A superhydrophobic flame-retardant fiber and its preparation method

Abstract

The present invention discloses a superhydrophobic flame-retardant fiber and a preparation method thereof, relating to the field of fibers. When preparing the superhydrophobic flame-retardant fiber of the present invention, pretreated polyacrylonitrile grafted with melamine is reacted with diallyl chlorophosphite, and then reacted with 5-mercaptosalicylic acid to obtain modified polyacrylonitrile; silica is reacted with tetramethylguanidinopropyltrimethoxysilane to obtain modified silica; the modified polyacrylonitrile and the modified silica are blended and spun, and finally finished with acrylamide and perfluorooctylethylene to obtain the superhydrophobic flame-retardant fiber. The fiber prepared by the present invention has excellent hydrophobicity, flame retardancy, antibacterial property and ultraviolet resistance.

Description

Technical Field

[0001] The present invention relates to the field of fibers, and particularly to a superhydrophobic flame-retardant fiber and a preparation method thereof. Background Art

[0002] In the development of textile material technology, the pursuit of multifunctionality has become an important research direction. Although traditional fibers can meet daily needs to a certain extent, they often lack special functions, which limits their applicability in different environments.

[0003] With the popularization of outdoor activities, people's demand for outdoor products has gradually increased. The safety and practicality of outdoor products such as tents and outdoor clothing have become one of the focuses of people's attention. In outdoor activities, flame-retardant fiber products can well avoid safety hazards brought by activities such as picnics and bonfire parties; superhydrophobic fiber products can help people cope with harsh outdoor weather such as rain and snow at any time. Therefore, a fiber with both hydrophobic and flame-retardant properties is needed. Similarly, in order to further broaden the application fields of fibers, other properties can also be imparted to the fibers, such as antibacterial and ultraviolet resistance. The present invention prepares a superhydrophobic flame-retardant fiber, which not only has excellent flame retardancy and hydrophobicity, but also has persistent antibacterial and ultraviolet resistance characteristics, overcoming the problem of single function in the prior art, and thus has an important application prospect in the field of high-performance textiles. Summary of the Invention

[0004] The purpose of the present invention is to provide a superhydrophobic flame-retardant fiber and a preparation method thereof to solve the problems existing in the prior art.

[0005] To solve the above technical problems, the present invention provides the following technical solutions:

[0006] A superhydrophobic flame-retardant fiber, wherein the superhydrophobic flame-retardant fiber is prepared by grafting pretreated polyacrylonitrile with melamine, reacting with diallyl chlorophosphite, and then reacting with 5-mercaptosalicylic acid to obtain modified polyacrylonitrile; reacting silica with tetramethylguanidinopropyltrimethoxysilane to obtain modified silica; blending and spinning the modified polyacrylonitrile and the modified silica, and finally finishing with acrylamide and perfluorooctylethylene.

[0007] A preparation method of a superhydrophobic flame-retardant fiber, comprising the following preparation steps:

[0008] (1)Mix pre-treated polyacrylonitrile, melamine, N,N'-dicyclohexylcarbodiimide, N,N-dimethylformamide, and boric acid evenly at a mass ratio of 1:1 - 2:0.5 - 0.8:100 - 120:0.1 - 0.2. React at 60 °C for 4 h, then cool to room temperature. Add dichloromethane that is 100 - 120 times the mass of the pre-treated polyacrylonitrile, filter, and wash with pure water 3 - 4 times. Dry at 60 °C for 12 - 14 h to obtain melamine-modified polyacrylonitrile.

[0009] (2)Mix melamine-modified polyacrylonitrile, acetonitrile, and triethylamine evenly at a mass ratio of 1:20 - 30:0.1 - 0.3 to obtain Solution A. Prepare Solution B by dissolving diallyl chlorophosphite in acetonitrile at a concentration of 2 - 3 g / mL. At 80 °C, add Solution B with a volume 0.02 - 0.04 times that of Solution A dropwise to Solution A at a dropping rate of 0.25 mL / min. After the dropping is completed, continue to react for 6 - 8 h. Add dichloromethane that is 40 - 50 times the mass of the melamine-modified polyacrylonitrile, filter, and wash with pure water 3 - 4 times. Dry at 60 °C for 12 - 14 h to obtain a modified polyacrylonitrile precursor.

[0010] (3)Mix the modified polyacrylonitrile precursor, 5-mercaptosalicylic acid, and N,N-dimethylformamide evenly at a mass ratio of 1:2 - 3:20 - 30. Add 2,2-dimethoxy-2-phenylacetophenone with a mass 0.1 - 0.3 times that of the modified polyacrylonitrile precursor, ultrasonicate at 20 - 40 kHz for 20 - 30 min, irradiate with ultraviolet light at room temperature for 30 min with an ultraviolet light power of 500 w. Add dichloromethane that is 40 - 50 times the mass of the modified polyacrylonitrile precursor, filter, and wash with pure water 3 - 4 times. Dry at 60 °C for 12 - 14 h to obtain modified polyacrylonitrile.

[0011] (4)Mix silica and absolute ethanol evenly at a mass ratio of 1:20 - 30, ultrasonically disperse at 20 - 40 kHz for 20 - 30 min, add a mixed solution of tetramethylguanidinopropyltrimethoxysilane with the same volume as the absolute ethanol, stir at 60 - 80 °C for 4 h with a stirring speed of 400 - 500 r / min. After stirring, perform suction filtration, wash with pure water 5 - 7 times, and dry at 60 °C for 6 - 8 h to obtain modified silica.

[0012] (5)Mix the modified silica and N,N-dimethylformamide at a mass-to-volume ratio of 1 - 5:100, ultrasonicate at 20 - 40 kHz for 30 - 40 min, add modified polyacrylonitrile with a mass 10 - 20 times that of the modified silica, stir at 5 - 10 °C for 2 - 3 h with a stirring speed of 400 - 600 r / min, and ultrasonically defoam at 20 - 40 kHz for 30 - 40 min to obtain a spinning solution.

[0013] (6) Aspirate the spinning solution with a syringe, extrude the spinning solution through a needle, and the extruded spinning solution enters the coagulating liquid to obtain nascent fibers. The nascent fibers are successively subjected to primary mechanical drawing, secondary mechanical drawing, and tertiary mechanical drawing and a drawing box to obtain drawn fibers. Finally, the drawn fibers are collected on a winding roller to obtain modified polyacrylonitrile fibers;

[0014] (7) After mixing the modified polyacrylonitrile fibers and acetonitrile evenly, add acrylamide and stir for 1 - 2 h at a stirring speed of 200 - 300 r / min. Add ethylene glycol dimethacrylate, perfluorooctylethylene, and azobisisobutyronitrile. Under nitrogen protection, react at 60 °C for 12 - 14 h. Filter by suction and wash with pure water 3 - 4 times. Dry at 60 °C for 12 - 14 h to obtain superhydrophobic flame-retardant fibers.

[0015] As an optimization, the preparation method of the pretreated polyacrylonitrile described in step (1) is to mix polyacrylonitrile, sodium hydroxide, and water in a mass ratio of 1:8 - 15:100 - 150 evenly, stir at 60 °C for 1 - 2 h, with a stirring speed of 200 r / min. Filter by suction and wash with pure water 3 - 4 times. Dry in a vacuum drying oven for 6 - 8 h. The vacuum degree of the vacuum drying oven is 0.08 MPa, the temperature is 50 °C, and the molecular weight of polyacrylonitrile is 53000.

[0016] As an optimization, the preparation method of 5-mercaptosalicylic acid described in step (3) is to stir 5-(sulfonyl chloride)salicylic acid, tin granules, and concentrated hydrochloric acid in a mass ratio of 1:3 - 5:20 - 30 for 14 - 16 h, with a stirring speed of 200 - 300 r / min. Cool to room temperature, filter, add ether with the same volume as the concentrated hydrochloric acid, filter again, take the filtrate, and perform vacuum distillation on the filtrate to remove ether. Recrystallize with ethanol-water to obtain 5-mercaptosalicylic acid. The purity of the tin granules is greater than 99.99%, and the particle size is 2 - 4 mm.

[0017] As an optimization, the silica in step (4) has a model of HN-SP1, a content greater than 99.5%, a particle size of 30 nm, and a specific surface area of 640 m 2 / g.

[0018] As an optimization, the preparation method of the tetramethylguanidinopropyltrimethoxysilane mixture described in step (4) is to adjust the pH of a 50 wt% ethanol aqueous solution to 3.5 - 4.5 with glacial acetic acid, and add tetramethylguanidinopropyltrimethoxysilane and mix evenly. The mass-volume ratio of tetramethylguanidinopropyltrimethoxysilane to the 50 wt% ethanol aqueous solution is 7 - 9:100.

[0019] As an optimization, the syringe used in step (6) has a specification of 20 mL, the inner diameter of the needle is 0.5 mm, the extrusion speed is 0.38 - 0.42 mL / min, the coagulating liquid is prepared by mixing N,N-dimethylformamide and water in a volume ratio of 1:1, the rotation speed of the first drafting roller is 20 r / min, the rotation speed of the second drafting roller is 32 r / min, the rotation speed of the third drafting roller is 36 r / min, the temperature of the drafting box is 115 °C, and the rotation speed of the winding roller is 38 r / min.

[0020] As an optimization, the dosages of the modified polyacrylonitrile, acetonitrile, acrylamide, ethylene glycol dimethacrylate, perfluorooctyl ethylene, and azobisisobutyronitrile in step (7) are as follows by mass parts: 7 - 9 parts of modified polyacrylonitrile, 50 - 60 parts of acetonitrile, 10 - 20 parts of acrylamide, 10 - 20 parts of ethylene glycol dimethacrylate, 7 - 8 parts of perfluorooctyl ethylene, and 1 - 3 parts of azobisisobutyronitrile.

[0021] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0022] When preparing the superhydrophobic flame-retardant fiber in the present invention, the pretreated polyacrylonitrile is grafted with melamine and then reacted with diallyl chlorophosphite, and then reacted with 5-mercaptosalicylic acid to obtain modified polyacrylonitrile; silica is reacted with tetramethylguanidinopropyltrimethoxysilane to obtain modified silica; the modified polyacrylonitrile and modified silica are melt-spun, and finally finished with acrylamide and perfluorooctyl ethylene to obtain the superhydrophobic flame-retardant fiber.

[0023] First, the pretreated polyacrylonitrile is grafted with melamine and then reacted with diallyl chlorophosphite, and then reacted with 5-mercaptosalicylic acid to obtain modified polyacrylonitrile; using sodium hydroxide to pretreat polyacrylonitrile is to perform alkaline hydrolysis on polyacrylonitrile, convert the cyano group in polypropylene into a carboxyl group, provide active sites for subsequent functional modification, then perform a condensation reaction between the amino group of melamine and the carboxyl group on polyacrylonitrile to introduce a nitrogen-based flame retardant on the surface of polyacrylonitrile, and then use diallyl chlorophosphite to react with the amino group of melamine to form a phosphorus-nitrogen-based flame retardant to provide good flame retardancy for polyacrylonitrile while introducing double bonds. Utilize the thiol-ene click reaction between the thiol group of 5-mercaptosalicylic acid and the double bond to introduce a salicylic acid structure. The carbonyl group and hydroxyl group in the salicylic acid structure can form an internal hydrogen bond to form a chelate ring. After absorbing the energy of ultraviolet light, molecular thermal vibration occurs, the internal hydrogen bond is broken, and the chelate ring is opened to release the energy of ultraviolet light as heat energy, thereby endowing the fiber prepared by the present invention with the ability to resist ultraviolet rays.

[0024] Secondly, modified silica is prepared by reacting silica with tetramethylguanidinopropyltrimethoxysilane. Tetramethylguanidinopropyltrimethoxysilane reacts with the hydroxyl groups on the surface of silica to obtain hydrophobic silica, and a guanidyl group with antibacterial properties is introduced onto the silica surface, endowing the silica with certain antibacterial properties, thereby endowing the fibers prepared by the present invention with antibacterial ability.

[0025] Finally, the modified polyacrylonitrile and the modified silica are wet-spun to obtain modified polyacrylonitrile fibers, and superhydrophobic flame-retardant fibers are prepared by finishing with acrylamide and perfluorooctylethylene. The modified polyacrylonitrile with a salicylic acid structure and the modified silica with a guanidyl group can undergo a neutralization reaction through simple blending to obtain a quaternary ammonium salt spinning solution. The fibers prepared from this spinning solution can further improve the antibacterial properties; after the modified polyacrylonitrile and the modified silica undergo a neutralization reaction, there are still some unreacted salicylic acid structures on the modified polyacrylonitrile. Therefore, there are unreacted salicylic acid structures on the modified polyacrylonitrile fibers after spinning. The amide group in acrylamide forms a stable complex with the carboxyl group and phenolic hydroxyl group in salicylic acid through hydrogen bonding and electrostatic attraction. The ester group in ethylene glycol dimethacrylate can interact with acrylamide and salicylic acid. Azobisisobutyronitrile acts as a radical initiator and decomposes to generate free radicals. These free radicals attack the unsaturated double bonds in acrylamide, ethylene glycol dimethacrylate, and perfluorooctylethylene, thereby initiating a polymerization reaction to fix perfluorooctylethylene with a low surface energy on the fibers, further increasing the hydrophobic properties of the fibers. Specific embodiments

[0026] The following will combine the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0027] The molecular weight of the polyacrylonitrile used in all the following examples and comparative examples is 53,000, purchased from Shanghai Jinshan Petrochemical Co., Ltd.; the silica is HN-SP1, with a content greater than 99.5%, a particle size of 30 nm, and a specific surface area of 640 m 2 / g, purchased from Zhejiang Zhoushan Mingri Nano Co., Ltd.; the tin grains have a purity greater than 99.99% and a particle size of 2 - 4 mm, purchased from Nangong Yingtai Metal Materials Co., Ltd. Example 1

[0028] A preparation method of superhydrophobic flame-retardant fibers, the preparation method of the superhydrophobic flame-retardant fibers comprising the following preparation steps:

[0029] (1) Mix polyacrylonitrile, sodium hydroxide, and water evenly at a mass ratio of 1:8:100, stir at 60 °C for 2 h with a stirring speed of 200 r / min, filter by suction and wash 4 times with pure water, and dry in a vacuum drying oven for 8 h. The vacuum degree of the vacuum drying oven is 0.08 MPa and the temperature is 50 °C;

[0030] (2) Mix the pretreated polyacrylonitrile, melamine, N,N'-dicyclohexylcarbodiimide, N,N-dimethylformamide, and boric acid evenly at a mass ratio of 1:1:0.5:100:0.1. After reacting at 60 °C for 4 h, cool to room temperature, add dichloromethane 100 times the mass of the pretreated polyacrylonitrile, filter and wash 3 times with pure water, and dry at 60 °C for 14 h to obtain melamine-modified polyacrylonitrile;

[0031] (3) Mix the melamine-modified polyacrylonitrile, acetonitrile, and triethylamine evenly at a mass ratio of 1:20:0.1 to obtain Solution A; prepare Solution B with a concentration of 2 g / mL of diallyl chlorophosphite in acetonitrile; at 80 °C, add Solution B with a volume 0.02 times that of Solution A dropwise to Solution A at a dropping speed of 0.25 mL / min. After the dropping is completed, continue to react for 6 h, add dichloromethane 40 times the mass of the melamine-modified polyacrylonitrile, filter and wash 3 times with pure water, and dry at 60 °C for 14 h to obtain a modified polyacrylonitrile precursor;

[0032] (4) Stir 5-(sulfonyl chloride) salicylic acid, tin granules, and concentrated hydrochloric acid at a mass ratio of 1:3:20 for 16 h with a stirring speed of 200 r / min, cool to room temperature, filter, add ether with the same volume as the concentrated hydrochloric acid, filter again, take the filtrate, perform vacuum distillation on the filtrate to remove ether, and recrystallize with ethanol-water to obtain 5-mercapto salicylic acid;

[0033] (5) Mix the modified polyacrylonitrile precursor, 5-mercapto salicylic acid, and N,N-dimethylformamide evenly at a mass ratio of 1:2:20, add 2,2-dimethoxy-2-phenylacetophenone with a mass 0.1 times that of the modified polyacrylonitrile precursor, perform ultrasonic treatment at 40 kHz for 30 min, irradiate with ultraviolet light at room temperature for 30 min with an ultraviolet light power of 500 w, add dichloromethane 40 times the mass of the modified polyacrylonitrile precursor, filter and wash 3 times with pure water, and dry at 60 °C for 14 h to obtain modified polyacrylonitrile;

[0034] (6) Adjust the pH of a 50 wt% ethanol aqueous solution to 3.5 with glacial acetic acid, add tetramethylguanidylpropyltrimethoxysilane and mix evenly to obtain a tetramethylguanidylpropyltrimethoxysilane mixture, where the mass-volume ratio of tetramethylguanidylpropyltrimethoxysilane to the 50 wt% ethanol aqueous solution is 7:100;

[0035] (7) Mix silica and absolute ethanol evenly at a mass ratio of 1:20, disperse them by ultrasonic wave at 20 kHz for 20 min, add a mixed solution of tetramethylguanidinopropyltrimethoxysilane with the same volume as absolute ethanol, stir at 80 °C for 4 h, the stirring speed is 500 r / min, perform suction filtration after stirring, wash with pure water for 7 times, and dry at 60 °C for 8 h to obtain modified silica;

[0036] (8) Mix modified silica and N,N-dimethylformamide at a mass-volume ratio of 1:100, ultrasonic wave at 40 kHz for 30 min, add modified polyacrylonitrile which is 10 times the mass of modified silica, stir at 5 °C for 3 h, the stirring speed is 600 r / min, and ultrasonic wave to remove bubbles at 40 kHz for 40 min to obtain a spinning solution;

[0037] (9) Aspirate the spinning solution with a 20 mL syringe, extrude the spinning solution through a needle with an inner diameter of 0.5 mm at an extrusion speed of 0.38 mL / min, and the extruded spinning solution enters the coagulating bath to obtain nascent fibers. The coagulating bath is prepared by mixing N,N-dimethylformamide and water at a volume ratio of 1:1. The nascent fibers are successively subjected to primary mechanical drawing, secondary mechanical drawing, and tertiary mechanical drawing and a drawing box to obtain drawn fibers. The rotation speed of the primary drawing roller is 20 r / min, the rotation speed of the secondary drawing roller is 32 r / min, the rotation speed of the tertiary drawing roller is 36 r / min, and the temperature of the drawing box is 115 °C. Finally, the drawn fibers are collected on a winding roller, and the rotation speed of the winding roller is 38 r / min to obtain modified polyacrylonitrile fibers;

[0038] (10) Weigh by mass parts: 7 parts of modified polyacrylonitrile, 50 parts of acetonitrile, 10 parts of acrylamide, 10 parts of ethylene glycol dimethacrylate, 7 parts of perfluorooctylethylene, and 1 part of azobisisobutyronitrile. After mixing the modified polyacrylonitrile fibers and acetonitrile evenly, add acrylamide and stir for 1 h, the stirring speed is 200 r / min, add ethylene glycol dimethacrylate, perfluorooctylethylene, and azobisisobutyronitrile, under nitrogen protection, at 60 °C, react for 12 h, perform suction filtration and wash with pure water for 3 times, and dry at 60 °C for 12 h to obtain superhydrophobic flame-retardant fibers. Example 2

[0039] A preparation method of superhydrophobic flame-retardant fibers, the preparation method of the superhydrophobic flame-retardant fibers includes the following preparation steps:

[0040] (1) Mix polyacrylonitrile, sodium hydroxide, and water evenly at a mass ratio of 1:10:120, stir at 60 °C for 1.5 h, the stirring speed is 200 r / min, perform suction filtration and wash with pure water for 4 times, and dry in a vacuum drying oven for 7 h. The vacuum degree of the vacuum drying oven is 0.08 MPa, and the temperature is 50 °C;

[0041] (2) Mix the pretreated polyacrylonitrile, melamine, N,N'-dicyclohexylcarbodiimide, N,N-dimethylformamide, and boric acid evenly at a mass ratio of 1:1.5:0.7:110:0.15. React at 60 °C for 4 h, then cool to room temperature. Add dichloromethane with a mass 110 times that of the pretreated polyacrylonitrile, filter, and wash 4 times with pure water. Dry at 60 °C for 13 h to obtain melamine-modified polyacrylonitrile.

[0042] (3) Mix the melamine-modified polyacrylonitrile, acetonitrile, and triethylamine evenly at a mass ratio of 1:25:0.2 to obtain Solution A; prepare Solution B by dissolving diallyl chlorophosphite in acetonitrile at a concentration of 2.5 g / mL. At 80 °C, add Solution B with a volume 0.03 times that of Solution A dropwise to Solution A at a dropping rate of 0.25 mL / min. After the dropping is complete, continue to react for 7 h. Add dichloromethane with a mass 45 times that of the melamine-modified polyacrylonitrile, filter, and wash 4 times with pure water. Dry at 60 °C for 13 h to obtain a modified polyacrylonitrile precursor.

[0043] (4) Stir 5-(sulfonyl chloride) salicylic acid, tin granules, and concentrated hydrochloric acid at a mass ratio of 1:4:25 for 15 h at a stirring speed of 250 r / min. Cool to room temperature, filter, add ether with the same volume as the concentrated hydrochloric acid, filter again, take the filtrate, perform vacuum distillation on the filtrate to remove ether, and recrystallize with ethanol-water to obtain 5-mercapto salicylic acid.

[0044] (5) Mix the modified polyacrylonitrile precursor, 5-mercapto salicylic acid, and N,N-dimethylformamide evenly at a mass ratio of 1:2.5:25. Add 2,2-dimethoxy-2-phenylacetophenone with a mass 0.2 times that of the modified polyacrylonitrile precursor, perform ultrasonic treatment at 25 kHz for 25 min, irradiate with ultraviolet light at room temperature for 30 min with an ultraviolet light power of 500 w. Add dichloromethane with a mass 45 times that of the modified polyacrylonitrile precursor, filter, and wash 3 times with pure water. Dry at 60 °C for 13 h to obtain modified polyacrylonitrile.

[0045] (6) Adjust the pH of a 50 wt% ethanol aqueous solution to 4 with glacial acetic acid, add tetramethylguanidinopropyltrimethoxysilane and mix evenly to obtain a tetramethylguanidinopropyltrimethoxysilane mixture, where the mass-volume ratio of tetramethylguanidinopropyltrimethoxysilane to the 50 wt% ethanol aqueous solution is 8:100.

[0046] (7) Mix silicon dioxide and absolute ethanol evenly at a mass ratio of 1:25, perform ultrasonic dispersion at 30 kHz for 25 min, add the tetramethylguanidinopropyltrimethoxysilane mixture with the same volume as the absolute ethanol, stir at 75 °C for 4 h at a stirring speed of 450 r / min. After stirring, perform suction filtration, wash 6 times with pure water, and dry at 60 °C for 7 h to obtain modified silicon dioxide.

[0047] (8) Mix the modified silica and N,N-dimethylformamide at a mass-to-volume ratio of 3:100, ultrasonicate for 35 min at 25 kHz, add modified polyacrylonitrile 15 times the mass of the modified silica, stir at 5 °C for 2.5 h with a stirring speed of 500 r / min, and ultrasonically defoam for 35 min at 30 kHz to obtain a spinning solution;

[0048] (9) Aspirate the spinning solution with a 20 mL syringe, extrude the spinning solution through a needle with an inner diameter of 0.5 mm at an extrusion speed of 0.40 mL / min, and the extruded spinning solution enters the coagulation bath to obtain nascent fibers. The coagulation bath is prepared by mixing N,N-dimethylformamide and water at a volume ratio of 1:1. The nascent fibers are successively subjected to primary mechanical drawing, secondary mechanical drawing, and tertiary mechanical drawing and a drawing box to obtain drawn fibers. The rotation speed of the primary drawing roller is 20 r / min, the rotation speed of the secondary drawing roller is 32 r / min, the rotation speed of the tertiary drawing roller is 36 r / min, and the temperature of the drawing box is 115 °C. Finally, the drawn fibers are collected on a winding roller with a winding roller rotation speed of 38 r / min to obtain modified polyacrylonitrile fibers;

[0049] (10) Weigh by mass parts: 8 parts of modified polyacrylonitrile, 55 parts of acetonitrile, 15 parts of acrylamide, 15 parts of ethylene glycol dimethacrylate, 7 parts of perfluorooctylethylene, and 2 parts of azobisisobutyronitrile. After mixing the modified polyacrylonitrile fibers and acetonitrile evenly, add acrylamide and stir for 1.5 h with a stirring speed of 250 r / min. Add ethylene glycol dimethacrylate, perfluorooctylethylene, and azobisisobutyronitrile, and react at 60 °C for 13 h under nitrogen protection. Filter and wash 3 times with pure water, and dry at 60 °C for 13 h to obtain superhydrophobic flame-retardant fibers. Example 3

[0050] A preparation method of superhydrophobic flame-retardant fibers, the preparation method of the superhydrophobic flame-retardant fibers comprising the following preparation steps:

[0051] (1) Mix polyacrylonitrile, sodium hydroxide, and water evenly at a mass ratio of 1:15:150, stir at 60 °C for 1 h with a stirring speed of 200 r / min, filter and wash 4 times with pure water, and dry in a vacuum drying oven for 6 h. The vacuum degree of the vacuum drying oven is 0.08 MPa and the temperature is 50 °C;

[0052] (2) Mix the pretreated polyacrylonitrile, melamine, N,N'-dicyclohexylcarbodiimide, N,N-dimethylformamide, and boric acid evenly at a mass ratio of 1:2:0.8:120:0.2. After reacting at 60 °C for 4 h, cool to room temperature, add dichloromethane 120 times the mass of the pretreated polyacrylonitrile, filter and wash 4 times with pure water, and dry at 60 °C for 14 h to obtain melamine-modified polyacrylonitrile;

[0053] (3) Mix melamine-modified polyacrylonitrile, acetonitrile, and triethylamine evenly at a mass ratio of 1:30:0.3 to obtain Solution A; prepare Solution B by dissolving diallyl chlorophosphite in acetonitrile at a concentration of 3 g / mL. At 80 °C, add Solution B with a volume 0.04 times that of Solution A dropwise to Solution A at a dropping rate of 0.25 mL / min. After the dropping is completed, continue the reaction for 8 h. Add dichloromethane with a mass 50 times that of the melamine-modified polyacrylonitrile, filter, and wash 4 times with pure water. Dry at 60 °C for 12 h to obtain a modified polyacrylonitrile precursor.

[0054] (4) Stir 5-(sulfonyl chloride) salicylic acid, tin granules, and concentrated hydrochloric acid at a mass ratio of 1:5:30 for 14 h at a stirring speed of 300 r / min. Cool to room temperature, filter, add ether with the same volume as the concentrated hydrochloric acid, filter again, take the filtrate, perform vacuum distillation on the filtrate to remove ether, and recrystallize with ethanol-water to obtain 5-mercapto salicylic acid.

[0055] (5) Mix the modified polyacrylonitrile precursor, 5-mercapto salicylic acid, and N,N-dimethylformamide evenly at a mass ratio of 1:3:30. Add 2,2-dimethoxy-2-phenylacetophenone with a mass 0.3 times that of the modified polyacrylonitrile precursor, ultrasonicate at 20 kHz for 20 min, irradiate with ultraviolet light at room temperature for 30 min with an ultraviolet light power of 500 w. Add dichloromethane with a mass 50 times that of the modified polyacrylonitrile precursor, filter, and wash 4 times with pure water. Dry at 60 °C for 14 h to obtain modified polyacrylonitrile.

[0056] (6) Adjust the pH of a 50 wt% ethanol aqueous solution to 4.5 using glacial acetic acid, add tetramethylguanidinopropyltrimethoxysilane and mix evenly to obtain a tetramethylguanidinopropyltrimethoxysilane mixture, where the mass-volume ratio of tetramethylguanidinopropyltrimethoxysilane to the 50 wt% ethanol aqueous solution is 9:100.

[0057] (7) Mix silica and absolute ethanol evenly at a mass ratio of 1:30, ultrasonically disperse at 40 kHz for 30 min, add the tetramethylguanidinopropyltrimethoxysilane mixture with the same volume as the absolute ethanol, stir at 60 °C for 4 h at a stirring speed of 400 r / min. After the stirring is completed, perform suction filtration, wash 7 times with pure water, and dry at 60 °C for 8 h to obtain modified silica.

[0058] (8) Mix the modified silica and N,N-dimethylformamide at a mass-volume ratio of 5:100, ultrasonicate at 40 kHz for 30 min, add modified polyacrylonitrile with a mass 20 times that of the modified silica, stir at 8 °C for 2 h at a stirring speed of 400 r / min, and ultrasonically defoam at 20 kHz for 30 min to obtain a spinning solution.

[0059] (9) Use a 20 mL syringe to suck up the spinning solution, extrude the spinning solution through a needle with an inner diameter of 0.5 mm at an extrusion speed of 0.42 mL / min. The extruded spinning solution enters the coagulation bath to obtain the nascent fiber. The coagulation bath is prepared by mixing N,N-dimethylformamide and water in a volume ratio of 1:1. The nascent fiber successively undergoes primary mechanical drawing, secondary mechanical drawing, and tertiary mechanical drawing and a drawing box to obtain the drawn fiber. The rotation speed of the primary drawing roller is 20 r / min, the rotation speed of the secondary drawing roller is 32 r / min, the rotation speed of the tertiary drawing roller is 36 r / min, and the temperature of the drawing box is 115 °C. Finally, the drawn fiber is collected on the winding roller, and the rotation speed of the winding roller is 38 r / min to obtain the modified polyacrylonitrile fiber;

[0060] (10) Weigh by mass parts: 9 parts of modified polyacrylonitrile, 60 parts of acetonitrile, 20 parts of acrylamide, 20 parts of ethylene glycol dimethacrylate, 8 parts of perfluorooctylethylene, and 3 parts of azobisisobutyronitrile. After mixing the modified polyacrylonitrile fiber and acetonitrile evenly, add acrylamide and stir for 1 h at a stirring speed of 200 r / min. Then add ethylene glycol dimethacrylate, perfluorooctylethylene, and azobisisobutyronitrile. Under nitrogen protection, react at 60 °C for 12 h. Filter by suction and wash 3 times with pure water, and dry at 60 °C for 12 h to obtain the superhydrophobic and flame-retardant fiber.

[0061] Comparative Example 1

[0062] The preparation method of the superhydrophobic and flame-retardant fiber in Comparative Example 1 is different from that in Example 2 in that steps (3), (4), and (5) are not carried out. Modify step (8) to mix modified silica and N,N-dimethylformamide at a mass-volume ratio of 3:100, ultrasonicate at 25 kHz for 35 min, add 15 times the mass of modified silica of melamine-modified polyacrylonitrile, stir at 5 °C for 2.5 h at a stirring speed of 500 r / min, and ultrasonically defoam at 30 kHz for 35 min to obtain the spinning solution.

[0063] Comparative Example 2

[0064] The preparation method of the superhydrophobic and flame-retardant fiber in Comparative Example 2 is different from that in Example 2 in that steps (4) and (5) are not carried out. Modify step (8) to mix modified silica and N,N-dimethylformamide at a mass-volume ratio of 3:100, ultrasonicate at 25 kHz for 35 min, add 15 times the mass of modified silica of the modified polyacrylonitrile precursor, stir at 5 °C for 2.5 h at a stirring speed of 500 r / min, and ultrasonically defoam at 30 kHz for 35 min to obtain the spinning solution.

[0065] Comparative Example 3

[0066] The preparation method of the superhydrophobic flame-retardant fiber of Comparative Example 3 is different from that of Example 2 in that steps (6) and (7) are not carried out, and step (8) is modified to mix modified polyacrylonitrile and N,N-dimethylformamide at a mass-volume ratio of 45:100, ultrasonicate for 35 min at 25 kHz, stir at 5 °C for 2.5 h, with a stirring speed of 500 r / min, and ultrasonically defoam for 35 min at 30 kHz to obtain a spinning solution.

[0067] Comparative Example 4

[0068] The preparation method of the superhydrophobic flame-retardant fiber of Comparative Example 4 is different from that of Example 2 in that step (10) is not carried out, and step (9) is modified to suck the spinning solution with a 20 mL syringe, extrude the spinning solution through a needle with an inner diameter of 0.5 mm at an extrusion speed of 0.40 mL / min, and the extruded spinning solution enters the coagulating liquid to obtain nascent fibers. The coagulating liquid is prepared by mixing N,N-dimethylformamide and water at a volume ratio of 1:1. The nascent fibers are successively subjected to one-stage mechanical drawing, two-stage mechanical drawing, three-stage mechanical drawing and a drawing box to obtain drawn fibers. The rotation speed of the first drawing roller is 20 r / min, the rotation speed of the second drawing roller is 32 r / min, the rotation speed of the third drawing roller is 36 r / min, and the temperature of the drawing box is 115 °C. Finally, the drawn fibers are collected on a winding roller with a winding roller rotation speed of 38 r / min to obtain superhydrophobic flame-retardant fibers.

[0069] Test Example 1

[0070] Test of flame retardancy

[0071] According to the GB / T5454 standard, the superhydrophobic flame-retardant fibers prepared in each example and comparative example were woven into fabrics and made into specimens, and the limiting oxygen index of the specimens was tested using a ZR-01 type limiting oxygen index instrument. The results are shown in Table 1.

[0072] Table 1

[0073]

[0074] From the comparison of the experimental data of Examples 1-3 and Comparative Examples 1-4 in Table 1, it can be found that the superhydrophobic flame-retardant fibers prepared by the present invention have good flame retardancy.

[0075] By comparison, the limiting oxygen index of Examples 1-3 is greater than that of Comparative Example 1, indicating that using sodium hydroxide to pretreat polyacrylonitrile is to carry out alkaline hydrolysis on polyacrylonitrile, convert the cyano group in polypropylene into a carboxyl group, provide active sites for subsequent functional modification, and then condense the amino group of melamine and the carboxyl group on polyacrylonitrile to introduce a nitrogen-based flame retardant on the surface of polyacrylonitrile. Then, reacting diallyl chlorophosphite with the amino group of melamine to form a phosphorus-nitrogen-based flame retardant provides good flame retardancy for polyacrylonitrile.

[0076] Test Example 2

[0077] Test of Hydrophobic Property

[0078] The superhydrophobic flame-retardant fibers prepared in each example and comparative example were pasted on a glass slide and tested using a DSA20 contact angle tester. 5 μL of pure water was dropped onto the surface of the superhydrophobic flame-retardant fiber, and the test started after 60 s. Five points were measured, and the average value was calculated after reading the data. The results are shown in Table 2.

[0079] Table 2

[0080]

[0081] From the comparison of the experimental data of Examples 1-3 and Comparative Examples 1-4 in Table 2, it can be found that the superhydrophobic flame-retardant fibers prepared by the present invention have good hydrophobic properties.

[0082] By comparison, the contact angles of Examples 1-3 are greater than those of Comparative Examples 3 and 4, indicating that modified silica is obtained by reacting silica with tetramethylguanidinopropyltrimethoxysilane. Tetramethylguanidinopropyltrimethoxysilane reacts with the hydroxyl groups on the surface of silica to obtain hydrophobic silica; after the modified polyacrylonitrile and the modified silica undergo a neutralization reaction, there are still some unreacted salicylic acid structures on the modified polyacrylonitrile. Therefore, there are unreacted salicylic acid structures on the modified polypropylene fibers after spinning. The amide group in acrylamide forms a stable complex with the carboxyl group and phenolic hydroxyl group in salicylic acid through hydrogen bonding and electrostatic attraction. The ester group in ethylene glycol dimethacrylate can interact with acrylamide and salicylic acid. Azobisisobutyronitrile, as a free radical initiator, decomposes to generate free radicals, and these free radicals attack the unsaturated double bonds in acrylamide, ethylene glycol dimethacrylate, and perfluorooctylethylene, thereby initiating a polymerization reaction to fix perfluorooctylethylene with low surface energy on the fiber, further increasing the hydrophobic property of the fiber.

[0083] Test Example 3

[0084] Test of UV Resistance

[0085] The superhydrophobic flame-retardant fibers prepared in each example and comparative example were woven into plain fabrics on a weaving trolley with warp and weft densities of 107 threads per inch and 63 threads per inch, respectively. The UV transmittance of the plain fabrics was tested at 370 nm using a Varian Cary500 UV-visible integrating sphere spectrophotometer. The results are shown in Table 3.

[0086] Table 3

[0087]

[0088] From the comparison of the experimental data of Examples 1-3 and Comparative Examples 1-4 in Table 3, it can be found that the superhydrophobic flame-retardant fibers prepared by the present invention have good ultraviolet resistance.

[0089] By comparison, the ultraviolet transmittance of Examples 1-3 is less than that of Comparative Examples 1-3, indicating that alkaline hydrolysis of polyacrylonitrile with sodium hydroxide converts the cyano group in polypropylene into a carboxyl group, providing active sites for subsequent functional modification. Subsequently, the amino group of melamine and the carboxyl group on polyacrylonitrile undergo a condensation reaction, and then diallyl chlorophosphite reacts with the amino group of melamine to introduce double bonds simultaneously. Using the thiol-ene click reaction between the thiol group of 5-mercapto salicylic acid and the double bond, a salicylic acid structure is introduced. The carbonyl group and hydroxyl group in the salicylic acid structure can form an intramolecular hydrogen bond to form a chelating ring. After absorbing the ultraviolet light energy, molecular thermal vibration occurs, the intramolecular hydrogen bond is broken, and the chelating ring opens to release the ultraviolet light energy as heat energy, thereby endowing the fibers prepared by the present invention with the ability to resist ultraviolet rays.

[0090] Test Example 4

[0091] Testing of antibacterial properties

[0092] Using the oscillation method in GB / T20944.3-2008 "Evaluation of Antibacterial Properties of Textiles", the antibacterial properties of the superhydrophobic flame-retardant fibers prepared in each example and comparative example were tested. The results are shown in Table 4.

[0093] Table 4

[0094]

[0095] From the comparison of the experimental data of Examples 1-3 and Comparative Examples 1-4 in Table 4, it can be found that the superhydrophobic flame-retardant fibers prepared by the present invention have good antibacterial properties.

[0096] By comparison, the antibacterial rate of Examples 1-3 can be greater than that of Comparative Example 3, indicating that modified silica is prepared by reacting silica with tetramethylguanidinopropyltrimethoxysilane. Tetramethylguanidinopropyltrimethoxysilane reacts with the hydroxyl groups on the silica surface to introduce guanidyl groups with antibacterial effects on the silica surface, endowing the silica with certain antibacterial properties, and thus endowing the fibers prepared by the present invention with antibacterial ability; finally, the modified polyacrylonitrile and modified silica are wet-spun to obtain modified polyacrylonitrile fibers, and the superhydrophobic flame-retardant fibers are prepared by finishing with acrylamide and perfluorooctylethylene. The modified polyacrylonitrile with a salicylic acid structure and the modified silica with guanidyl groups can undergo a neutralization reaction through simple blending to obtain a quaternary ammonium salt spinning solution, and the fibers prepared from this spinning solution can further improve the antibacterial properties.

[0097] It is obvious to those skilled in the art that the present invention is not limited to the details of the above-described exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention. Any reference signs in the claims should not be construed as limiting the claim concerned.

Claims

1. A method for preparing a super hydrophobic flame retardant fiber, characterized in that: The method comprises the following preparation steps: (1) Polyacrylonitrile, sodium hydroxide and water are mixed evenly in a mass ratio of 1:8-15:100-150, stirred at 60°C for 1-2h, the stirring speed is 200r / min, filtered and washed with pure water for 3-4 times, dried in a vacuum drying oven for 6-8h, the vacuum degree of the vacuum drying oven is 0.08MPa, the temperature is 50°C, and pretreated polyacrylonitrile is obtained; pretreated polyacrylonitrile, melamine, N,N-dicyclohexylcarbodiimide, N,N-dimethylformamide, and boric acid are mixed evenly in a mass ratio of 1:1-2:0.5-0.8:100-120:0.1-0.2, reacted at 60°C for 4h, cooled to room temperature, added dichloromethane 100-120 times the mass of the pretreated polyacrylonitrile, filtered and washed with pure water for 3-4 times, dried at 60°C for 12-14h, and melamine-modified polyacrylonitrile is obtained; (2) Mix melamine-modified polyacrylonitrile, acetonitrile and triethylamine in a mass ratio of 1:20-30:0.1-0.3 to obtain solution A; prepare diallyl chlorophosphite with acetonitrile to prepare solution B with a concentration of 2-3 g / mL; add solution B (0.02-0.04 times the volume of solution A) dropwise to solution A at 80°C at a rate of 0.25 mL / min. After the addition is completed, continue the reaction for 6-8 hours, add dichloromethane (40-50 times the mass of the melamine-modified polyacrylonitrile), filter and wash with pure water for 3-4 times, and dry at 60°C for 12-14 hours to obtain a modified polyacrylonitrile precursor; (3) The modified polyacrylonitrile precursor, 5-mercaptosalicylic acid, and N,N-dimethylformamide are mixed uniformly in a mass ratio of 1:2-3:20-30, 0.1-0.3 times the mass of the modified polyacrylonitrile precursor of 2,2-dimethoxy-2-phenylacetophenone is added, ultrasonication is performed at 20-40kHz for 20-30 minutes, ultraviolet light is irradiated at room temperature for 30 minutes, and the ultraviolet light power is 500W. Then, 40-50 times the mass of the modified polyacrylonitrile precursor of dichloromethane is added, the mixture is filtered and washed with pure water for 3-4 times, and dried at 60°C for 12-14 hours to obtain modified polyacrylonitrile; (4) Mix silica and anhydrous ethanol in a mass ratio of 1:20-30, disperse them ultrasonically at 20-40kHz for 20-30min, add a mixed solution of tetramethylguanidinopropyltrimethoxysilane in an equal volume to anhydrous ethanol, stir at 60-80°C for 4h at a stirring speed of 400-500r / min, filter after stirring, wash with pure water for 5-7 times, and dry at 60°C for 6-8h to obtain modified silica; (5) Mixing modified silica and N,N-dimethylformamide in a mass-to-volume ratio of 1-5:100, ultrasonically treating at 20-40 kHz for 30-40 min, adding modified polyacrylonitrile in an amount 10-20 times the mass of the modified silica, stirring at 5-10° C. for 2-3 h at a stirring speed of 400-600 r / min, and ultrasonically defoaming at 20-40 kHz for 30-40 min to obtain a spinning solution; (6) sucking the spinning solution with a syringe, squeezing the spinning solution out through a needle, the extruded spinning solution enters a coagulation liquid to obtain primary fibers, the primary fibers are sequentially subjected to a first mechanical draft, a second mechanical draft, a third mechanical draft and a drafting box to obtain stretched fibers, and finally, the stretched fibers are collected on a winding roller to obtain modified polyacrylonitrile fibers; (7) After the modified polyacrylonitrile fiber and acetonitrile are evenly mixed, acrylamide is added and stirred for 1-2 hours at a stirring speed of 200-300 r / min, ethylene glycol dimethacrylate, perfluorooctylethylene and azobisisobutyronitrile are added, and the mixture is reacted at 60°C under nitrogen protection for 12-14 hours. The mixture is filtered and washed with pure water for 3-4 times, and dried at 60°C for 12-14 hours to obtain a super hydrophobic flame retardant fiber.

2. The method for preparing a super hydrophobic flame retardant fiber according to claim 1, characterized in that: The molecular weight of the polyacrylonitrile in step (1) is 53,000.

3. The method for preparing a super hydrophobic flame retardant fiber according to claim 1, characterized in that: The preparation method of 5-mercaptosalicylic acid in step (3) is as follows: 5-(sulfonyl chloride)salicylic acid, tin particles, and concentrated hydrochloric acid are stirred at a mass ratio of 1:3-5:20-30 for 14-16 hours at a stirring speed of 200-300 r / min, cooled to room temperature, filtered, and an equal volume of ether to the concentrated hydrochloric acid is added, filtered again, and the filtrate is taken. The ether is removed by vacuum distillation of the filtrate, and 5-mercaptosalicylic acid is obtained by recrystallization with ethanol water. The purity of the tin particles is greater than 99.99%, and the particle size is 2-4 mm.

4. The method for preparing a super hydrophobic flame retardant fiber according to claim 1, characterized in that: The silicon dioxide model in step (4) is HN-SP1, with a content greater than 99.5%, a particle size of 30 nm, and a specific surface area of ​​640 m 2 / g.

5. The method for preparing a super hydrophobic flame retardant fiber according to claim 1, characterized in that: The preparation method of the tetramethylguanidinopropyltrimethoxysilane mixed solution in step (4) is to use glacial acetic acid to adjust the pH of 50wt% ethanol aqueous solution to 3.5-4.5, add tetramethylguanidinopropyltrimethoxysilane and mix evenly, wherein the mass volume ratio of tetramethylguanidinopropyltrimethoxysilane to 50wt% ethanol aqueous solution is 7-9:

100.

6. The method for preparing a super hydrophobic flame retardant fiber according to claim 1, characterized in that: The syringe specification of step (6) is 20 mL, the inner diameter of the needle is 0.5 mm, the extrusion speed is 0.38-0.42 mL / min, the coagulation liquid is a mixture of N,N-dimethylformamide and water in a volume ratio of 1:1, the speed of the first stretching roller is 20 r / min, the speed of the second stretching roller is 32 r / min, the speed of the third stretching roller is 36 r / min, the temperature of the stretching box is 115°C, and the speed of the winding roller is 38 r / min.

7. The method for preparing a super hydrophobic flame retardant fiber according to claim 1, characterized in that: The amounts of modified polyacrylonitrile, acetonitrile, acrylamide, ethylene glycol dimethacrylate, perfluorooctylethylene, and azobisisobutyronitrile used in step (7) are as follows, by mass: 7-9 parts of modified polyacrylonitrile, 50-60 parts of acetonitrile, 10-20 parts of acrylamide, 10-20 parts of ethylene glycol dimethacrylate, 7-8 parts of perfluorooctylethylene, and 1-3 parts of azobisisobutyronitrile.

8. A super-hydrophobic flame-retardant fiber prepared according to the method for preparing super-hydrophobic flame-retardant fiber according to any one of claims 1 to 7.

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