A method for preparing modified TiO2 composite cationic polylactic acid fiber and its application

Abstract

This invention relates to the field of textile bio-based fiber technology, specifically including a method for preparing modified TiO2 composite cationic polylactic acid (PLA) fiber, comprising the following steps: S1, preparation of modified TiO2 sample; S2, preparation of cationic modified PLA sample; S3, preparation of modified TiO2 composite cationic PLA fiber. This invention modifies PLA masterbatch with quaternary ammonium cations, firmly introducing hydrophilic and positively charged cations into the PLA molecular chain, endowing it with durable antibacterial properties and durable hydrophilicity. Further, by etherifying TiO2 followed by sulfonation, the hydrophilicity of the PLA fiber is significantly enhanced. Since water can conduct charge, the PLA fiber with positively charged cations exhibits strong antistatic properties.

Description

Technical Field

[0001] This invention relates to the field of textile bio-based fiber technology, specifically to a method for preparing modified TiO2 composite cationic polylactic acid fiber and its application. Background Technology

[0002] Polylactic acid (PLA) is considered one of the most promising bio-based polymer materials. In recent years, PLA applications have expanded from biomedical fields such as drug delivery, tissue engineering, and scaffolds to general polymer materials like packaging materials. Furthermore, its application in textiles and other fields is rapidly expanding through spinning into fibers, showing promising prospects. However, PLA fibers still have some drawbacks in practical applications, such as: relatively low single-fiber strength; strong hydrophobicity making it less effective than traditional hydrophilic fibers in terms of moisture absorption, wicking, and wearing comfort, and also causing serious static electricity problems; and insufficient antibacterial properties. These factors significantly affect its performance as a clothing fiber.

[0003] With increasing public awareness of health and environmental protection, the development of polylactic acid (PLA) fibers with durable hydrophilicity, high strength, antistatic properties, and antibacterial properties has become a major research focus. Therefore, this research addresses the existing problems in PLA fiber development. Conventionally, nano-auxiliaries (such as nano-TiO2) are blended with PLA to reduce its hydrophobicity and improve its strength to some extent. However, due to the hydrophilicity of nano-TiO2 and its tendency to agglomerate when used in large quantities, coupled with the strong hydrophobicity of PLA, its dispersibility in PLA is poor, resulting in limited improvement on PLA performance. Furthermore, during later use, the lack of significant molecular bonding between the auxiliaries and PLA molecular chains leads to the precipitation and loss of the auxiliaries, resulting in the short-lived improvement in the hydrophilicity and reinforcement properties of PLA fibers. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned shortcomings and provide a method for preparing modified TiO2 composite cationic polylactic acid fiber and its application. By adsorbing modified TiO2 particles onto the quaternary ammonium cationic groups on polylactic acid, poor dispersibility is avoided, and polylactic acid fiber is endowed with long-lasting antibacterial, hydrophilic and antistatic properties, which significantly enhances the use effect and value of polylactic acid fiber as clothing fiber.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a method for preparing modified TiO2 composite cationic polylactic acid fiber, comprising the following steps: S1. Preparation of modified TiO2 samples: Nano-TiO2 was mixed with an ethanol-distilled aqueous solution to form dispersion one, which was then subjected to an etherification modification reaction. After the reaction, dispersion two was prepared and subjected to a sulfonation modification reaction. After centrifugation, washing, drying, and pulverization, the modified TiO2 sample was obtained. S2. Preparation of cationic modified polylactic acid samples: Polylactic acid masterbatch was dissolved in an organic solvent and subjected to a quaternary ammonium cation modification reaction. After washing and filtration, the sample was dried and pulverized to obtain a cation-modified polylactic acid sample. S3. Preparation of modified TiO2 composite cationic polylactic acid fibers: The modified TiO2 sample and the cationic modified polylactic acid sample were thoroughly ground and mixed evenly. The mixture was then extruded in a screw extruder, melt-spun, cured, and wound to obtain modified TiO2 composite cationic polylactic acid fiber.

[0006] Furthermore, in S1, the etherification modification reaction specifically includes: adjusting the pH value of dispersion one using NaOH aqueous solution, then adding glycidyl methacrylate dropwise, and continuously stirring while reacting in a water bath.

[0007] Furthermore, in S1, the sulfonation modification reaction specifically includes: adding sodium bisulfite to dispersion II and carrying out the reaction in a water bath.

[0008] Furthermore, in S2, the quaternary ammonium cation modification reaction specifically includes: dissolving polylactic acid in an organic solvent, preparing a solution, adjusting the pH value with NaOH aqueous solution, then adding 2,3-epoxypropyltrimethylammonium chloride, and continuing the reaction.

[0009] Furthermore, the organic solvent is dichloromethane, chloroform, acetone, dichloromethane, ethyl acetate, or dimethylformamide.

[0010] Furthermore, the mass ratio of 2,3-epoxypropyltrimethylammonium chloride to polylactic acid is 1-3:20.

[0011] Furthermore, in S3, the mass of the modified TiO2 sample is 0.5%-3% of the mass of the cationic modified polylactic acid sample.

[0012] Furthermore, in S3, the melt spinning temperature is 180-230℃ and the winding speed is 15-50m / min.

[0013] An application of a modified TiO2 composite cationic polylactic acid fiber, wherein the modified TiO2 composite cationic polylactic acid fiber is used as a fiber for clothing.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention modifies polylactic acid masterbatch with quaternary ammonium cations, thereby firmly introducing hydrophilic and positively charged cations into the polylactic acid molecular chain, endowing it with long-lasting antibacterial properties and polylactic acid fibers with long-lasting hydrophilicity. 2. This invention significantly improves the hydrophilicity of polylactic acid fibers by etherifying TiO2 followed by sulfonation. Water can conduct charge, so polylactic acid fibers with positively charged cations have strong antistatic properties. 3. In this invention, the anionic sulfonic acid functional groups on the etherified-sulfonated modified TiO2 and the cationic functional groups on polylactic acid generate electrostatic attraction, adsorbing the etherified-sulfonated modified TiO2 onto the cationic groups on the polylactic acid molecular chain, thereby improving the dispersibility of TiO2 in polylactic acid and thus better enhancing the strength of polylactic acid fibers. Attached Figure Description

[0015] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 The reaction equation diagram shows the etherification-sulfonation modification of TiO2 and the quaternary ammonium cation modification of polylactic acid in this invention. Figure 2 This is a scanning electron microscope image of the modified TiO2 composite cationic polylactic acid fiber prepared in this invention; Figure 3 Water contact angle diagrams of the modified TiO2 composite cationic polylactic acid fiber, the original polylactic acid fiber, and the TiO2 composite polylactic acid fiber prepared in this invention; Figure 4 The tensile strength diagrams are for the modified TiO2 composite cationic polylactic acid fiber, the original polylactic acid fiber, and the TiO2 composite polylactic acid fiber prepared in this invention. Figure 5 The images show the modified TiO2 composite cationic polylactic acid fiber, the original polylactic acid fiber, the TiO2 composite polylactic acid fiber, and the colony diagram of the original bacteria prepared in this invention. Detailed Implementation

[0016] 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 a part of the embodiments of the present invention, and not all of the embodiments. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] Please see Figure 1-5 .

[0018] Example 1: The preparation method of the modified TiO2 composite cationic polylactic acid fiber of the present invention includes the following steps: S1. Preparation of modified TiO2 samples: 40g of dry nano-TiO2 was weighed and added to an ethanol-distilled water solution with a volume ratio of 60:40 to prepare a dispersion with a mass ratio of 4%. The pH of dispersion one was adjusted to 9 with a 2% NaOH aqueous solution. 20g of glycidyl methacrylate was slowly added dropwise, and the mixture was stirred and heated to 85℃ in a water bath for 100min. After washing four times with anhydrous ethanol by centrifugation, the mixture was redispersed with ethanol-distilled water to prepare a dispersion with a mass ratio of 4%. 40g of sodium bisulfite was added, and the mixture was reacted in a 50℃ water bath for 3h. After washing three times with distilled water by centrifugation, the mixture was dried and pulverized in a 50℃ oven to obtain an etherified-sulfonated modified TiO2 sample. The percentage of etherified-sulfonated groups in the sample was 8.79%. S2. Preparation of cationic modified polylactic acid samples: 100g of polylactic acid masterbatch was dissolved in dichloromethane to prepare a 30% (w / v) solution, which was then transferred to a three-necked flask. The pH was adjusted to 9 using a 2% (w / v) NaOH aqueous solution. The mixture was stirred and heated to 40°C and kept at this temperature. Then, 5g of 2,3-epoxypropyltrimethylammonium chloride was added, and the pH was adjusted to 9. The reaction was continued at this temperature for 6 hours. After evaporating the solvent in a fume hood, the remaining solid was washed twice with ethanol-distilled water and filtered. The solid was then dried and pulverized in an oven at 35°C to obtain cationic modified polylactic acid sample 1. The mass percentage of cationic substituents in sample 1 was 0.26%. S3. Preparation of modified TiO2 composite cationic polylactic acid fibers: The etherified-sulfonated modified TiO2 sample and the cationic modified polylactic acid sample 1 were thoroughly ground. The mass of the etherified-sulfonated modified TiO2 sample was 2% of the mass of the cationic modified polylactic acid sample 1. After being mixed evenly, the mixture was added to a screw extruder and extruded at a screw speed of 35 r / min. After melt extrusion and solidification at 190℃, the mixture was crushed and thoroughly ground. After drying in a vacuum drying oven at 55℃ for 12 h, it was added to a twin-screw extruder, heated for melt spinning, solidified, and then wound to obtain modified TiO2 composite cationic polylactic acid fiber I. The spinning temperature was 190℃, the screw speed was 35 r / min, and the spinning winding speed was 40 m / min.

[0019] An application of a modified TiO2 composite cationic polylactic acid fiber, wherein the modified TiO2 composite cationic polylactic acid fiber is used as a fiber for clothing.

[0020] Example 2: The difference between this embodiment and Embodiment 1 is that: In step S2, 10 g of 2,3-epoxypropyltrimethylammonium chloride was added to obtain cationic modified polylactic acid sample 2, in which the percentage of quaternary ammonium cationic groups was 0.85%. In step S3, the etherified-sulfonated modified TiO2 sample and the cationic modified polylactic acid sample 2 are thoroughly ground. The mass of the etherified-sulfonated modified TiO2 sample is 2% of the mass of the cationic modified polylactic acid sample 2. After being mixed evenly, the mixture is added to a screw extruder for extrusion at a screw speed of 45 r / min. After melt extrusion and solidification at 195°C, the mixture is crushed and thoroughly ground. After drying in a vacuum drying oven at 50°C for 12 h, it is added to a twin-screw extruder for heating, melt spinning, solidification, and winding to obtain modified TiO2 composite cationic polylactic acid fiber II. The spinning temperature is 190°C, the screw speed is 45 r / min, and the spinning winding speed is 35 m / min.

[0021] Example 3: The difference between this embodiment and Embodiment 1 is that: In step S2, 15 g of 2,3-epoxypropyltrimethylammonium chloride was added to obtain cationic modified polylactic acid sample 3. The percentage of quaternary ammonium cationic groups in sample 3 was 1.82%. In step S3, the etherified-sulfonated modified TiO2 sample and the cationic modified polylactic acid sample 3 are thoroughly ground. The mass of the etherified-sulfonated modified TiO2 sample is 2% of the mass of the cationic modified polylactic acid sample 3. After being mixed evenly, the mixture is added to a screw extruder for extrusion at a screw speed of 35 r / min. After melt extrusion and solidification at 195°C, the mixture is crushed and thoroughly ground. After drying in a vacuum drying oven at 50°C for 12 h, it is added to a twin-screw extruder for heating, melt spinning, solidification, and winding to obtain modified TiO2 composite cationic polylactic acid fiber III. The spinning temperature is 190°C, the screw speed is 35 r / min, and the spinning winding speed is 40 m / min.

[0022] Comparative Example 1: This comparative example provides a method for preparing virgin polylactic acid fibers, comprising the following steps: After the original polylactic acid masterbatch was fully pulverized by an ultrafine grinder, it was dried in a vacuum drying oven at 50°C for 12 hours. Then, it was added to a twin-screw extruder, heated, melt-extruded, spun, and wound to obtain the original polylactic acid fiber. The melt spinning temperature was 190°C, the screw speed was 35 r / min, and the spinning winding speed was 40 m / min.

[0023] Comparative Example 2: This comparative example provides a method for preparing TiO2 composite polylactic acid fibers, including the following steps: Polylactic acid (PLA) and TiO2 were thoroughly ground using an ultrafine mill, with TiO2 accounting for 2% of the PLA mass. After uniform mixing, the mixture was added to a screw extruder at a screw speed of 35 r / min. After melt extrusion and curing at 195°C, the mixture was pulverized and thoroughly ground using an ultrafine mill. It was then dried in a vacuum drying oven at 50°C for 12 hours before being added to a twin-screw extruder. After heating, melt spinning, curing, and winding, TiO2 composite PLA fibers were obtained. The melt spinning temperature was 190°C, the screw speed was 35 r / min, and the spinning winding speed was 40 m / min.

[0024] Figure 1 The preparation equations for etherified-sulfonated modified TiO2 samples and the reaction equations for polylactic acid quaternary ammonium cationic modification are presented. The glycidyl methacrylate structure is introduced into TiO2 particles by etherification of the epoxy alkyl group on glycidyl methacrylate with the hydroxyl group of TiO2. Then, a sulfonation reaction is carried out with sodium bisulfite to introduce hydrophilic sulfonic acid groups into the unsaturated olefin double bond of the glycidyl methacrylate structure, thus successfully preparing the etherified-sulfonated modified TiO2 sample. The cationic modified polylactic acid sample is obtained by etherification of polylactic acid masterbatch with 2,3-epoxypropyltrimethylammonium chloride in a solution system.

[0025] Figure 2 The image shows the surface morphology of the modified TiO2 composite cationic polylactic acid fiber using a Quantum SEM3200. The fiber surface is generally smooth and has a good morphology. The etherified-sulfonated modified TiO2 containing anionic sulfonate groups can combine with the cations on the cationic modified polylactic acid, thereby reducing the problem of poor dispersion of TiO2 in polylactic acid due to agglomeration and improving the surface morphology of the fiber.

[0026] Figure 3 The images show the water contact angles of the modified TiO2 composite cationic polylactic acid (PLA) fiber, the original PLA fiber, and the TiO2 composite PLA fiber prepared in this invention. The original PLA fiber has a contact angle of 122°, exhibiting strong hydrophobicity; the contact angle of the TiO2 composite PLA fiber is reduced to approximately 75°; and the modified TiO2 composite cationic PLA fiber further reduces the water contact angle to approximately 50°, exhibiting strong hydrophilic properties. These results indicate that the use of modified TiO2 containing hydrophilic polar hydroxyl and sulfonic acid functional groups, along with the hydrophilic cationic modification treatment of PLA, significantly enhances the hydrophilicity of PLA fibers. The firm introduction of hydrophilic cations into PLA prevents loss during washing and other processes after garment fabrication, thus endowing PLA fibers with durable hydrophilic properties. Simultaneously, the hydrophilicity allows for rapid conduction of static charges, reducing static electricity and providing an antistatic effect.

[0027] Figure 4The tensile strength diagrams of the modified TiO2 composite cationic polylactic acid fiber, the original polylactic acid fiber, and the TiO2 composite polylactic acid fiber prepared in this invention were obtained. The tensile strength of the fibers was tested using a tensile testing instrument with an effective test length set to 20 mm. At least 10 single fibers were tested in each sample group. A pretension of 0.05 cN was applied to the fibers. The original polylactic acid fiber sample had the lowest average tensile strength. The TiO2 composite polylactic acid fiber was slightly higher than the original polylactic acid fiber. The average tensile strength of the modified TiO2 composite cationic polylactic acid fiber sample was further increased, reaching 205 cN for sample III, which is 38.5% higher than that of the original polylactic acid fiber, showing a significant improvement.

[0028] Figure 5 To obtain the modified TiO2 composite cationic polylactic acid fiber, the original polylactic acid fiber, the TiO2 composite polylactic acid fiber, and the original bacteria prepared in this invention, the fiber sample was ground into powder. 0.1g of the sample was evenly distributed in 10mL of PBS, and 0.1mL of bacterial suspension was added. After 5 minutes, the bacteria in the sample were dispersed by vortexing for 10s. The bacterial solution was serially diluted 10 times using a conical centrifuge tube and evenly dropped onto the surface of a solid culture dish. After incubation at 37℃ for 24h, the colony count was measured and the antibacterial rate was calculated. The bacterial colonies in all three types of fibers were significantly lower than those in the original polylactic acid (PLA) fibers. The bacterial colonies in the TiO2 composite PLA fiber were slightly lower than those in the original PLA fiber. Calculations showed that the antibacterial rate of the original PLA fiber was 71.0%, the antibacterial rate of the TiO2 composite PLA fiber was 73.8%, and the modified TiO2 composite cationic PLA fiber had almost zero bacterial colonies, achieving an antibacterial rate of over 99.0%. This improved antibacterial performance is mainly attributed to the introduction of cationic quaternary ammonium salt functional groups into the PLA matrix, which inhibit bacterial growth and reproduction, thus exerting a bacteriostatic effect. This results in the superior antibacterial properties of the modified TiO2 composite cationic PLA fiber. By introducing hydrophilic quaternary ammonium cationic groups into PLA, the antibacterial properties are not lost during washing or other processes after the fiber is spun into yarn and made into clothing. This endows PLA fiber with long-lasting antibacterial properties, overcoming the problem of short-lasting antibacterial effects with conventional antibacterial agents. This significantly enhances the effectiveness and value of PLA fiber as a clothing fiber, laying an important foundation for the development of high-performance and long-lasting antibacterial textiles and medical dressings.

[0029] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A method for preparing modified TiO2 composite cationic polylactic acid fiber, characterized in that, Includes the following steps: S1. Preparation of modified TiO2 samples: Nano-TiO2 was mixed with an ethanol-distilled aqueous solution to form dispersion one, which was then subjected to an etherification modification reaction. After the reaction, dispersion two was prepared and subjected to a sulfonation modification reaction. After centrifugation, washing, drying, and pulverization, the modified TiO2 sample was obtained. S2. Preparation of cationic modified polylactic acid samples: Polylactic acid masterbatch was dissolved in an organic solvent and subjected to a quaternary ammonium cation modification reaction. After washing and filtration, the sample was dried and pulverized to obtain a cation-modified polylactic acid sample. S3. Preparation of modified TiO2 composite cationic polylactic acid fibers: The modified TiO2 sample and the cationic modified polylactic acid sample were thoroughly ground and mixed evenly. The mixture was then extruded in a screw extruder, melt-spun, cured, and wound to obtain modified TiO2 composite cationic polylactic acid fiber.

2. The method for preparing modified TiO2 composite cationic polylactic acid fiber according to claim 1, characterized in that, In S1, the etherification modification reaction specifically includes: adjusting the pH value of dispersion one with NaOH aqueous solution, then adding glycidyl methacrylate dropwise, and continuously stirring while reacting in a water bath.

3. The method for preparing modified TiO2 composite cationic polylactic acid fiber according to claim 1, characterized in that, In S1, the sulfonation modification reaction specifically includes: adding sodium bisulfite to dispersion II and carrying out the reaction in a water bath.

4. The method for preparing modified TiO2 composite cationic polylactic acid fiber according to claim 1, characterized in that, In S2, the quaternary ammonium cation modification reaction specifically includes: dissolving polylactic acid in an organic solvent, preparing a solution, adjusting the pH value with NaOH aqueous solution, then adding 2,3-epoxypropyltrimethylammonium chloride, and continuing the reaction.

5. The method for preparing modified TiO2 composite cationic polylactic acid fiber according to claim 4, characterized in that, The organic solvent is dichloromethane, chloroform, acetone, dichloromethane, ethyl acetate, or dimethylformamide.

6. The method for preparing modified TiO2 composite cationic polylactic acid fiber according to claim 4, characterized in that, The mass ratio of 2,3-epoxypropyltrimethylammonium chloride to polylactic acid is 1-3:

20.

7. The method for preparing modified TiO2 composite cationic polylactic acid fiber according to claim 1, characterized in that, In S3, the mass of the modified TiO2 sample is 0.5%-3% of the mass of the cationic modified polylactic acid sample.

8. The method for preparing modified TiO2 composite cationic polylactic acid fiber according to claim 1, characterized in that, In S3, the melt spinning temperature is 180-230℃ and the winding speed is 15-50m / min.

9. An application of a modified TiO2 composite cationic polylactic acid fiber according to any one of claims 1-8, characterized in that, The modified TiO2 composite cationic polylactic acid fiber is used as a fiber for clothing.

Images