Preparation method of degradable polyester and obtained degradable polyester

Abstract

The invention discloses a preparation method of degradable polyester and the obtained degradable polyester, and the preparation method comprises the following steps: melting, mixing and reacting a monomer, an initiator, a catalyst, a metal deactivator, an optional anti-hydrolysis agent and an optional antioxidant in a twin-screw extruder, and extruding and granulating to obtain the degradable polyester. According to the preparation method, the polyester is prepared by adopting double-screw continuous reaction extrusion polymerization, and different auxiliaries are added in sections to perform in-situ modification on the polyester: a metal deactivator and an optional anti-hydrolysis agent are added in situ at the rear section of a double-screw extruder to improve the stability of the polyester; and adding the auxiliary antioxidant together with the reaction monomer at the front section of the double-screw extruder to improve the efficiency of the polymerization process.

Description

Technical Field

[0001] The invention belongs to the field of preparation of degradable polyesters, and in particular relates to degradable polyesters with high hydrolysis resistance and stability, such as polyglycolide. Background Art

[0002] Degradable materials usually refer to a type of material that can eventually be decomposed into water and carbon dioxide under conditions such as composting and natural light. It can effectively solve the environmental pollution caused by the widespread use of non-degradable plastic products and achieve sustainable development. Commonly used degradable materials include polylactic acid (PLA), polycaprolactone (PCL), polyhydroxyalkanoates (PHA), polyglycolide (PGA), etc. Among them, PGA is a linear aliphatic polyester with the simplest chemical structure. It is a polymer material with good biocompatibility and unique biodegradability. It is widely used in surgical sutures, orthopedic fixation, tissue repair materials and drug controlled release systems.

[0003] However, PGA materials have poor thermal stability and are not resistant to hydrolysis. During the processing, a small amount of metal element catalysts (such as organic tin catalysts) remaining in the material will further catalyze the chain breakage and thermal degradation of PGA itself.

[0004] In addition, due to its own structure, the main chain of PGA is relatively short, and the ester bond in the main chain lacks the protection of hydrophobic groups, which makes it very easy to hydrolyze. Even if it is stored at room temperature (23°C, 70% relative humidity), it is easy to hydrolyze. Because the hydrolysis of polyester is a self-accelerating reaction, the acid content will accelerate the hydrolysis, and the higher the content of terminal carboxyl groups, the faster the hydrolysis of polyester materials will be, and it will also reduce its stability during processing and subsequent use.

[0005] Traditional PGA preparation methods, such as Chinese patent CN102634001A, usually use intermittent preparation in a polymerization reactor, which requires high pressure and anhydrous conditions, harsh reaction conditions, and low reaction efficiency. If twin-screw reaction extrusion is used for PGA polymerization, continuous polymerization can be used to greatly improve the polymerization efficiency. However, due to the short residence time of the monomer in the twin-screw extruder, a large amount of catalyst needs to be added to ensure the polymerization efficiency. Excessive catalyst residues will catalyze the thermal degradation of subsequent PGA during the secondary thermal processing process. In patent CN 114075378 A, antioxidant 9228 and anti-hydrolysis agent are introduced into PGA to improve the stability of PGA, but in this patent, during the modified secondary processing process, PGA will still be subjected to certain thermal degradation, resulting in a decrease in thermal stability. Summary of the invention

[0006] In order to overcome the problems existing in the prior art, the present invention provides a method for preparing a degradable polyester and the obtained degradable polyester, wherein the preparation method adopts twin-screw continuous reaction extrusion polymerization to prepare the polyester, wherein different additives are added in sections to modify the polyester in situ: a metal passivator and an optional anti-hydrolysis agent are added in situ at the rear section of the twin-screw extruder to improve the stability of the polyester; an auxiliary antioxidant is added together with the reaction monomer at the front section of the twin-screw extruder to improve the efficiency of the polymerization process. The in-situ introduction of the modification additive can effectively avoid the additional thermal degradation of the raw materials caused by secondary processing during the modification process of the synthesized PGA, and can also specifically inhibit the thermal decomposition of PGA caused by excessive PGA catalyst residues during the subsequent melt blending process with other materials.

[0007] One of the purposes of the present invention is to provide a method for preparing a degradable polyester, comprising: melt-mixing and reacting a monomer, an initiator, a catalyst, a metal deactivator, an optional anti-hydrolysis agent, and an optional antioxidant in a twin-screw extruder, and then extruding and granulating to obtain the degradable polyester.

[0008] In a preferred embodiment, the monomer is selected from at least one of methyl glycolate and / or its derivatives, glycolic acid and / or its derivatives, glycolide and / or its derivatives, lactide and / or its derivatives, caprolactone and / or its derivatives, preferably glycolide and / or its derivatives.

[0009] In a preferred embodiment, the initiator is selected from small molecule substances containing hydroxyl groups with a boiling point greater than 160°C.

[0010] In a further preferred embodiment, the initiator is selected from at least one of ethylene glycol, butanediol, glycerol, serinol, leucinol, pentaerythritol, sorbitol, xylitol, amino acids, phenol, hydroquinone, resorcinol, and benzyl alcohol.

[0011] In a preferred embodiment, the catalyst is selected from at least one of salt compounds corresponding to one or more elements of Group IIA, IIIA, IVA, VA, IVB, VIIB, VIII, and IIB metal elements, and organic guanidine compounds.

[0012] In a further preferred embodiment, the catalyst is selected from at least one of the salt compounds corresponding to one or more elements of Sn, Bi, Mg, Al, Ca, Fe, Mn, Ti and Zn, and is further preferably a Sn salt.

[0013] In a preferred embodiment, the antioxidant is selected from commonly used antioxidants in the art, preferably but not limited to one or a combination of two selected from hindered phenol antioxidants and phosphite antioxidants.

[0014] In a further preferred embodiment, the hindered phenol antioxidant is selected from at least one of antioxidant 1010, antioxidant 1024, antioxidant 1076, and antioxidant 1078, and the phosphite antioxidant is selected from at least one of antioxidant 168, antioxidant 608, antioxidant 626, and antioxidant TP80.

[0015] In a preferred embodiment, based on 100 parts by weight of the monomer, the initiator is 0.005 to 5 parts, the catalyst is 0.005 to 1 part, and the antioxidant is 0.005 to 10 parts.

[0016] For example, based on 100 parts by weight of the monomer, the initiator is 0.005 parts, 0.008 parts, 0.01 parts, 0.02 parts, 0.04 parts, 0.06 parts, 0.08 parts, 0.1 parts, 0.2 parts, 0.4 parts, 0.6 parts, 0.8 parts, 1 parts, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts or 5 parts, and the catalyst is 0.005 parts, 0.008 parts, 0.01 parts, 0.02 parts, 0.04 parts, 0.06 parts, 0.08 parts, 0.1 parts, 0.2 parts, 0.4 parts, 0.6 parts, 0.8 parts, 1 parts, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts or 5 parts. 0.02 parts, 0.04 parts, 0.06 parts, 0.08 parts, 0.1 parts, 0.2 parts, 0.4 parts, 0.6 parts, 0.8 parts or 1 parts of the antioxidant; the antioxidant is 0.005 parts, 0.008 parts, 0.01 parts, 0.02 parts, 0.04 parts, 0.06 parts, 0.08 parts, 0.1 parts, 0.2 parts, 0.4 parts, 0.6 parts, 0.8 parts, 1 parts, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts or 10 parts.

[0017] In a further preferred embodiment, based on 100 parts by weight of the monomer, the initiator is 0.01 to 1 part, the catalyst is 0.01 to 0.5 part, and the antioxidant is 0.01 to 5 parts.

[0018] In a preferred embodiment, the metal passivator is selected from at least one of oxalic acid derivatives, salicylic acid derivatives, hydrazide compounds, alkyl phosphates, benzotriazole compounds, and guanidine compounds.

[0019] In a further preferred embodiment, the metal deactivator is selected from at least one of the following products: BASF Chel-180, BASF Irganox MD1024, Eastman OABH, Naugard XL-1, Naugard MD24, ADEKASTAB CDA-1, ADEKASTAB AX71.

[0020] In a preferred embodiment, the anti-hydrolysis agent is a carbodiimide anti-hydrolysis agent.

[0021] In a further preferred embodiment, the anti-hydrolysis agent is selected from carbodiimide polymers and / or carbodiimide compounds, preferably carbodiimide polymers.

[0022] In a further preferred embodiment, the carbodiimide compound is selected from at least one of N,N'-di(2,6-diisopropylphenyl)carbodiimide, Stabaxol P, and Stabaxol P100; and / or the carbodiimide polymer is selected from at least one of poly[nitromethane tetranitro[2,4,6-tri(1-methylethyl)-1,3-phenylene]], Stabaxol P200, Stabaxol P400, Hymax 210, and Hymax 203.

[0023] Among them, the inventors have found through experiments that the use of polycarbodiimide anti-hydrolysis agents can more effectively avoid ester exchange chain scission occurring during the addition process, compared with monomeric carbodiimide anti-hydrolysis agents, and the effect is significantly better than that of using carbodiimide compounds.

[0024] In a preferred embodiment, based on 100 parts by weight of the monomer, the anti-hydrolysis agent accounts for 0.005 to 10 parts, and the metal deactivator accounts for 0.005 to 10 parts.

[0025] For example, based on 100 parts by weight of the monomer, the anti-hydrolysis agent is 0.005 parts, 0.008 parts, 0.01 parts, 0.02 parts, 0.05 parts, 0.08 parts, 1 parts, 2 parts, 4 parts, 6 parts, 8 parts or 10 parts, and the metal passivator is 0.005 parts, 0.008 parts, 0.01 parts, 0.02 parts, 0.05 parts, 0.08 parts, 1 parts, 2 parts, 4 parts, 6 parts, 8 parts or 10 parts.

[0026] In a further preferred embodiment, based on 100 parts by weight of the monomer, the anti-hydrolysis agent is 0.01 to 5 parts, and the metal deactivator is 0.01 to 2 parts.

[0027] The invention can effectively improve the thermal stability and hydrolysis resistance of polyester by introducing metal passivators and anti-hydrolysis agents. The anti-hydrolysis agent can effectively consume the acid in the chain decomposition process, can inhibit the ester bond breakage to a certain extent, and can also appropriately improve the thermal stability of the material.

[0028] In a preferred embodiment, the twin-screw extruder has 5 to 20 sections from the feed port to the die, preferably 8 to 16 sections, for example 8 sections, 9 sections, 10 sections, 11 sections, 12 sections, 13 sections, 14 sections, 15 sections or 16 sections.

[0029] In a further preferred embodiment, the temperature of each section from the second section to the die is controlled to be 140-300°C, preferably 150-280°C, for example, 140°C, 160°C, 180°C, 200°C, 220°C, 240°C, 260°C, 280°C or 300°C, and the temperature of each section (along the direction of material movement) increases successively.

[0030] In a further preferred embodiment, the temperature of the second stage is independently controlled to be 140-200°C, preferably 150-180°C; and / or the temperature of the die is controlled to be 210-300°C, preferably 220-260°C.

[0031] For example, the temperature of the second section is controlled to be 140°C, 150°C, 160°C, 170°C, 180°C, 190°C or 200°C; and / or the temperature of the die is controlled to be 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, 270°C, 280°C, 290°C or 300°C.

[0032] In a preferred embodiment, the residence time of the material in the twin-screw extruder is 0.5 to 60 minutes, preferably 0.5 to 20 minutes, more preferably 0.5 to 10 minutes, for example 0.5 minutes, 1 minute, 2 minutes, 4 minutes, 6 minutes, 8 minutes, 10 minutes, 12 minutes, 14 minutes, 16 minutes, 18 minutes or 20 minutes.

[0033] In a preferred embodiment, the preparation method comprises: (1) mixing a monomer, an initiator, a catalyst and an optional phosphite antioxidant to obtain component A, and mixing a metal passivator, an optional anti-hydrolysis agent and an optional hindered phenol antioxidant to obtain component B; (2) adding component A from the front section of a twin-screw extruder, and adding component B from the back section of the twin-screw extruder; (3) obtaining the degradable polyester through melt reaction and extrusion granulation.

[0034] In a preferred embodiment, in step (2), component A is added from any section before the 50% section (excluding the 50% section) of the twin-screw extruder, preferably component A is added from any section before the 30% section, and more preferably component A is added from any section before the 20% section, for example, the feed port (i.e., the first section).

[0035] In a further preferred embodiment, in step (3), component B is added from the 50% section and any section thereafter of the twin-screw extruder, preferably component B is added to any section in the 50% to 90% section, and more preferably component B is added to any section in the first 60 to 80% (e.g. 60 to 70%) section.

[0036] Along the material moving direction from front to back, there are sections of 0 to 100%.

[0037] In the process of preparing polyester by twin-screw extruder, different additives are added in stages to modify the polyester in situ: metal deactivators and anti-hydrolysis agents are added in situ in the latter stage of the reaction to improve the stability of the polyester; auxiliary antioxidants are added together with the reaction monomers in the front stage of the extruder to improve the efficiency of the polymerization process. By introducing additives in situ during the polymerization process for modification, thermal degradation caused by residual catalysts can be effectively suppressed, and thermal degradation caused by secondary processing can also be avoided.

[0038] The second object of the present invention is to provide a degradable polyester, such as polyglycolide, obtained by the preparation method described in the first object of the present invention. The degradable polyester has high thermal stability against hydrolysis.

[0039] In a preferred embodiment, the molecular weight of the degradable polyester is greater than 180,000, preferably 180,000-220,000, more preferably 180,000-200,000, for example, 180,000, 185,000, 190,000, 195,000, 200,000, 205,000, 210,000, 215,000 or 220,000.

[0040] In a preferred embodiment, the temperature of the degradable polyester at 5% thermal weight loss is 300-380°C, preferably 300-360°C.

[0041] The temperature of 5% thermal weight loss of the degradable polyester is at least 25° C. higher than that of common polyglycolide.

[0042] In a preferred embodiment, after the degradable polyester is placed in water at 37° C. for 11 days, the tensile strength retention rate is above 40%, preferably above 60%, for example, 40%, 45%, 50%, 55% or 60%.

[0043] The endpoints and any values ​​of the scope disclosed in the present invention are not limited to the precise scope or value, and these scopes or values ​​should be understood to include values ​​close to these scopes or values. For numerical ranges, the endpoint values ​​of each scope, the endpoint values ​​of each scope and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in this article. Hereinafter, in principle, each technical solution can be combined with each other to obtain a new technical solution, which should also be regarded as specifically disclosed in this article.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] (1) In the process of preparing polyester by continuous reaction extrusion polymerization, the metal passivator is introduced in situ, which can suppress the thermal decomposition problem caused by the residual catalyst in the degradable polyester in subsequent applications, and at the same time avoid the thermal degradation caused by secondary processing, thereby further improving the stability.

[0046] (2) In the present invention, during the reaction extrusion process, the metal deactivator and the anti-hydrolysis agent are introduced in situ at the end of the extruder, which can effectively avoid the inhibition of the catalyst activity by the metal deactivator and the anti-hydrolysis agent during the polymerization process, thereby increasing the molecular weight of the final polymerized polyester and reducing the residual monomer content. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 The torque-time diagrams of Examples 1-2 and Comparative Example 1 are shown;

[0048] Figure 2 The changes in mechanical properties during the hydrolysis aging process accelerated by different anti-hydrolysis agents PGA are shown. DETAILED DESCRIPTION

[0049] The present invention is described in detail below in conjunction with specific embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the contents of the present invention still fall within the scope of protection of the present invention.

[0050] It should also be noted that the various specific technical features described in the following specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0051] In addition, the various embodiments of the present invention may be arbitrarily combined as long as they do not violate the concept of the present invention. The technical solutions thus formed belong to part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0052] The raw materials used in the examples and comparative examples, unless otherwise specified, are disclosed in the prior art, for example, they can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0053] The test instruments and test conditions used in the examples are as follows:

[0054] Melt index (MFR) determination method: According to ISO 1133 standard, Lloyd Davenport MFI-10 / 230 melt index meter is used for determination, barrel temperature is 150°C, weight load is 2.16kg, die diameter is 2.095mm, length is 8mm, preheating time is 4min, automatic sample cutting is performed at set intervals, and the average value is calculated for 5 times. The measurement result is expressed in grams per 10 minutes (g / 10min).

[0055] Thermal performance analysis (DSC): The test was carried out on a Discovery series differential scanning calorimeter (DSC) produced by TA Instruments, and the processing software was TA Instruments Trios version 3.1.5. The DSC instrument was equipped with a Refrigerated Cooling System 90 mechanical refrigeration accessory. The test atmosphere was 50mL / min of nitrogen, and the sample amount required for the test was 5-10mg. The test procedure is as follows: first stabilize the temperature at 40°C, then increase the temperature to 220°C at 10°C / min and keep it constant for 1min to remove the thermal history, then cool down to -50°C at 10°C / min and keep it constant for 1min, and then increase the temperature to 220°C at 10°C / min. Record the cooling process and the second heating process to study the thermal properties of the sample. Through the DSC test, the software can directly derive the crystallization temperature ("T c ”), melting temperature (“T m ”), glass transition (“T g ”), thermal enthalpy change (“H”), etc.

[0056] Thermogravimetric test (TGA): The test was conducted on the Discovery series thermogravimetric analyzer of THERMAL ANALYSIS, and the processing software was TAInstruments Trios 3.1.4. Before the test, the machine was turned on and preheated to a temperature of about 40°C in the balance cavity. During the test, 5 to 10 mg of sample was weighed and placed in a ceramic crucible. The test was conducted in an air atmosphere with a flow rate of 20 mL / min. The temperature rise range was 50 to 600°C, and the heating rate was 10°C / h. The weight loss curve of the sample was recorded.

[0057] Gel Permeation Chromatography (GPC): The test instrument was PL-GPC50 gel permeation chromatograph from Angilent, USA, and the processing software was GPC offline. During the test, the mobile phase was hexafluoroisopropanol containing 5mmol / L sodium trifluoroacetate, the flow rate was 1mL / min, the column temperature was 40℃, the injection volume was 100μL, the standard sample was PMMA, and the sample concentration was 1mg / mL.

[0058] Tensile test: The sample was injected into 5A tensile specimen (thickness: 2mm) on HAAKE MiniJet micro-injection molding machine according to GB / T 1040.2-2006, the barrel temperature and mold temperature were 240℃ and 50℃, the injection pressure and time were 400bar and 5s, the holding pressure and time were 100bar and 10s. Then the tensile test was carried out on the 3344 material testing machine of Instron Company of the United States, the tensile rate was 50mm / min, and the clamp spacing was 50mm.

[0059] Accelerated hydrolysis test: The injection molded PGA specimens were placed in a constant temperature water bath at 37°C, and samples were taken at regular intervals to measure their molecular weight and mechanical properties by GPC.

[0060] 2,4-diisocyanate-1,3,5-tri(1-methylethyl)benzene homopolymer was purchased from Aladdin Reagent; N,N'-bis(2,6-diisopropylphenyl)carbodiimide was purchased from Shanghai Puzhan Technology; metal passivator AX71 was purchased from Shanghai Puzhan Technology; phosphite metal passivator THP was purchased from Aladdin Reagent; metal passivator TMC was purchased from Shanxi Chemical Research Institute; metal passivator XL-1 was purchased from Aladdin Reagent; metal passivator MD 1024 was purchased from BASF.

[0061] [Comparative Example 1]

[0062] Glycolide (GA), stannous octoate, and 1,4-butanediol were mixed uniformly in a mass ratio of 100:0.1:0.05:0.5, and then added to the MiniLabHAAKE MiniLab II micro extruder (conical co-rotating twin screws, with a maximum screw diameter of about 7 mm) produced by ThermoScientific in the United States. The extruder has a temperature module from the feed and is equipped with a sensor for real-time monitoring of the reaction torque. The reaction temperature was set to 220°C, the speed was 40 rpm, the reaction time was 7 minutes, and the torque-time data during the reaction was recorded.

[0063] [Example 1]

[0064] Glycol (GA), stannous octoate, 1,4-butanediol, and antioxidant 608 were mixed uniformly in a mass ratio of 100:0.1:0.05:0.5, and then added to the MiniLabHAAKE MiniLab II micro extruder (conical co-rotating twin screws, the maximum screw diameter is about 7 mm) produced by ThermoScientific in the United States. The extruder has a temperature module from the feed and is equipped with a sensor for real-time monitoring of the reaction torque. The reaction temperature was set to 220°C, the speed was 40rpm, the reaction time was 7 minutes, and the torque-time data during the reaction was recorded.

[0065] [Example 2]

[0066] Glycol (GA), stannous octoate, 1,4-butanediol, and antioxidant 168 were mixed uniformly in a mass ratio of 100:0.1:0.05:0.5, and then added to the MiniLabHAAKE MiniLab II micro extruder (conical co-rotating twin screws, the maximum screw diameter is about 7 mm) produced by ThermoScientific in the United States. The extruder has a temperature module from the feed and is equipped with a sensor for real-time monitoring of the reaction torque. The reaction temperature was set to 220°C, the speed was 40rpm, the reaction time was 7 minutes, and the torque-time data during the reaction was recorded.

[0067] The torque-time diagrams of Example 1-2 and Comparative Example 1 are as follows: Figure 1 As shown, it can be seen that both antioxidant 608 and antioxidant 168 can effectively increase the torque of the final reaction and obtain a polymer material with a higher molecular weight. The final torque after reaching equilibrium after adding 608 or 168 is significantly higher than that of Comparative Example 1. Compared with antioxidant 168, the addition of antioxidant 608 can significantly increase the reaction rate of glycolide at a low residence time, and the reaction torque within 0-4 minutes is significantly higher, which is more suitable for a twin-screw polymerization reaction system with a residence time of 3-5 minutes.

[0068] [Example 3-5]

[0069] Glycol (GA), stannous octoate, 1,4-butanediol, and antioxidant 608 were mixed uniformly in a mass ratio of 100:0.1:0.05:0.5, and then added to a ZE25Ax56D-UTX1 co-rotating twin-screw extruder (screw diameter 25 mm, L / D = 40) from Krauss Maffei, Germany, for extrusion granulation. The extruder has 11 sections from the feed port to the die, numbered 1-11, of which the first section (feed port) only serves to add materials and cannot be heated. The temperatures of sections 2-11 of the extruder are 160°C, 200°C, 220°C, 220°C, 220°C, 220°C, 230°C, 235°C, and 240°C, respectively. The feed rate is 15kg / h and the screw speed is 100rpm. In the 8th section of the extruder, according to 100 parts by mass of GA, different amounts of metal passivator AX71 were added in Examples 3-5, and other feeding conditions were controlled to be the same (Example 3: 0.5 parts, Example 4: 1 parts, Example 5: 2 parts), and mixed with 1 part of primary antioxidant 1010 and added through side feeding, and the feeding rates were 223g / h, 298g / h, and 447g / h, respectively. The residence time of the material in the twin-screw extruder was about 2-5min.

[0070] [Example 6]

[0071] The other synthesis methods were controlled to be the same as those in Example 1. In the 8th section of the twin-screw extruder, 0.5 parts of metal passivator MD 1024 and 1 part of primary antioxidant 1010 were added by side feeding based on 100 parts by mass of GA, and the feeding rate was 223 g / h. The residence time of the materials in the twin-screw extruder was about 2-5 minutes. Other conditions were the same as those in Example 1.

[0072] [Example 7]

[0073] The other synthesis methods were controlled to be the same as those in Example 1. In the 8th section of the twin-screw extruder, 0.5 parts of metal passivator XL-1 and 1 part of primary antioxidant 1010 were added by side feeding based on 100 parts by mass of GA at a feeding rate of 223 g / h. Other conditions were the same as those in Example 1.

[0074] [Example 8]

[0075] The other synthesis methods were controlled to be the same as those in Example 1. In the 8th section of the twin-screw extruder, 0.5 parts of metal passivator TMC 300 and 1 part of primary antioxidant 1010 were added by side feeding based on 100 parts by mass of GA, and the feeding rate was 223 g / h. The residence time of the material in the twin-screw extruder was about 2-5 min. The other conditions were the same as those in Example 3.

[0076] [Example 9]

[0077] The other synthesis methods are controlled to be the same as those in Example 1. In the 8th section of the twin-screw extruder, 0.5 parts of phosphite metal passivator THP and 1 part of primary antioxidant 1010 are added by side feeding based on 100 parts by mass of GA, and the feeding rate is 223 g / h. The residence time of the material in the twin-screw extruder is about 2-5 minutes. Other conditions are the same as those in Example 3.

[0078] [Comparative Example 2]

[0079] The other synthesis methods were controlled to be the same as those in Example 1. In the 8th section of the twin-screw extruder, 1 part of the primary antioxidant 1010 was added by side feeding based on 100 parts by mass of GA, without metal passivator, and the feeding rate was 149 g / h. Other conditions were the same as those in Example 1.

[0080] [Example 10]

[0081] The other synthesis methods are controlled to be the same as those in Example 1, except that: in the 8th section of the twin-screw extruder, based on 100 parts by mass of GA, 0.1 parts of metal passivator AX71 and 1 part of primary antioxidant 1010 are added through side feeding, and 0.5 parts of polymeric anti-hydrolysis agent 2,4-diisocyanate-1,3,5-tri(1-methylethyl)benzene homopolymer are added at a feeding rate of 238 g / h.

[0082] [Example 11]

[0083] The other synthesis methods are controlled to be the same as those in Example 1, except that: in the 8th section of the twin-screw extruder, based on 100 parts by mass of GA, 0.1 parts of metal passivator AX71 and 1 part of primary antioxidant 1010 are added through side feeding, and 0.5 parts of monomeric anti-hydrolysis agent N,N'-di(2,6-diisopropylphenyl)carbodiimide are added at a feeding rate of 238 g / h.

[0084] [Comparative Example 3]

[0085] Glycol (GA), stannous octoate, 1,4-butanediol, antioxidant 1010, and antioxidant 608 were mixed uniformly in a mass ratio of 100:0.1:0.05:1:0.5, and then added to a ZE25Ax56D-UTX1 co-rotating twin-screw extruder (screw diameter 25 mm, L / D = 40) from Krauss Maffei, Germany, for extrusion granulation. The extruder has 11 sections from the feed port to the die, numbered 1-11, of which the first section only serves to feed and cannot be heated. The temperatures of sections 2-11 of the extruder are 160°C, 200°C, 220°C, 220°C, 220°C, 220°C, 220°C, 230°C, 235°C, and 240°C, respectively. The feed rate is 15kg / h, and the screw speed is 100rpm. PGA particles are obtained by extrusion, cooling, and pelletizing.

[0086] The obtained PGA particles were premixed with the metal passivator AX-71 in a ratio of 100:0.5 and added into a twin-screw extruder (ZE25Ax56D-UTX1 from Krauss Maffei, Germany). The temperatures of sections 2-11 of the extruder were 160°C, 200°C, 220°C, 220°C, 220°C, 220°C, 230°C, 235°C and 240°C, respectively. The rotation speed was 150 rpm and the feeding rate was 5 kg / h.

[0087] [Comparative Example 4]

[0088] The other synthesis methods are controlled to be the same as those in Example 3. In the 8th section of the twin-screw extruder, 0.5 parts of polymeric anti-hydrolysis agent 2,4-diisocyanate-1,3,5-tri(1-methylethyl)benzene homopolymer and 1 part of primary antioxidant 1010 (without metal passivator) are added through side feeding according to 100 parts by mass of GA, and the feeding rate is 223 g / h. The residence time of the material in the twin-screw extruder is about 2-5 min. Other conditions are the same as those in Example 3.

[0089] [Example 12] DSC test

[0090] The polyglycolide compositions obtained in Examples 1 to 11 and Comparative Examples 1 to 2 were subjected to a scanning calorimetry (DSC) test, and the crystallization temperature (T c ), crystallization enthalpy (△H c ) and the melting temperature of the second heating process (T m ), melting enthalpy (△H m )See Table 2.

[0091] Table 1 DSC results of Examples 1 to 8 and Comparative Examples 1 to 2

[0092]

[0093] As shown in Table 1, it can be seen that after adding various additives, compared with Comparative Example 2, the crystallization temperature and crystallization enthalpy did not change significantly, indicating that the addition of additives will not significantly change the crystallization properties of PGA. m , melting enthalpy ΔH m It is significantly larger, indicating that the addition of polymeric anti-hydrolysis agent helps to improve the crystallization properties of PGA, making it more crystallinity and better thermal stability.

[0094] [Example 13] Thermal stability of modified particles: molecular weight, Td5%, melt index

[0095] The polyglycolide obtained in Examples 1 to 7 and Comparative Examples 2 to 4 was subjected to GPC, thermogravimetric and melt index tests, respectively, to verify the thermal stability of the modified PGA particles, and the results are shown in Table 2. The polyglycolide obtained in Examples 3 to 5 and Comparative Examples 2 to 4 was subjected to melt index tests, as shown in Table 3.

[0096] Table 2

[0097]

[0098] It can be seen from Table 2 that:

[0099] (1) The molecular weight of the polyester obtained in the embodiment of the present invention is above 180,000, which is higher than that of comparative examples 2 to 4; in particular, comparing embodiment 3 with comparative example 3, for different adding methods, the molecular weight of the polymer can be increased by adding the auxiliary agent to the end of the extruder through the "one-step method" during the synthesis process, and its weight average molecular weight is 187,064 g / mol, which is significantly higher than the weight average molecular weight of PGA after secondary processing of 156,743 g / mol.

[0100] (2) The 5% thermal decomposition temperature of Example 3-11 is also higher than that of Comparative Example 2, indicating that the metal passivator can effectively improve the thermal stability of the material. Among them, the 5% thermal decomposition temperature of Example 3 reaches 351°C, which is 57.8°C higher than that of Comparative Example 2. And further increasing the content of AX71, its thermal stability is further improved, indicating that AX71 can significantly improve the thermal stability of subsequent processing of the material. Comparing Example 3 with Comparative Example 3, for different addition methods, adding the auxiliary agent to the end of the extruder through the "one-step method" during the synthesis process can increase the 5% thermal decomposition temperature of the polymer by about 7.5°C.

[0101] Table 3

[0102]

[0103] It can be seen from Table 3 that the melt index of Examples 3 to 5 is significantly lower than that of Comparative Examples 2 to 4, indicating that the materials have higher melt strength and molecular chain length, and that the technical solution of the present invention can effectively improve the processing stability of the material.

[0104] [Example 14] Anti-hydrolysis performance after adding anti-hydrolysis agent

[0105] The polyglycolide obtained in Example 3, Example 10, and Example 11 was injection molded into dumbbell-shaped specimens, and the accelerated hydrolysis performance test was carried out in a constant temperature water bath at 37°C. Three specimens were taken out at regular intervals, and their mechanical properties were measured and the average value was taken. The obtained mechanical property retention rate changes with time as shown in Figure 2 As shown, Figure 2 As shown, after aging for ten days, the retention rate of breaking strength of Example 3 without adding anti-hydrolysis agent decreased significantly, and was only 31% of that before aging. Compared with different anti-hydrolysis agents, the polymeric anti-hydrolysis agent had better effect, and the retention rate was still 62% after aging for 10 days. The retention rate of the monomeric anti-hydrolysis agent after aging for ten days was slightly better than that of the unmodified PGA, which was 40%.

[0106] According to the embodiment of the present invention, the polymeric anti-hydrolysis agent has a significantly better anti-hydrolysis effect on PGA than the monomeric anti-hydrolysis agent, which may be because the polymeric anti-hydrolysis agent and PGA are tightly bound by hydrogen bonds and are evenly distributed. The lasting effect is longer during the use of PGA, while the monomeric anti-hydrolysis agent is easily detached from PGA, resulting in failure during use. As a result, the monomeric anti-hydrolysis agent has a worse effect.

[0107] It can be seen from the above test results that in the present invention, the use of metal passivators can effectively improve the thermal stability of PGA during use and processing, while polymeric anti-hydrolysis agents can effectively improve the hydrolysis resistance of PGA. In addition, the side feed is added to the end of the extruder through the "one-step method" during the synthesis process, which can effectively avoid thermal decomposition in the later secondary processing and increase its weight average molecular weight.

[0108] The present invention has been described in detail above in conjunction with specific implementations and exemplary examples, but these descriptions cannot be understood as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, a variety of equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its implementation methods, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing degradable polyester, include: The monomer, initiator, catalyst, metal deactivator, optional anti-hydrolysis agent and optional antioxidant are melt-mixed and reacted in a twin-screw extruder, and then extruded and granulated to obtain the degradable polyester.

2. The preparation method according to claim 1, It is characterized in that The monomer is selected from at least one of methyl glycolate and / or its derivatives, glycolic acid and / or its derivatives, glycolide and / or its derivatives, lactide and / or its derivatives, caprolactone and / or its derivatives; and / or, The initiator is selected from small molecule substances containing hydroxyl groups with a boiling point greater than 160° C., preferably at least one selected from ethylene glycol, butanediol, glycerol, serinol, leucinol, pentaerythritol, sorbitol, xylitol, amino acids, phenol, hydroquinone, resorcinol, and benzyl alcohol.

3. The preparation method according to claim 1, It is characterized in that The catalyst is selected from at least one of the salt compounds corresponding to one or more elements of group IIA, IIIA, IVA, VA, IVB, VIIB, VIII, and IIB metal elements, and organic guanidine compounds. Preferably, the catalyst is selected from at least one of the salt compounds corresponding to one or more elements of Sn, Bi, Mg, Al, Ca, Fe, Mn, Ti, and Zn.

4. The preparation method according to claim 1, It is characterized in that The antioxidant is selected from one or more combinations of hindered phenol antioxidants and phosphite antioxidants; preferably, the hindered phenol antioxidant is selected from at least one of antioxidant 1010, antioxidant 1024, antioxidant 1076, and antioxidant 1078, and / or the phosphite antioxidant is selected from at least one of antioxidant 168, antioxidant 608, antioxidant 626, and antioxidant TP80.

5. The preparation method according to claim 1, It is characterized in that The metal passivator is selected from at least one of oxalic acid derivatives, salicylic acid derivatives, hydrazide compounds, alkyl phosphates, benzotriazole compounds, and guanidine compounds, and is preferably selected from at least one of the following products: BASF Chel-180, BASF Irganox MD1024, Eastman OABH, Naugard XL-1, Naugard MD24, ADEKASTAB CDA-1, and ADEKA STAB AX71.

6. The preparation method according to claim 1, It is characterized in that The anti-hydrolysis agent is a carbodiimide anti-hydrolysis agent; Preferably, the anti-hydrolysis agent is selected from carbodiimide polymers and / or carbodiimide compounds; More preferably, the carbodiimide compound is selected from at least one of N,N'-di(2,6-diisopropylphenyl)carbodiimide, Stabaxol P, and Stabaxol P100; and / or the carbodiimide polymer is selected from at least one of poly[nitromethane tetranitro[2,4,6-tri(1-methylethyl)-1,3-phenylene]], Stabaxol P200, Stabaxol P400, Hymax 210, and Hymax 203.

7. The preparation method according to claim 1, It is characterized in that Based on 100 parts by weight of the monomer, the initiator is 0.005-5 parts, the catalyst is 0.005-1 parts, the antioxidant is 0.005-10 parts, the anti-hydrolysis agent is 0.005-10 parts, and the metal passivator is 0.005-10 parts; preferably, the initiator is 0.01-1 parts, the catalyst is 0.01-0.5 parts, the antioxidant is 0.01-5 parts, the anti-hydrolysis agent is 0.01-5 parts, and the metal passivator is 0.01-2 parts.

8. The preparation method according to any one of claims 1 to 7, It is characterized in that The twin-screw extruder has 5 to 20 sections from the feed port to the die, preferably 8 to 16 sections; preferably, the temperature of each section from the second section to the die is independently controlled to be 140 to 300° C., preferably 150 to 280° C.; and / or, The residence time of the material in the twin-screw extruder is 0.5 to 60 minutes, preferably 0.5 to 20 minutes.

9. The preparation method according to claim 8, It is characterized in that The preparation method comprises: (1) mixing a monomer, an initiator, a catalyst and an optional phosphite antioxidant to obtain component A, and mixing a metal deactivator, an optional anti-hydrolysis agent and an optional hindered phenol antioxidant to obtain component B; (2) adding component A from the front section of a twin-screw extruder, and adding component B from the back section of the twin-screw extruder; and (3) obtaining the degradable polyester through melt reaction and extrusion granulation.

10. The preparation method according to claim 9, It is characterized in that In step (2), Add the component A from any section before the 50% section of the twin-screw extruder, preferably add the component A from any section before the 30% section; and / or, The component B is added from the 50% section and any section thereafter of the twin-screw extruder, preferably any section from 50% to 90%.

11. The degradable polyester obtained by the preparation method according to any one of claims 1 to 10.

12. The degradable polyester according to claim 11, It is characterized in that The molecular weight of the degradable polyester is greater than 180,000, preferably 180,000 to 220,000; and / or, The temperature of the degradable polyester at 5% thermal weight loss is 300-380° C., preferably 300-360° C.; and / or, After the degradable polyester is placed in water at 37° C. for 11 days, the tensile strength retention rate is above 40%, preferably above 60%.

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