CN116253866A - Polyglycolide copolymer and preparation method thereof - Google Patents

Abstract

The invention provides a polyglycolide copolymer and a preparation method thereof. The method comprises the following steps: (1) mixing glycolide, a comonomer, Catalyst and the optional first auxiliary agent added; (2) making the material obtained in step (1) react under an inert gas atmosphere, 120-210 ° C, and a pressure higher than normal pressure, during which the second auxiliary agent is optionally added (3) the material obtained in step (2) is devolatilized. The method of the invention has the advantages of improving the utilization rate of raw materials, reducing material defects, increasing the molecular weight of the product, simplifying the operation process, and the like, and can prepare polyglycolide copolymer products with high molecular weight and no appearance defects.

Description

Polyglycolide copolymer and preparation method thereof

Technical Field

The invention belongs to the field of polyglycolide, and in particular relates to a polyglycolide copolymer and a preparation method thereof.

Background Art

Polyglycolide (PGA, also known as polyglycolic acid) is a synthetic polymer material with good biodegradability and biocompatibility, and is a thermoplastic polymer. The advantages of this polymer material are: (1) Good performance: high molecular weight PGA has excellent mechanical properties, high crystallinity, strong rigidity, and good mechanical properties. Generally, the higher the molecular weight, the better the mechanical properties; it has excellent gas barrier properties and is expected to replace traditional petroleum-based plastics in food packaging, disposable daily necessities, agriculture, medicine and other fields; (2) Easy to degrade: Compared with other biodegradable materials, such as polybutylene terephthalate-adipate (PBAT), polybutylene succinate (PBS), polylactic acid (PLA), etc., PGA does not require special or harsh conditions for degradation, and can be degraded into water and carbon dioxide in the natural environment that are harmless to humans, animals, plants and the natural environment.

The disadvantages of PGA obtained by homopolymerization of glycolic acid or glycolide are: (1) The melting temperature of high molecular weight PGA homopolymer is high (about 220°C), which is very close to the decomposition temperature, making it very easy to undergo thermal degradation during thermal processing, thereby damaging the mechanical properties of the material; (2) Although PGA homopolymer has strong rigidity, it has poor toughness; (3) PGA homopolymer degrades too quickly and often cannot meet the shelf life requirements. These disadvantages limit the widespread application of this material.

The introduction of comonomers can improve some of the above-mentioned problems of PGA to a certain extent, but the molecular weight of existing copolymer products is generally not high, the types of comonomers are relatively single (mainly copolymerized with lactic acid or lactide to obtain PLGA), and the copolymerization ratio of glycolic acid or glycolide in the copolymer is low, which cannot fully utilize the excellent properties of PGA itself, and the application range is relatively narrow, mainly concentrated in the field of biomedicine.

In the existing polymerization technology for preparing PGA, the method of condensation polymerization of glycolic acid is often difficult to obtain a product with a higher molecular weight. Even if the method of glycolide ring-opening bulk polymerization, which is recognized to have a higher reaction efficiency, is adopted, the increase in molecular weight is limited. If the molecular weight of the polymer needs to be further increased, solid phase polymerization is usually used. In this way, in addition to the original polymerization device and conditions, a new reaction device needs to be set up, and the process flow is relatively cumbersome. The method for preparing copolymers is basically the same as that for preparing PGA. In order to obtain high molecular weight copolymers, it is usually necessary to set up a new reaction device, such as transferring to an ultrasonic reactor for ultrasonic reaction, which is cumbersome.

Therefore, there is a need in the art for a method for preparing a high molecular weight polyglycolide copolymer that is simple to operate.

Summary of the invention

In view of the problems existing in the prior art, the present invention provides a polyglycolide copolymer with glycolide as the main raw material and a preparation method thereof. The present invention controls the staged change of the reaction temperature, the pressure and atmosphere of the reaction system, greatly increases the molecular weight, improves the utilization rate of raw materials, is conducive to ensuring a relatively complete monomer reaction, controlling the monomer ratio of the product, reducing material defects, and simplifying the operation process, thereby obtaining a polyglycolide copolymer product with a high molecular weight and no appearance defects.

Specifically, the present invention provides a method for preparing a polyglycolide copolymer, the method comprising the following steps:

(1) mixing glycolide, a comonomer, a catalyst and an optionally added first auxiliary agent in an inert gas atmosphere at 40 to 100° C. and a pressure higher than normal pressure;

(2) reacting the material obtained in step (1) in an inert gas atmosphere at 120 to 210° C. and a pressure higher than normal pressure, and optionally adding a second auxiliary agent during the reaction, to obtain a first reaction product;

Optionally, step (2) further comprises: reacting the first reaction product in an inert gas atmosphere at 150-225° C. and a pressure higher than normal pressure, during which a third auxiliary agent is optionally added to obtain a second reaction product;

(3) Devolatilizing the material obtained in step (2).

In one or more embodiments, the comonomer is selected from one or more of aliphatic cyclic ethers, aliphatic lactones, and aliphatic cyclic lactides other than glycolide, for example, selected from one or more of propiolactone, caprolactone, valerolactone, butyrolactone, enantholactone, octanolactone, nonanolactone, decanolactone, lactide, trimethylene carbonate, ethylene oxide, propylene oxide, methylpropylene oxide, oxetane, 1,2-butylene oxide, tetrahydrofuran, dioxolane, dioxane, and substituted ethylene oxide.

In one or more embodiments, the comonomer is selected from one or more of ε-caprolactone, β-butyrolactone, DL-lactide, L-lactide, trimethylene carbonate, ethylene oxide, propylene oxide, and dioxane.

In one or more embodiments, the catalyst is selected from one or more of tin salts, titanium salts, magnesium salts, aluminum salts, calcium salts, iron salts, manganese salts, zinc salts, organotin compounds, organotitanium compounds, organomagnesium compounds, organoaluminum compounds, organocalcium compounds, organoiron compounds, organomanganese compounds, and organozinc compounds.

In one or more embodiments, the first auxiliary agent includes one or more selected from the group consisting of an initiator, a thermal stabilizer, an antioxidant, and an anti-hydrolysis agent.

In one or more embodiments, the second auxiliary agent includes one or more selected from the group consisting of an initiator, a thermal stabilizer, an antioxidant, and an anti-hydrolysis agent.

In one or more embodiments, the initiator is selected from one or more of aliphatic carboxylic acids having a carbon number of 12 or less, aliphatic anhydrides, natural amino acids, natural amino acid oligomers, aliphatic alcohols, and aliphatic amines.

In one or more embodiments, the third auxiliary agent includes one or more selected from a crosslinking agent, a heat stabilizer, an antioxidant, and an anti-hydrolysis agent.

In one or more embodiments, the crosslinking agent is selected from one or more of aliphatic dicarboxylic acids having a carbon number of 12 or less, aliphatic polycarboxylic acids, anhydrides of aliphatic dicarboxylic acids and aliphatic polycarboxylic acids, natural amino acid oligomers, aliphatic diols, aliphatic polyols, aliphatic diamines and aliphatic polyamines.

In one or more embodiments, the weight fraction of glycolide in the total weight of monomers is ≥50%.

In one or more embodiments, the amount of catalyst used is 0.001% to 0.1% by weight of the total monomers.

In one or more embodiments, no initiator is added in step (1).

In one or more embodiments, an initiator is added in step (1), and the amount of the initiator is 0.01% to 5%, preferably 0.1% to 2%, based on the total weight of the monomers.

In one or more embodiments, no cross-linking agent is added during the preparation of the second reaction product in step (2).

In one or more embodiments, a crosslinking agent is added during the preparation of the second reaction product in step (2), and the amount of the crosslinking agent is 0.01 to 3%, preferably 0.1 to 2%, of the total weight of the monomers.

In one or more embodiments, the mixing temperature of step (1) is 50-100°C.

In one or more embodiments, the mixing time of step (1) is 1 to 30 min, preferably 5 to 30 min.

In one or more embodiments, step (1) is carried out at 0.12 to 20 MPa, preferably at 0.15 to 10 MPa.

In one or more embodiments, the reaction temperature for preparing the first reaction product in step (2) is 140-200°C.

In one or more embodiments, the reaction time for preparing the first reaction product in step (2) is 0.5 to 24 hours, preferably 2 to 20 hours.

In one or more embodiments, the preparation of the first reaction product in step (2) is carried out at 0.12 to 20 MPa, preferably at 0.15 to 10 MPa.

In one or more embodiments, the reaction temperature for preparing the second reaction product in step (2) is 180-220°C.

In one or more embodiments, the reaction time for preparing the second reaction product in step (2) is 0.1 h to 5 h, preferably 0.15 to 3.5 h.

In one or more embodiments, the preparation of the second reaction product in step (2) is carried out at 0.12 to 20 MPa, preferably at 0.15 to 10 MPa.

In one or more embodiments, the reaction temperature for preparing the second reaction product in step (2) is higher than the reaction temperature for preparing the first reaction product in step (2).

In one or more embodiments, the reaction temperature for preparing the second reaction product in step (2) is at least 20° C. higher than the reaction temperature for preparing the first reaction product in step (2).

In one or more embodiments, step (3) comprises devolatilizing the material obtained in step (2) at 0.5 to 100 kPa and 150 to 190°C.

In one or more embodiments, the devolatilization time is 10 to 60 minutes.

The present invention also provides a polyglycolide copolymer prepared by the method described in any embodiment of the present invention.

The present invention also provides an article comprising the polyglycolide copolymer described in any embodiment herein.

DETAILED DESCRIPTION

In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

In this article, all features such as values, quantities, contents and concentrations defined in the form of numerical ranges or percentage ranges are only for brevity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be considered to have included and specifically disclosed all possible secondary ranges and individual values within the range (including integers and fractions).

In this document, in order to make the description concise, not all possible combinations of various technical features in various embodiments or examples are described. Therefore, as long as there is no contradiction in the combination of these technical features, the various technical features in various embodiments or examples can be combined arbitrarily, and all possible combinations should be considered to be within the scope of this specification.

The present invention provides a method for preparing a high molecular weight polyglycolide copolymer with simple operation. The present invention can achieve a significant increase in molecular weight and raw material utilization by controlling the staged change of reaction temperature, the system pressure and atmosphere of the reaction, without replacing or adding new reaction equipment in the middle of the reaction, which is conducive to ensuring a relatively complete monomer reaction, controlling the product monomer ratio, reducing material defects, simplifying the operation process, and thus obtaining a high molecular weight, appearance defect-free polyglycolide copolymer product.

The method for preparing polyglycolide copolymer of the present invention comprises the following steps:

(1) mixing glycolide, a comonomer, a catalyst and an optionally added first auxiliary agent in an inert gas atmosphere at 40 to 100° C. and a pressure higher than normal pressure;

(2) reacting the material obtained in step (1) in an inert gas atmosphere at 120 to 210° C. and a pressure higher than normal pressure, and optionally adding a second auxiliary agent during the reaction, to obtain a first reaction product;

Optionally, step (2) may further include: reacting the first reaction product in an inert gas atmosphere at 150-225° C. and a pressure higher than normal pressure, during which a third auxiliary agent is optionally added to obtain a second reaction product;

(3) Devolatilizing the material obtained in step (2).

In the present invention, the step of preparing the first reaction product in step (2) is referred to as step (2-1), and the step of preparing the second reaction product in step (2) is referred to as step (2-2). In the present invention, step (2-2) is optionally or preferably included. When the method of the present invention includes step (2-2), the material obtained in step (2-2) (i.e., the second reaction product) is devolatilized in step (3). When the method of the present invention does not include step (2-2), the material obtained in step (2-1) (i.e., the first reaction product) is devolatilized in step (3).

In some embodiments, the method for preparing a polyglycolide copolymer of the present invention comprises the following steps:

(1) mixing glycolide, a comonomer, a catalyst, and an optionally added first auxiliary agent under an inert gas atmosphere, a pressurized condition, and a first temperature;

(2-1) reacting the material obtained in step (1) under an inert gas atmosphere, under pressure, and at a second temperature, and optionally adding a second auxiliary agent;

(2-2) reacting the material obtained in step (2-1) under an inert gas atmosphere, under pressure, and at a third temperature, and optionally adding a third auxiliary agent;

(3) Devolatilize the material obtained in step (2-2).

In the present invention, inert gas refers to an atmosphere that does not react with the materials in the system, such as nitrogen, rare gases, etc. In some embodiments, steps (1), (2-1) and (2-2) are performed in a nitrogen atmosphere. An inert gas environment can effectively prevent oxygen from damaging the monomer raw materials and the polymer product during the reaction.

In the present invention, the pressurized condition refers to a pressure higher than normal pressure (i.e., one atmosphere). Preferably, the pressurized condition is 0.12 to 20 MPa, such as 0.15 MPa, 0.2 MPa, 0.5 MPa, 3 MPa, 5 MPa, 10 MPa. The present invention has found that carrying out steps (1), (2-1), and (2-2) under pressurized conditions, especially under the aforementioned pressure conditions, can ensure that the comonomer reaction is relatively complete, increase the molecular weight, and avoid appearance defects such as bubbles in the product.

The glycolide suitable for use in the present invention can be obtained through the route of methyl glycolate → glycolic acid → polyglycolic acid oligomer → glycolide, or through the route of methyl glycolate → polyglycolic acid oligomer → glycolide.

γ-丁内酯

等，戊内酯包括γ-戊内酯

δ-戊内酯

等，己内酯包括γ-己内酯

δ-己内酯

ε-己内酯

等，庚内酯包括γ-庚内酯

δ-庚内酯

ε-庚内酯

ζ-庚内酯

等，辛内酯包括γ-辛内酯

δ-辛内酯

等，壬内酯包括等γ-壬内酯

δ-壬内酯

等，癸内酯包括γ-癸内酯

δ-癸内酯

ε-癸内酯

等，丙交酯包括L-丙交酯

DL-丙交酯

等。脂肪族环醚的实例包括但不限于环氧乙烷、环氧丙烷、甲基环氧丙烷、氧杂环丁烷、1,2-环氧丁烷、四氢呋喃、二氧戊环、二氧六环以及含取代基的环氧乙烷中的一种或多种。含取代基的环氧乙烷可以是被1到4个(例如1个或2个)C1-C4烷基取代的环氧乙烷，例如含取代基的环氧乙烷可以是1,2-二甲基环氧乙烷。本发明中，脂肪族化合物是指不含芳香环的化合物。共聚单体优选为可生物降解材料的单体，保证形成的共聚材料依然生物可降解。在一些实施方案中，共聚单体选自ε-己内酯、β-丁内酯、DL-丙交酯、L-丙交酯、三亚甲基碳酸酯、环氧乙烷、环氧丙烷和二氧六环中的一种或多种。In the present invention, the comonomer is a monomer of a cyclic ester structure, which ensures that the reaction is a single bulk melt ring-opening polymerization, and the reaction principle has unity and consistency, which is easy to control. The comonomer suitable for the present invention can be one or more selected from aliphatic cyclic ethers, aliphatic lactones and aliphatic cyclic lactides other than glycolide. Examples of aliphatic lactones include but are not limited to propiolactone, caprolactone, valerolactone, butyrolactone, enantholactone, octanolactone, nonanolactone, decanolactone, trimethylene carbonate, etc. Examples of aliphatic cyclic lactides include but are not limited to lactide, etc. It should be understood that, unless otherwise specified, the lactones and lactides described herein cover various isomers (including configurational isomers and conformational isomers) that may exist in the form of the lactone or lactide, for example, butyrolactone includes β-butyrolactone

γ-Butyrolactone

etc., valerolactones include γ-valerolactone

δ-Valerolactone

etc. Caprolactones include γ-caprolactone

δ-Caprolactone

ε-Caprolactone

etc., enantholactones include γ-enantholactone

δ-Heptanolide

ε-Heptanolide

ζ-Heptanolide

etc., octalactones include γ-octalactone

δ-Octyl lactone

etc. Nonanolactones include γ-nonanolactone

δ-Nonanolactone

etc., decanoic acid includes γ-decanoic acid

δ-Decalactone

ε-Decalactone

etc., lactides include L-lactide

DL-Lactide

Etc. Examples of aliphatic cyclic ethers include, but are not limited to, one or more of ethylene oxide, propylene oxide, methyl propylene oxide, oxetane, 1,2-butylene oxide, tetrahydrofuran, dioxolane, dioxane, and substituted ethylene oxide. Substituted ethylene oxide may be ethylene oxide substituted by 1 to 4 (e.g., 1 or 2) C1-C4 alkyl groups, for example, substituted ethylene oxide may be 1,2-dimethyl ethylene oxide. In the present invention, aliphatic compounds refer to compounds that do not contain aromatic rings. Comonomers are preferably monomers of biodegradable materials to ensure that the formed copolymer material is still biodegradable. In some embodiments, the comonomer is selected from one or more of ε-caprolactone, β-butyrolactone, DL-lactide, L-lactide, trimethylene carbonate, ethylene oxide, propylene oxide, and dioxane.

In some embodiments, the comonomer is selected from one or more of ε-caprolactone, β-butyrolactone, DL-lactide and L-lactide. In some embodiments, the comonomer is ε-caprolactone, β-butyrolactone, DL-lactide or L-lactide. The present invention introduces comonomers to improve the mechanical properties of PGA homopolymer resin, reduce the melting temperature to increase the difference between the melting temperature and the thermal decomposition temperature, expand the processing window, and improve the processing performance of the product; the mechanical properties and degradation time of the material are adjusted by selecting the type of comonomer and controlling the proportion.

In some embodiments, the comonomer includes monomers with a lower boiling point (e.g., <120°C or <100°C), such as ε-caprolactone, β-butyrolactone, etc., and optionally may also include monomers with a higher boiling point (e.g., ≥120°C or ≥100°C), such as DL-lactide, L-lactide, etc. In some embodiments, the comonomer includes one or two selected from ε-caprolactone and β-butyrolactone, and optionally one or two selected from DL-lactide and L-lactide. For example, the comonomer may be ε-caprolactone, or β-butyrolactone, or ε-caprolactone and β-butyrolactone, or ε-caprolactone and DL-lactide. The present invention is particularly suitable for situations where the comonomer includes monomers with a lower boiling point, can improve the utilization rate of raw materials, is conducive to ensuring that the monomer reaction is relatively complete, controls the monomer ratio of the product, improves the molecular weight of the product, and avoids defects such as pores in the material.

In a preferred embodiment, the mass fraction of glycolide in the total mass of the monomer (including glycolide and comonomer) is ≥50%, such as 56%, 60%, 70%, 80%, 98%. The present invention controls the copolymerization ratio of glycolide to be above 50%, which is beneficial to retaining the original excellent properties of polyglycolide.

The catalyst suitable for the present invention can be a catalyst commonly used in the art for catalyzing glycolide polymers, including but not limited to one or more selected from tin salts, titanium salts, magnesium salts, aluminum salts, calcium salts, iron salts, manganese salts, zinc salts, organic tin compounds, organic titanium compounds, organic magnesium compounds, organic aluminum compounds, organic calcium compounds, organic iron compounds, organic manganese compounds and organic zinc compounds. In the present invention, metal salts refer to inorganic salts containing the metal, and organic metal compounds refer to organic compounds containing the metal. Examples of catalysts include stannous chloride, stannous isooctanoate, tetrabutyl titanate, etc. The amount of the catalyst is 0.001% to 0.1% of the total mass of the monomer, such as 0.01%, 0.02%, 0.1%.

The components involved in the polymerization reaction may include an initiator and a cross-linking agent, or may not include an initiator and a cross-linking agent. Common additives such as heat stabilizers, antioxidants, and anti-hydrolysis agents may be added during the polymerization reaction, or may not be added. The first auxiliary agent optionally added in step (1) may include one or more selected from initiators, heat stabilizers, antioxidants, and anti-hydrolysis agents. The second auxiliary agent optionally added in step (2-1) may include one or more selected from initiators, heat stabilizers, antioxidants, and anti-hydrolysis agents. The first auxiliary agent and the second auxiliary agent may be the same or different. The third auxiliary agent optionally added in step (2-2) may include one or more selected from cross-linking agents, heat stabilizers, antioxidants, and anti-hydrolysis agents. In some embodiments, an initiator is optionally added in step (1), no auxiliary agent is added in step (2-1), and a cross-linking agent is optionally added in step (2-2).

The initiator suitable for the present invention is preferably selected from one or more of aliphatic carboxylic acids, aliphatic anhydrides, natural amino acids, natural amino acid oligomers, aliphatic alcohols and aliphatic amines. The carbon number of the initiator is preferably less than or equal to 12. Examples of initiators include glutaric acid, glycerol, 2-hydroxymethyl-1,3-propanediol, inositol, aspartic acid oligomers, etc. In the embodiment of adding the initiator, the amount of the initiator is 0.01% to 5% of the total mass of the monomer, for example 0.1%, 0.5%, 1%, 1.8%, 2%. The initiator can be added to the reaction system in step (1).

The crosslinking agent suitable for the present invention is preferably selected from one or more of anhydrides of aliphatic dicarboxylic acids, aliphatic polycarboxylic acids, aliphatic dicarboxylic acids and aliphatic polycarboxylic acids, natural amino acid oligomers, aliphatic diols, aliphatic polyols, aliphatic diamines and aliphatic polyamines. In the present invention, polyvalent refers to greater than or equal to trivalent. The anhydride can be an anhydride formed by the same carboxylic acid, or an anhydride formed by different carboxylic acids, for example, an anhydride formed by two different dicarboxylic acids, an anhydride formed by two different polycarboxylic acids, an anhydride formed by a dicarboxylic acid and a polycarboxylic acid, etc. The carbon number of the crosslinking agent is preferably less than or equal to 12. Examples of crosslinking agents include 1,2,7,8-octanedetrol, etc. In the embodiment of adding a crosslinking agent, the amount of the crosslinking agent is 0.01% to 3% of the total mass of the monomer, for example, 0.1%, 0.5%, 1%, 2%. The crosslinking agent can be added to the reaction system in step (2-2).

The step (1) of the method for preparing polyglycolide copolymer of the present invention is to mix glycolide, comonomer, catalyst and optional first auxiliary agent uniformly under inert gas atmosphere, pressurized conditions and first temperature. In the present invention, the first auxiliary agent refers to an additive preferably added at the beginning of the reaction, including but not limited to one or more selected from initiator, heat stabilizer, antioxidant and anti-hydrolysis agent. In the present invention, the first temperature is 40-100°C, such as 50°C, 60°C, 80°C, 90°C, 100°C. The mixing time of step (1) can be 1-30min, such as 5min, 10min, 20min, 30min. Before performing step (1), the material can be added to the reaction device, and the container in the reaction device can be replaced with inert gas and pressurized. Step (1) can be carried out under stirring. After step (1), the material is fully melted and mixed.

Step (2-1) is to polymerize the material under an inert gas atmosphere, pressurized conditions, and a second temperature. In the present invention, the second temperature is 120 to 210°C, for example, 120 to 180°C, 140 to 180°C, 140°C, 150°C, 170°C, 180°C, 200°C. The reaction time of step (2-1) can be 0.5 to 24h, for example, 2h, 6h, 6h, 12h, 20h. A second auxiliary agent can be optionally added in step (2-1). The polymerization process of step (2-1) is maintained for a sufficient time to avoid the product from being scorched in the subsequent polymerization process.

Step (2-2) is to further polymerize the material under an inert gas atmosphere, pressurized conditions, and a third temperature. In the present invention, the third temperature is 150 to 225°C, such as 180°C, 190°C, 200°C, and 220°C. The reaction time of step (2-2) can be 0.1 to 5h, such as 0.15h, 10min, 0.5h, 1h, 3h, and 3.5h. A third auxiliary agent can be optionally added in step (2-2). In the present invention, the third auxiliary agent refers to an additive preferably added near the end of the reaction, including but not limited to one or more selected from a cross-linking agent, a thermal stabilizer, an antioxidant, and an anti-hydrolysis agent. In some embodiments, one or more cross-linking agents are added in step (2-2) to adjust the molecular structure of the polymer. The reaction temperature of step (2-2) is preferably higher than the reaction temperature of step (2-1). More preferably, the reaction temperature of step (2-2) is at least 20°C higher than the reaction temperature of step (2-1). Further polymerization in step (2-2) and controlling the reaction temperature of step (2-2) to be higher than the reaction temperature of step (2-1) are beneficial to increasing the molecular weight of the polyglycolide copolymer.

Step (3) is to devolatilize the product. The devolatilization is carried out under reduced pressure, preferably at a pressure of 0.5 to 100 kPa, such as 0.5 kPa, 2 kPa, 10 kPa, and 50 kPa. The devolatilization temperature (fourth temperature) is preferably 150 to 190°C, such as 150°C, 160°C, and 180°C. The devolatilization time can be 10 to 60 min, such as 10 min, 30 min, and 50 min. After step (2) is completed, the temperature can be adjusted to the fourth temperature section, the device can be depressurized, and the decompression state can be maintained for a period of time to devolatilize. After the devolatilization is completed, the product can be extruded and granulated.

The reaction device applicable to the present invention can be any reactor with stirring blades or spiral belt blades, such as vertical, horizontal, bottled, tubular, barrel-shaped, etc., or a screw extruder with various capacities and aspect ratios, or a reaction device composed of multiple scraper reactors. In a preferred embodiment, steps (1), (2-1), (2-2) and (3) of the present invention are carried out in the same reaction device.

In some embodiments, the method for preparing a polyglycolide copolymer of the present invention comprises: (a) adding glycolide, a comonomer, a catalyst and an optional first auxiliary agent (such as an initiator) into a reaction device; (b) replacing the air atmosphere in the reactor with an inert gas (such as nitrogen) and pressurizing it; (c) heating to a first temperature and maintaining the temperature for a period of time to allow the raw materials to be fully melted and mixed; (d) heating to a second temperature and maintaining the temperature for a period of time to allow the raw materials to fully react; (e) heating to a third temperature to further polymerize the product of the second temperature section, during which a third auxiliary agent (such as a cross-linking agent) can be added to adjust the molecular structure of the polymer; (f) adjusting the temperature to a fourth temperature to depressurize the device and maintain the decompression state for a period of time to devolatilize; and (g) extruding the product into granules. The pressure in the reaction device is preferably 0.1-10 MPa; the first temperature is preferably 40-100°C, and the maintenance time can be 1-30 min; the second temperature is preferably 120-210°C, for example 120-180°C, and the maintenance time can be 0.5-24 h; the third temperature is preferably 150-225°C, and can be maintained for 0.2-5 h; the fourth temperature is preferably 150-190°C, and the pressure can be reduced to 0.5-100 kPa, and the maintenance time can be 10-60 min.

The polyglycolide copolymer product prepared by the preparation method of the present invention has the advantages of high molecular weight, no appearance defects, adjustable mechanical properties and degradation time, good processing performance (large processing window), etc. In some embodiments, the weight average molecular weight (Mw) of the polyglycolide copolymer prepared by the present invention can reach 60,000 or more, for example, 67,000 or more, 80,000 or more, 90,000 or more, 100,000 or more, 110,000 or more, 120,000 or more, or 160,000 or more.

Therefore, the present invention also includes the polyglycolide copolymer prepared by the preparation method of the present invention and its products. The present invention includes downstream materials containing the polyglycolide copolymer of the present invention, such as packaging boxes, boxes, bags, injection molded small daily necessities (such as toothbrush handles, pen shells, car interiors), etc.

The present invention has the following advantages:

(1) Compared with the conventional product obtained by a single temperature stage reaction, the molecular weight of the product obtained by the multi-stage temperature increase reaction of the present invention is significantly improved. Compared with other methods for synthesizing polyglycolide copolymers to increase molecular weight, such as ultrasonic synthesis and solid phase polymerization, the present invention does not require the replacement of equipment midway or the use of other energy supply methods other than heating (such as ultrasound), but instead uses a catalyst combined with a specially designed multi-stage temperature increase, pressurized reaction and inert gas protection preparation process, which not only achieves the preparation of high molecular weight polyglycolide copolymers, but also has the advantages of simple operation and low reaction temperature.

(2) The present invention adopts a lower reaction temperature, which reduces energy consumption, reduces the decomposition, oxidation and coloring of the material during the polymerization process, avoids the volatilization loss of comonomers (especially low-boiling point comonomers, such as ε-caprolactone, β-butyrolactone, etc.) during the reaction process, improves the utilization rate of raw materials, and is conducive to ensuring a relatively complete monomer reaction, controlling the monomer ratio of the product, and avoiding defects such as pores in the material. The presence of pores in the product material will damage the mechanical properties of the material and even make it obviously crisp on a macroscopic scale. Copolymerization reduces the melting point of the material, so the copolymer material can melt at a relatively low third temperature.

(3) The present invention adopts a staged heating method, especially providing a temperature condition near or above the melting point of the copolymer material, so that it can further react and increase the molecular weight of the product. The boundaries between the stages are clear, and each stage is kept for a sufficient time to allow the reactants in that stage to fully react. If the boundaries between the stages are blurred and the temperature is raised too quickly, it will cause uneven heat transfer and some materials will be burnt. The reaction of the present invention can be carried out in the same reaction device, which can simplify the operation process compared with the prior art.

(4) The present invention adopts a pressurized reaction, which can make different reaction components in a liquid state as much as possible, which is beneficial to control the ratio of components participating in the reaction, improve the utilization rate of raw materials, and reduce material defects caused by the gasification of reactants. Compared with the prior art, it can better serve the copolymerization process of glycolide and low-boiling point monomers.

(5) The preparation method of the present invention has a wide range of applications and is suitable for copolymerization with glycolide as the main material and various aliphatic short carbon chain cyclic esters or lactides. It can retain the original characteristics of PGA to a certain extent without affecting the biodegradability of the copolymer material. By adjusting the monomer copolymerization ratio, the degradation rate of the material can be adjusted; it can also improve the toughness and processing performance of the material. The decomposition temperature of the polymer formed by the copolymer monomer itself is higher than or similar to that of PGA. Therefore, the decomposition temperature of the copolymer material is higher than or similar to that of PGA. At the same time, the melting temperature of the copolymer material is lower than that of PGA, the difference between the melting temperature and the decomposition temperature becomes larger, and the processing window becomes larger; it can also enrich the types of PGA copolymer materials and expand its application range.

The present invention will be described below in the form of specific examples. It should be understood that these examples are merely illustrative and are not intended to limit the scope of the present invention. The methods, reagents and materials used in the examples are, unless otherwise stated, conventional methods, reagents and materials in the art. The raw material compounds in the preparation examples can all be purchased through commercial routes.

Example 1

60g glycolide, 40g ε-caprolactone, 20mg stannous chloride and 1g glutaric acid were added to the reactor. After replacing the gas in the reactor with nitrogen, the reactor was filled with nitrogen and pressurized to 0.5MPa. The temperature was raised to 60℃ while stirring, and maintained for 20min. The temperature was further raised to 140℃ and maintained for 6h. The temperature was raised to 180℃ again, maintained for 3h, 0.1g of 1,2,7,8-octanedetrol was added, the reaction continued for 30min, the temperature was lowered to 160℃, the pressure was reduced to 50kPa and maintained for 30min, and the product was taken out and cooled and collected. There were no obvious condensed droplets on the reactor wall, indicating that the ε-caprolactone reaction was relatively complete; the product had no bubbles. The weight average molecular weight of the product was 83320, and the melting temperature was 143℃. The yield tensile strength was 60.9MPa, the flexural strength was 82.6MPa, the flexural modulus was 2.5GPa, and the elongation at break was 185%.

Example 2

70g glycolide, 30g β-butyrolactone, 100mg stannous isooctanoate, and 0.1g propylene glycol were added to the reactor. The gas in the reactor was replaced with nitrogen, and then the nitrogen was filled and pressurized to 3MPa. The temperature was raised to 50°C while stirring, and maintained for 10min. The temperature was further raised to 150°C and maintained for 2h. The temperature was raised to 190°C again, maintained for 1h, cooled to 150°C, and decompressed to 2kPa and maintained for 50min. The product was taken out and cooled and collected. There were no obvious condensed droplets on the reactor wall, indicating that the β-butyrolactone reaction was relatively complete; the product had no bubbles. The product had a weight average molecular weight of 91378 and a melting temperature of 182°C. The yield tensile strength was 71.6MPa, the flexural strength was 97.0MPa, the flexural modulus was 3.1GPa, and the elongation at break was 6.6%.

Example 3

80g glycolide, 20g L-lactide, 20mg tetrabutyl titanate, 1g 2-hydroxymethyl-1,3-propanediol were added to the reactor, the gas in the reactor was replaced with nitrogen, and then the nitrogen was filled and pressurized to 0.12MPa. The temperature was raised to 100℃ while stirring, and maintained for 5min, and then continued to rise to 180℃ and maintained for 12h. The temperature was raised to 200℃ again, maintained for 30min, cooled to 180℃, and decompressed to 0.5kPa and maintained for 10min. The product was taken out and cooled and collected. There was no obvious condensed material on the reactor wall, indicating that the L-lactide reaction was relatively complete; the product had no bubbles. The product had a weight average molecular weight of 120762, a melting temperature of 175℃, a yield tensile strength of 83.5MPa, a flexural strength of 113.5MPa, a flexural modulus of 3.5GPa, and an elongation at break of 7%.

Example 4

98g glycolide, 2g ε-caprolactone, and 10mg stannous chloride were added to the reactor. After replacing the gas in the reactor with nitrogen, the reactor was filled with nitrogen and pressurized to 0.2MPa. The temperature was raised to 80°C while stirring, and maintained for 30min. The temperature was further raised to 150°C and maintained for 20h. The temperature was raised to 220°C again, maintained for 10min, cooled to 160°C, decompressed to 0.5kPa and maintained for 10min. The product was taken out and cooled and collected. There were no obvious condensed droplets on the reactor wall, indicating that the ε-caprolactone reaction was relatively complete and the product had no bubbles. The product had a weight average molecular weight of 164126, a melting temperature of 215°C, a yield tensile strength of 93.6MPa, a flexural strength of 128.6MPa, a flexural modulus of 3.9GPa, and an elongation at break of 8%.

Example 5

80g glycolide, 10g ε-caprolactone, 10g β-butyrolactone, 20mg stannous chloride, and 1.8g inositol were added to the reactor, and the gas in the reactor was replaced with nitrogen, and then the nitrogen was filled and pressurized to 5MPa. The temperature was raised to 60°C while stirring, and maintained for 20min, and then continued to rise to 140°C and maintained for 8h. The temperature was raised to 200°C again, maintained for 1h, cooled to 160°C, and decompressed to 0.5kPa and maintained for 30min. The product was taken out and cooled and collected. There were no obvious condensed droplets on the reactor wall, indicating that the reaction of ε-caprolactone and β-butyrolactone was relatively complete; the product had no bubbles. The product had a weight average molecular weight of 67588, a melting temperature of 188°C, a yield tensile strength of 78.1MPa, a flexural strength of 106.5MPa, a flexural modulus of 3.3GPa, and an elongation at break of 51%.

Example 6

80g glycolide, 15g DL-lactide, 5g ε-caprolactone, 20mg stannous chloride, 0.5g aspartic acid oligomer (Mw<3000) were added to the reactor, the gas in the reactor was replaced with nitrogen, and then the nitrogen was filled and pressurized to 0.5MPa. The temperature was raised to 90°C while stirring, and maintained for 10min, and then continued to rise to 140°C and maintained for 6h. The temperature was raised to 200°C again, maintained for 0.5h, cooled to 180°C, and decompressed to 0.5kPa and maintained for 30min. The product was taken out and cooled and collected. There was no obvious condensed material on the reactor wall, indicating that DL-lactide and ε-caprolactone reacted relatively completely and the product had no bubbles. The product had a weight average molecular weight of 112059, a melting temperature of 187°C, a yield tensile strength of 81.9MPa, a flexural strength of 111.5MPa, a flexural modulus of 3.4GPa, and an elongation at break of 29%.

Comparative Example 1

60g glycolide, 40g ε-caprolactone, 20mg stannous chloride, and 1g glutaric acid were added to the reactor, and the gas in the reactor was replaced with nitrogen and kept consistent with the atmospheric pressure. The temperature was raised to 60°C while stirring, and maintained for 20min, and then continued to rise to 140°C and maintained for 6h. The temperature was raised to 180°C again, maintained for 3h, cooled to 160°C, and decompressed to 50kPa and maintained for 30min. The product was taken out and cooled. There were a small number of bubbles near the surface. After the reaction was completed, there were more droplets on the reactor wall, and ε-caprolactone was detected. This shows that ε-caprolactone failed to react fully under normal pressure reaction conditions, and the bubbles in the product would cause internal defects in the material, which may have adverse effects on the product in subsequent use, such as reduced mechanical strength and accelerated degradation of the product due to increased specific surface area.

Comparative Example 2

70g glycolide, 30g β-butyrolactone, 100mg stannous isooctanoate, and 0.1g propylene glycol were added to the reactor, and the gas in the reactor was replaced with nitrogen and kept consistent with the atmospheric pressure. The temperature was raised to 50°C while stirring, and maintained for 10 minutes. The temperature was further raised to 150°C and maintained for 2 hours. The temperature was raised to 190°C again, maintained for 1 hour, cooled to 150°C, and decompressed to 2kPa and maintained for 10 minutes. The product was taken out and cooled and collected. After the reaction was completed, there were many droplets on the wall of the reactor, and it was detected that there were β-butyrolactone components; the solid product was loose and porous, and it was easy to break into fine particles. This shows that β-butyrolactone failed to fully react under normal pressure reaction conditions, and the product quality was poor.

Comparative Example 3

98g glycolide, 2g ε-caprolactone, and 10mg stannous chloride were added to the reactor, and the gas in the reactor was replaced with nitrogen, and then the nitrogen was filled and pressurized to 0.2MPa, and the temperature was raised to 80°C while stirring, and maintained for 30min, and then the temperature was further raised to 150°C, and maintained for 20h, and then the pressure was reduced to 0.5kPa and maintained for 10min, and the product was taken out, cooled, and collected. The product had no bubbles, a weight average molecular weight of 39458, and a melting temperature of 208°C.

Comparative Example 4

100g ε-caprolactone and 60mg stannous chloride were added to the reactor, and the gas in the reactor was replaced with nitrogen and kept consistent with the atmospheric pressure. The temperature was raised to 60°C while stirring, and maintained for 20min, and then continued to rise to 120°C and maintained for 4h. The temperature was raised to 150°C again, and maintained for 1h. The product was taken out and cooled and collected. After the reaction was completed, there were many droplets on the wall of the reactor, and the components of ε-caprolactone were detected. The product had no bubbles, a weight-average molecular weight of 45063, a melting temperature of only 60°C, and a limited range of applications.

Comparative Example 5

98 g of glycolide, 2 g of ε-caprolactone and 10 mg of stannous chloride were added to the reactor. The gas in the reactor was replaced with nitrogen and then pressurized to 0.2 MPa with nitrogen. The temperature was raised to 80°C while stirring, and then immediately raised to 150°C. After reaching the set temperature, the temperature was raised to 220°C again and maintained for 10 minutes. The product was charred and dark brown.

Some preparation processes and product properties of Examples 1-6 and Comparative Examples 1-5 are summarized in Table 1.

By comparing Example 1 and Comparative Example 1, and Example 2 and Comparative Example 2, it can be seen that the polyglycolide copolymer prepared by the synthesis method of the present invention has no bubbles, and the comonomer reaction is relatively complete, while after changing the reaction pressure to atmospheric pressure, the product has bubbles and is even loose and fragile, and the comonomer reaction is incomplete, indicating that the synthesis method of the present invention can avoid the appearance of bubbles in the product and ensure that the comonomer reaction is relatively complete.

By comparing Example 4 with Comparative Example 3, it can be seen that the polyglycolide copolymer prepared by the synthesis method of the present invention has a very high weight average molecular weight, and after omitting the third heating reaction step, the weight average molecular weight of the product is significantly reduced, indicating that the synthesis method of the present invention can significantly increase the molecular weight of the polyglycolide copolymer. It can be seen from Comparative Example 4 that the reaction of the ε-caprolactone monomer is not complete without pressure, and due to the absence of glycolide, the melting temperature of the product is very low and the application range is limited. By comparing Example 4 with Comparative Example 5, it can be seen that if the second heating reaction step is not maintained for a sufficient time, the polyglycolide copolymer product cannot be obtained.

Table 1: Preparation process and product properties of Examples 1-6 and Comparative Examples 1-5

Claims (10)

1. A process for preparing a polyglycolide copolymer, the process comprising the steps of:

(1) Mixing glycolide, a comonomer, a catalyst and optionally a first auxiliary agent under inert gas atmosphere at 40-100 ℃ and at a pressure higher than normal pressure;

(2) Reacting the material obtained in the step (1) in an inert gas atmosphere at 120-210 ℃ under a pressure higher than normal pressure, and optionally adding a second auxiliary agent during the reaction to obtain a first reaction product;

optionally, step (2) further comprises: reacting the first reaction product in inert gas atmosphere at 150-225 ℃ and under the pressure higher than normal pressure, and optionally adding a third auxiliary agent during the reaction to obtain a second reaction product;

(3) And (3) devolatilizing the material obtained in the step (2).

2. The method of claim 1, wherein the method has one or more of the following features:

the comonomer is selected from one or more of aliphatic cyclic ethers, aliphatic lactones and aliphatic cyclic lactide esters other than glycolide, for example, from one or more of propiolactone, caprolactone, valerolactone, butyrolactone, heptanolactone, octalactone, nonanolactone, decalactone, lactide, trimethylene carbonate, ethylene oxide, propylene oxide, methyl propylene oxide, oxetane, 1, 2-butylene oxide, tetrahydrofuran, dioxolane, dioxane and substituent-containing ethylene oxide;

the catalyst is selected from one or more of tin salt, titanium salt, magnesium salt, aluminum salt, calcium salt, ferric salt, manganese salt, zinc salt, organic tin compound, organic titanium compound, organic magnesium compound, organic aluminum compound, organic calcium compound, organic iron compound, organic manganese compound and organic zinc compound;

the first auxiliary agent comprises one or more selected from an initiator, a heat stabilizer, an antioxidant and an anti-hydrolysis agent;

the second auxiliary agent comprises one or more selected from an initiator, a heat stabilizer, an antioxidant and an anti-hydrolysis agent;

the third auxiliary agent comprises one or more selected from a cross-linking agent, a heat stabilizer, an antioxidant and a hydrolysis resistance agent.

3. The method of claim 2, wherein the comonomer is selected from one or more of epsilon-caprolactone, beta-butyrolactone, DL-lactide, L-lactide, trimethylene carbonate, ethylene oxide, propylene oxide, and dioxane.

4. The method of claim 2, wherein the initiator is selected from one or more of an aliphatic carboxylic acid having a carbon number less than or equal to 12, an aliphatic anhydride, a natural amino acid oligomer, an aliphatic alcohol, and an aliphatic amine.

5. The method of claim 2, wherein the cross-linking agent is selected from one or more of aliphatic dicarboxylic acids having a carbon number less than or equal to 12, aliphatic polycarboxylic acids, anhydrides of aliphatic dicarboxylic acids and aliphatic polycarboxylic acids, natural amino acid oligomers, aliphatic diols, aliphatic polyols, aliphatic diamines, and aliphatic polyamines.

6. The method of claim 1, wherein the method has one or more of the following features:

the mass fraction of glycolide accounting for the total mass of the monomer is more than or equal to 50 percent;

the dosage of the catalyst is 0.001% -0.1% of the total mass of the monomers;

adding an initiator or not in the step (1), wherein if the initiator is added, the dosage of the initiator is 0.01-5% of the total mass of the monomer, preferably 0.1-2%;

and (2) adding a cross-linking agent or not in the process of preparing the second reaction product in the step (2), wherein if the cross-linking agent is added, the dosage of the cross-linking agent is 0.01-3%, preferably 0.1-2% of the total mass of the monomers.

7. The method of claim 1, wherein the method has one or more of the following features:

the mixing temperature in the step (1) is 50-100 ℃;

the mixing time in the step (1) is 1-30 min, preferably 5-30 min;

step (1) is carried out at 0.12-20 MPa, preferably at 0.15-10 MPa;

the reaction temperature for preparing the first reaction product in the step (2) is 140-200 ℃;

the reaction time for preparing the first reaction product in the step (2) is 0.5 to 24 hours, preferably 2 to 20 hours;

the preparation of the first reaction product in step (2) is carried out at 0.12 to 20MPa, preferably at 0.15 to 10MPa;

the reaction temperature for preparing the second reaction product in the step (2) is 180-220 ℃;

the reaction time for preparing the second reaction product in the step (2) is 0.1 to 5 hours, preferably 0.15 to 3.5 hours;

the preparation of the second reaction product in step (2) is carried out at 0.12 to 20MPa, preferably at 0.15 to 10MPa;

the reaction temperature for preparing the second reaction product in the step (2) is higher than the reaction temperature for preparing the first reaction product in the step (2); preferably, the reaction temperature for preparing the second reaction product in step (2) is at least 20 ℃ higher than the reaction temperature for preparing the first reaction product in step (2).

8. The method of claim 1, wherein step (3) comprises devolatilizing the material obtained in step (2) at 0.5 to 100kPa, 150 to 190 ℃;

preferably, the devolatilization time is 10 to 60 minutes.

9. A polyglycolide copolymer prepared by the method of any one of claims 1-8.

10. An article comprising the polyglycolide copolymer of claim 9.