High-temperature-resistant PGA degradable material and preparation method thereof

Abstract

The invention discloses a high-temperature-resistant PGA degradable material and a preparation method thereof, and belongs to the technical field of preparation of high-temperature-resistant polyglycolic acid (PGA). The preparation method comprises the following steps: carrying out an esterification reaction I on a mixed solution containing raw materials and a catalyst until the mixed solution is clear and transparent, then adding a branching aid, and carrying out an esterification reaction II and a condensation polymerization reaction in sequence to obtain the high-temperature-resistant PGA degradable material, the raw material is glycollic acid and / or glycollate; the branched chain auxiliary agent contains a phosphorus branched chain auxiliary agent. According to the invention, the phosphorus-containing branched chain auxiliary agent is selected and used, so that the thermal decomposition temperature of the PGA is greatly increased, the PGA can obtain an excellent color value, the processing window of the PGA is widened, and the product quality is improved.

Description

Technical Field

[0001] This application relates to a high-temperature resistant PGA biodegradable material and its preparation method, belonging to the field of high-temperature resistant polyglycolic acid (PGA) preparation technology. Background Technology

[0002] Polyglycolic acid (PGA) is a biopolymer material with excellent biodegradability and biocompatibility. It is currently the best-performing polyester material known for its degradation performance and is primarily used in medical sutures, fracture fixation materials, tissue engineering scaffolds, drug-controlled release carriers, and suture reinforcement. PGA rapidly degrades into harmless water and CO2 in living organisms, compost, and marine environments, making it significant for addressing the serious problem of plastic pollution. Furthermore, PGA's high tensile strength and gas barrier properties effectively overcome the shortcomings of traditional biodegradable plastics. However, limitations in traditional PGA production technology result in low production capacity and high costs, significantly restricting its promotion and application. Currently, PGA preparation mainly includes ring-opening polymerization and direct condensation polymerization. While more research has been conducted on ring-opening polymerization, the raw material, glycolide, requires complex preparation processes, is difficult to purify, has high costs, and a long process flow, leading to high production costs and the potential for heavy metal residues in the finished product. However, ring-opening polymerization produces PGA with a higher molecular weight. Direct condensation polymerization primarily utilizes glycolic acid or glycolate as raw materials for direct dehydration or dealcoholization. Compared to ring-opening polymerization, direct condensation polymerization has a shorter process flow, simpler operation, and lower synthesis cost, making it more suitable for industrial production. However, when preparing polyglycolic acid (PGA) through direct polymerization of glycolic acid and methyl glycolate, the high viscosity of the system prevents the rapid removal of small water or methanol molecules generated from the reaction system, resulting in a low molecular weight and low mechanical strength of the polymer, thus affecting its applications. Although existing technologies have reported methods for preparing high molecular weight PGA using glycolic acid and methyl glycolate, even high molecular weight PGA exhibits poor heat resistance; the 5% mass thermal loss (Td5%) is only around 270 °C. Severe thermal degradation occurs when the processing temperature exceeds the melting point, leading to a significant reduction in the molecular weight of PGA and making it difficult to process and mold. Therefore, developing low-cost synthesis methods and specialized materials for preparing high-molecular-weight, high-heat-resistant PGA, and addressing the major drawbacks of PGA such as low thermal decomposition temperature and narrow processing window, is of great significance for the application of PGA as a general-purpose biodegradable polymer material. Summary of the Invention

[0003] To address the issues of low thermal decomposition temperature, easy thermal degradation, and narrow processing window in existing polyglycolic acid (PGA) technologies, this application provides a technical solution for a high-temperature resistant biodegradable PGA material. By selecting and using a type of phosphorus-containing branching agent, the thermal decomposition temperature of PGA is significantly increased, while also enabling PGA to obtain excellent color values, thus broadening the processing window of PGA and improving product quality.

[0004] The technical solution adopted in this application is as follows: According to a first aspect of this application, a method for preparing a high-temperature resistant PGA biodegradable material is provided, comprising the following steps: An esterification reaction I is carried out on a mixture containing raw materials and catalyst until the mixture becomes clear and transparent. Then, a branching agent is added and esterification reaction II and polycondensation reaction are carried out in sequence to obtain the high-temperature resistant PGA biodegradable material. The raw material is glycolic acid and / or glycolate; The branching aid is a phosphorus-containing branching aid.

[0005] Preferably, the phosphorus-containing branching aid is a multifunctional (phosphite) ester branching aid; Optionally, the phosphorus-containing branching aid is selected from at least one of triphenyl phosphate, trimethyl phosphate, triethyl phosphate, polyphosphoric acid, xylene-isooctyl phosphite, xylene-isodecyl phosphite, phenyl diisooctyl phosphite, phenyl diisodecyl phosphite, triisodecyl phosphite, trilauryl phosphite, tri(tetrazyl) phosphite, tri(dipolypropylene glycol) phosphite, pentaerythritol diisodecyl diphosphite, diphenyl phosphite, 4-4'-isopropylbis[di(C12 / 14 alkylphenyl phosphite)], and tetraphenyl dipropylene glycol diphosphite. Preferably, the phosphorus-containing branching aid is one or any combination of trimethyl phosphate, triethyl phosphate, xylene-isooctyl phosphite, tri(tetrazyl) phosphite, tri(dipolypropylene glycol) phosphite, or pentaerythritol diisodecyl diphosphite.

[0006] Through extensive experimental verification, the applicant discovered that using branching agents containing phosphate esters can solve the technical problems of this application. Phosphate ester compounds can interact with hydroxyl groups on the PGA molecular chain to form hydrogen bonds and ester bonds, enhancing intermolecular interactions and thus improving its thermal stability. The branched structure containing phosphate esters further enhances its entanglement with the PGA molecular chain, improving the thermal stability of PGA. Moreover, phosphorus can react with unsaturated bonds in PGA, reducing oxidation reactions and inhibiting yellowing of PGA.

[0007] Optionally, the amount of the branching agent is 1‰ to 50% wt of the amount of the raw material. The applicant found that dosages below this range could not achieve the desired technical effect, while dosages above this range would affect the PGA polymerization process and prevent the acquisition of PGA with the desired molecular weight.

[0008] Optionally, the amount of catalyst used is 0.01‰~0.5%wt of the amount of raw material. The catalyst is a general catalyst used for the polymerization of glycolic acid (methyl ester), and exemplarily, the catalyst is a zinc acetate catalyst. High catalyst activity, however, can lead to catalytic side reactions if used excessively, thus affecting the color of PGA.

[0009] Optionally, the conditions for the esterification reaction I include: an esterification temperature of 170~200 °C and an esterification pressure of atmospheric pressure.

[0010] Optionally, the esterification reaction I yields polyglycolic acid oligomers with a molecular weight of 500-2000 Da.

[0011] Optionally, the conditions for the esterification reaction II include: an esterification temperature of 200~220 °C, an esterification pressure of atmospheric pressure to 4000 Pa, and an esterification time of 10~90 min.

[0012] Optionally, the conditions for the polycondensation reaction include: a polycondensation temperature of 200~250℃, a polycondensation time of 3~10h, and a polycondensation pressure of 40~80 Pa.

[0013] Optionally, before the polycondensation reaction begins, the esterification pressure of the esterification reaction II is linearly increased to the polycondensation pressure.

[0014] According to a second aspect of this application, a high-temperature resistant PGA biodegradable material obtained by the aforementioned preparation method is provided, wherein the 5% mass thermogravimetric temperature Td of the high-temperature resistant PGA biodegradable material is... 5% The temperature range is 340~375 °C.

[0015] The beneficial effects of this application include: The method for preparing high-temperature resistant PGA biodegradable materials provided in this application uses a class of phosphorus-containing branching agents, which significantly increases the thermal decomposition temperature of PGA. At the same time, the prepared PGA has excellent color value, which broadens the processing window of PGA and improves the quality of the product. Attached Figure Description

[0016] Figure 1 In Example 2 of this application, TGA data of the synthesized PGA were obtained; Figure 2 The TGA curve for the commercialized PGA (Mn) of this application is shown. Detailed Implementation

[0017] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0018] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0019] Unless otherwise specified, all test methods are standard and all instrument settings are those recommended by the manufacturer.

[0020] The analysis and testing methods are as follows: The Td5% of PGA was determined using a TGA instrument. Measurements were performed under N2 protection conditions, with a temperature range from room temperature to 600 °C. The heating / cooling rate was 10 °C / min.

[0021] The color value (b-value) was determined according to Method A (drying and pulverizing method) 5.5 in GB / T14190-2017, using a D65 light source and a 10° viewing angle. The sample was placed in a forced-air drying oven, and the PGA slices were heated at 140℃ for 60 min. After cooling, the slices were pulverized and sieved to obtain particles ranging from 350 μm to 833 μm. The sieved sample particles were placed in a sample cup, ensuring a compact packing, and then placed on the measuring hole. The color value (L value and b-value) of the sample was measured at three points, rotating approximately 120° each time. The arithmetic mean of the three measurements was taken as the result, rounded to one decimal place according to GB / T8170.

[0022] Molecular weight was determined by gel permeation chromatography (GPC). (See reference method) Polymer 41 (2000)8725-8728) A Waters 1515 Isocratic HPLC Pump gel permeation chromatograph equipped with an HFIP 805 styrene-divinylbenzene copolymer gel column was used. HFIP containing 1 mM sodium trifluoroacetate was used as the eluent, and the temperature was 40℃. The molecular weight was calibrated according to polymethyl methacrylate (PMMA) standards. A good solvent for the polymer being tested (hexafluoroisopropanol was selected for this test) was used. The sample was fully dissolved in advance, with a sample concentration of 5 mg / mL. The sample was filtered through a 0.22 μm-0.45 μm PTFE membrane before the test. The injection volume was 100 μL, and the run time was 20 min.

[0023] According to one embodiment of this application, the preparation steps of the high-temperature resistant PGA biodegradable material include: directly mixing glycolic acid (ester) with a catalyst, first obtaining oligomeric polyglycolic acid by direct esterification, then adding a certain amount of phosphorus-containing branching agent, and continuing esterification (ester exchange) under high vacuum conditions to prepare a PGA biodegradable material with high temperature resistance.

[0024] In one embodiment, the phosphorus-containing branching agent is selected from, but not limited to, one or more of the following multifunctional ()phosphite branching agents: triphenyl phosphate, trimethyl phosphate, triethyl phosphate, polyphosphite, xylene-isooctyl phosphite, xylene-isodecyl phosphite, phenyl diisooctyl phosphite, phenyl diisodecyl phosphite, triisodecyl phosphite, trilauryl phosphite, tri(tridecyl) phosphite, tri(dipolypropylene glycol) phosphite, pentaerythritol diisodecyl diphosphite, diphenyl phosphite, 4-4'-isopropylbis[di(C12 / 14 alkylphenyl phosphite)], tetraphenyl dipropylene glycol diphosphite, etc., preferably trimethyl phosphate, triethyl phosphate, xylene-isooctyl phosphite, tri(tridecyl) phosphite, tri(dipolypropylene glycol) phosphite, and pentaerythritol diisodecyl diphosphite.

[0025] In one embodiment, the amount of the branching aid added is 1% to 50% of the mass of the polymerization raw material glycolic acid (methyl ester).

[0026] In one embodiment, the catalyst is a general-purpose catalyst used for the polymerization of glycolic acid (methyl ester), and the amount used is 0.01‰ to 0.5%wt of glycolic acid (ester).

[0027] In one embodiment, the 5% mass thermogravimetric temperature Td of the polymerized PGA biodegradable material is... 5% The temperature range is 340-375 °C.

[0028] In one embodiment, the polymerization reaction is divided into three stages: In the first stage, glycolic acid (methyl ester) and catalyst are polymerized at 170-200 °C to obtain polyglycolic acid oligomers with a molecular weight of 500-2000 Da; In the second stage, a branching agent is added to the above reaction system, and polymerization is carried out at 200-220 °C under vacuum conditions from atmospheric pressure to 4000 Pa for 10-90 min; In the third stage, the vacuum degree of the reaction system is gradually increased to 40-80 Pa, the polymerization reaction temperature is controlled at 200-250 °C, and polymerization is carried out for 3-10 hours to obtain high molecular weight PGA resin.

[0029] In one embodiment, the preparation of a high-temperature resistant PGA biodegradable material, using glycolic acid (methyl ester) as an example, is illustrated in Formula I.

[0030] Formula I.

[0031] Example 1 Take 1 mol of glycolic acid and add 0.3 mmol of zinc acetate catalyst. Under mechanical stirring at 200 °C, react at normal pressure until the solution is clear and transparent. Monitor the number average molecular weight of oligomeric PGA to reach 1000 Da. Add 23 g of trimethyl phosphate, raise the temperature of the reaction system to 210 °C, and apply a vacuum (4000 Pa). React for 1 h. Raise the polymerization temperature to 235 °C and gradually increase the vacuum of the polymerization system to 50 Pa. After polymerization for 5 hours, a white PGA product is obtained with a number average molecular weight of 57000 Da, a b value of 2.3, and a Td5% of 370 °C.

[0032] Example 2 1 mol of glycolic acid was added, along with 0.33 mmol of zinc acetate catalyst. The reaction was carried out at 200 °C under mechanical stirring and normal pressure until the solution became clear and transparent. The number-average molecular weight of the oligomeric PGA reached 1200 Da. 23 g of tridecyl phosphite was added, and the reaction system was heated to 210 °C and evacuated (4000 Pa). The reaction was carried out for 1 h, and the polymerization temperature was increased to 240 °C. The vacuum of the polymerization system was gradually increased to 50 Pa. After 6 hours of polymerization, a white PGA product was obtained with a number-average molecular weight of 54000 Da, a b-value of 2.1, and a Td5% of 375 °C.

[0033] Taking the high-temperature resistant PGA prepared in this embodiment as an example, it was compared with the commercial Macklin P909206 PGA (Mn=150000) and tested separately. It can be seen that the 5% thermal decomposition temperature is significantly improved.

[0034] Example 3 Take 1 mol of glycolic acid and add 0.3 mmol of zinc acetate catalyst. Under mechanical stirring at 200 °C, react at normal pressure until the solution is clear and transparent. Monitor the number average molecular weight of oligomeric PGA to reach 1000 Da. Add 30 g of triethyl phosphate, raise the temperature of the reaction system to 210 °C, and apply a vacuum (4000 Pa). React for 50 min. Increase the polymerization temperature to 240 °C and gradually increase the vacuum of the polymerization system to 50 Pa. Polymerize for 6 hours to obtain a white PGA product with a number average molecular weight of 50000 Da, b value of 2.7, and Td5% of 375 °C.

[0035] Comparative Example 1 Take 1 mol of glycolic acid and add 0.3 mmol of zinc acetate catalyst. Under mechanical stirring at 200 °C, react at normal pressure until the solution is clear and transparent. Monitor the number average molecular weight of oligomeric PGA to reach 1000 Da. Raise the temperature of the reaction system to 210 °C and apply a vacuum (4000 Pa). React for 1 h. Increase the polymerization temperature to 230 °C and gradually increase the vacuum of the polymerization system to 50 Pa. After polymerization for 5 hours, a brown PGA product is obtained with a number average molecular weight of 57000 Da, a b value of 10.2, and a Td5% of 265 °C.

[0036] Comparative Example 2 Take 1 mol of glycolic acid and add 0.3 mmol of zinc acetate catalyst. Under mechanical stirring at 200 °C, react at normal pressure until the solution is clear and transparent. Monitor the number average molecular weight of oligomeric PGA to reach 1000 Da. Add 30 g of tetraethyl orthosilicate. Heat the reaction system to 210 °C and apply a vacuum (4000 Pa). React for 1 h. Increase the polymerization temperature to 230 °C and gradually increase the vacuum of the polymerization system to 50 Pa. Polymerize for 5 hours to obtain a brown PGA product with a number average molecular weight of 51000 Da, b value of 11.7, and Td5% of 262 °C.

[0037] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing a high-temperature resistant, PGA biodegradable material, characterized in that, Includes the following steps: An esterification reaction I is carried out on a mixture containing raw materials and catalyst until the mixture becomes clear and transparent. Then, a branching agent is added and esterification reaction II and polycondensation reaction are carried out in sequence to obtain the high-temperature resistant PGA biodegradable material. The raw material is glycolic acid and / or glycolate; The branching aid is a phosphorus-containing branching aid.

2. The preparation method according to claim 1, characterized in that, The phosphorus-containing branching agent is selected from at least one of the following: triphenyl phosphate, trimethyl phosphate, triethyl phosphate, polyphosphoric acid, xylene isooctyl phosphite, xylene isodecanyl phosphite, phenyl diisooctyl phosphite, phenyl diisodecyl phosphite, triisodecyl phosphite, trilauryl phosphite, tri(tetrazyl) phosphite, tri(dipolypropylene glycol) phosphite, pentaerythritol diisodecyl diphosphite, diphenyl phosphite, 4-4'-isopropylbis[di(C12 / 14 alkylphenyl phosphite)], and tetraphenyl dipropylene glycol diphosphite.

3. The preparation method according to claim 1, characterized in that, The amount of the branching agent is 1‰ to 50% wt of the amount of the raw material.

4. The preparation method according to claim 1, characterized in that, The amount of catalyst used is 0.01‰~0.5%wt of the amount of raw material used.

5. The preparation method according to claim 1, characterized in that, The conditions for the esterification reaction I include: an esterification temperature of 170~200 °C and an esterification pressure of atmospheric pressure.

6. The preparation method according to claim 1, characterized in that, The esterification reaction I yields polyglycolic acid oligomers with molecular weights ranging from 500 to 2000 Da.

7. The preparation method according to claim 1, characterized in that, The conditions for the esterification reaction II include: an esterification temperature of 200-220 °C, an esterification pressure of atmospheric pressure to 4000 Pa, and an esterification time of 10-90 min.

8. The preparation method according to claim 1, characterized in that, The conditions for the polycondensation reaction include: a polycondensation temperature of 200~250℃, a polycondensation time of 3~10h, and a polycondensation pressure of 40~80 Pa.

9. The preparation method according to claim 8, characterized in that, Before the start of the polycondensation reaction, the esterification pressure of the esterification reaction II is linearly increased to the polycondensation pressure.

10. The high-temperature resistant PGA biodegradable material prepared by the preparation method according to any one of claims 1 to 9, characterized in that, The 5% mass thermogravimetric temperature Td of the high-temperature resistant PGA biodegradable material 5% The temperature range is 340~375 °C.

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