CN114790279A - Industrial production process method of polyglycolic acid oligomer - Google Patents
Industrial production process method of polyglycolic acid oligomer Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 39
- 229920000954 Polyglycolide Polymers 0.000 title claims abstract description 36
- 239000004633 polyglycolic acid Substances 0.000 title claims abstract description 36
- 238000009776 industrial production Methods 0.000 title claims abstract description 14
- 238000006243 chemical reaction Methods 0.000 claims abstract description 87
- 239000011552 falling film Substances 0.000 claims abstract description 77
- AEMRFAOFKBGASW-UHFFFAOYSA-N Glycolic acid Chemical compound OCC(O)=O AEMRFAOFKBGASW-UHFFFAOYSA-N 0.000 claims abstract description 56
- 239000000463 material Substances 0.000 claims abstract description 19
- 239000003054 catalyst Substances 0.000 claims abstract description 18
- AEMRFAOFKBGASW-UHFFFAOYSA-M Glycolate Chemical compound OCC([O-])=O AEMRFAOFKBGASW-UHFFFAOYSA-M 0.000 claims abstract description 15
- 238000006068 polycondensation reaction Methods 0.000 claims abstract description 11
- 238000002156 mixing Methods 0.000 claims abstract description 6
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- ZANNOFHADGWOLI-UHFFFAOYSA-N ethyl 2-hydroxyacetate Chemical compound CCOC(=O)CO ZANNOFHADGWOLI-UHFFFAOYSA-N 0.000 claims description 8
- 239000007788 liquid Substances 0.000 claims description 6
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 3
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 claims description 3
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 3
- 150000001875 compounds Chemical class 0.000 claims description 3
- 230000007423 decrease Effects 0.000 claims description 3
- 239000012528 membrane Substances 0.000 claims description 3
- NORCOOJYTVHQCR-UHFFFAOYSA-N propyl 2-hydroxyacetate Chemical compound CCCOC(=O)CO NORCOOJYTVHQCR-UHFFFAOYSA-N 0.000 claims description 3
- 229910052710 silicon Inorganic materials 0.000 claims description 3
- 239000010703 silicon Substances 0.000 claims description 3
- 239000011135 tin Substances 0.000 claims description 3
- 229910052718 tin Inorganic materials 0.000 claims description 3
- 229910052719 titanium Inorganic materials 0.000 claims description 3
- 239000010936 titanium Substances 0.000 claims description 3
- 238000009826 distribution Methods 0.000 abstract description 18
- 230000000694 effects Effects 0.000 abstract description 5
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- 238000011031 large-scale manufacturing process Methods 0.000 abstract description 2
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- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 24
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 13
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- RKDVKSZUMVYZHH-UHFFFAOYSA-N 1,4-dioxane-2,5-dione Chemical compound O=C1COC(=O)CO1 RKDVKSZUMVYZHH-UHFFFAOYSA-N 0.000 description 7
- 238000004128 high performance liquid chromatography Methods 0.000 description 7
- 238000005086 pumping Methods 0.000 description 6
- HPGGPRDJHPYFRM-UHFFFAOYSA-J tin(iv) chloride Chemical compound Cl[Sn](Cl)(Cl)Cl HPGGPRDJHPYFRM-UHFFFAOYSA-J 0.000 description 6
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- 238000007151 ring opening polymerisation reaction Methods 0.000 description 3
- BYEAHWXPCBROCE-UHFFFAOYSA-N 1,1,1,3,3,3-hexafluoropropan-2-ol Chemical compound FC(F)(F)C(O)C(F)(F)F BYEAHWXPCBROCE-UHFFFAOYSA-N 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 2
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- 229920003232 aliphatic polyester Polymers 0.000 description 1
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- 235000013405 beer Nutrition 0.000 description 1
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- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 description 1
- UYCAUPASBSROMS-AWQJXPNKSA-M sodium;2,2,2-trifluoroacetate Chemical compound [Na+].[O-][13C](=O)[13C](F)(F)F UYCAUPASBSROMS-AWQJXPNKSA-M 0.000 description 1
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Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
- C08G63/02—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds
- C08G63/06—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds derived from hydroxycarboxylic acids
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
- C08G63/78—Preparation processes
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
- C08G63/78—Preparation processes
- C08G63/785—Preparation processes characterised by the apparatus used
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- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
- Polyesters Or Polycarbonates (AREA)
Abstract
The invention relates to an industrial production process method of polyglycolic acid oligomer, wherein reaction materials obtained by mixing glycolic acid or glycolate and a catalyst are subjected to normal-pressure reaction in a prepolymerization reactor, and the obtained prepolymerization product is transferred to a falling film reactor to be subjected to deep polycondensation in a vacuum state, thus completing the process. Compared with the prior art, the invention adopts the process of combining the reaction kettle with the falling film reactor, improves the reaction separation effect and the conversion rate of glycolic acid or glycolic acid ester, improves the product yield, has narrow molecular weight distribution of the obtained oligomer, is beneficial to the next depolymerization reaction, and can meet the requirement of industrialized large-scale production.
Description
Technical Field
The invention belongs to the technical field of industrial production of polyglycolic acid oligomer, and relates to an industrial production process method of polyglycolic acid oligomer.
Background
Polyglycolic acid (PGA) is an aliphatic polyester-based polymer material having the smallest number of carbon atoms in its unit, a completely decomposable ester structure, and the fastest degradation rate. PAG has good biocompatibility, so PAG is widely applied to high value-added products such as medical absorbable surgical sutures, drug sustained release, simulated human tissue materials, biodegradable polymer scaffolds, high-strength fibers (fishing lines) and the like; multilayer bottle material for packaging beverage, PET composite bottle for packaging beer, shrink film and container, hot-pressed tea cup, composite paper and other single (or multi) layer soft packaging material, agricultural biodegradable film and other fields.
Direct thermal polycondensation with glycolic acid is a simple method for producing PGA, but the molecular weight of the resulting polymer is not so high that only oligomers having a molecular weight of several thousand are generally obtained, and the polymer often has a color. The ring-opening polymerization method is the most mature method for preparing the polyhydroxy fatty acid, and can be used for preparing the polyglycolic acid by ring-opening polymerization of glycolide, the method is mature, and can obtain a polyglycolic acid product with higher relative molecular mass, and the glycolide is an important monomer of the ring-opening polymerization method, and the purity of the glycolide is directly related to the performance of the polyglycolic acid.
US2668162A discloses a process for the preparation of polyglycolic acid oligomers by melt polycondensation at first 170-. The yield of the crude glycolide can reach 93 percent at most, and the obtained crude glycolide is further purified by solvent washing and multiple solvent recrystallization.
CN107868076A discloses a method for obtaining glycolic acid oligomer by mixing glycolic acid crystals with a catalyst and carrying out three steps of normal pressure, reduced pressure and reinforced polycondensation reaction.
CN105315155B discloses a method for carrying out normal compression polymerization reaction on glycolic acid crystals under normal pressure condition until no water is distilled out; then, carrying out reduced pressure polycondensation reaction to continue the condensation reaction or ester exchange reaction until no water is distilled out; wherein, the distillation adopts a distillation column, the temperature of the distillation column is 80-110 ℃, and the theoretical plate number of the distillation column is 5-30.
CN105218512B discloses the polymerization of glycolic acid and the cleavage of polyglycolic acid in two reactors separately to produce glycolide in high yield. Firstly, glycolic acid oligomer is prepared by melt-polymerizing glycolic acid in a polymerization reaction chamber at a high temperature of 170 ℃ to 190 ℃ under reduced pressure, and adding a molecular sieve water absorbing agent.
The current stage patents are all limited to laboratory stage researches, and no reference is made on how to realize the method in industrial production. In the production of polyglycolic acid oligomer using glycolic acid or glycolic acid ester as a raw material, water or alcohol is produced during the melt polycondensation reaction, and the melt polycondensation reaction is an equilibrium reaction, and in order to increase the molecular weight, the reaction needs to be carried out at a high temperature and under a high vacuum, and the equilibrium reaction is moved to the right, whereby the produced water or alcohol is effectively separated. However, most of laboratories use kettle type reactors to carry out polymerization, which results in a large amount of back mixing of materials in the kettle, and the heat exchange surface is narrow, which is not beneficial to the removal of small molecules, so that the polyglycolic acid oligomer has low conversion rate and too wide molecular weight distribution.
Disclosure of Invention
The invention aims to provide an industrial production process method of polyglycolic acid oligomer, which solves the problems that the conversion rate of glycolic acid or glycolate is low and the molecular weight distribution of the obtained oligomer is wide when the polyglycolic acid oligomer is prepared in the prior art, thereby meeting the requirement of industrial large-scale continuous production.
The purpose of the invention can be realized by the following technical scheme:
an industrial process for preparing polyglycolic acid oligomer includes such steps as mixing glycolic acid or glycollate with catalyst, reaction under ordinary pressure in prepolymerization reactor, and deep polycondensation in falling-film reactor.
Further, the glycolate is at least one of methyl glycolate, ethyl glycolate, or propyl glycolate.
Further, the reaction temperature in the prepolymerization kettle is 110-180 ℃, and the total residence time of the reaction materials in the prepolymerization kettle is 0.5-10 h.
Furthermore, the prepolymerization reactor is provided with one or a plurality of prepolymerization reactors connected in series in sequence, and when the prepolymerization reactor is provided with a plurality of prepolymerization reactors, the reaction temperature in each prepolymerization reactor is sequentially increased along the feeding direction.
Further, the reaction temperature in the falling film reactor is 160-220 ℃, the pressure is 0.1-20 kPa, and the residence time is 0.01-2 h.
Furthermore, the outer diameter of a heat transfer pipe in the falling film reactor is 19-75 mm, preferably 19-38 mm, and the flow velocity of materials in the heat transfer pipe is 0.8-1.2 m/s.
Furthermore, a ligament-type insert is further arranged in a heat transfer tube in the falling film reactor, the thickness of the ligament-type insert is 1-1.5mm, the gap between the ligament-type insert and the inner wall of the heat transfer tube is 0.5-1.2mm, and the ratio of the unit length H of the ligament-type insert for completing 180-degree torsion to the outer diameter D of the heat transfer tube is 1-2.5: 1.
Furthermore, the liquid membrane distributor in the falling-film reactor is formed by combining a plurality of layers of disk-type distributors.
Furthermore, the falling-film reactors are provided with one or a plurality of falling-film reactors connected in series in sequence, and when the falling-film reactors are provided with a plurality of falling-film reactors, the reaction temperature of each falling-film reactor rises in sequence and the reaction pressure decreases in sequence along the feeding direction.
Further, the catalyst is a compound of titanium, tin or silicon.
Compared with the prior art, the method can effectively improve the conversion rate of the glycolic acid or glycolate and the yield of the glycolic acid or glycolate in industrialization, can obtain an oligomer with relatively narrow molecular weight distribution, and achieves better technical effects.
Drawings
FIG. 1 is a process flow diagram of the present invention;
FIG. 2 is a schematic view of the construction of a heat transfer tube;
FIG. 3 is a schematic cross-sectional view of a heat transfer tube;
the symbols in the figure illustrate:
1-prepolymerization kettle, 2-stirrer, 3-discharge pump of prepolymerization kettle, 4-falling film reactor, 5-circulating discharge pump, 6-condenser, 7-liquid film distributor, 8-heat transfer pipe, and 9-insert.
Detailed Description
The invention is described in detail below with reference to the figures and the specific embodiments. The present embodiment is implemented on the premise of the technical solution of the present invention, and a detailed embodiment and a specific operation process are given, but the scope of the present invention is not limited to the following embodiments.
The process for industrially producing a polyglycolic acid oligomer of the present invention is explained in detail below.
As shown in figure 1, the industrial production process of polyglycolic acid oligomer includes the steps of mixing glycolic acid or glycolate as raw material with catalyst, reaction in a prepolymerization reactor 1 under normal pressure, transferring the obtained prepolymerization product to a falling film reactor 4, and carrying out deep polycondensation reaction in vacuum state.
In some embodiments, the glycolate is at least one of methyl glycolate, ethyl glycolate, or propyl glycolate.
In some embodiments, the reaction temperature in the prepolymerization reactor 1 is 110-180 ℃, preferably 110-160 ℃, and more preferably 120-140 ℃, and the total residence time of the reaction materials in the prepolymerization reactor 1 is 0.5-10 hours, preferably 0.5-8 hours, and more preferably 2-6 hours.
In some embodiments, in order to enhance the progress of oligomerization, a stirrer 2 is disposed in the prepolymerization vessel 1, and the stirrer 2 may be in the form of any one of a paddle type, an anchor type, a gate type, a three-blade sweep type, and the like. Meanwhile, in order to reduce the probability of the glycolic acid or glycolate being carried out by the gas, a condenser 6 is arranged at the gas phase outlet of the prepolymerization reactor 1 for more optimization, and the raw material in the gas phase is recovered. Preferably, the prepolymerization reactor 1 is a stirring reaction kettle with a jacket or a coil, the prepolymerization temperature is 110-180 ℃, a heating medium needs to be introduced into the jacket or the coil to heat the reaction, and the suitable temperature difference between the materials and the heating medium is 20-30 ℃.
In some embodiments, the prepolymerization reactor 1 comprises one or more prepolymerization reactors 1 connected in series, and when the prepolymerization reactor 1 comprises more than one prepolymerization reactor, the reaction temperature in each prepolymerization reactor 1 increases in sequence along the feeding direction. Preferably, the number of the devices is 2 to 4, and more preferably 2.
In some embodiments, the reaction temperature in the falling film reactor 4 is 160 to 220 ℃, preferably 160 to 200 ℃, more preferably 160 to 180 ℃, the pressure is 0.1 to 20kPa, preferably 0.1 to 10kPa, more preferably 0.1 to 5kPa, and the residence time is 0.01 to 2 hours, preferably 0.01 to 1 hour, more preferably 0.01 to 0.5 hour.
More specifically, a product discharge port of the falling film reactor 4 is also provided with a circulating discharge pump 5, the discharge pump is controlled by frequency conversion, and the residence time of the materials in the reactor is changed by adjusting the circulation amount; the circulation amount is 2-15 times of the feeding amount. Specifically, a heat medium is introduced into a 4-shell pass falling-film reactor, the reaction temperature is controlled to be 160-220 ℃, and the suitable temperature difference between the material and the heat medium is 10-20 ℃.
In some embodiments, the outer diameter of the heat transfer pipe 8 in the falling film reactor 4 is 19-75 mm, preferably 19-38 mm, and a large pipe diameter is selected during vacuum operation, and the pipe diameter is used in a larger vacuum degree; the material flow velocity in the heat transfer pipe 8 is 0.8-1.2m/s, the film distribution effect is good at the moment, and the film forming is not facilitated when the flow velocity is too high or too low. Too high a flow velocity can cause the thickness of the liquid film to increase, and influence heat transfer; too low a flow rate can cause flow interruption.
In some embodiments, a ligament type insert 9 is further arranged in a heat transfer pipe 8 in the falling film reactor 4 to enhance the heat transfer coefficient of the tube side of the falling film reactor 4, the thickness of the ligament type insert 9 is 1-1.5mm, the gap between the ligament type insert 9 and the inner wall of the heat transfer pipe 8 is 0.5-1.2mm, and the ratio of the unit length H of the ligament type insert 9 completing 180 ° torsion to the outer diameter D of the heat transfer pipe 8 is 1-2.5: 1. The ligament inserts 9 may instead be spiral coils, spinning disks, or wire-wound wreaths.
In some embodiments, the liquid membrane distributor 7 in the falling-film reactor 4 may be any one of a flooding type, a plug type or a porous plate type, and preferably, the present invention is formed by combining a multi-layer disc distributor.
In some embodiments, the falling film reactor 4 is provided with one or a plurality of falling film reactors 4 connected in series, and when the falling film reactor 4 is provided with a plurality of falling film reactors, the reaction temperature of each falling film reactor 4 increases and the reaction pressure decreases sequentially along the feeding direction. Preferably, the number of the devices is 2 to 4, and more preferably 2.
In some embodiments, the catalyst is a compound of titanium, tin, or silicon. Preferably, it may be titanium dioxide, tin chloride, silicon dioxide, or the like.
In addition, in the industrial production process method, the multistage kettle type reactor and the falling film reactor 4 are operated in series, and the oligomerization reaction is divided into two stages: the first stage is normal pressure prepolymerization, which is carried out in a tank reactor, mainly because a large amount of low-boiling-point water or alcohols needs to be removed in the early stage, the stage does not need to be vacuumized, and the temperature is gradually increased in a plurality of serially connected reaction tanks, so that the entrainment of glycolic acid or glycolate can be reduced, and the raw materials are promoted to be converted towards the direction of polyglycolic acid oligomer; the second stage is vacuum polycondensation, which is carried out in a plurality of serially connected falling film reactors 4, and the falling film reactors 4 are depressurized step by step to complete deep dehydration and dealcoholization reaction and promote the forward reaction.
Compared with the traditional single-kettle reaction process, the process method has the advantages that the reaction materials are uniformly distributed on the tube wall through the film distributor, the materials in the heat transfer tube 8 are in a film shape and have high flow rate, the heat transfer coefficient and the heat transfer efficiency are greatly improved, the deep dehydration or dealcoholization reaction is facilitated, and the conversion rate of the glycollic acid or the glycollic acid ester is further improved; secondly, the reaction materials are in a film shape in the tube, so that the gas-liquid contact area is increased, and the entrainment of glycolic acid or glycolate raw materials during dehydration or dealcoholization and exhaust is reduced, thereby improving the yield of glycolic acid or glycolate; and compared with a kettle type reactor, the residence time of reaction materials in the heat transfer pipe 8 is short, the material retention in a pipe pass space is very small, and the control on the molecular weight distribution of oligomers is more facilitated.
In addition, the heat transfer pipe 8 of the falling film reactor 4 is internally provided with a ligament-type insert 9, so that the development of a fluid boundary layer is destroyed, the flow turbulence is enhanced, and the effective surface heat exchange area can be increased; meanwhile, the ligament-shaped insert 9 can generate a rotating flow, and the rotating flow can generate a remarkable centrifugal convection effect to improve the heat transfer coefficient. The experiment proves that the total heat transfer coefficient of the built-in ligament heat transfer pipe 8 is improved by more than 20 percent compared with that of a common light pipe, the low polymer obtained by the experiment has narrower molecular weight distribution and lower impurity content, and when the low polymer is used for the subsequent depolymerization reaction, useless light components and waste residues generated by depolymerization are greatly reduced, thereby being beneficial to improving the yield of the depolymerization reaction and the purity of the product glycolide.
The invention will be better understood from the following examples which are set forth for the purpose of illustration and are not to be construed as limiting the invention.
Example 1
As shown in fig. 1, the polyglycolic acid oligomer reaction system provided for implementing the process of the present invention comprises a prepolymerization reactor 1, wherein a raw material glycolic acid or glycolate feeding pipe orifice is arranged on the prepolymerization reactor 1, a stirrer 2 is arranged inside the prepolymerization reactor 1, and a gas phase outlet at the top of the prepolymerization reactor 1 is provided with a condenser 6 for condensing the raw material glycolic acid or glycolate entrained in a gas phase, so as to improve the product yield;
the bottom discharge port of the prepolymerization reactor 1 is connected with a prepolymerization reactor discharge pump 3, the prepolymer is pumped into a falling film reactor 4, deep dehydration or dealcoholization reaction is carried out in the falling film reactor 4, a feed port, a discharge port and a vacuum exhaust port are arranged on the falling film reactor 4, and polyglycolic acid oligomer generated by the reaction is conveyed out by a circulating discharge pump 5 of the falling film reactor 4.
Since polyglycolic acid oligomer produced in the falling film reactor 4 has a large viscosity, it is preferable to select a pump type suitable for transporting a fluid having a large viscosity when selecting the type of the circulating discharge pump 5; the specific type of the discharge pump 3 of the prepolymerization reactor is not limited, and the process requirements can be met.
By adopting the reaction system, in the embodiment, the mixture of glycolic acid and a catalyst tin chloride (the addition amount of the catalyst is 0.02 wt%) is continuously pumped into a prepolymerization reactor 1 at the rate of 50kg/h, the temperature of the prepolymerization reactor 1 is controlled at 160 ℃ by adopting a steam jacket, the reaction pressure is normal pressure, water vapor generated in the process enters a condenser 6 at a gas phase outlet of the prepolymerization reactor 1, the gas phase temperature at the outlet of the condenser 6 is controlled at 110 ℃, and the raw material glycolic acid is ensured not to be entrained by the water vapor; the residence time of the reactants in the prepolymerization reactor 1 is 10h, and the obtained prepolymer is continuously transferred into a falling film reactor 4 through a discharge pump 3 of the prepolymerization reactor. The heat transfer pipe 8 in the falling film reactor 4 is a light pipe with the pipe outer diameter of 19mm, and the flow velocity in the pipe is controlled to be 0.8 m/s; the falling film reactor 4 is vacuumized by adopting a water ring vacuum pump, so that the reaction pressure is maintained at 20kpa, the reaction temperature is maintained at 220 ℃ by heating heat conducting oil of a tube pass, and the residence time of reactants in the falling film reactor 4 is 2 hours. The polyglycolic acid oligomer obtained was analyzed by HPLC test, and found to have a glycolic acid conversion of 96.1%, a yield of 94.1%, a weight-average molecular weight Mw of about 5000, and a molecular weight distribution coefficient (polydispersity) of 1.8.
Example 2
Referring to example 1, two prepolymerization reactors 1 of this example are connected in series, and the specific reaction process is as follows:
continuously pumping a mixture of methyl glycolate and a catalyst tin chloride (the addition amount of the catalyst is 0.02 wt%) into a first prepolymerization kettle 1 at a speed of 100kg/h, controlling the temperature of the first prepolymerization kettle 1 at 120 ℃ by using a steam jacket, controlling the reaction pressure at normal pressure, generating methanol vapor in the process, allowing the methanol vapor to enter a condenser 6 at a gas phase outlet of the first prepolymerization kettle 1, controlling the gas phase temperature at the outlet of the condenser 6 at 80 ℃, and ensuring that a raw material methyl glycolate is not entrained by the methanol vapor; the retention time of the reactant in the first prepolymerization reactor 1 is 5h, the obtained prepolymer is continuously transferred into a second prepolymerization reactor 1 through a first prepolymerization reactor discharge pump 3, the temperature of the second prepolymerization reactor 1 is controlled at 140 ℃ by adopting a steam jacket, and the rest conditions are the same as those of the first prepolymerization reactor 1; the obtained prepolymer is continuously transferred into a falling film reactor 4 through a discharge pump 3 of a second prepolymerization kettle. A heat transfer pipe 8 in the falling film reactor 4 adopts a light pipe with the pipe outer diameter of 38mm, and the flow velocity in the pipe is controlled to be 1.2 m/s; the falling film reactor 4 adopts a water ring vacuum pump to vacuumize, so that the reaction pressure is maintained at 3kpa, the reaction temperature is maintained at 160 ℃ by virtue of heating of heat conducting oil of a tube pass, and the residence time of reactants in the falling film reactor 4 is 2 hours. The polyglycolic acid oligomer obtained was analyzed by HPLC test to find that the conversion of methyl glycolate was 96.5%, the yield was 95.6%, the weight-average molecular weight Mw was about 5000, and the molecular weight distribution coefficient (polydispersity) was 1.8.
Example 3
Referring to example 1, this example also continuously pumps a mixture of ethyl glycolate and tin chloride (catalyst addition 0.02 wt%) as a catalyst into prepolymerization reactor 1 at a rate of 50kg/h, wherein prepolymerization reactor 1 is controlled at 160 ℃ by using a steam jacket and the reaction pressure is atmospheric pressure, ethanol vapor generated in the process enters condenser 6 at the outlet of gas phase of prepolymerization reactor 1, the temperature of gas phase at the outlet of condenser 6 is controlled at 90 ℃ to ensure that the raw material ethyl glycolate is not entrained by the ethanol vapor; the residence time of the reactants in the prepolymerization reactor 1 is 10 hours, and the obtained prepolymer is continuously transferred into a falling film reactor 4 through a discharge pump 3 of the prepolymerization reactor. The heat transfer pipe 8 in the falling film reactor 4 adopts a light pipe with the pipe outer diameter of 38mm, a ligament-type insert 9 is arranged in the light pipe to enhance heat transfer, the flow speed in the pipe is controlled to be 1.0m/s, the thickness of the ligament-type insert 9 is 1mm, the gap between the ligament-type insert and the inner wall of the heat transfer pipe 8 is 0.5mm, and the ratio of the unit length H (namely ligament pitch) of the ligament-type insert for completing 180-degree torsion to the heat transfer pipe outer diameter D is 1; the falling film reactor 4 adopts a water ring vacuum pump for vacuum pumping, so that the reaction pressure is maintained at 20kpa, the reaction temperature is maintained at 220 ℃ by means of heating of heat conducting oil of a tube pass, and the residence time of reactants in the falling film reactor 4 is 2 hours. The polyglycolic acid oligomer obtained was analyzed by HPLC test to find that the conversion of ethyl glycolate was 99.1%, the yield was 96.6%, the weight-average molecular weight Mw was about 5000, and the molecular weight distribution coefficient (polydispersity) was 1.7.
Example 4
Referring to example 1, the prepolymerization reactor 1 of this example is provided with four groups in series, and the falling film reactor 4 is also provided with four groups in series, and the specific reaction process is as follows:
continuously pumping a mixture of methyl glycolate and a catalyst tin chloride (the adding amount of the catalyst is 0.02 percent by weight) into a first prepolymerization reactor 1 at a speed of 200kg/h, controlling the temperature of the first prepolymerization reactor 1 at 110 ℃ by adopting a steam jacket, controlling the reaction pressure at normal pressure, generating methanol vapor in the process, entering the condenser 6 at a gas phase outlet of the first prepolymerization reactor 1, controlling the gas phase temperature at the outlet of the condenser 6 at 80 ℃, and ensuring that a raw material of methyl glycolate is not entrained by the methanol vapor; the retention time of the reactant in the first prepolymerization reactor 1 is 0.5h, the obtained prepolymer is continuously transferred into a second prepolymerization reactor 1 through a first prepolymerization reactor discharge pump 3, the temperature of the second prepolymerization reactor 1 is controlled at 120 ℃ by adopting a steam jacket, and the rest conditions are the same as those of the first prepolymerization reactor 1; continuously transferring the obtained prepolymer into a third prepolymerization kettle 1 through a discharge pump 3 of the second prepolymerization kettle, wherein the temperature of the third prepolymerization kettle 1 is controlled at 130 ℃ by adopting a steam jacket, and the rest conditions are the same as those of the first prepolymerization kettle 1; the obtained prepolymer is continuously transferred into a fourth prepolymerization reactor 1 through a third prepolymerization reactor discharge pump 3, the temperature of the fourth prepolymerization reactor 1 is controlled at 150 ℃ by adopting a steam jacket, and the rest conditions are the same as those of the first prepolymerization reactor 1.
Finally, the obtained prepolymer is continuously transferred into a first falling film reactor 4 through a fourth prepolymerization kettle discharge pump 3. A heat transfer pipe 8 in the falling film reactor 4 adopts a light pipe with the pipe diameter of 38mm, a tie-shaped insert 9 is arranged in the heat transfer pipe to enhance heat transfer, the flow speed in the pipe is controlled to be 1.0m/s, the thickness of the tie-shaped insert 9 is 1.5mm, the gap between the tie-shaped insert and the inner wall of the heat transfer pipe 8 is 1.2mm, and the ratio of the unit length H (namely tie pitch) of the tie-shaped insert for completing 180-degree torsion to the outer diameter D of the heat transfer pipe is 2.5; the falling film reactor 4 adopts a water ring vacuum pump for vacuum pumping, the falling film reactor 4 adopts four serial operations, the reaction temperature of the first falling film reactor is 160 ℃, the reaction pressure is 20kpa, and the retention time is 0.01 h; the reaction temperature of the second falling film reactor 4 is 180 ℃, the reaction pressure is 15kpa, and the retention time is 0.01 h; the reaction temperature of the third falling film reactor 4 is 200 ℃, the reaction pressure is 2kpa, and the retention time is 0.01 h; the reaction temperature of the fourth falling film reactor 4 is 220 ℃, the reaction pressure is 0.1kpa, and the retention time is 0.01 h; the polyglycolic acid oligomer obtained was analyzed by HPLC test to find that the conversion of methyl glycolate was 98.1%, the yield was 95.9%, the weight-average molecular weight Mw was about 4000, and the molecular weight distribution coefficient (polydispersity) was 1.7.
Example 5
Referring to embodiment 1, the prepolymerization reactor 1 of this embodiment is connected in series with two sets, and the falling film reactor 4 is also connected in series with two sets, the specific reaction process is:
continuously pumping a mixture of methyl glycolate and a catalyst tin chloride (the addition amount of the catalyst is 0.02 wt%) into a first prepolymerization kettle 1 at a speed of 100kg/h, controlling the temperature of the first prepolymerization kettle 1 at 120 ℃ by adopting a steam jacket, controlling the reaction pressure at normal pressure, generating methanol vapor in the process, allowing the methanol vapor to enter a condenser 6 at a gas phase outlet of the prepolymerization kettle 1, controlling the gas phase temperature at an outlet of the condenser 6 at 80 ℃, and ensuring that a raw material, namely methyl glycolate, is not entrained by the methanol vapor; the retention time of the reactant in the first prepolymerization kettle 1 is 5 hours, the obtained prepolymer is continuously transferred to a second prepolymerization kettle 1 through a discharge pump 3 of the first prepolymerization kettle, the temperature of the second prepolymerization kettle 1 is controlled at 140 ℃ by adopting a steam jacket, and the rest conditions are the same as those of the first prepolymerization kettle 1; the obtained prepolymer is continuously transferred into a first falling film reactor 4 through a discharge pump 3 of a second prepolymerization kettle. A heat transfer pipe 8 in the falling film reactor 4 adopts a light pipe with the pipe diameter of 38mm, a ligament-shaped insert 9 is arranged in the falling film reactor to strengthen heat transfer, the flow speed in the pipe is controlled to be 1.2m/s, the thickness of the ligament-shaped insert 9 is 1.2mm, the gap between the ligament-shaped insert and the inner wall of the heat transfer pipe 8 is 1mm, and the ratio of the unit length H (namely ligament pitch) of the ligament-shaped insert for completing 180-degree torsion to the outer diameter D of the heat transfer pipe is 1.5; the falling film reactor 4 adopts a water ring vacuum pump for vacuum pumping, the falling film reactor 4 adopts two series operations, the reaction temperature of the first falling film reactor is 160 ℃, the reaction pressure is 5kpa, and the retention time is 0.5 h; the reaction temperature of the second falling film reactor 4 is 180 ℃, the reaction pressure is 3kpa, and the residence time is 0.5 h. The polyglycolic acid oligomer obtained finally was analyzed by HPLC test to find that the conversion of methyl glycolate was 99.5%, the yield was 98.6%, the weight-average molecular weight Mw was about 5000, and the molecular weight distribution coefficient (polydispersity) was 1.6.
Comparative example 1
The falling film reactor in example 1 was changed to a tank reactor, and the remaining conditions were exactly the same as in example 1, and the obtained polyglycolic acid ester oligomer was analyzed by HPLC test to have a conversion of 93.2% of ethyl glycolate, a yield of 85%, a weight average molecular weight Mw of about 5000, and a molecular weight distribution coefficient (polydispersity) of 2.1.
Comparative example 2
The conditions of the falling film reactor and the ligament-type insert in example 3 were completely the same as those in example 3 except that the reactor was changed to a tank reactor, and the obtained polyglycolic acid ester oligomer was analyzed by HPLC test to show that the conversion of ethyl glycolate was 93.2%, the yield was 83%, the weight-average molecular weight Mw was about 5000, and the molecular weight distribution coefficient (polydispersity coefficient) was 2.1.
The weight average molecular weight and molecular weight distribution coefficient test methods are as follows:
weight average molecular weight (Mw) and molecular weight distribution) Mw/Mn was determined using Gel Permeation Chromatography (GPC).
The test conditions were as follows:
the instrument comprises the following steps: WatersIA type GPC instrument (Millipore, USA). The device consists of a 590 model pump, a U6k model sample injector, a column thermostat, a 490 model differential refractometer index detector and a 745 model data processor; the gel column was Shodex HFIPSOM linear column (Japanese Showa Denko Co.).
Solvent: hexafluoroisopropanol (Sigma, usa, ready for distillation) was prepared as a mobile phase in hexafluoroisopropanol solvent at 20mM concentration of sodium trifluoroacetate (alatin reagent (shanghai) ltd).
Flow rate: 1.0mL/min
Temperature: 40 deg.C
The weight average molecular weight (Mw), the number average molecular weight (Mn) and the molecular weight distribution coefficient (Mw/Mn) were found from the obtained elution curve.
In conclusion, the invention adopts the process of combining the reaction kettle with the falling film reactor, improves the reaction separation effect and the conversion rate of glycolic acid or glycolate, improves the product yield, has narrow molecular weight distribution of the obtained oligomer, is beneficial to the next depolymerization reaction, and can meet the requirement of industrialized large-scale production.
The embodiments described above are described to facilitate an understanding and appreciation of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make modifications and alterations without departing from the scope of the present invention.
Claims (10)
1. An industrial production process of polyglycolic acid oligomer is characterized in that reaction materials obtained by mixing glycolic acid or glycolate as raw materials with a catalyst are subjected to normal-pressure reaction in a prepolymerization reactor, and the obtained prepolymerization product is transferred to a falling film reactor to be subjected to deep polycondensation in a vacuum state, thus completing the process.
2. The process of claim 1, wherein the glycolic acid ester is at least one of methyl glycolate, ethyl glycolate or propyl glycolate.
3. The industrial production process of polyglycolic acid oligomer according to claim 1, wherein the reaction temperature in the prepolymerization reactor is 110-180 ℃, and the total residence time of the reaction materials in the prepolymerization reactor is 0.5-10 h.
4. The method according to claim 1, wherein the prepolymerization vessel is provided with one or more prepolymerization vessels, and when the prepolymerization vessel is provided with a plurality of prepolymerization vessels, the reaction temperature in each prepolymerization vessel is increased in the feeding direction.
5. The industrial production process method of polyglycolic acid oligomer according to claim 1, wherein the reaction temperature in the falling film reactor is 160-220 ℃, the pressure is 0.1-20 kPa, and the residence time is 0.01-2 h.
6. The industrial production process method of polyglycolic acid oligomer according to claim 1, wherein the outer diameter of the heat transfer pipe in the falling film reactor is 19-75 mm, and the material flow rate in the heat transfer pipe is 0.8-1.2 m/s.
7. The method of claim 1 or 6, wherein the heat transfer tube in the falling film reactor is further provided with a ligament-type insert, the thickness of the ligament-type insert is 1-1.5mm, the gap between the ligament-type insert and the inner wall of the heat transfer tube is 0.5-1.2mm, and the ratio of the unit length H of the ligament-type insert completing 180 ° torsion to the outer diameter D of the heat transfer tube is 1-2.5: 1.
8. The industrial production process method of polyglycolic acid oligomer according to claim 1, wherein the liquid membrane distributor in the falling-film reactor is a combination of multi-layer disk-type distributors.
9. The method according to claim 1, wherein the falling-film reactor comprises one or more falling-film reactors connected in series, and when the falling-film reactors comprise a plurality of falling-film reactors, the reaction temperature of each falling-film reactor increases and the reaction pressure decreases in sequence along the feeding direction.
10. The process of claim 1, wherein the catalyst is a compound of titanium, tin or silicon.
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