A reaction apparatus and its process

Abstract

This invention discloses a reaction apparatus and its process. The apparatus includes a shell and a pre-reaction unit, a combined chamber region, and an enhanced reaction unit arranged sequentially in the shell along the feed direction of the reactants.

Description

Technical Field

[0001] This invention relates to the chemical industry, and more particularly to a reaction apparatus and related processes for the production of glycolide. Background Technology

[0002] Glycolide is a class of cyclic ester compounds with a cyclic molecular structure formed by the elimination of two water molecules between two molecules of glycolic acid (also known as glycolic acid). In applications, glycolide can be homopolymerized to obtain high-molecular-weight polyglycolic acid (PGA) through ring-opening polymerization, or copolymerized with lactide to prepare polyglycolic acid-lactide copolymer (PGLA). This type of polymer is a burden-free biodegradable material, with final degradation products being water and carbon dioxide. It also exhibits good biocompatibility and has been widely used in high-value-added products such as absorbable surgical sutures, controlled-release drugs, human tissue-mimicking materials, biodegradable polymer scaffolds, and high-strength fibers (fishing lines), as well as multilayer bottle materials for beverage packaging, PET composite bottles for beer packaging, shrink films and containers, thermoformed teacups, composite paper and other single (multi)-layer flexible packaging materials, and agricultural biodegradable films.

[0003] Although glycolide possesses a cyclic molecular structure formed by the removal of two water molecules from glycolic acid molecules, it cannot be prepared solely through direct esterification and dehydration. Currently, there are generally two methods for preparing glycolide: the first uses chloroacetic acid as a raw material; the second uses glycolic acid (ester) (such as methyl glycolate) as a raw material. The second method has become the main process for preparing glycolide, which involves using glycolic acid (ester) as a raw material, first preparing glycolic acid oligomers through melt polycondensation, and then depolymerizing the glycolic acid oligomers into rings under high temperature and pressure to generate glycolide. Currently, such processes mostly use conventional stirred tanks as reaction vessels, requiring high temperature, high vacuum, and the presence of a large amount of high-boiling-point solvents for the reaction to proceed. However, due to the high temperature of the reactants, coking easily occurs at the bottom of the tank as the reaction progresses. Once coking occurs, it directly affects the stirring effect of the reactants, causing uneven heating within the reactants. This can easily lead to further coking in localized areas due to overheating. This not only affects the normal operation of the process, sometimes requiring production to be interrupted and the reactor to be cleaned again, but also results in significant material loss and a substantial reduction in the yield of glycolide. In addition, the use of large amounts of high-boiling-point solvents not only puts environmental pressure on industrial production but also has a significant impact on product purity.

[0004] Therefore, there is an urgent need in the field to provide a safe, environmentally friendly apparatus and method for producing glycolide that can effectively improve yield. Summary of the Invention

[0005] The present invention aims to provide apparatus and method for producing glycolide.

[0006] In a first aspect of the invention, a reaction apparatus is provided, the apparatus comprising a housing and a pre-reaction unit, a combined chamber region, and an enhanced reaction unit arranged sequentially in the housing along the feed direction of the reactants.

[0007] In another embodiment, the pre-reaction unit is a stirred reaction module or a falling film reaction module; the enhanced reaction unit is a scraped film reaction module.

[0008] In another embodiment, the stirred reaction module includes a top-open reactor, a discharge port located at the bottom of the reactor, a stirring paddle suspended in the reactor, and a heating element, wherein a gas phase annular channel is formed between the outer wall of the reactor and the shell.

[0009] In another embodiment, the heating element includes one or more of the following combinations: an electric heating mantle, a heat exchanger, and a heating coil.

[0010] In another embodiment, the falling film reaction module includes an upper partition and a lower partition arranged perpendicular to the feed direction of the reactants, a heat exchange tube arranged parallel to the feed direction of the reactants and disposed between the upper partition and the lower partition, and a film distributor disposed on the top of the upper partition.

[0011] In another embodiment, the peripheries of the upper and lower partitions are fixedly connected to the inner wall of the housing.

[0012] In another embodiment, the two ends of the heat exchange tube pass through the upper partition and the lower partition, respectively.

[0013] In another embodiment, a feed inlet is provided at the top of the housing.

[0014] In another embodiment, the scraped film reaction module includes a rotating shaft, a scraper radially connected to the rotating shaft and with its outer surface parallel to the rotating shaft, and a heating element.

[0015] In another embodiment, the distance between the outer side of the scraper and the inner wall of the housing is no more than 5 mm; preferably no more than 2 mm.

[0016] In another embodiment, a liquid guide plate and a membrane plate are sequentially arranged in the combined cavity region along the feed direction of the reactants, and an air outlet is provided on the shell corresponding to the combined cavity region.

[0017] In another embodiment, the combined cavity region is provided with a gas phase guide shroud protruding towards the inside of the housing around the air outlet on the inner wall of the housing.

[0018] In another embodiment, an airflow channel is formed between the liquid guide plate and the film plate.

[0019] In another embodiment, a liquid annular channel is provided between the bottom edge of the film plate and the inner wall of the housing corresponding to the combined cavity area.

[0020] In another embodiment, the device further includes a product collection unit.

[0021] In another embodiment, the product collection unit includes a gas-liquid separator, a condenser, and a product collection tank.

[0022] In a second aspect of the invention, a method for producing glycolide is provided, using the reaction apparatus provided by the invention as described above.

[0023] In another embodiment, the method includes the steps of:

[0024] (1) Depolymerize the molten reactants containing glycolic acid oligomers in the pre-reaction unit to generate gaseous glycolide;

[0025] (2) The gaseous glycolide generated in step (1) is collected through the outlet of the combined chamber region; and the remaining molten reactants containing glycolic acid oligomers enter the enhanced reaction unit through the combined chamber region.

[0026] (3) The remaining molten reactants containing glycolic acid oligomers are depolymerized in an enhanced reaction unit to generate gaseous glycolide; and

[0027] (4) The gaseous glycolide generated in step (3) is collected after passing through the outlet of the combined cavity region.

[0028] In another embodiment, step (2) causes the gaseous glycolide generated in step (1) to be discharged from the outlet through the gas phase guide hood of the combined cavity region and then collected. Based on the mass of glycolide collected in step (2), the conversion rate of glycolic acid oligomers in the corresponding pre-reaction unit is 20-60%.

[0029] In another embodiment, the remaining molten reactants containing glycolic acid oligomers from step (2) enter the enhanced reaction unit through the feed annular channel in the combined chamber region.

[0030] In another embodiment, step (4) causes the gaseous glycolide generated in step (3) to enter the combined cavity area through the airflow port at the top of the film plate and the airflow channel between the film plate and the liquid guide plate, and then be discharged from the outlet through the gas phase guide hood in the combined cavity area and collected.

[0031] In another embodiment, the generated gaseous glycolide passes through the outlet of the combined cavity region, then sequentially through a gas-liquid separator and a condenser before entering the product collection tank.

[0032] In another embodiment, the molten reactant containing glycolic acid oligomers contains a depolymerization catalyst, and the content of the depolymerization catalyst does not exceed 5 wt% based on the total weight of the molten reactant containing glycolic acid oligomers.

[0033] In another embodiment, the depolymerization in the pre-reaction unit or enhanced reaction unit is carried out at a pressure of ≤5 kPa; preferably, the pressure is ≤1 kPa.

[0034] In another embodiment, the depolymerization in the pre-reaction unit or the enhanced reaction unit is carried out at 220-350°C; preferably 225-300°C; more preferably 230-280°C.

[0035] Accordingly, the present invention provides a safe and environmentally friendly apparatus and method for producing glycolide that can effectively improve yield. Attached Figure Description

[0036] Figure 1 is a schematic diagram of the glycolide production apparatus provided in Embodiments 1 and 2 of the present invention; wherein

[0037] A is provided in device embodiment 1, and B is provided in device embodiment 2.

[0038] Figure 2 is a schematic diagram of the glycolide production apparatus provided in embodiments 3 and 4 of the present invention; wherein

[0039] A is provided in device embodiment 3, and B is provided in device embodiment 4.

[0040] Figure 3 is a schematic diagram of the glycolide production apparatus provided in embodiments 5 and 6 of the present invention; wherein

[0041] A is provided in device embodiment 5, and B is provided in device embodiment 6. Detailed Implementation

[0042] Through extensive and in-depth research, the inventors developed a reaction device that couples a stirred reaction module or a falling film reaction module with a scraped film reaction module via a joint chamber region. This device enables the glycolic acid oligomers used to produce glycolide to undergo a stepwise depolymerization and cyclization reaction, thereby effectively controlling the reaction process and promptly removing the generated gaseous glycolide from the reaction system to avoid material coking. Based on this, the present invention was completed.

[0043] As used in this invention, "feed direction" refers to the direction in which the reactants move forward.

[0044] As used in this invention, "couple" refers to the operative connection between two or more modules or devices, where they interact and influence each other.

[0045] As used in this invention, "film distributor" refers to a film distribution device that facilitates the uniform distribution of liquid material on the inner wall of each heating tube of a heat exchange tube (a type of heater), or on the inner wall of a reaction vessel, so that it descends in a uniform film.

[0046] glycolide production unit

[0047] The present invention provides a production apparatus for producing glycolide, comprising a shell and a pre-reaction unit, a combined chamber region and an enhanced reaction unit arranged sequentially in the shell along the feed direction of the reactants; further, the production apparatus also includes a product collection unit.

[0048] In one embodiment of the present invention, the pre-reaction unit may be a stirred reaction module or a falling film reaction module.

[0049] The stirred reaction module includes a top-open reactor, a stirring paddle inserted in the reactor, and a heating element for heating the reactor. The outer wall of the reactor does not contact the shell, and the space left can be called a gas phase annular gap channel (excluding the space between the top of the stirred reactor and the shell). This gas phase annular gap channel can connect the space between the top of the reactor and the shell with the combined cavity area.

[0050] As is commonly used, the stirring paddle inserted in the reactor can be suspended and not in contact with the inner wall and bottom of the reactor; in one embodiment of the present invention, the stirring paddle is driven by a motor to achieve the stirring function.

[0051] The heating element includes any combination of one or more of the following: an electric heating jacket arranged on the outer wall of the reactor, a heat exchanger arranged along the axial direction of the reactor on the inner wall of the reactor, or a heating coil arranged along the axial direction of the reactor in the inner cavity of the reactor.

[0052] In one embodiment of the present invention, a feed port is provided on the shell at the same height as or higher than the opening of the reactor, so as to insert a feed pipe to transport the reactant material into the reactor.

[0053] The bottom of the reactor is provided with a discharge port, and in one embodiment of the present invention, a solenoid valve is provided at the discharge port.

[0054] In one embodiment of the present invention, the bottom of the reaction vessel is arc-shaped.

[0055] The falling film reaction module may be, but is not limited to, a falling film evaporator, a falling film reactor, etc.

[0056] The falling film reaction module includes an upper partition and a lower partition arranged at intervals inside the shell along a direction perpendicular to the shell axis, a heat exchange tube arranged along the shell axis between the upper partition and the lower partition, and a film distributor disposed on the top of the upper partition.

[0057] The periphery of the upper and lower partitions is fixedly connected to the inner wall of the shell; n heat exchange tubes are provided between the upper and lower partitions, n being at least 50 for example; the upper and lower ends of the heat exchange tubes pass through the upper and lower partitions respectively, wherein the upper end of the heat exchange tube passes through the upper partition and is connected to the film distributor, and the lower end of the heat exchange tube passes through the lower partition (for example, protruding 1-10mm) and is connected to the combined cavity region.

[0058] The film spreader and the top of the housing form a sealed space, and the top of the housing is provided with a feed inlet.

[0059] In one embodiment of the present invention, the enhanced reaction unit may be a scraped film reaction module.

[0060] The scraping-film reaction module includes a rotating shaft inserted into the housing along the axial direction of the housing, multiple scrapers arranged along the axial direction of the housing and spaced apart from each other on the rotating shaft, and a heating element (e.g., but not limited to, an electric heating sleeve) sleeved on the outside of the housing. The rotating shaft is generally driven by a drive motor connected to it. An outlet is provided at the bottom of the housing.

[0061] A scraper can be arranged radially along the rotating shaft, or a scraper can be arranged at each of the two ends radially. The number of scrapers is usually determined by the space of the shell; the radial distance between the outer side of the scraper and the rotating shaft is determined by the cross-sectional size of the shell. In one embodiment of the present invention, a gap of no more than 5 mm, preferably no more than 2 mm, is left between the outer side of the scraper and the inner wall of the shell. The scraper thickness can be that used in conventional scraped film reactors.

[0062] The scraped film reaction module may be, but is not limited to, a scraped film evaporator, a scraped film reactor, etc.

[0063] The pre-reaction unit, the enhanced reaction unit, and the shell portion located between them together form a combined cavity region, and a flow guiding membrane distribution mechanism is provided in the combined cavity region.

[0064] The housing corresponding to the combined cavity area is provided with an air outlet. Preferably, the air outlet is located between the pre-reaction unit and the flow guiding membrane mechanism.

[0065] The inner wall of the housing is provided with a gas phase guide shroud protruding inward around the gas outlet; the gas phase guide shroud extends from the inner side of the housing in a funnel shape or a frustum shape to the inner wall of the housing and is fixedly connected to the inner wall of the housing. Typically, the edge of the gas phase guide shroud near the outer side of the housing needs to be connected (e.g., by welding) to the inner wall of the housing to fix the gas phase guide shroud to the inner wall of the housing.

[0066] In one embodiment of the present invention, the end of the gas phase guide hood facing the inner side of the housing is provided with an anti-liquid entrainment device (i.e., connected to the opening of the gas phase guide hood protruding from the inner wall of the housing); preferably, the anti-liquid entrainment device is a wire mesh or a swirl plate.

[0067] The flow guiding and film-forming mechanism includes a liquid guide plate and a film-forming plate arranged sequentially along the feed direction of the reactants.

[0068] In one embodiment of the present invention, the membrane plate has an inverted funnel shape or a similar inverted funnel shape, so that an airflow port is formed at the top of the membrane plate, and the liquid guide plate and the membrane plate arranged sequentially along the feed direction of the reactants form an airflow channel between the membrane plate and the liquid guide plate, and the airflow channel is connected to the airflow port at the top of the membrane plate.

[0069] In one embodiment of the present invention, the liquid guide plate has a conical or similar shape.

[0070] In one embodiment of the present invention, the feed guide plate and the film distribution plate can be fixedly connected to the housing of the reaction device corresponding to the combined cavity region through some conventional connection structures, such as, but not limited to, fixed connection through support bars or connecting rods, thereby supporting them in the combined cavity region. In one embodiment of the present invention, one end of the support bar or connecting rod is fixed to the inner wall of the housing of the reaction device corresponding to the combined cavity region by welding, and the other end is fixed to the feed guide plate or the film distribution plate by welding. In one embodiment of the present invention, the bottom diameter of the film distribution plate is larger than the bottom diameter of the feed guide plate.

[0071] In one embodiment, a liquid annular channel is provided between the bottom edge of the film plate and the inner wall of the shell.

[0072] The product collection unit generally includes a gas-liquid separator, a condenser, and a product collection tank. In one embodiment of the present invention, the gas-liquid separator adopts a side-feed method, and the gas outlet of the combined chamber area is connected to the gas-liquid separator through a pipeline. Furthermore, the upper interior of the gas-liquid separator is provided with an anti-liquid entrainment device (e.g., a wire mesh or a swirl vane).

[0073] In one embodiment of the present invention, a vacuum pump may be provided between the gas-liquid separator and the condenser to evacuate the housing and extract the gaseous glycolide generated by the reaction from the housing in a timely manner.

[0074] The exhaust port of the gas-liquid separator is connected to the material inlet of the condenser via a pipeline, and the material outlet of the condenser is connected to the product collection tank via a pipeline.

[0075] Production method of glycolide

[0076] This invention provides a method for producing glycolide, which is carried out using the above-mentioned production apparatus and includes the following steps:

[0077] The first step involves introducing molten reactants containing glycolic acid oligomers into a pre-reaction unit, where they undergo a depolymerization reaction to generate gaseous glycolide.

[0078] In the second step, the generated gaseous glycolide is collected through the outlet of the combined chamber region; while the remaining molten reactants containing glycolic acid oligomers from the pre-reaction unit enter the enhanced reaction unit through the combined chamber region.

[0079] The third step involves the molten reactants containing glycolic acid oligomers entering the enhanced reaction unit undergoing a depolymerization reaction to generate gaseous glycolide.

[0080] In the fourth step, the gaseous glycolide generated in the third step is collected after passing through the outlet of the combined cavity region.

[0081] The molecular weight (weight-average molecular weight) of the glycolic acid oligomer in the above method is preferably ≤50,000, for example, it can be selected as 2,000-50,000, 2,500-30,000, 3,000-20,000, etc.

[0082] It should be noted that the raw materials used in the above method are not limited to glycolic acid oligomers. They can also be polyglycolic acid with a molecular weight (weight average molecular weight) greater than 50,000. For example, waste polyglycolic acid materials with a weight average molecular weight of about 50,000 to 200,000 or more than 200,000 can also be used as raw materials to prepare glycolide through the above method after recycling, thereby realizing the reuse of waste polyglycolic acid materials.

[0083] The molten reaction material containing glycolic acid oligomers mentioned in the first step above contains a depolymerization catalyst, and the amount of the depolymerization catalyst added does not exceed 5 wt% of the molten glycolic acid oligomers. Further, the depolymerization catalyst can be selected from at least one of tin compounds, antimony compounds, or zinc compounds, such as, but not limited to, stannous octoate, stannous chloride, stannous lactate, antimony trioxide, diethylzinc, or zinc acetate dihydrate.

[0084] In the above method, the pressure and / or temperature in the pre-reaction unit and the enhanced reaction unit can be the same or different, preferably the same; for example, the absolute pressure is ≤5 kPa, preferably ≤1 kPa; the temperature is 220-350℃, preferably 225-300℃, more preferably 230-280℃.

[0085] In one embodiment of the present invention, the temperature of the pre-reaction unit and the enhanced reaction unit is brought to a set value, and the internal pressure of the shell is reduced to a set pressure value before proceeding to the first step of the method.

[0086] In one embodiment of the present invention, the above method, based on the total weight of the molten reactants containing glycolic acid oligomers entering the pre-reaction unit, obtains about 20-60% of the fumed glycolide (i.e., the conversion rate of glycolic acid oligomers corresponding to the obtained fumed glycolide), for example, but not limited to, about 20-40%, about 30-50%, etc.

[0087] In one embodiment of the present invention, a stirred reaction module is used as a pre-reaction unit. The temperature of the reactor and the enhanced reaction unit can be first brought to a set temperature value, and the pressure inside the shell can be reduced to a set pressure value. Then, molten reactants containing glycolic acid oligomers are introduced into the reactor through a feed pipe. The molten reactants in the reactor react under stirring, and the generated gaseous glycolide forms a vapor stream that rises and enters the combined chamber region through the gas phase annular gap channel between the reactor and the shell. An external vacuum pump creates a negative pressure in the combined chamber region and the entire reaction device, causing the gaseous glycolide generated in the stirred reaction module to flow downwards through the gas phase annular gap channel into the combined chamber region, and then exit through the gas phase guide hood from the outlet. When the reaction has progressed to a certain extent, the liquid material in the reactor (i.e., the remaining molten reactants containing glycolic acid oligomers) is discharged from the outlet at the bottom of the reactor under gravity, passing through the combined chamber region and entering the enhanced reaction unit.

[0088] In one embodiment of the present invention, the reactor is heated by turning on the heating element; the temperature of the enhanced reaction unit reaches a set temperature value by turning on the heating element (e.g., electric heating jacket) on the outside of the shell corresponding to the enhanced reaction unit.

[0089] In one embodiment of the present invention, the pressure inside the housing is reduced to a set pressure value by simultaneously turning on a vacuum pump.

[0090] In one embodiment of the present invention, molten reaction material containing glycolic acid oligomers is added through a feed pipe that passes through the upper part of the shell or simultaneously through the shell and the reactor wall.

[0091] In one embodiment of the present invention, the drive motor is turned on to drive the stirring paddle to rotate.

[0092] In one embodiment of the present invention, by opening the solenoid valve at the bottom outlet of the reactor, the liquid phase material in the reactor (i.e., the remaining molten reactant containing glycolic acid oligomers) is discharged from the outlet under gravity.

[0093] In one embodiment of the present invention, a falling film reaction module is used as a pre-reaction unit. The temperature of the heat exchange tubes in the falling film reaction module and the temperature of the enhanced reaction unit are first brought to a set value, while the pressure inside the shell is reduced to a set pressure value. Then, molten reactant containing glycolic acid oligomers enters the shell through the feed inlet at the top of the shell and is evenly distributed into each heat exchange tube by a film distributor. Under the influence of gravity, vacuum induction, and airflow, a uniform film is formed in each heat exchange tube and flows downwards. During this process, the generated gaseous glycolide enters the combined cavity region and is discharged from the outlet through the gas phase guide hood. The liquid material discharged from the heat exchange tubes continues to flow downwards through the combined cavity region into the enhanced reaction unit.

[0094] In one embodiment of the present invention, the temperature of the heat exchange tubes in the falling film reactor module is brought to a set temperature value by introducing a heat exchange medium (e.g., heat transfer oil) into the shell side of the falling film reactor module.

[0095] In one embodiment of the present invention, the temperature of the enhanced reaction unit is brought to a set temperature value by turning on the heating element (e.g., an electric heating jacket) on the outside of the housing corresponding to the enhanced reaction unit.

[0096] In one embodiment of the invention, a vacuum pump is turned on to reduce the pressure inside the housing to a set pressure value.

[0097] In one embodiment of the present invention, molten reactant containing glycolic acid oligomers is introduced into the shell through the tube side of a falling film reaction module.

[0098] In one embodiment of the present invention, under operating conditions, the average film thickness formed in each heat exchange tube of the falling film reaction module is ≤3mm, preferably ≤800μm, for example, but not limited to, 300-500μm, 400-700μm, etc.

[0099] In one embodiment of the present invention, a scraped film reaction module is used as an enhanced reaction unit. In the second step described above, the remaining molten reactants containing glycolic acid oligomers from the pre-reaction unit are uniformly guided downwards by the liquid guide plate to the film plate located below the liquid guide plate. Under the action of gravity, the liquid phase material is distributed from the bottom edge of the film plate through the liquid annular channel to the inner wall of the shell in the enhanced reaction unit. The rotating scraper driven by the drive motor continuously and uniformly scrapes the liquid phase material into a uniform liquid film on the inner wall of the shell and pushes it downwards in a spiral. During this process, the rotating scraper ensures that the continuous and uniform liquid film generates high-speed turbulence and prevents the liquid film from coking and scaling on the inner wall of the shell. The generated gaseous glycolide (i.e., the light component) forms a vapor flow and rises, entering the combined cavity area through the air outlet at the top of the film plate and the air channel between the film plate and the liquid guide plate, and then being discharged from the outlet through the gas phase guide hood. The remaining small amount of liquid phase material (i.e., the heavy component) moves downwards to the bottom of the shell under the action of gravity and is discharged.

[0100] In one embodiment of the present invention, in the working state, the average film thickness of the liquid film on the inner wall of the shell in the scraped film reaction module is ≤3mm, preferably ≤800μm, for example, but not limited to, 200-660μm, etc.

[0101] In the method provided by the present invention, the gaseous glycolide discharged from the gas outlet is introduced into a gas-liquid separator. The small amount or trace amount of liquid entrained in the gaseous glycolide is intercepted by the anti-liquid entrainer, while the gaseous glycolide discharged from the gas-liquid separator is condensed into a liquid phase by a condenser and then introduced into a product collection tank.

[0102] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0103] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0104] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are used for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0105] In this article, when the term “about” is used to modify a numerical value, it indicates an error tolerance of ±5% of that value.

[0106] The features mentioned above in this invention, or the features mentioned in the embodiments, can be combined arbitrarily. All features disclosed in this specification can be used with any compositional form, provided that the combination of these features does not contradict each other; all possible combinations should be considered within the scope of this specification. Each feature disclosed in the specification can be replaced by any alternative feature that provides the same, equivalent, or similar purpose. Therefore, unless otherwise specified, the disclosed features are merely general examples of equivalent or similar features.

[0107] The main advantages of this invention are:

[0108] 1. The glycolide production apparatus provided by this invention is not only suitable for continuous production, but also for intermittent production. It is economical and practical. When using this apparatus for industrial production, no organic solvents are required, making it safe and environmentally friendly.

[0109] 2. The pre-reaction unit and the enhanced reaction unit in the glycolide production device provided by the present invention are organically coupled into a whole through the combined cavity region and the flow guiding membrane mechanism set in the combined cavity region. The depolymerization and ring-forming reaction of the reactants can be carried out in stages in the same device. This is beneficial to properly control the degree of material conversion during the reaction process. It not only helps to discharge the generated gaseous glycolide from the reaction system in a timely manner and improve the efficiency of the depolymerization and ring-forming reaction, but also effectively avoids the occurrence of material coking.

[0110] 3. The glycolide production method provided by this invention does not require the use of organic solvents. While improving the glycolide yield, it can also effectively reduce economic costs, has low energy consumption, and can achieve green and low-carbon production.

[0111] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. Unless otherwise stated, all percentages, ratios, proportions, or parts are by weight. The units of weight-volume percentages in this invention are well known to those skilled in the art, for example, referring to the weight (grams) of solute in 100 ml of solution. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to the methods of this invention. The preferred embodiments and materials described herein are for illustrative purposes only.

[0112] Device Example 1

[0113] Provided as attachedFigure 1A The production equipment shown.

[0114] The glycolide production apparatus 1001 includes a shell 500 and a falling film reaction module 100, a combined chamber region 200 and a scraped film reaction module 300 arranged sequentially in the shell 500 along the feed direction of the reactants. The combined chamber region 200 is jointly enclosed by the falling film reaction module 100, the scraped film reaction module 300 and the portion of the shell 500 between them.

[0115] The falling film reaction module 100 includes an upper partition 101 and a lower partition 102 arranged at intervals between each other in a direction perpendicular to the axial direction of the housing 500, a plurality of heat exchange tubes 104 arranged in the axial direction of the housing 500 and between the upper partition 101 and the lower partition 102, and a film distributor 103 disposed on the top of the upper partition 101.

[0116] The upper and lower ends of the heat exchange tube 104 penetrate the upper partition 101 and the lower partition 102, respectively. The upper end of the heat exchange tube 104 passes through the upper partition 101 and is connected to the film distributor 103, while the lower end of the heat exchange tube 104 passes through the lower partition 102 and is connected to the combined cavity region 200. A feed inlet 105 is provided at the top of the shell 500.

[0117] An air outlet 201 is provided on the housing 500 corresponding to the combined cavity region 200. A gas phase guide hood 202 protruding towards the inside of the housing 500 is provided around the air outlet 201 on the inner wall of the housing 500. A liquid splash entrainer 203 is provided at the end of the gas phase guide hood 202 facing the inside of the housing 500.

[0118] The air outlet 201 is located between the falling film reaction module 100 and the liquid guide plate 204. Along the direction of material feeding, a film distribution plate 205 is also provided between the liquid guide plate 204 and the scraped film reaction module 300.

[0119] The top of the film plate 205 is provided with an air outlet 207, and an airflow channel 206 is provided between the film plate 205 and the liquid guide plate 204. A liquid annular channel 208 is provided between the bottom edge of the film plate 205 and the inner wall of the housing 500.

[0120] The scraped film reaction module 300 includes a rotating shaft 301 inserted into the housing 500 along the axial direction of the housing 500, a plurality of scrapers 302 arranged along the axial direction of the housing 500 and spaced apart from each other on the rotating shaft 301, a drive motor 304 connected to the rotating shaft 301, and a heating element 303 sleeved on the outside of the housing 500.

[0121] Device Example 2

[0122] Provided as attached Figure 1B The production equipment shown.

[0123] The glycolide production apparatus 1002 includes a shell 500, a falling film reaction module 100 arranged sequentially in the shell 500 along the feed direction of the reactants, a combined chamber region 200, a scraped film reaction module 300, and a product collection unit 400. The combined chamber region 200 is jointly enclosed by the falling film reaction module 100, the scraped film reaction module 300, and the portion of the shell 500 between them.

[0124] The falling film reaction module 100 includes an upper partition 101 and a lower partition 102 arranged at intervals between each other in a direction perpendicular to the axial direction of the housing 500, a plurality of heat exchange tubes 104 arranged in the axial direction of the housing 500 and between the upper partition 101 and the lower partition 102, and a film distributor 103 disposed on the top of the upper partition 101.

[0125] The upper and lower ends of the heat exchange tube 104 penetrate the upper partition 101 and the lower partition 102, respectively. The upper end of the heat exchange tube 104 passes through the upper partition 101 and is connected to the film distributor 103, while the lower end of the heat exchange tube 104 passes through the lower partition 102 and is connected to the combined cavity region 200. A feed inlet 105 is provided at the top of the shell 500.

[0126] An air outlet 201 is provided on the housing 500 corresponding to the combined cavity region 200. A gas phase guide hood 202 protruding towards the inside of the housing 500 is provided around the air outlet 201 on the inner wall of the housing 500. A liquid splash entrainer 203 is provided at the end of the gas phase guide hood 202 facing the inside of the housing 500.

[0127] The air outlet 201 is located between the falling film reaction module 100 and the liquid guide plate 204. Along the direction of material feeding, a film distribution plate 205 is also provided between the liquid guide plate 204 and the scraped film reaction module 300.

[0128] The top of the film plate 205 is provided with an air outlet 207, and an airflow channel 206 is provided between the film plate 205 and the liquid guide plate 204. A liquid annular channel 208 is provided between the bottom edge of the film plate 205 and the inner wall of the housing 500.

[0129] The scraped film reaction module 300 includes a rotating shaft 301 inserted into the housing 500 along the axial direction of the housing 500, a plurality of scrapers 302 arranged along the axial direction of the housing 500 and spaced apart from each other on the rotating shaft 301, a drive motor 304 connected to the rotating shaft 301, and a heating element 303 sleeved on the outside of the housing 500.

[0130] The product collection unit 400 includes a gas-liquid separator 401 connected to the gas outlet 201 of the housing 500, a vacuum pump 404 connected to the gas outlet of the gas-liquid separator 401 and the inlet of the condenser 402, and a product collection tank 403 connected to the outlet of the condenser 402.

[0131] Device Example 3

[0132] Provided as attached Figure 2A The production equipment shown.

[0133] The glycolide production apparatus 2001 includes a shell 500 and a stirred reaction module 110, a combined chamber region 200 and a scraped film reaction module 300 arranged sequentially in the shell 500 along the feed direction of the reactants. The combined chamber region 200 is jointly enclosed by the stirred reaction module 110, the scraped film reaction module 300 and the shell 500 portion between them.

[0134] The stirred reaction module 110 includes a reactor 111 with an open top, arranged axially along the shell 500, a stirring paddle 112 inserted in the reactor 111, and a heat exchanger 114 arranged axially along the inner wall of the reactor 111. A gas phase annular gap channel 113 is provided between the reactor 111 and the shell 500, which connects the top space of the reactor 111 with the combined cavity region 200. The bottom of the reactor 111 is arc-shaped and has a discharge port 115, at which a solenoid valve is installed.

[0135] An air outlet 201 is provided on the housing 500 corresponding to the combined cavity region 200. A gas phase guide hood 202 protruding towards the inside of the housing 500 is provided around the air outlet 201 on the inner wall of the housing 500. A liquid splash entrainer 203 is provided at the end of the gas phase guide hood 202 facing the inside of the housing 500.

[0136] The air outlet 201 is located between the stirred reaction module 110 and the liquid guide plate 204. Along the direction of material feeding, a film plate 205 is also provided between the liquid guide plate 204 and the scraped film reaction module 300.

[0137] The top of the film plate 205 is provided with an air outlet 207, and an airflow channel 206 is provided between the film plate 205 and the liquid guide plate 204. A liquid annular channel 208 is provided between the bottom edge of the film plate 205 and the inner wall of the housing 500.

[0138] The scraped film reaction module 300 includes a rotating shaft 301 inserted into the housing 500 along the axial direction of the housing 500, a plurality of scrapers 302 arranged along the axial direction of the housing 500 and spaced apart from each other on the rotating shaft 301, a drive motor 304 connected to the rotating shaft 301, and a heating element 303 sleeved on the outside of the housing 500.

[0139] Device Example 4

[0140] Provided as attached Figure 2B The production equipment shown.

[0141] The glycolide production apparatus 2002 includes a shell 500 and a stirred reaction module 110, a combined chamber region 200, a scraped film reaction module 300, and a product collection unit 400 arranged sequentially in the shell 500 along the feed direction of the reactants. The combined chamber region 200 is jointly enclosed by the stirred reaction module 110, the scraped film reaction module 300, and the portion of the shell 500 between them.

[0142] The stirred reaction module 110 includes a reactor 111 with an open top, arranged axially along the shell 500, a stirring paddle 112 inserted in the reactor 111, and a heat exchanger 114 arranged axially along the inner wall of the reactor 111. A gas phase annular gap channel 113 is provided between the reactor 111 and the shell 500, which connects the top space of the reactor 111 with the combined cavity region 200. The bottom of the reactor 111 is arc-shaped and has a discharge port 115, at which a solenoid valve is installed.

[0143] An air outlet 201 is provided on the housing 500 corresponding to the combined cavity region 200. A gas phase guide hood 202 protruding towards the inside of the housing 500 is provided around the air outlet 201 on the inner wall of the housing 500. A liquid splash entrainer 203 is provided at the end of the gas phase guide hood 202 facing the inside of the housing 500.

[0144] The air outlet 201 is located between the stirred reaction module 110 and the liquid guide plate 204. Along the direction of material feeding, a film plate 205 is also provided between the liquid guide plate 204 and the scraped film reaction module 300.

[0145] The top of the film plate 205 is provided with an air outlet 207, and an airflow channel 206 is provided between the film plate 205 and the liquid guide plate 204. A liquid annular channel 208 is provided between the bottom edge of the film plate 205 and the inner wall of the housing 500.

[0146] The scraped film reaction module 300 includes a rotating shaft 301 inserted into the housing 500 along the axial direction of the housing 500, a plurality of scrapers 302 arranged along the axial direction of the housing 500 and spaced apart from each other on the rotating shaft 301, a drive motor 304 connected to the rotating shaft 301, and a heating element 303 sleeved on the outside of the housing 500.

[0147] The product collection unit 400 includes a gas-liquid separator 401 connected to the gas outlet 201 of the housing 500, a vacuum pump 404 connected to the gas outlet of the gas-liquid separator 401 and the inlet of the condenser 402, and a product collection tank 403 connected to the outlet of the condenser 402.

[0148] Device Example 5

[0149] Provided as attached Figure 3A The production equipment shown.

[0150] The glycolide production apparatus 3001 includes a shell 500 and a stirred reaction module 120, a combined chamber region 200 and a scraped film reaction module 300 arranged sequentially in the shell 500 along the feed direction of the reactants. The combined chamber region 200 is jointly enclosed by the stirred reaction module 120, the scraped film reaction module 300 and the shell 500 portion between them.

[0151] The stirred reaction module 120 includes a reactor 111 with an open top, arranged axially along the shell 500; a stirring paddle 112 inserted into the reactor 111; a heating coil 124 arranged axially along the reactor 111 in the inner cavity of the reactor 111; and an electric heating jacket 125 arranged on the outer wall of the reactor 111. A gas phase annular gap channel 113 is provided between the reactor 111 and the shell 500, which connects the top space of the reactor 111 with the combined cavity region 200. The bottom of the reactor 111 is arc-shaped and has a discharge port 115, at which a solenoid valve is provided.

[0152] An air outlet 201 is provided on the housing 500 corresponding to the combined cavity region 200. A gas phase guide hood 202 protruding towards the inside of the housing 500 is provided around the air outlet 201 on the inner wall of the housing 500. A liquid splash entrainer 203 is provided at the end of the gas phase guide hood 202 facing the inside of the housing 500.

[0153] The air outlet 201 is located between the stirring reaction module 120 and the liquid guide plate 204. Along the direction of material feeding, a film plate 205 is also provided between the liquid guide plate 204 and the scraped film reaction module 300.

[0154] The top of the film plate 205 is provided with an air outlet 207, and an airflow channel 206 is provided between the film plate 205 and the liquid guide plate 204. A liquid annular channel 208 is provided between the bottom edge of the film plate 205 and the inner wall of the housing 500.

[0155] The scraped film reaction module 300 includes a rotating shaft 301 inserted into the housing 500 along the axial direction of the housing 500, a plurality of scrapers 302 arranged along the axial direction of the housing 500 and spaced apart from each other on the rotating shaft 301, a drive motor 304 connected to the rotating shaft 301, and a heating element 303 sleeved on the outside of the housing 500.

[0156] Device Example 6

[0157] Provided as attached Figure 3B The production equipment shown.

[0158] The glycolide production apparatus 3002 includes a shell 500 and a stirred reaction module 120, a combined chamber region 200, a scraped film reaction module 300, and a product collection unit 400 arranged sequentially in the shell 500 along the feed direction of the reactants. The combined chamber region 200 is jointly enclosed by the stirred reaction module 120, the scraped film reaction module 300, and the portion of the shell 500 between them.

[0159] The stirred reaction module 120 includes a reactor 111 with an open top, arranged axially along the shell 500; a stirring paddle 112 inserted into the reactor 111; a heating coil 124 arranged axially along the reactor 111 in the inner cavity of the reactor 111; and an electric heating jacket 125 arranged on the outer wall of the reactor 111. A gas phase annular gap channel 113 is provided between the reactor 111 and the shell 500, which connects the top space of the reactor 111 with the combined cavity region 200. The bottom of the reactor 111 is arc-shaped and has a discharge port 115, at which a solenoid valve is provided.

[0160] An air outlet 201 is provided on the housing 500 corresponding to the combined cavity region 200. A gas phase guide hood 202 protruding towards the inside of the housing 500 is provided around the air outlet 201 on the inner wall of the housing 500. A liquid splash entrainer 203 is provided at the end of the gas phase guide hood 202 facing the inside of the housing 500.

[0161] The air outlet 201 is located between the stirring reaction module 120 and the liquid guide plate 204. Along the direction of material feeding, a film plate 205 is also provided between the liquid guide plate 204 and the scraped film reaction module 300.

[0162] The top of the film plate 205 is provided with an air outlet 207, and an airflow channel 206 is provided between the film plate 205 and the liquid guide plate 204. A liquid annular channel 208 is provided between the bottom edge of the film plate 205 and the inner wall of the housing 500.

[0163] The scraped film reaction module 300 includes a rotating shaft 301 inserted into the housing 500 along the axial direction of the housing 500, a plurality of scrapers 302 arranged along the axial direction of the housing 500 and spaced apart from each other on the rotating shaft 301, a drive motor 304 connected to the rotating shaft 301, and a heating element 303 sleeved on the outside of the housing 500.

[0164] The product collection unit 400 includes a gas-liquid separator 401 connected to the gas outlet 201 of the housing 500, a vacuum pump 404 connected to the gas outlet of the gas-liquid separator 401 and the inlet of the condenser 402, and a product collection tank 403 connected to the outlet of the condenser 402.

[0165] Preparation Examples 1-6

[0166] Production of glycolide

[0167] In the following preparation examples 1-6, preparation examples 1-4 are based on the apparatus of the apparatus of example 2 above to prepare glycolide, preparation example 5 is based on the apparatus of the apparatus of example 4 above to prepare glycolide, and preparation example 6 is based on the apparatus of example 6 above to prepare glycolide.

[0168] Preparation Example 1:

[0169] 10 kg of glycolic acid oligomer (weight average molecular weight of approximately 10,000) was melted at approximately 230°C, and then 10 g of stannous octoate was added and stirred until homogeneous to obtain molten reactant. The molten reactant was then introduced into the shell through the feed inlet at the top of the shell at a feed rate of 10 kg / hour. The absolute pressure of the pre-reaction unit was set to approximately 0.4 kPa, and the temperature of each heat exchanger tube was set to approximately 300°C. The reactant entering the shell was evenly distributed into each heat exchanger tube via a film distributor. Under the influence of gravity, vacuum induction, and airflow, a film was formed on the heat exchange surface within each heat exchanger tube. A uniform film (average film thickness of approximately 520 μm) flows downwards. During this process, the generated gaseous glycolide enters the combined chamber region, is discharged from the outlet via a gas flow guide hood, and is collected. Once all the reactants have passed through the heat exchange tubes, approximately 3.23 kg of glycolide is collected (corresponding to a glycolic acid oligomer conversion rate of approximately 32.4%). The reactants discharged from the heat exchange tubes continue downwards into the combined chamber region and, guided by the flow-guiding film distribution mechanism, are distributed through the feed liquid annular channel to the inner wall of the shell within the enhanced reaction unit (wherein, the flow-guiding film distribution mechanism includes...). During the guiding process of the aforementioned guiding and film-distributing mechanism, the reactants are discharged from the heat exchange tubes and, under their own gravity, first fall onto the feed guide plate located in the combined cavity area, then continue to slide down along the feed guide plate, and subsequently fall onto the film-distributing plate located below the feed guide plate. Under their own gravity, the reactants then continue to slide down along the film-distributing plate to the bottom edge of the film-distributing plate, and are distributed onto the inner wall of the shell in the enhanced reaction unit through the feed annular gap channel. The absolute pressure of the enhanced reaction unit is basically the same as that of the pre-reaction unit, controlling the pressure inside the shell of the enhanced reaction unit. The wall temperature is about 300°C. The rotating scraper in the enhanced reaction unit continuously and evenly scrapes the remaining reactants into a liquid film of uniform thickness (average film thickness is about 380 μm) on the inner wall of the shell, and pushes it downward in a spiral. During this process, the liquid film formed by the remaining reactants is heated and undergoes a final depolymerization reaction. The gaseous glycolide generated by the reaction forms a vapor stream and rises. It enters the combined cavity area through the air flow port at the top of the film plate and the air flow channel between the film plate and the liquid guide plate. Then it is discharged from the gas outlet through the gas phase guide hood and collected until no more gaseous glycolide is discharged, and the reaction ends. The gaseous glycolide discharged through the outlet enters a gas-liquid separator (which has a standard anti-liquid entrainer on its upper side and an exhaust port at the top) via pipeline. In the separator, the gaseous glycolide rises through the anti-liquid entrainer, trapping any entrained residual liquid. The glycolide that passes through the anti-liquid entrainer is then discharged through the exhaust port and piped into a condenser where it is condensed into liquid. The liquid is then guided to a product collection tank. The total mass of glycolide collected is approximately 9.21 kg.Based on the mass of glycolic acid oligomers fed into the plant, the theoretical yield of glycolide is approximately 9.97 kg. Therefore, the yield of glycolide obtained in this example is approximately 92.38%.

[0170] Preparation Example 2:

[0171] 10 kg of glycolic acid oligomer (weight average molecular weight of approximately 10,000) was melted at approximately 230°C, followed by the addition of 10 g of stannous octoate and 10 g of antimony trioxide. The mixture was stirred until homogeneous, yielding molten reactants. These molten reactants were then introduced into the shell from the inlet at the top of the shell at a feed rate of 12 kg / hour. The absolute pressure of the pre-reaction unit was set to approximately 0.9 kPa, and the temperature of each heat exchanger was set to approximately 225°C. The reactants entering the shell were evenly distributed into each heat exchanger via a film distributor. Under the influence of gravity, vacuum induction, and airflow, a uniform film (average film thickness of approximately 630 μm) formed on the heat exchange surface of each heat exchanger and flowed downwards. During this process, the generated gaseous glycolide entered the combined chamber area, was discharged from the outlet via a gas flow guide hood, and was collected. After all the reactants had passed through the heat exchangers, approximately 2.76 kg of glycolide was collected (at this point, the amount of glycolide collected was approximately 2.76 kg). The polymer conversion rate is approximately 27.7%. The reactants discharged from the heat exchange tubes continue to flow downwards into the combined chamber region and are distributed onto the inner wall of the shell in the enhanced reaction unit through the feed liquid annular channel under the guidance of the flow-guiding film-forming mechanism. The absolute pressure of the enhanced reaction unit is basically the same as that of the pre-reaction unit. The temperature of the inner wall of the shell in the enhanced reaction unit is controlled at approximately 305°C. The rotating scraper in the enhanced reaction unit continuously and uniformly scrapes the remaining reactants onto the inner wall of the shell into a liquid film of uniform thickness (average film thickness is approximately 460 μm) and propels it downwards in a spiral. During this process, the liquid film formed by the remaining reactants is heated and undergoes a final depolymerization reaction. The gaseous glycolide generated by the reaction forms a vapor stream and rises. It enters the combined chamber region through the air outlet at the top of the film-forming plate and the air channel between the film-forming plate and the feed liquid guide plate. It is then discharged from the outlet through the gas phase guide hood and collected until no more gaseous glycolide is discharged, at which point the reaction ends. The gaseous glycolide discharged through the outlet enters a gas-liquid separator (which has a conventional anti-liquid entrainer on its upper side and an exhaust port at the top) via pipeline. In the separator, the gaseous glycolide rises through the anti-liquid entrainer, trapping any entrained residual liquid. The glycolide that passes through the anti-liquid entrainer is then discharged through the exhaust port and piped into a condenser where it is condensed into liquid. The liquid is then guided to a product collection tank. The total mass of glycolide collected is approximately 9.03 kg. Based on the mass of glycolic acid oligomer fed in, the theoretical glycolide yield is approximately 9.97 kg. Therefore, the glycolide yield obtained in this example is approximately 90.57%.

[0172] Preparation Example 3:

[0173] 10 kg of glycolic acid oligomer (weight-average molecular weight of approximately 10,000) was melted at approximately 230°C, and then 50 g of tin lactate was added and stirred until homogeneous to obtain molten reactant. The molten reactant was then introduced into the shell through the feed inlet at the top of the shell at a feed rate of 8 kg / hour. The absolute pressure of the pre-reaction unit was set to approximately 0.6 kPa, and the temperature of each heat exchange tube was set to approximately 250°C. The reactant entering the shell was evenly distributed into each heat exchange tube by a film distributor. Under the influence of gravity, vacuum induction, and airflow, a uniform film (average film thickness of approximately 420 μm) was formed on the heat exchange surface of each heat exchange tube and flowed from top to bottom. During this process, the generated gaseous glycolide entered the combined chamber area, was discharged from the outlet through the gas phase guide hood, and was collected. After all the reactant had passed through the heat exchange tubes, approximately 3.83 kg of glycolide was collected (corresponding to a glycolic acid oligomer conversion rate of approximately 1000%). The reactants discharged from the heat exchange tubes continue to flow downwards into the combined chamber area. Guided by the flow-guiding film distribution mechanism, they are distributed onto the inner wall of the shell in the enhanced reaction unit through the liquid annular channel. The absolute pressure of the enhanced reaction unit is basically the same as that of the pre-reaction unit. The temperature of the inner wall of the shell in the enhanced reaction unit is controlled at about 280°C. The rotating scraper in the enhanced reaction unit continuously and evenly scrapes the remaining reactants onto the inner wall of the shell into a liquid film of uniform thickness (average film thickness of about 320 μm), and pushes it downwards in a spiral. During this process, the liquid film formed by the remaining reactants is heated and undergoes a final depolymerization reaction. The gaseous glycolide generated by the reaction forms a vapor stream and rises. It enters the combined chamber area through the air outlet at the top of the film distribution plate and the air channel between the film distribution plate and the liquid guide plate. It is then discharged from the outlet through the gas phase guide hood and collected until no more gaseous glycolide is discharged, at which point the reaction ends. The gaseous glycolide discharged through the outlet enters a gas-liquid separator (which has a conventional anti-liquid entrainer on its upper side and an exhaust port at the top) via pipeline. In the separator, the gaseous glycolide rises through the anti-liquid entrainer, trapping any entrained residual liquid. The glycolide that passes through the anti-liquid entrainer is then discharged through the exhaust port and piped into a condenser where it is condensed into liquid. The liquid is then guided to a product collection tank. The total mass of glycolide collected is approximately 9.36 kg. Based on the mass of glycolic acid oligomer fed in, the theoretical glycolide yield is approximately 9.97 kg. Therefore, the glycolide yield obtained in this example is approximately 93.88%.

[0174] Preparation Example 4:

[0175] 10 kg of glycolic acid oligomer (weight average molecular weight of approximately 10,000) was melted at approximately 230°C, followed by the addition of 80 g of stannous octoate and 20 g of diethylzinc. The mixture was stirred until homogeneous, yielding molten reactants. These molten reactants were then introduced into the shell through the feed inlet at the top of the shell at a feed rate of 6 kg / hour. The absolute pressure of the pre-reaction unit was set to approximately 0.2 kPa, and the temperature of each heat exchanger was set to approximately 235°C. The reactants entering the shell were evenly distributed into each heat exchanger via a film distributor. Under the influence of gravity, vacuum induction, and airflow, a uniform film (average film thickness of approximately 310 μm) was formed on the heat exchange surface of each heat exchanger and flowed downwards. During this process, the generated gaseous glycolide entered the combined chamber area, was discharged from the outlet through the gas phase guide hood, and was collected. Once all the reactants had passed through the heat exchangers, approximately 3.52 kg of glycolide was collected (corresponding to glycolic acid oligomer). The conversion rate of the reactants is approximately 35.3%. The reactants discharged from the heat exchange tubes continue to flow downwards into the combined chamber region and are distributed onto the inner wall of the shell in the enhanced reaction unit through the liquid annular channel under the guidance of the flow-guiding film-forming mechanism. The absolute pressure of the enhanced reaction unit is basically the same as that of the pre-reaction unit. The temperature of the inner wall of the shell in the enhanced reaction unit is controlled at approximately 260°C. The rotating scraper in the enhanced reaction unit continuously and uniformly scrapes the remaining reactants onto the inner wall of the shell into a liquid film of uniform thickness (average film thickness of approximately 200 μm) and propels it downwards in a spiral. During this process, the liquid film formed by the remaining reactants undergoes a final depolymerization reaction when heated. The gaseous glycolide generated by the reaction forms a vapor stream and rises. It enters the combined chamber region through the air outlet at the top of the film-forming plate and the air channel between the film-forming plate and the liquid guide plate. It is then discharged from the outlet through the gas phase guide hood and collected until no more gaseous glycolide is discharged, at which point the reaction ends. The gaseous glycolide discharged through the outlet enters a gas-liquid separator (which has a conventional anti-foaming plate on its upper side and an exhaust port at the top) via pipeline. In the separator, the gaseous glycolide rises through the anti-foaming plate, trapping any entrained residual liquid. The glycolide that passes through the anti-foaming plate is then discharged through the exhaust port and piped into a condenser where it is condensed into liquid. The liquid is then guided to a product collection tank. The total mass of glycolide collected is approximately 8.74 kg. Based on the mass of glycolic acid oligomer fed in, the theoretical glycolide yield is approximately 9.97 kg. Therefore, the glycolide yield obtained in this example is approximately 87.66%.

[0176] Preparation Example 5:

[0177] 10 kg of glycolic acid oligomer (weight average molecular weight of approximately 10,000) was melted at approximately 225°C, and then 100 g of stannous octoate was added and stirred until homogeneous to obtain molten reactants. These molten reactants were then introduced into a stirred reactor in the pre-reaction unit and subjected to a preliminary depolymerization reaction at 5 kPa and approximately 240°C. The generated gaseous glycolide entered the combined chamber region through the gas phase annular gap channel and was then discharged from the outlet through the gas phase guide hood. When the collected glycolide mass reached approximately 2.25 kg (corresponding to a glycolic acid oligomer conversion rate of approximately 22.6%), the solenoid valve at the bottom outlet of the stirred reactor was opened, allowing the remaining reactants to enter the combined chamber region and be separated through the feed annular gap channel under the guidance of the flow-guiding membrane mechanism. The remaining reactants are spread onto the inner wall of the shell in the enhanced reaction unit. The absolute pressure of the enhanced reaction unit is basically the same as that of the pre-reaction unit. The temperature of the inner wall of the shell in the enhanced reaction unit is controlled at about 285°C. The rotating scraper in the enhanced reaction unit continuously and evenly scrapes the remaining reactants onto the inner wall of the shell to form a liquid film of uniform thickness (average film thickness of about 800 μm), and pushes it downward in a spiral. During this process, the liquid film formed by the remaining reactants is heated and undergoes a final depolymerization reaction. The gaseous glycolide generated by the reaction forms a vapor stream and rises. It enters the combined cavity area through the air outlet at the top of the film-covering plate and the airflow channel between the film-covering plate and the liquid guide plate. Then it is discharged from the outlet through the gas phase guide hood and collected until no more gaseous glycolide is discharged, and the reaction ends. The gaseous glycolide discharged through the outlet enters a gas-liquid separator (which has a conventional anti-liquid entrainer on its upper side and an exhaust port at the top) via pipeline. In the separator, the gaseous glycolide rises through the anti-liquid entrainer, trapping any entrained residual liquid. The glycolide that passes through the anti-liquid entrainer is then discharged through the exhaust port and piped into a condenser where it is condensed into liquid. The liquid is then guided to a product collection tank. The total mass of glycolide collected is approximately 8.89 kg. Based on the mass of glycolic acid oligomer fed in, the theoretical glycolide yield is approximately 9.97 kg. Therefore, the glycolide yield obtained in this example is approximately 89.17%.

[0178] Preparation Example 6:

[0179] 10 kg of glycolic acid oligomer (weight average molecular weight of approximately 10,000) was melted at approximately 225°C, and then 100 g of stannous chloride and 400 g of diethylzinc were added and stirred until homogeneous to obtain molten reactants. The molten reactants were then introduced into the stirred reactor of the pre-reaction unit and subjected to a preliminary depolymerization reaction at 2 kPa and approximately 350°C. The generated gaseous glycolide entered the combined chamber region through the gas phase annular gap channel and was then discharged from the outlet through the gas phase guide hood. When the collected glycolide mass reached approximately 3.12 kg (corresponding to a glycolic acid oligomer conversion rate of approximately 31.3%), the solenoid valve at the bottom outlet of the stirred reactor was opened, allowing the remaining reactants to enter the combined chamber region and, guided by the flow-guiding membrane mechanism, pass through the feed annular gap. The material is distributed to the inner wall of the shell in the enhanced reaction unit. The absolute pressure of the enhanced reaction unit is basically the same as that of the pre-reaction unit. The temperature of the inner wall of the shell in the enhanced reaction unit is controlled at about 350°C. The rotating scraper in the enhanced reaction unit continuously and evenly scrapes the remaining reactants into a uniform liquid film of similar thickness (average film thickness of about 660 μm) on the inner wall of the shell and pushes it downward in a spiral. During this process, the liquid film formed by the remaining reactants is heated and undergoes a final depolymerization reaction. The gaseous glycolide generated by the reaction forms a vapor stream and rises. It enters the combined cavity area through the air outlet at the top of the film plate and the air channel between the film plate and the liquid guide plate. Then it is discharged from the outlet through the gas phase guide hood and collected until no more gaseous glycolide is discharged, and the reaction ends. The gaseous glycolide discharged through the outlet enters a gas-liquid separator (which has a conventional anti-liquid entrainer on its upper side and an exhaust port at the top) via pipeline. In the separator, the gaseous glycolide rises through the anti-liquid entrainer, trapping any entrained residual liquid. The glycolide that passes through the anti-liquid entrainer is then discharged through the exhaust port and piped into a condenser where it is condensed into liquid. The liquid is then guided to a product collection tank. The total mass of glycolide collected is approximately 8.62 kg. Based on the mass of glycolic acid oligomer fed in, the theoretical glycolide yield is approximately 9.97 kg. Therefore, the glycolide yield obtained in this example is approximately 86.46%.

[0180] Comparative Example 1

[0181] 10 kg of glycolic acid oligomer (weight average molecular weight of approximately 10,000) was added to a stirred reactor and melted at approximately 230°C. Then, 10 g of stannous octoate was added and stirred until homogeneous. Subsequently, a depolymerization and cyclization reaction was carried out under conditions of approximately 0.4 kPa absolute pressure and approximately 300°C. The generated gaseous glycolide was discharged from the vent at the top of the stirred reactor and collected. The reaction ended when no more gaseous glycolide was discharged. The final collected glycolide mass was approximately 7.24 kg. Upon opening the stirred reactor, large pieces of coked material were found at the bottom, firmly adhering to the reactor wall and difficult to remove, requiring manual cleaning, which was time-consuming, labor-intensive, and resulted in significant material waste. Based on the mass of glycolic acid oligomer added, the theoretical glycolide yield was approximately 9.97 kg. The yield of glycolide obtained in this comparative example was approximately 72.62%.

[0182] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the substantive technical content of the present invention. The substantive technical content of the present invention is broadly defined within the scope of the claims. Any technical entity or method completed by others that is completely identical to or an equivalent modification of the claims is considered to be covered within the scope of the claims.

Claims

1. A reaction apparatus, characterized in that, The apparatus is used to produce glycolide, and the apparatus includes a shell and a pre-reaction unit, a combined chamber region, and an enhanced reaction unit arranged sequentially in the shell along the feed direction of the reactants. The pre-reaction unit is a stirred reaction module or a falling film reaction module; the enhanced reaction unit is a scraped film reaction module. The combined cavity region is provided with a liquid guide plate and a membrane plate in sequence along the feed direction of the reactants, and the shell corresponding to the combined cavity region is provided with an air outlet; a liquid annular gap channel is provided between the bottom edge of the membrane plate and the inner wall of the shell corresponding to the combined cavity region.

2. The reaction apparatus as described in claim 1, characterized in that, The stirred reaction module includes a top-open reactor, a discharge port located at the bottom of the reactor, a stirring paddle suspended in the reactor, and a heating element. A gas phase annular gap channel is formed between the outer wall of the reactor and the shell.

3. The reaction apparatus as described in claim 1, characterized in that, The falling film reaction module includes an upper partition and a lower partition perpendicular to the feed direction of the reactants, a heat exchange tube parallel to the feed direction of the reactants and disposed between the upper partition and the lower partition, and a film distributor disposed on the top of the upper partition.

4. The reaction apparatus as described in claim 3, characterized in that, The periphery of the upper and lower partitions is fixedly connected to the inner wall of the shell; n heat exchange tubes are provided between the upper and lower partitions, where n is at least 50; the upper and lower ends of the heat exchange tubes pass through the upper and lower partitions respectively, wherein the upper end of the heat exchange tube passes through the upper partition and is connected to the film distributor, and the lower end of the heat exchange tube passes through the lower partition and is connected to the combined cavity area.

5. The reaction apparatus as described in claim 1, characterized in that, The scraped film reaction module includes a rotating shaft, a scraper radially connected to the rotating shaft with its outer surface parallel to the rotating shaft, and a heating element.

6. The reaction apparatus as described in claim 1, characterized in that, The air outlet is located between the pre-reaction unit and the flow guiding membrane mechanism.

7. The reaction apparatus as described in claim 1, characterized in that, The inner wall of the housing is provided with a gas phase guide shroud protruding towards the inside of the housing around the air outlet; the gas phase guide shroud extends from the inside of the housing to the outside of the housing in a trumpet shape or a frustum shape to the inner wall of the housing and is fixedly connected to the inner wall of the housing.

8. The reaction apparatus as described in claim 7, characterized in that, The gas phase guide hood is equipped with a liquid splash trap at one end facing the inside of the shell.

9. The reaction apparatus as described in claim 1, characterized in that, An airflow channel is formed between the liquid guide plate and the film plate.

10. The reaction apparatus according to any one of claims 1-9, characterized in that, The device also includes a product collection unit.

11. A method for producing glycolide, characterized in that, Use the reaction apparatus as described in any one of claims 1-10.

12. The production method as described in claim 11, characterized in that, The method includes the following steps: (1) Depolymerize the molten reactants containing glycolic acid oligomers in the pre-reaction unit to generate gaseous glycolide; (2) The gaseous glycolide generated in step (1) is collected through the outlet of the combined chamber region; and the remaining molten reactants containing glycolic acid oligomers enter the enhanced reaction unit through the combined chamber region. (3) The remaining molten reactants containing glycolic acid oligomers are depolymerized in the enhanced reaction unit to generate gaseous glycolide; (4) The gaseous glycolide generated in step (3) is collected after passing through the outlet of the combined cavity region.

13. The production method as described in claim 12, characterized in that, Step (2) causes the gaseous glycolide generated in step (1) to be discharged from the outlet through the gas phase guide hood in the combined cavity area and then collected. Based on the mass of glycolide collected in step (2), the conversion rate of glycolic acid oligomer in the corresponding pre-reaction unit is 20-60%.

14. The production method as described in claim 12, characterized in that, The remaining molten reactants containing glycolic acid oligomers in step (2) enter the enhanced reaction unit through the liquid annular channel in the combined chamber region.

15. The production method as described in claim 12, characterized in that, Step (4) causes the gaseous glycolide generated in step (3) to enter the combined cavity area through the airflow port at the top of the membrane plate and the airflow channel between the membrane plate and the liquid guide plate, and then be discharged from the outlet through the gas phase guide hood in the combined cavity area and collected.

16. The production method as described in claim 12, characterized in that, In step (1), the molecular weight (weight-average molecular weight) of the glycolic acid oligomer is ≤50,000.

17. The production method as described in claim 12, characterized in that, Under operating conditions, the average film thickness formed in each heat exchange tube of the falling film reaction module is ≤3mm.

18. The production method as described in claim 12, characterized in that, In operation, the average film thickness of the liquid film on the inner wall of the shell in the scraped film reaction module is ≤3mm.

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