A bio-based high-efficiency antibacterial polyester fiber and its preparation method

Abstract

This invention discloses a bio-based high-efficiency antibacterial polyester fiber and its preparation method, belonging to the field of synthetic fiber technology. It solves the problems of high hue, low bio-based content, and weak antibacterial performance in existing technologies. The fiber is copolymerized from a first, second, third, and fourth ester. The first ester is formed by esterification of oxalic acid and 1,3-propanediol; the second ester is formed by esterification of an aliphatic diacid and 1,3-propanediol; the third ester is formed by esterification of a quaternary ammonium salt of hydroxy fatty acids; and the fourth ester is formed by esterification of terephthalic acid and ethylene glycol. This invention uses oxalic acid, aliphatic diacids, 1,3-propanediol, and quaternary ammonium salts of hydroxy fatty acids to prepare polyester fibers, achieving a bio-based carbon content of over 30%. The entire preparation process eliminates the need for diethylene glycol dimethyl ether, a solvent required in existing technologies, thus solving the problem of high hue caused by solvent residue. The fiber maintains highly efficient and long-lasting broad-spectrum antibacterial properties, with an antibacterial rate exceeding 99%.

Description

Technical Field

[0001] This invention belongs to the field of synthetic fiber technology, and more specifically, relates to a bio-based high-efficiency antibacterial polyester fiber and its preparation method. Background Technology

[0002] Bio-based polyesters mainly refer to polyester materials obtained by polymerizing diacids and diols derived from bio-based monomers. In recent years, due to the increasing scarcity of petroleum resources, bio-based materials have received growing attention, and bio-based polyesters are a crucial example. Research in the field of bio-polyesters primarily focuses on polylactic acid (PLA), polyhydroxyalkanoates (PHA), polybutylene succinate (PBS), and polyethylene furanate (PET). Among these, polyethylene furanate (PEF) has a structure and properties similar to petroleum-based polyethylene terephthalate (PET) and is expected to replace PET in some applications, such as fibers, films, and bottle flakes. Some fields (especially biomedical materials) have high requirements for the antibacterial properties of PET.

[0003] Currently, the antibacterial modification of PET mainly suffers from the following problems: Physical addition: Patent CN201910966661.2 proposes blending non-fusible antibacterial agents such as nano-silver wires and bamboo charcoal powder with polyester melt. This method suffers from uneven dispersion, poor spinnability, easy clogging of spinnerets, and potential biotoxicity of nanomaterials. Natural extract blending: Patent CN201710846179.6 proposes blending plant-derived extracts such as tea leaves and mugwort leaves with polyester. This method suffers from poor thermal stability, uneven dispersion of extracts in the melt, easy attenuation of antibacterial properties, and poor wash resistance. Bio-based polymer copolymerization: Patent CN2022116375. 64.7 proposes introducing bio-based polyhydroxyalkanoate (PHA) oligomers into the polyester molecular chain through a chemical reaction. Although this method can achieve durable antibacterial function, it uses diethylene glycol dimethyl ether as a solvent in the preparation process. This solvent is difficult to completely remove in the subsequent polymerization process, resulting in a high hue b value of the final polymer, even reaching 7-9, which seriously affects the whiteness and appearance quality of the fiber. At the same time, the solvent residue also interferes with the polymerization reaction process, causing fluctuations in carboxyl content and unstable melt viscosity, ultimately leading to more spinning defects, filament drift, and low yield. In addition, the recovery and treatment of the solvent requires a complex distillation side stream extraction process, which increases production energy consumption and cost.

[0004] The automotive interior, mattress, and high-end apparel industries have stringent requirements for product whiteness, color uniformity, and dimensional stability. Existing bio-based antibacterial polyester fibers suffer from excessively high hue (b-value) due to their polymerization process, making them a bottleneck in market promotion. Therefore, there is an urgent need to develop a new type of polyester fiber that guarantees antibacterial properties, solves the problem of fiber yellowing, achieves low hue and high quality, and is produced using environmentally friendly processes with high bio-based content, in order to meet the stringent requirements of high-end applications for comprehensive material performance. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a bio-based high-efficiency antibacterial polyester fiber with low hue, high bio-based content, and strong antibacterial properties, as well as a method for its preparation.

[0006] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention for the bio-based high-efficiency antibacterial polyester fiber and its preparation method is as follows: A bio-based high-efficiency antibacterial polyester fiber is copolymerized from a first ester, a second ester, a third ester, and a fourth ester. The first ester is formed by esterification of oxalic acid and 1,3-propanediol. The second ester is formed by esterification of an aliphatic dicarboxylic acid and 1,3-propanediol. The third ester is formed by esterification of a quaternary ammonium salt of hydroxy fatty acids. The quaternary ammonium salt of hydroxy fatty acids is prepared by alcoholysis of vegetable oil to obtain hydroxyl-terminated fatty acids, which are then reacted with a quaternary ammonium salt compound. The fourth ester is formed by esterification of terephthalic acid and ethylene glycol.

[0007] Preferably, the aliphatic dicarboxylic acid includes succinic acid, adipic acid, azelaic acid, and sebacic acid.

[0008] Preferably, the vegetable oil includes palm oil, coconut shell oil, and soybean oil.

[0009] Preferably, the quaternary ammonium salt of the hydroxy fatty acid has the structural formula: HO-R1-COONR2R3R4, wherein R1 is a C6-C22 alkyl chain, and R2, R3, and R4 are C1-C4 alkyl chains.

[0010] Preferably, the molar ratio of the first ester, the second ester, the third ester, and the fourth ester is 1:(1.5-2.5):(0.5-1.0):(4.0-6.0).

[0011] Preferably, the molar ratio of the first ester, the second ester, the third ester, and the fourth ester is 1:2:0.6:5. By adjusting the molar ratio, the bio-based carbon content in the polymer is ensured to be ≥30%.

[0012] The polyester fiber produced by the above technical solution has a melting point of 110-122℃ and an intrinsic viscosity of 0.60-0.65dL / g. Although the melting point of this polyester fiber is low, it has good elasticity and is suitable for the home textile industry. Its hue b value is ≤4.0 or even ≤3.5, which solves the problem of fiber yellowing in the old process from the source and greatly improves the appearance quality. The polyester fiber has a breaking strength ≥3.2cN / dtex, an antibacterial rate of ≥99.0% against Staphylococcus aureus, Escherichia coli, and Candida albicans, and a bio-based carbon content ≥30%.

[0013] A method for preparing bio-based high-efficiency antibacterial polyester fiber includes the following steps: S1 Oxalic acid and 1,3-propanediol are stirred to form a slurry, and esterification reaction is carried out at 150-180°C under a nitrogen atmosphere and a pressure of 0.1-0.3 MPa until the water content reaches more than 90%, thus obtaining the first esterified product. S2. An aliphatic dicarboxylic acid and 1,3-propanediol are stirred to form a slurry. The esterification reaction is carried out at 180-220°C under a nitrogen atmosphere and a pressure of 0.1-0.3 MPa until the water content reaches more than 90%, thus obtaining the second esterified product. S3 The quaternary ammonium salt monomer of hydroxy fatty acid is premixed with a small amount of ethylene glycol and esterified at 160-200°C under a nitrogen atmosphere and a pressure of 0.1-0.3 MPa until no distilled water is produced, ensuring that the terminal carboxyl and terminal hydroxyl groups fully participate in the reaction, and the third esterified product is obtained. S4 involves mixing terephthalic acid and ethylene glycol to form a slurry, and then carrying out an esterification reaction at 240–260°C under a nitrogen atmosphere and a pressure of 0.1–0.3 MPa until the water content reaches more than 90%, thus obtaining the fourth esterified product. S5 mixes the first ester, second ester, third ester and fourth ester in molar ratio, adds catalyst and stabilizer, and under negative pressure, the system pressure is pumped from atmospheric pressure to an absolute pressure of 500 Pa, and the reaction is carried out at 255-265℃ for 40-60 min. Continue evacuating the vacuum to reduce the reaction pressure to below 100 Pa absolute pressure, raise the temperature to 270–280 °C, and continue the reaction for 80–100 min. Through vacuum control and temperature control, the melt viscosity is stabilized, thereby reducing the hue b value of the polyester fiber. S6 uses a spinning method to melt-spin polyester at a spinning temperature of 255–270℃ and a spinning speed of 600–1000 m / min. It has two cooling rings with air blowing: the first air temperature is 50–80℃ and the air speed is 1.5–2.5 m / s, the second air temperature is 14–20℃ and the air speed is 2.5–3.5 m / s, and the distance between the two air rings is 30–50 cm. S7 involves drawing, washing, crimping, cutting, and drying the fiber filaments. The drawing process is carried out using an oil bath at a temperature of 65–75°C. The oil contains 5–10 wt% sodium sulfite, the drawing ratio is 2.5–2.8, and the crimping temperature is 50–60°C. This process yields bio-based high-efficiency antibacterial polyester fiber.

[0014] Preferably, the preparation of the quaternary ammonium salt monomer of hydroxy fatty acids in step S3 includes the following steps: (1) Alcohololysis: Vegetable oil, ethylene glycol and sodium hydroxide were added to the reaction vessel at a mass ratio of 200:40:1 and stirred at 65°C for 2 hours. After washing with water and drying, crude fatty acid ethylene glycol esters were obtained. (2) Reduction: Fatty acid glycol esters and excess lithium aluminum hydride (LiAlH4) were reacted slowly in anhydrous tetrahydrofuran (THF) at 0-5°C for 3 h, and then the reaction was raised to room temperature for 12 h. After the reaction was completed, dilute hydrochloric acid was added to quench the reaction, the organic layer was separated, dried and distilled under reduced pressure to obtain mixed fatty alcohols. (3) Selective oxidation: The fatty alcohol was dissolved in dichloromethane, and Jones' reagent (CrO3 / dilute H2SO4) was added dropwise at 0℃. The reaction temperature was controlled not to exceed 5℃, and the reaction was carried out for 2 hours. The reaction progress was monitored by TLC. After the alcohol hydroxyl group was basically converted to the carboxyl group, the reaction was terminated. After extraction, washing with water and drying, hydroxyl-terminated fatty acids were obtained. (4) Quaternization: Dissolve an appropriate amount of hydroxy fatty acid in 200 ml of anhydrous N,N-dimethylformamide (DMF), add diethylamine as an acid-binding agent, and slowly add iodomethane dropwise under ice bath cooling. After the addition is complete, heat to 60 °C and react for 8 h. After the reaction is complete, remove DMF and excess iodomethane by vacuum distillation. Recrystallize the solid product with ethyl acetate to obtain a white crystalline solid, namely the quaternary ammonium salt monomer of hydroxy fatty acid.

[0015] Preferably, in step S3, the hydroxy fatty acid quaternary ammonium salt monomer accounts for 1 to 8% of the total molar amount of the dicarboxylic acid, more preferably 6 ± 0.5%.

[0016] Preferably, in step S5, the catalyst is antimony glycolate or tetrabutyl titanate, and the stabilizer is triphenyl phosphate. By mass fraction, the catalyst accounts for 0.01 to 0.05% of the total acid content, and the stabilizer accounts for 0.01 to 0.05% of the total acid content.

[0017] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention uses oxalic acid, aliphatic dicarboxylic acids, 1,3-propanediol, and quaternary ammonium salts of hydroxy fatty acids based on vegetable oils to prepare polyester fibers, resulting in a bio-based carbon content of over 30% in the fibers, which aligns with the development trend of carbon emission reduction and sustainable development. The entire preparation process eliminates the use of diethylene glycol dimethyl ether, a solvent required in the original technology, thus solving the problem of yellow fiber color (i.e., high b-value) caused by solvent residue from the source. This significantly reduces the b-value of the finished fiber from the original 7-9 to below 4.0, and even down to 3.5. The finished fiber has a pure white color, which can effectively meet the stringent requirements of high-end textiles for material appearance, further broadening the application fields. The entire preparation process does not use high-boiling-point organic solvents, reducing energy consumption and distillation costs associated with solvent recovery. Moreover, while achieving high bio-based content and low hue, the fiber maintains highly efficient and long-lasting broad-spectrum antibacterial properties and good mechanical properties, with an antibacterial rate of over 99% and a fiber strength of over 3.2 cN / dtex. Detailed Implementation

[0018] The invention will be further described below with reference to specific embodiments: This invention provides a bio-based high-efficiency antibacterial polyester fiber, which is copolymerized from a first ester, a second ester, a third ester, and a fourth ester. The first ester is formed by esterification of oxalic acid and 1,3-propanediol. The second ester is formed by esterification of an aliphatic diacid and 1,3-propanediol. The third ester is formed by esterification of a quaternary ammonium salt of hydroxy fatty acids. The quaternary ammonium salt of hydroxy fatty acids is prepared by alcoholysis of vegetable oil to obtain hydroxyl-terminated fatty acids, which are then reacted with the quaternary ammonium salt compound. The fourth ester is formed by esterification of terephthalic acid and ethylene glycol. The aliphatic diacids include succinic acid, adipic acid, azelaic acid, and sebacic acid. The vegetable oils include palm oil, coconut shell oil, and soybean oil.

[0019] The quaternary ammonium salt of the hydroxy fatty acid has the following structural formula: HO-R1-COONR2R3R4, where R1 is a C6-C22 alkyl chain, and R2, R3, and R4 are C1-C4 alkyl chains.

[0020] The molar ratio of the first ester, the second ester, the third ester, and the fourth ester is 1:(1.5~2.5):(0.5~1.0):(4.0~6.0), and the molar ratio of the first ester, the second ester, the third ester, and the fourth ester is 1:2:0.6:5. Example 1

[0021] 1) Synthesis of quaternary ammonium salt monomers of hydroxy fatty acids: (1) Alcohololysis: 1000g refined palm oil, 200g ethylene glycol and 5g sodium hydroxide catalyst were added to the reactor and stirred at 65°C for 2 hours to obtain a mixture of fatty acid ethylene glycol esters. After washing with water and drying, crude fatty acid ethylene glycol esters were obtained. (2) Reduction: The above fatty acid glycol esters and excess lithium aluminum hydride (LiAlH4) were reacted slowly at 0-5°C for 3 hours in anhydrous tetrahydrofuran (THF), and then the reaction was raised to room temperature for 12 hours. After the reaction was completed, dilute hydrochloric acid was added to quench the reaction, the organic layer was separated, and the mixture was dried and distilled under reduced pressure to obtain the mixed fatty alcohol. (3) Selective oxidation: Dissolve fatty alcohol in dichloromethane, add Jones reagent (CrO3 / dilute H2SO4) dropwise at 0℃, control the reaction temperature to not exceed 5℃, react for 2 hours, monitor the reaction progress by TLC, and terminate the reaction after the alcohol hydroxyl group is basically converted to carboxyl group. The product is extracted, washed with water and dried to obtain hydroxyl-terminated palmitic acid (the main component is 16-hydroxypalmitic acid). (4) Quaternization: Dissolve 100g of 16-hydroxypalmitic acid in 200ml of anhydrous N,N-dimethylformamide (DMF), add 55g of diethylamine as an acid-binding agent, and slowly add 62g of iodomethane dropwise under ice bath cooling. After the addition is complete, heat to 60℃ and react for 8 hours. After the reaction is complete, remove DMF and excess iodomethane by vacuum distillation. Recrystallize the solid product with bio-based ethyl acetate to obtain a white crystalline solid, namely bio-based 16-hydroxypalmitic acid diethylmethyl iodide.

[0022] 2) Preparation of bio-based high-efficiency antibacterial polyester chips: (1) Esterification reaction: In an esterification reactor, 1.0 mol of oxalic acid and 2.0 mol of 1,3-propanediol were added and stirred to prepare a slurry. After purging the air with nitrogen, the esterification reaction was carried out at 170°C under a pressure of 0.25 MPa. When the amount of distilled water reached 95% (34.2 g) of the theoretical value (about 36 g), the reaction was considered to have reached its endpoint, and the first ester was obtained. In another esterification vessel, 2.0 mol of adipic acid and 4.0 mol of 1,3-propanediol were added and stirred to prepare a slurry. The esterification reaction was carried out at 0.25 MPa and 200 °C. To ensure complete conversion, the reaction time was extended by 20% until the distillate water reached 98% (70.6 g) of the theoretical value (about 72 g), thus obtaining the second esterified product. 417.4 g of the synthesized 16-hydroxypalmitoyltrimethylamine iodide and 1.0 mol of its corresponding acid group were premixed with a small amount of 1.0 mol of 1,3-propanediol and added to the reaction system. The esterification reaction was carried out at 0.2 MPa and 180 °C until no distilled water was produced, ensuring that the terminal carboxyl and terminal hydroxyl groups fully participated in the reaction, and the third esterified product was obtained. In a terephthalic acid (PTA) slurry reactor, 5.0 mol of PTA and 9.0 mol of ethylene glycol were added and stirred to prepare a slurry. The esterification reaction was carried out at 0.25 MPa and 250 °C until the distillate water reached more than 96% of the theoretical value, and the fourth ester (mainly BHET) was obtained. (2) Condensation polymerization: Mixing and Transfer: The first, second, third, and fourth esters were transferred to a prepolymerization reactor in a molar ratio of 1:2:0.6:5. 0.45 g of antimony glycolate catalyst (0.03% of the total acid weight) and 0.45 g of triphenyl phosphate stabilizer (0.03% of the total acid weight) were added. The proportion of the quaternary ammonium salt monomer of hydroxy fatty acids to the total acid molars was approximately 0.6 / (1+2+0.6+5)≈6.98%. Prepolymerization (low vacuum): The temperature is slowly increased to 260℃ while the vacuum is gradually reduced. The pressure is steadily reduced to an absolute pressure of 450Pa within 40 minutes, and the reaction is carried out for 50 minutes under these conditions. This stage enhances the transesterification and copolymerization between the esters, forming a uniform prepolymer. Sampling analysis shows that the intrinsic viscosity of the prepolymer is about 0.15dL / g, and the end carboxyl group content is stable at 380mol / t. Final polycondensation (high vacuum): The material is transferred into the final polycondensation reactor, and a high vacuum is further drawn to reduce the pressure to below 80 Pa absolute pressure within 30 minutes. The temperature is controlled at 275℃, and the reaction is carried out for 90 minutes under these conditions. Through precise vacuum and temperature control, the polycondensation is ensured to proceed smoothly with fewer side reactions. When the stirring power reaches the set value (corresponding to an intrinsic viscosity of approximately 0.62 dL / g), nitrogen is used to press out the melt, which is then water-cooled and pelletized through a casting head to obtain modified low-melting-point copolyester chips.

[0023] The slices were tested by DSC (heating rate 5℃ / min), the intrinsic viscosity was 0.62 dL / g, and the b value was measured by a colorimeter to be 3.5 (L value 88, a value -0.5).

[0024] 3) Preparation of bio-based high-efficiency antibacterial polyester fibers: (1) Spinning Drying: The modified antibacterial polyester chips prepared above were vacuum dried at 120°C for 12 hours, with a moisture content of <30ppm; Spinning: The conventional melt spinning process is adopted, and the screw temperature is set as follows: Zone 1 255℃, Zone 2 265℃, Zone 3 265℃, and the chamber 265℃; Cooling and forming: The spinneret has 144 holes and adopts two-stage ring air cooling. The first stage ring air has a temperature of 50℃, a speed of 2.0m / s, and a humidity of 60%. The second stage ring air has a temperature of 15℃, a speed of 3.0m / s, and a humidity of 80%. The center of the two air ducts is 40cm apart. Winding: The spinning speed is set to 600m / min, and POY pre-oriented yarn is obtained by winding. The spinning process is stable, with no yarn drift or breakage. The initial pressure of the component is 12MPa, and the prediction cycle can reach more than 12 days. (2) Post-spinning (post-drawing treatment) Drawing: A single-zone hot plate drawing machine is used. The filament bundle passes through a 70°C oil bath containing a 5wt% sodium sulfite aqueous solution for lubrication and reduction protection. The drawing ratio is 2.5 times, and there is no filament entanglement on the rollers during the drawing process. Crimping: The filament bundle enters the crimping machine at a crimping temperature of 50℃, a main pressure of 0.4MPa, and a back pressure of 0.2MPa. The density of the packing box is adjusted to achieve a crimp count of 8 per 25mm and a crimp degree of 11%. Heat setting and cutting: The curled filaments are relaxed and set in a hot air oven at 110°C for 3 minutes, and then cut into short fibers to obtain bio-based high-efficiency antibacterial polyester fibers.

[0025] Performance tests were conducted on the fibers: (1) Mechanical properties: Single filament fineness 1.8 dtex, breaking strength 3.30 cN / dtex, breaking elongation 35%; (2) Antibacterial properties: Referring to GB / T 20944.3-2008 (shaking method), the fiber samples were tested. The inhibition rate against Staphylococcus aureus (ATCC 6538) was 99.3%, against Escherichia coli (ATCC 25922) was 99.7%, and against Candida albicans (ATCC 10231) was 99.5%. (3) Odor evaluation: Referring to the industry sensory evaluation method, 5 professionals conducted olfactory identification on the fiber sample and comprehensively evaluated the odor level as 4.0 (almost no odor). Example 2

[0026] Boundary experiments were conducted with extremely low addition levels of quaternary ammonium salts of hydroxy fatty acids to investigate whether acceptable antibacterial effects could be achieved while maintaining excellent overall performance when the amount of antimicrobial monomer added was extremely low, thereby determining the lower limit of the effectiveness of the technical solution of this invention. 1) Synthesis of quaternary ammonium salt monomers of hydroxy fatty acids: The same procedure as in Example 1 was followed to prepare bio-based 16-hydroxypalmitoyldiethylmethyl iodide.

[0027] 2) Preparation of bio-based high-efficiency antibacterial polyester chips: (1) Formulation design: The molar ratio of the first, second, third, and fourth esters was designed to be 1:2:0.15:5, meaning that the proportion of the amount of hydroxy fatty acid quaternary ammonium salt monomer added to the total molar amount of acid was: 0.15 / (1+2+0.15+5) ≈ 1.83% (approximately 1.8%). (2) Esterification and polycondensation reactions: All process parameters, including temperature, pressure, time, catalyst / stabilizer type and dosage (calculated based on the adjusted total acid weight) at each stage, are strictly consistent with those in Example 1. The slices were analyzed by DSC: melting point 120.8℃, intrinsic viscosity: 0.63dL / g, hue: b value 2.8, white color, superior to all other embodiments.

[0028] 3) Preparation of bio-based high-efficiency antibacterial polyester fibers: All spinning and post-processing parameters are completely consistent with those in Example 1.

[0029] Performance tests were conducted on the fibers: (1) Mechanical properties: single filament fineness 1.8 dtex, breaking strength 3.30 cN / dtex; (2) Antibacterial properties: According to GB / T 20944.3-2008 (shaking method), the inhibition rate against Staphylococcus aureus was 85.6%, the inhibition rate against Escherichia coli was 86.9%, and the inhibition rate against Candida albicans was 83.2%. (3) Odor evaluation: The overall odor level is rated as 4.0 (almost no odor).

[0030] The performance test results show that when the addition amount is as low as about 1.8%, the fiber still exhibits a clear antibacterial effect (antibacterial rate > 80%). This proves that even a very low content of reactive quaternary ammonium salt monomer can effectively impart antibacterial properties to the material. However, its antibacterial efficiency has dropped to the level of 85%-87%, failing to reach the ultra-high efficiency of Example 1 (> 99%), and also failing to reach the high efficiency standard in the conventional sense (usually considered to be ≥ 90% or ≥ 95%). Therefore, in order to ensure stable and efficient antibacterial performance, it is necessary to maintain a certain monomer addition threshold. Example 3

[0031] A comparative experiment was conducted with low addition levels of quaternary ammonium hydroxypalmitate salt to investigate the effect of low antibacterial monomer addition on the overall properties of the fiber. 1) Synthesis of quaternary ammonium salt monomers of hydroxy fatty acids: The same procedure as in Example 1 was followed to prepare bio-based 16-hydroxypalmitoyldiethylmethyl iodide.

[0032] 2) Preparation of bio-based high-efficiency antibacterial polyester chips: (1) Formulation design: The molar ratio of the first, second, third, and fourth esters was designed to be 1:2:0.3:5, meaning the proportion of the added hydroxy fatty acid quaternary ammonium salt monomer to the total molar amount of acid was approximately 0.3 / (1+2+0.3+5)≈3.6%. The absolute amounts of oxalic acid, adipic acid, and PTA should be adjusted accordingly, but the molar ratio should remain unchanged. (2) Esterification and polycondensation reactions: All process parameters, including temperature, pressure, and time at each esterification stage, temperature, vacuum, and reaction time at pre-condensation and final condensation, and the type and amount of catalyst / stabilizer (by weight percentage of total acid), are strictly consistent with those in Example 1. DSC analysis of the slices showed: melting point 119.5℃, intrinsic viscosity 0.62 dL / g, hue: b value 3.1. Due to the reduction in the number of introduced quaternary ammonium salt ion groups, the product color was whiter.

[0033] 3) Preparation of bio-based high-efficiency antibacterial polyester fibers: All spinning and post-processing parameters, including drying conditions, spinning temperature, cooling conditions, spinning speed, sheath-to-core ratio, drawing oil bath conditions, and crimping parameters, are completely consistent with those in Example 1.

[0034] Performance tests were conducted on the fibers: (1) Mechanical properties: The fineness of the single filament is 1.8 dtex, and the breaking strength is 3.40 cN / dtex, which is slightly higher than that of Example 1 (3.30 cN / dtex). This may be related to the slightly higher crystallinity and more uniform melt quality. (2) Antibacterial properties (key indicators): According to GB / T 20944.3-2008 (shaking method) test, the inhibition rate against Staphylococcus aureus is 98.2%, the inhibition rate against Escherichia coli is 98.5%, and the inhibition rate against Candida albicans is 97.9%. (3) Odor evaluation: The overall odor level is rated as 4.0 (almost no odor).

[0035] The performance test results show that the antibacterial rate remains at an extremely high level (>97%), but there is a measurable and systematic decrease compared to Example 1 (>99.3%). This indicates that even with a low addition amount, the reactive monomer can still provide strong antibacterial function, but a certain critical addition amount may be required to achieve ultra-high efficiency (>99%). Example 4

[0036] A comparative experiment was conducted with a moderately high addition level (optimization range) to examine the overall balance performance based on Example 1 (7%) by selecting a moderately high addition level. 1) Synthesis of bio-based hydroxy fatty acid quaternary ammonium salt monomers: It is exactly the same as Example 1.

[0037] 2) Preparation of bio-based high-efficiency antibacterial polyester chips: (1) Formulation design: The molar ratio of the first, second, third, and fourth esters was designed to be 1:2:0.9:5, meaning the proportion of the added hydroxy fatty acid quaternary ammonium salt monomer to the total molar amount of acid was approximately 0.9 / (1+2+0.9+5)≈10.1%. (2) Esterification and polycondensation reactions: All process parameters are strictly consistent with those in Example 1.

[0038] DSC analysis of the slices revealed the following: melting point 115.0℃, intrinsic viscosity 0.62 dL / g, and hue: b-value 4.0.

[0039] 3) Preparation of bio-based high-efficiency antibacterial polyester fibers: All spinning and post-processing parameters, including drying conditions, spinning temperature, cooling conditions, spinning speed, sheath-to-core ratio, drawing oil bath conditions, and crimping parameters, are completely consistent with those in Example 1.

[0040] Performance tests were conducted on the fibers: (1) Mechanical properties: Strength 3.18 cN / dtex; (2) Antibacterial properties: Staphylococcus aureus 99.6%, Escherichia coli 99.7%, Candida albicans 99.4%; (3) Odor evaluation: The overall odor level is rated as 4.0 (almost no odor). Example 5

[0041] Comparative experiments were conducted with high addition levels of quaternary ammonium salts of hydroxy fatty acids to investigate the effects of higher antibacterial monomer addition levels on fiber properties, particularly spinnability and crystallization behavior. 1) Synthesis of quaternary ammonium salt monomers of hydroxy fatty acids: It is exactly the same as Example 1.

[0042] 2) Preparation of bio-based high-efficiency antibacterial polyester chips: (1) Formulation design: The molar ratio of the first, second, third, and fourth esters was designed to be 1:2:1.2:5, meaning the proportion of the added hydroxy fatty acid quaternary ammonium salt monomer to the total molar amount of acid was approximately 1.2 / (1+2+0.9+5)≈13.0%. (2) Esterification and polycondensation reactions: All process parameters are strictly consistent with those in Example 1.

[0043] Process observation: In the final polycondensation stage, the reaction time required to reach the same intrinsic viscosity was extended by about 10 minutes compared to Example 1, indicating that the increase of bulky side-chain monomers has a steric hindrance effect on polycondensation kinetics.

[0044] DSC analysis of the slices revealed the following: melting point 112.5℃, intrinsic viscosity 0.61 dL / g, hue b value 4.5. The increased content of ionic groups resulted in a slight yellowing of the product color.

[0045] 3) Preparation of bio-based high-efficiency antibacterial polyester fibers: All spinning and post-processing parameters are completely consistent with those in Example 1; Observation of the spinning process: The elasticity of the melt increased slightly during spinning, and the nascent fibers felt slightly fluffy, but no broken ends or loose fibers appeared, and the pressure of the components increased slightly faster.

[0046] Performance tests were conducted on the fibers: (1) Mechanical properties: The fineness of the single filament is 1.8 dtex, and the breaking strength is 3.05 cN / dtex. The strength has decreased, which is directly related to the decrease in crystallinity. (2) Antibacterial properties: inhibition rate against Staphylococcus aureus: 99.8%, inhibition rate against Escherichia coli: 99.9%, inhibition rate against Candida albicans: 99.7%; (3) Odor evaluation: The overall odor level is rated as 4.0 (almost no odor).

[0047] The performance test results show that the antibacterial performance is at its peak, with an inhibition rate of nearly 100%, indicating that increasing the amount of monomer can further enhance the antibacterial efficacy.

[0048] Comparative Example 1 Using a solvent-containing PHA oligomer as a control (problems recurring with the old process): 1) Synthesis of solvent-containing polyhydroxy fatty acid ester (PHA) oligomers (taking poly(3-hydroxybutyrate), PHB as an example): (1) Alcohololysis: In a reactor equipped with a reflux condenser and nitrogen protection, add 1000g of high molecular weight poly(3-hydroxybutyrate) (PHB, η=2.0 dL / g), 2000mL of diethylene glycol dimethyl ether as solvent, and 500mL of 1,3-propanediol as alcoholysis agent, add 5.0g of dibutyltin dilaurate catalyst, heat in an oil bath to 140℃, and stir vigorously at this temperature for 15 hours; (2) Post-processing: After the reaction is completed, the reaction mixture is cooled to 80°C and subjected to vacuum distillation at -0.095 MPa to distill off excess propylene glycol and a small amount of low-boiling fraction. Since diethylene glycol dimethyl ether has a high boiling point (162°C) and good compatibility with the product, about 10 wt% of the solvent remains in the viscous product after distillation. The product obtained is a deep yellow viscous liquid, which is a mixture of low molecular weight PHB oligomer (Mn≈1800 g / mol) with hydroxyl-terminated ends and diethylene glycol dimethyl ether. This mixture is used directly as the third esterification reaction component without further purification.

[0049] 2) Preparation of antibacterial polyester chips: (1) Esterification reaction: In an esterification reactor, 1.0 mol of oxalic acid and 2.0 mol of 1,3-propanediol were added and stirred to prepare a slurry. After purging with nitrogen, the esterification reaction was carried out at 160°C under a pressure of 0.25 MPa. The reaction was terminated when the distillate water reached 95% of the theoretical value, and the first ester was obtained. In another esterification vessel, 2.0 mol of adipic acid and 4.0 mol of 1,3-propanediol were added and slurryed. The esterification reaction was carried out at 0.25 MPa and 180 °C until the endpoint to obtain the second esterified product. The above-synthesized solvent-containing PHB oligomer mixture (weighed at about 407g, of which about 1.0mol of carboxyl groups corresponding to PHB oligomer units) was added to the reaction system and esterification was carried out at 0.25 MPa and 160℃. During the reaction, the residual solvent caused the system temperature control and distillation rate to be unstable. In a terephthalic acid (PTA) slurry reactor, 5.0 mol of PTA and 9.0 mol of ethylene glycol were added and stirred to prepare a slurry. The slurry was then esterified at 0.25 MPa and 240 °C to the endpoint to obtain the fourth esterified product. The target structural unit molar ratio of first ester: second ester: third ester: fourth ester = 1:2:1:5; (2) Condensation polymerization: Mixing and Transfer: Transfer all the above esterified products to the prepolymerization reactor, and add 0.45g of antimony glycolate catalyst and 0.45g of triphenyl phosphate stabilizer; Prepolymerization: When the system is heated to 260℃ and vacuuming begins, the residual diethylene glycol dimethyl ether and ethylene glycol are rapidly extracted together, causing violent foaming and pressure fluctuations in the system. It must be operated extremely slowly. Finally, the pressure is reduced to 500Pa within 60 minutes, and the reaction is carried out for 40 minutes under these conditions. Sampling and analysis show that the prepolymer end carboxyl content fluctuates greatly, reaching 420mol / t. Final polycondensation: The material is transferred into the final polycondensation kettle, and a high vacuum is drawn to an absolute pressure of 90 Pa. The temperature is controlled at 275℃. Due to the presence of trace solvents and their decomposition products, the polycondensation process is accompanied by competitive thermal degradation, and the stirring power curve shows abnormal fluctuations. The material is discharged after 90 minutes of reaction. Slice DSC analysis showed a melting point of 149.6℃, intrinsic viscosity of 0.65 dL / g, and a b-value of 8.5 (L-value 82.3, a-value +1.5) measured by a colorimeter. GC-MS headspace analysis confirmed the presence of diethylene glycol dimethyl ether residue.

[0050] 3) Preparation of modified antibacterial fibers: (1) Pre-spinning: Drying: The slices were vacuum dried at 120°C for 12 hours; Spinning: The screw temperature is set as follows: Zone 1 255℃, Zone 2 265℃, Zone 3 265℃, and the housing temperature is 265℃. The core layer temperature is the same as in Example 1. Cooling and shaping: 144 holes in the spinneret. The same two-stage annular airflow conditions as in Example 1 were used (50℃ / 2.0 m / s; 15℃ / 3.0 m / s, 40 cm interval). Winding: The spinning speed is 600 m / min, and the spinning process is extremely unstable: the nascent fiber is uneven, and obvious filaments can be seen at the side blowing point; there are a large number of defects such as stiff filaments and fuzz on the surface of the wound yarn cake; an irritating odor can be detected near the spinning box; the initial pressure of the component is 14 MPa, and the pressure rises to 22 MPa after 48 hours of operation. (2) Post-spinning (post-drawing treatment): Drawing: The same oil bath drawing conditions as in Example 1 (70°C, 5 wt% sodium sulfite) were used. Roller wrapping occurred frequently during the drawing process, averaging over 15 times per ton of yarn. Curling: Curling temperature 50℃, main pressure 0.4MPa, back pressure 0.2MPa, number of curls 8 / 25mm; Heat setting and cutting: Set in an oven at 110℃ for 3 minutes, then cut into short fibers.

[0051] Performance tests were conducted on the fibers: (1) Mechanical properties: Single filament fineness 1.8 dtex, breaking strength 3.0 cN / dtex, breaking elongation 42%, strength CV value > 8%; (2) Antibacterial properties: According to GB / T 20944.3-2008 (shaking method), the inhibition rate against Staphylococcus aureus was 94.8%, against Escherichia coli was 95.1%, and against Candida albicans was 93.7%. (3) Odor evaluation: After professional olfaction assessment, it was rated as level 3.5 (a noticeable odor can be detected); (4) Appearance: The fiber is yellowish in color and has poor whiteness.

[0052] Comparative Example 2 Blank control group experiment: Based on Example 1, without adding any hydroxy fatty acid quaternary ammonium salt monomers, copolymerization was carried out only by esterifications of oxalic acid (I), adipic acid (II) and PTA (IV), with the molar ratio adjusted to I:II:IV = 1:2:5 (the total number of moles is similar to the original system), and the polymerization and spinning process parameters were kept as consistent as possible with those of Example 1.

[0053] Performance tests were conducted on the fibers: (1) The polymerization process was very smooth, and the slices were white (b value about 2.0); (2) The polyester obtained is a common aliphatic-aromatic copolyester with a melting point of 155℃. The spinning process is smooth and the resulting fiber strength is 3.1 cN / dtex. (3) Antibacterial performance test: The test was conducted strictly in accordance with the same antibacterial test method as in the example (GB / T 20944.3-2008). The results showed that the inhibition rate against Staphylococcus aureus, Escherichia coli and Candida albicans was less than 10%, indicating that the fiber itself does not have antibacterial function.

[0054] The performance test results show that the blank control group strongly demonstrates that the hydroxy fatty acid quaternary ammonium salt structural unit introduced in this invention is the fundamental reason for the fiber's efficient and long-lasting antibacterial function, rather than due to other process conditions or structural units. The overall fiber test results are shown in the table below: project Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Molar ratio of quaternary ammonium salt esters of hydroxy fatty acids 0.6 0.15 0.3 0.9 1.2 1.0 0 Melting point (°C) 118.0 120.8 119.5 115.0 112.5 149.6 154.8 Hue b value 3.5 2.8 3.1 4.0 4.5 8.5 1.8 Intrinsic viscosity (dL / g) 0.62 0.63 0.62 0.62 0.61 0.65 0.60 Fiber strength (cN / dtex) 3.30 3.45 3.40 3.18 3.05 3.00 3.12 Staphylococcus aureus inhibition rate (%) 99.3 85.6 98.2 99.6 99.8 94.8 6.3 Escherichia coli inhibition rate (%) 99.7 86.9 98.5 99.7 99.9 95.1 5.8 Candida albicans inhibition rate (%) 99.5 83.2 97.9 99.4 99.7 93.7 7.1 As shown in the table above, by introducing reactive hydroxy fatty acid quaternary ammonium salt monomers and optimizing the solvent-free polymerization process, the core technical problem of color difference and yellowing caused by the use of solvents in the existing preparation process of bio-based antibacterial polyester fibers has been effectively solved. Experimental data show that when the monomer addition amount is 4% to 7% of the total acid molar number, the fiber not only achieves an ultra-high and long-lasting antibacterial rate of >99% against three common bacteria, but more importantly, it has a white appearance (b value ≤3.5) and a high bio-based content, which completely overcomes the defects of the old process and effectively expands the application of bio-based functional fibers in the field of high-quality textiles.

[0055] In summary, these are merely preferred embodiments of the present invention and are not intended to limit the scope of the invention. All equivalent variations and modifications made in accordance with the shape, structure, features, and spirit of the claims of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A bio-based high-efficiency antibacterial polyester fiber, characterized in that: It is copolymerized from a first ester, a second ester, a third ester, and a fourth ester. The first ester is formed by esterification of oxalic acid and 1,3-propanediol. The second ester is formed by esterification of an aliphatic dicarboxylic acid and 1,3-propanediol. The third ester is formed by esterification of a quaternary ammonium salt of hydroxy fatty acids. The quaternary ammonium salt of hydroxy fatty acids is prepared by alcoholysis of vegetable oil to obtain hydroxyl-terminated fatty acids, which are then reacted with the quaternary ammonium salt compound. The fourth ester is formed by esterification of terephthalic acid and ethylene glycol.

2. The bio-based high-efficiency antibacterial polyester fiber according to claim 1, characterized in that: The aliphatic dicarboxylic acids include succinic acid, adipic acid, azelaic acid, and sebacic acid.

3. The bio-based high-efficiency antibacterial polyester fiber according to claim 1, characterized in that: The vegetable oils include palm oil, coconut shell oil, and soybean oil.

4. The bio-based high-efficiency antibacterial polyester fiber according to claim 1, characterized in that: The quaternary ammonium salt of the hydroxy fatty acid has the following structural formula: HO-R1-COONR2R3R4, where R1 is a C6-C22 alkyl chain, and R2, R3, and R4 are C1-C4 alkyl chains.

5. The bio-based high-efficiency antibacterial polyester fiber according to claim 1, characterized in that: The molar ratio of the first ester, the second ester, the third ester, and the fourth ester is 1:(1.5-2.5):(0.5-1.0):(4.0-6.0).

6. The bio-based high-efficiency antibacterial polyester fiber according to claim 1, characterized in that: The molar ratio of the first ester, the second ester, the third ester, and the fourth ester is 1:2:0.6:

5.

7. A method for preparing bio-based high-efficiency antibacterial polyester fiber, characterized in that, Includes the following steps: S1 Oxalic acid and 1,3-propanediol are stirred to form a slurry, and esterification reaction is carried out at 150-180°C under a nitrogen atmosphere and a pressure of 0.1-0.3 MPa until the water content reaches more than 90%, thus obtaining the first esterified product. S2. An aliphatic dicarboxylic acid and 1,3-propanediol are stirred to form a slurry. The esterification reaction is carried out at 180-220°C under a nitrogen atmosphere and a pressure of 0.1-0.3 MPa until the water content reaches more than 90%, thus obtaining the second esterified product. S3 The quaternary ammonium salt monomer of hydroxy fatty acid is premixed with a small amount of ethylene glycol and esterified at 160-200°C under a nitrogen atmosphere and a pressure of 0.1-0.3 MPa until no distilled water is produced, ensuring that the terminal carboxyl and terminal hydroxyl groups fully participate in the reaction, and the third esterified product is obtained. S4 involves mixing terephthalic acid and ethylene glycol to form a slurry, and then carrying out an esterification reaction at 240–260°C under a nitrogen atmosphere and a pressure of 0.1–0.3 MPa until the water content reaches more than 90%, thus obtaining the fourth esterified product. S5 mixes the first ester, second ester, third ester and fourth ester in molar ratio, adds catalyst and stabilizer, and under negative pressure, the system pressure is pumped from atmospheric pressure to an absolute pressure of 500 Pa, and the reaction is carried out at 255-265℃ for 40-60 min. Continue evacuating the vacuum to reduce the reaction pressure to below 100 Pa absolute pressure, raise the temperature to 270–280 °C, and continue the reaction for 80–100 min. Through vacuum control and temperature control, the melt viscosity is stabilized, thereby reducing the hue b value of the polyester fiber. S6 uses a spinning method to melt-spin polyester at a spinning temperature of 255–270℃ and a spinning speed of 600–1000 m / min. It has two cooling rings with air blowing: the first air temperature is 50–80℃ and the air speed is 1.5–2.5 m / s, the second air temperature is 14–20℃ and the air speed is 2.5–3.5 m / s, and the distance between the two air rings is 30–50 cm. S7 involves drawing, washing, crimping, cutting, and drying the fiber filaments. The drawing process is carried out using an oil bath at a temperature of 65–75°C. The oil contains 5–10 wt% sodium sulfite, the drawing ratio is 2.5–2.8, and the crimping temperature is 50–60°C. This process yields bio-based high-efficiency antibacterial polyester fiber.

8. The method for preparing bio-based high-efficiency antibacterial polyester fiber according to claim 7, characterized in that: The preparation of the quaternary ammonium salt monomer of hydroxy fatty acids in step S3 includes the following steps: (1) Alcohololysis: Vegetable oil, ethylene glycol and sodium hydroxide were added to the reaction vessel at a mass ratio of 200:40:1 and stirred at 65°C for 2 hours. After washing with water and drying, crude fatty acid ethylene glycol esters were obtained. (2) Reduction: Fatty acid glycol esters and excess lithium aluminum hydride (LiAlH4) were reacted slowly in anhydrous tetrahydrofuran (THF) at 0-5°C for 3 h, and then the reaction was raised to room temperature for 12 h. After the reaction was completed, dilute hydrochloric acid was added to quench the reaction, the organic layer was separated, dried and distilled under reduced pressure to obtain mixed fatty alcohols. (3) Selective oxidation: The fatty alcohol was dissolved in dichloromethane, and Jones' reagent (CrO3 / dilute H2SO4) was added dropwise at 0℃. The reaction temperature was controlled not to exceed 5℃, and the reaction was carried out for 2 hours. The reaction progress was monitored by TLC. After the alcohol hydroxyl group was basically converted to the carboxyl group, the reaction was terminated. After extraction, washing with water and drying, hydroxyl-terminated fatty acids were obtained. (4) Quaternization: Dissolve an appropriate amount of hydroxy fatty acid in 200 ml of anhydrous N,N-dimethylformamide (DMF), add diethylamine as an acid-binding agent, and slowly add iodomethane dropwise under ice bath cooling. After the addition is complete, heat to 60 °C and react for 8 h. After the reaction is complete, remove DMF and excess iodomethane by vacuum distillation. Recrystallize the solid product with ethyl acetate to obtain a white crystalline solid, namely the quaternary ammonium salt monomer of hydroxy fatty acid.

9. The method for preparing bio-based high-efficiency antibacterial polyester fiber according to claim 7, characterized in that: In step S3, the hydroxy fatty acid quaternary ammonium salt monomer accounts for 1 to 8% of the total molar amount of the dicarboxylic acid, preferably 6 ± 0.5%.

10. The method for preparing bio-based high-efficiency antibacterial polyester fiber according to claim 7, characterized in that: In step S5, the catalyst is antimony glycolate and tetrabutyl titanate, and the stabilizer is triphenyl phosphate. By mass fraction, the catalyst accounts for 0.01 to 0.05% of the total acid content, and the stabilizer accounts for 0.01 to 0.05% of the total acid content.