Modified polylactic acid-glycolic acid copolymer as well as preparation method and application thereof

Abstract

The invention relates to a modified polylactic acid-glycolic acid copolymer and a preparation method and application thereof.The preparation method comprises the steps that glycolic acid monomers, lactic acid monomers, a functional branching agent and a catalyst are mixed and react, and a PLGA polymer melt is prepared; the functional branching agent comprises one or more of the following substances: a hyperbranched polyhydroxy polymer, a polyamido compound and a hyperbranched polycarboxyl polymer; after the PLGA polymer melt is cooled, performing crushing treatment to obtain a crushed material; and carrying out melt blending on the crushed material, a chain extender and a functional aid, and carrying out chain extension reaction to obtain the modified polylactic acid-glycolic acid copolymer. Compared with the prior art, the preparation method has the advantages that the raw materials are easy to obtain and environment-friendly, industrial amplification production is easy, and the prepared modified polylactic acid-glycolic acid copolymer is high in molecular weight and strength and has good mechanical property, heat resistance and biological full-degradation performance.

Description

Technical Field

[0001] The invention relates to the technical field of chemical modification, in particular to a modified polylactic acid-glycolic acid copolymer and a preparation method and application thereof. Background Art

[0002] Poly(lactic-co-glycolic acid), PLGA, is a fully biodegradable material with excellent mechanical properties, heat resistance and barrier properties. It has very important applications in medical devices, oil field temporary plugging agents, high-end membrane materials and other fields. The existing one-step process can only produce low molecular weight PLGA, while the two-step process requires the preparation of intermediates glycolide and lactide first, and then forms high-performance PLGA through ring-opening polymerization. This process is cumbersome, and the purification process of glycolide and lactide requires a large amount of organic solvents, which is inconsistent with the modern development concept of "green and low carbon".

[0003] In the prior art, PLGA prepared by a one-step process is modified to further increase its molecular weight. For example, in CN103864999A, lactic acid-glycolic acid copolymer is modified by maleic anhydride, a crude polylactic acid-glycolic acid copolymer is first prepared, and then the crude product is purified and dried, and the obtained pure product is reacted with maleic anhydride to obtain the final product. In the above preparation process, the crude copolymer needs to be purified first, and a large amount of organic solvent is still required during the purification process.

[0004] Therefore, there is an urgent need for a method for preparing a modified polylactic acid-glycolic acid copolymer that has readily available raw materials, is environmentally friendly, and is easy to industrially scale up for production, so as to obtain a modified polylactic acid-glycolic acid copolymer with good properties. Summary of the invention

[0005] The purpose of the present invention is to provide a modified polylactic acid-glycolic acid copolymer and a preparation method and application thereof in order to solve the above problems. The present invention adopts glycolic acid monomers and lactic acid monomers as raw materials, and prepares PLGA polymers through esterification / ester exchange reaction and polycondensation reaction under the action of catalysts and functional branching agents. Then, the PLGA polymer is crushed and then melt-chain extended and blended to obtain the modified polylactic acid-glycolic acid copolymer. The raw materials are easily available, environmentally friendly, and easy to industrially scale up.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] The first object of the present invention is to provide a method for preparing a modified polylactic acid-glycolic acid copolymer, the preparation method comprising the steps of:

[0008] (1) mixing and reacting glycolic acid monomers, lactic acid monomers, functional branching agents and catalysts to prepare a PLGA polymer melt through transesterification or esterification reaction and polycondensation reaction;

[0009] (2) after the PLGA polymer melt is cooled, pulverizing the PLGA polymer melt to obtain a pulverized material;

[0010] (3) Melting and blending the crushed material, chain extender and functional additive, and obtaining a modified polylactic acid-glycolic acid copolymer after chain extension reaction.

[0011] Furthermore, the glycolic acid monomer may be one or more of glycolic acid, methyl glycolate, ethyl glycolate, propyl glycolate, isopropyl glycolate, butyl glycolate and the like.

[0012] Furthermore, the lactic acid monomer may be one or more of lactic acid, methyl lactate, ethyl lactate, propyl lactate, isopropyl lactate and butyl lactate.

[0013] Furthermore, the catalyst includes but is not limited to one or more of tetrabutyl titanate, isopropyl titanate, stannous chloride, stannous octoate, zinc acetate dihydrate, titanium glycolate, antimony glycolate, magnesium oxide, antimony trioxide, antimony acetate, etc.

[0014] Furthermore, the functional branching agent includes one or more of the following substances: a hyperbranched polyhydroxy polymer, a polyamine compound and a hyperbranched polycarboxyl polymer.

[0015] Furthermore, the hyperbranched polyhydroxy polymer includes one or more of a hyperbranched polyester polyol having a molecular weight of 500 to 10,000 or a hyperbranched polyether polyol having a molecular weight of 500 to 10,000.

[0016] Furthermore, the polyamine compound includes one or more of hexamethylenetetramine, tris(2-aminoethyl)amine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, low-molecular-weight polyethyleneimine with a molecular weight of 200 to 20,000, and amino-treated nanoparticles with a molecular weight of 200 to 20,000.

[0017] Furthermore, the hyperbranched polycarboxyl polymer comprises a carboxyl-terminated hyperbranched polyamide having a molecular weight of 300 to 30,000.

[0018] As a preferred solution, the functional branching agent is a hyperbranched polyester polyol with a molecular weight of 500 to 10,000, and the hyperbranched polyester polyol with a molecular weight of 500 to 10,000 is prepared by the following method:

[0019] (s1) adding equal moles of dibasic acid and diol, and esterification catalyst into a reaction bottle, stirring with magnetic force at 60-80° C., and adding polyol in a molar ratio of 0.1% to 2% of the dibasic acid, wherein the amount of esterification catalyst is 0.01wt% to 0.2wt% of the dibasic acid;

[0020] (s2) heating under a nitrogen atmosphere and reacting at 80-150° C. for 2-6 hours;

[0021] (s3) reducing the pressure of the reaction system and continuing the reaction within the range of 50 kPa to 50 Pa for 2 to 10 hours;

[0022] (s4) stopping the reaction, pouring out the product while hot, cooling it, crushing it into particles of 10 to 100 meshes, and drying it to obtain a hyperbranched polyester polyol with a molecular weight of 500 to 10,000.

[0023] More preferably, the molecular weight of the hyperbranched polyester polyol is 5,000-10,000.

[0024] Furthermore, the esterification catalyst may be a tin salt, a zinc salt, a titanium salt, a sulfur salt, tin oxide, zinc oxide, titanium oxide, sulfur oxide, or a combination thereof, and is preferably the same as the catalyst in step (1).

[0025] Furthermore, the dibasic acid may be one or more of succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid and the like.

[0026] Furthermore, the diol may be one or more of ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol and the like.

[0027] Furthermore, the polyol can be selected from one or more of glycerol, pentaerythritol, dipentaerythritol, glycerol, xylitol, mannitol, sorbitol and the like.

[0028] As a preferred solution, the functional branching agent is an aminated nanoparticle with a molecular weight of 200 to 20,000. The nanoparticle can be selected from siloxane nanoparticles with a particle size of 10 to 500 nm. The aminated nanoparticle is prepared by the following method:

[0029] (s1) adding a silane coupling agent (e.g., silane coupling agent KH550, γ-aminopropyltriethoxysilane) and concentrated hydrochloric acid (37%) with a molar fraction of 0.05% to 0.5% (relative to the silane coupling agent) to a low-carbon alcohol solvent, and stirring with a magnetic stirrer;

[0030] (s2) the reaction system is reacted under continuous magnetic stirring at room temperature and pressure for 3 to 15 days, and then the excess solvent is removed by rotary evaporation until a flocculent to granular precipitate is formed, and the precipitate is filtered and dried at 50 to 70° C. (preferably 60° C.) to obtain white granules;

[0031] (s3) the obtained white particles are fully dissolved again in a low-carbon alcohol solvent, and then passed through a column filled with an anion exchange resin to obtain a nanoparticle mixed solution;

[0032] (s4) The obtained nanoparticle mixed solution is dried by rotary evaporation at 30-50° C. (preferably 40° C.) to obtain amino-treated siloxane nanoparticles with a molecular weight of 200-20,000.

[0033] Furthermore, the low-carbon alcohol solvent is selected from one or more of methanol, ethanol, isopropanol, n-propanol and the like.

[0034] More preferably, the molecular weight of the amination-treated siloxane nanoparticles is 5,000 to 20,000.

[0035] As a preferred solution, the functional branching agent is a carboxyl-terminated hyperbranched polyamide with a molecular weight of 300 to 30,000, and the carboxyl-terminated hyperbranched polyamide with a molecular weight of 300 to 30,000 is prepared by the following method:

[0036] (s1) under nitrogen atmosphere, a polar aprotic solvent (one or more of NMP, DMF, DMSO, and DMAC), triphenyl phosphite and pyridine in a molar ratio of 1:1 are added to a reaction bottle and dissolved by magnetic stirring;

[0037] (s2) adding a polyacid / anhydride and a diamine into a reaction flask at a molar ratio of 0.5% to 5% excess carboxyl group, and mixing them uniformly at 60 to 90° C., wherein the molar ratio of the sum of the molar amounts of triphenyl phosphite and pyridine to the diamine is 0.01% to 0.1%, and the mass of the solvent accounts for 50% to 80% of the total;

[0038] (s3) heating the reaction system to 130-150° C. (preferably 140° C.) and continuing the reaction for 4-10 hours;

[0039] (s4) After the reaction is completed, the reaction solution is poured into water for precipitation, filtered and then dried to obtain a carboxyl-terminated hyperbranched polyamide with a molecular weight of 300 to 30,000.

[0040] Preferably, the molecular weight of the carboxyl-terminated hyperbranched polyamide is 5000 to 30000. Preferably, the polyacid / anhydride is selected from one or more of 2,2-hydroxymethylpropionic acid, 2,2-hydroxymethylbutyric acid, trimellitic acid, trimellitic anhydride, pyromellitic acid, pyromellitic anhydride, trimesic acid, etc.

[0041] Furthermore, the diamine is selected from one or more of ethylenediamine, propylenediamine, hexamethylenediamine, p-phenylenediamine, o-phenylenediamine, m-phenylenediamine, and benzidine.

[0042] As a preferred solution, the molar ratio of glycolic acid monomers to lactic acid monomers is 50:50 to 90:10, and the molar amount of the functional branching agent is 0.1% to 3% of the total molar amount of glycolic acid monomers and lactic acid monomers.

[0043] As a preferred solution, the molar amount of the catalyst accounts for 0.005% to 6% of the total molar amount of glycolic acid monomers and lactic acid monomers.

[0044] Furthermore, the chain extender includes but is not limited to one or more of the following categories: 1) isocyanates: such as one or more of p-phenylene diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, diphenylmethane diisocyanate, and hexamethylene diisocyanate; 2) epoxies: such as one or more of BASF ADR type and KL-E4370; 3) oxazolines: such as one or more of 1,3-PBO dioxazoline and 2,2-bis(2-oxazoline).

[0045] As a preferred solution, the amount of the chain extender added is 1 wt% to 10 wt% of the pulverized material.

[0046] As a preferred solution, p-phenylene diisocyanate is selected as the chain extender.

[0047] As a preferred solution, the functional additives include but are not limited to one or more of antioxidants, reinforcing agents, stiffening agents, nucleating agents, flame retardants, and opening agents, and the added amount of each functional additive is 0.01 to 10% of the total molar amount of glycolic acid monomers and lactic acid monomers.

[0048] Further preferably, the antioxidant includes but is not limited to one or more of hindered phenols and phosphites, such as one or more of antioxidant 1010, antioxidant 168 and their composite products.

[0049] Further preferably, the reinforcing agent includes but is not limited to one or more of various organic and inorganic nanoparticles, such as one or more of NA960, NA21, nano calcium carbonate, talcum powder, etc. commercially available from Shanghai Magic Box New Materials Company.

[0050] Further preferably, the stiffening agent includes but is not limited to one or more of various organic and inorganic nanoparticles, such as one or more of NA960, NA21, nano calcium carbonate, talcum powder, etc. commercially available from Shanghai Magic Box New Materials Company.

[0051] Further preferably, the nucleating agent includes but is not limited to one or more of various organic and inorganic nanoparticles, such as one or more of NA960, NA21, nano calcium carbonate, talcum powder, etc. commercially available from Shanghai Magic Box New Materials Company.

[0052] Further preferably, the flame retardant includes but is not limited to one or more of inorganic hydroxides and modified hydroxides thereof, phosphorus-nitrogen flame retardants, silicone flame retardants, etc., such as Doher-998 of Doer Chemical, APP flame retardant of Wanran Technology, etc.

[0053] Further preferably, the anti-blocking agent includes but is not limited to one or more of talc, diatomaceous earth, oleamide, erucamide and EBS (ethylene bisstearamide) derivatives, such as one or more of Lingwei Technology's K-80, K-35X, K-25, etc.

[0054] Furthermore, step (1) specifically includes:

[0055] (s1) heating the reaction device to 60-100° C., introducing an inert gas protection (for example, circulate the inert gas 2-4 times, evacuate to an absolute pressure of less than 200 Pa, and then fill to normal pressure), adding glycolic acid monomer, lactic acid monomer, functional branching agent and catalyst, and stirring to mix uniformly;

[0056] (s2) performing an esterification reaction or an ester exchange reaction: raising the temperature of the reaction device, reacting at 110° C. to 170° C. for 2 to 8 hours, and ending the esterification reaction or the ester exchange reaction when the volume or weight of the by-product reaches 60 to 90% of the theoretical volume or weight;

[0057] (s3) performing polycondensation reaction: vacuumizing at a rate of 0.1 to 10 kPa / min, raising the polycondensation reaction temperature to 170 to 220° C. and a vacuum degree of 30 to 500 Pa, continuing the reaction for 2 to 16 hours, and terminating the reaction when the power of the stirring motor no longer increases, thereby preparing a PLGA polymer melt.

[0058] Furthermore, step (2) specifically includes:

[0059] After the PLGA polymer melt is cooled, a cooled PLGA polymer is obtained, and the cooled PLGA polymer is crushed by a crusher and sieved by a sifter to obtain a material with a particle size of 10 to 100 mesh.

[0060] Furthermore, step (3) specifically includes:

[0061] The pulverized material, functional additives and chain extender are melt blended at a temperature of 130-220° C. for a reaction time of 0.5-5 min to obtain a modified polylactic acid-glycolic acid copolymer. A suitable melt blending device can be selected according to the amount of raw materials. For example, in the laboratory stage, a torque rheometer is used as a melt blending device, and in the scale-up production stage, a twin-screw extruder is used as a melt blending device.

[0062] The second object of the present invention is to provide a modified polylactic acid-glycolic acid copolymer (modified PLGA copolymer), which is prepared by the above-mentioned preparation method.

[0063] Furthermore, the modified PLGA copolymer is light yellow, white, yellow, gray, brown, black, has a molecular weight of 50,000 to 200,000, an intrinsic viscosity of 0.5 to 1.8 dL / g, a melt index of 100 to 5 g / 10 min (190° C., 2.16 kg), a tensile strength of 20 to 100 MPa, and an elongation at break of 30% to 300%.

[0064] Further preferably, the modified PLGA copolymer has a molecular weight of 90,000 to 200,000, an intrinsic viscosity of 1 to 1.8 dL / g, a melt index of 50 to 5 g / 10 min (190° C., 2.16 kg), a tensile strength of 40 to 100 MPa, and an elongation at break of 50% to 300%.

[0065] The third object of the present invention is to provide an application of a modified polylactic acid-glycolic acid copolymer, wherein the modified polylactic acid-glycolic acid copolymer is prepared by the above-mentioned preparation method.

[0066] Furthermore, the application fields of the modified PLGA copolymer include but are not limited to one or more of various degradable and recyclable material fields such as degradable film materials, disposable lunch boxes, disposable straws, disposable packing bags, disposable knives, disposable forks, disposable spoons, degradable logistics packaging, degradable tapes, degradable gift boxes, recyclable degradable injection molding products, foaming materials, and blended modified ingredients.

[0067] Compared with the prior art, the beneficial effects of the present invention are embodied in the following aspects:

[0068] 1) This scheme uses glycolic acid monomers and lactic acid monomers in the presence of a catalyst and a functional branching agent to prepare PLGA polymers through esterification / ester exchange reaction and polycondensation reaction. The PLGA polymers are then crushed and then melt-chain extended and blended to obtain modified polylactic acid-glycolic acid copolymers. Compared with the existing two-step process using glycolide and lactide as raw materials, the raw materials are easily available, environmentally friendly, and easy to scale up for industrial production.

[0069] 2) The functional branching agent is a polyamine compound or a hyperbranched oligomer, which reacts with glycolic acid monomers and lactic acid monomers to form a PLGA polymer with a branched structure. The branched structure can increase the subsequent cross-linking sites with the chain extender, further improving the molecular weight and strength of the modified polylactic acid-glycolic acid copolymer obtained. The modified polymer has good mechanical properties, heat resistance and biodegradability. DETAILED DESCRIPTION

[0070] The present invention is described in detail below in conjunction with specific embodiments, but is by no means intended to limit the present invention. Features such as preparation methods, materials, structures or composition ratios not explicitly described in this technical solution are considered to be common technical features disclosed in the prior art.

[0071] Unless otherwise specified, the reagents, methods, instruments and equipment used in the present invention are conventional reagents, methods, instruments and equipment in the art. Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0072] Comparative Example 1

[0073] This comparative example provides a method for preparing a modified polylactic acid-glycolic acid copolymer, wherein the functional branching agent used is pentaerythritol, and the method comprises the following steps:

[0074] Place a 250 ml two-necked bottle in an oil bath at 80 °C and heat it. 2 Protection. Add 0.85mol of glycolic acid crystals, 0.15mol of lactic acid (70% aqueous solution), 0.0005mol of stannous chloride, and 0.002mol of pentaerythritol in sequence, stir magnetically for 0.5h, and mix well. Gradually increase the temperature to 130℃, react at 130℃ for 1h; increase the temperature to 150℃, react at 150℃ for 1h; increase the temperature to 170℃, react at 170℃ for 1h. Then evacuate to 30kPa at a rate of 5kPa / min at 170℃, react for 1h; continue to evacuate to 5kPa at a rate of 5kPa / min, react for 1h, continue to evacuate to 50-100Pa, and increase the temperature to 190℃, react for 6h.

[0075] The material was cooled, taken out, crushed, and sieved to obtain a material with a particle size of 50 mesh. The obtained material, 2wt% of p-phenylene diisocyanate, and 0.003mol of antioxidant 1010 were added to a torque rheometer, and reacted at 190°C and 100rpm for 5min to obtain a modified polylactic acid-glycolic acid copolymer.

[0076] Example 1

[0077] The preparation method of the modified polylactic acid-glycolic acid copolymer provided in this embodiment uses a hyperbranched polyester polyol with a molecular weight of 500 to 10,000 as a functional branching agent, and the preparation method comprises the following steps:

[0078] Preparation of hyperbranched polyester polyol: add equimolar succinic acid and ethylene glycol and 0.1wt% (relative to succinic acid) of stannous chloride into a reaction bottle, add pentaerythritol at a molar ratio of 0.5% to succinic acid under 70°C and magnetic stirring; gradually increase the temperature under a slightly positive nitrogen atmosphere, react at 110°C for 3h; gradually reduce the pressure of the reaction system, and continue to react at 1kPa for 2h; after the reaction is completed, pour out the product while hot, cool it, crush it into 50 mesh particles and dry it to obtain hyperbranched poly(ethylene succinate). The molecular weight of the hyperbranched poly(ethylene succinate) is measured to be 8600g / mol.

[0079] Preparation of modified PLGA copolymer: The preparation method is the same as that of Comparative Example 1, except that 0.002 mol of pentaerythritol is replaced by 0.002 mol of the above-mentioned hyperbranched polyethylene succinate to obtain a modified polylactic acid-glycolic acid copolymer.

[0080] Example 2

[0081] The preparation method of the modified polylactic acid-glycolic acid copolymer provided in this embodiment is the same as that in Example 1, except that the amount of the hyperbranched poly(ethylene succinate) added is changed from 0.002 mol to 0.005 mol to obtain the modified polylactic acid-glycolic acid copolymer.

[0082] Example 3

[0083] The preparation method of the modified polylactic acid-glycolic acid copolymer provided in this embodiment is the same as that in Example 1, except that the amount of the hyperbranched polyethylene succinate added is changed from 0.002 mol to 0.01 mol to obtain the modified polylactic acid-glycolic acid copolymer.

[0084] Example 4

[0085] This embodiment provides a method for preparing a modified polylactic acid-glycolic acid copolymer, wherein the functional branching agent used is a carboxyl-terminated hyperbranched polyamide having a molecular weight of 300 to 30,000, and the preparation method comprises the following steps:

[0086] Preparation of carboxyl-terminated hyperbranched polyamide: Under nitrogen atmosphere, add appropriate amount of polar non-protonic solvent DMSO, triphenyl phosphite and pyridine in a molar ratio of 1:1 (the molar ratio of the sum of the molar amounts of triphenyl phosphite and pyridine to hexamethylenediamine in the subsequent step is 0.05%) to a reaction bottle, stir magnetically to dissolve; add trimellitic anhydride and hexamethylenediamine to the reaction bottle in a molar ratio of 2% excess carboxyl, mix evenly at 80°C, DMSO solvent accounts for 60% of the mass in the system; heat the reaction system to 140°C, and continue the reaction for 6 hours; after the reaction is completed, pour the reaction solution into water for precipitation, filter and dry, and a carboxyl-terminated hyperbranched polyamide can be obtained. The molecular weight of the hyperbranched polyamide is measured to be 12000g / mol.

[0087] Preparation of modified PLGA copolymer: The preparation method is the same as that of Comparative Example 1, except that 0.002 mol of pentaerythritol is replaced by 0.005 mol of the above hyperbranched polyamide to obtain a modified polylactic acid-glycolic acid copolymer.

[0088] Example 5

[0089] The preparation method of the modified polylactic acid-glycolic acid copolymer provided in this embodiment is the same as that in Example 4, except that the addition amount of the hyperbranched polyamide is changed from 0.005 mol to 0.01 mol to obtain the modified polylactic acid-glycolic acid copolymer.

[0090] Example 6

[0091] The preparation method of the modified polylactic acid-glycolic acid copolymer provided in this embodiment is the same as that in Example 4, except that the addition amount of the hyperbranched polyamide is changed from 0.005 mol to 0.02 mol to obtain the modified polylactic acid-glycolic acid copolymer.

[0092] Example 7

[0093] This embodiment provides a method for preparing a modified polylactic acid-glycolic acid copolymer, wherein the functional branches used are amino-treated nanoparticles with a molecular weight of 200 to 20,000. The preparation method comprises the following steps:

[0094] Silane coupling agent KH550 and 0.1% mole fraction (relative to the silane coupling agent) of concentrated hydrochloric acid (37%) are added to methanol and magnetically stirred; the reaction system is continuously magnetically stirred for 10 days at room temperature and pressure, and the excess methanol solvent is removed by rotary evaporation until flocculent to granular precipitates appear, which are filtered and dried at 60°C to obtain white particles; the obtained white particles are fully dissolved in methanol again, and then passed through a column filled with anion exchange resin to obtain a nanoparticle solution; the obtained nanoparticle solution is dried by rotary evaporation at 40°C to obtain amino-treated nanoparticles with a molecular weight of 15000 g / mol.

[0095] Preparation of modified PLGA copolymer: The preparation method is the same as that of Comparative Example 1, except that 0.002 mol of pentaerythritol is replaced by 0.01 mol of the above-mentioned amino-treated nanoparticles to obtain a modified polylactic acid-glycolic acid copolymer.

[0096] Example 8

[0097] The preparation method of the modified polylactic acid-glycolic acid copolymer provided in this embodiment is the same as that in Example 7, except that the amount of the aminated nanoparticles added is changed from 0.01 mol to 0.02 mol to obtain the modified polylactic acid-glycolic acid copolymer.

[0098] Comparative Example 2

[0099] This comparative example provides a method for preparing a modified polylactic acid-glycolic acid copolymer, in which the functional branching agent used is polyethylene succinate. The preparation method of polyethylene succinate is the same as that of Example 1, except that, in the process of preparing polyethylene succinate, pentaerythritol is not added, and succinic acid and ethylene glycol are added to the reaction bottle at a molar ratio of 2% excess hydroxyl group. The molecular weight of the prepared polyethylene succinate is measured to be 2600 g / mol.

[0100] The preparation method of the modified polylactic acid-glycolic acid copolymer is the same as that of Example 1, except that the hyperbranched poly(ethylene succinate) is replaced with the above-mentioned poly(ethylene succinate) to obtain the modified polylactic acid-glycolic acid copolymer.

[0101] Comparative Example 3

[0102] The preparation method of the modified polylactic acid-glycolic acid copolymer provided in this comparative example is the same as that in Example 1, except that the addition amount of the hyperbranched poly(ethylene succinate) is changed from 0.002 mol to 0.05 mol to obtain the modified polylactic acid-glycolic acid copolymer.

[0103] Performance Test:

[0104] The following performance tests were performed on the modified polylactic acid-glycolic acid copolymer samples of Examples 1 to 8 and Comparative Examples 1 to 3:

[0105] 1. Weight average molecular weight

[0106] The sample was dissolved in a 5 mmol / L sodium trifluoroacetate hexafluoroisopropanol solution to obtain a 0.05-0.3 wt% (mass fraction) solution. The solution was then filtered through a polytetrafluoroethylene filter with a pore size of 0.4 μm. 20 μL of the filtered solution was added to a gel permeation chromatography (GPC) injector to determine the molecular weight of the sample. Five standard molecular weights of methyl methacrylate with different molecular weights were used for molecular weight calibration.

[0107] 2. Intrinsic viscosity

[0108] Weigh about 0.125 g of the sample, dissolve it in 25 ml of hexafluoroisopropanol, and place it in a constant temperature water bath at 25°C. Use an Ubbelohde viscometer to measure the intrinsic viscosity (η). Measure the average value three times. The difference in the outflow time of each measurement does not exceed 0.2 seconds.

[0109] 3. Melt index (MFR) test

[0110] The melt index (MFR) of the copolymer is tested according to the following method: 1) the copolymer is dried at 105°C in a vacuum drying oven; 2) the test temperature of the test instrument is set to 190°C and the instrument is preheated; 3) 4g of the dried copolymer is loaded into a barrel through a funnel, and a piston is inserted into the barrel to press the dried copolymer into a rod; 4) the dried copolymer is kept in the rod for 1 minute under the condition that a weight of 2.16kg is pressed on the top of the rod, and then a section is cut every 30s to obtain a total of five sections; 5) the mass of each sample is weighed and its MFR is calculated. MFR = 600W / t (g / 10min), where W is the average mass of each sample, and t is the cutting time interval of each section.

[0111] 4. Tensile strength and elongation at break

[0112] The test was carried out according to the test standard of GB / T1040.2-2016, the tensile speed was 50mm / min, and 5 groups of samples were tested and the average value was taken.

[0113] Table 1 Performance test results of various embodiments and comparative examples

[0114]

[0115] As shown in Table 1, Example 1 is compared with Comparative Example 1. It can be seen that the use of hyperbranched polyester polyol as a functional branching agent can effectively improve the weight average molecular weight, intrinsic viscosity, tensile strength and elongation at break of the modified polylactic acid-glycolic acid copolymer compared to the commonly used branching agent-pentaerythritol; the use of carboxyl-terminated hyperbranched polyamide or amino-treated nanoparticles as a functional branching agent, compared with the same amount of hyperbranched polyester polyol, the weight average molecular weight, tensile strength and elongation at break of the obtained modified polylactic acid-glycolic acid copolymer are slightly improved. Further, the modified polylactic acid-glycolic acid copolymer prepared by using a commonly used branching agent cannot be detected in the melt index test because it flows out too fast, while the melt index of the modified polylactic acid-glycolic acid copolymer obtained in the present application is between 30 and 5 g / 10 min (190° C., 2.16 kg), and has good hot melt stability.

[0116] Example 1 is compared with Comparative Example 2. In the process of preparing polyester polyol, no polyol is added, and only succinic acid and ethylene glycol are used for esterification reaction. The obtained polyester polyol has a linear structure. When linear polyester polyol is used as a functional branching agent, the obtained modified polylactic acid-hydroxyacetic acid copolymer cannot be detected in the melt index test because it flows out too fast, and the tensile strength is low.

[0117] Example 1 is compared with Comparative Example 3. When the molar amount of the functional branching agent is 5% (greater than 3%) of the total molar amount of glycolic acid monomers and lactic acid monomers, the obtained modified polylactic acid-glycolic acid copolymer is insoluble in 5 mmol / L hexafluoroisopropanol solution of sodium trifluoroacetate or hexafluoroisopropanol, and cross-linking is excessive.

[0118] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for preparing a modified polylactic acid-glycolic acid copolymer, characterized in that: The preparation method comprises the following steps: (1) mixing and reacting glycolic acid monomers, lactic acid monomers, a functional branching agent and a catalyst to prepare a PLGA polymer melt, wherein the functional branching agent comprises one or more of the following substances: a hyperbranched polyhydroxy polymer, a polyamine compound and a hyperbranched polycarboxyl polymer; (2) after the PLGA polymer melt is cooled, pulverizing the PLGA polymer melt to obtain a pulverized material; (3) Melting and blending the crushed material, the chain extender and the functional additive, and obtaining a modified polylactic acid-glycolic acid copolymer after a chain extension reaction.

2. The method for preparing a modified polylactic acid-glycolic acid copolymer according to claim 1, characterized in that: The hyperbranched polyhydroxy polymer includes one or more of a hyperbranched polyester polyol having a molecular weight of 500 to 10,000 or a hyperbranched polyether polyol having a molecular weight of 500 to 10,000; The polyamine compound includes one or more of hexamethylenetetramine, tris(2-aminoethyl)amine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, oligoethyleneimine with a molecular weight of 200 to 20,000, and aminated nanoparticles with a molecular weight of 200 to 20,000; The hyperbranched polycarboxyl polymer comprises a carboxyl-terminated hyperbranched polyamide with a molecular weight of 300 to 30,000.

3. The method for preparing a modified polylactic acid-glycolic acid copolymer according to claim 2, characterized in that: The functional branching agent is a hyperbranched polyester polyol with a molecular weight of 500 to 10,000. The preparation of the hyperbranched polyester polyol with a molecular weight of 500 to 10,000 comprises the following steps: (s1) stirring an equimolar amount of a dibasic acid and a diol, and an esterification catalyst at 60 to 80° C., and simultaneously adding a polyol in a molar ratio of 0.1% to 2% of the dibasic acid; (s2) heating under a nitrogen atmosphere and reacting at 80-150° C. for 2-6 hours; (s3) reducing the pressure of the reaction system and continuing the reaction within the range of 50 kPa to 50 Pa for 2 to 10 hours; (s4) stopping the reaction, and after the product is cooled, crushing the product into particles of 10 to 100 meshes, and drying to obtain a hyperbranched polyester polyol having a molecular weight of 500 to 10,000.

4. The method for preparing a modified polylactic acid-glycolic acid copolymer according to claim 2, characterized in that: The functional branching agent is an aminated nanoparticle with a molecular weight of 200 to 20,000, the nanoparticle is selected from siloxane nanoparticles, and the particle size is 10 to 500 nm. The preparation of the aminated nanoparticle includes the following steps: (s1) adding a silane coupling agent and concentrated hydrochloric acid having a molar fraction of 0.05% to 0.5% relative to the silane coupling agent to a low-carbon alcohol solvent, and stirring the mixture with a magnetic stirrer; (s2) the reaction system is reacted under continuous magnetic stirring at room temperature and pressure for 3 to 15 days, and then the excess solvent is removed by rotary evaporation until a precipitate is formed, and the precipitate is filtered and dried at 50 to 70° C. to obtain white particles; (s3) the obtained white particles are dissolved again in a low-carbon alcohol solvent, and then passed through a column filled with an anion exchange resin to obtain a nanoparticle mixed solution; (s4) The obtained nanoparticle mixed solution is dried by rotary evaporation at 30-50° C. to obtain amino-treated siloxane nanoparticles with a molecular weight of 200-20,000.

5. The method for preparing a modified polylactic acid-glycolic acid copolymer according to claim 2, characterized in that: The functional branching agent is a carboxyl-terminated hyperbranched polyamide with a molecular weight of 300 to 30,000. The preparation of the carboxyl-terminated hyperbranched polyamide with a molecular weight of 300 to 30,000 comprises the following steps: (s1) under a nitrogen atmosphere, uniformly mixing a polar aprotic solvent, triphenyl phosphite and pyridine to obtain a mixed solution, wherein the molar ratio of triphenyl phosphite to pyridine is 1:1; (s2) mixing the polyacid / anhydride and the diamine with the mixed solution of step (s1) at a molar ratio of 0.5% to 5% excess carboxyl group, and mixing them uniformly at 60 to 90° C., wherein the molar ratio of the sum of the molar amounts of triphenyl phosphite and pyridine to the diamine is 0.01% to 0.1%; (s3) raising the temperature of the reaction system to 130-150° C. and continuing the reaction for 4-10 hours; (s4) After the reaction is completed, the reaction solution is poured into water for precipitation, filtered and then dried to obtain a carboxyl-terminated hyperbranched polyamide with a molecular weight of 300 to 30,000.

6. The method for preparing a modified polylactic acid-glycolic acid copolymer according to any one of claims 1 to 5, characterized in that: The molar ratio of the glycolic acid monomer and the lactic acid monomer is 50:50 to 90:10, and the molar amount of the functional branching agent is 0.1% to 3% of the total molar amount of the glycolic acid monomer and the lactic acid monomer; The chain extender includes one or more of the following substances: isocyanates, epoxies and oxazolines. The added amount of the chain extender is 1wt% to 10wt% of the pulverized material.

7. The method for preparing a modified polylactic acid-glycolic acid copolymer according to claim 6, characterized in that: Step (1) specifically includes: (s1) heating the reaction device to 60-100° C., introducing an inert gas protection, adding glycolic acid monomer, lactic acid monomer, functional branching agent and catalyst, and stirring and mixing uniformly; (s2) raising the temperature of the reaction device to react at 110° C. to 170° C. for 2 to 8 hours, and ending the esterification reaction or transesterification reaction when the volume or weight of the by-products reaches 60 to 90% of the theoretical volume or weight; (s3) vacuuming at a rate of 0.1 to 10 kPa / min, raising the polycondensation reaction temperature to 170 to 220° C. and a vacuum degree of 30 to 500 Pa, and continuing the reaction for 2 to 16 hours to prepare a PLGA polymer melt.

8. The method for preparing a modified polylactic acid-glycolic acid copolymer according to claim 6, characterized in that: The particle size of the pulverized material obtained in step (2) is between 10 and 100 meshes; In step (3), the pulverized material, functional additive and chain extender are melt-blended at a temperature of 130 to 220° C. and reacted for 0.5 to 5 minutes to obtain a modified polylactic acid-glycolic acid copolymer.

9. A modified polylactic acid-glycolic acid copolymer, characterized in that: The method is prepared according to any one of claims 1 to 8.

10. An application of a modified polylactic acid-glycolic acid copolymer prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The modified polylactic acid-glycolic acid copolymer is used in the field of degradable and recyclable materials.

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