CN115260459A - Polylactic acid-glycolic acid copolymer and preparation method thereof - Google Patents
Polylactic acid-glycolic acid copolymer and preparation method thereof Download PDFInfo
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- CN115260459A CN115260459A CN202211072469.7A CN202211072469A CN115260459A CN 115260459 A CN115260459 A CN 115260459A CN 202211072469 A CN202211072469 A CN 202211072469A CN 115260459 A CN115260459 A CN 115260459A
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- lactide
- polylactic acid
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- glycolic acid
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- 238000007334 copolymerization reaction Methods 0.000 claims description 45
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- WVDDGKGOMKODPV-UHFFFAOYSA-N Benzyl alcohol Chemical compound OCC1=CC=CC=C1 WVDDGKGOMKODPV-UHFFFAOYSA-N 0.000 description 3
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- 229920001634 Copolyester Polymers 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 description 1
- 239000004696 Poly ether ether ketone Substances 0.000 description 1
- 239000004734 Polyphenylene sulfide Substances 0.000 description 1
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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
- C08G63/02—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds
- C08G63/06—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds derived from hydroxycarboxylic acids
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
- C08G63/78—Preparation processes
Abstract
The present invention relates to a polylactic acid-glycolic acid copolymer comprising: a structural unit A represented by the formula (I), and a structural unit B represented by the formula (II),
Description
Technical Field
The invention belongs to the technical field of high polymer materials, and particularly relates to a polylactic acid-glycolic acid copolymer and a preparation method thereof.
Background
In recent years, under the promotion of scientific and technological progress and sustainable development concept, the treatment of plastic pollution in the world is more concerned, and the biodegradable polyester gradually becomes a hotspot in material foundation and application research. Polyglycolic acid (PGA) is a novel biodegradable engineering plastic. Based on excellent comprehensive properties, the application of PGA is moving from the field of traditional medical materials to the field of special industrial application, and the PGA is widely concerned in the fields of degradable plastics, barrier materials, oil and gas exploitation materials and the like. Compared with traditional degradable materials such as polylactic acid (PLA), poly Butylene Succinate (PBS), PGA has a plurality of advantages: 1) The heat-resisting temperature is high, and the melting point reaches 220 ℃; 2) The strength and the modulus are high, and the strength is close to that of high-performance engineering plastics such as polyether-ether-ketone, polyphenylene sulfide and the like; 3) The degradation speed is high, the ester bond unit content in the PGA is high, and the degradation speed is obviously higher than that of common degradable polyester materials such as PLA, PBS and the like; 4) The barrier property is excellent, and the barrier property to carbon dioxide and oxygen is hundreds of times higher than that of PET; 5) The solvent resistance is strong, and the solvent is not dissolved in common organic solvents such as tetrahydrofuran, chloroform, N-dimethylformamide and the like, but only dissolved in special solvents such as hexafluoroisopropanol and the like.
Although PGA has many advantages, PGA has high molecular chain regularity and high crystallinity, which causes the PGA to have high brittleness, poor toughness, low elongation at break, and narrow processing temperature width, thus limiting further applications of PGA.
The introduction of the levorotatory lactide into the PGA can effectively reduce the melting point of the PGA on the premise of keeping high thermal stability, thereby widening the melting processing temperature range of the PGA. However, the levorotatory lactide segment with high optical purity has strong crystallization capability and can be discharged into PGA crystal lattices as a chemical defect unit, so that the introduction of the levorotatory lactide unit has no obvious toughening effect on PGA, and the toughness of the PGA cannot be effectively improved.
Meso lactide or low-light pure lactide is a byproduct in the preparation of high-light pure lactide, and has high yield and low price. The melting point (43-47 ℃) of meso-lactide is far lower than that (94-96 ℃) of high-gloss pure lactide, and PLA prepared from meso-lactide or low-gloss pure lactide is amorphous, has poor heat resistance and mechanical property, and is difficult to be used as plastics on a large scale. Therefore, the comprehensive utilization of meso-lactide or low-light pure lactide is a difficulty in the PLA industrial chain.
Disclosure of Invention
Due to poor mechanical properties and narrow processing temperature width of the polyglycolic acid, further application of the polyglycolic acid is limited. The present inventors have unexpectedly found that efficient toughening of PGA can be achieved by introducing meso-lactide (or oligomers of meso-lactide) which is not industrially fully used at present, into a PGA chain by copolymerization, while widening the melt processing temperature range of PGA and maintaining its good thermal stability, and polylactic acid-glycolic acid copolymers with excellent application prospects are obtained.
In one aspect, the present invention relates to a polylactic acid-glycolic acid copolymer comprising: a structural unit A represented by the formula (I), and a structural unit B represented by the formula (II),
wherein, all the structural units are connected through ester bonds.
In one embodiment, the polylactic acid-glycolic acid copolymer of the present invention contains the structural unit a in an amount of 0.5 to 25% by weight, preferably 0.5 to 20% by weight, based on the weight of the polylactic acid-glycolic acid copolymer.
In one embodiment, the polylactic acid-glycolic acid copolymer of the present invention has a content of the structural unit B of 75 to 99.5 wt%, preferably 80 to 99.5 wt%, based on the weight of the polylactic acid-glycolic acid copolymer.
In another aspect, the present invention also relates to a method for preparing the polylactic acid-glycolic acid copolymer of the present invention, comprising the steps of:
copolymerizing lactide copolymerization units with glycolide in the presence of a catalyst to obtain the polylactic acid-glycolic acid copolymer, wherein the lactide copolymerization units are selected from: meso-lactide, meso-lactide oligomers, and combinations thereof.
Detailed Description
General definitions and terms
All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety if not otherwise indicated.
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 case of conflict, the present specification, including definitions, will control.
All percentages, parts, ratios, etc. are by weight unless otherwise indicated.
When an amount, concentration, or other value or parameter is given as either a range, preferred range, or a pair of upper and lower preferable values or specific values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. When a range of numerical values is recited herein, unless otherwise stated, the range is intended to include the endpoints thereof, and all integers and fractions within the range. The scope of the invention is not limited to the specific values recited when defining a range.
The terms "about" and "approximately," when used in conjunction with a numerical variable, generally mean that the value of the variable and all values of the variable are within experimental error (e.g., within 95% confidence interval for the mean) or within ± 10% of the specified value, or more.
When values or range ends are described herein, it is to be understood that the disclosure includes the particular values or ends recited.
The words "comprising" or similar words synonymous therewith "including", "containing" and "having" and the like are open-ended and do not exclude additional unrecited elements, steps or components. The expression "consisting of 8230comprises" excludes any element, step or ingredient not specified. The expression "consisting essentially of 8230comprises means that the scope is limited to the specified elements, steps or components, plus optional elements, steps or components that do not materially affect the basic and novel characteristics of the claimed subject matter. It is understood that the expression "comprising" covers the expressions "consisting essentially of and" consisting of \82303030303030A ".
Unless otherwise indicated, the term "combination thereof" means a multi-component mixture of the elements in question, for example two, three, four and up to the maximum possible.
Furthermore, no number of elements or components of the invention have been designated herein before to indicate that no limitation as to the number of elements or components present is intended. Thus, it should be read to include one or at least one and singular forms of a component or ingredient also include the plural unless the numerical value explicitly indicates the singular.
The terms "optionally" or "optionally" as used herein mean that the subsequently described event or circumstance may or may not occur, and that the description includes instances where said event or circumstance occurs and instances where it does not.
The term "one or more" or "at least one" as used herein refers to one, two, three, four, five, six, seven, eight, nine or more.
The term "number average molecular weight" as used herein is alternatively referred to as number average molar mass. If the molecular weight in the polymer is M j Has a mole fraction of x j Number of molecules N j Number average molecular weight
Is composed of
Wherein
The measurement can be carried out by methods such as end group measurement, gel chromatography, membrane osmometry, vapor osmometry, boiling point elevation, mass spectrometry, etc. Molecular weights described herein are number average molecular weights unless otherwise specified. The number average molecular weight and the distribution thereof in the present invention can be measured, for example, by using a Gel Permeation Chromatograph (GPC) or a mass spectrometer.
The term "repeating unit" as used herein refers to a combination of atoms linked in a manner on a polymer chain that is the basic unit that makes up the polymer chain.
The term "degree of polymerization" as used herein refers to the number of consecutive occurrences of repeating units in a polymer molecular chain.
Polylactic acid-glycolic acid copolymer
In one aspect, the present invention relates to a polylactic acid-glycolic acid copolymer comprising a polylactic acid segment and a polyglycolic acid segment, specifically, comprising: the polylactic acid segment composed of the structural unit A and the polyglycolic acid segment composed of the structural unit B are connected to each other through an ester bond. In a specific embodiment, the polylactic acid-glycolic acid copolymer of the present invention is composed of a polylactic acid segment and a polyglycolic acid segment. In a specific embodiment, the polylactic acid-glycolic acid copolymer consists of structural unit a and structural unit B.
By introducing the polylactic acid chain segment into the polyglycolic acid chain segment, the polyglycolic acid can be efficiently toughened and the melt processing temperature range can be widened, and the obtained polylactic acid-glycolic acid copolymer has excellent properties, such as: wider hot working window, increased toughness, elongation at break, notched impact strength, etc.
The levorotatory (or dextrorotatory) lactide chain segment formed by levorotatory (or dextrorotatory) lactide structural units (the structural formula of which is shown as the following) has strong crystallization capability, can be used as chemical defect units to be discharged into PGA crystal lattices, and has no obvious toughening effect on the PGA.
In the invention, the meso-polylactic acid segment with low regularity, weak crystallization ability and strong flexibility is introduced into the polyglycolic acid segment, so that the polyglycolic acid can be efficiently toughened and the melting processing temperature range of the polyglycolic acid can be widened. It is understood that the polyglycolic acid segment and the polylactic acid segment are connected by an ester bond to form a polylactic acid-glycolic acid copolymer.
The meso-polylactic acid segment is composed of meso-lactide structural units (e.g., structural unit a). In the production process, meso-lactide or meso-lactide oligomer may be used as a copolymerization unit to introduce a polyglycolic acid segment.
In one embodiment, the meso-polylactic acid segment included in the polylactic acid-glycolic acid copolymer of the present invention may be formed by one or more structural units a represented by formula (I) being connected to each other through an ester bond:
the polylactic acid-glycolic acid copolymer should contain a proper proportion of polylactic acid segments so that the copolymer has good thermal and mechanical properties. The polylactic acid segment contained in the polylactic acid-glycolic acid copolymer has too low proportion, and cannot effectively toughen and widen the thermal processing window; too high a ratio results in a decrease in heat resistance, strength, and degradation properties of the product. In one embodiment, the content of the structural unit a is 0.5 to 25% by weight, preferably 0.5 to 20% by weight, for example, 0.5, 1.0, 1.5, 2.0, 2.5, 3, 4, 5, 10, 15, 18, 20, 22, 24, 24.5, 25, 0.6, 4.4, 8.9, 19.4, 24.1, 3.9, 8.6, 18.3, 8.3, 9.4, 9.0, 9.1% by weight, or the like, based on the weight of the polylactic acid-glycolic acid copolymer.
The presence of polyglycolic acid segments in the polylactic acid-glycolic acid copolymer can impart advantageous properties of polyglycolic acid to the polymer, such as: high heat-resistant temperature, high strength and modulus, high degradation speed, excellent barrier property and strong solvent resistance. Glycolide can be used as a copolymerization unit to introduce a polyglycolic acid segment during the preparation process.
The polyglycolic acid segment contained in the polylactic acid-glycolic acid copolymer may be formed by one or more structural units B represented by formula (II) being connected to each other via an ester bond:
the polylactic acid-glycolic acid copolymer contains polyglycolic acid segments in a suitable range so that the copolymer can maintain the advantageous properties of PGA while achieving the effects of toughening and widening the hot working temperature window. In one embodiment, the content of the structural unit B is 75 wt% to 99.5 wt%, preferably 80 wt% to 99.5 wt%, for example, 75 wt%, 75.5 wt%, 76 wt%, 77 wt%, 78 wt%, 79.5 wt%, 80 wt%, 80.5 wt%, 85 wt%, 90 wt%, 95 wt%, 97 wt%, 98 wt%, 98.5 wt%, 99 wt%, 99.5 wt%, etc., based on the weight of the polylactic acid-glycolic acid copolymer.
The proportion of structural units (e.g. the content of structural unit a or structural unit B) can be determined using methods conventional in the art, for example using a nuclear magnetic resonance apparatus (NMR), from the characteristic proton absorption peak area ratios.
As an example, the polylactic acid-glycolic acid copolymer of the present invention may comprise one or more of the following formulas (III-1) to (III-2):
wherein x is selected from integers of 5-200, preferably 5-100, such as 5, 10, 50, 100, 150, 200, etc.; y is selected from an integer from 1000 to 2500, preferably from 1400 to 2000, for example 1000, 1250, 1500, 1750, 2000, 2250, 2500, etc.
In the polylactic acid-glycolic acid copolymer, the degree of polymerization of the polylactic acid segment and the degree of polymerization of the polyglycolic acid segment affect the uniformity of the distribution of the two segments. The higher the uniformity of the distribution of the two segments, the more beneficial the mechanical property of the copolymer is increased, so as to obtain the polylactic acid-glycolic acid copolymer with better performance. In the case of polylactic acid-glycolic acid copolymers, when one or more excessively long polylactic acid segments and/or polyglycolic acid segments are present, a decrease in product properties (e.g., toughness, etc.) may result. Therefore, it is advantageous to improve the product performance that the degree of polymerization of the polylactic acid segment and/or the degree of polymerization of the polyglycolic acid segment are in a suitable range. In one embodiment, the polylactic acid segment has a degree of polymerization of about 5 to 200, preferably about 5 to 100, such as 5, 10, 50, 100, 150, 200, and the like. In one embodiment, the polyglycolic acid segments have a degree of polymerization of about 1000 to 2500, preferably about 1400 to 2000, such as 1000, 1250, 1500, 1750, 2000, 2250, 2500, and the like.
The molecular weight of the polylactic acid-glycolic acid copolymer affects the properties (such as melting point, thermal decomposition temperature, mechanical properties, etc.). It is difficult to obtain excellent performance from the polylactic acid-glycolic acid copolymer having too low or too high molecular weight, and it is not suitable for practical use. In one embodiment, the polylactic acid-glycolic acid copolymer of the present invention has a number average molecular weight of about 10 to 15 ten thousand.
Intrinsic viscosity can be used as an indicator parameter for the molecular weight of the polylactic acid-glycolic acid copolymer. Higher molecular weight polymers generally have greater intrinsic viscosity. Intrinsic viscosity can be determined using methods conventional in the art, for example, using a viscometer. The inherent viscosity of the polylactic acid-glycolic acid copolymer of the present invention may be 0.6 to 1.50dL/g, preferably 1.0 to 1.5dL/g, and may be, for example, about 1.28dL/g, 1.27dL/g, 1.28dL/g, 1.19dL/g, 1.15dL/g, 1.02dL/g, 1.21dL/g, 1.17dL/g, 1.09dL/g, 1.11dL/g, 1.32dL/g, 1.51dL/g, or 1.48dL/g.
The thermal decomposition temperature refers to the temperature at which the material decomposes upon heating. Above the thermal decomposition temperature, molecular chains and molecular structures in the polymer material are decomposed (e.g., broken). The high polymer material forming temperature can not exceed the thermal decomposition temperature. The thermal decomposition temperature can be determined using methods conventional in the art, for example, using a thermogravimetric analyzer. The thermal decomposition temperature of the polylactic acid-glycolic acid copolymer can be 200-260 ℃; preferably 230-260 ℃, for example about 251.5 ℃, 250.9 ℃, 249.7 ℃, 247.5 ℃, 240.4 ℃, 218.7 ℃, 248.9 ℃, 247.7 ℃, 241.2 ℃, 248.2 ℃, 235.1 ℃, 247.5 ℃, 248.6 ℃. The thermal decomposition temperature is too low, which is not beneficial to the subsequent processing and use of the material.
The melting point of the polymer refers to the temperature at which the polymer changes from a solid state to a molten state, and the melting process of the polymer has a wider melting temperature range, namely, a melting limit exists. The temperature at which it finally melts completely is generally referred to as the melting point. The melting point can be determined using methods conventional in the art, such as can be measured by using a Differential Scanning Calorimeter (DSC), and the temperature rise rate can be, for example, 10 deg.C/min. The melting point of the polylactic acid-glycolic acid copolymer is 150-225 ℃; preferably 180-225 deg.C, such as about 221.9 deg.C, 222.1 deg.C, 210.7 deg.C, 203.9 deg.C, 185.4 deg.C, 155.4 deg.C, 212.1 deg.C, 203.7 deg.C, 183.2 deg.C, 204.1 deg.C, 193.7 deg.C, 202.9 deg.C, 203.1 deg.C, etc.
The thermal decomposition temperature and the melting point together define a melt processing temperature window (also referred to herein as the thermal processing window) for the polymeric material. The higher the thermal decomposition temperature, the lower the melting point, and the larger the melting processing temperature range, which is beneficial to processing the high polymer material. Herein, the melt processing temperature interval refers to the difference between the thermal decomposition temperature and the melting point. The polylactic acid-glycolic acid of the present invention has a wide melt processing temperature range. In one embodiment, the polylactic acid-glycolic acid of the present invention has a melt processing temperature range of 28 to 70 ℃, preferably 30 to 70 ℃, more preferably 45 to 70 ℃, for example, 29.6 ℃, 28.8 ℃, 39 ℃, 43.6 ℃, 55 ℃, 63.3 ℃, 36.8 ℃, 44 ℃, 58 ℃, 44.1 ℃, 41.4 ℃, 44.6 ℃, 45.5 ℃ and the like.
Notched impact strength: an index, which measures the copolymer of the present invention, is defined as the energy absorbed per unit cross-sectional area when the specimen breaks or fractures under impact loading. Notched impact strength can be determined using methods conventional in the art, for example, in the present invention, can be measured by an impact strength tester. The polylactic acid-glycolic acid copolymer of the present invention may have a notched impact strength of about 3KJ/m 2 Above, e.g. about 3.0KJ/m 2 About 3.2KJ/m 2 About 3.9KJ/m 2 About 5.5KJ/m 2 About 7.4KJ/m 2 About 4.1KJ/m 2 About 5.4KJ/m 2 About 7.2KJ/m 2 About 5.1KJ/m 2 About 5.6KJ/m 2 About 5.8KJ/m 2 About 8.1KJ/m 2 About 6.2KJ/m 2 。
Elongation at break: it is generally expressed in terms of relative elongation at break, i.e., the ratio of the elongation at break of the copolymer fiber to its initial length, expressed as a percentage. Elongation at break = (length at break of material-initial length of material)/initial length. It is an index that characterizes the softness and elastic properties of the copolymer. The greater the elongation at break, the better the softness and elasticity, and the desired elongation at break should be present depending on the use of the fiber. When the copolymer fiber is broken by external force, the ratio of the elongation length before and after stretching to the length before stretching is called the elongation at break. The elongation at break can be determined using methods conventional in the art, for example, in the present invention, by a universal tester. The polylactic acid-glycolic acid copolymer of the present invention may have an elongation at break of 3.0 to 25%, for example, about 4.4%, 6.0%, 7.9%, 9.7%, 18.9%, 21.2%, 7.4%, 9.5%, 19.5%, 9.7%, 10.9%, 8.5%, 9.2%, and the like.
Young's modulus: in the elastic deformation stage of the material, the stress and the strain are in a proportional relation, and the proportionality coefficient of the material is called Young modulus. The young's modulus can be regarded as an index for measuring the difficulty of the material in elastic deformation, and the larger the young's modulus is, the larger the stress for causing the material to generate a certain elastic deformation is, i.e. the higher the rigidity of the material is, i.e. the smaller the elastic deformation is generated under the action of a certain stress. Young's modulus can be measured using methods conventional in the art, for example, in the present invention, by a universal tester. The young's modulus of the polylactic acid-glycolic acid copolymer of the present invention may be 1.0-4.0GPa, for example, about 1.4GPa, 2.6GPa, 3.8GPa, about 3.5GPa, about 3.1GPa, about 2.7GPa, about 2.0GPa, about 3.3GPa, about 2.8GPa, about 1.9GPa, about 2.9GPa, about 3.2GPa, and the like.
Preparation method
In another aspect, the present invention is also directed to a method of preparing a polylactic acid-glycolic acid copolymer comprising the steps of: in the presence of a catalyst and an initiator, lactide copolymerization units and glycolide are subjected to copolymerization reaction to obtain a polylactic acid-glycolic acid copolymer.
Lactide copolymerization unit
The configuration of the lactide copolymerization unit determines the configuration of the polylactic acid segment. To incorporate a meso-polylactic acid segment in the copolymer, the lactide co-polymerized units may be meso-lactide, meso-lactide oligomers, or a combination of both.
The structure of meso-lactide is shown in formula (IV) below:
the amount of meso-lactide affects the proportion of polylactic acid segments in the copolymer, and further affects the properties (such as mechanical properties, heat resistance and the like) of the copolymer. Therefore, a polylactic acid-glycolic acid copolymer having excellent properties can be obtained with a suitable amount of meso-lactide, and the product properties may be adversely affected by an excessively high or low amount. In one embodiment, the weight of meso-lactide is between 0.5% and 25%, preferably between 0.5% and 20%, for example about 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3%, 4%, 5%, 10%, 15%, 18%, 20%, 22%, 24%, 24.5%, 25%, etc., of the total weight of meso-lactide and glycolide. The structure of the meso-lactide oligomer is shown in the following formula (IV):
in the formula (V), n represents the degree of polymerization of meso-lactide.
Too high molecular weight of meso-lactide oligomer may result in too high degree of polymerization of polylactic acid segment in the obtained copolymer, which is not favorable for uniform distribution of polylactic acid segment in the copolymer, and further brings adverse effect on product performance (such as toughness of material). The molecular weight of the meso-lactide oligomer is too high and the resulting copolymer will have poor thermal properties (e.g., a reduced thermal decomposition temperature) and be unfavorable for subsequent processing and use. In one embodiment, the number average molecular weight of the meso-lactide oligomer may be in the range of 100 to 2000, preferably 100 to 1000. In another embodiment, the degree of polymerization of the meso-lactide oligomer is in the range of 1 to 15, for example 1, 2,3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15. It will be understood that the meso-lactide oligomer is generally composed of homologues of different degrees of polymerization, and herein the degree of polymerization of the meso-lactide oligomer refers to its average degree of polymerization.
The amount of meso-lactide oligomer also affects the proportion of polylactic acid segments in the copolymer, and further affects the properties (such as mechanical properties, heat resistance and the like) of the copolymer. The use of a meso-lactide oligomer in an appropriate range contributes to obtaining a polylactic acid-glycolic acid copolymer having excellent properties. In one embodiment, the weight of meso-lactide oligomers is from 0.5% to 25%, preferably from 0.5% to 20%, for example about 1%, 2%, 5%, 10%, 20%, 25%, etc., of the total weight of meso-lactide and glycolide.
The amount of glycolide used affects the proportion of polyglycolic acid segments in the copolymer, and may affect the properties of the copolymer. Thus, either too high or too low a level of glycolide can adversely affect product performance. In one embodiment, the weight of glycolide ranges from about 75% to 99.5%, preferably from about 80% to 99.5%, for example, from about 75%, 75.5%, 76%, 77%, 78%, 79.5%, 80%, 80.5%, 85%, 90%, 95%, 97%, 98%, 98.5%, 99%, 99.5%, etc., of the total weight of copolymerized units of lactide and glycolide
Catalyst and process for preparing same
A catalyst may be used to catalyze the copolymerization of lactide interpolymerized units with glycolide. The addition of the catalyst can accelerate the reaction rate of ring-opening copolymerization, wherein the proper catalyst can effectively accelerate the reaction rate, the reaction is not influenced by the chemical properties of the catalyst, such as acidity, alkalinity, oxidizability, reducibility and the like, the occurrence of side reactions can be avoided, and the concentration of the product is improved.
Catalysts useful in the present invention include, but are not limited to: a tin-based catalyst, a zinc-based catalyst, a bismuth-based catalyst, or a combination thereof. The tin-based catalyst refers to a compound containing elemental tin, which may be an organotin compound or an inorganic tin compound. The zinc-based catalyst refers to a compound containing elemental zinc, which may be an organozinc compound or an inorganic zinc compound. The bismuth-based catalyst refers to a compound containing bismuth as an element, which may be an organic bismuth compound or an inorganic bismuth compound.
In one embodiment, the catalyst of the invention is selected from the group consisting of: stannous octoate, stannous chloride, zinc oxide, zinc chloride, zinc acetate, bismuth subsalicylate, bismuth trifluoromethanesulfonate, and combinations thereof.
The amount of catalyst used will affect the efficiency of the copolymerization to some extent and on the other hand the cost. In one embodiment, the weight of the catalyst is from 0.01% to 1%, preferably from 0.01% to 0.5%, more preferably from 0.01% to 0.15% of the weight of glycolide.
For a particular lactide copolymerization unit, the appropriate type and amount of catalyst can impart more excellent properties to the resulting copolymer.
In one embodiment, meso-lactide participates in the copolymerization reaction as a lactide copolymerization unit, and the catalyst is preferably bismuth subsalicylate, bismuth trifluoromethanesulfonate, or a combination thereof. In another embodiment, meso-lactide participates in the copolymerization as a co-polymerization unit of lactide, with the weight of catalyst being 0.01% to 0.15% of the mass of glycolide.
In one embodiment, the meso-lactide oligomer participates in the copolymerization as a lactide copolymerization unit, and the catalyst is preferably stannous octoate, zinc acetate, or a combination thereof. In another embodiment, meso-lactide participates in the copolymerization as a lactide copolymerization unit, with the weight of catalyst being 0.01% to 0.15% of the mass of glycolide.
Initiator
The initiator is used for starting the copolymerization reaction of the lactide copolymerization unit and the glycolide. In the present invention, the copolymerization reaction may be carried out without using an initiator to obtain a copolymer having a higher molecular weight.
The copolymerization reaction of the present invention may also be carried out in the presence of an initiator. Suitable initiators help to obtain the target copolymer. The present invention may employ alcoholic and/or phenolic initiators, including, for example, but not limited to: ethylene glycol, 1, 4-butanediol, 2, 3-butanediol, 1,3 propylene glycol, lauryl alcohol, benzyl alcohol, or combinations thereof. The amount of initiator is an important means for controlling the molecular weight of the copolymer obtained. The proper amount of the initiator can make the reaction smoothly proceed and make the polylactic acid-glycolic acid copolymer obtain a proper molecular weight range, thereby improving the performance. In one embodiment, the weight of the initiator is 0.01% to 5%, preferably 0.01% to 2% of the weight of the glycolide.
Copolymerization reaction
The proper reaction temperature of the copolymerization reaction helps the reaction to smoothly occur and has better reaction rate and yield of the target product. In one embodiment, the reaction temperature for the copolymerization reaction is from 150 to 230 ℃. Too high a reaction temperature increases energy consumption during the reaction, and may cause undesirable decomposition, resulting in a decrease in the yield of the target product; too low a reaction temperature is unfavorable for the reaction and the reaction rate is too low.
The reaction time of the copolymerization reaction is 0.05 to 8 hours. Too short reaction time can cause incomplete reaction, too low molecular weight of the product, reduced yield and no contribution to subsequent reaction; too long a reaction time increases energy consumption during the reaction and is liable to cause thermal degradation.
Under the environment of inert gas, the method is favorable for reducing side reaction and maintaining the activity of the catalyst. In one embodiment, the copolymerization reaction is carried out under an atmosphere of an inert gas. For example, the copolymerization reaction is carried out under an atmosphere of nitrogen and/or argon. In a particular embodiment, the copolymerization reactor is charged with nitrogen and/or argon at an absolute pressure greater than 101.3kPa.
During the copolymerization reaction, the good dispersion of the reaction raw materials (e.g., catalyst, initiator, lactide copolymerization units and glycolide) is advantageous for obtaining the desired product. Before and during the copolymerization, the reaction materials may be thoroughly mixed by stirring (e.g., mechanical stirring).
In order to avoid adverse effects of components in the air (such as water vapor, oxygen, etc.) on the copolymerization reaction, before the copolymerization reaction is carried out, a pressure reduction operation may be further carried out, and then an inert gas may be introduced to obtain an inert atmosphere. The pressure reduction may be performed by evacuation. In one embodiment, the reactor containing the reaction feed is evacuated to an absolute pressure in the reactor of from 10 to 2000Pa.
Advantageous effects
The racemic lactide used in the invention is a byproduct in the preparation of high-gloss pure lactide, and has large yield and low price. The meso-lactide or the oligomer thereof and the glycolide are polymerized to directly prepare the polylactic acid-glycolic acid copolymer with high molecular weight, thereby realizing the high value-added application of the meso-lactide. The toughness of the polyglycolic acid can be obviously improved by introducing the meso-polylactic acid chain segment into the polyglycolic acid chain segment, and the mechanical property can be regulated and controlled by adjusting the content of the meso-polylactic acid chain segment.
The polylactic acid-glycollic acid copolymer has the advantages of excellent performance, low cost and simple preparation process, is suitable for large-scale production and application, and has wide application prospect.
Examples
The present invention will be described in further detail with reference to specific examples.
It should be noted that the following examples are only given for clearly illustrating the technical solutions of the present invention, and are not intended to limit the present invention. Other variants and modifications will be apparent to those skilled in the art in light of the foregoing description, and it is not necessary or exhaustive for all embodiments to include such obvious variations or modifications as are within the scope of the invention. Unless otherwise indicated, both the instrumentation and reagent materials used herein are commercially available.
Material
Glycolide: jinan Dai handle bio-technology Ltd.
Meso-lactide and meso-lactide oligomers: zhejiang Haizhen biomaterial, inc.
Catalyst: sn (Oct) 2 、SnCl 2 、ZnO、ZnCl 2 、Zn(Ac) 2 Bismuth subsalicylate and Bi (OTf) 3 ) (ii) a Shanghai Aladdin Biotechnology Ltd.
Initiator: ethylene glycol, 1, 4-butanediol, 2, 3-butanediol, 1, 3-propanediol, lauryl alcohol, benzyl alcohol; shanghai Aladdin Biotechnology Ltd.
Solvent: hexafluoroisopropanol, shanghai Michelin Biotech, inc.
Preparation of
Samples of the preparation examples and comparative examples were prepared according to the following procedures, and the kinds and amounts of raw materials used for the preparation examples and comparative examples are shown in table 1 below.
Example 1
Weighing glycolide, a catalyst and meso-lactide according to a certain proportion, and adding the weighed materials into a polymerization reactor. The mixture is stirred and mixed evenly by a machine, and is vacuumized while stirring, the residual water in the reactor and the materials is removed by vacuuming for 1h under the condition of room temperature, and the absolute pressure is 200Pa when the materials are vacuumized. After the vacuum pumping is finished, argon is filled until the absolute pressure in the reactor is more than 101.3kPa. After completion of the aeration, the reactor was placed in an oil bath at 180 ℃ and subjected to polymerization reaction under an argon atmosphere for 2 hours to obtain a sample of example 1.
Examples 2 to 6
Referring to the preparation of example 1, samples of examples 2-6 and 12-13 were obtained, respectively.
Example 7
Weighing the lactide, the catalyst and the meso-lactide oligomer according to the proportion, and adding the weighed materials into a polymerization reactor. The mixture is stirred and mixed evenly by a machine, and is vacuumized while stirring, the residual water in the reactor and the materials is removed by vacuuming for 1h under the condition of room temperature, and the absolute pressure is 200Pa when the materials are vacuumized. After the completion of the vacuum pumping, argon gas was introduced until the absolute pressure in the reactor was more than 101.3kPa, and after the completion of the gas introduction, the reactor was placed in an oil bath pan at 180 ℃ to conduct a polymerization reaction for 2 hours under an argon atmosphere, thereby obtaining a sample of example 6.
Examples 7 to 10
Referring to the preparation of example 7, samples of examples 7 to 11 were obtained, respectively.
Examples 12 to 13
Samples of examples 12 to 13 were obtained respectively by taking the preparation of example 1 into consideration.
Comparative example 1
Glycolide and catalyst are weighed in proportion and added into a polymerization reactor. The materials are stirred and mixed evenly by a machine, and the mixture is vacuumized while being stirred for 1 hour at normal temperature to remove residual water in a reactor and the materials, wherein the absolute pressure is 200Pa when the mixture is vacuumized. After the vacuum pumping is finished, argon is filled until the absolute pressure in the reactor is more than 101.3kPa. After the completion of the aeration, the reactor was placed in an oil bath at 180 ℃ and subjected to polymerization reaction under an argon atmosphere for 2 hours to obtain the sample of comparative example 1, which was a PGA homopolymer.
Comparative example 2
Weighing glycolide, a catalyst and levorotatory lactide according to a certain proportion, and adding the weighed materials into a polymerization reactor. The materials are stirred and mixed evenly by a machine, and the mixture is vacuumized while being stirred for 1 hour at normal temperature to remove residual water in a reactor and the materials, wherein the absolute pressure is 200Pa when the mixture is vacuumized. And after the vacuum pumping is finished, argon is filled until the absolute pressure in the reactor is more than 101.3kPa. After the completion of the aeration, the reactor was placed in an oil bath at 180 ℃ and subjected to polymerization reaction for 2 hours under an argon atmosphere to obtain a sample of comparative example 2, the molecular structure of which comprises a levorotatory polylactic acid segment composed of levorotatory lactide structural units.
The kinds and amounts of raw materials used in the preparation examples and comparative examples are shown in table 1 below.
Comparative example 3
Weighing glycolide, a catalyst and dextro-lactide according to a certain proportion, and adding the materials into a polymerization reactor. The materials are stirred and mixed evenly by a machine, and the mixture is vacuumized while being stirred for 1 hour at normal temperature to remove residual water in a reactor and the materials, wherein the absolute pressure is 200Pa when the mixture is vacuumized. After the vacuum pumping is finished, argon is filled until the absolute pressure in the reactor is more than 101.3kPa. After the completion of the aeration, the reactor was placed in an oil bath at 180 ℃ and subjected to polymerization reaction for 2 hours under an argon atmosphere to obtain a sample of comparative example 2, the molecular structure of which contained a D-polylactic acid segment composed of L-lactide structural units.
TABLE 1
Testing
The examples and comparative examples were tested according to the following test methods, and the test results are shown in table 2.
Intrinsic viscosity test:
the intrinsic viscosity was measured in hexafluoroisopropanol at 25 ℃ using a fully automatic viscometer (Zhongwang technologies, hangzhou) with a black viscometer with an inner diameter of 0.51 mm.
Thermal decomposition temperature test:
the sample was heated from 50 ℃ to 600 ℃ at a temperature ramp rate of 10 ℃/min under a nitrogen atmosphere using a TGA55 thermogravimetric analyzer (TA, USA).
Melting point test:
the sample was heated from-20 ℃ to 250 ℃ at a heating rate of 10 ℃/min under nitrogen using a DSC25 differential scanning calorimeter (TA, USA).
And (3) testing a chemical structure:
a600 MHz nuclear magnetic resonance spectrometer produced by Brucker company of Switzerland is adopted, deuterated trifluoroacetic acid is used as a solvent, tetramethylsilane is used as an internal standard, and the test temperature is 25 ℃. And calculating the content of the lactide unit in the copolyester according to the area ratio of proton peaks on a methyl unit in a meso-glycolide unit based on the result of the nuclear magnetic resonance hydrogen spectrum.
And (3) testing tensile property:
and melting the sample at 245 ℃ for 3min by using a hot press, then carrying out hot pressing to form a film, wherein the thickness of the film is about 0.4mm, naturally cooling to room temperature, and taking out for later use. The dumbbell-shaped sample strips are manufactured by using a test cut-off knife, the length of the dumbbell-shaped sample strips is 50mm, the cross section width of the dumbbell-shaped sample strips is 3mm, the dumbbell-shaped sample strips are 0.4mm in thickness and 20mm in gauge length, the dumbbell-shaped sample strips are placed in a room-temperature environment for 48 hours after being cut to eliminate internal stress, a UTM2503 electronic universal test machine (Shenzhen Sansi longitudinal and transverse companies) is used for conducting uniaxial tensile test on the sample strips at 25 ℃ and 5mm/min, at least 3 sample strips are measured in parallel on each group of samples, and the breaking elongation and the Young modulus are obtained by averaging the results.
And (3) impact performance test:
melting a sample at 245 ℃ by using a micro injection molding machine, then preparing a test sample strip with the length of 80mm, the cross section width of 10mm and the thickness of 4mm by injection molding, and cutting a notch with the bottom radius of 0.25mm in the middle of the sample strip by using a milling cutter after the sample strip is taken out. And during injection molding, the mold temperature is 50 ℃, the injection molding pressure is 90MPa, the injection molding time is 15s, the pressure maintaining is 15MPa, and the pressure maintaining time is 10s. And (3) carrying out an impact strength test on the sample strips by using a cantilever beam type impact strength testing machine, testing 5 sample strips in parallel on each sample, and averaging the final results to obtain the notch impact strength.
TABLE 2
As is clear from the data in tables 1 and 2, both meso-lactide and meso-lactide oligomer can react with glycolide to obtain a polylactic acid-glycolic acid copolymer having excellent target performance.
The thermodynamic properties of the materials are significantly affected by the incorporation of a meso polylactic acid segment in PGA in examples 1-13, compared to comparative example 1. With the increase of the consumption of meso-lactide or meso-lactide oligomer, the higher the content of lactide structural fragments in the obtained copolymer, the more obvious the change of the properties of the obtained copolymer product than that of pure PGA.
In examples 5 and 8, when the content of lactide structural fragments in the copolymer was increased to about 20%, the melting point of the obtained copolymer was lowered by about 40 ℃ compared to that of pure PGA (comparative example 1). The difference between the thermal decomposition temperature and the melting point is increased, and the thermal processing temperature window is enlarged.
From examples 5 and 6, it can be seen that with further increase of lactide structure segments in the copolymer, the mechanical properties of the copolymer product of example 6 did not show significant improvement over example 5, but the thermal properties declined. From examples 10 and 11, it can be seen that with further increase in the molecular weight of meso lactide used, the thermal properties of the copolymer product obtained in example 6 are reduced compared to example 5.
From example 4 and examples 10 and 11, it is understood that in the copolymerization reaction between glycolide and meso-lactide as a reaction raw material, the bismuth-based catalyst has a higher catalytic effect than the tin-based catalyst, and a copolymer having a higher molecular weight and better performance can be produced.
In addition, it is understood from examples 1 to 9 that the mechanical properties (e.g., toughness) of the copolymer obtained by incorporating the meso-polylactic acid segment into PGA are significantly improved as compared with PGA. With the increase of the consumption of meso-lactide or meso-lactide oligomer, the content of lactide structural fragments in the obtained copolymer is higher, and with the increase of the content of meso-lactide, the improvement of the mechanical properties is more obvious.
As can be seen by comparing the examples with comparative examples 2-3, the use of meso-lactide or meso-lactide oligomer provides a significantly better toughening effect on the resulting copolymer than levo-lactide and dextro-lactide.
The above description is only an exemplary embodiment of the present invention, and is not intended to limit the scope of the present invention, which is defined by the claims of the present invention, and all equivalent modifications made by the present invention, or directly or indirectly applied to other related fields.
Claims (10)
1. A polylactic acid-glycolic acid copolymer comprising: a structural unit A represented by the formula (I), and a structural unit B represented by the formula (II),
wherein, the structural units are connected through ester bonds.
2. The polylactic acid-glycolic acid copolymer according to claim 1,
the content of the structural unit a is 0.5 to 25% by weight, preferably 0.5 to 20% by weight, based on the weight of the polylactic acid-glycolic acid copolymer; and/or
The content of the structural unit B is 75 to 99.5% by weight, preferably 80 to 99.5% by weight, based on the weight of the polylactic acid-glycolic acid copolymer.
3. The polylactic acid-glycolic acid copolymer according to claim 1 or 2, wherein,
the inherent viscosity of the polylactic acid-glycolic acid copolymer is 0.6-1.50dL/g, preferably 1.0-1.5dL/g; and/or
The thermal decomposition temperature of the polylactic acid-glycolic acid copolymer is 200-260 ℃; preferably 230 to 260 ℃; and/or
The melting point of the polylactic acid-glycolic acid copolymer is 150-225 ℃; preferably 180-225 deg.c.
4. A method for preparing the polylactic acid-glycolic acid copolymer according to any one of claims 1 to 3, comprising the steps of:
copolymerizing lactide copolymerization units with glycolide in the presence of a catalyst to obtain the polylactic acid-glycolic acid copolymer, wherein,
the lactide copolymerization unit is selected from: meso-lactide, meso-lactide oligomers, and combinations thereof.
5. The method of claim 4, wherein,
the weight of the lactide copolymerization unit is 0.5-25%, preferably 0.5-20% of the total weight of the lactide copolymerization unit and the glycolide.
6. The method of claim 4 or 5, wherein,
the meso-lactide oligomer has a number average molecular weight of 100 to 2000, preferably 100 to 1000; and/or
The polymerization degree of the meso-lactide oligomer is 1-15.
7. The method of any one of claims 4-6, wherein,
the catalyst is selected from: tin-based catalysts, zinc-based catalysts, bismuth-based catalysts and combinations thereof, preferably selected from: stannous octoate, stannous chloride, zinc oxide, zinc chloride, zinc acetate, bismuth subsalicylate, bismuth trifluoromethanesulfonate, and combinations thereof; and/or
The weight of the catalyst is 0.01-1%, preferably 0.01-0.5%, more preferably 0.01-0.15% of the weight of the glycolide.
8. The method of any one of claims 4-7, wherein,
the copolymerization is also carried out in the presence of an initiator, wherein,
the initiator is selected from: alcohol initiators, phenolic initiators and combinations thereof, preferably selected from: ethylene glycol, 1, 4-butanediol, 2, 3-butanediol, 1, 3-propanediol, lauryl alcohol, benzyl alcohol, and combinations thereof; and/or
The weight of the initiator is 0.01-5%, preferably 0.01-2% of the weight of the glycolide.
9. The method of any one of claims 4-8, wherein,
the reaction temperature of the copolymerization reaction is 150-230 ℃; and/or
The reaction time of the copolymerization reaction is 0.05 to 8 hours.
10. The method of any one of claims 4-9, wherein,
before the copolymerization reaction, the method also comprises a decompression operation.
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