Preparation Method of Quaternized Polylactic Acid Antibacterial Elastic Composite Fiber

Abstract

The present invention relates to the technical field of fibers, and discloses a preparation method of a quaternized polylactic acid antibacterial elastic composite fiber. In the present invention, polylactic acid and maleic anhydride-modified polyvinyl alcohol are electrospun to obtain polylactic acid composite fibers; then they are reacted with glutaraldehyde and aminoethyl imidazole quaternary salt to obtain a quaternized polylactic acid antibacterial elastic composite fiber. Maleic anhydride-modified polyvinyl alcohol contains carboxyl hydrophilic groups and ester groups, which improves the hydrophilicity of the composite fiber and at the same time improves the compatibility of polylactic acid and polyvinyl alcohol, and can avoid the phenomenon of phase separation between the two during the electrospinning process, which is beneficial to improving the elongation at break, toughness and elasticity of the fiber. Using glutaraldehyde as a crosslinking agent, aminoethyl imidazole quaternary salt is chemically grafted onto the surface of the composite fiber, which improves the antibacterial rate of the fiber against Escherichia coli and Staphylococcus aureus and shows strong antibacterial properties.

Description

Technical Field

[0001] The invention relates to the technical field of fibers, in particular to a method for preparing quaternized polylactic acid antibacterial elastic composite fibers. Background Art

[0002] Polylactic acid (PLA) boasts excellent biocompatibility, biodegradability, and mechanical strength. It can be made into plastics, fibers, and other products, and is widely used in tissue engineering, medical supplies, and textiles. However, traditional PLA fibers suffer from poor hydrophilicity, low elongation at break, poor toughness and elasticity, and poor antibacterial properties, limiting their practical applications.

[0003] Polyvinyl alcohol has good biodegradability, hydrophilicity and spinnability, and has important applications in fiber products. By blending polyvinyl alcohol and polylactic acid, a composite fiber with better hydrophilicity and degradation performance can be obtained. Chinese patent CN112481731B discloses a copper ion antibacterial fiber and antibacterial fabric. The fibers are spun with polylactic acid, hydrophobically modified polyvinyl alcohol, and a copper-loaded nanoporous phosphorus-containing borosilicate ceramic powder antibacterial agent. The obtained fibers have good antibacterial and mechanical properties. However, this patent does not solve the problem of poor hydrophilicity of polylactic acid fibers. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the present invention provides a method for preparing quaternized polylactic acid antibacterial elastic composite fibers, which solves the problem of poor antibacterial performance of polylactic acid fibers and improves the hydrophilicity and resilience of polylactic acid fibers. The specific technical solution is as follows:

[0005] The preparation method of quaternized polylactic acid antibacterial elastic composite fiber comprises the following steps:

[0006] (1) Add 100 parts by weight of polylactic acid to dimethyl sulfoxide, heat and stir to dissolve, and prepare 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 thoroughly, let it stand for degassing, pour the spinning solution into a syringe, spin it through an electrospinning machine, and collect it to obtain a polylactic acid composite fiber;

[0007] (2) Add 100 parts by weight of polylactic acid composite fiber and an aqueous solution containing 3-18 parts by weight of glutaraldehyde to water, add hydrochloric acid solution dropwise, stir to react, then add 2-10 parts by weight of aminoethyl imidazole quaternary ammonium salt, stir to react, filter, wash, and dry to obtain quaternized polylactic acid antibacterial elastic composite fiber; wherein the structural formula of aminoethyl imidazole quaternary ammonium salt is ; a is any integer between 12 and 16.

[0008] Further, in the step (1), the voltage during electrospinning is 10 - 15 kV, and the flow rate of the spinning solution is 0.4 - 0.8 mL / h.

[0009] Further, in the step (2), 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%.

[0010] Further, in the 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.

[0011] Further, in the 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, and after filtration and washing, it is dried to obtain maleic anhydride modified polyvinyl alcohol.

[0012] Further, in the step (2), the preparation method of aminoethyl imidazole quaternary ammonium salt is as follows: N - Boc - 2 - chloroethylamine and 1 - alkyl imidazole with a molar ratio of (0.9 - 1):1 are added to N,N - dimethylformamide, and the mixture is heated to 115 - 130 °C and stirred and reacted for 24 - 30 h. Then, it is distilled under reduced pressure and washed. The product is added to a dichloromethane solution of trifluoroacetic acid, and the mixture is stirred and reacted at room temperature for 3 - 4 h. Then, it is distilled under reduced pressure, washed, and recrystallized to obtain aminoethyl imidazole quaternary ammonium salt. Among them, the structural formula of 1 - alkyl imidazole is , where a is any integer from among 12 - 16. The reaction formula is:

[0013] .

[0014] Beneficial technical effects:

[0015] 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 and 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 and improves their compatibility, and can avoid the phenomenon of phase separation between polyvinyl alcohol and polylactic acid during the electrospinning process, which is beneficial to improving the toughness and elasticity of the fibers and showing a higher elongation at break.

[0016] The present invention uses glutaraldehyde as a crosslinking agent. Its two-terminal aldehyde groups react with the hydroxyl groups of polyvinyl alcohol in the composite fiber and the amino groups of aminoethylimidazole quaternary salt respectively, thereby chemically grafting the aminoethylimidazole quaternary 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, and showing strong antibacterial properties. Detailed implementation manners

[0017] To make the above objects, features and advantages of the present invention more obvious and understandable, the following detailed description of the specific implementation manners of the present invention is provided.

[0018] 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.

[0019] Example 1:

[0020] (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.

[0021] (2) Add 30 mmol of N-Boc-2-chloroethylamine and 30 mmol of 1-dodecylimidazole (CAS registry 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 salt. The structural formula is .

[0022] (3) 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, stand for defoaming, pour the spinning solution into a syringe and spin through an electrospinning machine, control the spinning voltage at 15 kV, the spinning solution flow rate at 0.5 mL / h, and receive to obtain polylactic acid composite fiber.

[0023] (4) 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 hydrochloric acid solution with a mass fraction of 30% to adjust the pH to 6. Heat to 50 °C and react for 5 h. Then add 0.4 g of aminoethylimidazole quaternary 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 quaternized polylactic acid antibacterial elastic composite fiber.

[0024] Example 2:

[0025] (1) Add 5 g of polyvinyl alcohol to 50 mL of dimethyl sulfoxide. After heating and stirring, add 2.5 g of maleic anhydride and stir and react at 65 °C for 2 h. After cooling, dilute with acetone alcohol, filter, wash with acetone, and dry to obtain maleic anhydride-modified polyvinyl alcohol.

[0026] (2) Add 27 mmol of N-Boc-2-chloroethylamine and 30 mmol of 1-hexadecylimidazole (CAS registry number 58175-55-6) to 40 mL of N,N-dimethylformamide. Heat to 130 °C and stir and react for 24 h. Carry out vacuum distillation, wash with petroleum ether. Add the product to a dichloromethane solution of 35 mL of trifluoroacetic acid with a volume fraction of 50% and stir and react at room temperature for 4 h. Carry out vacuum distillation, wash with saturated sodium bicarbonate solution, and recrystallize the product in a mixed solution of dichloromethane and ethanol to obtain aminoethylimidazole quaternary salt. The structural formula is: .

[0027] (3) Add 10 g of polylactic acid to 100 mL of dimethyl sulfoxide, heat and stir to dissolve to make a polylactic acid solution; add 7 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, and stand for defoaming. Pour the spinning solution into a syringe and carry out electrospinning through an electrospinning machine. Control the spinning voltage at 10 kV and the flow rate of the spinning solution at 0.8 mL / h, and receive to obtain polylactic acid composite fiber.

[0028] (4) Add 20 g of polylactic acid composite fiber and 5 mL of an aqueous solution containing 2 g of glutaraldehyde to 1.5 L of water. Dropwise add a hydrochloric acid solution with a mass fraction of 10% to adjust the pH to 6.5. Heat to 65 °C and react for 5 h. Then add 1.5 g of aminoethylimidazole quaternary salt and stir and react at 20 °C for 6 h. Filter, wash successively with N,N-dimethylformamide, water, and ethanol, and dry to obtain quaternized polylactic acid antibacterial elastic composite fiber.

[0029] Example 3:

[0030] (1) Add 5 g of polyvinyl alcohol to 50 mL of dimethyl sulfoxide. After heating and stirring, add 1.6 g of maleic anhydride and stir for reaction at 70 °C for 1 h. After cooling, dilute with acetone alcohol, wash with acetone after filtration, and dry to obtain maleic anhydride-modified polyvinyl alcohol.

[0031] (2) Add 27 mmol of N-Boc-2-chloroethylamine and 30 mmol of 1-tetradecylimidazole (CAS registry number: 54004-47-6) to 30 mL of N,N-dimethylformamide. Heat to 115 °C and stir for reaction for 30 h. Distill under reduced pressure and wash with petroleum ether. Add the product to a 45 mL dichloromethane solution of 40% volume fraction trifluoroacetic acid and stir for reaction at room temperature for 4 h. Distill under reduced pressure and wash with saturated sodium bicarbonate solution. Recrystallize the product in a mixed solution of dichloromethane and ethanol to obtain aminoethylimidazole quaternary ammonium salt. The structural formula is: .

[0032] (3) Add 10 g of polylactic acid to 100 mL of dimethyl sulfoxide, heat and stir to dissolve to prepare 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 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 fiber.

[0033] (4) Add 20 g of polylactic acid composite fiber and 8 mL of an aqueous solution containing 3.6 g of glutaraldehyde to 1.5 L of water, dropwise add a 37% mass fraction hydrochloric acid solution 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 and stir for reaction 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 fiber.

[0034] Comparative example 1:

[0035] (1) Add 10 g of polylactic acid to 90 mL of dimethyl sulfoxide, heat and stir to dissolve to prepare 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 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 fiber.

[0036] Comparative example 2:

[0037] (1) Add 10 g of polylactic acid to 90 mL of dimethyl sulfoxide, heat and stir to dissolve it 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 it, then add the polylactic acid solution, stir and mix well, let it 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 flow rate of the spinning solution at 0.5 mL / h, and collect to obtain polylactic acid composite fibers.

[0038] Comparative Example 3:

[0039] (1) Add 10 g of polylactic acid to 90 mL of dimethyl sulfoxide, heat and stir to dissolve it to form a polylactic acid solution; add 6 g of polyvinyl alcohol to 90 mL of dimethyl sulfoxide, heat and stir to dissolve it, then add the polylactic acid solution, stir and mix well, let it 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 flow rate of the spinning solution at 0.5 mL / h, and collect to obtain polylactic acid composite fibers.

[0040] (2) 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, add a 30% hydrochloric acid solution dropwise 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 polylactic acid composite fibers.

[0041] Comparative Example 4:

[0042] (1) Add 30 mmol of 2-chloroethane and 30 mmol of 1-dodecylimidazole to 30 mL of N,N-dimethylformamide, heat to 120 °C, stir and react for 30 h, carry out vacuum distillation, wash with petroleum ether, and dry to obtain ethylimidazole quaternary ammonium salt, with the structural formula .

[0043] (2) Add 20 g of polylactic acid composite fibers (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, add a 30% hydrochloric acid solution dropwise to adjust the pH to 6, heat to 50 °C, react for 5 h, then add 0.4 g of ethylimidazole 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 polylactic acid composite fibers.

[0044] Test the antibacterial properties of the polylactic acid composite fiber according to the method specified in the standard GB / T 20944.3-2008, and the test bacteria 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.

[0045] 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.

[0046] 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, stand for defoaming, pour the spinning solution into a syringe and carry out electrospinning through an electrospinning machine, control the spinning voltage at 15 kV, the spinning solution flow rate at 0.5 mL / h, receive, and accumulate the fibers on the collector to form a fiber membrane.

[0047] (2) Add 20 g of the fiber membrane and 2 mL of an aqueous solution containing 0.6 g of glutaraldehyde to 1.2 L of water, add a hydrochloric acid solution with a mass fraction of 30% dropwise 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 a quaternized polylactic acid antibacterial elastic composite fiber membrane.

[0048] Adopt the drop method, drop water droplets on the surface of the composite fiber membrane, and test the water contact angle through a contact angle tester. Test the contact angles at 5 different positions and take the average value.

[0049] Table 1 Performance test of composite fiber

[0050]

[0051] After testing, the water contact angle of the composite fiber of Comparative Example 1 reached 75.1°, with poor hydrophilicity. The elongation at break was only 2.15%, and the toughness and elasticity were not good. In Examples 1-4, glutaraldehyde was used as a crosslinking agent to chemically graft aminoethylimidazole quaternary ammonium salt onto the surface of the composite fiber. The quaternary ammonium salt cation was positively charged and had a strong bactericidal effect, significantly improving the antibacterial rate of the fiber against Escherichia coli and Staphylococcus aureus, showing strong antibacterial properties. Moreover, maleic anhydride-modified polyvinyl alcohol contained hydrophilic carboxyl groups, which was beneficial to improving the hydrophilicity of the fiber and had a lower water contact angle. At the same time, maleic anhydride-modified polyvinyl alcohol contained ester groups similar to those of polylactic acid, improving the solubility between polyvinyl alcohol and polylactic acid, enhancing their compatibility, and avoiding the phase separation phenomenon of polyvinyl alcohol and polylactic acid during the electrospinning process, which was beneficial to improving the toughness and elasticity of the fiber and showing a higher elongation at break.

[0052] In Comparative Example 2, aminoethylimidazole quaternary ammonium salt was not chemically grafted onto the surface of the composite fiber, resulting in poor antibacterial properties 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 properties. Moreover, polyvinyl alcohol did not contain ester groups, and its compatibility with polylactic acid was poor. Phase separation of polyvinyl alcohol and polylactic acid occurred 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 did not contain an amino group and could not be chemically grafted onto the surface of the composite fiber through glutaraldehyde. After washing, the surface of the composite fiber did not contain quaternary ammonium salt groups, and the antibacterial properties of the fiber were poor.

[0053] Although the present invention has been described above with reference to the embodiments, various improvements can be made to it and components therein 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 various features in the disclosed embodiments of the present invention can be combined with each other in any way. The exhaustive description of these combinations is not given in this specification only for the sake 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) Add 100 parts by weight of polylactic acid to dimethyl sulfoxide, heat and stir to dissolve, and prepare 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 thoroughly, let it stand for degassing, pour the spinning solution into a syringe, spin it through an electrospinning machine, and collect it to obtain a polylactic acid composite fiber; (2) adding 100 parts by weight of polylactic acid composite fiber and an aqueous solution containing 3-18 parts by weight of glutaraldehyde to water, adding hydrochloric acid solution dropwise, stirring to react, then adding 2-10 parts by weight of aminoethyl imidazole quaternary ammonium salt, stirring to react, filtering, washing, and drying to obtain 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, heat and stir, then add 15-50 parts by weight of maleic anhydride, stir and react at 60-70°C for 1-2 hours, cool, add acetol to dilute, 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 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 at room temperature for 3-4 hours, distill under reduced pressure, wash, and recrystallize to obtain 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 and 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-alkyl imidazole is , a is any integer between 12 and 16.

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