Flame-retardant cotton fiber and preparation method thereof

Abstract

The invention discloses a flame-retardant cotton fiber and a preparation method thereof, and relates to the field of cotton fibers. When the flame-retardant cotton fiber is prepared, dicarboxyl phenyl porphyrin and copper nitrate react to prepare a metal organic framework nanosheet; the preparation method comprises the following steps: reacting 2, 4, 6-tri (4-formyl phenyl)-1, 3, 5-triazine, 2-aminomethyl piperazine and phosphorous acid to prepare a flame-retardant graft; the cotton balls, the metal organic framework nanosheets and the flame-retardant graft react to prepare pre-modified cotton fibers; and carrying out ring-opening reaction on the pre-modified cotton fiber and epoxy chloropropane, and then carrying out ring-closing to obtain the flame-retardant cotton fiber. The flame-retardant cotton fiber prepared by the invention has excellent antibacterial property, flame retardance, color fixation and dispersity.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of cotton fibers, in particular to a flame-retardant cotton fiber and a preparation method thereof. BACKGROUND

[0002] Cotton is the main fiber in the 20th century, and its yield is only second to polyester. Cotton cloth is widely available, can be mass-produced, and is comfortable to wear, soft to the touch, and has good moisture permeability and air permeability. Therefore, it is the most popular textile at present. However, cotton fiber is highly flammable, with an oxygen index of only about 18% and an ignition temperature of about 350℃, and its flammability is much higher than that of other textile materials. Therefore, flame-retardant treatment of cotton fiber to delay ignition and prevent flame spread is a necessary measure to reduce fire risk.

[0003] In recent years, domestic and foreign scholars have conducted extensive research on the flame retardation of cotton fabrics, and have developed various types of cotton flame retardants. Early halogen flame retardants produce dioxins, furans and other carcinogens during combustion, which greatly limits their application in various fields. In the past decade, the synthesis of nitrogen-containing heteroatom organic phosphorus compounds and their application as flame retardants have received widespread attention from academia and industry. Such compounds are relatively easy to synthesize, have high thermal stability, are conducive to high-temperature processing, improve the stability of carbon, density and residual carbon content of polymers during thermal decomposition, and release active phosphorus during flame retardation. Therefore, the present application prepares a cotton fiber with excellent flame retardant properties. SUMMARY

[0004] The present application aims to provide a flame-retardant cotton fiber and a preparation method thereof to solve the problems in the prior art.

[0005] In order to solve the above technical problems, the present application provides the following technical solutions:

[0006] A flame-retardant cotton fiber, which is obtained by ring-closing the ring-opening reaction of a pre-modified cotton fiber and epichlorohydrin.

[0007] As an optimization, the pre-modified cotton fiber is prepared by reacting cotton balls, metal-organic framework nanosheets and flame-retardant grafts.

[0008] As an optimization, the cotton balls are from Shandong Xuzheng Textile Co., Ltd.

[0009] As an optimization, the metal-organic framework nanosheets are prepared by reacting dicarboxyphenyl porphyrin and copper nitrate.

[0010] As an optimization, the flame-retardant grafts are prepared by reacting 2,4,6-tris(4-formylphenyl)-1,3,5-triazine, 2-aminomethylpiperazine and phosphorous acid.

[0011] A preparation method of a flame-retardant cotton fiber, comprising the following preparation steps:

[0012] (1) mixing dicarboxyphenyl porphyrin, polyvinylpyrrolidone, anhydrous ethanol and N,N-dimethylformamide in a mass ratio of 1:(20-30):(100-300):(500-700), ultrasonicating for 5-15 min at 20-30 DEG C, stirring for 25-35 min at 300-400 rpm, adding copper nitrate in an amount of 0.8-1.0 times the mass of the dicarboxyphenyl porphyrin, continuing to stir for 1-3 min, centrifuging after heating for 23-25 h at 75-85 DEG C, washing with deionized water and anhydrous ethanol for 3-5 times respectively, and drying for 11-13 h at 50-60 DEG C to obtain metal-organic framework nanosheets;

[0013] (2) mixing 2,4,6-tris(4-formylphenyl)-1,3,5-triazine, 2-aminomethylpiperazine and 1,4-dioxane in a mass ratio of 1:(0.85-0.95):(15-25), stirring for 2-4 h at 75-85 DEG C under nitrogen atmosphere and at 100-300 rpm, naturally cooling to room temperature, adding phosphorous acid in an amount of 1.05-1.07 times the mass of the 2,4,6-tris(4-formylphenyl)-1,3,5-triazine, continuing to stir for 11-13 h after heating to 50-60 DEG C, pouring into ice water and standing, then suction filtering, washing with anhydrous ethanol and dichloromethane for 3-5 times respectively, and drying for 23-25 h at 70-80 DEG C to obtain a flame-retardant grafting product;

[0014] (3) mixing a cotton group, 4-dimethylaminopyridine and deionized water in a mass ratio of 1:(0.01-0.03):(15-25), ultrasonicating for 20-30 min at 20-30 DEG C, adding the flame-retardant grafting product in an amount of 0.7-0.9 times the mass of the cotton group and the metal-organic framework nanosheets in an amount of 0.03-0.05 times the mass of the cotton group, continuing to ultrasonicate for 0.5-1.5 h, filtering, washing with anhydrous ethanol and deionized water for 3-5 times respectively, and drying for 11-13 h at 50-60 DEG C to obtain a pre-modified cotton fiber;

[0015] (4) mixing the pre-modified cotton fiber, epichlorohydrin and anhydrous ethanol in a mass ratio of 1:(0.4-0.5):(10-20), stirring for 3-5 h at 60-70 DEG C and at 200-400 rpm, filtering, washing with anhydrous ethanol for 3-5 times, and drying for 7-9 h at 55-65 DEG C to obtain a modified cotton fiber; immersing the modified cotton fiber in a 0.05-0.15 mol / L sodium hydroxide solution, ultrasonicating for 10-30 min at 25-35 DEG C, filtering, standing for 1-3 h, washing with deionized water for 3-5 times, and drying for 7-9 h at 60-70 DEG C to obtain a flame-retardant cotton fiber.

[0016] As optimization, the reaction equation of the metal organic framework nanosheet in step (1) is:

[0017]

[0018] As optimization, the reaction equation of the flame-retardant graft in step (2) is:

[0019]

[0020] As optimization, the reaction equation of the pre-modified cotton fiber in step (3) is:

[0021]

[0022] As optimization, the reaction equation of the flame-retardant cotton fiber in step (4) is:

[0023]

[0024] Compared with the prior art, the beneficial effects achieved by the present application are:

[0025] In the preparation of the flame-retardant cotton fiber, the present application reacts dicarboxyphenyl porphyrin and copper nitrate to obtain a metal organic framework nanosheet; reacts 2,4,6-tris(4-formylphenyl)-1,3,5-triazine, 2-aminomethyl piperazine and phosphorous acid to obtain a flame-retardant graft; reacts a cotton group, the metal organic framework nanosheet and the flame-retardant graft to obtain a pre-modified cotton fiber; and after ring-opening reaction of the pre-modified cotton fiber and epichlorohydrin, the flame-retardant cotton fiber is obtained by ring closure.

[0026] First, dicarboxyphenyl porphyrin and copper nitrate are reacted to obtain a metal organic framework nanosheet; 2,4,6-tris(4-formylphenyl)-1,3,5-triazine, 2-aminomethyl piperazine and phosphorous acid are reacted to obtain a flame-retardant graft; by releasing copper ions, the bacterial cell membrane is destroyed, and porphyrin can produce active oxygen under visible light irradiation to directly oxidize bacteria, thereby improving the antibacterial property of the flame-retardant cotton fiber; at the same time, the metal organic framework can also enhance the dye adhesion by metal coordination and physical adsorption, thereby improving the color fastness of the flame-retardant cotton fiber; after Schiff base reaction of 2,4,6-tris(4-formylphenyl)-1,3,5-triazine and 2-aminomethyl piperazine, phosphorous acid is added to form a phosphorus-nitrogen synergistic flame-retardant structure, and phosphorous acid can capture free radicals generated in the combustion chain reaction, and piperazine and triazine ring can generate non-combustible gas under heating, thereby improving the flame-retardant property of the flame-retardant cotton fiber.

[0027] Secondly, the cotton, metal organic framework nanosheet and flame-retardant graft are reacted to obtain pre-modified cotton fibers; the pre-modified cotton fibers and epoxy chloropropane are reacted to obtain flame-retardant cotton fibers; 4-dimethylamino pyridine is used to catalyze the esterification reaction among the cotton, metal organic framework nanosheet and flame-retardant graft at room temperature, 4-dimethylamino pyridine can be selectively mono-esterified and the reaction can be carried out at room temperature, so as to avoid multi-functional group esterification crosslinking and reduce the occurrence of side reactions, and improve the dispersibility of the flame-retardant cotton fibers; the secondary amine on the piperazine ring is used as a reaction site to graft the epoxy chloropropane after ring closure, and a covalent bond is formed with the dye molecule, and the metal organic framework nanosheet is synergized to enhance the color fixation rate and improve the color fastness of the flame-retardant cotton fibers. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0029] The raw materials used in the following examples and comparative examples are all commercially available:

[0030] The cotton is from Shandong Xuzheng Textile Co., Ltd.

[0031] Example 1:

[0032] A preparation method of flame-retardant cotton fibers, the preparation method of the flame-retardant cotton fibers comprises the following preparation steps:

[0033] (1) Mix dicarboxyphenyl porphyrin, polyvinylpyrrolidone, anhydrous ethanol and N,N-dimethylformamide in a mass ratio of 1:20:100:500, ultrasonic at 20℃ for 5min, stir at 300rpm for 35min, add copper nitrate with a mass of 0.8 times that of dicarboxyphenyl porphyrin, continue to stir for 1min, heat at 75℃ for 25h, then centrifuge, wash with deionized water and anhydrous ethanol for 3 times respectively, and dry at 50℃ for 13h to obtain metal organic framework nanosheet;

[0034] (2) Mix 2,4,6-tris(4-formylphenyl)-1,3,5-triazine, 2-aminomethylpiperazine and 1,4-dioxane in a mass ratio of 1:0.85:15, stir at 100rpm for 4h in a nitrogen atmosphere at 75℃, naturally cool to room temperature, add phosphorous acid with a mass of 1.05 times that of 2,4,6-tris(4-formylphenyl)-1,3,5-triazine, continue to stir at 50℃ for 13h, pour into ice water, stand, then suction filter, wash with anhydrous ethanol and dichloromethane for 3 times respectively, and dry at 70℃ for 25h to obtain flame-retardant graft;

[0035] (3) Cotton balls, 4-dimethylaminopyridine and deionized water were mixed in a mass ratio of 1:0.01:15, and ultrasonically dispersed at 20°C for 30 min. Flame-retardant grafts (0.7 times the mass of the cotton balls) and metal organic framework nanosheets (0.03 to 1.5 times the mass of the cotton balls) were added. The mixture was ultrasonically dispersed for 1.5 h and then filtered. The mixture was washed with anhydrous ethanol and deionized water for 3 times, respectively, and dried at 50°C for 13 h to obtain pre-modified cotton fibers.

[0036] (4) The pre-modified cotton fiber, epichlorohydrin and anhydrous ethanol were mixed in a mass ratio of 1:0.4:10, stirred at 60°C and 200 rpm for 5 h, filtered, washed three times with anhydrous ethanol, and dried at 55°C for 9 h to obtain modified cotton fiber; the modified cotton fiber was immersed in 0.05 mol / L sodium hydroxide solution, ultrasonicated at 25°C for 30 min, filtered, allowed to stand for 1 h, washed three times with deionized water, and dried at 60°C for 9 h to obtain flame-retardant cotton fiber.

[0037] Example 2:

[0038] A method for preparing flame-retardant cotton fiber, comprising the following steps:

[0039] (1) Dicarboxyphenylporphyrin, polyvinylpyrrolidone, anhydrous ethanol and N,N-dimethylformamide were mixed in a mass ratio of 1:25:200:600, ultrasonicated at 25°C for 10 min, stirred at 350 rpm for 30 min, and copper nitrate (0.9 times the mass of dicarboxyphenylporphyrin) was added. The mixture was stirred for 2 min, heated at 80°C for 24 h, and then centrifuged. The mixture was washed with deionized water and anhydrous ethanol four times, respectively, and dried at 55°C for 12 h to obtain metal organic framework nanosheets.

[0040] (2) 2,4,6-tris(4-formylphenyl)-1,3,5-triazine, 2-aminomethylpiperazine and 1,4-dioxane were mixed in a mass ratio of 1:0.9:20, stirred at 80°C and 200 rpm for 3 h in a nitrogen atmosphere, cooled naturally to room temperature, added with phosphorous acid (1.06 times the mass of 2,4,6-tris(4-formylphenyl)-1,3,5-triazine), heated to 55°C and stirred for 12 h, poured into ice water, allowed to stand and then filtered, washed with anhydrous ethanol and dichloromethane four times respectively, and dried at 75°C for 24 h to obtain a flame retardant grafted product;

[0041] (3) Cotton balls, 4-dimethylaminopyridine, and deionized water were mixed in a mass ratio of 1:0.02:20, and ultrasonically dispersed at 25°C for 25 min. Flame-retardant grafts (0.8 times the mass of the cotton balls) and metal organic framework nanosheets (0.04 times the mass of the cotton balls) were added. Ultrasonication was continued for 1 h, and then filtered. The fibers were washed four times with anhydrous ethanol and deionized water, respectively, and dried at 55°C for 12 h to obtain pre-modified cotton fibers.

[0042] (4) Pre-modified cotton fibers, epichlorohydrin and anhydrous ethanol were mixed in a mass ratio of 1:0.45:15, filtered after stirring at 65°C for 4h at 300rpm, washed with anhydrous ethanol for 4 times, and dried at 60°C for 8h to obtain modified cotton fibers; the modified cotton fibers were immersed in a 0.1 mol / L sodium hydroxide solution, filtered after ultrasonic treatment at 30°C for 20min, placed for 2h, washed with deionized water for 4 times, and dried at 65°C for 8h to obtain flame-retardant cotton fibers.

[0043] Example 3:

[0044] A preparation method of flame-retardant cotton fibers, the preparation method of flame-retardant cotton fibers comprising the following preparation steps:

[0045] (1) Carboxyphenyl porphyrin, polyvinylpyrrolidone, anhydrous ethanol and N,N-dimethylformamide were mixed in a mass ratio of 1:30:300:700, ultrasonic treated at 30°C for 5min, stirred at 400rpm for 25min, 1.0 times of copper nitrate of carboxyphenyl porphyrin was added, and the stirring was continued for 1min, centrifuged after heating at 85°C for 23h, washed with deionized water and anhydrous ethanol for 5 times respectively, and dried at 60°C for 11h to obtain metal-organic framework nanosheets;

[0046] (2) 2,4,6-tris(4-formylphenyl)-1,3,5-triazine, 2-aminomethylpiperazine and 1,4-dioxane were mixed in a mass ratio of 1:0.95:25, stirred at 85°C for 2h under nitrogen atmosphere at 300rpm, naturally cooled to room temperature, 1.07 times of phosphorous acid of 2,4,6-tris(4-formylphenyl)-1,3,5-triazine was added, and the stirring was continued at 60°C for 11h, poured into ice water and placed, then suction filtered, washed with anhydrous ethanol and dichloromethane for 5 times respectively, and dried at 80°C for 23h to obtain flame-retardant grafting;

[0047] (3) Cotton group, 4-dimethylaminopyridine and deionized water were mixed in a mass ratio of 1:0.03:25, ultrasonic dispersed at 30°C for 20min, 0.9 times of the flame-retardant grafting of the cotton group and 0.05 times of the metal-organic framework nanosheets of the cotton group were added, and the ultrasonic treatment was continued for 0.5h, then filtered, washed with anhydrous ethanol and deionized water for 5 times respectively, and dried at 60°C for 11h to obtain pre-modified cotton fibers;

[0048] (4) The pre-modified cotton fiber, epichlorohydrin and anhydrous ethanol were mixed in a mass ratio of 1:0.5:20, filtered after stirring at 70°C and 400 rpm for 3h, washed with anhydrous ethanol for 5 times, and dried at 65°C for 7h to obtain modified cotton fiber; the modified cotton fiber was immersed in a 0.15 mol / L sodium hydroxide solution, filtered after ultrasonic treatment at 35°C for 10 min, washed with deionized water for 5 times, and dried at 70°C for 7h to obtain the flame-retardant cotton fiber.

[0049] Comparative Example 1:

[0050] The preparation method of the flame-retardant cotton fiber of Comparative Example 1 is different from that of Example 2 only in step (3), wherein the 4-dimethylaminopyridine in step (3) is modified to: sulfuric chloride. The remaining steps are the same as those of Example 2.

[0051] Comparative Example 2:

[0052] The preparation method of the flame-retardant cotton fiber of Comparative Example 2 is different from that of Example 2 only in step (3), wherein the 4-dimethylaminopyridine in step (3) is modified to: p-toluenesulfonic acid. The remaining steps are the same as those of Example 2.

[0053] Comparative Example 3:

[0054] The preparation method of the flame-retardant cotton fiber of Comparative Example 3 is different from that of Example 2 only in step (3), wherein the reaction temperature in step (3) is modified to: 40°C. The remaining steps are the same as those of Example 2.

[0055] Comparative Example 4:

[0056] The preparation method of the flame-retardant cotton fiber of Comparative Example 4 is different from that of Example 2 only in step (3), wherein the reaction temperature in step (3) is modified to: 60°C. The remaining steps are the same as those of Example 2.

[0057] Comparative Example 5:

[0058] The preparation method of the flame-retardant cotton fiber of Comparative Example 5 is different from that of Example 2 only in step (3), wherein the reaction time in step (3) is modified to: 2h. The remaining steps are the same as those of Example 2.

[0059] Comparative Example 6:

[0060] The preparation method of the flame-retardant cotton fiber of Comparative Example 6 is different from that of Example 2 only in step (3), wherein the reaction time in step (3) is modified to: 3h. The remaining steps are the same as those of Example 2.

[0061] Comparative Example 7:

[0062] The preparation method of the flame-retardant cotton fiber of Comparative Example 7 is only different from that of Example 2 in steps (1), (3), and step (1) is omitted. Step (3) is modified as follows: the cotton group, 4-dimethylaminopyridine, and deionized water are uniformly mixed in a mass ratio of 1:0.02:20, ultrasonic dispersion is performed at 25°C for 25 min, 0.8 times the mass of the cotton group of the flame-retardant grafting agent is added, ultrasonic dispersion is continued for 1 h, then filtration is performed, and the flame-retardant cotton fiber is obtained by washing with anhydrous ethanol and deionized water 4 times each and drying at 55°C for 12 h. The remaining steps are the same as in Example 2.

[0063] Comparative Example 8:

[0064] The preparation method of the flame-retardant cotton fiber of Comparative Example 8 is only different from that of Example 2 in steps (3), (4), and step (4) is omitted. Step (3) is modified as follows: the cotton group, 4-dimethylaminopyridine, and deionized water are uniformly mixed in a mass ratio of 1:0.02:20, ultrasonic dispersion is performed at 25°C for 25 min, 0.8 times the mass of the cotton group of the flame-retardant grafting agent and 0.04 times the mass of the cotton group of the metal-organic framework nanosheet are added, ultrasonic dispersion is continued for 1 h, then filtration is performed, and the flame-retardant cotton fiber is obtained by washing with anhydrous ethanol and deionized water 4 times each and drying at 55°C for 12 h. The remaining steps are the same as in Example 2.

[0065] Comparative Example 9:

[0066] The preparation method of the flame-retardant cotton fiber of Comparative Example 9 is only different from that of Example 2 in steps (2), (3), (4), and steps (2), (4) are omitted. Step (3) is modified as follows: the cotton group, 4-dimethylaminopyridine, and deionized water are uniformly mixed in a mass ratio of 1:0.02:20, ultrasonic dispersion is performed at 25°C for 25 min, 0.04 times the mass of the cotton group of the metal-organic framework nanosheet is added, ultrasonic dispersion is continued for 1 h, then filtration is performed, and the flame-retardant cotton fiber is obtained by washing with anhydrous ethanol and deionized water 4 times each and drying at 55°C for 12 h. The remaining steps are the same as in Example 2.

[0067] Test Example 1:

[0068] 1. Dispersion

[0069] Test method: the flame-retardant cotton fiber obtained in each example and comparative example and deionized water are uniformly mixed in a mass ratio of 1:5, and stirring is performed 30 times alternately clockwise and counterclockwise, and the dispersion is observed and recorded.

[0070] 2. Grafting rate

[0071] Test method: the cotton group (m0) and the obtained pre-modified cotton fiber (m1) used in each example and comparative example are weighed, and the grafting rate is calculated as (m1-m0) / m0*100%.

[0072] The following Table 1 shows the analysis results of the dispersibility of the flame-retardant cotton fibers prepared by using the embodiment 2 and the comparative examples 1-6 of the present application.

[0073] Table 1

[0074] Catalyst Temperature °C Time h Dispersibility Grafting % Example 2 4-dimethylamino pyridine 25 1 Uniformly dispersed 48 Comparative Example 1 Thionyl chloride 25 1 / 23 Comparative Example 2 p-toluenesulfonic acid 25 1 / 12 Comparative Example 3 4-dimethylamino pyridine 40 1 Partially agglomerated 54 Comparative Example 4 4-dimethylamino pyridine 60 1 Mostly agglomerated 61 Comparative Example 5 4-dimethylamino pyridine 25 2 Partially agglomerated 58 Comparative Example 6 4-dimethylamino pyridine 25 3 Mostly agglomerated 63

[0075] From the comparison of the experimental data of the embodiment 2 and the comparative examples 1-6 in Table 1, it can be found that the flame-retardant cotton fibers prepared by the present application have good dispersibility.

[0076] Through comparison, the dispersibility and grafting rate of the embodiment 1, 2, 3 and the comparative examples 1-6 show that the esterification reaction between the cotton group, the metal-organic framework nanosheet and the flame-retardant grafting material is catalyzed by 4-dimethylaminopyridine at room temperature, 4-dimethylaminopyridine can be selectively mono-esterified and can be carried out at room temperature, which avoids the crosslinking esterification of multi-functional groups and reduces the occurrence of side reactions, thereby improving the dispersibility of the flame-retardant cotton fibers.

[0077] Test Example 2:

[0078] 1. Flame Retardancy

[0079] Test Method: The flame-retardant cotton fibers obtained in each example and comparative example were tested for limiting oxygen index according to GB / T5454.

[0080] 2. Antibacterial Property

[0081] Test Method: The flame-retardant cotton fibers obtained in each example and comparative example were cut into test samples with a diameter of 25 mm according to GB / T20944, 10 mL of sterilized nutrient agar was poured into a sterile culture dish as the lower sterile culture medium, 1 mL of Staphylococcus aureus liquid with a concentration of 5×10 8 CFU / mL was added to 150 mL of agar medium at 45℃, and after uniform shaking, 5 mL was poured into a sterile culture dish as the upper inoculum medium, the test sample was placed on the two layers of medium, and was gently pressed with tweezers, and was incubated at 37℃ for 24 h, and the width of the inhibition zone was measured.

[0082] 3. Dyeing Property

[0083] Test Method: The flame-retardant cotton fibers obtained in each example and comparative example were dyed with reactive black 5 dye according to GB / T3921, and the water washing fastness grade was tested.

[0084] The following Table 2 shows the analysis results of the antibacterial, flame-retardant and color fixing properties of the flame-retardant cotton fibers prepared by using the embodiments 1-3 and the comparative examples 7-9 of the present application.

[0085] Table 2

[0086]

[0087]

[0088] From the experimental data comparison of examples 1-3 and comparative examples 7-9 in table 2, it can be found that the flame-retardant cotton fibers prepared by the present application have good antibacterial, flame-retardant and color fixing properties.

[0089] Comparative example 7 does not graft metal organic framework nanosheets; by comparison, the bacteriostatic ring width of examples 1, 2, 3 is large, and the color fastness grade is high, which shows that the release of copper ions can destroy the bacterial cell membrane, and porphyrin can produce active oxygen under visible light irradiation to directly oxidize bacteria and improve the antibacterial property of the flame-retardant cotton fibers; at the same time, the metal organic framework can also enhance the dye adhesion through metal coordination and physical adsorption, and improve the color fastness of the flame-retardant cotton fibers.

[0090] Comparative example 8 does not graft the ring-closing after the ring-opening of epichlorohydrin; by comparison, the color fastness grade of examples 1, 2, 3 is high, which shows that the secondary amine on the piperazine ring is used as a reaction site to graft the ring-closing after the ring-opening of epichlorohydrin, and a covalent bond is formed with the dye molecule, which cooperates with the metal organic framework nanosheet to enhance the color fixing rate and improve the color fastness of the flame-retardant cotton fibers.

[0091] Comparative example 9 does not graft the flame-retardant grafting material; by comparison, the limiting oxygen index and color fastness grade of examples 1, 2, 3 are high, which shows that the Schiff base reaction is carried out after 2,4,6-tris(4-formylphenyl)-1,3,5-triazine and 2-aminomethyl piperazine, and then phosphorous acid is added, forming a phosphorus-nitrogen synergistic flame-retardant structure, and the phosphorous acid can capture free radicals generated by combustion chain reaction, and the piperazine and triazine rings can generate non-combustible gas under heat, improving the flame-retardant property of the flame-retardant cotton fibers; at the same time, the secondary amine on the piperazine ring can be used as a reaction site to graft the ring-closing after the ring-opening of epichlorohydrin, and a covalent bond is formed with the dye molecule, which cooperates with the metal organic framework nanosheet to enhance the color fixing rate and improve the color fastness of the flame-retardant cotton fibers.

[0092] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present application, and it should be understood that the above description is only a specific embodiment of the present application and is not used to limit the protection scope of the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A flame-retardant cotton fiber, characterized by, The flame-retardant cotton fiber is obtained by ring closing after opening ring of pre-modified cotton fiber and epichlorohydrin; The pre-modified cotton fiber is prepared by reaction of cotton group, metal organic framework nanosheet and flame-retardant grafting. The metal organic framework nanosheet is prepared by reaction of dicarboxyphenyl porphyrin and copper nitrate. The flame-retardant grafting is prepared by reaction of 2,4,6-tris(4-formylphenyl)-1,3,5-triazine, 2-aminomethyl piperazine and phosphorous acid.

2. A method for producing a flame-retardant cotton fiber, characterized by, The preparation process comprises the following steps: (1) mixing dicarboxyphenyl porphyrin, polyvinylpyrrolidone, anhydrous ethanol and N,N-dimethylformamide, adding copper nitrate, washing and drying to obtain metal organic framework nanosheet; (2) mixing 2,4,6-tris(4-formylphenyl)-1,3,5-triazine, 2-aminomethyl piperazine and 1,4-dioxane, reacting, adding phosphorous acid for further reaction, pouring into ice water, standing, then filtering, washing and drying to obtain flame-retardant grafting; (3) mixing cotton group, 4-dimethylaminopyridine and deionized water, ultrasonic dispersion, adding flame-retardant grafting and metal organic framework nanosheet, continuing ultrasonic, then filtering, washing and drying to obtain pre-modified cotton fiber; (4) mixing pre-modified cotton fiber, epichlorohydrin and anhydrous ethanol, reacting to obtain modified cotton fiber; The modified cotton fiber is immersed in sodium hydroxide solution, filtered after ultrasonic, standing, washing and drying to obtain flame-retardant cotton fiber.

3. The method of claim 2, wherein the flame-retardant cotton fiber is prepared by adding the flame-retardant agent to the cotton fiber. The preparation process of the metal organic framework nanosheet in step (1) is as follows: mixing dicarboxyphenyl porphyrin, polyvinylpyrrolidone, anhydrous ethanol and N,N-dimethylformamide according to mass ratio 1:(20-30):(100-300):(500-700), ultrasonic for 5-15 min at 20-30℃, stirring for 25-35 min at 300-400 rpm, adding copper nitrate with mass 0.8-1.0 times of dicarboxyphenyl porphyrin, continuing stirring for 1-3 min, heating for 23-25 h at 75-85℃, then centrifuging, washing with deionized water and anhydrous ethanol for 3-5 times respectively.

4. The method of claim 2, wherein the flame-retardant cotton fiber is prepared by adding the flame-retardant agent to the cotton fiber. The preparation process of the flame-retardant grafting in step (2) is as follows: mixing 2,4,6-tris(4-formylphenyl)-1,3,5-triazine, 2-aminomethyl piperazine and 1,4-dioxane according to mass ratio 1:(0.85-0.95):(15-25), stirring for 2-4 h at 75-85℃ under nitrogen atmosphere and at 100-300 rpm, naturally cooling to room temperature, adding phosphorous acid with mass 1.05-1.07 times of 2,4,6-tris(4-formylphenyl)-1,3,5-triazine, heating to 50-60℃ for continuing stirring for 11-13 h, pouring into ice water, standing, then filtering, washing with anhydrous ethanol and dichloromethane for 3-5 times respectively, drying at 70-80℃ for 23-25 h.

5. The method of claim 2, wherein the flame-retardant cotton fiber is prepared by adding the flame-retardant agent to the cotton fiber. The preparation process of the pre-modified cotton fiber in step (3) is as follows: mixing the cotton group, 4-dimethylaminopyridine and deionized water according to the mass ratio of 1:(0.01-0.03):(15-25), ultrasonic dispersion at 20-30 DEG C for 20-30 min, adding 0.7-0.9 times the mass of the cotton group of the flame-retardant graft and 0.03-0.05 times the mass of the cotton group of the metal organic framework nanosheet, continuing ultrasonic for 0.5-1.5 h, filtering, washing with anhydrous ethanol and deionized water for 3-5 times, and drying at 50-60 DEG C for 11-13 h.

6. The method for preparing flame-retardant cotton fiber according to claim 2, characterized in that: The preparation process of the flame-retardant cotton fiber in step (4) is as follows: immersing the modified cotton fiber in a sodium hydroxide solution, filtering after ultrasonic for 10-30 min at 25-35 DEG C, standing for 1-3 h, washing with deionized water for 3-5 times, and drying at 60-70 DEG C for 7-9 h. The preparation process of the modified cotton fiber is as follows: mixing the pre-modified cotton fiber, epichlorohydrin and anhydrous ethanol according to the mass ratio of 1:(0.4-0.5):(10-20), filtering after stirring at 60-70 DEG C and 200-400 rpm for 3-5 h, washing with anhydrous ethanol for 3-5 times, and drying at 55-65 DEG C for 7-9 h.

7. The method of claim 6, wherein the flame-retardant cotton fiber is prepared by adding the flame-retardant agent to the cotton fiber in the form of a solution, a suspension, or a dispersion. The concentration of the sodium hydroxide solution is 0.05-0.15 mol / L.

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