A low-acid-value long-acting bacteriostatic degradable polyester, a preparation method and application thereof

Abstract

The application provides a low-acid-value long-acting bacteriostatic degradable polyester and a preparation method and application thereof, and the method steps comprise: performing esterification reaction on terephthalic acid, adipic acid and butanediol to obtain an esterification product, and then performing pre-polycondensation reaction and final polycondensation reaction in sequence to prepare the polyester; wherein, a quaternary ammonium compound containing at least two hydroxyl groups is added in the early stage of the final polycondensation reaction. The quaternary ammonium compound containing at least two hydroxyl groups is added in the early stage of the final polycondensation reaction, the compound is chemically grafted with the carboxyl group of the polyester to introduce an antibacterial group and reduce the acid value of the product, and the quaternary ammonium group contained in the compound endows the material with antibacterial properties. The obtained PBAT has low acid value and long-acting antibacterial properties, and the performance defects of PBAT materials in the fields of one-time use such as food packaging and medical health, such as the lack of antibacterial effect or the physical blending of the material and the antibacterial agent and the short-lasting antibacterial effect, are well improved.

Description

Technical Field

[0001] This invention belongs to the field of polymer material synthesis, specifically relating to a low-acid-value, long-lasting antibacterial, biodegradable polyester, its preparation method, and its application. Background Technology

[0002] Currently, most disposable raw materials used in food packaging, medical and health fields are non-degradable materials such as polyethylene and polypropylene, which cause white pollution. Adhering to the principles of green and sustainable development, the development of biodegradable materials such as polybutylene adipate terephthalate (PBAT) has gained attention. However, there is relatively little research on developing products based on PBAT that possess excellent basic properties while also having antibacterial properties, to extend food shelf life and replace existing non-degradable plastic products in preventative medicine and other fields. Some studies, such as CN 115710409A, achieve antibacterial properties by blending PBAT with PLA and adding at least one of chitosan, nano-silver, and nano-zinc oxide as antibacterial agents, and CN 114907676A, which uses starch and polyguanidine bactericides added to the PBAT matrix material in the form of masterbatches. Both of these studies suffer from the drawback of physical blending of PBAT and bactericides, where bactericide leaching occurs during later use, leading to a decrease in antibacterial efficacy. In addition, excessively high acid values ​​in PBAT products can cause PBAT to degrade too quickly, failing to meet usage requirements.

[0003] Therefore, how to make PBAT have long-lasting antibacterial effect while having a low acid value to ensure its durability has become an urgent problem to be solved in this field. Summary of the Invention

[0004] To address the aforementioned problems in the existing technology, the present invention aims to provide a low-acid-value, long-lasting antibacterial, biodegradable polyester and its preparation method. The method involves adding a quaternary ammonium compound containing at least two hydroxyl groups in the early stage of the final polycondensation stage of polybutylene adipate / terephthalate (PBAT). The synthesis process of PBAT is a publicly disclosed method in the prior art. The method of the present invention is applicable to any PBAT preparation process including a final polycondensation reaction stage.

[0005] In the process of melt condensation polymerization to form PBAT, this invention adds a quaternary ammonium compound containing at least two hydroxyl groups in the early stage of the final condensation stage of polyester. This compound reacts with the carboxyl groups in the polyester to chemically graft antibacterial groups while reducing the acid value of the product, and the quaternary ammonium groups it contains endow the material with antibacterial properties.

[0006] To achieve the above-mentioned objectives, the technical solution adopted by the present invention is as follows:

[0007] This invention provides a method for preparing a low-acid-value, long-lasting antibacterial, and biodegradable polyester. The method includes esterifying terephthalic acid, adipic acid, and butanediol to obtain an esterified product, followed by a pre-condensation reaction and a final condensation reaction to obtain the polyester.

[0008] In this process, a quaternary ammonium compound containing at least two hydroxyl groups is added in the early stage of the final polycondensation reaction. Preferably, the quaternary ammonium compound contains two to three hydroxyl groups.

[0009] In this invention, a quaternary ammonium compound containing at least two hydroxyl groups is added in the early stage of the final polycondensation reaction. The early stage refers to the first 2-25% of the total time of the final polycondensation reaction. This invention divides the final polycondensation reaction time into three stages: early stage, middle stage, and late stage. According to general understanding, the early stage generally refers to the first 0-30%, not exceeding the first 1 / 3 of the time period, and the remaining time period is the middle and late stages of the reaction.

[0010] Preferably, the total time for the final polycondensation reaction is 2-4 hours, wherein the initial stage refers to 4-60 minutes after the start of the final polycondensation reaction, preferably 5-30 minutes.

[0011] In this invention, the quaternary ammonium compound containing at least two hydroxyl groups has the structure shown in formula (1):

[0012]

[0013] In formula (1), X is a halogen or acid radical, and the acid radical is selected from sulfate, phosphate, and nitrate.

[0014] R1, R2, R3, and R4 each independently represent substituents of arbitrary structure and are not H. The total number of hydroxyl groups contained on the substituents represented by R1, R2, R3, and R4 is at least 2, preferably 2-3.

[0015] R1, R2, R3, and R4 can be the same or different.

[0016] In some specific embodiments of the present invention, R1, R2, R3, and R4 are independently represented as -R-(OH)n, wherein R is selected from alicyclic substituents of C3-C60 with or without heteroatoms, aliphatic hydrocarbon groups of C1-C60, and alkyl groups of C1-C25, wherein the heteroatoms are O or N, n≥0 and the sum of n in R1, R2, R3, and R4 is not less than 2; preferably, R is an alkyl group of C1-C3 or an aliphatic hydrocarbon group of C12-C18; preferably, the sum of n is 2-3.

[0017] In some specific embodiments of the present invention, R1, R2, R3, and R4 contain at least one C12-C18 aliphatic hydrocarbon group.

[0018] In some specific embodiments of the present invention, the quaternary ammonium compound containing at least two hydroxyl groups is selected from quaternary ammonium compounds containing C3-C60 alicyclic substituents and quaternary ammonium compounds containing C1-C25 alkyl chains, preferably one or more of polyquaternary ammonium salt-10, chitosan quaternary ammonium salt, dodecyl dihydroxyethyl methyl ammonium chloride, quaternary ammonium salt-16, and 2,3-dihydroxypropyl-trimethyl ammonium chloride, more preferably one or more of quaternary ammonium salt-16 and dodecyl dihydroxyethyl methyl ammonium chloride.

[0019] In some specific embodiments of the present invention, the preparation method of the low-acid-value, long-lasting antibacterial, and biodegradable polyester includes the following steps:

[0020] S1: Esterification reaction of terephthalic acid, adipic acid, butanediol and catalyst;

[0021] S2: After the esterification reaction is completed, the temperature is raised to carry out the pre-condensation reaction;

[0022] S3: After the pre-condensation reaction is completed, the final condensation reaction is carried out. In the early stage of the final condensation reaction, a quaternary ammonium compound containing at least two hydroxyl groups is added to obtain a low-acid-value, long-lasting antibacterial and biodegradable polyester.

[0023] In this invention, the molar ratio of the total amount of terephthalic acid and adipic acid to butanediol in S1 is 1:(1.1-1.5);

[0024] Preferably, the molar ratio of terephthalic acid to adipic acid is (45-50):(55-50).

[0025] In this invention, the catalyst in S1 is selected from titanium-based catalysts, preferably one or more of titanium dioxide, tetrabutyl titanate, isopropyl titanate, tetraisopropyl titanate, tetraisobutyl titanate, tetraisooctyl titanate, titanium citrate, titanium tartrate, titanium ethylene glycol, titanium propylene glycol, and titanium butanediol.

[0026] Preferably, the catalyst is a titanium-based catalyst, and the amount of the catalyst used, calculated by the mass of titanium element, is 50-200 ppm of the total mass of terephthalic acid, adipic acid and butanediol.

[0027] In this invention, the esterification reaction described in S1 is carried out under normal pressure or slightly reduced pressure, preferably at a pressure of 40-80 kPa.

[0028] Preferably, the esterification reaction is carried out at a temperature of 190-230℃, more preferably 190-220℃, and for a time of 2-3 hours, more preferably 2-2.5 hours.

[0029] Preferably, the esterification reaction is carried out under the protection of an inert gas, which is selected from nitrogen and argon, with nitrogen being preferred.

[0030] In this invention, the pre-condensation reaction described in S2 is carried out at a pressure of 3-8 kPaA;

[0031] Preferably, the pre-condensation reaction is carried out at a temperature of 230-245°C, more preferably 230-235°C, and for a reaction time of 30-90 min, more preferably 30-50 min.

[0032] In this invention, the final polycondensation reaction described in S3 is carried out at a pressure of 5-100 PaA;

[0033] Preferably, the final polycondensation reaction is carried out at a temperature of 230-245℃, more preferably 230-235℃, and for a reaction time of 2-4 hours, more preferably 2-3 hours.

[0034] In this invention, the amount of the quaternary ammonium compound containing at least two hydroxyl groups added in S3 is 0.02-1.2% of the total mass of terephthalic acid, adipic acid and butanediol in S1, preferably 0.02-0.8%.

[0035] In this invention, S3 refers to the initial stage of the reaction, where the initial stage refers to the first 2-25% of the total time of the final polycondensation reaction;

[0036] Preferably, the total time for the final polycondensation reaction is 2-4 hours, wherein the initial stage refers to 4-60 minutes after the start of the final polycondensation reaction, preferably 5-30 minutes.

[0037] In this invention, after adding the quaternary ammonium compound containing at least two hydroxyl groups in step S3, the atmospheric pressure valve is closed and stirring is started. Stirring is performed for 3-15 minutes, and then the vacuum is restored. It is preferable to stir for 3-15 minutes after adding the compound and closing the atmospheric pressure valve. If the stirring time is too short, the dispersion will be uneven; if the stirring time is too long, energy consumption will increase costs. Additionally, excess 1,4-butanediol and some of the hydroxyl groups in the compound will etherify, and this etherification will be carried away with the ether after the vacuum is restored, thus reducing the acid-reducing and antibacterial effects.

[0038] In this invention, after the S3 reaction is completed, an inert gas is introduced into the reactor to restore the reactor to normal pressure, thereby obtaining the polyester product.

[0039] Through research and extensive experimental verification, this invention has discovered that during the preparation of PBAT resin, the introduction of a quaternary ammonium compound containing at least two hydroxyl groups allows for the chemical grafting of quaternary ammonium groups through the reaction of hydroxyl groups with carboxylic acids in the polyester. These quaternary ammonium groups enable the polyester to adsorb onto the bacterial cell surface during use, with hydrophobic groups inserting into the lipid layer. This alters cell membrane permeability, disrupts membrane structure, causes intracellular leakage, denatures or inhibits enzyme and protein activity, and affects bacterial metabolism, ultimately leading to bacterial death and imparting a long-lasting antibacterial effect to the material. Furthermore, the reaction of hydroxyl groups with the carboxyl groups of the polyester significantly reduces the acid value, preventing PBAT from degrading too rapidly due to high acid values, thus reducing its durability. This invention also reveals the importance of controlling the timing of the compound's addition. Adding it too early diminishes the acid-reducing effect, possibly because excess 1,4-butanediol remaining in the polymerization reactor may not have had time to be removed by vacuum. When the compound is added and the vacuum is restored, it is carried away along with the excess 1,4-butanediol, resulting in less of the compound actually participating in the reaction. Adding the resin too late will result in uneven antibacterial and acid-lowering properties, presumably due to increased viscosity in the later stages, affecting the grafting reaction. Only by adding the resin in the early stages of the final polycondensation reaction, such as 4-60 minutes after the start of the final polycondensation reaction, can the expected effects of low acid value and long-lasting antibacterial action be achieved.

[0040] The experiments of this invention also found that when a quaternary ammonium compound containing two or more hydroxyl groups was added in the early stage of the final polycondensation reaction, the tensile properties of the material were significantly improved. It is speculated that the quaternary ammonium compound at this time acts as a branching agent, allowing PBAT to form branched chains with specific structures during the polymerization process, thereby improving its tensile properties.

[0041] Furthermore, this invention has found that if the amount of the aforementioned compound containing at least two hydroxyl groups in the polyester is controlled within the range of 0.02-1.2 wt%, it can not only effectively reduce the acid value and improve the antibacterial effect of the polyester, but also improve the overall performance. Adding amounts below this range result in poorer antibacterial and acid value reduction effects; conversely, adding amounts exceeding this range can affect the regularity of the molecular chain, crystallinity, and even reduce the melting point and mechanical properties.

[0042] The present invention also provides a low-acid-value, long-lasting antibacterial, biodegradable polyester prepared by the above method, wherein the polyester has an acid value ≤25mol / t and an antibacterial rate of over 90% after soaking in water for 7 days, and the antibacterial effect is significantly improved.

[0043] The low-acid-value, long-lasting antibacterial, and biodegradable polyester described in this invention is suitable for fields such as mulch film, food packaging, and medical and health care, and is especially suitable for use in disposable products such as catering food packaging and medical and health care.

[0044] Compared with the prior art, the positive effects of the technical solution of the present invention are as follows:

[0045] The antibacterial effect of the material is achieved through chemical grafting, rather than physical blending of the resin and antibacterial agent later. This avoids the problem of antibacterial agent leaching causing a significant reduction in its antibacterial effect. It also reduces the acid value by consuming the terminal carboxyl groups through chemical reaction, thereby increasing its durability and greatly expanding the application fields of PBAT resin in food packaging, medical and health care, and other fields. Detailed Implementation

[0046] The present invention will be further described below with reference to the embodiments. It should be noted that the embodiments do not constitute a limitation on the scope of protection of the present invention.

[0047] The main raw material sources involved in the various embodiments and comparative examples of this invention are as follows; unless otherwise specified, all raw materials were obtained from ordinary commercial channels:

[0048] Terephthalic acid: purchased from Shandong Xiya Chemical Co., Ltd.;

[0049] Adipic acid: purchased from Jinan Century Tongda Chemical Co., Ltd.;

[0050] 1,4-Butanediol: purchased from Shandong Jinyueyuan New Materials Co., Ltd.;

[0051] n-Butyl titanate: purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0052] Quaternary ammonium salt-16: purchased from Shanghai BOC Sciences Co., Ltd.;

[0053] Dodecyl dihydroxyethyl methyl ammonium chloride: purchased from Hunan Zhenyuan Chemical Co., Ltd.;

[0054] Polyquaternium-10: purchased from Shanghai Maclean Biochemical Technology Co., Ltd.;

[0055] Chitosan quaternary ammonium salt: purchased from Wuhan Lanabai Pharmaceutical Chemical Co., Ltd.;

[0056] 2,3-Dihydroxypropyl-trimethylammonium chloride: Shanghai Bid Pharmaceutical Technology Co., Ltd.;

[0057] Hexadecyltrimethylammonium bromide: purchased from Beijing Yangcun Chemical Co., Ltd.;

[0058] 3-Chloro-2-hydroxypropyltrimethylammonium chloride: purchased from Shandong Lifan Chemical Co., Ltd.;

[0059] Glycerin: Purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0060] Staphylococcus aureus (representative of Gram-positive bacteria): purchased from Shanghai Jizhi Biochemical Technology Co., Ltd.;

[0061] Escherichia coli (representative of Gram-negative bacteria): purchased from Shanghai Xuanya Biotechnology Co., Ltd.

[0062] The main analytical methods used in the embodiments and comparative examples of this invention are as follows:

[0063] Mechanical properties (tensile strength): determined using an Instron 5966 universal testing machine (refer to ISO 527 method);

[0064] Acid value test: The content of terminal carboxyl groups was tested using chloroform as solvent and a Metrohm Titrino series automatic potentiometric titrator. The test method is the same as that in standard FZ / T50012-2006 Determination of terminal carboxyl group content in polyester - titration analysis.

[0065] Antibacterial rate test: The bacterial strain was incubated overnight in a bacterial incubator with liquid culture medium. Its OD (optical density) value was measured using an enzyme-linked immunosorbent assay (ELISA) reader. Then, it was diluted to a specific OD value with sterilized liquid culture medium for antibacterial experiments. A fixed amount of polyester granules was weighed, sterilized, and then placed in a certain amount of sterile water and shaken for a certain period of time. The granules were then removed, and the sterile water after removal and the removed polyester granules were used for antibacterial tests to evaluate the leaching and long-lasting antibacterial effect of the polyester antibacterial agent. The antibacterial rate was calculated using the following formula:

[0066]

[0067] In the formula, OD sample is the OD value of a quantitative polyester particle or sterile water after removing the polyester particle and a quantitative amount of bacteria after co-culturing in a quantitative liquid culture medium for 24 hours; if calculating the antibacterial rate of polyester particles, OD blank is the initial OD value of bacteria in a quantitative liquid culture medium without polyester particles; if calculating the antibacterial rate of sterile water after removing the polyester particles, OD blank is the initial OD value of bacteria in a quantitative liquid culture medium after adding sterile water; OD pure is the OD value of a quantitative amount of bacteria after co-culturing in a quantitative liquid culture medium for 24 hours without adding the sample.

[0068] Unless otherwise specified above, the equipment and testing methods used in this invention, such as acid value and melting point, are all common equipment and methods in the field.

[0069]

Example 1

[0070] The steps for preparing a low-acid-value, long-lasting, antibacterial, and biodegradable polyester are as follows:

[0071] S1: Weigh out 1000g (6.02mol) of terephthalic acid, 1000g (6.84mol) of adipic acid, 1507g (16.72mol) of 1,4-butanediol, and n-butyl titanate (Ti accounting for 50ppm of the total mass of terephthalic acid, adipic acid, and butanediol) and add them to a 5L reactor. Start stirring, purge with nitrogen three times, and maintain atmospheric pressure. Heat the system to 230℃ and carry out the esterification reaction for 2 hours at an esterification pressure of 80 kPaA.

[0072] S2: After the esterification reaction is completed, the temperature is raised to 230℃, and the vacuum is drawn to an absolute pressure of 3kPa to carry out the pre-condensation reaction for 30 minutes.

[0073] S3: After the pre-condensation reaction is completed, the pressure in the reactor is reduced to a high vacuum of 100 Pa, and the final condensation reaction is carried out at 235 °C. 5 min after the start of the final condensation reaction, 0.05% of dodecyl dihydroxyethyl methyl ammonium chloride (i.e., the total mass of terephthalic acid, adipic acid and butanediol in step S1) of the total polyester mass is added. After stirring for 3 min, the high vacuum of 100 Pa is restored, and the reaction is continued at 235 °C for 3 h. After stirring is stopped, nitrogen is introduced into the reactor to restore the reactor to normal pressure, and polyester melt is obtained. It is extruded under nitrogen protection, cooled to room temperature, and then pelletized to obtain a low-acid-value, long-lasting, antibacterial, and biodegradable polyester.

[0074] The polyester has an acid value of 22 mol / t, a melting point Tm of 122℃, and a tensile strength of 28.6 MPa.

[0075] After soaking in water for seven days, the polyester showed antibacterial rates of 93% and 94% against Escherichia coli and Staphylococcus aureus, respectively. The water after removing the polyester particles showed antibacterial rates of 2% and 1% against Escherichia coli and Staphylococcus aureus, respectively. After drying the polyester particles soaked for seven days and soaking them for another week, the antibacterial rates against Escherichia coli and Staphylococcus aureus were 92% and 93%, respectively.

[0076]

Example 2

[0077] The steps for preparing a low-acid-value, long-lasting, antibacterial, and biodegradable polyester are as follows:

[0078] S1: Weigh out 961.4 g (5.78 mol) of terephthalic acid, 1033.7 g (7.07 mol) of adipic acid, 1507 g (16.72 mol) of 1,4-butanediol, and n-butyl titanate (Ti accounting for 100 ppm of the total mass of terephthalic acid, adipic acid, and butanediol) and add them to a 5 L reactor. Start stirring, purge with nitrogen three times, and maintain atmospheric pressure. Heat the system to 190 °C and carry out the esterification reaction for 2.5 h at an esterification pressure of 40 kPaA.

[0079] S2: After the esterification reaction is completed, the temperature is raised to 230℃, and the vacuum is drawn to an absolute pressure of 8kPa to carry out the pre-condensation reaction for 50 minutes.

[0080] S3: After the pre-condensation reaction is completed, the pressure in the reactor is reduced to a high vacuum of 5 Pa, and the final condensation reaction is carried out at 235°C. 30 min after the start of the final condensation reaction, 0.8% of the total mass of the polyester, namely dodecyl dihydroxyethyl methyl ammonium chloride, is added. After stirring for 15 min, the high vacuum of 5 Pa is restored, and the reaction is continued at 235°C for 2 h. After stirring is stopped, nitrogen is introduced into the reactor to restore the reactor to normal pressure, and polyester melt is obtained. It is extruded under nitrogen protection, cooled to room temperature, and then pelletized to obtain a low acid value, long-lasting antibacterial and biodegradable polyester.

[0081] The polyester has an acid value of 19 mol / t, a melting point Tm of 123℃, and a tensile strength of 29.2 MPa.

[0082] After soaking in water for seven days, the polyester particles showed inhibition rates of 97% and 98% against Escherichia coli and Staphylococcus aureus, respectively. The water after removing the polyester particles showed inhibition rates of 3% and 2% against Escherichia coli and Staphylococcus aureus, respectively. After drying the polyester particles soaked for seven days and then soaking them for another week, the inhibition rates against Escherichia coli and Staphylococcus aureus were 96% and 97%, respectively.

[0083]

Example 3

[0084] The steps for preparing a low-acid-value, long-lasting, antibacterial, and biodegradable polyester are as follows:

[0085] S1: Weigh out 1000g (6.02mol) of terephthalic acid, 1000g (6.84mol) of adipic acid, 1738.4g (19.29mol) of 1,4-butanediol, and n-butyl titanate (Ti accounting for 200ppm of the total mass of terephthalic acid, adipic acid, and butanediol) and add them to a 5L reactor. Start stirring, purge with nitrogen three times, and maintain atmospheric pressure. Heat the system to 220℃ and carry out the esterification reaction for 3 hours at an esterification pressure of 40 kPaA.

[0086] S2: After the esterification reaction is completed, the temperature is raised to 245℃, and the vacuum is drawn to an absolute pressure of 8kPa to carry out the pre-condensation reaction for 30 minutes.

[0087] S3: After the pre-condensation reaction is completed, the pressure in the reactor is reduced to a high vacuum of 5 Pa, and the final condensation reaction is carried out at 245℃. 30 min after the start of the final condensation reaction, 0.8% of the total mass of the polyester quaternary ammonium salt-16 is added. After stirring for 15 min, the high vacuum of 5 Pa is restored, and the reaction is continued at 245℃ for 2 h. After stirring is stopped, nitrogen is introduced into the reactor to restore the reactor to normal pressure, and polyester melt is obtained. It is extruded under nitrogen protection, cooled to room temperature, and then pelletized to obtain a low acid value, long-lasting antibacterial and biodegradable polyester.

[0088] The polyester has an acid value of 16 mol / t, a melting point Tm of 121℃, and a tensile strength of 28.5 MPa.

[0089] After soaking in water for seven days, the polyester particles showed inhibition rates of 99% and 97% against Escherichia coli and Staphylococcus aureus, respectively. The water after removing the polyester particles showed inhibition rates of 1% and 1% against Escherichia coli and Staphylococcus aureus, respectively. After drying the polyester particles soaked for seven days, they were soaked for another week, maintaining inhibition rates of 97% and 95% against Escherichia coli and Staphylococcus aureus, respectively.

[0090]

Example 4

[0091] The steps for preparing a low-acid-value, long-lasting, antibacterial, and biodegradable polyester are as follows:

[0092] S1: Weigh out 1068.2 g (6.43 mol) of terephthalic acid, 939.7 g (6.43 mol) of adipic acid, 1274 g (14.15 mol) of 1,4-butanediol, and 200 ppm of tetrabutyl titanate (Ti accounting for 200 ppm of the total mass of terephthalic acid, adipic acid, and butanediol) and add them to a 5 L reactor. Start stirring, purge with nitrogen three times, and maintain atmospheric pressure. Heat the system to 220 °C and carry out the esterification reaction for 3 hours at an esterification pressure of 80 kPaA.

[0093] S2: After the esterification reaction is completed, the temperature is raised to 230℃, and the vacuum is drawn to an absolute pressure of 3kPa to carry out the pre-condensation reaction for 90 minutes.

[0094] S3: After the pre-condensation reaction is completed, the pressure in the reactor is reduced to a high vacuum of 5 Pa, and the final condensation reaction is carried out at 230°C. 4 min after the start of the final condensation reaction, 0.02% of the total mass of the polyester, namely dodecyl dihydroxyethyl methyl ammonium chloride, is added. After stirring for 15 min, the high vacuum of 5 Pa is restored, and the reaction is continued at 230°C for 4 h. After stirring is stopped, nitrogen is introduced into the reactor to restore the reactor to normal pressure, and polyester melt is obtained. It is extruded under nitrogen protection, cooled to room temperature, and then pelletized to obtain a low acid value, long-lasting antibacterial and biodegradable polyester.

[0095] The polyester has an acid value of 25 mol / t, a melting point Tm of 119℃, and a tensile strength of 27.8 MPa.

[0096] After soaking in water for seven days, the polyester particles showed inhibition rates of 90% and 91% against Escherichia coli and Staphylococcus aureus, respectively. The water after removing the polyester particles showed inhibition rates of 1% and 2% against Escherichia coli and Staphylococcus aureus, respectively. After drying the polyester particles soaked for seven days and soaking them for another week, the inhibition rates against Escherichia coli and Staphylococcus aureus remained at 90% and 90%, respectively.

[0097]

Example 5

[0098] The steps for preparing a low-acid-value, long-lasting, antibacterial, and biodegradable polyester are as follows:

[0099] S1: Weigh out 1000g (6.02mol) of terephthalic acid, 1000g (6.84mol) of adipic acid, 1738.4g (19.29mol) of 1,4-butanediol, and n-butyl titanate (Ti accounting for 100ppm of the total mass of terephthalic acid, adipic acid, and butanediol) and add them to a 5L reactor. Start stirring, purge with nitrogen three times, and maintain atmospheric pressure. Heat the system to 220℃ and carry out the esterification reaction for 2 hours at an esterification pressure of 40 kPaA.

[0100] S2: After the esterification reaction is completed, the temperature is raised to 230℃, and the vacuum is drawn to an absolute pressure of 3kPa to carry out the pre-condensation reaction for 90 minutes.

[0101] S3: After the pre-condensation reaction is completed, the pressure of the reactor is reduced to a high vacuum of 100 Pa, and the final condensation reaction is carried out at 245°C. 60 min after the start of the final condensation reaction, 1.2% of the total mass of the polyester, namely dodecyl dihydroxyethyl methyl ammonium chloride, is added. After stirring for 3 min, the high vacuum of 5 Pa is restored, and the reaction is continued at 245°C for 3 h. After stirring is stopped, nitrogen is introduced into the reactor to restore the reactor to normal pressure, and polyester melt is obtained. It is extruded under nitrogen protection, cooled to room temperature, and then pelletized to obtain a low acid value, long-lasting antibacterial and biodegradable polyester.

[0102] The polyester has an acid value of 18 mol / t, a melting point Tm of 116℃, and a tensile strength of 30.2 MPa.

[0103] After soaking in water for seven days, the polyester particles showed inhibition rates of 96% and 97% against Escherichia coli and Staphylococcus aureus, respectively. The water after removing the polyester particles showed inhibition rates of 2% and 3% against Escherichia coli and Staphylococcus aureus, respectively. After drying the polyester particles and soaking them for another week, the inhibition rates against Escherichia coli and Staphylococcus aureus reached 95% and 96%, respectively.

[0104]

Example 6

[0105] The steps for preparing a low-acid-value, long-lasting, antibacterial, and biodegradable polyester are as follows:

[0106] S1: Weigh out 1000g (6.02mol) of terephthalic acid, 1000g (6.84mol) of adipic acid, 1738.4g (19.29mol) of 1,4-butanediol, and n-butyl titanate (Ti accounting for 100ppm of the total mass of terephthalic acid, adipic acid, and butanediol) and add them to a 5L reactor. Start stirring, purge with nitrogen three times, and maintain atmospheric pressure. Heat the system to 220℃ and carry out the esterification reaction for 3 hours at an esterification pressure of 40 kPaA.

[0107] S2: After the esterification reaction is completed, the temperature is raised to 245℃, and the vacuum is drawn to an absolute pressure of 8kPa to carry out the pre-condensation reaction for 60min.

[0108] S3: After the pre-condensation reaction is completed, the pressure in the reactor is reduced to a high vacuum of 5 Pa, and the final condensation reaction is carried out at 240°C. 30 min after the start of the final condensation reaction, 0.8% of the total mass of 2,3-dihydroxypropyl-trimethylammonium chloride is added. After stirring for 15 min, the high vacuum of 5 Pa is restored, and the reaction is continued at 240°C for 2.5 h. After stirring is stopped, nitrogen is introduced into the reactor to restore the reactor to normal pressure, and polyester melt is obtained. It is extruded under nitrogen protection, cooled to room temperature, and then pelletized to obtain a low acid value, long-lasting antibacterial and biodegradable polyester.

[0109] The polyester has an acid value of 24 mol / t, a melting point Tm of 123℃, and a tensile strength of 28.2 MPa.

[0110] After soaking in water for seven days, the polyester particles showed inhibition rates of 92% and 90% against Escherichia coli and Staphylococcus aureus, respectively. The water after removing the polyester particles showed inhibition rates of 2% and 2% against Escherichia coli and Staphylococcus aureus, respectively. After drying the polyester particles soaked for seven days, they were soaked for another week, maintaining inhibition rates of 91% and 88% against Escherichia coli and Staphylococcus aureus, respectively.

[0111]

Example 7

[0112] Low-acid-value, long-lasting antibacterial, and biodegradable polyester was prepared according to the method in Example 1, except that in step S3, the quaternary ammonium compound was replaced by polyquaternium salt-10 at 0.22% of the total mass of the polyester instead of dodecyl dihydroxyethyl methyl ammonium chloride added at 0.05% of the total mass of the polyester. Other operations and parameters remained unchanged, and low-acid-value, long-lasting antibacterial, and biodegradable polyester was obtained.

[0113] The polyester has an acid value of 19 mol / t, a melting point Tm of 121℃, and a tensile strength of 29.5 MPa.

[0114] After soaking in water for seven days, the polyester showed inhibition rates of 90% and 91% against Escherichia coli and Staphylococcus aureus, respectively. The water after removing the polyester particles showed inhibition rates of 2% and 1% against Escherichia coli and Staphylococcus aureus, respectively. After drying the polyester particles soaked for seven days and soaking them for another week, the inhibition rates against Escherichia coli and Staphylococcus aureus were 88% and 89%, respectively.

[0115]

Example 8

[0116] The low-acid-value, long-lasting antibacterial, and biodegradable polyester was prepared according to the method in Example 4, except that in step S3, 0.02% of the total mass of the polyester, which is added as a quaternary ammonium compound 4 minutes after the start of the final polycondensation reaction, was replaced by 0.5% of the total mass of the polyester, which is added as a chitosan quaternary ammonium salt 60 minutes after the start of the final polycondensation reaction. At the same time, the final polycondensation reaction temperature was increased from 230°C to 235°C. Other operations and parameters remained unchanged, and the low-acid-value, long-lasting antibacterial, and biodegradable polyester was obtained.

[0117] The polyester has an acid value of 25 mol / t, a melting point Tm of 120℃, and a tensile strength of 28.9 MPa.

[0118] After soaking in water for seven days, the polyester particles showed inhibition rates of 90% and 90% against Escherichia coli and Staphylococcus aureus, respectively. The water after removing the polyester particles showed inhibition rates of 1% and 2% against Escherichia coli and Staphylococcus aureus, respectively. After drying the polyester particles soaked for seven days and soaking them for another week, the inhibition rates against Escherichia coli and Staphylococcus aureus remained at 88% and 85%, respectively.

[0119] Comparative Example 1

[0120] Biodegradable polyester was prepared according to the method in Example 1, except that in step S3, after the final shrinkage reaction for 5 min, the added quaternary ammonium compound was replaced with hexadecyltrimethylammonium bromide (a quaternary ammonium compound without OH). Other operations and parameters remained unchanged, and biodegradable polyester was obtained.

[0121] The polyester has an acid value of 35 mol / t, a melting point Tm of 122℃, and a tensile strength of 25.2 MPa.

[0122] After being soaked in water for seven days, the polyester showed antibacterial rates of 3% and 2% against Escherichia coli and Staphylococcus aureus, respectively. The antibacterial rates of the water after removing the polyester particles were 96% and 95%, respectively.

[0123] Comparative Example 2

[0124] Biodegradable polyester was prepared according to the method in Example 2, except that in step S3, after the final shrinkage reaction for 5 minutes, the added quaternary ammonium compound was replaced with 3-chloro-2-hydroxypropyltrimethylammonium chloride (a quaternary ammonium compound containing only one hydroxyl group), and other operations and parameters remained unchanged, thus obtaining biodegradable polyester.

[0125] The polyester has an acid value of 28 mol / t, a melting point Tm of 115℃, and a tensile strength of 24.3 MPa.

[0126] After soaking in water for seven days, the polyester showed inhibition rates of 82% and 81% against Escherichia coli and Staphylococcus aureus, respectively. The inhibition rates of the water after removing the polyester particles were 1% and 0%, respectively. After drying the PBAT resin soaked for seven days and then soaking it for another week, the inhibition rates against Escherichia coli and Staphylococcus aureus were 78% and 75%, respectively.

[0127] Comparative Example 3

[0128] Biodegradable polyester was prepared according to the method in Example 1, except that in step S3, after the final shrinkage reaction for 5 minutes, the added quaternary ammonium compound was replaced with glycerol (a non-quaternary ammonium compound containing two hydroxyl groups), and other operations and parameters remained unchanged, thus obtaining biodegradable polyester.

[0129] The polyester has an acid value of 24 mol / t, a melting point Tm of 121℃, and a tensile strength of 27.8 MPa.

[0130] After being soaked in water for seven days, the polyester showed an inhibition rate of 0% against Escherichia coli and 0% against Staphylococcus aureus, respectively. The water after removing the polyester particles showed an inhibition rate of 0% and 0%, respectively, indicating no antibacterial effect.

[0131] Comparative Example 4

[0132] Biodegradable polyester was prepared according to the method in Example 1, except that the quaternary ammonium compound was replaced in step S2 instead of step S3, that is, added 5 min after the pre-condensation reaction. Other operations and parameters remained unchanged, and biodegradable polyester was obtained.

[0133] The polyester has an acid value of 32 mol / t, a melting point Tm of 120℃, and a tensile strength of 25.5 MPa.

[0134] After being soaked in water for seven days, the polyester showed inhibition rates of 1% and 0% against Escherichia coli and Staphylococcus aureus, respectively. The inhibition rates of the water after removing the polyester particles were 1% and 0%, respectively.

[0135] Comparative Example 5

[0136] Biodegradable polyester was prepared according to the method in Example 1, except that in step S3, the addition time of the quaternary ammonium compound dodecyl dihydroxyethyl methyl ammonium chloride was changed from 5 min after the start of the final polycondensation reaction to 90 min after the start of the final polycondensation reaction (i.e., the middle of the final polycondensation reaction). Other operations and parameters remained unchanged, and biodegradable polyester was obtained.

[0137] The polyester has an acid value of 30 mol / t, a melting point Tm of 120℃, and a tensile strength of 25.4 MPa.

[0138] After soaking in water for seven days, the polyester particles showed inhibition rates of 65% and 63% against Escherichia coli and Staphylococcus aureus, respectively. The inhibition rates of the water after removing the polyester particles were 2% and 3%, respectively. After drying the polyester particles soaked for seven days and then soaking them for another week, the inhibition rates against Escherichia coli and Staphylococcus aureus were 62% and 60%, respectively.

[0139] Comparative Example 6

[0140] Biodegradable polyester was prepared according to the method in Example 1, except that in step S3, the addition time of the quaternary ammonium compound dodecyl dihydroxyethyl methyl ammonium chloride was changed from 5 min after the start of the final polycondensation reaction to 150 min after the start of the final polycondensation reaction (i.e., the later stage of the final polycondensation reaction). Other operations and parameters remained unchanged, and biodegradable polyester was obtained.

[0141] The polyester has an acid value of 35 mol / t, a melting point Tm of 119℃, and a tensile strength of 24.5 MPa.

[0142] After soaking in water for seven days, the polyester particles showed inhibition rates of 45% and 42% against Escherichia coli and Staphylococcus aureus, respectively. The inhibition rates of the water after removing the polyester particles were 1% and 2%, respectively. After drying the polyester particles soaked for seven days and then soaking them for another week, the inhibition rates against Escherichia coli and Staphylococcus aureus were 41% and 40%, respectively.

[0143] As can be seen from the examples and comparative examples, adding quaternary ammonium compounds containing two or more OH groups during the early stage of the final polycondensation reaction (the first 2-25% of the total final polycondensation reaction time, such as 4-60 min) can effectively reduce the acid value (≤25 mol / t) and also impart excellent antibacterial effects (≥90%) to the polyester. In particular, when the addition amount is controlled at 0.02-1.2% of the polyester melt, and the final polycondensation reaction is continued under vacuum after stirring for 3-15 min, the acid value reduction and antibacterial effects are even better, and the mechanical properties can be further improved. If the quaternary ammonium compound does not contain OH, as shown in Comparative Example 1, its acid value is high due to the lack of a group that reacts with the carboxyl group at the end of the ester, and the antibacterial component is easily precipitated. If a quaternary ammonium compound containing only one hydroxyl group is added, as shown in Comparative Example 2, the effect on reducing acid value and increasing tensile strength is limited. Similarly, Comparative Example 3 adds a non-quaternary ammonium compound containing hydroxyl groups, Comparative Example 4 adds a quaternary ammonium compound before the final shrinkage reaction, and Comparative Examples 5 and 6 add quaternary ammonium compounds containing two hydroxyl groups in the middle and later stages of the final shrinkage reaction, none of which can achieve the expected effect of low acid value and long-lasting antibacterial effect.

[0144] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a low-acid-value, long-lasting, antibacterial, and biodegradable polyester, characterized in that, The method comprises esterification of terephthalic acid, adipic acid and butanediol to obtain an esterification product, and then sequentially performing pre-polycondensation and final polycondensation to obtain the polyester; The total time of the final polycondensation reaction is 2-4 h, and a quaternary ammonium compound containing at least two hydroxyl groups is added in the early stage of the final polycondensation reaction; the early stage of the final polycondensation reaction refers to a time period of 2-25% of the total time of the final polycondensation reaction, or 4-60 min after the start of the final polycondensation reaction; The quaternary ammonium compound has the following structure shown in formula (1): In formula (1), X is halogen or an acid radical selected from sulfate, phosphate, nitrate; R1, R2, R3, and R4 each independently represent a substituent of any structure and are not H, and the total number of hydroxyl groups contained in the substituents represented by R1, R2, R3, and R4 is at least 2; The R1, R2, R3, and R4 can be the same or different.

2. The production method according to claim 1, characterized by, The quaternary ammonium compound contains 2-3 hydroxyl groups.

3. The preparation method according to claim 1, characterized in that, The early stage of the final polycondensation reaction refers to 5-30 min after the start of the final polycondensation reaction.

4. The production method according to claim 1, characterized by, The total number of hydroxyl groups contained in the substituents represented by R1, R2, R3, and R4 is 2-3.

5. The method of claim 1, wherein, R1, R2, R3, and R4 each independently represent -R-(OH)n, wherein R is selected from C3-C60 alicyclic substituents containing or not containing heteroatoms, C1-C60 aliphatic hydrocarbon groups, and C1-C25 alkyl groups, the heteroatoms are O and N, n≥0, and the total sum of n in R1, R2, R3, and R4 is not less than 2.

6. The production method according to claim 5, wherein The R is a C1-C3 alkyl group or a C12-C18 aliphatic hydrocarbon group, and n has a value of 2-3.

7. The preparation method according to claim 5, characterized in that, At least one of R1, R2, R3, and R4 contains a C12-C18 aliphatic hydrocarbon group.

8. The method of claim 1, wherein, The quaternary ammonium compound is selected from one or more of quaternary ammonium compounds containing C3-C60 alicyclic substituents and quaternary ammonium compounds containing C1-C25 alkyl groups.

9. The production method according to claim 8, characterized by, The quaternary ammonium compound is selected from one or more of polyquaternium-10, chitosan quaternary ammonium salt, dodecyl bis-hydroxyethyl methyl ammonium chloride, quaternary ammonium salt-16, and 2,3-dihydroxypropyl-trimethyl ammonium chloride.

10. The method of claim 9, wherein, The quaternary ammonium compound is selected from one or more of quaternary ammonium salt-16 and dodecyl bis-hydroxyethyl methyl ammonium chloride.

11. The method of claim 1, wherein, The preparation method of the low-acid-value long-acting bacteriostatic degradable polyester comprises the following specific steps: S1: esterification of terephthalic acid, adipic acid, butanediol, and a catalyst; S2: after the esterification reaction is completed, pre-polycondensation is performed by heating; S3: after the pre-polycondensation reaction is completed, final polycondensation is performed, and a quaternary ammonium compound containing at least two hydroxyl groups is added in the early stage of the final polycondensation reaction to obtain the low-acid-value long-acting bacteriostatic degradable polyester.

12. The method of claim 11, wherein, The molar ratio of the total amount of terephthalic acid and adipic acid to butanediol in S1 is 1:(1.1-1.5); and / or The catalyst in S1 is selected from one or more of titanium-based catalysts.

13. The method of claim 12, wherein, The molar ratio of terephthalic acid to adipic acid is (45-50):(55-50).

14. The method of claim 12, wherein, The catalyst is selected from one or more of titanium dioxide, n-butyl titanate, isopropyl titanate, tetraisopropyl titanate, tetraisobutyl titanate, tetraisooctyl titanate, titanium citrate, titanium tartrate, titanium glycolate, titanium propylene glycolate, and titanium butylene glycolate.

15. The method of claim 12, wherein, The catalyst is a titanium-based catalyst, and the amount of the catalyst, calculated based on the mass of titanium element, is 50-200 ppm of the total mass of terephthalic acid, adipic acid, and butanediol.

16. The method of claim 11, wherein, The esterification reaction in S1 is carried out at normal pressure.

17. The preparation method according to claim 14, characterized in that, The esterification reaction in S1 is carried out at a pressure of 40-80 KPaA.

18. The method of claim 11, wherein, The esterification reaction in S1 is carried out at a temperature of 190-230 ℃ for 2-3 h.

19. The method of claim 18, wherein, The reaction is carried out at a temperature of 190-220 ℃ for 2-2.5 h.

20. The method of claim 11, wherein, The esterification reaction is carried out under the protection of an inert gas selected from nitrogen and argon.

21. The method of claim 11, wherein, The pre-polycondensation reaction in S2 is carried out at a pressure of 3-8 KPaA.

22. The method of claim 11, wherein, The pre-polycondensation reaction in S2 is carried out at a temperature of 230-245 ℃ for 30-90 min.

23. The method of claim 22, wherein, The reaction is carried out at a temperature of 230-235 ℃ for 30-50 min.

24. The method of claim 11, wherein, The final polycondensation reaction in S3 is carried out at a pressure of 5-100 PaA; and / or The reaction in S3 is carried out in a pre-stage, wherein the pre-stage refers to a period of 2-25% of the total time of the final polycondensation reaction; and / or The amount of the quaternary ammonium compound containing at least two hydroxyl groups added in S3 is 0.02-1.2% of the total mass of terephthalic acid, adipic acid, and butanediol in S1; and / or After the quaternary ammonium compound is added in S3, the mixture is stirred for 3-15 min.

25. The method of claim 24, wherein, The amount of the quaternary ammonium compound containing at least two hydroxyl groups added in S3 is 0.02-0.8% of the total mass of terephthalic acid, adipic acid, and butanediol in S1.

26. The method of claim 11, wherein, The final polycondensation reaction in S3 is carried out at a temperature of 230-245 ℃ for 2-4 h.

27. The method of claim 26, wherein, The reaction is carried out at a temperature of 230-235 ℃ for 2-3 h.

28. The method of claim 11, wherein, The total time of the final polycondensation reaction in S3 is 2-4 h, wherein the pre-stage refers to 4-60 min after the start of the final polycondensation reaction.

29. The method of claim 28, wherein, The pre-stage refers to 5-30 min after the start of the final polycondensation reaction.

30. A low-acid-value long-acting bacteriostatic degradable polyester prepared by the method of any one of claims 1-29.

31. The use of the low-acid-value long-acting bacteriostatic degradable polyester prepared by the method of any one of claims 1-29 in the fields of mulching film, food packaging, and medical and health care.

32. The use according to claim 31, characterized in that The low-acid-value long-acting bacteriostatic degradable polyester is suitable for use in the field of disposable products in the fields of catering, food packaging, and medical and health care.

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