Antibacterial polylactic acid, nonwoven fabric based on the polylactic acid and application to pet wipes

Abstract

This invention relates to the field of polymer materials technology, specifically to an antibacterial polylactic acid (PLA), a nonwoven fabric based on the PLA, and its application in pet wipes. The antibacterial PLA, by weight, comprises: 65-92 parts of PLA matrix resin, 3-10 parts of an antibacterial agent composition, 0.5-5 parts of a bio-based chain extender, 3-15 parts of a bio-based toughening agent, 0.5-8 parts of a polydicarboxylic acid, and 0.1-2 parts of a bio-based nucleating agent; wherein the antibacterial agent composition contains chitosan quaternary ammonium salt and a supported nano-inorganic antibacterial material. The PLA spunlace nonwoven fabric, prepared by melt spinning, web formation, and hydroentangling reinforcement of the antibacterial PLA, possesses excellent dry / wet mechanical strength, a soft feel, breathability, and highly efficient and long-lasting broad-spectrum antibacterial properties, making it particularly suitable for pet wipes where hygiene and safety requirements are high.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to an antibacterial polylactic acid, a nonwoven fabric based on the polylactic acid, and its application in pet wipes. Background Technology

[0002] With the rapid development of the pet economy and the increasing emphasis consumers place on pet health care, the market demand for pet wipes, as a convenient product for daily cleaning and grooming, continues to grow. At the same time, the increasing global awareness of environmental protection is driving the trend of disposable hygiene products shifting towards bio-based biodegradable materials. Polylactic acid (PLA), as a fully biodegradable polyester material derived from renewable plant resources, possesses excellent biocompatibility and processing properties, and is considered one of the ideal candidates to replace traditional petroleum-based materials in the preparation of environmentally friendly pet wipe substrates.

[0003] Currently, to impart antibacterial properties to polylactic acid (PLA) nonwoven fabrics to meet the high hygiene and safety requirements of pet wipes, the main technical approaches include: 1. Physical blending method: This involves directly melt-blending inorganic antibacterial agents (such as nano-silver, nano-zinc oxide, silver-loaded zeolite, etc.) or organic antibacterial agents (such as quaternary ammonium salts, triclosan, etc.) with the PLA matrix. This method often faces challenges such as poor compatibility, easy agglomeration of antibacterial agents leading to uneven dispersion, affecting spinning stability and the mechanical properties of the nonwoven fabric; furthermore, some inorganic antibacterial agents may raise concerns about biosafety, while small-molecule organic antibacterial agents have poor heat resistance and are prone to decomposition or volatilization at processing temperatures. 2. Finishing method: This involves impregnating, spraying, or coating the already formed PLA nonwoven fabric, grafting or loading antibacterial components. While this method can preserve the mechanical properties of the substrate, the introduced coating often has weak adhesion to the PLA matrix and is easily detached under friction such as wiping, resulting in a short-lasting antibacterial effect. Simultaneously, the outer coating may clog the pores of the nonwoven fabric, affecting its breathability, soft feel, and integrity in biodegradation. Third, the modified polylactic acid method, such as introducing antibacterial structural units into the PLA molecular chain through copolymerization, involves complex synthesis steps and high costs, making it difficult to meet the needs of large-scale industrial production. In summary, existing technologies struggle to achieve an ideal balance between highly efficient and long-lasting antibacterial properties, good processing and mechanical properties, fully biodegradable characteristics, and controllable costs.

[0004] Therefore, developing a fully bio-based polylactic acid material that combines efficient and stable antibacterial properties, excellent processability and mechanical strength, and is suitable for the requirements of hygiene products such as pet wipes, has important practical significance and application value. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to provide an antibacterial polylactic acid, which is prepared by comprising the following components in parts by weight: 65-92 parts of polylactic acid matrix resin, 3-10 parts of antibacterial agent composition, 0.5-5 parts of bio-based chain extender, 3-15 parts of bio-based toughening agent, 0.5-8 parts of polydicarboxylic acid, and 0.1-2 parts of bio-based nucleating agent; The antibacterial composition comprises a first antibacterial component and a second antibacterial component; the mass ratio of the first antibacterial component to the second antibacterial component is 1:(0.5-3); the first antibacterial component is chitosan quaternary ammonium salt; and the second antibacterial component is a supported nano-inorganic antibacterial material.

[0006] This invention also discloses a method for preparing antibacterial polylactic acid as described above, comprising the following steps: S1. The carrier material is dispersed in deionized water to form a suspension. A soluble salt solution containing inorganic antibacterial metal ions is added dropwise to the suspension. After the addition is complete, the reaction is carried out. After the reaction is completed, the material is separated, washed, and dried to obtain the supported nano-inorganic antibacterial material, i.e., the second antibacterial component. S2. The second antibacterial component obtained in step S1, the first antibacterial component, the polydicarboxylic acid, and the first part of the bio-based chain extender are premixed to obtain a premix. S3. The premix, the polylactic acid matrix resin, the second part of the bio-based chain extender, the bio-based toughening agent and the bio-based nucleating agent are melt-blended, extruded, cooled and pelletized to obtain the antibacterial polylactic acid.

[0007] Preferably, the polylactic acid matrix resin is L-polylactic acid; the L-polylactic acid has a weight-average molecular weight of 80,000-150,000 and a melt flow rate of 10-35 g / 10 min at 190°C and 2.16 kg load.

[0008] Preferably, the bio-based chain extender is selected from at least one of multifunctional epoxy chain extenders and isocyanate chain extenders; The multifunctional epoxy chain extender includes epoxidized vegetable oil with an epoxy value between 3 and 8; The isocyanate chain extenders include bio-based diisocyanates.

[0009] Preferably, the bio-based toughening agent is selected from at least one of polybutylene adipate terephthalate, polylactic acid-polycaprolactone block copolymer, polyhydroxyalkanoate, and acetylated tributyl citrate; The bio-based toughening agent has a melting point of 50-120℃ and a melt flow rate of 10-100g / 10min at 190℃ and 2.16kg load. The polydicarboxylic acid includes at least one of polysuccinic acid and polyadipic acid; The bio-based nucleating agent is selected from at least one of microcrystalline cellulose, chitin whiskers, phytate or caseinate; the average particle size of the bio-based nucleating agent is 0.5-20 μm.

[0010] Preferably, in S1, the carrier material includes at least one of halloysite nanotubes, montmorillonite, or hydrotalcite; the inorganic antibacterial metal ions are selected from at least one of silver ions, zinc ions, and copper ions. The reaction conditions are stirring at 50-70℃ for 4-8 hours.

[0011] Preferably, in step S2, the first part of the bio-based chain extender accounts for 30%-70% of the total mass of the bio-based chain extender; the premixing temperature is 40-80℃, and the premixing time is 10-60 min.

[0012] Preferably, in step S3, during melt blending, the processing temperature range is 180-200℃ and the screw speed is 100-400rpm.

[0013] This invention also discloses a nonwoven fabric based on antibacterial polylactic acid, wherein the nonwoven fabric is prepared by spinning, web laying, and hydroentangling reinforcement of the antibacterial polylactic acid as described above, specifically comprising: Step (1), spinning: After drying the antibacterial polylactic acid, polylactic acid fiber is obtained by melt spinning, winding, stretching and heat setting processes; Step (2), Web laying: Lay polylactic acid fibers into a web; Step (3), hydroentanglement reinforcement: The fiber web is subjected to hydroentanglement reinforcement treatment and dried to obtain a nonwoven fabric based on antibacterial polylactic acid.

[0014] Preferably, in step (1), the spinning temperature is 190-210℃, the winding speed is 800-2800m / min, the drawing temperature is 75-95℃, the drawing ratio is 2-4 times, the heat setting temperature is 85-105℃, and the fineness of the resulting polylactic acid fiber monofilament is 1-3.5dtex; in step (2), the web laying method is cross-laying, and the web weight is 30-50g / m². 2 In step (3), the hydroentangling pressure is 60-150 bar.

[0015] The present invention also discloses the application of the above-described antibacterial polylactic acid-based nonwoven fabric in pet wipes.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: In this invention, the first antibacterial component, chitosan quaternary ammonium salt, is compounded with the second antibacterial component, a supported nano-inorganic antibacterial material, to construct a multi-level antibacterial system with organic-inorganic synergy. During premixing and melt blending, the positively charged chitosan quaternary ammonium salt molecular chains can be adsorbed onto the negatively charged nano-carrier surface through electrostatic interaction. At the same time, its amine groups and the carboxyl groups of polydicarboxylic acid have reaction potential, while inorganic antibacterial metal ions can coordinate with the groups on the chitosan chains. The contact antibacterial effect of chitosan quaternary ammonium salt and the slow-release antibacterial effect of inorganic ions form a dual antibacterial mechanism, broadening the antibacterial spectrum. Furthermore, through the interaction between components, a stable composite antibacterial unit is initially constructed before processing, effectively avoiding the thermal degradation of single small molecule antibacterial agents or severe aggregation of nanoparticles, laying the foundation for achieving efficient and stable antibacterial performance. In this invention, a polydicarboxylic acid component is introduced. During premixing and subsequent melt blending, the polydicarboxylic acid plays a dual role as a molecular bridge and a reaction medium: its carboxyl groups can interact with the surface of the heterogeneously dispersed nano-inorganic antibacterial material, improving its dispersibility in the polymer melt. More importantly, it can undergo amidation reaction with the amino groups on the chitosan quaternary ammonium salt molecular chain. At the same time, its own and the active groups of the bio-based chain extender can also react with the ends of the polylactic acid molecular chain. The antibacterial component, which is originally easy to migrate or fall off, is indirectly anchored or intertwined in the polylactic acid matrix network through chemical bonds by the polydicarboxylic acid segments, realizing the implantation of antibacterial function. This overcomes the defects of easy peeling off of the coating in the finishing method and poor compatibility in the physical blending method, and endows the material with durable and abrasion-resistant and wash-resistant antibacterial properties. Furthermore, the polydicarboxylic acid introduced in this invention plays a crucial role in enhancing the mechanical properties of the system. During melt blending, the carboxyl groups at the ends of the polydicarboxylic acid molecular chains can undergo esterification with the hydroxyl groups at the ends of the polylactic acid molecular chains, and simultaneously undergo ring-opening reactions with the epoxy groups of the bio-based chain extender to form chain extender or micro-crosslinked structures. This increases the entanglement density and connection strength between polylactic acid molecular chains, thereby significantly improving the dry-state breaking strength of the material. At the same time, by blocking the hydrophilic terminal hydroxyl groups of the polylactic acid molecular chains and restricting the penetration of water molecules into the material through the formed network structure, the polydicarboxylic acid significantly improves the hydrolysis resistance of the material, enabling the nonwoven fabric to maintain high mechanical strength even under wet conditions, with a particularly significant increase in wet strength. In addition, the polydicarboxylic acid itself is an aliphatic polyester structure, and its molecular chains have flexibility, which plays a toughening role between the rigid segments of polylactic acid. This allows the material to undergo a certain degree of conformational adjustment when subjected to bending stress, thereby reducing bending stiffness and giving the nonwoven fabric a superior soft feel. This invention achieves a balance between reactivity and processing stability through a specific process sequence: pre-mixing and activating an antibacterial composition, polydicarboxylic acid, and a bio-based chain extender, followed by melt blending with polylactic acid (PLA) matrix and other components. The pre-mixing step promotes initial interactions and dispersion between the antibacterial components, and between the antibacterial components and the polydicarboxylic acid and some of the chain extenders, creating conditions for uniform dispersion and full reaction in the subsequent molten state. Combined with bio-based toughening agents and nucleating agents, the resulting antibacterial PLA maintains necessary melt flowability and spinning performance while forming a multiphase structure with excellent mechanical properties. The resulting nonwoven fabric, while possessing excellent antibacterial properties, also maintains good mechanical strength, softness, and breathability, meeting the comprehensive performance requirements of pet wipes for the substrate. Attached Figure Description

[0017] Figure 1 The graph shows the results of measuring the dry and wet strength of the nonwoven fabrics prepared in Examples 1-3 and Comparative Examples 1-5 of this invention. Figure 2 The graph shows the results of measuring the softness of the nonwoven fabrics obtained in Examples 1-3 and Comparative Examples 1-5 of this invention. Figure 3 The graph shows the results of the antibacterial properties of the nonwoven fabrics prepared in Examples 1-3 and Comparative Examples 1-5 of this invention. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0019] Example 1: This example provides a method for preparing a nonwoven fabric based on antibacterial polylactic acid, including the following steps: Step 1: Preparation of antibacterial polylactic acid: S1. Halloysite nanotubes (outer diameter 30-50 nm, inner diameter 15-20 nm, length approximately 100-1500 nm) were dispersed in deionized water at a mass-to-volume ratio of 1 g / 100 mL. A uniform suspension was formed by mechanical stirring under ultrasonic (300 W) assistance. Under continuous stirring and in the dark, 0.01 mol / L silver nitrate solution was added dropwise to the suspension, maintaining the pH of the reaction system at 4 during the addition. After the addition was complete, the reaction system was heated to 50 °C and stirred continuously for 8 hours. After the reaction, the mixture was vacuum filtered. The resulting solid was repeatedly washed with deionized water until no white precipitate was formed when the filtrate was tested with sodium chloride solution. The washed solid was dried in a 60 °C vacuum oven to constant weight, ground, and passed through a 600-mesh sieve to obtain silver ion-loaded modified halloysite nanotubes, i.e., the second antibacterial component. X-ray fluorescence spectroscopy (XRF) analysis showed that the silver ion loading was 0.5% of the halloysite nanotube mass. S2. Weigh the raw materials according to the following parts by weight: 1 part of the second antibacterial component obtained in step S1, 2 parts of the first antibacterial component chitosan quaternary ammonium salt (degree of deacetylation 90%, degree of substitution 85%, number average molecular weight 12000), 0.5 parts of polysuccinic acid (number average molecular weight 2000), and 0.15 parts of epoxidized soybean oil (epoxide value 3) (accounting for 30% of the total mass of bio-based chain extender); All the above materials are put into a high-speed mixer. Under nitrogen atmosphere protection, the mixing temperature is set to 40°C and the mixture is mixed at 500 rpm for 60 minutes to obtain a premix. S3. Prepare other components according to the following weight parts: 65 parts of polylactic acid (weight average molecular weight of 80,000, melt flow rate of 35 g / 10 min (190℃, 2.16 kg), optical purity of 96%), 0.35 parts of epoxidized soybean oil (same specifications as S2, accounting for 70% of the total mass of bio-based chain extender), 3 parts of polybutylene adipate terephthalate (melting point of 50℃, melt flow rate of 10 g / 10 min (190℃, 2.16 kg)), and 0.1 parts of microcrystalline cellulose (average particle size of 0.5 μm); The premixed material and all the above components were fed into the main feed port of a twin-screw extruder. The temperature range from the feed port to the die head of the extruder was set as follows: 180℃, 185℃, 188℃, 192℃, 195℃, 198℃, 195℃, 190℃. The screw speed was set to 100 rpm, the average residence time of the material was 5 min, the melt was extruded through the die head and then cooled in a water bath. After being pelletized by a pelletizer, it was vacuum dried at 80℃ for 10 h to obtain the antibacterial polylactic acid granules. Step 2: Preparation of nonwoven fabric based on antibacterial polylactic acid: Step (1), spinning: The above antibacterial polylactic acid granules are placed in a vacuum drying oven and dried at 80℃ and -0.8MPa for 12 hours to make the moisture content less than 200ppm. The dried granules are then fed into a melt spinning machine for melt spinning. The temperature of the spinning box is set to 190℃. The melt is extruded through a spinneret (orifice diameter of 0.25mm) and cooled and shaped by side blowing (wind speed 0.5m / s, temperature 20℃). The winding speed is 800m / min to obtain nascent fibers. The nascent fibers are stretched at 75℃ with a stretch ratio of 2, and then heat-set at 85℃ to obtain polylactic acid fibers with a single filament fineness of 3.5dtex. Step (2), Web laying: The antibacterial polylactic acid fiber obtained by spinning is opened and combed by a mechanical carding machine, and then the fiber layer is folded and laid back and forth by a cross-laying machine to form a uniform fiber web with a basis weight of 30g / m². Step (3), hydroentangling reinforcement: The laid fiber web is sent into the hydroentangling reinforcement equipment. Two hydroentangling heads are used, and the hydroentangling pressure is set to 60 bar. The front hydroentangling reinforcement of the fiber web is carried out. The hydroentangled nonwoven fabric is sent into a hot air circulating oven and dried at 80°C until the moisture content is less than 5%, thus obtaining the nonwoven fabric based on antibacterial polylactic acid.

[0020] Example 2: This example provides a method for preparing a nonwoven fabric based on antibacterial polylactic acid, including the following steps: Step 1: Preparation of antibacterial polylactic acid: S1. Hydrotalcite (average particle size 0.4-0.6μm, specific surface area 6-12m²) 2 The hydrotalcite ( / g) was dispersed in deionized water at a mass-to-volume ratio of 1g / 100mL. A uniform suspension was formed by mechanical stirring under ultrasonic (300W) assistance. Under continuous stirring and in the dark, a 1mol / L mixed solution of silver nitrate and zinc acetate (molar ratio of silver ions to zinc ions 1:1) was added dropwise to the suspension. The pH of the reaction system was maintained at 7 during the addition. After the addition was complete, the reaction system was heated to 70℃ and stirred vigorously for 4 hours. After the reaction, the mixture was vacuum filtered. The resulting solid was repeatedly washed with deionized water until no white precipitate was formed when tested with sodium chloride solution. The washed solid was dried in a 60℃ vacuum oven to constant weight, ground, and passed through a 600-mesh sieve to obtain silver ion / zinc ion-loaded modified hydrotalcite, i.e., the second antibacterial component. X-ray fluorescence spectroscopy analysis showed that the total loading of silver and zinc ions was 5% of the mass of the hydrotalcite. S2. Weigh the raw materials according to the following parts by weight: 7.5 parts of the second antibacterial component obtained in step S1, 2.5 parts of the first antibacterial component chitosan quaternary ammonium salt (degree of deacetylation 95%, degree of substitution 95%, number average molecular weight 48000), 8 parts of polyadipic acid (number average molecular weight 6000), and 3.5 parts of bio-based diisocyanate (bio-based chain extender derived from castor oil, NCO content 16%) (accounting for 70% of the total mass of bio-based chain extender). All the above materials are put into a high-speed mixer. Under nitrogen atmosphere protection, the mixing temperature is set to 80°C and the mixture is mixed at 800 rpm for 10 minutes to obtain a premix. S3. Prepare other components according to the following weight parts: 92 parts of polylactic acid (weight average molecular weight of 150,000, melt flow rate of 10g / 10min (190℃, 2.16kg), optical purity of 99%), 1.5 parts of bio-based diisocyanate (same specifications as S2, accounting for 30% of the total mass of bio-based chain extender), 15 parts of polylactic acid-polycaprolactone block copolymer (melting point of 120℃, melt flow rate of 100g / 10min (190℃, 2.16kg)), and 2 parts of chitin whiskers (average length of 20μm). The premixed material and all the above components were fed into the main feed port of a twin-screw extruder. The temperature range from the feed port to the die head of the extruder was set as follows: 180℃, 185℃, 188℃, 192℃, 195℃, 198℃, 195℃, 190℃. The screw speed was set to 400 rpm, the average residence time of the material was 1 min, the melt was extruded through the die head and then cooled in a water bath. After being pelletized by a pelletizer, it was vacuum dried at 80℃ for 10 h to obtain the antibacterial polylactic acid granules. Step 2: Preparation of nonwoven fabric based on antibacterial polylactic acid: Step (1), spinning: The above antibacterial polylactic acid granules are placed in a vacuum drying oven and dried at 80℃ and -0.8MPa for 12 hours to make the moisture content less than 200ppm. The dried granules are then fed into a melt spinning machine for melt spinning. The temperature of the spinning box is set to 210℃. The melt is extruded through a spinneret (orifice diameter of 0.15mm) and cooled and shaped by side blowing (wind speed 0.5m / s, temperature 20℃). The winding speed is 2500m / min to obtain nascent fibers. The nascent fibers are stretched at 95℃ with a stretch ratio of 4 times, and then heat-set at 105℃ to obtain polylactic acid fibers with a single filament fineness of 1dtex. Step (2), Web laying: The antibacterial polylactic acid fiber obtained by spinning is opened and combed by a mechanical carding machine, and then the fiber layer is folded and laid back and forth by a cross-laying machine to form a uniform fiber web with a basis weight of 50g / m². Step (3), hydroentangling reinforcement: The laid fiber web is sent into the hydroentangling reinforcement equipment, using 2 hydroentangling heads, and the hydroentangling pressure is set to 150 bar to perform front hydroentangling reinforcement on the fiber web. The hydroentangled nonwoven fabric is sent into a hot air circulating oven and dried at 80°C until the moisture content is less than 5%, thus obtaining the nonwoven fabric based on antibacterial polylactic acid.

[0021] Example 3: This example provides a method for preparing a nonwoven fabric based on antibacterial polylactic acid, including the following steps: Step 1: Preparation of antibacterial polylactic acid: S1. Montmorillonite (particle size: 50nm) was dispersed in deionized water at a mass-to-volume ratio of 1.5g / 100mL. The mixture was mechanically stirred under ultrasonic (300W) assistance to form a uniform suspension. Under continuous stirring and in the dark, 0.1mol / L silver nitrate solution was added dropwise to the suspension. The pH of the reaction system was maintained at 5.5 during the addition. After the addition was completed, the reaction system was heated to 60℃ and stirred continuously at this temperature for 6 hours. After the reaction was completed, the mixture was vacuum filtered. The obtained solid was repeatedly washed with deionized water until no white precipitate was formed when the filtrate was tested with sodium chloride solution. The washed solid was dried in a vacuum oven at 60℃ to constant weight, ground, and passed through a 600-mesh sieve to obtain silver ion-loaded modified montmorillonite, i.e., the second antibacterial component. X-ray fluorescence spectroscopy analysis showed that the silver ion loading was 2.5% of the carrier mass. S2. Weigh the raw materials according to the following parts by weight: 5 parts of the second antibacterial component obtained in step S1, 2.5 parts of the first antibacterial component chitosan quaternary ammonium salt (degree of deacetylation 92%, degree of substitution 90%, number average molecular weight 20000), 4 parts of polyadipic acid (number average molecular weight 3000), and 1.6 parts of epoxidized linseed oil (epoxy value 5.5) (accounting for 50% of the total mass of bio-based chain extender); All the above materials are put into a high-speed mixer. Under nitrogen atmosphere protection, the mixing temperature is set to 60°C and the mixture is mixed at 600 rpm for 35 minutes to obtain the premix. S3. Prepare other components according to the following weight parts: 85 parts of polylactic acid (weight average molecular weight 120,000, melt flow rate 20g / 10min (190℃, 2.16kg), optical purity 98%), 1.6 parts of epoxidized linseed oil (same specifications as S2, accounting for 50% of the total mass of bio-based chain extender), 11 parts of polyhydroxyalkanoate (melting point 85℃, melt flow rate 55g / 10min (190℃, 2.16kg)), and 1 part of calcium magnesium phytate (average particle size 2μm). The premixed material and all the above components were fed into the main feed port of a twin-screw extruder. The temperature range from the feed port to the die head of the extruder was set as follows: 180℃, 185℃, 188℃, 192℃, 195℃, 198℃, 195℃, 190℃. The screw speed was set to 250 rpm. The average residence time of the material was about 3 minutes. After the melt was extruded through the die head, it was cooled in a water bath, granulated by a pelletizer, and vacuum dried at 80℃ for 10 hours to obtain the antibacterial polylactic acid granules. Step 2: Preparation of nonwoven fabric based on antibacterial polylactic acid: Step (1), spinning: The above antibacterial polylactic acid granules are placed in a vacuum drying oven and dried at 80℃ and -0.8MPa for 12 hours to make the moisture content less than 200ppm. The dried granules are then fed into a melt spinning machine for melt spinning. The temperature of the spinning box is set to 200℃. The melt is extruded through a spinneret (0.20mm orifice) and cooled and shaped by side blowing (0.5m / s wind speed, 20℃). The winding speed is 1650m / min to obtain nascent fibers. The nascent fibers are stretched at 85℃ with a stretch ratio of 3 times, and then heat-set at 95℃ to obtain polylactic acid fibers with a single filament fineness of 2.2dtex. Step (2), Web laying: The antibacterial polylactic acid fiber obtained by spinning is opened and combed by a mechanical carding machine, and then the fiber layer is folded and laid back and forth by a cross-laying machine to form a uniform fiber web with a basis weight of 40g / m². Step (3), hydroentangling reinforcement: The laid fiber web is sent into the hydroentangling reinforcement equipment, using 3 hydroentangling heads, and the hydroentangling pressure is set to 105 bar to perform front hydroentangling reinforcement on the fiber web. The hydroentangled nonwoven fabric is sent into a hot air circulating oven and dried at 80°C until the moisture content is less than 5%, thus obtaining the nonwoven fabric based on antibacterial polylactic acid.

[0022] Comparative Example 1 Compared with Example 3, the only difference in the preparation of antibacterial polylactic acid in Comparative Example 1 is that polydicarboxylic acid is not added.

[0023] Comparative Example 2 Compared with Example 3, the only difference in the preparation of antibacterial polylactic acid in Comparative Example 2 is that chitosan quaternary ammonium salt is not added.

[0024] Comparative Example 3 Compared with Example 3, the only difference in the preparation of antibacterial polylactic acid in Comparative Example 3 is that no supported nano-inorganic antibacterial material is added.

[0025] Comparative Example 4 Compared with Example 3, Comparative Example 4 differed only in that it did not add polydicarboxylic acid and chitosan quaternary ammonium salt when preparing antibacterial polylactic acid.

[0026] Comparative Example 5 Compared with Example 3, Comparative Example 5 differed only in that it did not add polydicarboxylic acid and supported nano-inorganic antibacterial materials when preparing antibacterial polylactic acid.

[0027] Performance testing: The nonwoven fabrics obtained in Examples 1-3 and Comparative Examples 1-5 were subjected to performance tests. The dry and wet strength of the nonwoven fabrics were determined according to standard GB / T24218.3-2010, the softness was determined according to standard GB / T8942-2016, and the antibacterial properties were determined according to standard GB / T20944.3-2008. The test results are shown in Table 1. Table 1

[0028] As shown in Table 1, the nonwoven fabric based on antibacterial polylactic acid prepared by the present invention exhibits excellent performance in dry / wet mechanical strength, softness, and initial and lasting antibacterial properties. Compared to Example 3, in Comparative Example 1, the dry strength, wet strength, softness, initial antibacterial rate, and antibacterial rate after 20 washes of the nonwoven fabric all decreased, indicating that polydicarboxylic acid plays an important role in the system: the carboxyl groups at the ends of the polydicarboxylic acid molecular chains undergo esterification with the hydroxyl groups at the ends of the polylactic acid molecular chains, and simultaneously undergo ring-opening reactions with the epoxy groups of the bio-based chain extender, forming chain extender or micro-crosslinked structures, increasing the entanglement density between molecular chains and stress transfer efficiency. When polydicarboxylic acid is absent, the intermolecular interaction weakens, leading to a decrease in dry strength; polydicarboxylic acid significantly improves the hydrolysis resistance of the material by blocking the hydrophilic terminal hydroxyl groups of the polylactic acid molecular chains and inhibiting water molecule penetration through the formed network structure. When polydicarboxylic acid is absent, water molecules can more easily penetrate between molecular chains, accelerating ester bond hydrolysis and significantly reducing wet strength; the flexible structure of the polydicarboxylic acid molecular chains plays a crucial role in the hydrolysis of polylactic acid. The rigid chain segments of the acid act as a toughening agent, reducing bending stiffness. When polydicarboxylic acid is missing, polylactic acid exhibits a purely rigid chain structure, resulting in more pronounced stress concentration during bending deformation and a harder feel. Polydicarboxylic acid anchors antibacterial components to the matrix network through chemical bonds, resulting in good compatibility between the antibacterial components and the matrix, and endowing it with long-lasting antibacterial properties. When polydicarboxylic acid is missing, the antibacterial components are easily migrated and lost, significantly reducing antibacterial durability. In Comparative Example 2, the absence of chitosan quaternary ammonium salt reduced the antibacterial properties of the nonwoven fabric. In Comparative Example 3, the absence of loaded nano-inorganic antibacterial materials reduced the antibacterial properties of the nonwoven fabric. In Comparative Example 4, the absence of both polydicarboxylic acid and chitosan quaternary ammonium salt reduced the mechanical properties, softness, and antibacterial properties of the nonwoven fabric. In Comparative Example 5, the absence of both polydicarboxylic acid and loaded nano-inorganic antibacterial materials reduced the mechanical properties, softness, and antibacterial properties of the nonwoven fabric.

[0029] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An antibacterial polylactic acid, characterized in that, It is prepared by weight of the following components: 65-92 parts of polylactic acid matrix resin, 3-10 parts of antibacterial agent composition, 0.5-5 parts of bio-based chain extender, 3-15 parts of bio-based toughening agent, 0.5-8 parts of polydicarboxylic acid, and 0.1-2 parts of bio-based nucleating agent. The antibacterial composition comprises a first antibacterial component and a second antibacterial component; The mass ratio of the first antibacterial component to the second antibacterial component is 1:(0.5-3); The first antibacterial component is chitosan quaternary ammonium salt; The second antibacterial component is a supported nano-inorganic antibacterial material.

2. A method for preparing antibacterial polylactic acid as described in claim 1, characterized in that, Includes the following steps: S1. The carrier material is dispersed in deionized water to form a suspension. A soluble salt solution containing inorganic antibacterial metal ions is added dropwise to the suspension. After the addition is complete, the reaction is carried out. After the reaction is completed, the material is separated, washed, and dried to obtain the supported nano-inorganic antibacterial material, i.e., the second antibacterial component. S2. The second antibacterial component obtained in step S1, the first antibacterial component, the polydicarboxylic acid, and the first part of the bio-based chain extender are premixed to obtain a premix. S3. The premix, the polylactic acid matrix resin, the second part of the bio-based chain extender, the bio-based toughening agent and the bio-based nucleating agent are melt-blended, extruded, cooled and pelletized to obtain the antibacterial polylactic acid.

3. The method for preparing antibacterial polylactic acid according to claim 2, characterized in that, The polylactic acid matrix resin is L-polylactic acid; The L-polylactic acid has a weight-average molecular weight of 80,000-150,000 and a melt flow rate of 10-35 g / 10 min at 190°C and 2.16 kg load.

4. The method for preparing antibacterial polylactic acid according to claim 2, characterized in that, The bio-based chain extender is selected from at least one of multifunctional epoxy chain extenders and isocyanate chain extenders; The multifunctional epoxy chain extender includes epoxidized vegetable oil with an epoxy value between 3 and 8; The isocyanate chain extenders include bio-based diisocyanates.

5. The method for preparing antibacterial polylactic acid according to claim 2, characterized in that, The bio-based toughening agent is selected from at least one of polybutylene adipate-terephthalate, polylactic acid-polycaprolactone block copolymer, polyhydroxy fatty acid ester, and acetylated tributyl citrate. The bio-based toughening agent has a melting point of 50-120℃ and a melt flow rate of 10-100g / 10min at 190℃ and 2.16kg load. The polydicarboxylic acid includes at least one of polysuccinic acid and polyadipic acid; The bio-based nucleating agent is selected from at least one of microcrystalline cellulose, chitin whiskers, phytate or caseinate. The average particle size of the bio-based nucleating agent is 0.5-20 μm.

6. The method for preparing antibacterial polylactic acid according to claim 2, characterized in that, In S1, the carrier material includes at least one of halloysite nanotubes, montmorillonite, or hydrotalcite; the inorganic antibacterial metal ions are selected from at least one of silver ions, zinc ions, and copper ions. The reaction conditions are stirring at 50-70℃ for 4-8 hours.

7. The method for preparing antibacterial polylactic acid according to claim 2, characterized in that, In S2, the first part of the bio-based chain extender accounts for 30%-70% of the total mass of the bio-based chain extender; the premixing temperature is 40-80℃, and the premixing time is 10-60min.

8. The method for preparing antibacterial polylactic acid according to claim 2, characterized in that, In S3, during melt blending, the processing temperature range is 180-200℃, and the screw speed is 100-400rpm.

9. A nonwoven fabric based on antibacterial polylactic acid, characterized in that, The nonwoven fabric is prepared from the antibacterial polylactic acid as described in claim 1 through spinning, web laying, and hydroentangling reinforcement, specifically including: Step (1), spinning: After drying the antibacterial polylactic acid, polylactic acid fiber is obtained by melt spinning, winding, stretching and heat setting processes; Step (2), Web laying: Lay polylactic acid fibers into a web; Step (3), hydroentanglement reinforcement: The fiber web is subjected to hydroentanglement reinforcement treatment and dried to obtain a nonwoven fabric based on antibacterial polylactic acid; In step (1), the spinning temperature is 190-210℃, the winding speed is 800-2800m / min, the drawing temperature is 75-95℃, the drawing ratio is 2-4 times, the heat setting temperature is 85-105℃, and the fineness of the resulting polylactic acid fiber monofilament is 1-3.5dtex; in step (2), the web is laid in a cross-laying manner, and the weight of the web is 30-50g / m². 2 In step (3), the hydroentangling pressure is 60-150 bar.

10. The application of the antibacterial polylactic acid-based nonwoven fabric as described in claim 9 in pet wipes.

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