CN115505107A - Preparation method of granular polyglycolic acid - Google Patents
Preparation method of granular polyglycolic acid Download PDFInfo
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- CN115505107A CN115505107A CN202110693030.5A CN202110693030A CN115505107A CN 115505107 A CN115505107 A CN 115505107A CN 202110693030 A CN202110693030 A CN 202110693030A CN 115505107 A CN115505107 A CN 115505107A
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- polyglycolic acid
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- 229920000954 Polyglycolide Polymers 0.000 title claims abstract description 53
- 239000004633 polyglycolic acid Substances 0.000 title claims abstract description 50
- 238000002360 preparation method Methods 0.000 title claims abstract description 7
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- 230000003068 static effect Effects 0.000 claims abstract description 42
- 238000000034 method Methods 0.000 claims abstract description 40
- 238000006243 chemical reaction Methods 0.000 claims abstract description 37
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- 238000006116 polymerization reaction Methods 0.000 claims abstract description 16
- 238000002156 mixing Methods 0.000 claims description 20
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- 238000005469 granulation Methods 0.000 claims description 8
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- TXUICONDJPYNPY-UHFFFAOYSA-N (1,10,13-trimethyl-3-oxo-4,5,6,7,8,9,11,12,14,15,16,17-dodecahydrocyclopenta[a]phenanthren-17-yl) heptanoate Chemical compound C1CC2CC(=O)C=C(C)C2(C)C2C1C1CCC(OC(=O)CCCCCC)C1(C)CC2 TXUICONDJPYNPY-UHFFFAOYSA-N 0.000 description 1
- SKEZDZQGPKHHSH-UHFFFAOYSA-J 2-hydroxypropanoate;tin(4+) Chemical compound [Sn+4].CC(O)C([O-])=O.CC(O)C([O-])=O.CC(O)C([O-])=O.CC(O)C([O-])=O SKEZDZQGPKHHSH-UHFFFAOYSA-J 0.000 description 1
- QOSSAOTZNIDXMA-UHFFFAOYSA-N Dicylcohexylcarbodiimide Chemical compound C1CCCCC1N=C=NC1CCCCC1 QOSSAOTZNIDXMA-UHFFFAOYSA-N 0.000 description 1
- XBDQKXXYIPTUBI-UHFFFAOYSA-M Propionate Chemical compound CCC([O-])=O XBDQKXXYIPTUBI-UHFFFAOYSA-M 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- 229910021626 Tin(II) chloride Inorganic materials 0.000 description 1
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- BGYHLZZASRKEJE-UHFFFAOYSA-N [3-[3-(3,5-ditert-butyl-4-hydroxyphenyl)propanoyloxy]-2,2-bis[3-(3,5-ditert-butyl-4-hydroxyphenyl)propanoyloxymethyl]propyl] 3-(3,5-ditert-butyl-4-hydroxyphenyl)propanoate Chemical compound CC(C)(C)C1=C(O)C(C(C)(C)C)=CC(CCC(=O)OCC(COC(=O)CCC=2C=C(C(O)=C(C=2)C(C)(C)C)C(C)(C)C)(COC(=O)CCC=2C=C(C(O)=C(C=2)C(C)(C)C)C(C)(C)C)COC(=O)CCC=2C=C(C(O)=C(C=2)C(C)(C)C)C(C)(C)C)=C1 BGYHLZZASRKEJE-UHFFFAOYSA-N 0.000 description 1
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- CJZGTCYPCWQAJB-UHFFFAOYSA-L calcium stearate Chemical compound [Ca+2].CCCCCCCCCCCCCCCCCC([O-])=O.CCCCCCCCCCCCCCCCCC([O-])=O CJZGTCYPCWQAJB-UHFFFAOYSA-L 0.000 description 1
- 235000013539 calcium stearate Nutrition 0.000 description 1
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- HQWPLXHWEZZGKY-UHFFFAOYSA-N diethylzinc Chemical compound CC[Zn]CC HQWPLXHWEZZGKY-UHFFFAOYSA-N 0.000 description 1
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- XLDBGFGREOMWSL-UHFFFAOYSA-N n,n'-bis[2,6-di(propan-2-yl)phenyl]methanediimine Chemical group CC(C)C1=CC=CC(C(C)C)=C1N=C=NC1=C(C(C)C)C=CC=C1C(C)C XLDBGFGREOMWSL-UHFFFAOYSA-N 0.000 description 1
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- WVDDGKGOMKODPV-ZQBYOMGUSA-N phenyl(114C)methanol Chemical compound O[14CH2]C1=CC=CC=C1 WVDDGKGOMKODPV-ZQBYOMGUSA-N 0.000 description 1
- 229920003229 poly(methyl methacrylate) Polymers 0.000 description 1
- 239000004926 polymethyl methacrylate Substances 0.000 description 1
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 1
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- 150000003138 primary alcohols Chemical class 0.000 description 1
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- 150000003333 secondary alcohols Chemical class 0.000 description 1
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- 239000001119 stannous chloride Substances 0.000 description 1
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- 238000009864 tensile test Methods 0.000 description 1
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- KSBAEPSJVUENNK-UHFFFAOYSA-L tin(ii) 2-ethylhexanoate Chemical compound [Sn+2].CCCCC(CC)C([O-])=O.CCCCC(CC)C([O-])=O KSBAEPSJVUENNK-UHFFFAOYSA-L 0.000 description 1
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- YZYKBQUWMPUVEN-UHFFFAOYSA-N zafuleptine Chemical compound OC(=O)CCCCCC(C(C)C)NCC1=CC=C(F)C=C1 YZYKBQUWMPUVEN-UHFFFAOYSA-N 0.000 description 1
- 239000011701 zinc Substances 0.000 description 1
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- 229940012185 zinc palmitate Drugs 0.000 description 1
- GJAPSKMAVXDBIU-UHFFFAOYSA-L zinc;hexadecanoate Chemical compound [Zn+2].CCCCCCCCCCCCCCCC([O-])=O.CCCCCCCCCCCCCCCC([O-])=O GJAPSKMAVXDBIU-UHFFFAOYSA-L 0.000 description 1
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
- C08G63/08—Lactones or lactides
-
- 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
Abstract
The invention discloses a preparation method of granular polyglycolic acid. The method comprises the following steps: (1) Prepolymerizing molten glycolide and a reaction auxiliary in a static mixer to obtain a glycolic acid prepolymer; (2) Carrying out final polymerization on the glycolic acid prepolymer obtained in the step (1) and a chain extender through tackifying equipment to obtain a molten product; and (3) extruding and granulating the molten product obtained in the step (2), and cooling to obtain granular polyglycolic acid.
Description
Technical Field
The invention relates to the field of polymer preparation, in particular to a preparation method of granular polyglycolic acid.
Background
Polyglycolic acid, also known as polyglycolic acid (abbreviated as PGA), is a biodegradable aliphatic polymer and has good biocompatibility, gas barrier property and strong mechanical strength.
At present, a process for producing particulate polyglycolic acid generally includes steps of melting, drawing, cooling, solidifying, granulating and the like, but since the molecular configuration of polyglycolic acid is a simple linear long-chain macromolecular structure, when a melt-extruded polyglycolic acid strand is cooled with an aqueous medium in the production process of the particulate polyglycolic acid, although the cooling efficiency is high, the polyglycolic acid itself is hydrolyzed relatively severely under the stimulation of water, so that the molecular weight of the finally obtained particulate polyglycolic acid is reduced and the molecular weight distribution is broadened.
Therefore, there is a strong need in the art to provide a process for producing particulate polyglycolic acid which can effectively maintain a narrow molecular weight and molecular weight distribution.
Disclosure of Invention
The present invention aims to provide a process for producing particulate polyglycolic acid.
The present invention provides a process for the preparation of particulate polyglycolic acid, the process comprising the steps of:
(1) Prepolymerizing molten glycolide and a reaction auxiliary in a static mixer to obtain a glycolic acid prepolymer;
(2) Carrying out final polymerization on the glycolic acid prepolymer obtained in the step (1) and a chain extender through tackifying equipment to obtain a molten product; and
(3) And (3) extruding and granulating the molten product obtained in the step (2), and cooling to obtain granular polyglycolic acid.
In another embodiment, the static mixer used in step (1) employs at least 2 stages of gradient temperature ramp.
In another embodiment, the static mixer used in step (1) is a 2-10 stage gradient temperature increasing system, preferably 3-7 stages.
In another embodiment, the first stage temperature ranges from 120 ℃ to 220 ℃; the temperature of the last stage is 220-250 ℃.
In another embodiment, the temperature of the second section is increased by between 10-100 ℃ over the temperature of the first section; the temperature of the last section is increased by 0-30 ℃ compared with the temperature of the previous adjacent section.
In another embodiment, the glycolic acid prepolymer obtained in step (1) has a weight average molecular weight of about 5 to 15 ten thousand.
In another embodiment, the reaction auxiliary in step (1) comprises a catalyst, an initiator and a dehydrating agent.
In another embodiment, the catalyst is used in an amount of 0.001 to 5wt% thereof, the initiator is used in an amount of no more than 5wt% (e.g., without limitation, 0.1 to 4wt%, 1 to 3wt%, etc.) and the dehydrating agent is used in an amount of 0.2 to 1.6wt% thereof, based on the mass of glycolide used.
In another embodiment, the molten glycolide is obtained by subjecting purified glycolide to a melt mixing kettle.
In another embodiment, the glycolide has a purity of 98% or more; preferably not less than 98.5%, and acidity not exceeding 20mmol/kg.
In another embodiment, the purified glycolide is added into a melt mixing kettle, the temperature is raised to 90-120 ℃ under normal pressure, the reaction auxiliary agent is added while stirring, the molten glycolide and the reaction auxiliary agent are uniformly mixed to obtain a fluid premix, and then the premix is conveyed to a static mixer.
In another embodiment, the reaction aid is added dropwise to the melt-mixing kettle by injection.
In another embodiment, the tackifying equipment in step (2) is devolatilized at an absolute pressure of less than or equal to 500Pa and a temperature of from 220 to 250 ℃.
In another embodiment, the screw length to diameter ratio of the devolatilization section may be set to 30 to 100, such as, but not limited to, 40 to 50, 60 to 90, and the like.
In another embodiment, the chain extender in step (2) is selected from one or two or more of the following: epoxy chain extender ADR, maleic anhydride and glycidyl methacrylate.
In another embodiment, the chain extender is used in an amount of about 0.1 to 1wt% of the theoretical mass of the polyglycolic acid calculated on the mass of glycolide.
In another embodiment, the pellets obtained by the granulation in the step (3) are cooled in an aqueous cooling medium, and then dehydrated and dried to obtain a particulate polyglycolic acid.
In another embodiment, the aqueous cooling medium temperature is generally not more than 95 ℃, preferably not more than 50 ℃, more preferably not more than 15 ℃, such as but not limited to 0-15 ℃.
In another embodiment, the cooling time is generally no more than 10 minutes, preferably no more than 5 minutes, more preferably no more than 2 minutes, such as, but not limited to, 10-40 seconds.
Accordingly, the present invention provides a process for producing particulate polyglycolic acid which can effectively maintain a narrow molecular weight and a narrow molecular weight distribution.
Drawings
FIG. 1 shows the morphology of the particulate polyglycolic acid product obtained in example 4.
FIG. 2 shows the morphology of the particulate polyglycolic acid product prepared in comparative example 3.
Detailed Description
The present inventors have made extensive and intensive studies and as a result, have found that a static mixer can be used as a main site for glycolide polymerization, and that the ring-opening polymerization of glycolide is promoted by means of multistage stepwise temperature rise while the mixing effect of glycolide and a reaction auxiliary is enhanced, thereby gradually forming a glycolic acid prepolymer having a certain molecular weight; the chain extender is added at the beginning of the devolatilization section of the tackifying equipment, and the generated small molecular substances can be timely discharged out of the system under the condition of high vacuum degree, so that the bridging degree is further promoted, the molecular weight of the polymer is further improved, the content of terminal carboxyl groups in the final polyglycolic acid product is reduced, and the aging resistance of the product can be improved. On the basis of this, the present invention has been completed.
It should be noted here that the "tackifying device" in the present invention plays a role in devolatilizing, which can promote further polymerization of glycolic acid prepolymer, and timely remove the generated small molecule removal system, so as to further increase the molecular weight of the polymer, and correspondingly, the viscosity of the polymer; the "tackifying means" in the art may be, for example and without limitation, a twin screw extruder provided with only a devolatilization section.
Process for producing particulate polyglycolic acid
The invention provides a method for preparing granular polyglycolic acid, which comprises the following steps:
the method comprises the following steps of firstly, prepolymerizing molten glycolide and a reaction auxiliary agent in a static mixer to obtain a glycolic acid prepolymer with a certain molecular weight;
secondly, carrying out final polymerization on the glycolic acid prepolymer and the chain extender through tackifying equipment to obtain a molten product;
and thirdly, extruding and granulating the molten product obtained in the second step, and cooling the molten product in an aqueous cooling medium to obtain granular polyglycolic acid.
The static mixer in the first step adopts at least 2-section gradient heating mode, for example 2-10-section gradient heating mode; preferably, 3 to 7 stages are employed.
In one embodiment of the invention, the first stage temperature of the static mixer is in the range of 120-220 ℃, such as but not limited to 140-170 ℃, 150-180 ℃, 130-200 ℃ and the like; the final temperature range is 130-250 deg.C, such as but not limited to 150-200 deg.C, 190-230 deg.C, 220-250 deg.C, etc.
In one embodiment of the invention, the second stage of the static mixer is increased in temperature by between 10-100 ℃ over the first stage, such as but not limited to 40-50 ℃, 20-70 ℃, 30-60 ℃, 80-90 ℃ and the like; the last stage is raised from the temperature of the previous adjacent stage by between 0-30 deg.C, such as but not limited to 10-20 deg.C, etc.
In one embodiment of the invention, the static mixer is provided with four sections, wherein the temperature of the first section is set to be 120-180 ℃, the temperature of the second section is set to be 190-210 ℃, the temperature of the third section is set to be 210-220 ℃, and the temperature of the fourth section is set to be 220-230 ℃.
In one embodiment of the invention, the static mixer is provided with five sections, wherein the temperature of the first section is set to be 150-170 ℃, the temperature of the second section is set to be 190-200 ℃, the temperature of the third section is set to be 200-210 ℃, the temperature of the fourth section is set to be 210-220 ℃, and the temperature of the fifth section is set to be 220-230 ℃.
In one embodiment of the invention, the static mixer is provided with three sections, wherein the temperature of the first section is set to be 190-220 ℃, the temperature of the second section is set to be 205-240 ℃, and the temperature of the third section is set to be 220-250 ℃.
The glycolic acid prepolymer obtained in the first step above has a weight average molecular weight of about 5 to 15 ten thousand.
Static mixers commonly used in the art, such as, but not limited to, SK type static mixers, SX type static mixers, SV type static mixers, and the like, may be used.
In one embodiment of the present invention, the reaction auxiliary in the first step comprises a catalyst, an initiator and a dehydrating agent; in terms of the amount of the reaction aid, the catalyst is used in an amount of about 0.001 to 5wt% based on the mass of glycolide, the initiator is used in an amount of not more than about 5wt% (for example, but not limited to, 0.1 to 1 wt%) based on the mass of glycolide, and the dehydrating agent is used in an amount of about 0.2 to 1.6wt% based on the mass of glycolide.
The catalyst may be selected from at least one of tin-based compounds, antimony-based compounds, or zinc-based compounds, such as, but not limited to, stannous octoate, stannous chloride, tin lactate, antimony trioxide, diethyl zinc, or zinc acetate dihydrate.
The initiator may be selected from one or both of alkane substances having a hydroxyl structure such as primary or secondary alcohols (e.g., n-propanol, isopropanol, n-butanol, isobutanol, etc.) or aromatic substances having a hydroxyl active group (e.g., benzyl alcohol, phenethyl alcohol, etc.).
The dehydrating agent may be selected from carbodiimide, polycarbodiimide, or carbodiimide-based compounds (such as, but not limited to, N' -diisopropylcarbodiimide, dicyclohexylcarbodiimide, etc.).
To prevent local excess concentrations of the reaction aid in molten glycolide, in one embodiment of the invention, the reaction aid may be added dropwise to the melt-mixing kettle by injection.
In one embodiment of the invention, purified glycolide is added into a melt mixing kettle, the temperature is raised to 90-120 ℃ under normal pressure, reaction auxiliary agents are added while stirring, so that the molten glycolide and the reaction auxiliary agents are uniformly mixed to obtain a fluid premix, and then the premix is conveyed to a static mixer; the purity of the glycolide is 98 percent; preferably not less than 98.5%, and acidity not exceeding 20mmol/kg.
In one embodiment of the present invention, the particle size D of the glycolide 90 Less than or equal to 200 mu m, purity more than or equal to 98.5 percent and acidity less than or equal to 20mmol/kg.
In one embodiment of the invention, the total length of time the material is in the static mixer during operation is generally not more than 150 minutes, such as, but not limited to, 60-90 minutes.
In one embodiment of the present invention, the glycolic acid prepolymer obtained in the first step has a weight average molecular weight of about 5 to 15 ten thousand.
In the second step, the tackifying equipment is only provided with a devolatilization section, the absolute pressure of the devolatilization section is less than or equal to 500Pa, and the temperature is set to be 220-250 ℃.
Preferably, the screw length to diameter ratio of the devolatilization section is set to 30 to 100, such as, but not limited to, 50 to 60.
In the production process, the chain extender can be added at the beginning of the devolatilization section in the second step through weight loss, and the glycolic acid prepolymer and the chain extender are mixed and enter the devolatilization section together for final polymerization. In addition, according to actual requirements, a proper amount of processing aids (such as heat stabilizers, antioxidants, hydrolytic resistance agents and the like) can be added at the beginning of the devolatilization section by weight loss weighing.
It should be noted here that in the present technology, the tackifying device plays a role of devolatilization, which is equivalent to the devolatilization section of the static mixer, and can promote further polymerization of the glycolic acid prepolymer, and remove the generated small molecules in time, so as to further increase the molecular weight of the polymer.
In one embodiment of the present invention, the chain extender used in the second step may be selected from at least one of epoxy chain extender ADR, maleic anhydride or glycidyl methacrylate; the charged amount of the chain extender is about 0.1-1wt% of the theoretical mass of the polyglycolic acid calculated on the mass of glycolide.
In the third step, pellets obtained by passing the molten product obtained by the final polymerization through a die are cooled in an aqueous cooling medium, and then dehydrated and dried to obtain particulate polyglycolic acid.
In one embodiment of the present invention, the aqueous cooling medium may be water alone (e.g., tap water, deionized water, purified water, etc.), alcohols (e.g., ethanol, n-propanol, etc.) or esters (e.g., methyl acetate, ethyl acetate, etc.), or a mixture of water and a solvent having good compatibility with water, such as alcohols or esters; preferably deionized water.
In one embodiment of the invention, the temperature of the aqueous cooling medium is generally not more than 95 ℃, preferably not more than 50 ℃, more preferably not more than 15 ℃, such as but not limited to 0-15 ℃, for example using an ice water mixture or ethanol or a mixture of water and ethanol in a mass ratio of 1:1 to obtain an aqueous cooling medium of 0 ℃; the cooling time of the granulated pellets in the aqueous cooling medium is generally not more than 10 minutes, preferably not more than 5 minutes, more preferably not more than 2 minutes, such as, but not limited to, 10-40 seconds.
In one embodiment of the present invention, the discharge port of the tackifying device used in the second step is connected to an underwater pelletizer, the molten product in the third step is extruded through the discharge port of the tackifying device and enters the underwater pelletizer, and is extruded and pelletized through a die of the underwater pelletizer, the pelletized pellets are cooled in an aqueous cooling medium, and then are conveyed through a conveying pipeline into a centrifugal dehydrator for dehydration, and the dehydrated pellets are dried to obtain the pelletized polyglycolic acid.
It should be noted that the aqueous cooling medium is mainly used as a transport medium in the transport line to transport the pellets forward to the centrifugal dehydrator.
In one embodiment of the present invention, the drying conditions are: drying for 1-5 hours at 100-120 ℃ in the air with the dew point of-50-40 ℃.
The particulate polyglycolic acid product produced by the process of the present invention has a molecular weight distribution index of about 1.2 to 1.3.
The granular polyglycolic acid product prepared by the method is approximately spherical particles, the surface is relatively smooth, no sharp or sharp bulge or corner exists, and the particles are uniform in thickness; the average particle diameter of the particles is 1.0 to 5.0mm, preferably 2.0 to 3.0mm; the coefficient of variation of the particle diameter is 1.0 to 7.0%, preferably 2.0 to 5.0%.
As used herein, "distribution index" is a parameter D representing the width of molecular weight distribution, D = M (w)/M (n), where M (w) is the weight average molecular weight, M (n) is the number average molecular weight, D =1 is a polymer of uniform molecular weight, and the value of D is broader in its molecular weight distribution and greater in the degree of polydispersity as the value of D is greater than 1. The measurement method generally employs Gel Permeation Chromatography (GPC) to measure M (w) and M (n) of a sample, and then calculates the ratio of the two.
As used herein, "average particle size" refers to the average particle size obtained by summing the diameters of all particles in a test sample and then dividing by the total number of particles.
As used herein, the "particle diameter variation coefficient" is calculated by the following equation: standard deviation of particle size/average particle size X100%
The glycolide content of the reaction mass (i.e., the glycolide mass) used in the process of the invention can be determined by gas chromatography methods well known in the art, and the acidity by potentiometric titration methods well known in the art (e.g., by automated potentiometric titrators).
To make the features and effects of the present invention comprehensible to those skilled in the art, general description and definitions are made below with reference to terms and expressions mentioned in the specification and claims. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
The theory or mechanism described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, i.e., the present disclosure may be practiced without limitation to any particular theory or mechanism.
All features defined herein as numerical ranges or percentage ranges, such as values, amounts, levels and concentrations, are for brevity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to cover and specifically disclose all possible subranges and individual numerical values (including integers and fractions) within the range.
As used herein, the term "about" when used to modify a numerical value means within + -5% of the error margin measured for that value.
The features mentioned above with reference to the invention, or the features mentioned with reference to the embodiments, can be combined arbitrarily. All features disclosed in this specification may be combined in any combination, provided that there is no conflict between such features and the combination, and all possible combinations are to be considered within the scope of the present specification. Each feature disclosed in this specification may be replaced by an alternative feature serving the same, equivalent, or similar purpose. Thus, unless expressly stated otherwise, the features disclosed are merely generic examples of equivalent or similar features.
The main advantages of the invention are:
1. according to the invention, glycolide and a reaction auxiliary agent are fully and uniformly mixed through a melt mixing kettle to obtain a premix, and the premix is introduced into a static mixer for prepolymerization, wherein the static mixer can play a role in low-shear high-dispersion on the premix, so that the heat accumulation in a local area in the material can be prevented and eliminated, the occurrence of side reactions such as thermal degradation and the like caused by overhigh temperature in the local area due to uneven heating in the material can be effectively prevented, good prepolymerization of glycolide can be ensured, a glycolic acid prepolymer with a certain molecular weight can be obtained, and the glycolic acid prepolymer is introduced into tackifying equipment for final polymerization, so that the time of the material subjected to high-shear action in the tackifying equipment can be effectively shortened, the occurrence of side reactions such as thermal degradation and the like can be favorably inhibited, the occurrence of ester exchange reaction can be favorably inhibited, the content of oligomers and/or low molecular chain substances in a system can be reduced, the molecular weight of the prepared polyglycolic acid can be remarkably improved, the molecular weight distribution index is smaller, the molecular weight distribution is more uniform, and the aging resistance of the material can be improved.
2. The invention introduces the fluid premix of the molten glycolide into a static mixer, utilizes a cross flow mode to enhance the mixing effect between the glycolide and the reaction auxiliary agent, enables the reaction auxiliary agent to be more uniformly dispersed in a reaction system, simultaneously utilizes a gradient temperature rising mode to firstly more gently initiate the ring-opening polymerization reaction of the glycolide at a relatively low temperature within a relatively short time, then appropriately raises the temperature and appropriately prolongs the time to form a glycolic acid molecular chain which is relatively stable and has reaction activity in the reaction system, and then further increases the glycolic acid molecular chain at a relatively high temperature and within a relatively long time to obtain the glycolic acid prepolymer with a certain molecular weight.
3. In the invention, the chain extender is added at the beginning of the devolatilization section of the tackifying equipment, the chain extender can form 'bridge connection' between polymer molecular chains in the devolatilization stage, and generated small molecular substances can be timely discharged out of a system under the condition of high vacuum degree, thus being beneficial to further promoting the degree of 'bridge connection', further improving the molecular weight of the polymer, reducing the content of terminal carboxyl in the final polyglycolic acid product, improving the aging resistance of the product, and in addition, in order to further improve the water resistance and the thermal stability of the final product, a hydrolytic resistance agent and/or an antioxidant and/or a thermal stabilizer can be added at the beginning of the devolatilization section of the tackifying equipment.
4. The main polymerization reaction is carried out in the static mixer, compared with a dynamic mixing type double-screw extruder, the static mixer has better air tightness, and the influence of oxygen and moisture on the polymerization reaction can be reduced to the maximum extent; the method of the invention utilizes the characteristic of good uniform heat transfer effect of the static mixer, and can ensure that the molecular chain in the polymerization reaction can be stably increased for a longer time.
5. The invention is suitable for amplification production, is beneficial to saving the modification cost of the process flow, can realize low-carbonization continuous production and has outstanding economical practicability.
The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. The experimental procedures, in which specific conditions are not noted in the following examples, are generally carried out according to conventional conditions or according to conditions recommended by the manufacturers. All percentages, ratios, proportions, or parts are by weight unless otherwise specified. The units in weight volume percent in the present invention are well known to those skilled in the art and refer to, for example, the weight (g) of solute in 100ml of solution. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. In addition, any methods and materials similar or equivalent to those described herein can be used in the methods of the present invention. The preferred embodiments and materials described herein are intended to be exemplary only.
In the examples described below, the glycolide content of the purified glycolide powders concerned can be determined by gas chromatography methods known in the art, the glycolide powder particle size being determined by the mesh size of the sieve, for example by using a 70 mesh (corresponding to about 200 μm) sieve or by using a sieve with more than 70 mesh, the glycolide powder being capable of being sieved and having a particle size substantially satisfying "D 90 Less than or equal to 200 μm ", and the acidity is determined by potentiometric titration methods known in the art (for example, by means of an automated potentiometric titrator).
For the test of the molecular weight and the distribution of polyglycolic acid, gel Permeation Chromatography (GPC) method is used for the test, which is as follows:
a0.2 g sample of PGA was dissolved in 100mL of hexafluoroisopropanol solution having a sodium trifluoroacetate content of 5mmol/L, filtered through a polytetrafluoroethylene filter having a pore size of 0.4. Mu.m, and 20. Mu.L of the filtrate was introduced into an "LC-20AD GPC" sample injector manufactured by Shimadzu (Japan) under test conditions: the column temperature is 40 ℃; eluent: hexafluoroisopropanol with 5mmol/L of sodium trifluoroacetate dissolved therein; the flow rate is 1mL/min; a detector: an RI detector; and (3) correction: molecular weight correction was performed using five different standards of polymethyl methacrylate varying in molecular weight between 7000 and 200000.
In the following examples, the melt stirring tank used had a volume of 50L, the static mixer 8L, the melt metering pump had a maximum delivery flow rate of 10L/h, and the melt pump had a maximum delivery flow rate of 12L/h.
The static mixer used in the following examples was a commercially available SK type static mixer.
The amounts of the reaction assistants added in examples 1 to 5 are shown in Table 1 below.
TABLE 1 addition amount of reaction auxiliary
The kinds of reaction assistants used in examples 1 to 5 are shown in Table 2 below.
TABLE 2 kinds of reaction assistants
The kinds of chain extenders used in examples 1 to 5 and the amounts thereof are shown in table 3 below.
TABLE 3 kinds and amounts of chain extenders
Examples 1-5 above particulate polyglycolic acid was prepared using the following method:
purifying the glycolide (particle size D) 90 Not more than 200 mu m, the purity not less than 98 percent and the acidity not more than 20 mmol/kg) is added into a melt mixing kettle, the temperature is raised to about 90-120 ℃ under normal pressure, the reaction auxiliary agents are all added into the melt mixing kettle within about 5min by weight parts in the existing injection way while stirring, the stirring is continued to ensure that the molten glycolide and the reaction auxiliary agents are uniformly mixed to obtain a pre-mixed material in a fluid state, then the pre-mixed material in the fluid state is conveyed to a static mixer by a melt metering pump for pre-polymerization to obtain a glycolic acid pre-polymer, then the glycolic acid pre-polymer is conveyed to a tackifying device (for example, a double screw extruder only provided with a devolatilization section), a chain extender is added at the beginning of the devolatilization section of the tackifying device by adopting a weight loss scale, the glycolic acid pre-polymer and the chain extender are mixed and enter the devolatilization section of the tackifying device for final polymerization, the obtained molten product is extruded out through a discharge port of the tackifying device and then is extruded into underwater, granulated granules are extruded and cooled in an aqueous cooling medium (for example, deionized water is then is extruded and granulated through a mouth die of the underwaterConveying the granules to a centrifugal dehydrator for dehydration through a conveying pipeline, and drying the dehydrated granules to obtain the granular polyglycolic acid.
The temperature of the heated molten glycolide in the melt-mixing kettle in examples 1-5 is shown in table 4 below.
TABLE 4
| Item | Example 1 | Example 2 | Example 3 | Example 4 | Example 5 |
| Temperature (. Degree.C.) | About 90 | About 102 | About 118 | About 120 | About 115 |
Note: the time from the time each batch of glycolide powder entered the melt-mixing kettle to the time the premix was obtained was about 20min.
The process conditions for the static mixer of examples 1-5 are shown in Table 5-1 below:
TABLE 5-1 temperature parameters of the sections of the static mixer
| Item | Static mixer | First stage | Second section | Third stage | Fourth stage | Fifth stage |
| Example 1 | Five sections in total | About 150 deg.C | About 190 deg.C | About 202 deg.C | About 213 deg.C | About 220 deg.C |
| Example 2 | Five sections in total | About 168 deg.C | About 200 deg.C | About 210 deg.C | About 220 deg.C | About 230 deg.C |
| Example 3 | Four sections in total | About 124 deg.C | About 190 deg.C | About 215 deg.C | About 228 deg.C | / |
| Example 4 | Four sections in total | About 178 deg.C | About 208 deg.C | About 220 deg.C | About 230 deg.C | / |
| Example 5 | Three segments in total | About 220 deg.C | About 238 deg.C | About 250 deg.C | / | / |
For examples 1-2, the time for the material in the static mixer to pass through the first stage was about 5min, the time for the material to pass through the second stage was about 5min, the time for the material to pass through the third stage was about 10min, the time for the material to pass through the fourth stage was about 15min, and the time for the material to pass through the fifth stage was about 55min; for examples 3-4, the time for the material in the static mixer to pass through the first stage was about 5min, the time for the material to pass through the second stage was about 10min, the time for the material to pass through the third stage was about 15min, and the time for the material to pass through the fourth stage was about 60min; for example 5, the time for the material in the static mixer to pass through the first stage was about 5min, the time for the material to pass through the second stage was about 20min, and the time for the material to pass through the third stage was about 65min.
The parameter settings of the devolatilization section in the tackifying apparatuses of examples 1 to 5 are shown in the following tables 5 to 2:
TABLE 5-2 devolatilization section parameters in tackifying equipment
| Item | Temperature (. Degree.C.) | Absolute pressure (Pa) | Length-diameter ratio of screw | Screw rotation speed (r/min) |
| Example 1 | About 220 | About 120 | About 56 | About 60 |
| Example 2 | About 236 | About 150 | About 60 | About 30 |
| Example 3 | About 232 f | About 180 | About 50 | About 45 |
| Example 4 | About 238 | About 100 | About 55 | About 50 |
| Example 5 | About 250 f | About 500 | About 54 | About 60 |
The time for the materials of examples 1-5 to pass through the devolatilization section of the viscosifying device was about 15 minutes.
The temperature settings for the lines from the melt mixing kettle to the viscosity increasing equipment in examples 1-5 are shown in Table 6 below:
TABLE 6 pipeline temperature parameters
Note: the supply flow rates of the melt metering pump and the melt pump used in examples 1 to 5 described above were each set to about 5.3L/h.
The process conditions for water-cooling granulation and drying in examples 1-5 are shown in Table 7 below:
TABLE 7 Process conditions for water-cooling granulation and drying
The molecular weight of glycolic acid prepolymer produced by the static mixer in examples 1-5, the molecular weight of particulate polyglycolic acid finally produced, and the melt index are shown in Table 8 below.
TABLE 8 molecular weight and melt index test results
The particulate polyglycolic acid prepared in examples 1 to 5 was approximately spherical particles, had a smooth and round surface, and had no sharp or sharp protrusions or corners. For each example, 40 particles were randomly selected and measured, and the standard deviation of the particle size/average particle size × the particle size variation coefficient of 100% was calculated, and the results are shown in table 9 below.
TABLE 9 particle diameter and particle diameter variation coefficient test results
| Item | Average particle diameter (mm) | Standard deviation (mm) | Coefficient of variation of particle size |
| Example 1 | 2.8 | 0.13 | 4.6％ |
| Example 2 | 2.8 | 0.11 | 3.9％ |
| Example 3 | 2.6 | 0.08 | 3.1％ |
| Example 4 | 2.5 | 0.05 | 2.0％ |
| Example 5 | 2.1 | 0.07 | 3.3％ |
Examples 6-8 are provided below on the basis of example 4, with examples 6-8 being substantially the same as example 4 except that examples 6-8 have other processing aids added at the beginning of the devolatilization section in addition to the chain extender, as shown in table 10 below.
TABLE 10 amounts of other processing aids
| Item | Heat stabilizer | Antioxidant agent | Anti-hydrolysis agent |
| Example 6 | About 1.2% | / | / |
| Example 7 | About 1.2% | About 0.4% | / |
| Example 8 | About 1.2% | About 0.4% | About 0.2% |
Note: the amounts of processing aids in table 10 are in percent of the theoretical mass of polyglycolic acid calculated based on the mass of glycolide.
In table 10 above, for example, the heat stabilizer is a mixture of calcium stearate soap and zinc palmitate soap 1:1 by mass ratio, the antioxidant is a mixture of antioxidant 1010 and antioxidant B215 by mass ratio 3:1, and the hydrolysis resistant agent is bis (2,6-diisopropylphenyl) carbodiimide.
Referring to example 4, comparative examples 1-4 are provided below, specifically as follows:
comparative example 1 is essentially the same as example 4 except that comparative example 1 does not add any processing aid at the beginning of the devolatilization section.
Comparative example 2 is substantially the same as example 4 except that comparative example 2 does not add a chain extender at the beginning of the devolatilization section, but adds a heat stabilizer, an antioxidant, and an anti-hydrolysis agent.
Comparative example 3 polyglycolic acid was prepared based on a conventional reaction type twin-screw extruder, and then granulated by water cooling, air cooling, granulation and drying (i.e., the existing extrusion granulation process) to obtain the granulated polyglycolic acid by the following specific method:
purified glycolide (particle size D) 90 Less than or equal to 200 mu m, the purity is more than or equal to 98.5 percent, the acidity is less than or equal to 20 mmol/kg) is added into a double-screw extruder from a main feeding port (a melting mixing kettle is not used), reaction auxiliary agents are added through a side feeding port, so that glycolide is subjected to polymerization reaction in the double-screw extruder, chain extender is added at the beginning of a devolatilization section of the double-screw extruder, then molten polyglycolic acid resin extruded by a head of the double-screw extruder is pulled into a water bath filled with water at about 5 ℃ in a bracing way for cooling for 15s, strips are pulled and placed on a steel belt conveyor after the surfaces of the strips are solidified, the strips are swept for 5 times by air with the dew point of-50 ℃ and the temperature of about 26 ℃ and are cooled for about 25s in the air,cooling and solidifying completely, cutting the material strips by a rotary cutter, and drying the formed particles in air with dew point of-50 ℃ and temperature of about 120 ℃ for 3 hours to obtain the granular polyglycolic acid.
In comparative example 3, there was no prepolymerization in a static mixer, and no underwater granulation and water cooling were employed, but water cooling, air cooling, and rotary granulation were employed.
The types and the amounts of the reaction auxiliary agent and the chain extender in the comparative example 3 are the same as those in the example 4, and the twin-screw extruder used in the comparative example 3 is provided with a mixing section, a reaction section and a devolatilization section along the feeding direction of the material, wherein the mixing section is provided with three sections, the temperature of the first section is set to be about 95 ℃, the temperature of the second section is set to be about 115 ℃, the temperature of the third section is set to be about 130 ℃, the reaction auxiliary agent is added into the first section of the mixing section, the time for the material to pass through the first section is about 1min, the time for the material to pass through the second section is about 3min, and the time for the material to pass through the third section is about 6min, namely, the total time for the material to pass through the mixing section is about 10min; the reaction section is provided with four sections in total, the temperature of the first section is set to be about 204 ℃, the temperature of the second section is set to be about 210 ℃, the temperature of the third section is set to be about 220 ℃, the temperature of the fourth section is set to be about 230 ℃, the time for the material to pass through the first section is about 5min, the time for the material to pass through the second section is about 10min, the time for the material to pass through the third section is about 20min, and the time for the material to pass through the fourth section is about 45min, namely the total time for the material to pass through the reaction section is about 80min; the chain extender was added at the beginning of the devolatilization section, the temperature of the devolatilization section was set at about 240 ℃, the absolute pressure was set at about 150Pa, the screw length to diameter ratio was about 50, and the time for the material to pass through the devolatilization section was about 15min.
Comparative example 4 is substantially the same as comparative example 3 except that in comparative example 4, a heat stabilizer, an antioxidant and an anti-hydrolysis agent are added in addition to a chain extender at the beginning of the devolatilization section of the twin-screw extruder, and the types and the amounts thereof are the same as those in example 8.
The molecular weights and melt indices of the particulate polyglycolic acids obtained in examples 4 and 6 to 8, comparative examples 1 to 4 are shown in Table 11 below.
TABLE 11 molecular weight and melt index test results
The particulate polyglycolic acid prepared in examples 4 and 6 to 8, comparative examples 1 to 2 was approximately spherical particles having a smooth surface without sharp or sharp protrusions or corners; the granular polyglycolic acid prepared in comparative examples 3 to 4 was approximately cylindrical granules, and had different particle sizes, some of which were large at one end and small at the other end, and had sharp cross sections with sharp corners at the edges of the cross sections. See figures 1 and 2.
For each of the examples and comparative examples, 40 particles were randomly selected and measured, and the standard deviation of the particle diameter/average particle diameter × the coefficient of variation of the particle diameter of 100% was calculated, with the results shown in table 12 below.
TABLE 12 particle diameter and particle diameter variation coefficient test results
During the pelletization of comparative examples 3 and 4, it was visually confirmed that the strands formed from the molten polyglycolic acid resin extruded from the head of the twin-screw extruder were broken during the drawing process, and the strands were uneven in thickness at various locations before being drawn into the water bath, and were distorted at various locations during the cooling on the steel belt conveyor after cooling in the water bath.
For the granular polyglycolic acid obtained in examples 4 and 6 to 8 and comparative examples 1 to 4, a lot of specimens (15 in total, divided into 3 groups on average) were prepared according to the tensile test standard GB/T1040.4-2006, respectively, marked, and then the specimens were subjected to an aging test in a constant temperature and humidity aging box at a temperature of about 50 ℃ and a relative humidity of about 90%, and a group of specimens were taken out every 5 days, tested for tensile strength, and averaged, and the test results are shown in table 13 below.
TABLE 13 tensile Strength test results
As can be seen from table 13, the tensile strength retention rates of the materials of examples 4-8 were about 80.2%, 81.9%, 83.8%, 87.2%, respectively, and the tensile strength retention rates of the materials of comparative examples 1-4 were about 69.6%, 74.1%, 49.5%, 59.6%, respectively, over 10 days under constant temperature and humidity conditions of 50 ℃ and a relative humidity of about 90%.
The foregoing is merely a preferred embodiment of the invention and is not intended to limit the scope of the invention, which is defined by the claims appended hereto, and any other technical entity or method that is encompassed by the claims as broadly defined herein, or equivalent variations thereof, is contemplated as being encompassed by the claims.
Claims (10)
1. A process for the preparation of particulate polyglycolic acid, comprising the steps of:
(1) Prepolymerizing molten glycolide and a reaction auxiliary in a static mixer to obtain a glycolic acid prepolymer;
(2) Carrying out final polymerization on the glycolic acid prepolymer obtained in the step (1) and a chain extender through tackifying equipment to obtain a molten product;
(3) And (3) extruding and granulating the molten product obtained in the step (2), and cooling to obtain granular polyglycolic acid.
2. The method according to claim 1, wherein the static mixer used in step (1) is a gradient mixer with at least 2 stages.
3. The process according to claim 2, wherein the static mixer used in step (1) is a 2-10 stage gradient, preferably 3-7 stage static mixer.
4. The method of claim 2, wherein the first stage temperature is in the range of 120-220 ℃; the temperature of the last stage is 220-250 ℃.
5. The method of claim 2, wherein the temperature of the second section is increased by between 10-100 ℃ over the temperature of the first section; the temperature of the last section is increased by 0-30 ℃ compared with the temperature of the previous adjacent section.
6. The method according to claim 1, wherein the reaction auxiliary in the step (1) comprises a catalyst, an initiator and a dehydrating agent.
7. The method of claim 1, wherein the molten glycolide is obtained by subjecting purified glycolide to a melt-mixing kettle.
8. The method according to claim 1, wherein the tackifying equipment in step (2) is devolatilized at an absolute pressure of 500Pa or less and a temperature of 220 to 250 ℃.
9. The method according to claim 1, wherein the chain extender in the step (2) is one or more selected from the group consisting of: epoxy chain extender ADR, maleic anhydride and glycidyl methacrylate.
10. The process according to claim 1, wherein the pellets obtained by the granulation in the step (3) are cooled in an aqueous cooling medium, dehydrated and dried to obtain the granulated polyglycolic acid.
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| CN112469763A (en) * | 2018-10-29 | 2021-03-09 | 上海浦景化工技术股份有限公司 | High temperature and aging resistant polyglycolide copolymers and compositions thereof |
| CN112469760A (en) * | 2018-10-29 | 2021-03-09 | 上海浦景化工技术股份有限公司 | Integrated preparation method for producing polyglycolic acid product |
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