High-elasticity polyurethane flame-retardant fiber, preparation method and application of high-elasticity polyurethane flame-retardant fiber to telescopic electric wire

Abstract

The invention relates to the technical field of fibers, and discloses a high-elasticity polyurethane flame-retardant fiber, a preparation method and application of the high-elasticity polyurethane flame-retardant fiber to a telescopic electric wire. The preparation method comprises the following steps: by using 1, 1, 3, 3-tetramethyldisiloxane as a bridging agent through hydrosilylation reaction, connecting allyl modified DOPO with allyl phenoxy cyclotriphosphazene to prepare a flame retardant with three flame-retardant elements of phosphorus, nitrogen and silicon at the same time; the preparation method comprises the following steps: preparing a polyurethane urea solution by a method of adding 4, 4-diphenylmethane diisocyanate in batches, introducing a flame retardant, mixing the polyurethane urea solution with an antioxidant, a dyeing assistant and a delustering agent, and carrying out dry spinning to obtain the high-elasticity polyurethane flame-retardant fiber. The polyurethane fiber has excellent flame retardant property and heat resistance, and good mechanical property and resilience, and can be applied to telescopic electric wires.

Description

Technical Field

[0001] The present invention relates to the field of fiber technology, and in particular to a high-elasticity polyurethane flame-retardant fiber, a preparation method and application in telescopic wires. Background Art

[0002] Polyurethane elastic fiber, or spandex for short, is a multi-block copolymer with alternating soft and hard segments. Its unique structure gives it high resilience and low modulus. Industrialized spandex can be divided into melt-spun spandex and dry-spun spandex based on processing techniques, with dry-spun spandex offering superior performance. Traditional electrical wires use resin sheaths, which are prone to loosening and tangling in dynamic environments. The excellent elasticity of spandex fiber provides the foundation for controlled scalability in electrical wires.

[0003] Although polyurethane fibers possess various excellent properties, they are flammable, with a limiting oxygen index of only 17%. This flammability severely impacts the flame retardant properties of flame-retardant materials, thus limiting their application. Current methods for preparing flame-retardant fibers primarily include copolymerization, blending, composite spinning, grafting, and fabric finishing. The flame-retardant mechanisms of flame retardants are primarily categorized as gas-phase, condensed-phase, and synergistic. Prior art approaches achieve intrinsic flame retardancy in polyurethane fibers by constructing polyols, isocyanates, or chain extenders containing flame-retardant elements, allowing the flame-retardant elements to be incorporated into the polyurethane molecular structure through a reaction. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings of the existing technology and provide a high-elasticity polyurethane flame-retardant fiber, a preparation method and its application in telescopic wires. The polyurethane fiber has excellent flame retardant and heat resistance, as well as good mechanical properties and rebound ability, and can be used in telescopic wires.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows: A method for preparing a highly elastic polyurethane flame-retardant fiber comprises the following steps: Step (1), mixing and dissolving hexachlorocyclotriphosphazene, acetone, and a catalyst, potassium carbonate, adding an acetone solution of 2-allylphenol, reacting, and after the reaction is completed, purifying to obtain allylphenoxycyclotriphosphazene; Step (2), heating DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) until it melts, adding allyl glycidyl ether and catalyst triphenylphosphine, reacting, and cooling after the reaction to obtain allyl-modified DOPO; Allylphenoxy cyclotriphosphazene, Custer catalyst, and tetrahydrofuran were mixed, heated, and 1,1,3,3-tetramethyldisiloxane was added dropwise. After the addition was complete, the mixture was reacted. After the reaction was completed, allyl-modified DOPO was added and the reaction was continued. After the reaction was completed, the mixture was rotary evaporated to obtain a flame retardant. Step (3), reacting polytetramethylene glycol and the first portion of 4,4-diphenylmethane diisocyanate, and obtaining a prepolymer after the reaction is completed; mixing and dissolving the prepolymer and dimethylacetamide, adding the second portion of 4,4-diphenylmethane diisocyanate and mixing evenly, adding a flame retardant, and continuing the reaction. After the reaction is completed, cooling, adding a chain extender, and reacting again, and obtaining a polyurethane urea solution after the reaction is completed; Step (4): mixing the polyurethane urea solution with an antioxidant, a dyeing assistant, and a matting agent, and dry spinning the mixture to obtain a highly elastic polyurethane flame retardant fiber.

[0006] Preferably, in step (1), the molar ratio of hexachlorocyclotriphosphazene to 2-allylphenol is 1:6.5-7; the acetone solution of 2-allylphenol is prepared by mixing 2-allylphenol and acetone in a mass ratio of 1:5-6; and the mass ratio of hexachlorocyclotriphosphazene, acetone, and catalyst potassium carbonate is 17-18:180-200:82-83.

[0007] Preferably, in step (1), the reaction conditions are: reaction at 40-50°C for 12-15h.

[0008] Preferably, in step (1), the purification operation includes: cooling to room temperature after the reaction is completed, filtering, collecting the filtrate, and distilling under reduced pressure to remove the solvent acetone to obtain a crude reaction product, dissolving the crude reaction product with toluene, and sequentially adding 5wt% sodium hydroxide aqueous solution, 2wt% hydrochloric acid aqueous solution, and water to wash until neutral. After washing, adding anhydrous sodium sulfate to dry, filtering, collecting the filtrate, and distilling under reduced pressure to remove the solvent.

[0009] Preferably, in step (2), the molar ratio of DOPO to allyl glycidyl ether is 1:1-1.1; the amount of triphenylphosphine catalyst added is 0.5-0.8 wt% of the total mass of DOPO and allyl glycidyl ether; when preparing allyl-modified DOPO, the preparation reaction conditions are: reaction in a nitrogen atmosphere at 130° C. for 10-12 hours.

[0010] Preferably, in step (2), the mass ratio of allylphenoxy cyclotriphosphazene, 1,1,3,3-tetramethyldisiloxane, allyl-modified DOPO, Custer catalyst, and tetrahydrofuran is 93-95:82-84.5:192-208:3-3.5:3500-4000; when preparing the flame retardant, the reaction conditions are: reacting at a temperature of 60-70°C for 2-2.5h; and the continued reaction conditions are: continuing the reaction at a temperature of 65-75°C for 3-4h.

[0011] Preferably, in step (3), the mass ratio of polytetramethylene glycol, the first portion of 4,4-diphenylmethane diisocyanate, the second portion of 4,4-diphenylmethane diisocyanate, the chain extender, and the flame retardant is 340:75-80:23-25:80-90:50-60; The chain extender is prepared by mixing and dissolving ethylenediamine, propylenediamine, diethylamine and dimethylacetamide in a mass ratio of 5-5.1:3:0.5-0.6:90-100.

[0012] Preferably, in step (3), the reaction conditions are: reacting at 80-85°C for 2-2.5 hours; continuing the reaction conditions are: continuing the reaction at 70-75°C for 0.5 hours; and re-reacting conditions are: reacting again at 10°C for 0.5-1 hours.

[0013] Preferably, in step (3), the solid content of the polyurethane urea solution is 30-40 wt%.

[0014] Preferably, in step (4), the mass ratio of the polyurethane urea solution to the antioxidant, anti-yellowing agent, and matting agent is 1000:0.02-0.03:0.01-0.02:0.008-0.01; the spinning speed of the dry spinning is 800-900 m / min, and the spinning cylinder atmosphere temperature is 250-270°C.

[0015] Preferably, a high elasticity polyurethane flame retardant fiber is prepared by the preparation method of the high elasticity polyurethane flame retardant fiber as described above.

[0016] Preferably, the highly elastic polyurethane flame-retardant fiber as described above is used in telescopic wires.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The invention introduces a flame retardant into the polyurethane urea spinning solution and adopts a preparation method of secondary addition of isocyanate, thereby not only improving the flame retardancy and heat resistance of the polyurethane fiber, but also improving the mechanical properties and resilience of the polyurethane fiber.

[0018] The invention uses hexachlorocyclotriphosphazene and 2-allylphenol as raw materials to prepare allylphenoxycyclotriphosphazene having a carbon-carbon double bond functional group. Then, DOPO and allyl glycidyl ether are subjected to a ring-opening reaction under catalyst conditions to prepare allyl-modified DOPO having a carbon-carbon double bond and a hydroxyl functional group. 1,1,3,3-tetramethyldisiloxane is used as a bridging agent to connect the allyl-modified DOPO and the allylphenoxycyclotriphosphazene through a hydrosilylation reaction of the carbon-carbon double bond and the Si-H bond under platinum catalyst conditions to prepare a flame retardant having three flame retardant elements: phosphorus, nitrogen and silicon. In addition, the hydroxyl functional group in the flame retardant can participate in the polymerization reaction of a polyurethane urea prepolymer, so that the flame retardant structure is graft-copolymerized in the polymer, thereby improving the flame retardancy and flame retardancy durability of the material.

[0019] In addition, flame retardants contain rigid structures such as cyclotriphosphazene and benzene rings, and introducing them into polyurethane urea matrix materials can improve the mechanical properties and heat resistance of the materials; at the same time, flame retardants can react with diisocyanates through polyhydroxy groups, increasing the functionality of the reaction, and forming a network structure with the flame retardant center in the polyurethane urea matrix material, thereby improving the mechanical properties and elastic properties of the fiber.

[0020] The present invention adopts a method of adding isocyanate twice when preparing the polyurethane urea spinning solution, so that the free isocyanate added for the second time can easily form a hard segment with good crystallization performance during the chain extension process, thereby improving the crystallization performance of the fiber, generating cross-linking at the same time, and improving the resilience of the fiber. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the reaction for synthesizing allylphenoxy cyclotriphosphazene in the present invention; Figure 2 Schematic diagram of the reaction for synthesizing allyl-modified DOPO in the present invention; Figure 3 Schematic diagram of the reaction for synthesizing the flame retardant in the present invention; Figure 4 It is a histogram of the limiting oxygen index of Examples 1-5 and Comparative Examples 1-2 in the performance test of the present invention. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0023] Example 1

[0024] This embodiment discloses a method for preparing a highly elastic polyurethane flame-retardant fiber, comprising the following steps: Step (1), hexachlorocyclotriphosphazene, acetone, and catalyst potassium carbonate are mixed and dissolved in a mass ratio of 17:180:82, 2-allylphenol acetone solution is added at 30°C, and the mixture is reacted at 40°C for 15 hours. After the reaction is completed, the mixture is cooled to room temperature, filtered, the filtrate is collected, and the solvent acetone is removed by vacuum distillation to obtain a crude reaction product. The crude reaction product is dissolved in toluene, and 5wt% sodium hydroxide aqueous solution, 2wt% hydrochloric acid aqueous solution, and water are added in sequence to wash the mixture until it is neutral. After washing, anhydrous sodium sulfate is added to dry the mixture, the mixture is filtered, the filtrate is collected, and the solvent is removed by vacuum distillation to obtain allylphenoxycyclotriphosphazene; The molar ratio of hexachlorocyclotriphosphazene to 2-allylphenol is 1:6.5; the acetone solution of 2-allylphenol is prepared by mixing 2-allylphenol and acetone in a mass ratio of 1:5; Step (2), heating DOPO to 130°C to melt, adding allyl glycidyl ether and catalyst triphenylphosphine, reacting at 130°C for 12 hours in a nitrogen atmosphere, and cooling to room temperature after the reaction to obtain allyl-modified DOPO; The molar ratio of DOPO to allyl glycidyl ether is 1:1.1; the amount of the catalyst triphenylphosphine added is 0.7 wt% of the total mass of DOPO and allyl glycidyl ether; Allylphenoxy cyclotriphosphazene, Custer catalyst, and tetrahydrofuran were mixed, heated to 60°C, and 1,1,3,3-tetramethyldisiloxane was added dropwise for 1 hour. After the addition was completed, the mixture was reacted at 60°C for 2.5 hours. After the reaction was completed, allyl-modified DOPO was added and the mixture was reacted at 65°C for another 4 hours. After the reaction was completed, the solvent was removed by rotary evaporation to obtain a flame retardant. The mass ratio of allylphenoxy cyclotriphosphazene, 1,1,3,3-tetramethyldisiloxane, allyl-modified DOPO, Custer catalyst, and tetrahydrofuran is 93:82:192:3:3500; Step (3), reacting polytetramethylene glycol and the first portion of 4,4-diphenylmethane diisocyanate at 80°C for 2.5h, after which a prepolymer is obtained; mixing and dissolving the prepolymer and dimethylacetamide, adding the second portion of 4,4-diphenylmethane diisocyanate and mixing evenly, adding a flame retardant, and continuing to react at 70°C for 0.5h. After the reaction is completed, cooling to 10°C, adding a chain extender, and reacting again for 0.5h. After the reaction is completed, a polyurethane urea solution with a solid content of 35wt% is obtained; The mass ratio of polytetramethylene ether glycol, the first part of 4,4-diphenylmethane diisocyanate, the second part of 4,4-diphenylmethane diisocyanate, the chain extender, and the flame retardant is 340:75:23:90:50; The chain extender is prepared by dissolving ethylenediamine, propylenediamine, diethylamine, and dimethylacetamide in a mass ratio of 5:3:0.6:90; Step (4), mixing the polyurethane urea solution with an antioxidant, an anti-yellowing agent, and a matting agent in a mass ratio of 1000:0.02:0.01:0.008, and dry spinning to obtain a high-elasticity polyurethane flame-retardant fiber; The spinning speed of the dry spinning process was 800 m / min, and the spinning cylinder atmosphere temperature was 250°C.

[0025] Example 2

[0026] This embodiment discloses a method for preparing a highly elastic polyurethane flame-retardant fiber, comprising the following steps: Step (1), hexachlorocyclotriphosphazene, acetone, and catalyst potassium carbonate are mixed and dissolved in a mass ratio of 17.5:190:82.5, 2-allylphenol acetone solution is added at 30°C, and the mixture is reacted at 45°C for 13 hours. After the reaction is completed, the mixture is cooled to room temperature, filtered, the filtrate is collected, and the solvent acetone is removed by vacuum distillation to obtain a crude reaction product. The crude reaction product is dissolved in toluene, and 5wt% sodium hydroxide aqueous solution, 2wt% hydrochloric acid aqueous solution, and water are added in sequence to wash the mixture until it is neutral. After washing, anhydrous sodium sulfate is added to dry the mixture, the mixture is filtered, the filtrate is collected, and the solvent is removed by vacuum distillation to obtain allylphenoxycyclotriphosphazene; The molar ratio of hexachlorocyclotriphosphazene to 2-allylphenol is 1:6.5; the acetone solution of 2-allylphenol is prepared by mixing 2-allylphenol and acetone in a mass ratio of 1:5; Step (2), heating DOPO to 130°C to melt, adding allyl glycidyl ether and catalyst triphenylphosphine, reacting at 130°C for 12 hours in a nitrogen atmosphere, and cooling to room temperature after the reaction to obtain allyl-modified DOPO; The molar ratio of DOPO to allyl glycidyl ether is 1:1.1; the amount of the catalyst triphenylphosphine added is 0.7 wt% of the total mass of DOPO and allyl glycidyl ether; Allylphenoxy cyclotriphosphazene, Custer catalyst, and tetrahydrofuran were mixed, heated to 60°C, and 1,1,3,3-tetramethyldisiloxane was added dropwise for 1 hour. After the addition was completed, the mixture was reacted at 60°C for 2.5 hours. After the reaction was completed, allyl-modified DOPO was added and the mixture was reacted at 70°C for 3.5 hours. After the reaction was completed, the solvent was removed by rotary evaporation to obtain a flame retardant. The mass ratio of allylphenoxy cyclotriphosphazene, 1,1,3,3-tetramethyldisiloxane, allyl-modified DOPO, Custer catalyst, and tetrahydrofuran is 93.5:82.5:196:3.1:3600; Step (3), reacting polytetramethylene glycol and the first portion of 4,4-diphenylmethane diisocyanate at 80°C for 2.5h, after which a prepolymer is obtained; mixing and dissolving the prepolymer and dimethylacetamide, adding the second portion of 4,4-diphenylmethane diisocyanate and mixing evenly, adding a flame retardant, and continuing to react at 70°C for 0.5h. After the reaction is completed, cooling to 10°C, adding a chain extender, and reacting again for 0.5h. After the reaction is completed, a polyurethane urea solution with a solid content of 35wt% is obtained; The mass ratio of polytetramethylene ether glycol, the first portion of 4,4-diphenylmethane diisocyanate, the second portion of 4,4-diphenylmethane diisocyanate, the chain extender, and the flame retardant is 340:76:23.5:87:53; The chain extender is prepared by dissolving ethylenediamine, propylenediamine, diethylamine, and dimethylacetamide in a mass ratio of 5.05:3:0.55:90; Step (4), mixing the polyurethane urea solution with an antioxidant, an anti-yellowing agent, and a matting agent in a mass ratio of 1000:0.02:0.01:0.008, and dry spinning to obtain a high-elasticity polyurethane flame-retardant fiber; The spinning speed of the dry spinning process was 800 m / min, and the spinning cylinder atmosphere temperature was 250°C.

[0027] Example 3

[0028] This embodiment discloses a method for preparing a highly elastic polyurethane flame-retardant fiber, comprising the following steps: Step (1), hexachlorocyclotriphosphazene, acetone, and catalyst potassium carbonate are mixed and dissolved in a mass ratio of 17.5:190:82.5, 2-allylphenol acetone solution is added at 30°C, and the mixture is reacted at 45°C for 13 hours. After the reaction is completed, the mixture is cooled to room temperature, filtered, the filtrate is collected, and the solvent acetone is removed by vacuum distillation to obtain a crude reaction product. The crude reaction product is dissolved in toluene, and 5wt% sodium hydroxide aqueous solution, 2wt% hydrochloric acid aqueous solution, and water are added in sequence to wash the mixture until it is neutral. After washing, anhydrous sodium sulfate is added to dry the mixture, the mixture is filtered, the filtrate is collected, and the solvent is removed by vacuum distillation to obtain allylphenoxycyclotriphosphazene; The molar ratio of hexachlorocyclotriphosphazene to 2-allylphenol is 1:6.8; the acetone solution of 2-allylphenol is prepared by mixing 2-allylphenol and acetone in a mass ratio of 1:5; Step (2), heating DOPO to 130°C to melt, adding allyl glycidyl ether and catalyst triphenylphosphine, reacting at 130°C for 12 hours in a nitrogen atmosphere, and cooling to room temperature after the reaction to obtain allyl-modified DOPO; The molar ratio of DOPO to allyl glycidyl ether is 1:1.1; the amount of the catalyst triphenylphosphine added is 0.7 wt% of the total mass of DOPO and allyl glycidyl ether; Allylphenoxy cyclotriphosphazene, Custer catalyst, and tetrahydrofuran were mixed, heated to 60°C, and 1,1,3,3-tetramethyldisiloxane was added dropwise for 1 hour. After the addition was completed, the mixture was reacted at 65°C for 2.3 hours. After the reaction was completed, allyl-modified DOPO was added and the mixture was reacted at 70°C for 3.5 hours. After the reaction was completed, the solvent was removed by rotary evaporation to obtain a flame retardant. The mass ratio of allylphenoxy cyclotriphosphazene, 1,1,3,3-tetramethyldisiloxane, allyl-modified DOPO, Custer catalyst, and tetrahydrofuran is 94:83:200:3.3:3800; Step (3), reacting polytetramethylene glycol and the first portion of 4,4-diphenylmethane diisocyanate at 83°C for 2.3h, after which a prepolymer is obtained; mixing and dissolving the prepolymer and dimethylacetamide, adding the second portion of 4,4-diphenylmethane diisocyanate and mixing evenly, adding a flame retardant, and continuing to react at 72°C for 0.5h. After the reaction is completed, cooling to 10°C, adding a chain extender, and reacting again for 0.8h. After the reaction is completed, a polyurethane urea solution with a solid content of 35wt% is obtained; The mass ratio of polytetramethylene ether glycol, the first part of 4,4-diphenylmethane diisocyanate, the second part of 4,4-diphenylmethane diisocyanate, the chain extender, and the flame retardant is 340:78:24:85:55; The chain extender is prepared by dissolving ethylenediamine, propylenediamine, diethylamine, and dimethylacetamide in a mass ratio of 5.05:3:0.55:90; Step (4), mixing the polyurethane urea solution with an antioxidant, an anti-yellowing agent, and a matting agent in a mass ratio of 1000:0.02:0.01:0.008, and dry spinning to obtain a high-elasticity polyurethane flame-retardant fiber; The spinning speed of the dry spinning method was 850 m / min, and the spinning cylinder atmosphere temperature was 250°C.

[0029] Example 4

[0030] This embodiment discloses a method for preparing a highly elastic polyurethane flame-retardant fiber, comprising the following steps: Step (1), hexachlorocyclotriphosphazene, acetone, and catalyst potassium carbonate are mixed and dissolved in a mass ratio of 18:190:83, 2-allylphenol acetone solution is added at 30°C, and the mixture is reacted at 45°C for 13 hours. After the reaction is completed, the mixture is cooled to room temperature, filtered, the filtrate is collected, and the solvent acetone is removed by vacuum distillation to obtain a crude reaction product. The crude reaction product is dissolved in toluene, and 5wt% sodium hydroxide aqueous solution, 2wt% hydrochloric acid aqueous solution, and water are added in sequence to wash the mixture until it is neutral. After washing, anhydrous sodium sulfate is added to dry the mixture, the mixture is filtered, the filtrate is collected, and the solvent is removed by vacuum distillation to obtain allylphenoxycyclotriphosphazene; The molar ratio of hexachlorocyclotriphosphazene to 2-allylphenol is 1:7; the acetone solution of 2-allylphenol is prepared by mixing 2-allylphenol and acetone in a mass ratio of 1:6; Step (2), heating DOPO to 130°C to melt, adding allyl glycidyl ether and catalyst triphenylphosphine, reacting at 130°C for 12 hours in a nitrogen atmosphere, and cooling to room temperature after the reaction to obtain allyl-modified DOPO; The molar ratio of DOPO to allyl glycidyl ether is 1:1.1; the amount of the catalyst triphenylphosphine added is 0.7 wt% of the total mass of DOPO and allyl glycidyl ether; Allylphenoxy cyclotriphosphazene, Custer catalyst, and tetrahydrofuran were mixed, heated to 60°C, and 1,1,3,3-tetramethyldisiloxane was added dropwise for 1 hour. After the addition was completed, the mixture was reacted at 70°C for 2 hours. After the reaction was completed, allyl-modified DOPO was added and the mixture was reacted at 75°C for 3 hours. After the reaction was completed, the solvent was removed by rotary evaporation to obtain a flame retardant. The mass ratio of allylphenoxy cyclotriphosphazene, 1,1,3,3-tetramethyldisiloxane, allyl-modified DOPO, Custer catalyst, and tetrahydrofuran is 94.5:84:204:3.4:3800; Step (3), reacting polytetramethylene glycol and the first portion of 4,4-diphenylmethane diisocyanate at 85°C for 2h, after which a prepolymer is obtained; mixing and dissolving the prepolymer and dimethylacetamide, adding the second portion of 4,4-diphenylmethane diisocyanate and mixing evenly, adding a flame retardant, and continuing to react at 75°C for 0.5h. After the reaction is completed, cooling to 10°C, adding a chain extender, and reacting again for 1h. After the reaction is completed, a polyurethane urea solution with a solid content of 35wt% is obtained; The mass ratio of polytetramethylene ether glycol, the first part of 4,4-diphenylmethane diisocyanate, the second part of 4,4-diphenylmethane diisocyanate, the chain extender, and the flame retardant is 340:79:24.5:82:58; The chain extender is prepared by dissolving ethylenediamine, propylenediamine, diethylamine, and dimethylacetamide in a mass ratio of 5.1:3:0.6:90; Step (4), mixing the polyurethane urea solution with an antioxidant, an anti-yellowing agent, and a matting agent in a mass ratio of 1000:0.02:0.01:0.008, and dry spinning to obtain a high-elasticity polyurethane flame-retardant fiber; The spinning speed of the dry spinning process was 900 m / min, and the spinning cylinder atmosphere temperature was 250°C.

[0031] Example 5

[0032] This embodiment discloses a method for preparing a highly elastic polyurethane flame-retardant fiber, comprising the following steps: Step (1), hexachlorocyclotriphosphazene, acetone, and catalyst potassium carbonate are mixed and dissolved in a mass ratio of 18:200:83, 2-allylphenol acetone solution is added at 30°C, and the mixture is reacted at 50°C for 12 hours. After the reaction is completed, the mixture is cooled to room temperature, filtered, the filtrate is collected, and the solvent acetone is removed by vacuum distillation to obtain a crude reaction product. The crude reaction product is dissolved in toluene, and 5wt% sodium hydroxide aqueous solution, 2wt% hydrochloric acid aqueous solution, and water are added in sequence to wash the mixture until it is neutral. After washing, anhydrous sodium sulfate is added to dry the mixture, the mixture is filtered, the filtrate is collected, and the solvent is removed by vacuum distillation to obtain allylphenoxycyclotriphosphazene; The molar ratio of hexachlorocyclotriphosphazene to 2-allylphenol is 1:7; the acetone solution of 2-allylphenol is prepared by mixing 2-allylphenol and acetone in a mass ratio of 1:6; Step (2), heating DOPO to 130°C to melt, adding allyl glycidyl ether and catalyst triphenylphosphine, reacting at 130°C for 12 hours in a nitrogen atmosphere, and cooling to room temperature after the reaction to obtain allyl-modified DOPO; The molar ratio of DOPO to allyl glycidyl ether is 1:1.1; the amount of the catalyst triphenylphosphine added is 0.7 wt% of the total mass of DOPO and allyl glycidyl ether; Allylphenoxy cyclotriphosphazene, Custer catalyst, and tetrahydrofuran were mixed, heated to 60°C, and 1,1,3,3-tetramethyldisiloxane was added dropwise for 1 hour. After the addition was completed, the mixture was reacted at 70°C for 2 hours. After the reaction was completed, allyl-modified DOPO was added and the mixture was reacted at 75°C for 3 hours. After the reaction was completed, the solvent was removed by rotary evaporation to obtain a flame retardant. The mass ratio of allylphenoxy cyclotriphosphazene, 1,1,3,3-tetramethyldisiloxane, allyl-modified DOPO, Custer catalyst, and tetrahydrofuran is 95:84.5:208:3.5:4000; Step (3), reacting polytetramethylene glycol and the first portion of 4,4-diphenylmethane diisocyanate at 85°C for 2h, after which a prepolymer is obtained; mixing and dissolving the prepolymer and dimethylacetamide, adding the second portion of 4,4-diphenylmethane diisocyanate and mixing evenly, adding a flame retardant, and continuing to react at 75°C for 0.5h. After the reaction is completed, cooling to 10°C, adding a chain extender, and reacting again for 1h. After the reaction is completed, a polyurethane urea solution with a solid content of 35wt% is obtained; The mass ratio of polytetramethylene ether glycol, the first part of 4,4-diphenylmethane diisocyanate, the second part of 4,4-diphenylmethane diisocyanate, the chain extender, and the flame retardant is 340:80:25:80:60; The chain extender is prepared by dissolving ethylenediamine, propylenediamine, diethylamine, and dimethylacetamide in a mass ratio of 5.1:3:0.5:90; Step (4), mixing the polyurethane urea solution with an antioxidant, an anti-yellowing agent, and a matting agent in a mass ratio of 1000:0.02:0.01:0.008, and dry spinning to obtain a high-elasticity polyurethane flame-retardant fiber; The spinning speed of the dry spinning process was 900 m / min, and the spinning cylinder atmosphere temperature was 250°C.

[0033] Comparative Example 1 This comparative example discloses a method for preparing polyurethane fibers, comprising the following steps: Step (1), hexachlorocyclotriphosphazene, acetone, and catalyst potassium carbonate are mixed and dissolved in a mass ratio of 17:180:82, 2-allylphenol acetone solution is added at 30°C, and the mixture is reacted at 40°C for 15 hours. After the reaction is completed, the mixture is cooled to room temperature, filtered, the filtrate is collected, and the solvent acetone is removed by vacuum distillation to obtain a crude reaction product. The crude reaction product is dissolved in toluene, and 5wt% sodium hydroxide aqueous solution, 2wt% hydrochloric acid aqueous solution, and water are added in sequence to wash the mixture until it is neutral. After washing, anhydrous sodium sulfate is added to dry the mixture, the mixture is filtered, the filtrate is collected, and the solvent is removed by vacuum distillation to obtain allylphenoxycyclotriphosphazene; The molar ratio of hexachlorocyclotriphosphazene to 2-allylphenol is 1:6.5; the acetone solution of 2-allylphenol is prepared by mixing 2-allylphenol and acetone in a mass ratio of 1:5; Step (2), reacting polytetramethylene glycol and the first portion of 4,4-diphenylmethane diisocyanate at 80°C for 2.5h, after which a prepolymer is obtained; mixing and dissolving the prepolymer and dimethylacetamide, adding the second portion of 4,4-diphenylmethane diisocyanate and mixing evenly, adding allylphenoxy cyclotriphosphazene, and continuing to react at 70°C for 0.5h, after which the reaction is completed, cooling to 10°C, adding a chain extender, and reacting again for 0.5h, after which a polyurethane urea solution with a solid content of 35wt% is obtained; The mass ratio of polytetramethylene ether glycol, the first portion of 4,4-diphenylmethane diisocyanate, the second portion of 4,4-diphenylmethane diisocyanate, the chain extender, and allylphenoxy cyclotriphosphazene is 340:75:23:90:50; The chain extender is prepared by dissolving ethylenediamine, propylenediamine, diethylamine, and dimethylacetamide in a mass ratio of 5:3:0.6:90; Step (4), mixing the polyurethane urea solution with an antioxidant, an anti-yellowing agent, and a matting agent in a mass ratio of 1000:0.02:0.01:0.008, and dry spinning to obtain polyurethane fibers; The spinning speed of the dry spinning process was 800 m / min, and the spinning cylinder atmosphere temperature was 250°C.

[0034] Comparative Example 2 This comparative example discloses a method for preparing polyurethane fibers, comprising the following steps: Step (1), hexachlorocyclotriphosphazene, acetone, and catalyst potassium carbonate are mixed and dissolved in a mass ratio of 17:180:82, 2-allylphenol acetone solution is added at 30°C, and the mixture is reacted at 40°C for 15 hours. After the reaction is completed, the mixture is cooled to room temperature, filtered, the filtrate is collected, and the solvent acetone is removed by vacuum distillation to obtain a crude reaction product. The crude reaction product is dissolved in toluene, and 5wt% sodium hydroxide aqueous solution, 2wt% hydrochloric acid aqueous solution, and water are added in sequence to wash the mixture until it is neutral. After washing, anhydrous sodium sulfate is added to dry the mixture, the mixture is filtered, the filtrate is collected, and the solvent is removed by vacuum distillation to obtain allylphenoxycyclotriphosphazene; The molar ratio of hexachlorocyclotriphosphazene to 2-allylphenol is 1:6.5; the acetone solution of 2-allylphenol is prepared by mixing 2-allylphenol and acetone in a mass ratio of 1:5; Step (2), heating DOPO to 130°C to melt, adding allyl glycidyl ether and catalyst triphenylphosphine, reacting at 130°C for 12 hours in a nitrogen atmosphere, and cooling to room temperature after the reaction to obtain allyl-modified DOPO; The molar ratio of DOPO to allyl glycidyl ether is 1:1.1; the amount of the catalyst triphenylphosphine added is 0.7 wt% of the total mass of DOPO and allyl glycidyl ether; Allylphenoxy cyclotriphosphazene, Custer catalyst, and tetrahydrofuran were mixed, heated to 60°C, and 1,1,3,3-tetramethyldisiloxane was added dropwise for 1 hour. After the addition was completed, the mixture was reacted at 60°C for 2.5 hours. After the reaction was completed, allyl-modified DOPO was added and the mixture was reacted at 65°C for another 4 hours. After the reaction was completed, the solvent was removed by rotary evaporation to obtain a flame retardant. The mass ratio of allylphenoxy cyclotriphosphazene, 1,1,3,3-tetramethyldisiloxane, allyl-modified DOPO, Custer catalyst, and tetrahydrofuran is 93:82:192:3:3500; Step (3), reacting polytetramethylene glycol and 4,4-diphenylmethane diisocyanate at 80°C for 2.5 hours, after which a prepolymer is obtained; mixing and dissolving the prepolymer and dimethylacetamide, adding a flame retardant, and continuing to react at 70°C for 0.5 hours, after which the reaction is completed, cooling to 10°C, adding a chain extender, and reacting again for 0.5 hours, after which a polyurethane urea solution with a solid content of 35 wt% is obtained; The mass ratio of polytetramethylene ether glycol, 4,4-diphenylmethane diisocyanate, chain extender and flame retardant is 340:98:90:50; The chain extender is prepared by dissolving ethylenediamine, propylenediamine, diethylamine, and dimethylacetamide in a mass ratio of 5:3:0.6:90; Step (4), mixing the polyurethane urea solution with an antioxidant, an anti-yellowing agent, and a matting agent in a mass ratio of 1000:0.02:0.01:0.008, and dry spinning to obtain polyurethane fibers; The spinning speed of the dry spinning process was 800 m / min, and the spinning cylinder atmosphere temperature was 250°C.

[0035] In the above examples and comparative examples, the Mn of the polytetramethylene ether glycol is 1800; the specification of the Custer catalyst is 1000 ppm; the antioxidant is BASF light stabilizer 622; the anti-yellowing agent is TSA011; and the matting agent is nano-titanium dioxide with a particle size of 0.35-0.5 μm.

[0036] Test example The mechanical properties, heat resistance and flame retardancy of the polyurethane fibers prepared in Examples 1-5 and Comparative Examples 1-2 were tested. Specific test results are shown in Table 1: Table 1

[0037] The testing of each index in Table 1 is based on the following standards: the breaking strength is measured with reference to GB / T14344-2008 "Test method for tensile properties of chemical fiber filaments"; the rebound rate is tested by stretching the polyurethane fibers prepared in Examples 1-5 and Comparative Examples 1-2 to 300% of the original length, fixing them for 20 minutes, and then performing a rebound performance test with reference to FZ / T50007-2012 "Test method for elasticity of spandex yarn"; the heat resistance is represented by the breaking strength retention rate, and is tested under dry heat conditions with reference to FZ / T 50033-2016 "Test method for heat resistance of spandex filaments"; the limiting oxygen index is tested with reference to GB / T 5454 "Determination of burning behavior of textiles - Determination of oxygen index".

[0038] According to the test results in Table 1, it can be seen that the polyurethane fiber prepared in the present invention has excellent flame retardancy and heat resistance, as well as good mechanical properties and resilience.

[0039] In order to improve the comprehensive performance of polyurethane fibers, the present invention uses 1,1,3,3-tetramethyldisiloxane as a bridging agent to connect allyl-modified DOPO and allylphenoxycyclotriphosphazene to prepare a flame retardant simultaneously containing three flame retardant elements: phosphorus, nitrogen, and silicon. In addition, due to the presence of hydroxyl functional groups in the flame retardant, the hydroxyl functional groups can participate in the polymerization reaction of the polyurethane urea prepolymer, so that the flame retardant structure is grafted and copolymerized in the polymer, thereby improving the flame retardancy and flame retardancy durability of the material.

[0040] In addition, flame retardants contain rigid structures such as cyclotriphosphazene and benzene rings, and introducing them into polyurethane urea matrix materials can improve the mechanical properties and heat resistance of the materials; at the same time, flame retardants can react with diisocyanates through polyhydroxy groups, increasing the functionality of the reaction, and forming a network structure with the flame retardant center in the polyurethane urea matrix material, thereby improving the mechanical properties and elastic properties of the fiber.

[0041] The present invention employs a secondary isocyanate addition method when preparing the polyurethane urea spinning solution. This allows the free isocyanate added in the second addition to readily form hard segments with superior crystallization properties during the chain extension process, thereby enhancing the crystallization properties of the fiber and simultaneously generating crosslinking, improving the fiber's resilience. Furthermore, during the dry-laid spandex forming process, molecular chain orientation is promoted, resulting in a more regular arrangement of the polyurethane material's molecular chains, thereby improving the macroscopic thermal stability of the fiber material.

[0042] Comparative Example 1 flame retardant uses allylphenoxy cyclotriphosphazene, lacks the effect of allyl modified DOPO and 1,1,3,3-tetramethyldisiloxane on improving the flame retardant performance, so the flame retardant performance of Comparative Example 1 is not as good as that of Example In Comparative Example 2, when preparing polyurethane fibers, 4,4-diphenylmethane diisocyanate was added all at once. Since the method of adding isocyanate twice can easily form a hard segment with good crystallization performance during the chain extension process, thereby improving the crystallization performance of the fiber, and at the same time generating cross-linking, improving the resilience of the fiber, so the breaking strength and resilience of Comparative Example 2 are not as good as those of the embodiment.

[0043] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a highly elastic polyurethane flame-retardant fiber, characterized in that: The following steps are involved: Step (1), allylphenoxy cyclotriphosphazene, Custer catalyst, and tetrahydrofuran are mixed, the temperature is increased, 1,1,3,3-tetramethyldisiloxane is added dropwise, and after the addition is completed, the mixture is reacted. After the reaction is completed, allyl-modified DOPO is added and the reaction is continued. After the reaction is completed, the mixture is rotary evaporated to obtain a flame retardant; Step (2), reacting polytetramethylene glycol and the first portion of 4,4-diphenylmethane diisocyanate, and obtaining a prepolymer after the reaction is completed; mixing and dissolving the prepolymer and dimethylacetamide, adding the second portion of 4,4-diphenylmethane diisocyanate and mixing evenly, adding a flame retardant, and continuing the reaction. After the reaction is completed, cooling, adding a chain extender, and reacting again, and obtaining a polyurethane urea solution after the reaction is completed; Step (3): mixing the polyurethane urea solution with an antioxidant, a dyeing assistant, and a matting agent, and dry spinning the mixture to obtain a highly elastic polyurethane flame-retardant fiber.

2. The method for preparing a highly elastic polyurethane flame-retardant fiber according to claim 1, characterized in that: The allylphenoxy cyclotriphosphazene in step (1) is prepared by the following steps: Hexachlorocyclotriphosphazene, acetone, and a catalyst, potassium carbonate, are mixed and dissolved, and an acetone solution of 2-allylphenol is added, reacted, and after completion of the reaction, purified to obtain allylphenoxycyclotriphosphazene; The molar ratio of hexachlorocyclotriphosphazene to 2-allylphenol is 1:6.5-7; the acetone solution of 2-allylphenol is prepared by mixing 2-allylphenol and acetone in a mass ratio of 1:5-6; the mass ratio of hexachlorocyclotriphosphazene, acetone, and catalyst potassium carbonate is 17-18:180-200:82-83; and the reaction conditions are: reaction at a temperature of 40-50°C for 12-15 hours.

3. The method for preparing the highly elastic polyurethane flame-retardant fiber according to claim 1, characterized in that: The allyl-modified DOPO in step (1) is prepared by the following steps: The DOPO is heated until it melts, and allyl glycidyl ether and a catalyst, triphenylphosphine, are added to react. After the reaction is completed, the reaction is cooled to obtain allyl-modified DOPO; The molar ratio of DOPO to allyl glycidyl ether is 1:1-1.1; the amount of triphenylphosphine catalyst added is 0.5-0.8 wt% of the total mass of DOPO and allyl glycidyl ether; and the reaction conditions are: in a nitrogen atmosphere, at a temperature of 130° C. for 10-12 hours.

4. The method for preparing a highly elastic polyurethane flame-retardant fiber according to claim 1, characterized in that: In the step (1), the mass ratio of allylphenoxy cyclotriphosphazene, 1,1,3,3-tetramethyldisiloxane, allyl modified DOPO, Custer catalyst, and tetrahydrofuran is 93-95:82-84.5:192-208:3-3.5:3500-4000; when preparing the flame retardant, the reaction conditions are: reacting at a temperature of 60-70°C for 2-2.5 hours; and the continued reaction conditions are: continuing the reaction at a temperature of 65-75°C for 3-4 hours.

5. The method for preparing a highly elastic polyurethane flame-retardant fiber according to claim 1, characterized in that: In the step (2), the mass ratio of polytetramethylene glycol, the first portion of 4,4-diphenylmethane diisocyanate, the second portion of 4,4-diphenylmethane diisocyanate, the chain extender, and the flame retardant is 340:75-80:23-25:80-90:50-60; The chain extender is prepared by mixing and dissolving ethylenediamine, propylenediamine, diethylamine and dimethylacetamide in a mass ratio of 5-5.1:3:0.5-0.6:90-100.

6. The method for preparing a highly elastic polyurethane flame-retardant fiber according to claim 1, characterized in that: In the step (2), the reaction conditions are: reacting at 80-85°C for 2-2.5 hours; continuing the reaction conditions are: continuing the reaction at 70-75°C for 0.5 hours; and re-reacting conditions are: reacting again at 10°C for 0.5-1 hours.

7. The method for preparing a highly elastic polyurethane flame-retardant fiber according to claim 1, characterized in that: In the step (2), the solid content of the polyurethane urea solution is 30-40 wt%.

8. The method for preparing a highly elastic polyurethane flame-retardant fiber according to claim 1, characterized in that: In the step (3), the mass ratio of the polyurethane urea solution to the antioxidant, the anti-yellowing agent, and the matting agent is 1000:0.02-0.03:0.01-0.02:0.008-0.01; the spinning speed of the dry spinning is 800-900 m / min, and the spinning cylinder atmosphere temperature is 250-270°C.

9. A high-elasticity polyurethane flame-retardant fiber prepared by the method for preparing a high-elasticity polyurethane flame-retardant fiber according to any one of claims 1 to 8.

10. Use of the highly elastic polyurethane flame-retardant fiber according to claim 9 in telescopic wires.

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