Preparation method of strong hydrophilic-high toughness-heat-resistant polylactic acid fiber

Abstract

The application relates to the technical field of textile fibers, in particular to a preparation method of strong-hydrophilic-high-toughness-heat-resistant polylactic acid fiber, which comprises the following steps: S1, performing ether modification and silane modification treatment on nano-TiO2 respectively, mixing the two, and grinding to prepare composite modified TiO2; S2, taking polylactic acid masterbatch and the composite modified TiO2 prepared in S1, grinding, drying, and fully mixing and uniformly mixing, then adding into a screw extruder to heat melt extrusion, then fully grinding and drying, adding into a double-screw extruder to heat melt extrusion, spinning and drawing, and finally preparing the TiO2 composite modified strong-hydrophilic-high-toughness-heat-resistant polylactic acid fiber. The application improves the dispersibility of nano-TiO2 in polylactic acid, obviously improves the heat degradation resistance of the polylactic acid fiber, and compared with the addition of single silane modified nano-TiO2, further improves the heat degradation resistance, hydrophilicity and toughness of the polylactic acid fiber, and enhances the use effect of the polylactic acid fiber as a clothing fiber.

Description

Technical Field

[0001] This invention relates to the field of textile fiber technology, specifically to a highly hydrophilic, high-strength, high-toughness, and heat-resistant polylactic acid fiber and its preparation method. Background Technology

[0002] Polylactic acid (PLA) is considered one of the most promising bio-based polymers, belonging to the thermoplastic aliphatic polyester family. It is non-toxic, non-irritating, and a fully biodegradable polymer with good biocompatibility, high mechanical strength, and easy processing. Compared to other chemically synthesized biodegradable polymers, PLA is derived from renewable plant resources, eliminating dependence on petroleum. In recent years, PLA's applications have expanded from its initial biomedical applications such as drug delivery, tissue engineering, and scaffolds to general polymer materials like packaging materials, and are rapidly expanding into engineering plastics for construction and automotive products, showing promising prospects. However, PLA also has several drawbacks, such as poor softness and impact resistance at room temperature, low hydrophilicity of fibers, and easy degradation during processing, which severely limit its widespread application in the textile industry. In addition, the use of polylactic acid (PLA) fibers in clothing fabrics is receiving increasing attention. However, due to its poor hydrophilicity and low toughness, the efforts of scholars are still needed to solve these problems and expand the use and effectiveness of PLA fibers in clothing.

[0003] With the surge in demand for a low-carbon economy, polylactic acid (PLA) fiber, thanks to its sustainable closed-loop "returning from farmland to farmland" model, is gradually replacing petroleum-based synthetic fibers and becoming one of the core materials for the green transformation of industries such as textiles, medical devices, and packaging. Studies have shown that adding nano-auxiliaries can improve the performance of PLA, but the improvement is limited. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned shortcomings and provide a method for preparing highly hydrophilic, high-strength and tough, and heat-resistant polylactic acid (PLA) fiber. This method can significantly improve the hydrophilicity and heat degradation resistance of PLA fiber and enhance its toughness. It has significant commercial value for expanding the use and effectiveness of PLA fiber in clothing applications.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a method for preparing highly hydrophilic, high-strength and tough, heat-resistant polylactic acid fiber, comprising the following steps: S1. Nano TiO2 is subjected to etherification modification and silane modification treatment respectively. The two are then mixed and ground thoroughly to obtain composite modified TiO2. S2. The polylactic acid masterbatch and the composite modified TiO2 obtained in S1 are milled, dried and thoroughly mixed. The mixture is then added to a screw extruder for heating and melting extrusion. After further milling and drying, the mixture is added to a twin-screw extruder for heating, melting, extrusion, spinning and stretching to obtain TiO2 composite modified strong hydrophilic, high strength and toughness, and heat-resistant polylactic acid fiber.

[0006] Furthermore, in S1, the specific steps for etherification modification of nano-TiO2 are as follows: solid chloroacetic acid, sodium hydroxide and nano-TiO2 are mixed, thoroughly ground, placed in an oven for reaction, dried and taken out, thoroughly washed with distilled water and centrifuged, the washing-centrifugation is repeated three times, the precipitate is dried and ground to obtain carboxymethyl modified nano-TiO2.

[0007] Furthermore, the molar ratio of chloroacetic acid to sodium hydroxide is 2:1.

[0008] Furthermore, during the reaction in the oven, the product is taken out and stirred evenly every 30 minutes before being put back into the oven.

[0009] Furthermore, in S1, the specific steps for silane modification of nano-TiO2 are as follows: nano-TiO2 is added to a container of anhydrous ethanol and distilled water, and N-aminoethyl-γ-aminopropyltriethoxysilane is added to the container. Then, the container is placed in a constant temperature water bath and stirred. After cooling, the mixture obtained from the reaction is centrifuged, and the precipitate is washed with anhydrous ethanol and filtered. The obtained precipitate is dried and then ground to obtain silane-modified nano-TiO2.

[0010] Furthermore, the mass ratio of the etherified modified nano-TiO2 and the silane modified nano-TiO2 is 0.5-1.5:1.

[0011] Furthermore, the mass of the composite modified TiO2 is 1.5%-2.5% of the mass of the polylactic acid masterbatch.

[0012] Furthermore, the heating and melting temperature is 180-220℃, the spinning speed is 10-60m / min, and the screw speed is 15-150r / min.

[0013] Furthermore, the temperature during the drawing process is 80-120℃, the drawing ratio is 1-4 times, and the drawing speed is 100-260cm / min.

[0014] Compared with the prior art, the present invention has the following beneficial effects: This invention is based on the principle that the hydrophilic hydroxyl groups on the surface of nano-TiO2 can undergo chemical reactions. By forming chemical bonds, carboxymethyl and N-aminoethyl-γ-aminopropyltriethoxysilane substituents with polar functional groups are introduced to regulate the molecular structure of nano-TiO2. TiO2 composite modified polylactic acid (PLA) fibers were prepared by mixing with PLA masterbatch. This process utilized the synergistic effect between functional groups, the filling effect of the composite modified nano-TiO2, the hydrophilicity of polar functional groups, the formation of hydrogen bonds and van der Waals forces between functional groups and PLA molecules, and the high bond energy of titanium-oxygen and silicon-oxygen bonds. Furthermore, the synergistic effect of substituents and steric hindrance reduced the aggregation problem of nano-TiO2 and improved its dispersibility in PLA. This significantly enhanced the heat degradation resistance of PLA fibers. Compared with the addition of single silane-modified nano-TiO2, this further improved the heat degradation resistance, hydrophilicity, and toughness of PLA fibers, enhancing their suitability as clothing 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 images show scanning electron microscope (SEM) images of the modified polylactic acid (PLA) fiber and the original PLA fiber prepared according to this invention.

[0016] Figure 2 Thermogravimetric analysis (TGA) diagrams are shown for the modified polylactic acid (PLA) fiber, the original PLA fiber, and the PLA fiber with single silane-modified nano-TiO2 prepared according to this invention.

[0017] Figure 3 The fracture strength diagrams are of the modified polylactic acid fiber prepared in this invention and the polylactic acid fiber modified with single silane nano-TiO2.

[0018] Figure 4 The diagram shows the elongation at break of the modified polylactic acid fiber prepared in this invention and the polylactic acid fiber modified with single silane nano-TiO2.

[0019] Figure 5 The contact angle diagrams are for the modified polylactic acid fiber, the original polylactic acid fiber, and the polylactic acid fiber with single silane modified nano-TiO2 prepared according to the present invention.

[0020] In the figure: I, II, and III refer to the modified polylactic acid fibers prepared in Examples 1-3, respectively; the comparison refers to the polylactic acid fibers with single silane modified nano-TiO2 prepared in Comparative Example 2. Detailed Implementation

[0021] 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.

[0022] Please see Figure 1-5 .

[0023] Example 1: The present invention discloses a method for preparing highly hydrophilic, high-strength, and heat-resistant polylactic acid fibers, comprising the following steps: S1. The nano-TiO2 was subjected to etherification modification and silane modification treatment respectively. The two were mixed and ground thoroughly to obtain composite modified TiO2. The mass ratio of the etherified nano-TiO2 and the silane-modified nano-TiO2 was 0.5:1. The specific steps for etherification modification of nano-TiO2 are as follows: 45g of solid chloroacetic acid, sodium hydroxide and 60g of nano-TiO2 are mixed, the molar ratio of chloroacetic acid to sodium hydroxide is 2:1, and after thorough grinding for 30min, the mixture is placed in an oven at 66℃ for 3.5h. Every 30min, the mixture is taken out, stirred evenly and placed back into the oven. After drying, it is taken out and washed thoroughly with distilled water and centrifuged at 4000r / min for 10min. The washing-centrifugation process is repeated three times. The precipitate is placed in an oven at 40℃ for 10h and then ground to obtain carboxymethyl modified nano-TiO2. The specific steps for silane modification of nano-TiO2 are as follows: 20g of nano-TiO2 is added to a container containing 300mL of anhydrous ethanol and 300mL of distilled water, and 0.844g of N-aminoethyl-γ-aminopropyltriethoxysilane is added to the container. Then, the mixture is placed in a 70℃ constant temperature water bath and stirred for 4h. After cooling to room temperature, the mixture is centrifuged for 30min at a speed of 4000r / min. The precipitate is washed with anhydrous ethanol and filtered. The centrifugation and washing operations are repeated 3 times. The precipitate is dried at 35℃ and then ground to obtain silane-modified nano-TiO2. S2. The polylactic acid masterbatch and the composite modified TiO2 obtained in S1 are milled and dried in a vacuum drying oven at 50℃ for 12 hours. The mass of the composite modified TiO2 is 1.5% of the mass of the polylactic acid masterbatch. After being fully mixed, the mixture is added to a screw extruder and heated to 190℃ for melt extrusion. After being fully milled and dried, the mixture is added to a twin-screw extruder with a screw speed of 35 r / min. After being heated, melt-extruded, spun, and drawn, TiO2 composite modified strong hydrophilic-high strength and toughness-heat resistant polylactic acid fiber sample I is obtained. The melt spinning temperature is 190℃, the spinning speed is 40 m / min, the drawing temperature is 100℃, the drawing ratio is 2 times, and the drawing speed is 200 cm / min. Example 2: The difference between this embodiment and Embodiment 1 is that in S1, the mass ratio of carboxymethyl modified nano-TiO2 to silane modified nano-TiO2 is 1:1. In step S2, the mass of the composite modified TiO2 is 2.0% of the mass of the polylactic acid masterbatch, the melt spinning temperature is 195℃, and the spinning speed is 45m / min. The drawing temperature is 105℃, the drawing ratio is 2, and the drawing speed is 200cm / min, thus obtaining TiO2 composite modified strong hydrophilic, high strength and toughness, and heat-resistant polylactic acid fiber sample II.

[0024] Example 3: The difference between this embodiment and Embodiment 1 is that, in S1, the mass ratio of carboxymethyl modified nano-TiO2 to silane modified nano-TiO2 is 1.5:1; In step S2, the mass of the composite modified TiO2 is 2.5% of the mass of the polylactic acid masterbatch, the melt spinning temperature is 195℃, and the spinning speed is 45m / min. The drawing temperature is 105℃, the drawing ratio is 2, and the drawing speed is 200cm / min, thus obtaining TiO2 composite modified strong hydrophilic, high strength and toughness, and heat-resistant polylactic acid fiber sample III.

[0025] Comparative Example 1: This comparative example provides a method for preparing polylactic acid fibers in the prior art, the steps of which are as follows: The original polylactic acid masterbatch was thoroughly pulverized using an ultrafine grinder, dried in a vacuum drying oven at 50℃ for 12 hours, and then fed into a twin-screw extruder. The screw speed was controlled at 40 r / min, and the mixture was heated, melt-spun, and spun to obtain original polylactic acid fibers. The melt spinning temperature was 190℃, and the spinning speed was 40 m / min. The drawing temperature was 100℃, the drawing ratio was 2, and the drawing speed was 200 cm / min.

[0026] Comparative Example 2: This comparative example provides a method for preparing polylactic acid fibers with single silane-modified nano-TiO2, the steps of which are as follows: After silane-modified nano-TiO2 and polylactic acid masterbatch were thoroughly pulverized using an ultrafine grinder, they were dried in a vacuum drying oven at 50℃ for 12 hours. Then, they were fed into a twin-screw extruder, and the screw speed was controlled at 40 r / min. The mixture was heated and melt-extruded to obtain silane-modified polylactic acid fiber. The melt spinning temperature was 190℃, the spinning speed was 40 m / min, the drawing temperature was 100℃, the drawing ratio was 2, and the drawing speed was 200 cm / min.

[0027] In conjunction with the examples and comparative examples 1-2, after sputtering gold onto fiber samples under vacuum conditions, the surface morphology of the fibers was observed and analyzed using a Quantum SEM 3200. The results are as follows. Figure 1 As shown, by Figure 1 It can be seen that the surfaces of the original polylactic acid fiber prepared in Comparative Example 1 and the modified polylactic acid fiber prepared in this application are basically smooth and flat, with no obvious difference, indicating that the addition of the composite modified nano-auxiliary agent did not have a significant impact on the surface of the spun fiber.

[0028] Thermogravimetric analysis (TGA) was used to systematically study the mass variation of polylactic acid (PLA) fiber samples with temperature, revealing the thermal stability of the samples. The results are shown in [Figure number missing]. Figure 2 The initial decomposition temperature of the original polylactic acid fiber in Comparative Example 1 was approximately 335°C, and the thermal degradation temperature range was 335-400°C. The initial decomposition temperature of the polylactic acid fiber with TiO2 modified by adding a single silane in Comparative Example 2 was approximately 345°C, and the thermal degradation temperature range was 345-400°C. The modified polylactic acid fiber prepared in Example 1 of this application had an increased initial decomposition temperature of approximately 345°C, and a rapid thermal degradation temperature range of 360-425°C. These results indicate that the addition of composite modified nano-TiO2, compared to the addition of single silane modified nano-TiO2, further enhances the heat resistance of polylactic acid (PLA) fibers. TiO2 and silane have the effect of delaying heat conduction and volatilization diffusion, and the high bond energy of titanium oxide bonds and silicon oxide bonds, as well as the synergistic effect of silane and carboxymethyl groups, increase the temperature at which PLA fibers undergo rapid thermal degradation, allowing them to be melt-processed at higher temperatures. This improves thermal degradation stability and avoids the impact of the spinning process on the PLA molecular chain, reducing the risk of thermal degradation.

[0029] The tensile strength and elongation at break of the fibers were tested using a tensile testing instrument. The effective test length was 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 test results are shown in […]. Figure 3 and 4The modified polylactic acid fiber sample I prepared in Example 1 of this application has the highest average breaking strength (281 cN), which is significantly higher than that of the polylactic acid fiber prepared with single silane modified nano-TiO2 prepared in Comparative Example 2 (comparison, 190 cN). It also has the highest average elongation at break (3.97%), which is significantly higher than that of the polylactic acid fiber prepared with single silane modified nano-TiO2 (comparison, 3.42%). The breaking strength and elongation at break are increased by 47.9% and 16.1% respectively compared with the polylactic acid fiber prepared with single silane modified nano-TiO2. Since the elongation at break of the modified polylactic acid fiber sample I is significantly better than that of the polylactic acid fiber prepared with single silane modified nano-TiO2, it can be concluded that the addition of composite modified nano-TiO2 further significantly improves the strength and toughness of polylactic acid fiber. Among the three modified polylactic acid samples used to improve the performance of polylactic acid fiber, sample I is preferred.

[0030] Deionized water was used, and a contact angle meter was employed to test the contact angles of polylactic acid fibers before and after modification to evaluate the change in fiber hydrophilicity. The contact angle test results are shown in the figure. Figure 5 The original polylactic acid (PLA) fiber had a contact angle of 113°, exhibiting obvious hydrophobic properties. This hydrophobic property mainly stems from the large number of hydrophobic ester groups present in the PLA molecular chain. The contact angles of the modified PLA fiber with single silane-modified nano-TiO2 (comparison) and the modified PLA fiber with composite-modified nano-TiO2 decreased to about 73° and 58°, respectively. This indicates that the use of composite-modified nano-TiO2 containing hydrophilic polar functional groups significantly improves the hydrophilicity of PLA fiber compared to PLA fiber with single silane-modified nano-TiO2.

[0031] 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 highly hydrophilic, high-strength, and heat-resistant polylactic acid fiber, characterized in that, Includes the following steps: S1. Nano TiO2 is subjected to etherification modification and silane modification treatment respectively. The two are then mixed and ground thoroughly to obtain composite modified TiO2. S2. The polylactic acid masterbatch and the composite modified TiO2 obtained in S1 are milled, dried and thoroughly mixed. The mixture is then added to a screw extruder for heating and melting extrusion. After further milling and drying, the mixture is added to a twin-screw extruder for heating, melting, extrusion, spinning and stretching to obtain TiO2 composite modified strong hydrophilic, high strength and toughness, and heat-resistant polylactic acid fiber.

2. The method for preparing highly hydrophilic, high-strength, tough, and heat-resistant polylactic acid fiber according to claim 1, characterized in that, In S1, the specific steps for etherification modification of nano-TiO2 are as follows: solid chloroacetic acid, sodium hydroxide and nano-TiO2 are mixed, ground thoroughly, placed in an oven for reaction, dried and taken out, washed thoroughly with distilled water and centrifuged. After repeating the washing-centrifugation three times, the precipitate is dried and ground to obtain carboxymethyl modified nano-TiO2.

3. The method for preparing highly hydrophilic, high-strength, tough, and heat-resistant polylactic acid fiber according to claim 2, characterized in that, The molar ratio of chloroacetic acid to sodium hydroxide is 2:

1.

4. The method for preparing highly hydrophilic, high-strength, and heat-resistant polylactic acid fiber according to claim 2, characterized in that, During the reaction in the oven, the product is taken out and stirred evenly every 30 minutes before being put back into the oven.

5. The method for preparing highly hydrophilic, high-strength, and heat-resistant polylactic acid fiber according to claim 1, characterized in that, In S1, the specific steps for silane modification of nano-TiO2 are as follows: nano-TiO2 is added to a container of anhydrous ethanol and distilled water, and N-aminoethyl-γ-aminopropyltriethoxysilane is added to the container. Then, the container is placed in a constant temperature water bath and stirred. After cooling, the mixture obtained from the reaction is centrifuged, and the precipitate is washed with anhydrous ethanol and filtered. The precipitate is dried and then ground to obtain silane-modified nano-TiO2.

6. The method for preparing highly hydrophilic, high-strength, tough, and heat-resistant polylactic acid fiber according to claim 1, characterized in that, The mass ratio of etherified nano-TiO2 and silane-modified nano-TiO2 is 0.5-1.5:

1.

7. The method for preparing highly hydrophilic, high-strength, tough, and heat-resistant polylactic acid fiber according to claim 1, characterized in that, The mass of the composite modified TiO2 is 1.5%-2.5% of the mass of the polylactic acid masterbatch.

8. The method for preparing highly hydrophilic, high-strength, and heat-resistant polylactic acid fiber according to claim 1, characterized in that, The heating and melting temperature is 180-220℃, the spinning speed is 10-60m / min, and the screw speed is 15-150r / min.

9. The method for preparing highly hydrophilic, high-strength, tough, and heat-resistant polylactic acid fiber according to claim 1, characterized in that, The temperature during the stretching process is 80-120℃, the stretching ratio is 1-4 times, and the stretching speed is 100-260cm / min.

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