Preparation method of quaternized polylactic acid antibacterial elastic composite fiber

Abstract

The invention relates to the technical field of fibers, and discloses a quaternized polylactic acid antibacterial elastic composite fiber preparation method, which comprises: carrying out electrostatic spinning on polylactic acid and maleic anhydride modified polyvinyl alcohol to obtain a polylactic acid composite fiber; and then reacting with glutaraldehyde and amine ethyl imidazole quaternary ammonium salt to obtain the quaternized polylactic acid antibacterial elastic composite fiber. The maleic anhydride modified polyvinyl alcohol contains carboxyl hydrophilic groups and ester groups, so that the hydrophilicity of the composite fiber is improved, the compatibility of polylactic acid and polyvinyl alcohol is improved, the phase separation phenomenon of polylactic acid and polyvinyl alcohol in the spinning process can be avoided, and the elongation at break, toughness and elasticity of the fiber can be improved; the aminoethyl imidazole quaternary ammonium salt is chemically grafted to the surface of the composite fiber, so that the antibacterial rate of the fiber to escherichia coli and staphylococcus aureus is increased, and the fiber shows very strong antibacterial performance.

Description

Technical Field

[0001] The present invention relates to the technical field of fibers, and specifically to a preparation method of quaternized polylactic acid antibacterial elastic composite fibers. Background Art

[0002] Polylactic acid has good biocompatibility, degradability and mechanical strength, and can be made into products such as plastics and fibers, which are widely used in biological tissue engineering, medical supplies, textiles and other aspects. Traditional polylactic acid fibers have problems such as poor hydrophilicity, low elongation at break, poor toughness and elasticity, and poor antibacterial performance, which limit the practical application of polylactic acid fibers.

[0003] Polyvinyl alcohol has good biodegradability, hydrophilicity and spinnability, and has important applications in fiber products. Blending polyvinyl alcohol and polylactic acid for spinning can obtain composite fibers with better hydrophilicity and degradability. Chinese Patent CN112481731B discloses a copper ion antibacterial fiber and antibacterial fabric, which are spun with polylactic acid, hydrophobically modified polyvinyl alcohol, copper-loaded nanoporous phosphorus-containing borosilicate ceramic powder antibacterial agent, etc., and the obtained fibers have good antibacterial and mechanical properties, etc., but this patent does not solve the problem of poor hydrophilicity of polylactic acid fibers. Summary of the Invention

[0004] In view of the deficiencies of the prior art, the present invention provides a preparation method of quaternized polylactic acid antibacterial elastic composite fibers, which solves the problem of poor antibacterial performance of polylactic acid fibers, and at the same time improves the hydrophilicity and resilience of polylactic acid fibers. The specific technical solutions are as follows: The preparation method of quaternized polylactic acid antibacterial elastic composite fibers includes the following steps: (1) Add 100 parts by weight of polylactic acid to dimethyl sulfoxide, heat and stir to dissolve to form a polylactic acid solution; add 60 - 80 parts by weight of maleic anhydride-modified polyvinyl alcohol to dimethyl sulfoxide, heat and stir to dissolve, then add the polylactic acid solution, stir and mix evenly, stand for defoaming, pour the spinning solution into a syringe, and spin and receive through an electrospinning machine to obtain polylactic acid composite fibers; (2) Add 100 parts by weight of polylactic acid composite fibers and an aqueous solution containing 3 - 18 parts by weight of glutaraldehyde to water, dropwise add a hydrochloric acid solution, stir and react, then add 2 - 10 parts by weight of aminoethylimidazole quaternary ammonium salt, stir and react, filter, wash, and dry to obtain quaternized polylactic acid antibacterial elastic composite fibers; wherein, the structural formula of aminoethylimidazole quaternary ammonium salt is ; a is any integer from 12 to 16.

[0005] Further, in the step (1), the voltage during spinning is 10 - 15 kV, and the flow rate of the spinning solution is 0.4 - 0.8 mL / h.

[0006] Further, in step (2), a hydrochloric acid solution is added dropwise to adjust the pH to 5.5 - 6.5; the mass fraction of the hydrochloric acid solution is 10 - 37%.

[0007] Further, in step (2), the temperature of the first reaction is 40 - 65°C, and the reaction time is 5 - 7 h; the temperature of the second reaction is 20 - 35°C, and the reaction time is 3 - 6 h.

[0008] Further, in step (1), the preparation method of maleic anhydride - modified polyvinyl alcohol is as follows: 100 parts by weight of polyvinyl alcohol is added to dimethyl sulfoxide, and after heating and stirring, 15 - 50 parts by weight of maleic anhydride is added. The mixture is stirred and reacted at 60 - 70°C for 1 - 2 h. After cooling, acetone alcohol is added for dilution, followed by filtration, washing, and drying to obtain maleic anhydride - modified polyvinyl alcohol.

[0009] Further, in step (2), the preparation method of aminoethylimidazole quaternary ammonium salt is as follows: N - Boc - 2 - chloroethylamine and 1 - alkylimidazole with a molar ratio of (0.9 - 1):1 are added to N,N - dimethylformamide. The mixture is heated to 115 - 130°C and stirred for 24 - 30 h, followed by reduced - pressure distillation and washing. The product is added to a dichloromethane solution of trifluoroacetic acid and stirred at room temperature for 3 - 4 h, followed by reduced - pressure distillation, washing, and recrystallization to obtain aminoethylimidazole quaternary ammonium salt. Among them, the structural formula of 1 - alkylimidazole is , where a is any integer from 12 to 16. The reaction formula is: .

[0010] Beneficial technical effects: In the present invention, polylactic acid and maleic anhydride - modified polyvinyl alcohol containing carboxyl and ester groups are blended and electrospun to obtain polylactic acid composite fibers. Maleic anhydride - modified polyvinyl alcohol contains hydrophilic carboxyl groups, which is beneficial to improving the hydrophilicity of the composite fibers, showing a lower water contact angle. At the same time, maleic anhydride - modified polyvinyl alcohol contains ester groups similar to those of polylactic acid, which improves the solubility between polyvinyl alcohol and polylactic acid, improves their compatibility, and can avoid the phenomenon of phase separation between polyvinyl alcohol and polylactic acid during the electrospinning process, being beneficial to improving the toughness and elasticity of the fibers and showing a higher elongation at break.

[0011] In the present invention, glutaraldehyde is used as a cross - linker, and its double - end aldehyde groups react with the hydroxyl groups of polyvinyl alcohol in the composite fibers and the amino groups of aminoethylimidazole quaternary ammonium salt respectively, thereby chemically grafting the aminoethylimidazole quaternary ammonium salt onto the surface of the composite fibers. The quaternary ammonium salt cations are positively charged and have a strong bactericidal effect, significantly improving the antibacterial rate of the fibers against Escherichia coli and Staphylococcus aureus and showing strong antibacterial properties. Specific embodiments

[0012] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following provides a detailed description of the specific embodiments of the present invention.

[0013] The effective ingredient content of polylactic acid is 99%, purchased from Shandong Haizhou Bioengineering Co., Ltd. The polyvinyl alcohol model is 1799, purchased from Shandong Xiangzhao New Materials Co., Ltd.

[0014] Example 1: (1) Add 5 g of polyvinyl alcohol to 40 mL of dimethyl sulfoxide, heat and stir, then add 0.75 g of maleic anhydride, stir and react at 60 °C for 2 h, cool, dilute with acetone alcohol, filter, wash with acetone, and dry to obtain maleic anhydride-modified polyvinyl alcohol.

[0015] (2) Add 30 mmol of N-Boc-2-chloroethylamine and 30 mmol of 1-dodecylimidazole (CAS registration number 4303-67-7) to 30 mL of N,N-dimethylformamide, heat to 120 °C, stir and react for 30 h, distill under reduced pressure, wash with petroleum ether, add the product to 35 mL of a dichloromethane solution of 50% volume fraction trifluoroacetic acid, stir and react at room temperature for 3 h, distill under reduced pressure, wash with saturated sodium bicarbonate solution, and recrystallize the product in a mixed solution of dichloromethane and ethanol to obtain aminoethylimidazole quaternary ammonium salt. The structural formula is .

[0016] (3) Add 10 g of polylactic acid to 90 mL of dimethyl sulfoxide, heat and stir to dissolve to form a polylactic acid solution; add 6 g of maleic anhydride-modified polyvinyl alcohol to 90 mL of dimethyl sulfoxide, heat and stir to dissolve, then add the polylactic acid solution, stir and mix evenly, stand for degassing, pour the spinning solution into a syringe, and perform electrospinning through an electrospinning machine. Control the spinning voltage to be 15 kV, the spinning solution flow rate to be 0.5 mL / h, and receive to obtain polylactic acid composite fibers.

[0017] (4) Add 20 g of polylactic acid composite fibers and 2 mL of an aqueous solution containing 0.6 g of glutaraldehyde to 1.2 L of water, dropwise add a 30% mass fraction hydrochloric acid solution to adjust the pH to 6, heat to 50 °C, react for 5 h, then add 0.4 g of aminoethylimidazole quaternary ammonium salt, stir and react at 25 °C for 4 h, filter, wash successively with N,N-dimethylformamide, water, and ethanol, and dry to obtain quaternized polylactic acid antibacterial elastic composite fibers.

[0018] Example 2: (1) Add 5 g of polyvinyl alcohol to 50 mL of dimethyl sulfoxide, heat and stir, then add 2.5 g of maleic anhydride, stir and react at 65 °C for 2 h, cool, dilute with acetone alcohol, filter, wash with acetone, and dry to obtain maleic anhydride-modified polyvinyl alcohol.

[0019] (2) 27 mmol of N-Boc-2-chloroethylamine and 30 mmol of 1-hexadecylimidazole (CAS Registry Number: 58175-55-6) were added to 40 mL of N,N-dimethylformamide. The mixture was heated to 130 °C and stirred for 24 h. Then, it was distilled under reduced pressure and washed with petroleum ether. The product was added to a 35 mL dichloromethane solution containing 50% (v / v) trifluoroacetic acid and stirred at room temperature for 4 h. After distillation under reduced pressure, it was washed with saturated sodium bicarbonate solution. The product was recrystallized from a mixed solution of dichloromethane and ethanol to obtain the aminoethylimidazole quaternary ammonium salt. The structural formula is: 。

[0020] (3) 10 g of polylactic acid was added to 100 mL of dimethyl sulfoxide and heated with stirring to dissolve, forming a polylactic acid solution. 7 g of maleic anhydride-modified polyvinyl alcohol was added to 100 mL of dimethyl sulfoxide and heated with stirring to dissolve. Then, the polylactic acid solution was added, and after stirring and mixing evenly, it was left to stand for defoaming. The spinning solution was poured into a syringe and spun by an electrospinning machine. The spinning voltage was controlled at 10 kV, and the flow rate of the spinning solution was 0.8 mL / h. The product was collected to obtain the polylactic acid composite fiber.

[0021] (4) 20 g of the polylactic acid composite fiber and 5 mL of an aqueous solution containing 2 g of glutaraldehyde were added to 1.5 L of water. A 10% (w / w) hydrochloric acid solution was added dropwise to adjust the pH to 6.5. The mixture was heated to 65 °C and reacted for 5 h. Then, 1.5 g of the aminoethylimidazole quaternary ammonium salt was added, and the reaction was stirred at 20 °C for 6 h. The product was filtered and washed successively with N,N-dimethylformamide, water, and ethanol, and then dried to obtain the quaternized polylactic acid antibacterial elastic composite fiber.

[0022] Example 3: (1) 5 g of polyvinyl alcohol was added to 50 mL of dimethyl sulfoxide. After heating and stirring, 1.6 g of maleic anhydride was added, and the mixture was stirred at 70 °C for 1 h. After cooling, it was diluted with acetone alcohol, filtered, washed with acetone, and dried to obtain maleic anhydride-modified polyvinyl alcohol.

[0023] (2) 27 mmol of N-Boc-2-chloroethylamine and 30 mmol of 1-tetradecylimidazole (CAS Registry Number: 54004-47-6) were added to 30 mL of N,N-dimethylformamide. The mixture was heated to 115 °C and stirred for 30 h. Then, it was distilled under reduced pressure and washed with petroleum ether. The product was added to a 45 mL dichloromethane solution containing 40% (v / v) trifluoroacetic acid and stirred at room temperature for 4 h. After distillation under reduced pressure, it was washed with saturated sodium bicarbonate solution. The product was recrystallized from a mixed solution of dichloromethane and ethanol to obtain the aminoethylimidazole quaternary ammonium salt. The structural formula is: 。

[0024] (3) Add 10 g of polylactic acid to 100 mL of dimethyl sulfoxide, heat and stir to dissolve to form a polylactic acid solution; add 8 g of maleic anhydride-modified polyvinyl alcohol to 100 mL of dimethyl sulfoxide, heat and stir to dissolve, then add the polylactic acid solution, stir and mix well, stand for defoaming, pour the spinning solution into a syringe and spin it through an electrospinning machine, control the spinning voltage at 12 kV, the spinning solution flow rate at 0.4 mL / h, receive to obtain polylactic acid composite fibers.

[0025] (4) Add 20 g of polylactic acid composite fibers and 8 mL of an aqueous solution containing 3.6 g of glutaraldehyde to 1.5 L of water, dropwise add a hydrochloric acid solution with a mass fraction of 37% to adjust the pH to 5.5, heat to 40 °C, react for 7 h, then add 2.5 g of aminoethylimidazole quaternary ammonium salt, stir and react at 35 °C for 3 h, filter, wash successively with N,N-dimethylformamide, water, and ethanol, and dry to obtain quaternized polylactic acid antibacterial elastic composite fibers.

[0026] Comparative Example 1: (1) Add 10 g of polylactic acid to 90 mL of dimethyl sulfoxide, heat and stir to dissolve to form a polylactic acid solution; add 6 g of polyvinyl alcohol to 90 mL of dimethyl sulfoxide, heat and stir to dissolve, then add the polylactic acid solution, stir and mix well, stand for defoaming, pour the spinning solution into a syringe and spin it through an electrospinning machine, control the spinning voltage at 15 kV, the spinning solution flow rate at 0.5 mL / h, receive to obtain polylactic acid composite fibers.

[0027] Comparative Example 2: (1) Add 10 g of polylactic acid to 90 mL of dimethyl sulfoxide, heat and stir to dissolve to form a polylactic acid solution; add 6 g of maleic anhydride-modified polyvinyl alcohol (prepared in the same way as in Example 1) to 90 mL of dimethyl sulfoxide, heat and stir to dissolve, then add the polylactic acid solution, stir and mix well, stand for defoaming, pour the spinning solution into a syringe and spin it through an electrospinning machine, control the spinning voltage at 15 kV, the spinning solution flow rate at 0.5 mL / h, receive to obtain polylactic acid composite fibers.

[0028] Comparative Example 3: (1) Add 10 g of polylactic acid to 90 mL of dimethyl sulfoxide, heat and stir to dissolve to form a polylactic acid solution; add 6 g of polyvinyl alcohol to 90 mL of dimethyl sulfoxide, heat and stir to dissolve, then add the polylactic acid solution, stir and mix well, stand for defoaming, pour the spinning solution into a syringe and spin it through an electrospinning machine, control the spinning voltage at 15 kV, the spinning solution flow rate at 0.5 mL / h, receive to obtain polylactic acid composite fibers.

[0029] (2) Add 20 g of polylactic acid composite fiber and 2 mL of an aqueous solution containing 0.6 g of glutaraldehyde to 1.2 L of water. Dropwise add a 30% hydrochloric acid solution to adjust the pH to 6. Heat to 50 °C and react for 5 h. Then add 0.4 g of aminoethylimidazole quaternary ammonium salt and stir and react at 25 °C for 4 h. Filter, wash successively with N,N-dimethylformamide, water, and ethanol, and dry to obtain the polylactic acid composite fiber.

[0030] Comparative Example 4: (1) Add 30 mmol of 2-chloroethane and 30 mmol of 1-dodecylimidazole to 30 mL of N,N-dimethylformamide. Heat to 120 °C and stir and react for 30 h. Perform vacuum distillation, wash with petroleum ether, and dry to obtain ethylimidazole quaternary ammonium salt, the structural formula of which is .

[0031] (2) Add 20 g of polylactic acid composite fiber (prepared in the same way as in Example 1) and 2 mL of an aqueous solution containing 0.6 g of glutaraldehyde to 1.2 L of water. Dropwise add a 30% hydrochloric acid solution to adjust the pH to 6. Heat to 50 °C and react for 5 h. Then add 0.4 g of ethylimidazole quaternary ammonium salt and stir and react at 25 °C for 4 h. Filter, wash successively with N,N-dimethylformamide, water, and ethanol, and dry to obtain the polylactic acid composite fiber.

[0032] Test the antibacterial properties of the polylactic acid composite fiber according to the method specified in the standard GB / T 20944.3-2008. The test bacterial strains are Staphylococcus aureus or Escherichia coli. The control sample is the polylactic acid composite fiber of Comparative Example 1. The antibacterial samples are the polylactic acid composite fibers of Examples 1-3 and Comparative Examples 2-4.

[0033] Test the tensile properties of the polylactic acid composite fiber according to the method of GB / T 14344-2022. Each group of specimens is tested 5 times and the average value is taken.

[0034] Water contact angle test: Taking Example 1 as an example, (1) Add 10 g of polylactic acid to 90 mL of dimethyl sulfoxide, heat and stir to dissolve to make a polylactic acid solution; add 6 g of maleic anhydride-modified polyvinyl alcohol to 90 mL of dimethyl sulfoxide, heat and stir to dissolve, then add the polylactic acid solution, stir and mix well and let stand to defoam. Pour the spinning solution into a syringe and perform electrospinning through an electrospinning machine, controlling the spinning voltage at 15 kV and the spinning solution flow rate at 0.5 mL / h, receive, and accumulate the fibers on the collector to form a fiber membrane.

[0035] (2) Add 20 g of fiber membrane and 2 mL of aqueous solution containing 0.6 g of glutaraldehyde to 1.2 L of water. Dropwise add 30% hydrochloric acid solution to adjust the pH to 6. Heat to 50 °C and react for 5 h. Then add 0.4 g of aminoethylimidazole quaternary ammonium salt and stir and react at 25 °C for 4 h. Filter, wash successively with N,N-dimethylformamide, water, and ethanol, and dry to obtain the quaternized polylactic acid antibacterial elastic composite fiber membrane.

[0036] Using the dropping method, drop water droplets on the surface of the composite fiber membrane and measure the water contact angle through a contact angle tester. Measure the contact angles at 5 different positions and take the average value.

[0037] Table 1 Performance test of composite fiber

[0038] After testing, the water contact angle of the composite fiber in Comparative Example 1 reached 75.1°, with poor hydrophilicity, and the elongation at break was only 2.15%, showing poor toughness and elasticity. In Examples 1-4, glutaraldehyde was used as a cross-linking agent to chemically graft aminoethylimidazole quaternary ammonium salt onto the surface of the composite fiber. The quaternary ammonium salt cation is positively charged and has a strong bactericidal effect, significantly improving the antibacterial rate of the fiber against Escherichia coli and Staphylococcus aureus, showing strong antibacterial properties. And maleic anhydride-modified polyvinyl alcohol contains hydrophilic carboxyl groups, which is beneficial to improving the hydrophilicity of the fiber and has a lower water contact angle. At the same time, maleic anhydride-modified polyvinyl alcohol contains ester groups similar to those of polylactic acid, improving the solubility between polyvinyl alcohol and polylactic acid, improving their compatibility, and avoiding the phase separation phenomenon of polyvinyl alcohol and polylactic acid during the electrospinning process, which is beneficial to improving the toughness and elasticity of the fiber and showing a higher elongation at break.

[0039] In Comparative Example 2, aminoethylimidazole quaternary ammonium salt was not chemically grafted onto the surface of the composite fiber, resulting in poor antibacterial performance of the fiber. In Comparative Example 3, polyvinyl alcohol was not modified with maleic anhydride and did not contain hydrophilic carboxyl groups, resulting in a large water contact angle of the fiber and poor hydrophilic performance. And polyvinyl alcohol does not contain ester groups, with poor compatibility with polylactic acid, and phase separation of polyvinyl alcohol and polylactic acid will occur during the electrospinning process, affecting the toughness and elasticity of the composite fiber and resulting in a low elongation at break. In Comparative Example 4, ethylimidazole quaternary ammonium salt was added, which does not contain amino groups and cannot be chemically grafted onto the surface of the composite fiber through glutaraldehyde. After washing, the surface of the composite fiber does not contain quaternary ammonium salt groups, and the antibacterial performance of the fiber is poor.

[0040] Although the present invention has been described above with reference to the embodiments, various modifications can be made thereto and components thereof can be replaced with equivalents without departing from the scope of the present invention. In particular, as long as there is no structural conflict, the features in the embodiments disclosed in the present invention can be combined with each other in any way, and the exhaustive description of these combinations is not given in this specification only for the consideration of saving space and resources. Therefore, the present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for preparing quaternized polylactic acid antibacterial elastic composite fiber, characterized in that: The steps include: (1) Adding 100 parts by weight of polylactic acid to dimethyl sulfoxide, heating and stirring to dissolve, to prepare a polylactic acid solution; adding 60-80 parts by weight of maleic anhydride-modified polyvinyl alcohol to dimethyl sulfoxide, heating and stirring to dissolve, then adding the polylactic acid solution, stirring and mixing, and then standing to degas, pouring the spinning solution into a syringe, spinning and receiving it through an electrospinning machine, and obtaining a polylactic acid composite fiber; (2) adding 100 parts by weight of polylactic acid composite fibers and an aqueous solution containing 3-18 parts by weight of glutaraldehyde into water, dropping a hydrochloric acid solution, stirring for reaction, and then adding 2-10 parts by weight of aminoethyl imidazole quaternary ammonium salt, stirring for reaction, filtering, washing, and drying to obtain a quaternized polylactic acid antibacterial elastic composite fiber; The structural formula of the aminoethyl imidazole quaternary ammonium salt is ; a is any integer between 12 and 16.

2. The method for preparing the quaternized polylactic acid antibacterial elastic composite fiber according to claim 1, characterized in that: The voltage during spinning in (1) is 10-15 kV, and the spinning solution flow rate is 0.4-0.8 mL / h.

3. The method for preparing the quaternized polylactic acid antibacterial elastic composite fiber according to claim 1, characterized in that: In the step (2), a hydrochloric acid solution is added dropwise to adjust the pH to 5.5-6.5; the mass fraction of the hydrochloric acid solution is 10-37%.

4. The method for preparing the quaternized polylactic acid antibacterial elastic composite fiber according to claim 1, characterized in that: The temperature of the first reaction in (2) is 40-65°C, and the reaction time is 5-7h; the temperature of the second reaction is 20-35°C, and the reaction time is 3-6h.

5. The method for preparing the quaternized polylactic acid antibacterial elastic composite fiber according to claim 1, characterized in that: The preparation method of maleic anhydride modified polyvinyl alcohol in (1) is as follows: add 100 parts by weight of polyvinyl alcohol to dimethyl sulfoxide, add 15-50 parts by weight of maleic anhydride after heating and stirring, react at 60-70°C with stirring for 1-2h, add acetol to dilute after cooling, filter, wash, and dry to obtain maleic anhydride modified polyvinyl alcohol.

6. The method for preparing the quaternized polylactic acid antibacterial elastic composite fiber according to claim 1, characterized in that: The preparation method of the aminoethyl imidazole quaternary ammonium salt in (2) is as follows: add N-Boc-2-chloroethylamine and 1-alkyl imidazole to N,N-dimethylformamide, heat to 115-130°C, stir and react for 24-30 hours, distill under reduced pressure, wash, add the product to a dichloromethane solution of trifluoroacetic acid, stir and react for 3-4 hours at room temperature, distill under reduced pressure, wash, and recrystallize to obtain the aminoethyl imidazole quaternary ammonium salt.

7. The method for preparing the quaternized polylactic acid antibacterial elastic composite fiber according to claim 6, characterized in that: The molar ratio of the N-Boc-2-chloroethylamine to 1-alkylimidazole is (0.9-1):

1.

8. The method for preparing the quaternized polylactic acid antibacterial elastic composite fiber according to claim 7, characterized in that: The structural formula of the 1-alkylimidazole is , a is any integer between 12 and 16.

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