradient temperature increase method, with the polymerization temperature being 170–230℃, the time being 5–16 h, and the pressure being 0.2–0.7 MPa. Both the prepolymerization section and the polymerization section of the reactor are filled with a supported catalyst. Under the action of the supported catalyst, the prepolymerization and polymerization of glycolide are promoted under the action of the initiator.

[0032] The final product obtained in this application is subjected to devolatilization to obtain polyglycolic acid; the devolatilization temperature is 150-300℃ and the pressure is 10-1000Pa, specifically, the devolatilization temperature is 180-250℃ and the pressure is 100-800Pa. After devolatilization, the product is discharged, thereby obtaining polyglycolic acid; the discharge temperature is 170-300℃ and the discharge rate is 0.01-200kg / min, specifically, the discharge temperature is 190-240℃ and the discharge rate is 0.02-50kg / min.

[0033] This application also provides an apparatus for preparing polyglycolic acid, comprising a reaction vessel and a devolatilization vessel connected in sequence. The reaction vessel consists of a prepolymerization section and a polymerization section connected in series. The discharge end of the prepolymerization section is connected to the feed end of the polymerization section, and the discharge end of the polymerization section is connected to the feed section of the devolatilization vessel.

[0034] Figure 1 This is a schematic diagram of the polyglycolic acid preparation apparatus provided by the present invention. It is a device with multiple components connected together, and the reactor is composed of pipes connected in series. In the preparation apparatus, H1 and H2 represent heat exchangers, P1, P2 and P3 represent melt pumps, M1 represents a static mixer, R1 represents a prepolymerization section, R2 represents a polymerization section, R2 section is divided into four segments: Ra, Rb, Rc and Rd, R represents a reactor, V1 represents a vacuum system, and D1 represents a devolatilization reactor.

[0035] Specifically, the preparation equipment includes a first heat exchanger, a first melt pump, a static mixer, a reaction vessel, a second melt pump, a second heat exchanger, a devolatilization vessel, and a third melt pump connected in sequence. The first heat exchanger is used for heating and melting the reactants (glycolic acid monomer and catalyst). The first melt pump is a power transmission device for glycolide and catalyst, and its inlet is connected to the outlet of the first heat exchanger, enabling the reactants passing through the first heat exchanger to be transported to the static mixer. The static mixer is a mixing device for glycolide and catalyst, and its inlet is connected to the outlet of the first melt pump, used for uniform mixing of glycolide and catalyst. The reaction vessel consists of a prepolymerization section and a polymerization section connected in series, and its inlet is connected to the outlet of the static mixer. The discharge end of the prepolymerization section and the inlet of the polymerization section are connected in series. The polymerization section employs a gradient heating method. The second melt pump is a power transmission device for transferring material from the polymerization section to the second heat exchanger. The inlet of the second melt pump is connected to the outlet of the polymerization section. The second heat exchanger is used to heat the material transferred from the second melt pump. The outlet of the second melt pump is connected to the inlet of the second heat exchanger. The devolatilization reactor is used for devolatilization and purification of the material transferred from the second heat exchanger. The outlet of the second heat exchanger is connected to the inlet of the devolatilization reactor. The polyglycolic acid production apparatus also includes a vacuum system installed in the devolatilization reactor. The inlet of the vacuum system is connected to the outlet of the devolatilization reactor, and the vacuum system can evacuate the devolatilization reactor. The outlet of the devolatilization reactor is connected to the inlet of a third melt pump, and the material is discharged through the third melt pump.

[0036] In this application, the feed end of the preparation apparatus is equipped with a first heat exchanger, the discharge end of the first heat exchanger is equipped with a first melt pump, the discharge end of the first melt pump is equipped with a static mixer, and a second heat exchanger is provided between the reaction vessel and the devolatilization vessel. The prepolymerization section is connected end-to-end by N1 pipes, where N1 = 1 to 10, and the polymerization section is connected end-to-end by N2 pipes, where N2 = 2 to 10. In a specific embodiment, the prepolymerization section is connected end-to-end by 3 pipes, and the polymerization section is divided into four segments: Ra, Rb, Rc, and Rd, which are connected end-to-end by 8 pipes. In the devolatilization vessel, the porous structure of the vessel top enables the diversion of polyglycolic acid, reducing the monomer content in the polyglycolic acid. The polyglycolic acid preparation apparatus provided in this application enables the continuous preparation of polyglycolic acid.

[0037] To further understand the present invention, the preparation method and apparatus for polyglycolic acid provided by the present invention will be described in detail below with reference to the embodiments. The scope of protection of the present invention is not limited by the following embodiments.

[0038] The detection methods in the following embodiments are as follows:

[0039] The molecular weight of the polymer was determined by gel permeation chromatography (GPC) using a Waters 410 HPLC pump. The mobile phase was a solution of hexafluoroisopropanol containing 5 mM sodium trifluoroacetate, the temperature was 35 °C, and the flow rate was 1 mL / min. Monodisperse polystyrene standards were used for universal correction.

[0040] Polyglycolic acid was tested for melt index according to GB / T 3682.2-2018. The specific process is as follows: granular polyglycolic acid was placed in a melt indexer for melt index testing at a temperature of 230℃ and a load of 2.16Kg.

[0041] The metal element content in polyglycolic acid was determined by inductively coupled plasma optical emission spectrometry (ICP-OES). The specific process is as follows: polyglycolic acid was hydrolyzed in sodium hydroxide solution to obtain an aqueous glycolic acid solution, and then the metal element content in the solution was analyzed and determined by ICP-OES.

[0042] The preparation method of the SnO2 / Al2O3 supported catalyst in the following examples is as follows:

[0043] A porous cylindrical alumina support was immersed in a 50% toluene solution of stannous octoate catalyst. After holding at 50°C for 60 min, the support was removed and transferred to water, where it was soaked at 50°C for 50 min for hydrolysis. The support was then dried with nitrogen. Finally, the catalyst was transferred to a muffle furnace and heated from 50°C to 200°C at a rate of 2°C / min, and then from 200°C to 600°C at a rate of 2°C / min. The catalyst was calcined at 600°C for 2 h. After cooling to room temperature, the supported catalyst was cleaned with deionized water to obtain the supported catalyst SnO2 / Al2O3. Other supported catalysts were prepared using the same method, except that stannous octoate could be replaced with zinc octoate, antimony octoate, or lanthanum octoate, and the support could be replaced with silicon dioxide (SiO2), titanium dioxide (TiO2), or zirconium oxide (ZrO2). These catalysts and supports can be freely combined to form supported catalysts.

[0044] A schematic diagram of the apparatus for synthesizing polyglycolic acid is shown below. Figure 1As shown, H1 is the first heat exchanger, P1 is the first melt pump, the inlet of P1 is connected to the outlet of H1, M1 is the static mixer, the inlet of M1 is connected to the outlet of melt pump P1, R is the reactor, which consists of a prepolymerization section R1 and a polymerization section R2 connected in series. The R2 section is divided into four segments: Ra, Rb, Rc, and Rd. The inlet of R is connected to the outlet of M1, and the discharge end of R1 is connected to the feed end of polymerization section R2. P2 is the second melt pump, the inlet of P2 is connected to the outlet of R2, H2 is the second heat exchanger, the discharge end of P2 is connected to the feed end of H2, D1 is the devolatilization reactor, the discharge end of H2 is connected to the feed end of D1, V1 is the vacuum system, the inlet of V1 is connected to the outlet of D1, and P3 is the third melt pump, the inlet of P3 is connected to the outlet of D1.

[0045] The process of preparing polyglycolic acid using the above-described apparatus:

[0046] The glycolide and initiator are melted in the first heat exchanger H1 and transported to the reactor R1 section with three series pipes for prepolymerization via the first melt pump P1 and static mixer M1. Then, the material is transported to the R2 section with eight series pipes for polymerization using a gradient heating method. The material is heated using the second heat exchanger and then enters the D1 section for devolatilization. Finally, the material is discharged through the third melt pump to obtain polyglycolic acid.

[0047] Comparative Example 1

[0048] Ethylene glycol and glycol are melted in a heat exchanger at a molar ratio of 1000:1. The melt is then fed into reactor R1, which has three series-connected pipes, via melt pump P1 and static mixer M1 for prepolymerization. The heat exchanger temperature is 100°C, the glycol feed rate is 0.02 kg / min, the reactor R1 temperature is 110°C, and the pressure is 0.2 MPa. The material is then transferred to R2, which has eight series-connected pipes, for gradient temperature polymerization at a pressure of 0.2 MPa. The Ra section temperature is 160°C, and the Rb section... The temperature is 190℃, the Rc section temperature is 210℃ and the Rd section temperature is 230℃. Each pipe in the R1 and R2 sections is filled with SnO2 / Al2O3 supported catalyst. The material enters the D1 section for devolatilization through melt pump P2 and heat exchanger H2. The H2 temperature is 240℃, the D1 section temperature is 250℃, and the pressure is 300Pa. Then it is discharged through melt pump P3 at a discharge temperature of 250℃, a pressure of 0.1MPa, and a discharge rate of 0.02Kg / min to obtain polyglycolic acid.

[0049] The melt index of the polyglycolic acid prepared in Comparative Example 1 of this invention was tested, and the results showed that the melt index of polyglycolic acid was 34 g / 10 min.

[0050] GPC testing was performed on the polyglycolic acid prepared in Comparative Example 1 of this invention, and the results showed that the number-average molecular weight of the polyglycolic acid was 75,000.

[0051] The polyglycolic acid prepared in Comparative Example 1 of this invention was subjected to ICP-OES analysis. The results showed that the tin content in the polyglycolic acid was 14 ppm, the aluminum content was 8.6 ppm, and no other elements were detected.

[0052] Comparative Example 2

[0053] Glycol, 2-hydroxyethyl methacrylate, and stannous octoate were added to a 10L reactor at a molar ratio of 1000:1:0.5 for prepolymerization at 110℃ and 0.2MPa for 100 minutes. Then, the temperature was raised to 200℃ for polymerization. After 10 hours, the material was heated to 250℃ for devolatilization at 300Pa to obtain polyglycolic acid.

[0054] The melt index of the polyglycolic acid prepared in Comparative Example 2 of this invention was tested, and the results showed that the melt index of polyglycolic acid was 12 g / 10 min.

[0055] The polyglycolic acid prepared in Comparative Example 2 of this invention was subjected to GPC testing, and the results showed that the number-average molecular weight of the polyglycolic acid was 102,000.

[0056] The polyglycolic acid prepared in Comparative Example 2 of this invention was subjected to ICP-OES analysis. The results showed that the tin content in the polyglycolic acid was 500 ppm, and the content of other elements was not detected.

[0057] Example 1

[0058] Ethyl glycolide and 2-hydroxyethyl methacrylate were melted in a heat exchanger at a molar ratio of 1000:1. The melt was then fed into reactor R1, which has three series-connected pipes, via melt pump P1 and static mixer M1 for prepolymerization. The heat exchanger temperature was 100°C, the glycolide feed rate was 0.02 kg / min, the reactor R1 temperature was 110°C, and the pressure was 0.2 MPa. After 100 minutes, the material was transferred to R2, which has eight series-connected pipes, for gradient temperature polymerization at a pressure of 0.2 MPa and a temperature of 16°C. At 0℃, the temperature of section Rb is 190℃, the temperature of section Rc is 210℃, and the temperature of section Rd is 230℃. Each pipe in section R1 and section R2 is filled with SnO2 / Al2O3 supported catalyst. After 10 hours, the material enters section D1 for devolatilization through melt pump P2 and heat exchanger H2. The temperature of H2 is 235℃, the temperature of section D1 is 240℃, and the pressure is 300Pa. Then, it is discharged through melt pump P3 at a discharge temperature of 250℃, a pressure of 0.1MPa, and a discharge rate of 0.02Kg / min to obtain polyglycolic acid.

[0059] The melt index of the polyglycolic acid prepared in Example 1 of the present invention was tested, and the results showed that the melt index of polyglycolic acid was 12 g / 10 min.

[0060] The polyglycolic acid prepared in Example 1 of this invention was subjected to GPC testing, and the results showed that the number-average molecular weight of the polyglycolic acid was 104,000.

[0061] The polyglycolic acid prepared in Example 1 of this invention was subjected to ICP-OES analysis. The results showed that the tin content in the polyglycolic acid was 9.6 ppm, the aluminum content was 9 ppm, and no other elements were detected.

[0062] Example 2

[0063] Ethyl glycolide and 2-hydroxyethyl acrylate were melted in a heat exchanger at a molar ratio of 800:1. The melt was then fed into reactor R1, which has three series-connected pipes, via melt pump P1 and static mixer M1 for prepolymerization. The heat exchanger temperature was 105°C, the glycolide feed rate was 0.04 kg / min, the reactor R1 temperature was 115°C, and the pressure was 0.2 MPa. After 90 minutes, the material was transferred to R2, which has eight series-connected pipes, for gradient temperature polymerization at a pressure of 0.2 MPa and a temperature of 165°C. The temperature of section Rb is 195℃, section Rc is 215℃, and section Rd is 230℃. Each pipe in sections R1 and R2 is filled with SnO2 / Al2O3 supported catalyst. After 9 hours, the material enters section D1 for devolatilization through melt pump P2 and heat exchanger H2. The temperature of H2 is 230℃, the temperature of section D1 is 240℃, and the pressure is 300Pa. Then, the material is discharged through melt pump P3 at a discharge temperature of 240℃, a pressure of 0.1MPa, and a discharge rate of 0.04Kg / min to obtain polyglycolic acid.

[0064] The melt index of the polyglycolic acid prepared in Example 2 of the present invention was tested, and the results showed that the melt index of polyglycolic acid was 20 g / 10 min.

[0065] The polyglycolic acid prepared in Example 2 of this invention was subjected to GPC testing, and the results showed that the number-average molecular weight of the polyglycolic acid was 92,000.

[0066] The polyglycolic acid prepared in Example 2 of this invention was subjected to ICP-OES analysis. The results showed that the tin content in the polyglycolic acid was 12 ppm, the aluminum content was 7.5 ppm, and no other elements were detected.

[0067] Example 3

[0068] Ethylene glycol and pentaerythritol triacrylate were melted in a heat exchanger at a molar ratio of 600:1. The melt was then fed into reactor R1, which has three series-connected pipes, via melt pump P1 and static mixer M1 for prepolymerization. The heat exchanger temperature was 110°C, the ethylene glycol feed rate was 0.06 kg / min, the reactor R1 temperature was 120°C, and the pressure was 0.2 MPa. After 80 minutes, the material was transferred to R2, which has eight series-connected pipes, for gradient temperature polymerization at a pressure of 0.2 MPa and a temperature of 170°C. The temperature of section Rb is 200℃, section Rc is 220℃, and section Rd is 225℃. Each pipe in sections R1 and R2 is filled with SnO2 / Al2O3 supported catalyst. After 8 hours, the material enters section D1 for devolatilization through melt pump P2 and heat exchanger H2. The temperature of H2 is 230℃, the temperature of section D1 is 230℃, and the pressure is 300Pa. Then, the material is discharged through melt pump P3 at a discharge temperature of 210℃, a pressure of 0.1MPa, and a discharge rate of 0.06Kg / min to obtain polyglycolic acid.

[0069] The melt index of the polyglycolic acid prepared in Example 3 of the present invention was tested, and the results showed that the melt index of polyglycolic acid was 30 g / 10 min.

[0070] The polyglycolic acid prepared in Example 3 of this invention was subjected to GPC testing, and the results showed that the number-average molecular weight of the polyglycolic acid was 77,000.

[0071] The polyglycolic acid prepared in Example 3 of this invention was subjected to ICP-OES analysis. The results showed that the tin content in the polyglycolic acid was 8.2 ppm, the aluminum content was 5.8 ppm, and no other elements were detected.

[0072] Example 4

[0073] Ethyl glycolide and 3-chloro-2-hydroxypropyl methacrylate were melted in a heat exchanger at a molar ratio of 1200:1. The melt was then fed into reactor R1, which has three series-connected pipes, via melt pump P1 and static mixer M1 for prepolymerization. The heat exchanger temperature was 115°C, the glycolide feed rate was 0.08 kg / min, the reactor R1 temperature was 125°C, and the pressure was 0.2 MPa. After 70 minutes, the material was transferred to R2, which has eight series-connected pipes, for gradient temperature polymerization at a pressure of 0.2 MPa and a temperature of [missing information - likely a temperature value]. The temperature of each section is 175℃, Rb section is 205℃, Rc section is 225℃, and Rd section is 225℃. Each pipe in R1 and R2 sections is filled with SnO2 / Al2O3 supported catalyst. After 7 hours, the material enters D1 section for devolatilization through melt pump P2 and heat exchanger H2. The temperature of H2 is 230℃, the temperature of D1 section is 235℃, and the pressure is 300Pa. Then, it is discharged through melt pump P3 at a discharge temperature of 220℃, a pressure of 0.1MPa, and a discharge rate of 0.08Kg / min to obtain polyglycolic acid.

[0074] The melt index of the polyglycolic acid prepared in Example 4 of this invention was tested, and the results showed that the melt index of polyglycolic acid was 7 g / 10 min.

[0075] The polyglycolic acid prepared in Example 4 of this invention was subjected to GPC testing, and the results showed that the number-average molecular weight of the polyglycolic acid was 125,000.

[0076] The polyglycolic acid prepared in Example 4 of this invention was subjected to ICP-OES analysis. The results showed that the tin content in the polyglycolic acid was 16 ppm, the aluminum content was 9.7 ppm, and no other elements were detected.

[0077] Example 5

[0078] Ethyl glycolide and 4-hydroxybutyl acrylate were melted in a heat exchanger at a molar ratio of 1400:1. The melt was then fed into reactor R1, which has three series-connected pipes, via melt pump P1 and static mixer M1 for prepolymerization. The heat exchanger temperature was 120°C, the glycolide feed rate was 0.1 kg / min, the reactor R1 temperature was 130°C, and the pressure was 0.2 MPa. After 60 minutes, the material was transferred to R2, which has eight series-connected pipes, for gradient temperature polymerization at a pressure of 0.2 MPa and a temperature of 180°C. The temperature of section Rb is 210℃, section Rc is 225℃, and section Rd is 230℃. Each pipe in sections R1 and R2 is filled with SnO2 / Al2O3 supported catalyst. After 6 hours, the material enters section D1 for devolatilization through melt pump P2 and heat exchanger H2. The temperature of H2 is 235℃, the temperature of section D1 is 240℃, and the pressure is 300Pa. Then, it is discharged through melt pump P3 at a discharge temperature of 220℃, a pressure of 0.1MPa, and a discharge rate of 0.1Kg / min to obtain polyglycolic acid.

[0079] The melt index of the polyglycolic acid prepared in Example 5 of the present invention was tested, and the results showed that the melt index of polyglycolic acid was 4 g / 10 min.

[0080] The polyglycolic acid prepared in Example 5 of this invention was subjected to GPC testing, and the results showed that the number-average molecular weight of the polyglycolic acid was 147,000.

[0081] The polyglycolic acid prepared in Example 5 of this invention was subjected to ICP-OES analysis. The results showed that the tin content in the polyglycolic acid was 13 ppm, the aluminum content was 6.9 ppm, and no other elements were detected.

[0082] Example 6

[0083] Ethyl glycolide and 3-(acryloyloxy)-2-hydroxypropyl methacrylate were melted in a heat exchanger at a molar ratio of 1600:1. The melt was then fed into reactor R1, which has three series-connected pipes, via melt pump P1 and static mixer M1 for prepolymerization. The heat exchanger temperature was 125°C, the glycolide feed rate was 0.12 kg / min, the reactor R1 temperature was 135°C, and the pressure was 0.2 MPa. After 50 minutes, the material was transferred to R2, which has eight series-connected pipes, for gradient temperature polymerization at a pressure of 0.2 MPa. The temperature was 185℃, the Rb section temperature was 215℃, the Rc section temperature was 225℃, and the Rd section temperature was 230℃. Each pipe in the R1 and R2 sections was filled with SnO2 / Al2O3 supported catalyst. After 5 hours, the material entered the D1 section for devolatilization through melt pump P2 and heat exchanger H2. The temperature of H2 was 245℃, the temperature of the D1 section was 245℃, and the pressure was 300Pa. Then, the material was discharged through melt pump P3 at a discharge temperature of 210℃, a pressure of 0.1MPa, and a discharge rate of 0.12Kg / min to obtain polyglycolic acid.

[0084] The melt index of the polyglycolic acid prepared in Example 6 of this invention was tested, and the results showed that the melt index of polyglycolic acid was 2 g / 10 min.

[0085] The polyglycolic acid prepared in Example 6 of this invention was subjected to GPC testing, and the results showed that the number-average molecular weight of the polyglycolic acid was 169,000.

[0086] The polyglycolic acid prepared in Example 6 of this invention was subjected to ICP-OES analysis. The results showed that the tin content in the polyglycolic acid was 15 ppm, the aluminum content was 6.5 ppm, and no other elements were detected.

[0087] Example 7

[0088] Ethyl glycol and hydroxypropyl acrylate were melted in a heat exchanger at a molar ratio of 2000:1. The melt was then fed into reactor R1, which has three series-connected pipes, via melt pump P1 and static mixer M1 for prepolymerization. The heat exchanger temperature was 130°C, the glycolide feed rate was 0.15 kg / min, the reactor R1 temperature was 140°C, and the pressure was 0.2 MPa. After 40 minutes, the material was transferred to R2, which has eight series-connected pipes, for gradient temperature polymerization at a pressure of 0.2 MPa and a temperature of 190°C. The temperature of section Rb is 220℃, section Rc is 225℃, and section Rd is 230℃. Each pipe in sections R1 and R2 is filled with SnO2 / Al2O3 supported catalyst. After 4 hours, the material enters section D1 for devolatilization through melt pump P2 and heat exchanger H2. The temperature of H2 is 240℃, the temperature of section D1 is 240℃, and the pressure is 300Pa. Then, the material is discharged through melt pump P3 at a discharge temperature of 220℃, a pressure of 0.1MPa, and a discharge rate of 0.15Kg / min to obtain polyglycolic acid.

[0089] The melt index of the polyglycolic acid prepared in Example 7 of the present invention was tested, and the results showed that the melt index of polyglycolic acid was 1 g / 10 min.

[0090] The polyglycolic acid prepared in Example 7 of this invention was subjected to GPC testing, and the results showed that the number-average molecular weight of the polyglycolic acid was 191,000.

[0091] The polyglycolic acid prepared in Example 7 of this invention was subjected to ICP-OES analysis. The results showed that the tin content in the polyglycolic acid was 11 ppm, the aluminum content was 9.3 ppm, and no other elements were detected.

[0092] Example 8

[0093] Ethyl glycol and 5-hexen-1-ol were melted in a heat exchanger at a molar ratio of 700:1. The melt was then fed into reactor R1, which has three series-connected pipes, via melt pump P1 and static mixer M1 for prepolymerization. The heat exchanger temperature was 135°C, the ethylene glycol feed rate was 0.18 kg / min, the reactor R1 temperature was 145°C, and the pressure was 0.2 MPa. After 30 minutes, the material was transferred to R2, which has eight series-connected pipes, for gradient temperature polymerization at a pressure of 0.2 MPa and a temperature of 195°C. The temperature of section Rb is 215℃, section Rc is 220℃, and section Rd is 230℃. Each pipe in sections R1 and R2 is filled with SnO2 / Al2O3 supported catalyst. After 3 hours, the material enters section D1 for devolatilization through melt pump P2 and heat exchanger H2. The temperature of H2 is 230℃, the temperature of section D1 is 235℃, and the pressure is 300Pa. Then, the material is discharged through melt pump P3 at a discharge temperature of 215℃, a pressure of 0.1MPa, and a discharge rate of 0.18Kg / min to obtain polyglycolic acid.

[0094] The melt index of the polyglycolic acid prepared in Example 8 of the present invention was tested, and the results showed that the melt index of polyglycolic acid was 23 g / 10 min.

[0095] The polyglycolic acid prepared in Example 8 of this invention was subjected to GPC testing, and the results showed that the number-average molecular weight of the polyglycolic acid was 88,000.

[0096] The polyglycolic acid prepared in Example 8 of this invention was subjected to ICP-OES analysis. The results showed that the tin content in the polyglycolic acid was 10.5 ppm, the aluminum content was 7.3 ppm, and no other elements were detected.

[0097] Example 9

[0098] Ethyl glycol and 3-allyloxy-1,2-propanediol were melted in a heat exchanger at a molar ratio of 900:1. The melt was then fed into reactor R1, which has three series-connected pipes, via melt pump P1 and static mixer M1 for prepolymerization. The heat exchanger temperature was 140°C, the ethylene glycol feed rate was 0.2 kg / min, the reactor R1 temperature was 150°C, and the pressure was 0.2 MPa. After 20 minutes, the material was transferred to R2, which has eight series-connected pipes, for gradient temperature polymerization at a pressure of 0.2 MPa and a temperature of 150°C. The temperature of the Rb section is 195℃, the Rc section temperature is 215℃, and the Rd section temperature is 225℃. Each pipe in the R1 and R2 sections is filled with SnO2 / Al2O3 supported catalyst. After 6 hours, the material enters the D1 section for devolatilization through melt pump P2 and heat exchanger H2. The temperature of H2 is 230℃, the temperature of the D1 section is 230℃, and the pressure is 300Pa. Then, it is discharged through melt pump P3 at a discharge temperature of 205℃, a pressure of 0.1MPa, and a discharge rate of 0.2Kg / min to obtain polyglycolic acid.

[0099] The melt index of the polyglycolic acid prepared in Example 9 of the present invention was tested, and the results showed that the melt index of polyglycolic acid was 15 g / 10 min.

[0100] The polyglycolic acid prepared in Example 9 of this invention was subjected to GPC testing, and the results showed that the number-average molecular weight of the polyglycolic acid was 97,000.

[0101] The polyglycolic acid prepared in Example 9 of this invention was subjected to ICP-OES analysis. The results showed that the tin content in the polyglycolic acid was 13.7 ppm, the aluminum content was 8.2 ppm, and no other elements were detected.

[0102] Example 10

[0103] Ethyl glycol and ethylene glycol monoallyl ether were melted in a heat exchanger at a molar ratio of 1100:1. The melt was then fed into reactor R1, which has three series-connected pipes, via melt pump P1 and static mixer M1 for prepolymerization. The heat exchanger temperature was 145°C, the ethylene glycol feed rate was 0.23 kg / min, the reactor R1 temperature was 155°C, and the pressure was 0.2 MPa. After 10 minutes, the material was transferred to R2, which has eight series-connected pipes, for gradient temperature polymerization at a pressure of 0.2 MPa and a temperature of 150°C. The temperature of section Rb is 190℃, section Rc is 210℃, and section Rd is 225℃. Each pipe in sections R1 and R2 is filled with SnO2 / Al2O3 supported catalyst. After 5 hours, the material enters section D1 for devolatilization through melt pump P2 and heat exchanger H2. The temperature of H2 is 235℃, the temperature of section D1 is 235℃, and the pressure is 300Pa. Then, the material is discharged through melt pump P3 at a discharge temperature of 195℃, a pressure of 0.1MPa, and a discharge rate of 0.23Kg / min to obtain polyglycolic acid.

[0104] The melt index of the polyglycolic acid prepared in Example 10 of the present invention was tested, and the results showed that the melt index of polyglycolic acid was 10 g / 10 min.

[0105] The polyglycolic acid prepared in Example 10 of this invention was subjected to GPC testing, and the results showed that the number-average molecular weight of the polyglycolic acid was 113,000.

[0106] The polyglycolic acid prepared in Example 10 of this invention was subjected to ICP-OES analysis. The results showed that the tin content in the polyglycolic acid was 12.6 ppm, the aluminum content was 7.9 ppm, and no other elements were detected.

[0107] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0108] 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 polyglycolic acid, comprising the following steps: melting glycolide and an initiator, and then pre-polymerizing in a pre-polymerization section of a reactor, and then polymerizing in a polymerization section of the reactor, and finally de-volatilizing to obtain polyglycolic acid; the pre-polymerization section and the polymerization section are respectively filled with a supported fixed-bed catalyst, the support of the supported fixed-bed catalyst is one or more of alumina, silica, titania and zirconia in a cylindrical or square shape with a porous structure, and the catalyst is tin oxide; the initiator is selected from one or more of 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, pentaerythritol triacrylate, 3-chloro-2-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, 3-(acryloyloxy)-2-hydroxypropyl methacrylate, hydroxypropyl acrylate, 5-hexene-1-ol, 3-allyloxy-1,2-propanediol and ethylene glycol monoallyl ether. The preparation method of the supported fixed-bed catalyst is specifically as follows: immersing the catalyst support into a catalyst solution, then hydrolyzing, and finally calcining to obtain the supported fixed-bed catalyst. The temperature of the immersing is 20-100℃, the time is 1-120min, the temperature of the hydrolyzing is 20-100℃, the time is 10-120min, the temperature of the calcining is 50-600℃, and the time is 5-30h.

2. The production method according to claim 1, characterized by, The molar ratio of the glycolide to the initiator is (100-10000) :

1. The temperature of the pre-polymerizing is 100-200℃, the time is 10-120min, and the pressure is 0.1-1MPa; the temperature of the polymerizing is 150-250℃, the time is 2-24h, and the pressure is 0.1-1MPa.

3. The production method according to claim 2, characterized by, The de-volatilizing is performed through a heat exchanger, and the temperature of the heat exchanger is 220-300℃.

4. The method of claim 1, wherein, 7.A device for preparing polyglycolic acid by the method according to any one of claims 1-6, comprising a reactor and a de-volatilization kettle connected in sequence, wherein the reactor is composed of a pre-polymerization section and a polymerization section connected in series; the outlet of the pre-polymerization section is connected to the inlet of the polymerization section, and the outlet of the polymerization section is connected to the inlet of the de-volatilization kettle; a first heat exchanger and a static mixer are arranged in sequence at the inlet of the device; a second heat exchanger is arranged between the reactor and the de-volatilization kettle; the pre-polymerization section is composed of N1 pipes connected end to end, and N1 = 1-10; the polymerization section is composed of N2 pipes connected end to end, and N2 = 2-10.

5. The preparation method according to claim 1, characterized in that, ​ 6. The method of claim 1, wherein, ​ ​

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