CN215250525U - Glycolide continuous production device - Google Patents
Glycolide continuous production device Download PDFInfo
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- CN215250525U CN215250525U CN202120899622.8U CN202120899622U CN215250525U CN 215250525 U CN215250525 U CN 215250525U CN 202120899622 U CN202120899622 U CN 202120899622U CN 215250525 U CN215250525 U CN 215250525U
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Abstract
The utility model discloses a glycolide continuous production device and application thereof. The device comprises a cracking ring-forming reactor, a spray cooler connected with an exhaust port of the cracking ring-forming reactor, a vacuum dry distiller connected with a solid discharge port of the cracking ring-forming reactor, and a crystallization unit coupled with the spray cooler.
Description
Technical Field
The utility model relates to a polymer preparation field especially relates to a glycolide continuous production device.
Background
Polyglycolic acid (abbreviated as PGA) is a biodegradable aliphatic polymer, which can be hydrolyzed under the catalysis of enzymes or acids and bases in microorganisms or organisms to finally form carbon dioxide and water, and is a degradable material with great development potential. In application, PGA can be used in the field of film products, such as agricultural mulching films, shopping bags, express bags, packaging bags, freshness protection bags, etc., and can be processed into downhole tool members (such as bridge plugs, fracturing balls, etc.) for hydrocarbon resource recovery, temporary plugging agent materials, etc., in addition to medical and medical device materials. Therefore, the PGA has considerable economic benefit and good application prospect as a novel degradable material.
Currently, the process for the preparation of polyglycolic acid comprises a route known as a two-step process, which is a process of preparing polyglycolic acid by dehydrating polycondensation of glycolic acid or glycolic acid ester-based materials (e.g., methyl glycolate) to prepare a polymer having a low molecular weight, followed by thermal cleavage of the polymer having a low molecular weight into a ring to form glycolide, and then by ring-opening polymerization of glycolide.
In the two-step process route, glycolide is an important intermediate product for synthesizing polyglycolic acid and a copolymer thereof, and the purity of glycolide can directly influence the performance of the finally generated polyglycolic acid. At present, in the process of preparing glycolide by using glycolic acid or glycolate as a raw material through polycondensation-cracking cyclization, the reaction needs to be carried out under the conditions of high temperature, high vacuum degree and high boiling point solvent, the reaction conditions are harsh, the energy consumption is high, the materials in a kettle are easy to coke, the cleaning is troublesome, the product yield is easy to reduce, and pipelines are blocked.
Currently, many attempts have been made to improve the glycolide production process. For example, US2668162 discloses a process in which glycolic acid oligomer is broken into powder and heated at 270 ℃ and 285 ℃ under ultra high vacuum (12-15 torr (1.6-2.0kPa)) and fed in small portions (about 20 g/hr) to a reaction vessel to effect depolymerization, and the resulting glycolide-containing vapor is collected. Although this method is suitable for small-scale production, it is difficult to achieve stable expanded industrial production; in addition, the oligomer is easily deteriorated by heating, and it remains in the reaction vessel in the form of a large amount of residue, resulting in a decrease in the yield of glycolide, and it takes a large amount of labor time to remove the residue; moreover, glycolide is evaporated from the reaction vessel in a gaseous state at high temperature and high vacuum, and hot liquid glycolide is directly collected and inevitably stays in a heat exchanger, a buffer tank, a pump and a conveying pipeline accompanied by heat, so that the deterioration degree of the glycolide is further increased, and furthermore, the glycolide staying in a flow dead zone (even a few millimeters) of heat tracing equipment, pipelines and valves can be silted up due to self-polymerization and even block the pipelines, so that the production is forced to be terminated, and great economic loss is caused.
Therefore, in view of the problem of solidification and/or coking at the bottom of the reaction kettle caused by the increase of the viscosity of the material system after the gas-phase glycolide generated in the ring reactor is cracked, there is an urgent need in the art to provide a method for improving the utilization rate of the glycolide contained in the discharged material.
SUMMERY OF THE UTILITY MODEL
The utility model aims at providing a glycolide continuous production device and be based on the method of device preparation glycolide.
The utility model discloses an aspect provides a glycolide continuous production device, including the schizolysis become the ring reactor, with spray cooler that the gas vent that the schizolysis becomes the ring reactor is connected, with the vacuum dry distiller that the solid bin outlet that the schizolysis becomes the ring reactor is connected and with spray cooler coupled's crystallization unit.
In another embodiment, a solid-liquid separator I and a dissolving stirrer are sequentially connected between the spray cooler and the near-end feed inlet of the crystallization unit.
In another embodiment, the device further comprises a dissolving solvent storage tank which is connected with the liquid inlet of the dissolving stirrer through a dissolving solvent supply pipeline.
In another embodiment, the outlet at the far end of the crystallization unit is connected with a solid-liquid separator II.
In another embodiment, the solid-liquid separator II connected with the outlet at the far end of the crystallization unit is connected with the dissolving solvent supply pipeline through a liquid circulation pipeline.
In another embodiment, the spray solvent reservoir is connected to the top feed inlet of the spray cooler by a spray solvent supply line.
In another embodiment, the crystallization unit is provided with at least 2 crystallization kettles in series.
In another embodiment, the side line of the far-end crystallization kettle in the series crystallization kettle is connected with the bottom discharge port of the adjacent near-end crystallization kettle.
In another embodiment, the exhaust port at the top of the vacuum retort is connected to the spray cooler through a gas circulation line.
In a second aspect of the present invention, there is provided a method for continuously producing glycolide by the apparatus as described above, the method comprising the steps of:
(1) reacting glycolic acid or its ester oligomer with a catalyst in a cracking ring reactor to obtain glycolide vapor or gas-phase glycolide and a semi-fluid material;
(2) spraying and cooling glycolide steam or gas-phase glycolide generated by cracking cyclization in a spray cooler to obtain slurry 1; and
(2') introducing the semi-fluid material cracked in the ring reactor into a vacuum dry distiller to form glycolide steam or gas-phase glycolide, and performing spray cooling in a spray cooler to obtain slurry 1;
(3) treating the slurry 1 to obtain a pretreatment solution;
(4) introducing the pretreatment solution into a crystallization unit containing more than 2 crystallization kettles connected in series one by one to obtain slurry 2; and
(5) and separating the slurry 2 to obtain refined glycolide.
In another embodiment, the glycolic acid or oligoester thereof in step (1) has a weight average molecular weight of 1 to 5 ten thousand.
In another embodiment, the catalyst in the step (1) is selected from at least one of tin-based compounds, antimony-based compounds, or zinc-based compounds.
In another embodiment, the solvent used for spray cooling in step (2) or (2') comprises at least one of esters, alcohols, ethers, and ketones.
In another embodiment, the alcohol is selected from C3-5One or more of saturated monohydric alcohol and polyhydric alcohol; the ester is butyl acetate; the ethers are selected from ethylene glycol dimethyl ether and/or n-butylAn ether; the ketones are selected from cyclohexanone and/or methyl isobutyl ketone.
In another embodiment, the rotational viscosity of the semi-fluid material introduced into the vacuum retort in step (2') is 25000 and 100000 cp.
In another embodiment, the amount of solvent used for spray cooling in step (2) or (2') is 4 to 20 times the mass of the glycolide vapor or gas-phase glycolide to be treated.
In another embodiment, the temperature of the solvent used for spray cooling in step (2) or (2') is from-20 ℃ to 60 ℃.
In another embodiment, the vacuum retort temperature in step (2') is 230 ℃ and 280 ℃ and the absolute pressure is less than or equal to 5 kPa.
In another embodiment, step (3) treats slurry 1 in a dissolution blender.
In another embodiment, the treatment in step (3) is to dissolve the solid obtained after solid-liquid separation of the slurry 1 to obtain a pretreatment solution; the solvent used for dissolving the solid is at least one of acetate, ketone or methane chloride.
In another embodiment, the glycolic acid dimer content is no more than 500ppm, based on the total weight of the pretreatment solution.
In another embodiment, the temperature of the first crystallization kettle introduced in step (4) is 5-30 ℃ lower than the dissolution temperature of step (3), and the temperature of the last crystallization kettle introduced is not higher than 0 ℃; for example, the temperature settings from the first to the last crystallization vessel decrease one by one, and the temperature difference between each crystallization vessel and the adjacent crystallization vessel in series is between 5 and 35 ℃.
In another embodiment, the pretreatment solution introduced in step (4) has a residence time in the crystallization vessel of 5 to 150 minutes.
In another embodiment, step (5) results in solid-liquid separation of the slurry 2 to yield refined glycolide and mother liquor.
In another embodiment, the mother liquor in the step (5) is returned to the dissolution solvent supply line through a liquid circulation line to perform the treatment of the step (3).
Accordingly, the present invention provides a method for improving the utilization of glycolide contained in discharged materials.
Drawings
Fig. 1 is a schematic diagram of a glycolide continuous production device provided by the utility model.
Detailed Description
The inventor finds that the material at the bottom of the reaction kettle is discharged when the cracking cyclization reaction is carried out to a certain degree, so that the coking at the bottom of the kettle can be effectively avoided; carrying out dry distillation on glycolide still contained in the discharged material, and recovering the glycolide in the glycolide; by combining the means of dry distillation, spray cooling, continuous crystallization and the like, the continuous industrial production of glycolide can be realized. On this basis, the utility model discloses has been accomplished.
Glycolide continuous production device
The utility model provides a glycolide continuous production device, including the schizolysis become the ring reactor, with spray cooler that the gas vent that the schizolysis becomes the ring reactor is connected, with the vacuum dry distiller that the solid bin outlet that the schizolysis becomes the ring reactor is connected, with the continuous cooling crystallization unit of spray cooler looks coupling.
Preferably, the vent of the cracking-to-loop reactor is arranged at the top or side upper part of the cracking-to-loop reactor.
Preferably, the solid discharge of the pyrolysis loop reactor is arranged at the bottom or in the lower lateral part of the pyrolysis loop reactor.
Preferably, the side lower part of the spray cooler is provided with an air inlet which is connected with an exhaust port of the cracking loop reactor, the top of the spray cooler is provided with a spray solvent inlet which is connected with a spray solvent storage tank through a spray solvent supply pipeline, the spray solvent supply pipeline is provided with a cooler, and further, the spray cooler can be provided with a liquid delivery pump.
In one embodiment of the present invention, the spray cooler is evacuated and depressurized using a vacuum pump so that the pressure inside the spray cooler is reduced to be the same or substantially the same as the pressure in the cracking ring reactor.
As an implementation scheme, a solid-liquid separator I and a dissolving stirrer are arranged between the spray cooler and the continuous cooling crystallization unit, a dissolving solvent liquid inlet is arranged at the top of the dissolving stirrer, and the dissolving solvent liquid inlet is connected with a dissolving solvent liquid storage tank through a dissolving solvent supply pipeline; preferably, a liquid delivery pump is arranged on the dissolving solvent supply pipeline; under the working state, slurry formed by spraying and cooling glycolide steam or gas-phase glycolide in the spray cooler is discharged from a discharge port at the bottom of the spray cooler and enters a solid-liquid separator I for solid-liquid separation, the solid material obtained by separation is transferred to a dissolving stirrer, the solid material is stirred and dissolved by a dissolving solvent to obtain a pretreatment solution, and then the pretreatment solution is introduced into a continuous cooling and cooling crystallization unit for continuous cooling and cooling crystallization. In order to dissolve the solid materials quickly and sufficiently, the dissolving stirrer can be heated by adopting a conventional heat tracing mode. In one embodiment, a liquid delivery pump is arranged on a pipeline for introducing the pretreatment solution into the continuous cooling and crystallizing unit.
As an embodiment, the continuous cooling and crystallizing unit comprises at least 2 crystallization kettles which are connected in series and are arranged in a stepped descending manner.
Preferably, the crystallization kettle is provided with 2-5 crystallization kettles in total. Such as a first crystallization kettle, a second crystallization kettle, a third crystallization kettle, a fourth crystallization kettle, a fifth crystallization kettle, etc.
In one embodiment, each of the serially connected crystallization kettles in the continuous temperature-reducing cooling crystallization unit is fed by a side line (for example, the side line is fed from the upper position of the crystallization kettle), and the side line of the next crystallization kettle is connected with the bottom discharge port of the previous crystallization kettle.
Preferably, the side line of the first crystallization kettle in the continuous cooling and crystallizing unit is connected with a liquid outlet at the bottom of the dissolving stirrer.
As an embodiment, the device also comprises a solid-liquid separator II connected with the bottom discharge hole of the last crystallization kettle in the continuous cooling crystallization unit.
Preferably, the solid-liquid separator II is provided with a liquid outlet and a solid outlet, the liquid outlet is connected with the dissolving solvent supply pipeline through a liquid circulation pipeline, in an operating state, after the slurry entering the solid-liquid separator II is subjected to solid-liquid separation, most of the obtained mother liquor is returned to the dissolving stirrer through the liquid circulation pipeline and the dissolving solvent supply pipeline through the liquid outlet for recycling, and the obtained solid is transferred to the product collection tank after being subjected to vacuum drying. In one embodiment, a liquid transfer pump is provided on the liquid circulation line.
As an embodiment, the vacuum retort is a vacuum spiral-ribbon retort and comprises a retort body, a spiral-ribbon rotating shaft arranged inside the retort body along the axial direction of the retort body and a driving motor in transmission connection with the spiral-ribbon rotating shaft.
Preferably, the dry distiller body is of a cylindrical structure, a heating sleeve is arranged on the outer side of the dry distiller body, a feed inlet is formed in the feed end of the dry distiller body, a slag discharge buffering mechanism is arranged at the discharge end of the dry distiller body, the feed inlet is connected with a solid discharge port of the cracking ring-forming reactor, at least 1 exhaust port is formed in the top of the dry distiller body, and the exhaust port is connected with an air inlet in the lateral lower part of the spray cooler through a gas circulation pipeline.
Preferably, the plurality of the exhaust ports are arranged at the top of the retort body at regular intervals along the axial direction of the retort body.
Furthermore, the slag discharge buffer mechanism comprises a material collecting bin arranged at the discharge end of the retort body and a lock hopper connected with the material collecting bin, and a slag conveying belt is arranged below the lock hopper.
Preferably, the spiral ribbon rotating shaft includes a central shaft, and an outer spiral ribbon and an inner spiral ribbon spirally wound and arranged on the central shaft along an axial direction of the central shaft, a bending direction of the outer spiral ribbon is consistent with a bending direction of the inner spiral ribbon, and the outer spiral ribbon and the inner spiral ribbon are integrally formed.
Continuous production method of glycolide
The utility model provides a continuous production method of glycolide, the steps of the method include:
in the first step, molten polyglycolic acid or its ester (or glycolic acid or its ester oligomer) is cracked into ring to generate glycolide steam or gas-phase glycolide;
secondly, spraying glycolide steam or gas-phase glycolide by using a solvent to form slurry 1;
thirdly, performing solid-liquid separation on the slurry 1 to obtain a solid material;
fourthly, mixing the solid material with an organic solvent to fully dissolve the solid material to obtain a pretreatment solution;
step five, sequentially introducing the pretreatment solution into at least 2 serially-connected crystallization kettles with the temperature descending in a stepped manner for cooling and crystallization, and obtaining slurry 2 from the last crystallization kettle;
and sixthly, performing solid-liquid separation on the slurry 2 to obtain the refined glycolide.
The weight average molecular weight of the polyglycolic acid or ester thereof melted in the above first step is 1 to 5 ten thousand, for example, but not limited to, 2 to 3 ten thousand, 1.2 to 4.5 ten thousand, and the like.
The cleavage cyclization reaction in the first step is carried out in the presence of a catalyst, which may be selected from at least one of tin-based compounds, antimony-based compounds, or zinc-based compounds, such as, but not limited to, stannous octoate, stannous chloride, tin lactate, antimony trioxide, diethyl zinc, or zinc acetate dihydrate, and the like.
As an embodiment, the catalyst is used in an amount of 0.1 to 1% by weight, preferably 0.2 to 0.8% by weight, based on the mass of polyglycolic acid or ester thereof.
The cracking and cyclization reaction in the first step is carried out at the temperature of 230-280 ℃ and the absolute pressure of 100-1800 Pa.
In addition to the generation of glycolide vapor or gas-phase glycolide in the first step, a viscous semi-fluid material is generated, and in one embodiment of the present invention, when the viscosity of the semi-fluid material is between 25000-100000cp, the material is subjected to dry distillation treatment, and the formed glycolide vapor or gas-phase glycolide is also subjected to the second step. The inventor finds that when the viscosity of the semi-fluid material is low, on one hand, the cracking ring forming reaction is not thorough, on the other hand, the semi-fluid material cannot enter the dry distillation equipment to be effectively conveyed by a screw belt, if the semi-fluid material is discharged under the condition of high viscosity, the bottom of the kettle is likely to be solidified and/or coked, and even more, the viscosity of the semi-fluid material is suddenly increased to the extent that the semi-fluid material cannot be discharged out of the reaction kettle, so that the semi-fluid material cannot be dry distilled at all.
As the utility model discloses used, "viscosity" of above-mentioned semifluid material means "rotational viscosity", belongs to the relative viscosity among the dynamic viscosity, and the testing instrument who adopts is the boehler flight RVDV-2T viscometer, rotational speed: 0.1-200rpm, test temperature: 230 ℃ to 230 ℃.
The solvent used in the second step may include at least one of esters, alcohols, ethers and ketones. The esters may be selected from butyl acetate; the alcohols may be selected from C3-C5The saturated monohydric alcohol or polyhydric alcohol of (2) may be, for example, one or more selected from n-propanol, isopropanol, n-butanol, isobutanol, t-butanol, 1-pentanol, 2-pentanol, 3-pentanol, ethylene glycol, diethylene glycol, propylene glycol, and glycerin; the ethers can be one or two of ethylene glycol dimethyl ether or n-butyl ether; the ketone can be selected from one or two of cyclohexanone or methyl isobutyl ketone.
The inventor finds that the second step is carried out spraying under high vacuum, if the boiling point of the spraying solvent is too low, the spraying solvent is gasified under the corresponding conditions of high vacuum and temperature, and the gas-phase glycolide cannot be effectively sprayed and cooled, but if the boiling point of the spraying solvent is too high, the subsequent removal is not facilitated, more solvent is remained in the liquid-phase glycolide, and the quality of the liquid-phase glycolide is influenced.
In one embodiment, the amount of spray solvent is 4 to 20 times the mass of glycolide vapor or gas phase glycolide entering the spray cooler.
As an embodiment, the spraying temperature of the spraying solvent is set to-20 ℃ to 60 ℃.
As an embodiment, the absolute pressure in the spray cooler is not lower than the saturated vapor pressure of the solvent having the highest saturated vapor pressure in the spray solvent, for example, the absolute pressure in the spray cooler is 100-1800 Pa.
As an embodiment, the temperature of the slurry 1 formed by cooling in the spray cooler is not more than 80 ℃, preferably not more than 60 ℃.
The solid-liquid separation method in the third step includes, but is not limited to, suction filtration, centrifugation, and the like.
In one embodiment of the present invention, the glycolic acid dimer content is not more than 0.25 wt.%, preferably not more than 0.23 wt.%, based on the total weight of the solid material obtained in the third step.
The organic solvent used in the fourth step may include at least one of acetates, ketones or methane chlorides. The acetate can be at least one of ethyl acetate or methyl acetate; the ketone can be selected from at least one of acetone, butanone, methyl ethyl ketone or methyl isobutyl ketone; the methane chloride can be selected from at least one of dichloromethane, trichloromethane or carbon tetrachloride.
Further, the organic solvent used may further include alcohols, such as one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, or tert-butanol.
Most preferably, the organic solvent used in the above fourth step is ethyl acetate.
As an embodiment, the amount of the organic solvent used in the fourth step is 4 to 6 times the mass of the solid material.
In one embodiment, the glycolic acid dimer content does not exceed 500ppm based on the total weight of the pretreatment solution obtained in the fourth step above.
In an embodiment of the present invention, the fourth step is to add the solid material into the container containing the organic solvent, and heat up the solid material while stirring the solid material, so that the solid material is sufficiently dissolved.
The dissolution temperature in the fourth step is determined depending on the organic solvent used, as long as the solid material can be completely dissolved, but should be lower than the boiling point of the organic solvent so as not to unnecessarily lose the solvent.
In one embodiment of the present invention, the fourth step is to filter the solid material after the solid material is sufficiently dissolved to remove insoluble substances (such as glycolic acid polymers) in the crude glycolide product, thereby obtaining the pretreatment solution.
The pretreatment solution in the fifth step is sequentially introduced into more than 2 crystallization kettles connected in series, the temperature of the crystallization kettles is gradually reduced, the temperature difference between two adjacent crystallization kettles connected in series is favorable for recrystallization, namely, the temperature reduction degree is favorable for reducing the solubility of glycolide in the pretreatment solution, and the glycolide is precipitated after the solution is saturated. The inventor finds that the temperature difference between two adjacent crystallization kettles is too large, so that the material quenching speed is too high or the quenching process is too strong, a large amount of glycolide is rapidly separated out in the process and is rapidly accumulated, so that the glycolide separated out earlier is easily adhered to and stays on the inner wall of the crystallization kettle due to the compression of a large amount of glycolide separated out after relative lag, and the material in the next batch is difficult to carry out the material staying in the previous batch when flowing through the crystallization kettle, thereby causing the waste of the material and greatly reducing the yield of the final glycolide.
And a plurality of crystallization kettles are adopted, before the material reaches the last crystallization kettle, the quenching speed or the quenching degree of the material is properly reduced by utilizing the proper temperature difference between the two adjacent crystallization kettles, so that the glycolide in the material can be separated out mildly, retention of the separated glycolide in the crystallization kettles is favorably reduced or eliminated to the maximum extent, and the retained glycolide is easily carried out by the material of the next batch even if a small amount of retention occurs.
The term "crystallization vessel" is used in the art to mean a vessel capable of controlling the temperature within a certain range.
In one embodiment of the present invention, the temperature difference between each crystallization kettle and the adjacent crystallization kettle connected in series is between 5 and 35 ℃.
The temperature of the first crystallization vessel into which the pretreatment solution is introduced in the fifth step is 5 to 30 ℃ lower than the dissolution temperature in the fourth step, and the temperature of the last crystallization vessel into which the pretreatment solution is introduced is generally not more than 0 ℃.
In one embodiment, the temperature of the at least 2 crystallization kettles connected in series is set to be in a step-type descending manner, and the temperature of the first crystallization kettle is lower than that of the pretreatment solution.
In an embodiment of the present invention, in the above fifth step, the crystallization kettles are 5 series crystallization kettles with a temperature falling in a stepwise manner, wherein the temperature of the first crystallization kettle is set to 42 ℃, the temperature of the second crystallization kettle is set to 30 ℃, the temperature of the third crystallization kettle is set to 18 ℃, the temperature of the fourth crystallization kettle is set to 10 ℃, and the temperature of the fifth crystallization kettle is set to-5 ℃.
In an embodiment of the present invention, in the above fifth step, the crystallization kettles are 4 series crystallization kettles with a temperature falling in a stepwise manner, wherein the temperature of the first crystallization kettle is set to 35 ℃, the temperature of the second crystallization kettle is set to 18 ℃, the temperature of the third crystallization kettle is set to 5 ℃, and the temperature of the fourth crystallization kettle is set to-5 ℃.
In an embodiment of the present invention, in the above fifth step, the crystallization kettles are 3 series crystallization kettles with a temperature falling in a stepwise manner, wherein the temperature of the first crystallization kettle is set to 40 ℃, the temperature of the second crystallization kettle is set to 12 ℃, and the temperature of the third crystallization kettle is set to-5 ℃.
In an embodiment of the present invention, in the above fifth step, the crystallization kettles are 2 series crystallization kettles with a temperature set in a stepwise descending manner, wherein the temperature of the first crystallization kettle is set to 32 ℃, and the temperature of the second crystallization kettle is set to-2 ℃.
The pretreatment solution introduced into the crystallization kettle in the fifth step needs to stay in the crystallization kettle for a period of time, such as 5-150 minutes; in one embodiment of the present invention, the higher the temperature, the longer the residence time in the crystallization vessel is generally.
The solid-liquid separation in the sixth step may be a means commonly used in the art, such as, but not limited to, centrifugation and the like.
In an embodiment of the present invention, the solid material obtained by centrifuging the slurry 2 in the sixth step may be dried to obtain the refined glycolide. Drying may be carried out by methods conventional in the art, such as, but not limited to, vacuum drying, e.g., 40-60 ℃ at an absolute pressure of 500Pa or less, for 1-2 hours.
The utility model discloses glycolide purity can reach more than 99.5% in the fine glycolide or fine glycolide product that obtain, and solvent residual rate is less than or equal to 0.3%, and glycolic acid content < 0.03 wt%, glycolic acid dimer content < 0.03 wt%, water content < 0.03 wt%. The content of glycolide, residual solvent and glycolic acid dimer in the present invention is obtained by gas chromatography known in the art, the content of water is obtained by Karl Fischer moisture meter, and the content of glycolic acid is obtained by potentiometric titration known in the art (for example, automatic potentiometric titrator).
In an embodiment of the present invention, the sixth step is to perform solid-liquid separation on the slurry 2 to obtain refined glycolide and a mother liquor; then the mother liquor is returned to the fourth step to be mixed with the solid material newly obtained from the third step, and the fourth step to the sixth step are carried out for continuous circulation, thereby continuously obtaining the refined glycolide.
In an embodiment of the present invention, the solvent lost in the sixth step after drying is collected (for example, but not limited to, collected by a heat exchanger) and mixed with the mother liquor, and there is a very small amount of solvent in the dried refined glycolide, which is negligible when measured in kg.
In the sixth step, the mother liquor is returned to the fourth mixing step in which the second batch of the solid material from the third step, the mother liquor returned from the sixth step and the additional organic solvent are contained, and then the pretreated solution obtained by sufficient dissolution is subjected to the following steps such as the fifth step of the second batch, thereby carrying out the second-batch production of purified glycolide, and so on, and the processes of the third batch, the fourth batch and so on are carried out, thereby realizing continuous circulation/production. Based on the material balance in the industrial production, the next batch circulation brings out the material remained or accumulated in the previous batch circulation, and the quantity of the refined glycolide obtained in the next batch and the previous batch is basically the same from the appearance.
The determination of how many batches of such recycle/production need to be carried out is generally based on the cumulative glycolic acid dimer content in the mother liquor to be returned to the fourth step in the sixth step described above or the glycolic acid and/or glycolic acid dimer content of the resulting refined glycolide product.
In one embodiment of the present invention, the make-up organic solvent is about 5-50 w/w% of the returned mother liquor, such as, but not limited to, about 5-15 w/w%, about 8-12 w/w%, about 9-11 w/w%, and the like.
In one embodiment of the present invention, the content of glycolic acid dimer accumulated in the mother liquor to be returned to the fourth step exceeds 1000ppm or the content of glycolic acid and/or glycolic acid dimer in the resulting refined glycolide product exceeds 0.03 wt%, and the sixth step is stopped.
Once a run of multiple batches of the continuous process for purifying glycolide according to the present invention has been completed, a new run of such continuous process can be started, wherein all of the newly added organic solvent is used in the fourth step (instead of the mother liquor and make-up organic solvent returned in the sixth step).
The various solvents used in the utility model are reagent grade, and do not need further treatment.
In an embodiment of the present invention, the glycolide continuous production apparatus provided by the present invention is used for continuous production of glycolide, comprising the following steps:
step S1: introducing molten polyglycolic acid or ester thereof with certain molecular weight into a cracking ring-forming reactor, adding a catalyst, carrying out cracking ring-forming reaction at the temperature of 230-plus-280 ℃ and the absolute pressure of 100-plus-1800 Pa, directly introducing generated glycolide steam or gas-phase glycolide into a spray cooler for spray cooling, directly introducing the material which is in a viscous semi-fluid state in the cracking ring-forming reactor into a vacuum dry distiller for dry distillation treatment when the viscosity of the material in the cracking ring-forming reactor reaches 25000-plus-100000 cp, and returning the formed glycolide steam or gas-phase glycolide to the spray cooler for spray cooling through a gas circulation pipeline;
step S2: and (2) carrying out solid-liquid separation on slurry 1 formed by carrying out spray cooling on glycolide steam or gas-phase glycolide in a spray cooler, retaining solid materials, transferring the solid materials into a dissolving stirrer, dissolving to obtain a pretreatment solution, then introducing the pretreatment solution into a continuous cooling and cooling crystallization unit for continuous cooling and cooling crystallization, carrying out solid-liquid separation on the obtained slurry 2, returning most of the obtained mother liquor to the dissolving stirrer for recycling, and transferring the obtained solid into a product collection tank after vacuum drying.
In one embodiment of the present invention, the temperature in the vacuum retort is 230-280 ℃, and the absolute pressure is less than or equal to 5 Kpa.
In one embodiment of the present invention, the glycolide vapor or gas-phase glycolide is discharged from the side or top of the ring reactor by cracking, and is directly introduced into the spray cooler from the lower side of the spray cooler.
Preferably, in the operating state, the pressure in the cracking-to-loop reactor is the same or approximately the same as the pressure in the spray cooler.
As an embodiment, the solid materials in the dissolution stirrer are stirred and dissolved under normal pressure, and the dissolution stirrer can be heated by adopting a conventional heat tracing mode, and the temperature of the pretreatment solution obtained by dissolution is 50-60 ℃, and preferably 60 ℃.
In an embodiment of the present invention, there are at least 2 crystallization kettles connected in series in the cooling crystallization unit, wherein the lateral line of the first crystallization kettle at the near end is connected to the bottom liquid outlet of the dissolution agitator.
In one embodiment, the at least 2 crystallization kettles connected in series are all fed by a side line, and the side line of the next crystallization kettle is connected with the bottom discharge port of the previous crystallization kettle.
To make the features and effects of the present invention comprehensible to those skilled in the art, the general description and definitions are made with the terms and expressions mentioned in the specification and claims. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
The theory or mechanism described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, i.e., the present invention may be practiced without limitation to any particular theory or mechanism.
All features defined herein as numerical ranges or percentage ranges, such as values, amounts, levels and concentrations, are for brevity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to cover and specifically disclose all possible subranges and individual numerical values (including integers and fractions) within the range.
The above-mentioned features of the present invention, or those mentioned in the embodiments, can be combined arbitrarily. All features disclosed in this specification may be combined in any combination, provided that there is no conflict between such features and the combination, and all possible combinations are to be considered within the scope of the present specification. Each feature disclosed in this specification may be replaced by an alternative feature serving the same, equivalent, or similar purpose. Thus, unless expressly stated otherwise, the features disclosed are merely generic examples of equivalent or similar features.
The utility model has the main advantages that:
1. the spray cooling is coupled with the continuous crystalline phase, so that the retention of hot liquid glycolide which is directly collected conventionally in a high-temperature state can be completely avoided, the self-polymerization degree of the glycolide can be effectively inhibited or reduced, and the phenomenon that the pipeline is blocked due to metamorphism and solidification in the pipeline conveying process of the hot liquid glycolide is avoided.
2. Compared with the conventional recrystallization method, the method has the advantages that the use amount of the solvent can be obviously saved, the residual solvent removal process is not needed, the waste liquid treatment problem is avoided, and the environment is not polluted.
3. When the viscosity of the material in the cracking ring reactor reaches 25000-100000cp, the viscous semi-fluid material in the reactor is transferred to a vacuum dry distiller in time, so that the solidification and/or coking phenomenon of the material due to further aggravation of the reaction degree can be effectively avoided, the viscous semi-fluid material entering the vacuum dry distiller can be discharged in a gas phase under the condition of high temperature and high vacuum degree, the carried or contained glycolide can be returned to a spray cooler through a gas circulation pipeline for spray cooling, meanwhile, the viscous semi-fluid material can move forward under the driving of a spiral belt and can be gradually changed into a solid material in the moving process, the solid material can be crushed under the disturbance of the spiral belt, the heating area is increased, the residual glycolide in the viscous semi-fluid material can be further released, and the crushed solid material can pass through a collecting bin, The lock hopper is discharged out of the vacuum dry distiller, namely the coupling of the vacuum dry distiller and the cracking ring-forming reactor, so that the loss of glycolide can be effectively reduced while the technical problems that materials are easy to solidify and/or coke in the reactor and the like in the prior art are overcome, and the final yield of glycolide can be improved.
4. The device and the process flow thereof provided by the utility model have good continuous stability, can effectively avoid unnecessary material loss, reduce the process cost, have low energy consumption, can realize the low carbonization production, are convenient for the industrialization and enlarge the production, can be applied to the production preparation of ten thousand tons of grades of polyglycolic acid.
The present invention will be further described with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. The experimental procedures, in which specific conditions are not noted in the following examples, are generally carried out according to conventional conditions or according to conditions recommended by the manufacturers. All percentages, ratios, proportions, or parts are by weight unless otherwise specified. The weight volume percentage units in the present invention are well known to those skilled in the art, and refer to the weight (g) of solute in 100 ml of solution, for example. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. In addition, any methods and materials similar or equivalent to those described herein can be used in the methods of the present invention. The preferred embodiments and materials described herein are intended to be exemplary only.
In the following examples, the purified glycolide products obtained were measured for the glycolide, residual solvent, and glycolic acid dimer contents by gas chromatography, a water content by a Karl Fischer moisture meter, and a glycolic acid content by a potentiometric titration method (e.g., an automatic potentiometric titrator), which are well known in the art.
Example 1
A continuous glycolide production apparatus shown in FIG. 1 is provided. Under the working state, the cracking ring reactor, the spray cooler and the vacuum retort adopt the vacuum condition, and other equipment adopts the normal pressure condition.
The glycolide continuous production device 1000 comprises a cracking ring-forming reactor 100, a spray cooler 200 connected with an exhaust port of the cracking ring-forming reactor, a vacuum dry distiller 300 connected with a solid discharge port of the cracking ring-forming reactor, and a continuous cooling and crystallizing unit 400 coupled with the spray cooler.
The exhaust port of the cracking ring reactor 100 is disposed at the top or lateral upper portion of the cracking ring reactor, and the solid discharge port of the cracking ring reactor 100 is disposed at the bottom or lateral lower portion of the cracking ring reactor.
The side lower part of the spray cooler 200 is provided with an air inlet connected with an exhaust port of the cracking-to-loop reactor, and the top of the spray cooler is provided with a spray solvent inlet connected with a spray solvent storage tank 220 through a spray solvent supply pipeline 210, and the spray solvent supply pipeline 210 is provided with a cooler 240.
A solid-liquid separator 503-I and a dissolving stirrer 504 are arranged between the spray cooler 200 and the continuous cooling crystallization unit 400. The top of the dissolution agitator 504 is provided with a dissolution solvent inlet, which is connected to a dissolution solvent reservoir 506 through a dissolution solvent supply line 505.
The continuous cooling and crystallizing unit 400 comprises 4 crystallization kettles which are arranged in series and the temperature of which decreases in a stepwise manner, namely a first crystallization kettle 410, a second crystallization kettle 420, a third crystallization kettle 430 and a fourth crystallization kettle 440.
The first crystallization kettle 410, the second crystallization kettle 420, the third crystallization kettle 430 and the fourth crystallization kettle 440 which are connected in series adopt side feeding, the side line of the next crystallization kettle is connected with the bottom discharge port of the previous crystallization kettle, for example, the side line of the second crystallization kettle 420 is connected with the bottom discharge port of the first crystallization kettle 410, and so on. The side line of the first crystallization kettle 410 is connected with the bottom liquid outlet of the dissolution stirrer 504.
The device 1000 further comprises a solid-liquid separator 503-II connected with a bottom discharge port of the fourth crystallization kettle 440 in the continuous cooling crystallization unit 400.
The solid-liquid separator 503-II is provided with a liquid discharge port and a solid discharge port, and the liquid discharge port is connected to a dissolving solvent supply line 505 through a liquid circulation line 501.
The resulting solid was vacuum dried and transferred to product collection tank 508.
The vacuum retort 300 is a vacuum spiral-ribbon retort, and comprises a retort body 310, a spiral-ribbon rotating shaft arranged inside the retort body along the axial direction of the retort body, and a driving motor 340 in transmission connection with the spiral-ribbon rotating shaft.
The dry distiller body 310 is of a cylindrical structure, a heating jacket is arranged on the outer side of the dry distiller body, a feed inlet is formed in the feed end of the dry distiller body, a slag discharge buffer mechanism 350 is arranged at the discharge end of the dry distiller body, the feed inlet is connected with a solid discharge outlet of the cracking loop reactor, at least 1 exhaust port 380 is arranged at the top of the dry distiller body 310, and the exhaust port is connected with an air inlet in the lateral lower part of the spray cooler 200 through a gas circulation pipeline 502.
The plurality of exhaust ports are arranged at the top of the retort body at uniform intervals along the axial direction of the retort body.
Further, the slag discharge buffering mechanism 350 comprises a material collecting bin 351 arranged at the discharge end of the retort body and a lock hopper 352 connected with the material collecting bin, and a slag conveying belt 353 is arranged below the lock hopper.
The spiral ribbon rotating shaft comprises a central shaft 320 and a spiral ribbon 330 (composed of an outer spiral ribbon and an inner spiral ribbon) spirally wound and distributed on the central shaft 320 along the axial direction of the central shaft 320, the bending direction of the outer spiral ribbon is consistent with that of the inner spiral ribbon, and the outer spiral ribbon and the inner spiral ribbon are integrally formed.
Example 2(4 crystallization kettles)
Introducing about 10kg of polyglycolic acid with the weight-average molecular weight of about 3.1 ten thousand into a cracking ring-forming reactor, adding about 80g of stannous octoate, carrying out cracking ring-forming reaction at the temperature of about 260 ℃ and under the absolute pressure of about 200Pa, directly introducing the generated glycolide steam or gas-phase glycolide into a spray cooler for spray cooling, directly introducing about 3.8kg of the material which is in a viscous fluid state in the cracking ring-forming reactor into a vacuum dry distiller when the viscosity of the material in the cracking ring-forming reactor reaches about 32000cp, carrying out dry distillation treatment at the temperature of 250 ℃ and the absolute pressure of less than or equal to 5kPa, returning about 3480g of the formed glycolide steam or gas-phase glycolide into the spray cooler for spray cooling through a gas circulation pipeline (the total amount of the glycolide steam or the gas-phase glycolide generated in the cracking ring-forming reaction and the vacuum dry distillation process is about 9.68kg, and the spray solvent used in the spray cooler is formed by mixing n-propanol and isopropanol according to the mass ratio of 1:1, the total amount of spray solvent was about 98kg, the spray temperature was about-20 ℃, the absolute pressure in the spray cooler was about 200Pa), then the slurry formed by spray cooling of glycolide vapor or gas-phase glycolide in the spray cooler (about 107kg, temperature was about 11 ℃) was separated by a centrifuge, the solid material (about 8.91kg) was retained, then the solid material was transferred to a dissolution stirrer containing about 36kg of ethyl acetate solvent, the temperature was raised to about 60 ℃ with stirring, the solid material was sufficiently dissolved to obtain a pretreatment solution (about 44.91kg, in which the content of glycolic acid was 500ppm or less), then the pretreatment solution was introduced into a first crystallization tank having a temperature of about 35 ℃ for a residence time of about 100min, then introduced into a second crystallization tank having a temperature of about 18 ℃ for a residence time of about 60min, and then introduced into a third crystallization tank having a temperature of about 5 ℃, a residence time of about 30min, introducing into a fourth crystallization kettle at a temperature of about-5 deg.C for a residence time of about 8min, centrifuging about 44.91kg of slurry in the fourth crystallization kettle, drying the obtained solid at 40 deg.C under an absolute pressure of 500Pa or less for 2 hours, transferring into a product collection tank to obtain about 7.39kg of refined glycolide with a yield of 82.9% (the yield is calculated based on the solid material separated by the centrifuge), collecting about 37.52kg of the obtained mother liquor (the solvent lost after drying is collected (for example, by a heat exchanger), mixing with the mother liquor, and about 90% (about 33.77kg) of the dried refined glycolide has a very small amount of solvent, and the solvent is not counted in kg) and returning to the dissolution agitator via a liquid circulation line and a dissolution solvent supply line, and adding about 3.14kg of solvent to the dissolution agitator via a dissolution solvent supply line via a liquid transfer pump I.e., ethyl acetate), is mixed with about 8.0kg of the solid material in the next batch entering the dissolution stirrer, the temperature is raised to about 60 ℃ while stirring, so that the solid material is fully dissolved, a pretreatment solution (about 44.91kg, wherein the content of the glycolic acid dimer is less than or equal to 500ppm) is obtained, then the pretreatment solution is introduced into the first crystallization kettle to perform subsequent continuous cooling and crystallization, finally, about 44.91kg of slurry obtained in the fourth crystallization kettle is centrifugally separated, the solid is retained, and the slurry is dried for 2 hours at 40 ℃ and the absolute pressure is less than or equal to 500Pa, so that about 7.39kg of refined glycolide is obtained (continuous circulation is realized, the second circulation can bring out the material remained or accumulated in the first circulation, apparently, the amount of the refined glycolide obtained in the first batch and the second batch is the same), and the yield is 92.4% (based on the solid material fed into the dissolution stirrer), about 90% of the mother liquor (about 37.52 kg) (i.e., about 33.77kg) is returned to the dissolution agitator, and so on, to perform continuous production of refined glycolide.
Based on the steps, in the refined glycolide product produced by the first batch of the method, the glycolide content is about 99.82 wt%, the residual solvent content is about 0.13 wt%, the glycolic acid content is about 0.0103 wt%, the glycolic acid dimer content is about 0.0110 wt%, and the water content is less than 0.03 wt%;
in the refined glycolide product produced in the second batch, the glycolide content is about 99.82 wt%, the residual solvent content is about 0.13 wt%, the glycolic acid content is about 0.0109 wt%, the glycolic acid dimer content is about 0.0117 wt%, and the water content is less than 0.03 wt%;
in the refined glycolide product produced in the third batch, the glycolide content is about 99.82 wt%, the residual solvent content is about 0.13 wt%, the glycolic acid content is about 0.0113 wt%, the glycolic acid dimer content is about 0.0114 wt%, and the water content is less than 0.03 wt%.
Only three batches of refined glycolide products are listed here, but it should be noted that the pretreatment solution formed in the dissolution agitator can be continuously introduced into the first crystallization tank for continuous cooling and cooling crystallization, so that continuous production of the fourth, fifth, sixth, … … or even the Nth batch can be achieved until the content of glycolic acid dimer accumulated in the mother liquor to be returned to the dissolution agitator exceeds 1000ppm or the content of glycolic acid and/or glycolic acid dimer in the obtained refined glycolide product exceeds 0.03 wt%, the continuous production is stopped, new solvent is replaced in the dissolution agitator, and the new continuous production is restarted.
Example 3(5 crystallization kettles)
Introducing about 10kg of polyglycolic acid with the weight-average molecular weight of about 2.4 ten thousand into a cracking ring-forming reactor, adding about 25g of antimony trioxide and about 35g of diethyl zinc, carrying out cracking ring-forming reaction at about 280 ℃ and about 100Pa absolute pressure, directly introducing generated glycolide steam or gas-phase glycolide into a spray cooler for spray cooling, directly introducing about 3.1kg of material which is in a viscous fluid state in the cracking ring-forming reactor into a vacuum dry distiller when the viscosity of the material in the cracking ring-forming reactor reaches about 100000cp, carrying out dry distillation treatment at 280 ℃ and the absolute pressure of less than or equal to 5kPa, returning about 2848g of formed glycolide steam or gas-phase glycolide into the spray cooler for spray cooling through a gas circulation pipeline (the total amount of the glycolide steam or the gas-phase glycolide generated in the cracking ring-forming reaction and the vacuum dry distillation process is about 9.75kg, and the spray solvent used in the spray cooler is a mixture of n-propanol and butyl acetate according to the mass ratio of 2:1 The total amount of solvent sprayed was about 175kg, the spraying temperature was about-10 ℃, the absolute pressure in the spray cooler was about 100Pa, then the slurry (about 184kg, temperature about 2 ℃) formed by spray cooling the glycolide vapor or gas phase glycolide in the spray cooler was separated by a centrifuge, the solid material (about 9.36kg) was retained, then the solid material was transferred to a dissolution stirrer containing about 47kg of solvent (formed by mixing ethyl acetate and ethanol in a mass ratio of 4: 1), the temperature was raised to about 56 ℃ with stirring to sufficiently dissolve the solid material to obtain a pretreated solution (about 56.36kg, wherein the content of glycolic acid dimer was 500ppm or less), then the pretreated solution was introduced into a first crystallization tank having a temperature of about 42 ℃ for a residence time of about 120min, then introduced into a second crystallization tank having a temperature of about 30 ℃ for a residence time of about 90min, then the mixture is introduced into a third crystallization kettle with the temperature of about 18 ℃ and the residence time is about 50min, then the mixture is introduced into a fourth crystallization kettle with the temperature of about 10 ℃ and the residence time is about 35min, then the mixture is introduced into a fifth crystallization kettle with the temperature of about-5 ℃ and the residence time is about 15min, then about 56.36kg of slurry of the fifth crystallization kettle is centrifugally separated, the obtained solid is dried for 1 hour at the temperature of 60 ℃ and the absolute pressure of less than or equal to 500Pa, and then the dried solid is transferred into a product collecting tank, thus obtaining about 8.11kg of refined glycolide with the yield of 86.6 percent (based on the solid material obtained by the separation of a centrifugal machine), and about 48.25kg of the obtained mother liquor (the lost solvent after drying is collected (for example, by a heat exchanger), and the mother liquor is mixed, and the dried refined glycolide has a very small amount of solvent which can be ignored and is measured by kg, namely about 38.6kg) is measured by a liquid circulation pipeline, Returning a dissolving solvent supply pipeline to the dissolving stirrer, adding about 9.06kg of solvent (formed by mixing ethyl acetate and ethanol according to a mass ratio of 4: 1) into the dissolving stirrer through a dissolving solvent supply pipeline by a liquid transfer pump from a dissolving solvent storage tank, mixing with about 8.7kg of solid material in the next batch of dissolving stirrer, heating to about 56 ℃ while stirring to fully dissolve the solid material to obtain a pretreatment solution (about 56.36kg, wherein the content of the glycolic acid dimer is less than or equal to 500ppm), then introducing the pretreatment solution into a first crystallization kettle to perform subsequent continuous cooling and crystallization, finally centrifuging about 56.36kg of slurry obtained from a fifth crystallization kettle, retaining the solid, drying at 60 ℃ under an absolute pressure of less than or equal to 500Pa for 1 hour to obtain about 8.11kg of refined glycolide (realizing continuous circulation, and carrying out the material remained or accumulated in the first batch circulation process by the second batch circulation, apparently, the amount of refined glycolide obtained was the same for the first and second batches), the yield was 93.2% (calculated on the basis of the solid material fed to the dissolution stirrer), and about 80% (i.e. about 38.6kg) of the mother liquor obtained from the separation was returned to the dissolution stirrer, and so on, to perform continuous production of refined glycolide.
Based on the above steps, the refined glycolide product produced in the first batch of the method of this embodiment has a glycolide content of about 99.89 wt%, a residual solvent content of about 0.06 wt%, a glycolic acid content of about 0.0106 wt%, a glycolic acid dimer content of about 0.0104 wt%, and a water content of less than 0.03 wt%;
in the refined glycolide product produced in the second batch, the glycolide content is about 99.89 wt%, the residual solvent content is about 0.06 wt%, the glycolic acid content is about 0.0115 wt%, the glycolic acid dimer content is about 0.0107 wt%, and the water content is less than 0.03 wt%;
in the refined glycolide product produced in the third batch, the glycolide content is about 99.89 wt%, the residual solvent content is about 0.06 wt%, the glycolic acid content is about 0.0112 wt%, the glycolic acid dimer content is about 0.0114 wt%, and the water content is less than 0.03 wt%.
Only three batches of refined glycolide products are listed here, but it should be noted that the pretreatment solution formed in the dissolution agitator can be continuously introduced into the first crystallization tank for continuous cooling and cooling crystallization, so that continuous production of the fourth, fifth, sixth, … … or even the Nth batch can be achieved until the content of glycolic acid dimer accumulated in the mother liquor to be returned to the dissolution agitator exceeds 1000ppm or the content of glycolic acid and/or glycolic acid dimer in the obtained refined glycolide product exceeds 0.03 wt%, the continuous production is stopped, new solvent is replaced in the dissolution agitator, and the new continuous production is restarted.
Example 4(3 crystallization kettles)
Introducing about 10kg of polyglycolic acid with the weight-average molecular weight of about 1.1 ten thousand into a cracking ring-forming reactor, adding 10g of stannous chloride and 10g of stannic lactate, carrying out cracking ring-forming reaction at about 230 ℃ and about 1800Pa absolute pressure, directly introducing the generated glycolide steam or gas-phase glycolide into a spray cooler for spray cooling, directly introducing about 4.2kg of the material which is in a viscous fluid state in the cracking ring-forming reactor into a vacuum dry distiller when the viscosity of the material in the cracking ring-forming reactor reaches about 25000cp, carrying out dry distillation treatment at 230 ℃ and the absolute pressure of less than or equal to 5kPa, returning about 4032g of the formed glycolide steam or gas-phase glycolide into the spray cooler through a gas circulation pipeline for spray cooling (the total amount of the glycolide steam or gas-phase glycolide generated in the cracking ring-forming reaction and the vacuum dry distillation process is about 9.83kg, and the spray solvent used in the spray cooler is glycerol, the total amount of spray solvent was about 196kg, the spray temperature was about 60 ℃, the absolute pressure in the spray cooler was about 1800Pa), then the slurry (about 205kg, temperature about 76 ℃) formed by spray cooling of glycolide vapor or gas-phase glycolide in the spray cooler was separated by a centrifuge, the solid material (about 8.85kg) was retained, then the solid material was transferred to a dissolution stirrer containing about 52kg of solvent (formed by mixing acetone and methyl acetate in a mass ratio of 1: 3), the temperature was raised to about 50 ℃ with stirring, the solid material was sufficiently dissolved to obtain a pretreatment solution (about 60.85kg, in which the content of glycolic acid was 500ppm or less), then the pretreatment solution was introduced into a first crystallization tank having a temperature of about 40 ℃ for a residence time of about 95min, the acidity of the slurry was about 512ppm, followed by introduction into a second crystallization tank having a temperature of about 12 ℃, a residence time of about 30min, introducing into a third crystallization kettle at a temperature of about-5 deg.C for about 10min, centrifuging about 60.85kg of the slurry in the third crystallization kettle, drying the resulting solid at 60 deg.C under an absolute pressure of 500Pa or less for 1 hour, transferring into a product collection tank to obtain about 7.06kg of refined glycolide with a yield of 79.8% (calculated based on the solid material obtained by the centrifuge separation), collecting about 53.79kg of the resulting mother liquor (solvent lost after drying (collected by a heat exchanger, for example), mixing with the mother liquor, and returning about 80% (i.e., about 43.03kg) of the dried refined glycolide to the dissolution agitator via a liquid circulation line and a dissolution solvent supply line, and adding about 10.12kg of solvent to the dissolution agitator via a dissolution solvent supply line via a liquid transfer pump (about 43.03kg of solvent is negligible in kg), and returning the dissolution solvent to the dissolution agitator via a liquid circulation line via a dissolution solvent supply line via a liquid transfer pump Acetone and methyl acetate are mixed according to the mass ratio of 1: 3), the mixture is mixed with about 7.7kg of solid material of the next batch entering a dissolving stirrer, the temperature is raised to about 50 ℃ while stirring, the solid material is fully dissolved, a pretreatment solution (about 60.85kg, wherein the content of glycolic acid dimer is less than or equal to 500ppm) is obtained, then the pretreatment solution is introduced into a first crystallization kettle for subsequent continuous cooling and cooling crystallization, finally, about 60.85kg of slurry obtained by a third crystallization kettle is centrifugally separated, solid is reserved, the slurry is dried for 1 hour at the absolute pressure of less than or equal to 500Pa at the temperature of 60 ℃, about 7.06kg of refined glycolide is obtained (continuous circulation is realized, the second circulation can bring out the material remained or accumulated in the first circulation, the quantity of the refined glycolide obtained in the first batch and the second batch is the same apparently), the yield is 91.7 percent (the yield is calculated by taking the solid material fed into the dissolving stirrer as standard), about 80% of the mother liquor (about 53.79 kg) (i.e., about 43.03kg) is returned to the dissolution agitator, and so on, to perform continuous production of refined glycolide.
Based on the above steps, in the refined glycolide product produced in the first batch of the method of this embodiment, the glycolide content is about 99.86 wt%, the residual solvent content is about 0.09 wt%, the glycolic acid content is about 0.0126 wt%, the glycolic acid dimer content is about 0.0122 wt%, and the water content is less than 0.03 wt%;
in the refined glycolide product produced in the second batch, the glycolide content is about 99.86 wt%, the residual solvent content is about 0.09 wt%, the glycolic acid content is about 0.0119 wt%, the glycolic acid dimer content is about 0.0116 wt%, and the water content is less than 0.03 wt%;
in the refined glycolide product produced in the third batch, the glycolide content is about 99.86 wt%, the residual solvent content is about 0.09 wt%, the glycolic acid content is about 0.0120 wt%, the glycolic acid dimer content is about 0.0127 wt%, and the water content is less than 0.03 wt%.
Only three batches of refined glycolide products are listed here, but it should be noted that the pretreatment solution formed in the dissolution agitator can be continuously introduced into the first crystallization tank for continuous cooling and cooling crystallization, so that continuous production of the fourth, fifth, sixth, … … or even the Nth batch can be achieved until the content of glycolic acid dimer accumulated in the mother liquor to be returned to the dissolution agitator exceeds 1000ppm or the content of glycolic acid and/or glycolic acid dimer in the obtained refined glycolide product exceeds 0.03 wt%, the continuous production is stopped, new solvent is replaced in the dissolution agitator, and the new continuous production is restarted.
Example 5(2 crystallization kettles)
Introducing about 10kg of polyglycolic acid with the weight-average molecular weight of about 4.9 ten thousand into a cracking ring-forming reactor, adding 30g of diethyl zinc, 50g of stannous octoate and 20g of antimony trioxide, carrying out cracking ring-forming reaction at the temperature of about 272 ℃ and the absolute pressure of about 150Pa, directly introducing the generated glycolide steam or gas-phase glycolide into a spray cooler for spray cooling, directly introducing about 3.5kg of the viscous fluid material in the cracking ring-forming reactor into a vacuum dry distiller when the viscosity of the material in the cracking ring-forming reactor reaches about 66000cp, carrying out dry distillation treatment at the temperature of 270 ℃ and the absolute pressure of less than or equal to 5kPa, returning about 3080g of the formed glycolide steam or gas-phase glycolide into the spray cooler for spray cooling through a gas circulation pipeline (the total amount of the glycolide steam or gas-phase glycolide generated in the cracking ring-forming reaction and the vacuum dry distillation process is about 9.58kg, the spray cooler used was a mixture of n-butyl ether, methyl isopropyl ketone and cyclohexanone in a mass ratio of 3:1:1, the total amount of spray solvent was about 40kg, the spray temperature was about 5 ℃, and the absolute pressure in the spray cooler was about 150Pa, and then slurry (about 49kg, temperature about 58 ℃) formed by spray cooling glycolide vapor or gas-phase glycolide in the spray cooler was separated by a centrifuge, and a solid material (about 9.1kg) was retained, and then the solid material was transferred to a dissolution stirrer containing about 45kg of a solvent (formed by mixing ethyl acetate, isopropyl alcohol and methyl ethyl ketone in a mass ratio of 7:2: 1), and heated to about 60 ℃ with stirring to fully dissolve the solid material to obtain a pretreated solution (about 54.1kg, in which the content of glycolic acid dimer was not more than 500ppm), and then the pretreated solution was introduced into a first crystallization tank having a temperature of about 32 ℃, the residence time was about 60min, the acidity of the slurry was about 480ppm, the slurry was introduced into a second crystallization vessel at a temperature of about-2 ℃ for about 15min, and then about 54.1kg of the slurry in the second crystallization vessel was centrifuged, the obtained solid was dried at 60 ℃ under an absolute pressure of 500Pa or less for 1 hour, and transferred to a product collection tank, whereby about 7.17kg of refined glycolide was obtained with a yield of 78.8% (the yield was calculated based on the solid material obtained by separation with a centrifuge), about 85% (i.e., about 39.9kg) of the obtained mother liquor was returned to the dissolution stirrer via a liquid circulation line and a dissolution solvent supply line, and about 6.3kg of a solvent (obtained by mixing ethyl acetate, isopropyl alcohol, and methyl ethyl ketone at a mass ratio of 7:2: 1) was supplied from a dissolution solvent storage tank via a liquid transfer pump via the dissolution solvent supply line to the dissolution stirrer, mixing with about 7.9kg of the solid material in the next batch into the dissolution stirrer, heating to about 60 ℃ while stirring to fully dissolve the solid material to obtain a pre-treatment solution (about 54.1kg, wherein the content of glycolic acid dimer is less than or equal to 500ppm), introducing the pre-treatment solution into the first crystallization kettle to perform subsequent continuous cooling and crystallization, centrifuging about 54.1kg of slurry obtained in the second crystallization kettle to retain the solid, drying at 60 ℃ and an absolute pressure of less than or equal to 500Pa for 1 hour to obtain about 7.17kg of refined glycolide (continuous circulation is realized, the second circulation brings out the residual or accumulated material in the first circulation, and the apparent amount of the refined glycolide obtained in the first and second batches is the same), and the yield is about 90.8% (based on the solid material fed into the dissolution stirrer), about 85% (i.e., about 39.9kg) of the mother liquor obtained by separation was returned to the dissolution agitator, and so on, to perform continuous production of refined glycolide.
Based on the above steps, the refined glycolide product produced in the first batch of the method of this embodiment has a glycolide content of about 99.84 wt%, a residual solvent content of about 0.11 wt%, a glycolic acid content of about 0.0144 wt%, a glycolic acid dimer content of about 0.0148 wt%, and a water content of < 0.03 wt%;
in the refined glycolide product produced in the second batch, the glycolide content is about 99.84 wt%, the residual solvent content is about 0.11 wt%, the glycolic acid content is about 0.0140 wt%, the glycolic acid dimer content is about 0.0141 wt%, and the water content is less than 0.03 wt%;
the purified glycolide product produced in the third batch had a glycolide content of about 99.84 wt%, a residual solvent content of about 0.11 wt%, a glycolic acid content of about 0.0147 wt%, a glycolic acid dimer content of about 0.0147 wt%, and a water content of < 0.03 wt%.
Only three batches of refined glycolide products are listed here, but it should be noted that the pretreatment solution formed in the dissolution agitator can be continuously introduced into the first crystallization tank for continuous cooling and cooling crystallization, so that continuous production of the fourth, fifth, sixth, … … or even the Nth batch can be achieved until the content of glycolic acid dimer accumulated in the mother liquor to be returned to the dissolution agitator exceeds 1000ppm or the content of glycolic acid and/or glycolic acid dimer in the obtained refined glycolide product exceeds 0.03 wt%, the continuous production is stopped, new solvent is replaced in the dissolution agitator, and the new continuous production is restarted.
The foregoing is merely a preferred embodiment of the invention and is not intended to limit the scope of the invention, which is defined by the claims appended hereto, and all changes that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
Claims (9)
1. A glycolide continuous production device comprises a cracking ring-forming reactor, a spray cooler connected with an exhaust port of the cracking ring-forming reactor, a vacuum dry distiller connected with a solid discharge port of the cracking ring-forming reactor, and a crystallization unit coupled with the spray cooler.
2. The apparatus according to claim 1, wherein a solid-liquid separator I and a dissolution stirrer are connected between the spray cooler and the proximal feed inlet of the crystallization unit in this order.
3. The apparatus of claim 2, further comprising a dissolution solvent reservoir connected to the inlet of the dissolution agitator via a dissolution solvent supply line.
4. The apparatus of claim 3, wherein the outlet at the distal end of the crystallization unit is connected to a solid-liquid separator II.
5. The apparatus according to claim 4, wherein the solid-liquid separator II connected to the outlet at the distal end of the crystallization unit is connected to the supply line for the dissolution solvent through a liquid circulation line.
6. The apparatus of claim 1, wherein the spray solvent reservoir is connected to the top feed port of the spray cooler by a spray solvent supply line.
7. The apparatus of claim 1, wherein the crystallization unit is provided with at least 2 crystallization vessels in series.
8. The apparatus according to claim 7, wherein the side line of the far-end crystallization kettle in the series crystallization kettle is connected with the bottom discharge port of the adjacent near-end crystallization kettle.
9. The apparatus according to claim 1, wherein the exhaust port at the top of the vacuum retort is connected to the spray cooler through a gas circulation line.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN115246810A (en) * | 2021-04-28 | 2022-10-28 | 上海浦景化工技术股份有限公司 | Glycolide continuous production device and application thereof |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115246810A (en) * | 2021-04-28 | 2022-10-28 | 上海浦景化工技术股份有限公司 | Glycolide continuous production device and application thereof |
| CN115246810B (en) * | 2021-04-28 | 2024-03-26 | 上海浦景化工技术股份有限公司 | Glycolide continuous production device and application thereof |
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