CN117964600A - Glycolide composition, preparation method thereof and polyglycolic acid - Google Patents
Glycolide composition, preparation method thereof and polyglycolic acid Download PDFInfo
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Abstract
The invention provides a glycolide composition, a preparation method thereof and polyglycolic acid. Comprises greater than or equal to 99 weight percent glycolide and no greater than 1 weight percent glycolic acid oligomer, based on the weight of the composition; the average degree of polymerization of the glycolic acid oligomer is 8 or more. The prepared glycolide composition has lower carboxyl end groups, contains a macromolecular initiator, and generates polyglycolic acid with higher intrinsic viscosity after polymerization.
Description
Technical Field
The invention relates to the field of glycolide, in particular to a glycolide composition, a preparation method thereof and polyglycolic acid.
Background
Polyglycolic acid (PGA) is a biodegradable polymer material having excellent biocompatibility. It is also the first synthetic polymer approved by the U.S. Food and Drug Administration (FDA) for human implantation. PGA is widely used in the fields of medical absorbable surgical suture lines, medical slow-release and controlled-release medical products with high added value for simulating human tissue materials and the like. Because of its excellent mechanical properties and water vapor-oxygen barrier properties, it has also been used in the field of fracturing balls for oil field exploitation and barrier packaging materials.
The currently accepted preparation method of the high molecular weight PGA is ring-opening polymerization of glycolide, and the PGA used for medical suture lines, stents, dressings and fracturing balls needs to be polymerized by using polymer grade glycolide, and the glycolide needs to have high purity and low carboxyl end group content so as to meet the requirements of preparing spinning grade or injection molding grade PGA after polymerization, and the carboxyl end group content is usually at least less than 10 mu mol/g, preferably less than 3 mu mol/g.
At present, the most mature glycolide synthesis method at home and abroad is a polycondensation-depolymerization method using glycolic acid as a raw material, and Chinese patent No. CN105272958A discloses a glycolide preparation method, which is an example of preparing crude glycolide by using a polycondensation-pyrolysis method. The crude glycolide obtained by the depolymerization reaction generally contains various impurities such as water, glycolic acid, and glycolic acid oligomers, and it is necessary to control the content of impurities which are difficult to remove in the crude glycolide in order to reduce the pressure and cost of the purification step. One purification means or a combination of purification means is generally reused to sufficiently remove the above-mentioned various impurities.
The reported refining method adopts an organic solvent to purify glycolide, and the glycolide is purified by repeated recrystallization, repeated alcohol washing and recrystallization-alcohol washing coupling; for example, literature (pensons, cui Aijun, yin Fanghua, et al. Alcohol wash purification of glycolide and effect on open-loop polymerization [ J ]. Chemical progress, 2015,34 (04): 1059-1063.) uses a large number of organic solvents to purify crude glycolide by multiple washes.
The reported refining method also adopts a scheme without organic solvent to purify glycolide, and the glycolide is purified by multistage rectification and multistage melt crystallization; chinese patent No. CN106928180a discloses a scheme for purifying glycolide by continuous rectification in a multistage rectification column; patent WO2014139730A1 discloses a purification scheme combining rectification with multistage melt crystallization; it is well known to those skilled in the art that glycolide has a thermal degradation phenomenon, which can undergo ring-opening polymerization in a molten state to produce low molecular weight PGA, which is more likely to occur under the catalysis of a protonic acid. At the same time, however, glycolide in the molten state is easily transferred, and is almost unavoidable in the industrial-scale pyrolysis collection or purification process. The temperature of the tower kettle for purifying the crude glycolide by multistage rectification is generally higher than 200 ℃, the crude glycolide is rapidly thermally degraded and deteriorated to be a glycolic acid oligomer when being heated in the tower kettle, the purification yield is low, and the rectification method can not separate the glycolide from impurities azeotroped with the glycolide, so that only rectification is used, and the purity after purification is limited.
The removal of small molecule impurities in glycolide is easier because at room temperature, small molecule impurities, predominantly polar molecules, have a higher solubility in organic solvents commonly used in the art. Chinese patent CN107868074a discloses a technical scheme for purifying glycolide by evaporation crystallization-extraction combination, which states that "the high molecular weight impurity in glycolide is usually a glycolic acid oligomer with a polymerization degree of 4 or more"; according to the technical scheme, the crude glycolide is collected in a cold state, and the removal effect of high molecular weight impurities in the glycolide is represented by a method for measuring the content of carboxyl end groups, so that the purpose of removing the high molecular weight impurities is achieved. However, the actual content of high molecular weight impurities, the molecular weight, was not tested, but only example 3 produced refined glycolide having a terminal carboxyl group slightly below 10. Mu. Mol/g.
Disclosure of Invention
In order to solve the technical problems in the prior art, the invention provides a glycolide composition, a preparation method thereof and polyglycolic acid.
The invention provides a novel glycolide composition which has lower terminal carboxyl groups, contains a macromolecular initiator, and generates polyglycolic acid with higher intrinsic viscosity after polymerization.
The invention solves the problems that the cold collection of crude glycolide is not easy to transfer and the content of refined glycolide acid is high in the prior art, the cold collection reduces the residence time of a crude glycolide melt in a molten state, the content of glycolic acid oligomer is reduced, the method is favorable for improving the purity of products, but has the defects of difficult transfer and high energy consumption, any impurity in glycolide is considered to be unfavorable for the preparation of polyglycolic acid in the prior art, the problem of the prior art in impurity cognition is overcome, and the invention provides a simple glycolide preparation and purification method, and a glycolide composition with low acid content and a certain amount of ring-opening polymerization initiator is prepared for ring-opening polymerization, so that the polyglycolic acid with higher intrinsic viscosity can be polymerized. The preparation process provided by the invention can allow glycolide to stay in a molten state for a plurality of hours, and has the advantages of small dosage of organic solvent, low content of refined glycolide acid and easiness in industrial preparation.
It is an object of the present invention to provide a glycolide composition comprising 99% by weight or more of glycolide and 1% by weight or less of a glycolic acid oligomer based on the weight of the composition; the average degree of polymerization of the glycolic acid oligomer is 8 or more.
In a preferred embodiment of the present invention,
Comprises from 99.0% to 99.9% by weight of glycolide and from 0.1% to 1% by weight of glycolic acid oligomer, based on the weight of the composition.
In a preferred embodiment of the present invention,
The average polymerization degree of the glycolic acid oligomer is more than or equal to 14.
Regarding the average degree of polymerization of glycolic acid oligomer, the inventors have studied the following reasoning: for the same mass fraction of glycolic acid oligomers in the composition, the higher its average degree of polymerization, the lower its acid content contributed by the terminal carboxyl groups to the composition, e.g., 8000ppm of glycolic acid thirty-polymers may contribute 4.6 μmol/g of acid content to the composition, while 8000ppm of glycolic acid pentapolymers may contribute 9.0 μmol/g of acid content, and when the average degree of polymerization of the glycolic acid oligomers is sufficiently high, the acid content contributed by no more than 1% of the composition weight does not affect the normal progress of ring-opening polymerization. And the high molecular weight glycolic acid oligomer with a specific polymerization degree can still realize the low carboxyl end group content of the glycolide composition by remaining in the glycolide with a certain content.
In a preferred embodiment of the present invention,
The carboxyl end group content of the glycolide composition is less than or equal to 7 mu mol/g; preferably, the carboxyl end group content thereof is 3. Mu. Mol/g or less.
The second object of the present invention is to provide a method for preparing glycolide composition, comprising the steps of:
(1) Glycolic acid polycondensate is prepared by polycondensation reaction of glycolic acid, or glycolic acid derivative polycondensate is prepared by transesterification reaction of glycolic acid derivative;
(2) Carrying out pyrolysis reaction on the obtained glycolic acid polycondensate or glycolic acid derivative polycondensate, and condensing a gas phase to obtain a glycolide crude product;
(3) And purifying the obtained crude glycolide product to obtain the glycolide composition.
In a preferred embodiment of the present invention,
The glycollic acid is at least one of glycollic acid crystals and glycollic acid aqueous solution;
The glycollic acid derivative is methyl glycollate;
Preferably, the method comprises the steps of,
The glycolic acid crystals are glycolic acid having a purity of greater than 97 wt.% and containing no more than 2000ppm aldehyde; and/or the number of the groups of groups,
The aqueous solution of glycolic acid has a mass concentration of 50% or more and contains not more than 2000ppm of aldehyde based on the mass of glycolic acid; and/or the number of the groups of groups,
The methyl glycolate is methyl glycolate with purity higher than 95 weight percent and contains no more than 1 weight percent of alcohol, acid and other esters respectively; and/or the number of the groups of groups,
The weight average molecular weight of the glycolic acid polycondensate or glycolic acid derivative polycondensate is less than or equal to 5 ten thousand; preferably 2.5 ten thousand or less.
In a preferred embodiment of the present invention,
Step (1),
The condensation polymerization of glycolic acid crystal or aqueous solution of glycolic acid is carried out by atmospheric pressure and then reduced pressure,
The polycondensation reaction step comprises the following steps:
a) The polycondensation time at the normal pressure stage is within 4 hours, the polycondensation temperature is 110-220 ℃, and the polycondensation pressure is 0.09-0.11 MPa;
b) The polycondensation time in the decompression stage is within 4 hours, the polycondensation temperature is 110-220 ℃, the polycondensation pressure is 0.1-10 kPa, until no water is distilled out, and the glycolic acid polycondensate is obtained;
The transesterification of methyl glycolate is carried out by positive pressure and then decompression, and the transesterification step comprises the following steps:
a) The polycondensation time in the positive pressure stage is within 4 hours, the polycondensation temperature is 150-230 ℃, and the polycondensation pressure is 0.11-0.55 MPa;
b) The polycondensation time in the decompression stage is within 4 hours, the polycondensation temperature is 150-230 ℃, the polycondensation pressure is 0.1-10 kPa, and the methyl glycolate polycondensate is obtained until no methanol is distilled out.
The reaction temperature is increased, and the reaction time can be shortened by using a catalyst.
In a preferred embodiment of the present invention,
Step (2),
The gas phase product in the pyrolysis reaction is distilled out of the reaction system in a straight-run mode or is distilled out of the reaction system through a rectifying tower, and is condensed into molten crude glycolide;
the pyrolysis reaction is carried out under reduced pressure, and the pyrolysis pressure is 0.1 to 10kPa, preferably 3 to 5kPa; the pyrolysis temperature is 230-290 ℃; a catalyst may be used;
condensing the gaseous glycolide into molten glycolide by a condensing medium (for example, hot water at 80-95 ℃), wherein the temperature of the molten glycolide is 75-110 ℃; preferably 80 to 95 ℃;
the time before entering step (3) after the gas phase has condensed to the molten state is not more than 4 hours, preferably not more than 2 hours;
After condensing to the molten state, there may be a waiting period before entering the purification equipment, during which oligomer impurities can be generated by reaction, so that the waiting period should be controlled as short as possible;
the glycolide crude product comprises no more than 2% by weight of glycolic acid oligomers, based on the total weight of the glycolide crude product.
Glycolide has a thermal degradation phenomenon, and can undergo ring-opening polymerization reaction in a molten state to generate low molecular weight PGA, the side reaction is more easy to occur under the catalysis of protonic acid and the initiation of alcoholic hydroxyl groups, and crude glycolide can be in a molten state in a pyrolysis reaction device, a straight distillation device, a rectification device and a molten state collection device, so that a crude glycolide product can contain a certain content of glycolic acid oligomer.
In a preferred embodiment of the present invention,
The step (3) specifically comprises the steps of,
(3-1) Extracting the glycolide crude product with a solvent of a saturated monohydric alcohol or a complex solvent of a saturated monohydric alcohol and other solvents to obtain a glycolide-containing phase and an impurity-containing phase; the extraction temperature is 20-40 ℃;
(3-2) crystallizing the glycolide-containing phase obtained, and extracting a solid phase;
preferably, the steps (3-1) and (3-2) are repeated 1 to 2 times.
Step (3-1) defines a solvent and a preferred extraction temperature, and a large amount of acidic impurities (about 500 mu mol/g) in the crude glycolide in step (3-1) is contacted with the glycolide, and the acid is a catalyst for the self-polymerization of the glycolide, and if the temperature is not limited, the self-polymerization can rapidly occur to generate oligomer impurities, and the invention can sufficiently remove the impurities with low polymerization degree at the preferred temperature and inhibit the rapid and large generation of the oligomer impurities; .
Step (3-1) obtaining a solid filter cake containing glycolide and impurities, wherein the solid filter cake is solid if drying operation is carried out; heating the solid state to obtain a molten state, and performing melt crystallization to further purify; the solid phase containing a small amount of solvent is heated together to above the melting point of glycolide, but the solvent is insufficient to completely dissolve the glycolide, and the undissolved portion of the glycolide is present in the molten form.
In a preferred embodiment of the present invention,
Step (3-2),
The method for extracting the solid phase is filtration or drying; and/or the number of the groups of groups,
The melting temperature of the glycolide-containing phase is 75-150 ℃; preferably 75-90 ℃;
the residence time of the glycolide in the molten state is not more than 2.5 hours, which means that the glycolide-containing phase temperature is maintained at 70 to 150 ℃ for a period of time during which a glycolic acid oligomer of a desired degree of polymerization can be produced.
The glycolide exists in a molten state in two stages of the steps of pyrolysis condensation into a liquid state and purification (3-2), and after the glycolide is pyrolyzed and condensed into the liquid state, a large amount of acid exists in the liquid crude glycolide, so that the self-polymerization reaction can be catalyzed to occur rapidly, and the time in the liquid state is limited; in the purification step (3-2), since most of the acid has been removed through the step (3-1), a certain residence time in the molten state is allowed in (3-2) and the amount of oligomer of a specific polymerization degree is produced.
In a preferred embodiment of the present invention,
The solvent of the saturated monohydric alcohol is saturated monohydric alcohol with 1-6 carbon atoms; preferably a saturated monohydric alcohol having 1 to 5 carbon atoms; more preferably at least one of methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol, and isobutanol;
The other solvent is a solvent with the solubility of glycolide in the solvent being more than or equal to 10g of glycolide per hundred g of solvent at 25 ℃, the other solvent is preferably at least one of ethyl acetate, acetone, ethylene glycol dimethyl ether and polyalcohol ether, and saturated monohydric alcohol can be prepared into a compound solvent with organic solvents such as ethyl acetate, acetone and polyalcohol ether for impurity extraction of crude glycolide;
The mass ratio of the solvent to the glycolide crude product is (1-10): 1, preferably (2 to 4): 1.
It is a further object of the present invention to provide a glycolide composition prepared by the above process.
The glycolide composition comprises 99% by weight or more of glycolide and 1% by weight or less of a glycolic acid oligomer; preferably comprises from 99.0% to 99.9% by weight glycolide and from 0.1% to 1% by weight glycolic acid oligomer; the average degree of polymerization of the glycolic acid oligomer is 8 or more; preferably 14 or more.
In a preferred embodiment of the present invention,
The glycolide composition further comprises water or a saturated monohydric alcohol; the content of water in the glycolide composition is less than or equal to 300ppm; the content of the saturated monohydric alcohol is less than or equal to 500ppm, and the melting point of the saturated monohydric alcohol is less than or equal to 25 ℃.
The content range of water and saturated monohydric alcohol (from the refining solvent) is a specification for the quality of the product, if glycolide contains water or saturated monohydric alcohol outside the content range (out of specification), the excess hydroxyl groups will significantly reduce the intrinsic viscosity, molecular weight of the polymer.
The fourth object of the present invention is to provide a glycolic acid oligomer prepared from the glycolide composition, wherein the glycolic acid oligomer is obtained by separating the glycolide composition; preferably, the glycolic acid oligomer is obtained by dissolving the glycolic acid oligomer in a solvent to prepare a solution, centrifuging the solution, and drying the insoluble sediment.
It is a fifth object of the present invention to provide a glycolide composition comprising the above-produced glycolic acid oligomer, said glycolide composition further comprising glycolide, based on the weight of the composition, comprising 99% by weight or more of glycolide and not more than 1% by weight of glycolic acid oligomer; preferably, it comprises from 99.0% to 99.9% by weight of glycolide and from 0.1% to 1% by weight of glycolic acid oligomer.
It is a sixth object of the present invention to provide polyglycolic acid produced from the glycolide composition.
The glycolide composition of the present invention is used as a starting material for ring-opening polymerization, and for example, can be used as a polymerized monomer of polyglycolic acid, or can be used in combination with other cyclic monomers, for example, lactide, caprolactone, etc., as one of polymerized monomers of the copolymer. When the above glycolide composition is used for ring-opening polymerization, the inventors have studied the following reasoning: because glycolide compositions contain no more than 1% by weight of the composition of glycolic acid oligomer and the average degree of polymerization is high, the glycolic acid oligomer contributes insufficient acid content to adversely affect the polymerization and acts as a macroinitiator in ring-opening polymerization, resulting in an acceleration of the initiation process of the polymerization and a greater specific gravity of the high molecular weight fraction in the molecular weight distribution during the polymerization, ultimately leading to an increase in the intrinsic viscosity of the polymer.
Compared with the prior art, the invention has the beneficial effects that:
The invention can completely remove the impurities with low polymerization degree in the crude glycolide product, and the impurities with low polymerization degree contribute most of carboxyl groups (one small molecule end is provided with one carboxyl group), so that the prepared glycolide composition has low carboxyl end group content (low acid value); meanwhile, the invention can retain impurities with higher polymerization degree, the part of the impurities contribute little carboxyl (one long-chain terminal only carries one carboxyl and one alcoholic hydroxyl capable of initiating), and the impurities can be used as a macromolecular initiator in ring-opening polymerization, and when the macromolecular initiator is used in ring-opening polymerization, the ring-opening polymerization reaction is not influenced, and the polyglycolic acid generated after polymerization is promoted to have higher intrinsic viscosity.
The saturated alcohol with low carbon number has stronger extraction capability to impurities with low polymerization degree, can completely remove the impurities with low polymerization degree in the crude glycolide product, has lower extraction temperature, limits the self-polymerization of the glycolide to generate polymer impurities in the presence of acidic impurities, and can stay in a molten state for a certain time after most of acid is extracted and removed, so that the heat degradation of the glycolide can not be caused, and polyglycolic acid with higher polymerization degree generated in the earlier stage can be reserved, and the content of the polyglycolic acid is controlled in a certain range more accurately.
Detailed Description
The present invention is described in detail below with reference to specific embodiments, and it should be noted that the following embodiments are only for further description of the present invention and should not be construed as limiting the scope of the present invention, and some insubstantial modifications and adjustments of the present invention by those skilled in the art from the present disclosure are still within the scope of the present invention.
The starting materials used in the examples were all conventional commercially available.
The testing method comprises the following steps:
The acid content determination method of the crude glycolide and the glycolide comprises the following steps:
Determining the acid content in the crude glycolide by using an acid-base titration method; the specific operation is as follows: dissolving a crude glycolide sample in about 30mL of dry dimethyl sulfoxide, and dropwise adding a plurality of bromophenol blue indicator solutions into the solution after the crude glycolide sample is dissolved, wherein the solution is yellow; titrating the solution by using a benzyl alcohol dilute solution of sodium hydroxide with known concentration, wherein the end point is when the color of the solution changes from yellow to green; the carboxyl end group content (in. Mu. Mol) in glycolide was calculated by calculating the volume of sodium hydroxide solution used to reach the end of titration, divided by the mass of the crude glycolide sample to give the crude glycolide acid content (in. Mu. Mol/g).
Method for determining content of glycolic acid oligomer in crude glycolide and glycolide:
Dissolving 5 g of crude glycolide or a purified glycolide sample in 50 g of dry ethyl acetate, centrifuging the solution at a high speed (the centrifugal speed is 10000rpm for 10 min) after the glycolide is completely dissolved at a dissolving temperature of 25 ℃ to fully deposit insoluble substances in the solution; pouring and discarding the centrifuged supernatant, adding 20 g of dry ethyl acetate to the sediment, fully mixing, and dissolving the residual glycolide at the mixing temperature of 25 ℃, centrifuging at high speed again, and pouring and discarding the centrifuged supernatant; the deposit was dried in vacuo (4 hours at 40 ℃) and weighed, and the glycolic acid oligomer content was obtained by dividing the mass of the crude glycolide or glycolide sample.
Method for measuring average molecular weight (average degree of polymerization) of glycolic acid oligomer in glycolide:
Determining molecular weight information for glycolic acid oligomers using ultra-high performance polymer chromatography (APC); taking hexafluoroisopropanol containing 5mM sodium trifluoroacetate as a mobile phase, dissolving at least 7 PMMA standard samples with the Mp (peak molecular weight) ranging from 300 to 10000 in hexafluoroisopropanol to prepare a solution with the concentration of 2mg/mL, and carrying out sample injection measurement to establish a standard curve; and dissolving the glycolic acid oligomer to be detected in hexafluoroisopropanol to prepare a solution with the concentration of 5-10 mg/mL, carrying out sample injection measurement, and calculating according to a standard curve to obtain the weight average molecular weight Mw, wherein the weight average molecular weight Mw is regarded as the average molecular weight, and the average polymerization degree of the glycolic acid oligomer is an integer with the (Mw-18)/58 rounded downwards.
The method for measuring the moisture content by using the coulomb method moisture meter comprises the following steps:
Methanol, formamide and Karl Fischer reagent are added into a titration chamber of a coulometric moisture meter after being configured according to the volume ratio of 1:1:3, and a baseline is waited to be stable; accurately weighing 0.5 g of glycolide powder, putting the glycolide powder into a closed titration chamber, starting to titrate moisture after 300 seconds of dissolution, calculating the moisture mass by a moisture meter after the titration is finished, and dividing the mass by the mass of the glycolide powder to obtain the moisture content.
GC measurement of residual solvent content:
Preparing a series of dimethyl sulfoxide containing 10-1000 ppm of solvent, and sequentially carrying out sample injection test to obtain a standard curve of the solvent content and the peak area; accurately weighing 0.5 g of glycolide powder and 2 ml of dimethyl sulfoxide, preparing a solution after dissolving, carrying out sample injection test, and calculating the content of residual solvent according to the peak area of the solvent and a standard curve.
Method for measuring intrinsic viscosity of polyglycolic acid:
the solution with concentration c is prepared by taking hexafluoroisopropanol as a solvent, and the intrinsic viscosity [ eta ] is obtained by measuring the flowing-out time t 0 and t of the pure solvent and the sample solution in a constant-temperature water bath at 25 ℃ by using an Ubbelohde viscometer, and the formula [ eta ] =2sqrt [ t/t 0-1-ln(t/t0) ]/c.
[ Example 1]
Preparation of glycolide crude product:
600g of glycolic acid crystals (commercial product, GC purity 99.0%, total aldehyde content of MBTH method 56 ppm) and 6g of stannous octoate catalyst are added into a reactor, the temperature is raised to 90 ℃ from room temperature, after the solid is completely dissolved, the temperature is raised to 120 ℃ to start normal pressure prepolymerization, the temperature is raised to 210 ℃ after the prepolymerization is carried out for 2 hours, after anhydrous distillation, the system is kept at the temperature and vacuumizing is started, the vacuum degree is controlled at 2kPa, the polycondensation time is 3 hours, 475g of glycolic acid polycondensate is obtained after anhydrous distillation, and the weight average molecular weight of the polycondensate is 21000Da.
The oligomer is provided to a depolymerization reactor, the depolymerization system is reacted at the reaction temperature of 285 ℃, the vacuum degree of 3kPa and the stirring speed of 120rpm to prepare crude glycolide, the gas phase crude glycolide is collected after being condensed by a hot water medium at 90 ℃, the temperature is kept at 90 ℃ for heat preservation, the reaction is stopped after 3 hours, 392g of crude glycolide is obtained, the acid content of 480 mu mol/g, and the glycolic acid oligomer content in the crude glycolide is 3300ppm.
Purification of glycolide crude product:
250g of the crude glycolide melt is kept at the temperature of 90 ℃ in a jacketed reaction kettle A, 500g of isopropanol is added in advance in a jacketed reaction kettle B, 120rmp is stirred, and the temperature is kept at 25 ℃. The melt in reactor A was fed to reactor B at a rate of 10ml/min with stirring at 120rmp, and after completion 210g of filter cake was collected by suction filtration under nitrogen protection.
The filter cake was mixed with 420g of isopropanol and heated to 85℃to form a liquid which was maintained for 0.5h. Cooling to room temperature at a speed of 120rpm, sufficiently precipitating glycolide from the system, performing suction filtration, repeating the cooling recrystallization-filtration operation of the filter cake for 1 time, and vacuum drying the filtered solid at 50 ℃ for 4 hours to obtain 164.0g of white crystals with a total yield of 65.6%. The acid content in the purified glycolide is 1.6 mu mol/g measured by acid-base titration; the residual glycolic acid oligomer content in the glycolide after purification was found to be 4500ppm by extraction with ethyl acetate; the average degree of polymerization of the residual oligomer was 18 as measured using APC; the water content was 182ppm using a coulomb method moisture meter; the residual isopropanol content was determined to be 315ppm using GC.
Preparation of polyglycolic acid:
55g of purified glycolide is weighed and added into a reaction kettle, stannous chloride dihydrate powder (commercially available) accounting for 0.002 percent of the weight of the glycolide is weighed, the reaction kettle is vacuumized, then replaced by nitrogen, the vacuumization-nitrogen replacement operation is repeated for one time, finally, the vacuum is pumped again to enable the pressure inside the reaction kettle to be lower than 200Pa, then the reaction kettle is closed for stirring reaction, firstly, the temperature of the reaction kettle is heated to 160 ℃, then the temperature is raised at the heating rate of 4 ℃/min, finally, the temperature is kept at 220 ℃, and the polyglycolic acid is obtained after the reaction is carried out for 60 min.
The intrinsic viscosity of polyglycolic acid was found to be 1.45dl/g.
[ Example 2]
Preparation of glycolide crude product: as in example 1;
purification of glycolide crude product:
The difference between this example and example 1 is that the melt in reactor A was fed into reactor B at a rate of 10ml/min, and that reactor B was incubated at 38℃with the other examples 1. 162.2 g of white crystals were obtained, and the total yield was 64.9%. The acid content in the purified glycolide is 1.2 mu mol/g measured by acid-base titration; the residual glycolic acid oligomer content in the glycolide after purification was measured using ethyl acetate extraction to be 5200ppm; the average degree of polymerization of the residual oligomer was 20 as measured using APC; moisture 163ppm was measured using a coulomb method moisture meter; the residual isopropanol content was measured using GC and found to be 305ppm.
Preparation of polyglycolic acid: as in example 1, polyglycolic acid was found to have an intrinsic viscosity of 1.43dl/g.
[ Example 3]
Preparation of glycolide crude product: as in example 1;
purification of glycolide crude product:
the difference from example 1 is that ethanol is used instead of isopropanol, otherwise the same as example 1. 160.3 g of white crystals were obtained, and the total yield was 64.1%. The acid content in the purified glycolide is 2.7 mu mol/g measured by acid-base titration; the residual glycolic acid oligomer content in the glycolide after purification was 5400ppm as measured by ethyl acetate extraction; the average degree of polymerization of the residual oligomer was 16 as measured using APC; the water content was measured at 230ppm using a coulomb method moisture meter; the residual ethanol content was measured using GC at 260ppm.
Preparation of polyglycolic acid: as in example 1, polyglycolic acid was found to have an intrinsic viscosity of 1.57dl/g.
[ Example 4]
Preparation of glycolide crude product: as in example 1;
purification of glycolide crude product:
The difference from example 1 is that a mixed solvent of ethanol and n-propanol (mass ratio 1 to 1) was used instead of isopropanol, and the other is the same as example 1. 160.0 g of white crystals were obtained, and the total yield was 64.1%. The acid content in the purified glycolide is 2.4 mu mol/g measured by acid-base titration; the residual glycolic acid oligomer content in the glycolide after purification was 5500ppm as measured by ethyl acetate extraction; the average degree of polymerization of the residual oligomer was 17 as measured using APC; measuring 218ppm of moisture by using a coulomb method moisture meter; residual ethanol and residual n-propanol contents were 135ppm and 145ppm, respectively, as measured using GC.
Preparation of polyglycolic acid: as in example 1, polyglycolic acid was found to have an intrinsic viscosity of 1.50dl/g.
[ Example 5]
Preparation of glycolide crude product: as in example 1;
purification of glycolide crude product:
The difference between this example and example 1 is that after 210g of filter cake has been collected by suction filtration, the filter cake is heated to 77℃with 420g of isopropanol in a mixture. 165.0 g of white crystals were obtained, and the total yield was 66.0%. The acid content in the purified glycolide is 2.8 mu mol/g measured by acid-base titration; the residual glycolic acid oligomer content in the glycolide after purification was 4400ppm as measured by ethyl acetate extraction; the average degree of polymerization of the residual oligomer was 16 as measured using APC; moisture 206ppm was measured using a coulomb method moisture meter; the residual isopropanol content was measured by GC and found to be 340ppm.
Preparation of polyglycolic acid: as in example 1, polyglycolic acid was found to have an intrinsic viscosity of 1.43dl/g.
[ Example 6]
Preparation of glycolide crude product: as in example 1;
purification of glycolide crude product:
The difference from example 1 is that the filter cake is heated to 85℃in combination with 420g of isopropanol and held for 2.5h, otherwise as in example 1. 161.8 g of white crystals were obtained, and the total yield was 64.7%. The acid content in the purified glycolide is 1.1 mu mol/g measured by acid-base titration; the residual glycolic acid oligomer content in the glycolide after purification was 6600ppm as measured by ethyl acetate extraction; the average degree of polymerization of the residual oligomer was 16 as measured using APC; the water content was measured at 224ppm using a coulomb method moisture meter; the residual isopropanol content was determined to be 335ppm using GC.
Preparation of polyglycolic acid: as in example 1, polyglycolic acid was found to have an intrinsic viscosity of 1.50dl/g.
[ Example 7]
Preparation of glycolide crude product: as in example 1;
purification of glycolide crude product:
The difference from example 1 is that 250g of crude glycolide melt is incubated in jacketed reaction vessel A at 90℃for 2 hours and then transferred to reaction vessel B, with the exception of example 1. 159.0 g of white crystals were obtained, and the total yield was 63.6%. The acid content in the purified glycolide is 1.5 mu mol/g measured by acid-base titration; residual glycolic acid oligomer content in glycolide after purification was 9300ppm as measured by ethyl acetate extraction; the average degree of polymerization of the residual oligomer was 35 as measured using APC; the water content was measured at 250ppm using a coulomb method moisture meter; the residual isopropanol content was measured using GC to be 405ppm.
Preparation of polyglycolic acid: as in example 1, polyglycolic acid was found to have an intrinsic viscosity of 1.45dl/g.
[ Example 8]
Preparation of glycolide crude product: the difference from example 1 is that the gas phase crude glycolide is collected after rectification by a packed column filled with a dixon packing (one eighth inch) and then condensed by a hot water medium at 90 ℃; 324g of crude glycolide was obtained, which had an acid content of 353. Mu. Mol/g and a glycolic acid oligomer content of 370ppm.
Purification of glycolide crude product:
as in example 1, 166.0 g of white crystals were obtained, and the total yield was 66.4%. The acid content in the purified glycolide is 0.8 mu mol/g measured by acid-base titration; the residual glycolic acid oligomer content in the glycolide after purification was 1300ppm as measured by ethyl acetate extraction; the average degree of polymerization of the residual oligomer was 14 as measured using APC; moisture 211ppm was measured using a coulomb method moisture meter; the residual isopropanol content was found to be 345ppm using GC.
Preparation of polyglycolic acid: as in example 1, polyglycolic acid was found to have an intrinsic viscosity of 1.40dl/g.
[ Example 9]
Preparation of glycolide crude product: as in example 1;
Purification of glycolide crude product: the difference from example 1 is that the amount of isopropanol used is doubled, otherwise the same as in example 1; 155.0 g of white crystals were obtained, and the total yield was 62.0%. The acid content in the purified glycolide is 1.0 mu mol/g measured by acid-base titration; the residual glycolic acid oligomer content in the glycolide after purification was 4200ppm as measured by extraction with ethyl acetate; the average degree of polymerization of the residual oligomer was 24 as measured using APC; moisture 265ppm was measured using a coulomb method moisture meter; the residual isopropanol content was 460ppm as measured using GC.
Preparation of polyglycolic acid: as in example 1, polyglycolic acid was found to have an intrinsic viscosity of 1.47dl/g.
[ Example 10]
Preparation of glycolide crude product:
600g of methyl glycolate (commercially available, GC purity 98.0%) and 16g of stannous octoate catalyst were added to the reactor, the pressure was controlled at 0.22-0.55 MPa, the temperature was gradually increased from 150℃to 220℃over 3 hours, the positive pressure prepolymerization was carried out, after no methanol was distilled off, the system was kept at 220℃and the pressure was initially reduced, the pressure was gradually reduced to 3kPa absolute pressure over 3 hours, after no methanol was distilled off, 406.6g of methyl glycolate polycondensate was obtained, and the weight average molecular weight of the polycondensate was 12000Da.
The oligomer is provided to a depolymerization reactor, the depolymerization system is reacted at a reaction temperature of 285 ℃, a vacuum degree of 3kPa and a stirring speed of 120rpm to prepare crude glycolide, the gas-phase crude glycolide is collected after being condensed by a hot water medium at 90 ℃, the temperature is kept at 90 ℃ for heat preservation, the reaction is stopped after 3 hours, 366g of crude glycolide is obtained, the acid content of 379 mu mol/g, and the glycolic acid oligomer content in the crude glycolide is 2900ppm.
Purification of glycolide crude product:
As in example 1, 173.2g of white crystals were obtained, and the total yield was 69.3%. The acid content in the purified glycolide is 1.1 mu mol/g measured by acid-base titration; the residual glycolic acid oligomer content in the glycolide after purification was 3900ppm as measured by ethyl acetate extraction; the average degree of polymerization of the residual oligomer was 23 as measured using APC; the water content was measured at 262ppm by using a coulomb method moisture meter; the residual isopropanol content was 435ppm using GC.
Preparation of polyglycolic acid: as in example 1, polyglycolic acid was found to have an intrinsic viscosity of 1.51dl/g.
[ Example 11]
Preparation of glycolide crude product:
The difference from example 1 is that: the pyrolysis temperature of the depolymerization system is 230 ℃, the pyrolysis pressure is 5kPa, gas-phase crude glycolide is collected after being condensed by a hot water medium at 80 ℃, the temperature is kept at 80 ℃ for heat preservation, the reaction is stopped after 3 hours of reaction, and other conditions are the same as those of the example 1; 304g of crude glycolide with an acid content of 435 mu mol/g and 1900ppm of glycolic acid oligomer in the crude glycolide are obtained;
purification of glycolide crude product:
The difference from example 1 is that: the crude glycolide melt was incubated in jacketed kettle A at 80℃with the same procedure as in example 1. 169.0 g of white crystals were obtained, giving a total yield of 67.6%. The acid content in the purified glycolide is 1.5 mu mol/g measured by acid-base titration; the residual glycolic acid oligomer content in the glycolide after purification was 3100ppm as measured using ethyl acetate extraction; the average degree of polymerization of the residual oligomer was 21 as measured using APC; moisture 195ppm was measured using a coulomb method moisture meter; the residual isopropanol content was measured using GC to be 230ppm;
Preparation of polyglycolic acid: as in example 1, polyglycolic acid was found to have an intrinsic viscosity of 1.49dl/g.
[ Example 12]
Preparation of glycolide crude product: as in example 1;
purification of glycolide crude product:
The difference from example 1 is that: the cooling recrystallization-filtration operation was performed only 1 time, and the same as in example 1 was repeated. 182.5 g of white crystals were obtained, and the total yield was 73.0%. The acid content in the purified glycolide is 6.5 mu mol/g measured by acid-base titration; the residual glycolic acid oligomer content in the glycolide after purification was 3900ppm as measured by ethyl acetate extraction; the average degree of polymerization of the residual oligomer was 15 as measured using APC; moisture 283ppm was measured using a coulomb method moisture meter; residual isopropanol content was 310ppm as measured using GC;
Preparation of polyglycolic acid: as in example 1, polyglycolic acid was found to have an intrinsic viscosity of 1.35dl/g.
[ Example 13]
Preparation of glycolic acid oligomer:
The glycolic acid polycondensate was prepared as in example 1 except that the degree of vacuum (absolute pressure) was controlled at 5kPa and the polycondensation time was 15 minutes at the time of evacuation, otherwise as in example 1; taking polycondensates as raw materials, and extracting dry sediment according to the method for measuring the content of glycolic acid oligomer in crude glycolide and glycolide, namely the glycolic acid oligomer; the average degree of polymerization of the dried deposit was measured using APC and found to be 20.
Preparation of glycolide composition:
adding the glycolic acid oligomer extracted from the glycolic acid polycondensate obtained above to commercial glycolide to obtain a glycolide composition containing the glycolic acid oligomer;
To commercially available glycolide (acid value 1.6. Mu. Mol/g, residual glycolic acid oligomer content 50ppm, average degree of polymerization of residual oligomer 5, residual ethyl acetate content 360ppm, moisture 210 ppm) was added 5000ppm of the above glycolic acid oligomer.
Preparation of polyglycolic acid: the difference from example 1 is that 55g of glycolide composition was weighed into a reaction vessel, and the other is the same as example 1; the intrinsic viscosity of polyglycolic acid was found to be 1.39dl/g.
[ Example 14 ]
Preparation of glycolic acid oligomer:
The same procedure as in example 10 was used for the preparation of the methyl glycolate polycondensate: the depressurization operation was varied and gradually decreased to 10kPa absolute pressure within 20 minutes, otherwise as in example 1; taking polycondensates as raw materials, and extracting dry sediment according to the method for measuring the content of glycolic acid oligomer in crude glycolide and glycolide, namely the glycolic acid oligomer; the average degree of polymerization of the dried deposit was measured using APC and found to be 25.
Preparation of glycolide composition:
adding the glycolic acid oligomer extracted from the glycolic acid polycondensate obtained above to commercial glycolide to obtain a glycolide composition containing the glycolic acid oligomer;
To commercially available glycolide (acid value 1.6. Mu. Mol/g, residual glycolic acid oligomer content 50ppm, average degree of polymerization of residual oligomer 5, residual ethyl acetate content 360ppm, moisture 210 ppm) was added 8000ppm of the above glycolic acid oligomer.
Preparation of polyglycolic acid: the difference from example 1 is that 55g of glycolide composition was weighed into a reaction vessel, and the other is the same as example 1; the intrinsic viscosity of polyglycolic acid was found to be 1.36dl/g.
[ Example 15 ]
The glycolide after purification of example 1 was extracted as a dry deposit according to the above-mentioned "determination method of the content of glycolic acid oligomer in crude glycolide and glycolide", namely glycolic acid oligomer.
Preparation of glycolide composition:
adding the glycolic acid oligomer extracted from the glycolic acid polycondensate obtained above to commercial glycolide to obtain a glycolide composition containing the glycolic acid oligomer;
To commercially available glycolide (acid value 1.6. Mu. Mol/g, residual glycolic acid oligomer content 50ppm, average degree of polymerization of residual oligomer 5, residual ethyl acetate content 360ppm, moisture 210 ppm) was added 2000ppm of the above glycolic acid oligomer.
Preparation of polyglycolic acid: the difference from example 1 is that 55g of glycolide composition was weighed into a reaction vessel; the intrinsic viscosity of polyglycolic acid was found to be 1.39dl/g.
[ Example 16]
Preparation of glycolide composition: same as in example 13;
purification of glycolide composition:
250g of the melt of the glycolide composition prepared in example 13 was kept at 90℃in a jacketed reaction vessel A, 500g of a composite solvent of isopropanol and ethylene glycol dimethyl ether (isopropanol: 50% by weight) was previously added to the jacketed reaction vessel B, and 120rmp was stirred and kept at 25 ℃. The melt in the reaction vessel A was fed into the reaction vessel B at a rate of 10ml/min, during which the stirring rate was 120rmp, and after completion, the filter cake was collected by suction filtration under nitrogen protection. The filter cake was dried under vacuum at 50℃for 4h to give 230.0g of white crystals in 92.0% yield. The acid content in the purified glycolide is 0.4 mu mol/g measured by acid-base titration; the residual glycolic acid oligomer content in the glycolide after purification was 4900ppm as measured by ethyl acetate extraction; the average degree of polymerization of the residual oligomer was 17 as measured using APC; moisture 195ppm was measured using a coulomb method moisture meter; the residual isopropanol and residual ethylene glycol dimethyl ether content were measured by GC and were 150ppm and 135ppm, respectively.
Comparative example 1
Preparation of glycolic acid oligomer: the same glycolic acid polycondensate as in example 1 was prepared except that the polycondensation time was 0 minutes at the time of evacuation, i.e., only the polycondensation was carried out at normal pressure for 2 hours, otherwise as in example 1; taking polycondensates as raw materials, and extracting dry sediment according to the method for measuring the content of glycolic acid oligomer in crude glycolide and glycolide, namely the glycolic acid oligomer; the average degree of polymerization of the dried deposit was measured using APC and was 5.
Preparation of glycolide composition: to commercially available glycolide (acid value 1.6. Mu. Mol/g, residual glycolic acid oligomer content 50ppm, average degree of polymerization of residual oligomer 5, residual ethyl acetate content 360 ppm) was added 5000ppm of the above glycolic acid oligomer.
Preparation of polyglycolic acid: the difference from example 1 is that 55g of glycolide composition was weighed into a reaction vessel, and the other is the same as example 1; the intrinsic viscosity of polyglycolic acid was found to be 1.32dl/g.
Comparative example 2
Preparation of polyglycolic acid: adding an initiator lauryl alcohol (commercially available) which is equal to 5000ppm of glycolide in mass fraction into a reaction kettle (acid value is 1.6 mu mol/g, residual glycolic acid oligomer content is 50ppm, average polymerization degree of residual oligomer is 5, residual ethyl acetate content is 360 ppm), vacuumizing the reaction kettle, replacing with nitrogen, repeating vacuumizing-nitrogen replacement operation for one time, vacuumizing again to enable the pressure inside the reaction kettle to be lower than 200Pa, closing the reaction kettle to perform stirring reaction, heating the reaction kettle to 160 ℃ at a heating rate of 4 ℃/min, keeping the temperature at 220 ℃, and discharging after reacting for 60min to obtain polyglycolic acid; the intrinsic viscosity of polyglycolic acid was found to be 1.25dl/g.
The glycolide compositions prepared in examples 1 to 11 have a low carboxyl end group content of 0.8 to 2.8. Mu. Mol/g;
The glycolide compositions prepared in examples 1 to 11 retain impurities with a relatively high degree of polymerization, the degree of polymerization of the impurities is 14 to 35, and the intrinsic viscosity after polymerization is 1.43 to 1.57dl/g when the glycolide compositions are used for preparing polyglycolic acid by ring-opening polymerization; lauryl alcohol added in comparative example 2 is a common initiator, and the equivalent amount of glycolic acid oligomer as an initiator produced polyglycolic acid with higher intrinsic viscosity than that produced by polymerization in example 1.
The intrinsic viscosities after polymerization of comparative examples 1 to 2 were 1.32dl/g and 1.25dl/g, respectively, and the intrinsic viscosities of example 1 were higher, compared with the intrinsic viscosities after polymerization of example 1 of 1.45dl/g, demonstrating that the glycolide composition prepared by the present invention can be used as a macroinitiator in ring-opening polymerization, does not affect the ring-opening polymerization reaction, and promotes polyglycolic acid produced after polymerization to have higher intrinsic viscosities.
The solvent extraction capacity is stronger, the extraction temperature is lower, the glycolide thermal degradation is not caused, and the test result shows that the content of the glycolic acid oligomer with higher polymerization degree in the examples 1-12 is 0.13-0.93%, and can be accurately controlled within 1%.
Examples 13 to 15 the glycolide composition obtained was extracted from the glycolic acid oligomer, added to commercial glycolide, and when used for the preparation of polyglycolic acid by ring-opening polymerization, the mass fraction was 0.2 to 0.8%, and the intrinsic viscosity after polymerization was 1.36 to 1.39dl/g, providing a process for the preparation of glycolide compositions, i.e., the glycolide composition was obtained by adding the glycolic acid oligomer to glycolide, and further used for the preparation of downstream products of polyglycolic acid.
In example 16, a complex solvent was used, which demonstrated that the solvent only removed the lower polymerization degree of the glycolide as an impurity, and the higher polymerization degree oligomers prepared according to the present invention remained in the glycolide after extraction to form a glycolide composition.
Claims (16)
1. A glycolide composition comprising, based on the weight of the composition, 99% by weight or more glycolide and not more than 1% by weight of a glycolic acid oligomer; the average degree of polymerization of the glycolic acid oligomer is 8 or more.
2. Glycolide composition according to claim 1, characterized in that:
Comprises from 99.0% to 99.9% by weight of glycolide and from 0.1% to 1% by weight of glycolic acid oligomer, based on the weight of the composition.
3. Glycolide composition according to claim 1, characterized in that:
The average polymerization degree of the glycolic acid oligomer is more than or equal to 14.
4. A glycolide composition according to any one of claims 1 to 3, characterized in that:
the carboxyl end group content of the glycolide composition is less than or equal to 7 mu mol/g; preferably, the carboxyl end group content thereof is 3. Mu. Mol/g or less.
5. A process for preparing a glycolide composition according to any one of claims 1 to 4, comprising the steps of:
(1) Glycolic acid polycondensate is prepared by polycondensation reaction of glycolic acid, or glycolic acid derivative polycondensate is prepared by transesterification reaction of glycolic acid derivative;
(2) Carrying out pyrolysis reaction on the obtained glycolic acid polycondensate or glycolic acid derivative polycondensate, and condensing a gas phase to obtain a glycolide crude product;
(3) And purifying the obtained crude glycolide product to obtain the glycolide composition.
6. The method for producing a glycolide composition according to claim 5, wherein:
step (1),
The glycollic acid is at least one of glycollic acid crystals and glycollic acid aqueous solution;
The glycollic acid derivative is methyl glycollate;
Preferably, the method comprises the steps of,
The glycolic acid crystals are glycolic acid having a purity of greater than 97 wt.% and containing no more than 2000ppm aldehyde; and/or the number of the groups of groups,
The aqueous solution of glycolic acid has a mass concentration of 50% or more and contains not more than 2000ppm of aldehyde based on the mass of glycolic acid; and/or the number of the groups of groups,
The methyl glycolate is methyl glycolate with purity higher than 95 weight percent and contains no more than 1 weight percent of alcohol, acid and other esters respectively; and/or the number of the groups of groups,
The weight average molecular weight of the glycolic acid polycondensate or glycolic acid derivative polycondensate is less than or equal to 5 ten thousand; preferably 2.5 ten thousand or less.
7. The method for producing a glycolide composition according to claim 5, wherein:
step (1),
The polycondensation step includes the steps of first performing normal-pressure polycondensation and then performing reduced-pressure polycondensation on the raw materials, and preferably includes the following steps:
a) The polycondensation time at the normal pressure stage is within 4 hours, the polycondensation temperature is 110-220 ℃, and the polycondensation pressure is 0.09-0.11 MPa;
b) The polycondensation time in the decompression stage is within 4 hours, the polycondensation temperature is 110-220 ℃, the polycondensation pressure is 0.1-10 kPa, until no water is distilled out, and the glycolic acid polycondensate is obtained;
the transesterification step includes the steps of subjecting the raw material to positive pressure polycondensation followed by reduced pressure polycondensation, preferably comprising the steps of:
a) The polycondensation time in the positive pressure stage is within 4 hours, the polycondensation temperature is 150-230 ℃, and the polycondensation pressure is 0.11-0.55 MPa;
b) The polycondensation time in the decompression stage is within 4 hours, the polycondensation temperature is 150-230 ℃, the polycondensation pressure is 0.1-10 kPa, and the methyl glycolate polycondensate is obtained until no methanol is distilled out.
8. A process for the preparation of glycolide compositions according to claim 1, characterized in that:
Step (2),
The gas phase product in the pyrolysis reaction is distilled out of the reaction system in a straight-run mode or is distilled out of the reaction system through a rectifying tower;
The pyrolysis pressure is 0.1 to 10kPa; preferably 3 to 5kPa;
The pyrolysis temperature is 230-290 ℃;
the temperature of the molten glycolide is 75-110 ℃; preferably 80 to 95 ℃;
The time before entering step (3) after the gas phase has condensed to the molten state is not more than 4 hours, preferably not more than 2 hours;
The crude glycolide product comprises no more than 2% by weight of glycolic acid oligomers.
9. A process for the preparation of glycolide compositions according to claim 1, characterized in that:
The step (3) specifically comprises the steps of,
(3-1) Subjecting the crude glycolide product to impurity extraction with a solvent to obtain a glycolide-containing phase and an impurity-containing phase; the solvent is a solvent of saturated monohydric alcohol or a composite solvent of saturated monohydric alcohol and other solvents; the extraction temperature is 20-40 ℃;
(3-2) melting the glycolide-containing phase obtained, crystallizing, and extracting a solid phase;
preferably, the steps (3-1) and (3-2) are repeated 1 to 2 times.
10. A process for the preparation of glycolide compositions according to claim 9, characterized in that:
Step (3-2),
The method for extracting the solid phase is filtration or drying; and/or the number of the groups of groups,
The melting temperature of the glycolide-containing phase is 75-150 ℃; preferably 75-90 ℃;
The glycolide has a residence time in the molten state of no more than 2.5 hours.
11. A process for the preparation of glycolide compositions according to claim 9, characterized in that:
the solvent of the saturated monohydric alcohol is saturated monohydric alcohol with 1-6 carbon atoms; preferably a saturated monohydric alcohol having 1 to 5 carbon atoms; more preferably at least one of methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol, and isobutanol; and/or the number of the groups of groups,
The other solvent is a solvent with the solubility of glycolide in the solvent being more than or equal to 10g of glycolide per hundred g of solvent at 25 ℃, and the other solvent is preferably at least one of ethyl acetate, acetone, ethylene glycol dimethyl ether and polyalcohol ether; and/or the number of the groups of groups,
The mass ratio of the solvent to the glycolide crude product is (1-10): 1, preferably (2 to 4): 1.
12. A glycolide composition obtainable by a process according to any one of claims 5 to 11, said glycolide composition comprising 99% by weight or more of glycolide and not more than 1% by weight of glycolic acid oligomer; preferably comprises from 99.0% to 99.9% by weight glycolide and from 0.1% to 1% by weight glycolic acid oligomer; the average degree of polymerization of the glycolic acid oligomer is 8 or more; preferably 14 or more.
13. Glycolide composition according to claim 12, characterized in that:
The glycolide composition further comprises water or a saturated monohydric alcohol; the content of water in the glycolide composition is less than or equal to 300ppm; the content of the saturated monohydric alcohol is less than or equal to 500ppm, and the melting point of the saturated monohydric alcohol is less than or equal to 25 ℃.
14. A glycolic acid oligomer prepared from the glycolide composition of claim 12 or 13, said glycolide composition being isolated to provide said glycolic acid oligomer; preferably, the glycolic acid oligomer is obtained by dissolving the glycolic acid oligomer in a solvent to prepare a solution, centrifuging the solution, and drying insoluble sediment.
15. A glycolide composition comprising the glycolic acid oligomer of claim 14, further comprising glycolide, comprising 99% by weight or more glycolide and not greater than 1% by weight of glycolic acid oligomer, based on the weight of the composition; preferably, it comprises from 99.0% to 99.9% by weight of glycolide and from 0.1% to 1% by weight of glycolic acid oligomer.
16. Polyglycolic acid prepared from the glycolide composition of any one of claims 1 to 4, or claim 12.
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