High performance flame retardant spandex fiber and method of making same

Abstract

This invention proposes a high-performance flame-retardant spandex fiber and its preparation method, belonging to the technical field of chemical fiber manufacturing, to solve the technical problem of poor flame retardancy of flame-retardant polyurethane. The invention includes the following steps: mixing a polydiol with a diisocyanate and then performing a prepolymerization reaction to obtain a prepolymer; dissolving a phosphorus-containing dihydroxy compound, a nitrogen-containing dihydroxy compound, and a catalyst in a polar amine solution to prepare a mixed solution; mixing the mixed solution with the prepolymer and then performing a polymerization reaction to obtain a low-molecular-weight polyurethane containing phosphorus in its molecular chain; mixing the low-molecular-weight polyurethane with a chain extender and then performing a chain extension reaction to obtain a phosphorus-containing polyurethane urea solution; and then curing the phosphorus-containing polyurethane urea solution and spinning it to obtain high-performance flame-retardant spandex yarn. This invention utilizes the crosslinking characteristics of nitrogen-containing moieties at high temperatures and the synergistic flame-retardant advantages of phosphorus and nitrogen. It not only solves the problems of poor compatibility and easy shedding between conventional flame retardants and spandex macromolecules, but also improves the molecular chain forces and the viscosity of the spandex spinning solution, enabling it to meet the requirements of high-speed dry spinning. This endows spandex with excellent flame-retardant properties, mechanical properties, and controllable elasticity, improves spandex preparation efficiency, and significantly reduces costs.

Description

Technical Field

[0001] This invention belongs to the technical field of chemical fiber manufacturing, and particularly relates to a high-performance flame-retardant spandex fiber and its preparation method. Background Technology

[0002] Spandex possesses unparalleled elasticity compared to other synthetic fibers, with a breaking elongation of up to 800% and an elastic recovery rate exceeding 95%. It is widely used in textiles, apparel, medical and health products, sports equipment, and national defense. Even a small amount added can impart excellent elasticity, comfort, and shape retention to textiles, making it an indispensable fiber material for high-end textiles and holding a vital position in the national economy and national defense.

[0003] Conventional spandex polymers are prepared by stepwise polymerization and chain extension reactions of aliphatic polydiols and aromatic diisocyanates. The presence of a large amount of aliphatic diols in the molecular chain results in poor flame retardancy and heat resistance of conventional spandex, which cannot meet the requirements of high-end applications. To improve the flame retardancy of spandex, small-molecule flame retardants are usually added during the polymerization or spinning process. However, this method has drawbacks such as poor compatibility between the flame retardant and the large spandex molecules, high addition amounts of flame retardant, easy shedding, and impact on spinnability and mechanical properties.

[0004] For example, patent publication number CN103361974A describes a method for preparing flame-retardant spandex fibers. This method uses a flame retardant prepared from triethyl phosphate, methanol, and octabromoether solution. The spandex fabric is immersed in the prepared flame retardant solution, heated to 50°C, and soaked for a certain period before being removed and dried. This gives the fabric highly efficient flame-retardant properties. However, the flame-retardant properties of the spandex fabric prepared by this method still have many shortcomings. Because the flame retardant is attached to the fiber surface, it detaches after repeated washing, weakening the fiber's flame-retardant properties. Furthermore, spandex products with flame retardant on the surface tend to feel rough and stiff, which is detrimental to long-term use and commercial production.

[0005] Patent publication number CN114672897A describes a method for preparing antistatic and flame-retardant spandex fibers. The method involves rapidly dispersing and mixing spandex chips, a nonionic antistatic agent, anionic surfactant, and a phosphate ester flame retardant in a high-speed mixer to obtain an antistatic and flame-retardant spandex masterbatch, followed by melt spinning to obtain spandex fibers with antistatic, high-strength, and flame-retardant properties. However, this method, which involves melting and mixing spandex chips, nonionic antistatic agents, anionic surfactants, and phosphate ester flame retardants, results in fibers with a breaking strength of only 0.93 cN / dtex to 0.98 cN / dtex and a breaking elongation of 450% to 500%. The addition of flame retardants leads to a significant decrease in breaking strength and breaking elongation. Furthermore, the limiting oxygen index is only 27% to 30%, with a relatively small improvement. Due to the use of melt spinning, the fiber fineness is relatively large, making it impossible to produce fine denier spandex yarns; further optimization and improvement are needed.

[0006] Patent CN103590138A discloses a method for preparing flame-retardant polyurethane elastic fibers. The method involves two main steps: copolymerizing with a phosphorus-based flame retardant to ensure permanent flame retardancy; blending with small amounts of halogen-free phosphonate flame retardants, melamine flame retardants, and alumina flame retardants to further ensure excellent flame retardant properties and reduce combustion dripping, thus preparing a superior spinning solution; and subsequent dry spinning. In this patent, the phosphorus-based flame retardant is copolymerized into the polyurethane molecular chain to give the prepared fiber permanent flame retardancy. However, the flame retardancy of the fiber obtained solely through copolymerization is relatively poor, and additional flame retardants need to be added to the system to meet the requirements. Summary of the Invention

[0007] To address the technical problem of poor flame retardancy in flame-retardant spandex, this invention proposes a high-performance flame-retardant spandex fiber and its preparation method. Utilizing the cross-linking characteristics of nitrogen-containing building blocks at high temperatures and the synergistic flame-retardant advantages of phosphorus and nitrogen, this invention not only solves the problems of poor compatibility and easy detachment between conventional flame retardants and spandex macromolecules, but also improves the molecular chain forces and increases the viscosity of the spandex spinning solution, enabling it to meet the requirements of high-speed dry spinning. This endows spandex with excellent flame retardant properties, mechanical properties, and controllable elasticity, improving spandex preparation efficiency and significantly reducing costs.

[0008] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0009] A high-performance flame-retardant spandex fiber and its preparation method are disclosed below.

[0010] (1) Prepolymerization: Polydiol and diisocyanate are added to a prepolymerization reactor and stirred at high speed to obtain a prepolymer.

[0011] The polydiol is a polyether diol or a polyester diol with a molecular weight of 1000-3000;

[0012] The polyether diol is one of polytetrahydrofuran ether diol, polyethylene glycol, and polypropylene glycol;

[0013] The polyester diol is one of polybutylene succinate diol, polybutylene adipate diol, and polybutylene sebacate diol.

[0014] (2) Polymerization: The phosphorus-containing dihydroxy compound and catalyst are dissolved in a polar amine solution and transported to the final polymerization reactor to react with the prepolymer to obtain a low molecular weight polyurethane containing phosphorus in the molecular chain; next, the chain extender and additives are dissolved and dispersed in a polar amine solution and added to the final polymerization reactor by multi-point injection to extend the chain of the phosphorus-containing prepolymer to obtain a phosphorus-containing polyurethane urea solution.

[0015] The phosphorus-containing dihydroxy compound is one of the following structures:

[0016]

[0017] The nitrogen-containing dihydroxy compound has one of the following structures:

[0018]

[0019] The molar ratio of phosphorus-containing and nitrogen-containing dihydroxy compounds is 1:9-9:1, and the molar ratio of the total amount of the two compounds to the polydiol is 1:9-5:5.

[0020] The catalyst is one of stannous octoate, dibutyltin dilaurate, and dibutyltin disulfide, and the amount used is 0.01-0.5 wt% of the total mass of the monomers;

[0021] The chain extender is a mixture of diamine and diol, with a ratio of 1:9 to 9:1, and its dosage is 20-50 mol% of diisocyanate, injected through the feed inlet at position 3-5; wherein the diamine is one of the following structures;

[0022]

[0023] The diol mentioned is one of the following structures.

[0024]

[0025] The additives mentioned are light stabilizers, antioxidants, and antibacterial agents, and the dosage is 0.1-3 wt% of the total mass of the spinning solution.

[0026] The polar amine solution is N,N-dimethylformamide or N,N-dimethylacetamide, and its amount is 3-5 times the total mass of the dihydroxy compounds.

[0027] (3) Spinning: The phosphorus-containing polyurethane urea solution is aged to obtain the spinning solution, which is then transported to the spinning box by a metering pump and extruded by spinning. The filaments are solidified in the spinning channel and then wound to obtain high-performance flame-retardant spandex filaments.

[0028] The viscosity of the spinning solution is 20-50 Pa·s, the number of spinnerets is 60-300, the temperature of the hot air or hot nitrogen in the spinning tunnel is 230-280℃, the gas flow rate is 0.1-1 m / s, and the winding speed is 600-1500 m / min.

[0029] The high-performance flame-retardant spandex fiber has a weight-average molecular weight greater than 90,000, a breaking strength greater than 1.3 cN / dtex, and a limiting oxygen index greater than 30%.

[0030] The beneficial effects of this invention are as follows: This invention copolymerizes aromatic phosphorus- and nitrogen-containing dihydroxy compounds with polyols and isocyanates, and uses phosphorus-containing diols for chain extension. The chain extension reaction is carried out at a temperature of 40-80℃ for 30-90 minutes. Phosphorus-containing spandex spinning dopes with a phosphorus content greater than 1.4 wt% can be prepared through continuous polymerization, and high-performance flame-retardant spandex fibers can be obtained by dry spinning. By introducing phosphorus-containing moieties, azo dyes (-N=N-), and Schiff bases (-N=CH-) into the spandex macromolecular chain through molecular structure design, and utilizing the crosslinking characteristics of azo dyes and Schiff bases at high temperatures and the synergistic flame-retardant advantages of phosphorus and nitrogen, this approach not only solves the problems of poor compatibility and easy detachment between conventional flame retardants and spandex macromolecules, but also improves the molecular chain forces and increases the viscosity of the spandex spinning solution. Furthermore, by adding chain extenders through multi-position injection, the chain extenders can be rapidly dispersed into the prepolymer solution, improving the uniformity of the chain extension reaction and obtaining a high-molecular-weight, highly uniform spinning solution that meets the requirements of high-speed dry spinning. Ultimately, this endows spandex with excellent flame-retardant properties, mechanical properties, and controllable elasticity, and allows for adjustable and controllable fineness from 5-40D, improving spandex production efficiency and significantly reducing costs. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 The thermogravimetric curves of spandex in Example 1 and Comparative Example 1 are shown.

[0033] Figure 2Microscopic image of the surface morphology of spandex in Example 1 (magnification 1000x).

[0034] Figure 3 The image shows the GPC curve of the flame-retardant spandex in Example 1.

[0035] Figure 4 The rheological curves are shown in Example 1 and Comparative Example 1.

[0036] Figure 5 This is the strength curve in Example 1.

[0037] Figure 6 This is a cone-shaped combustion image of Example 1. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] Example 1

[0040] This embodiment describes a high-performance flame-retardant spandex fiber and its preparation method, with the following steps:

[0041] Polytetrahydrofuran ether diol and 4,4'-methylenebis(phenyl isocyanate) were added to a prepolymer reactor at a molar ratio of 1:1.8 and reacted at 90°C with high-speed stirring for 80 min to prepare a prepolymer, which was then transferred to a final polymerization reactor. Next, phosphorus-containing dihydroxy compound DOPO-HQ and nitrogen-containing dihydroxy compound NBP6 were dissolved in N,N-dimethylformamide solution (DMF) at a molar ratio of 9:1, with the DMF amount being 3 times that of the dihydroxy compounds. 0.01 wt% of stannous octoate catalyst was added, and the mixture was transferred to the final polymerization reactor (the total amount of DOPO-HQ and NBP6 was 1 / 2 of the amount of polytetrahydrofuran ether diol). The mixture was reacted with the prepolymer at 60°C for 10 min to obtain a low molecular weight polyurethane containing phosphorus in its molecular chain. Finally, ethylenediamine and N,N-dihydroxyethyl- (20 mol% diisocyanate chain extender) were added. Diethyl phosphate (DEPHA) (in a ratio of 1:9) and auxiliary agents, including light stabilizer 119, antioxidant 1076, and antibacterial quaternary ammonium salt, are dissolved and dispersed in a polar amine solution (auxiliary agent dosage is 0.1 wt%). This solution is then added to the final polymerization reactor via a 3-position injection method. The reaction is carried out at 40°C for 60 min to extend the chain of the phosphorus-containing prepolymer, resulting in a phosphorus-containing polyurethane urea solution with a weight-average molecular weight of 119,000. Finally, the phosphorus-containing polyurethane urea solution is cured to obtain a spinning solution with a viscosity of 26 Pa·s. This solution is then pumped into the spinning box and extruded through a spinneret with 60 spinneret holes. The filaments are solidified in a spinning tunnel filled with nitrogen at 280°C with a gas flow rate of 0.1 m / s and a winding speed of 600 m / min, resulting in a high-performance flame-retardant spandex filament with a strength of 1.81 cN / dtex, an elongation at break of 250%, and a limiting oxygen index of 34.2%. The thermal loss curve of the obtained spandex is as follows Figure 1 As shown, the initial thermal decomposition temperature and residual carbon content at 650°C of the spandex fiber prepared in Example 1 were 326°C and 14.96%, respectively, which were 63°C and 10.69% higher than those of the comparative fiber. Figure 2 The image shows the morphology of the spandex fiber in Example 1. It can be seen that the fiber fineness is uniform and the surface is relatively smooth. Figure 3 The GPC curve for the spandex fiber in Example 1 is shown, with a weight-average molecular weight of 119,000. Figure 4 The rheological curve of the spandex spinning solution in Example 1 shows that, compared with the comparative example, the spandex spinning solution in Example 1 has a higher viscosity, indicating that its molecular chains have greater rigidity and force, and it also has a higher molecular weight, which is beneficial to improving the performance of spandex fibers. Figure 5 The stress-strain curve of the spandex fiber in Example 1 is shown. The fiber fineness is 10D, the breaking strength is 19.9cN, and the strength is 1.81cN / dtex, exhibiting excellent mechanical properties. Figure 6The photograph shows the result of a cone-shaped combustion test on the spandex fiber of Example 1 after hot pressing. It can be seen that the fiber has a dense char layer structure after combustion, indicating that it has excellent flame retardancy.

[0042] Example 2

[0043] This embodiment describes a high-performance flame-retardant spandex fiber and its preparation method, with the following steps:

[0044] Polyethylene glycol and 4,4'-methylenebis(phenyl isocyanate) were added to a prepolymer reactor at a molar ratio of 1:1.9 and reacted at high speed at 80°C for 85 min to prepare a prepolymer, which was then transferred to a final polymerization reactor. Next, phosphorus-containing dihydroxy compound MH-PPOA and nitrogen-containing dihydroxy compound NBP6 were dissolved in N,N-dimethylacetamide solution (DMAC) at a molar ratio of 8:2, with the DMAC amount being 5 times that of the dihydroxy compounds. 0.05 wt% of dibutyltin dilaurate catalyst was added, and the solution was transferred to the final polymerization reactor (the total amount of MH-PPOA and NBP6 was 1 / 4 of the amount of polyethylene glycol). The mixture was reacted with the prepolymer at 55°C for 15 min to obtain a low molecular weight polyurethane containing phosphorus in its molecular chain. Finally, propylene glycol (25 mol% diisocyanate) and N,N-dihydroxyethyl-diethylamine (NOH-dimethyl-diethyl-dimethyl-2-ethyl ... Dephosphoric acid ester (DEPHA) (in a ratio of 9:1) and auxiliary agents, including light stabilizer 622, antioxidant 168, and antibacterial quaternary ammonium salt, were dissolved and dispersed in a polar amine solution (auxiliary agent dosage: 0.5 wt%). This solution was added to the final polymerization reactor via a 3-position injection method and reacted at 50°C for 60 min to extend the chain of the phosphorus-containing prepolymer, yielding a phosphorus-containing polyurethane urea solution with a weight-average molecular weight of 128,000. Finally, the phosphorus-containing polyurethane urea solution was cured to obtain a spinning solution with a viscosity of 30 Pa·s. This solution was then pumped into a spinning box and extruded through a spinneret with 80 spinneret holes. The filaments were cured in a spinning tunnel filled with nitrogen at 275°C at a gas flow rate of 0.2 m / s and a winding speed of 700 m / min, resulting in a high-performance flame-retardant spandex filament with a strength of 1.83 cN / dtex, an elongation at break of 330%, and a limiting oxygen index of 31.5%.

[0045] Example 3

[0046] This embodiment describes a high-performance flame-retardant spandex fiber and its preparation method, with the following steps:

[0047] Polypropylene glycol and 4,4'-methylenebis(phenyl isocyanate) were added to a prepolymer reactor at a molar ratio of 1:2.0 and reacted at high speed at 70°C for 90 min to prepare a prepolymer, which was then transferred to a final polymerization reactor. Next, phosphorus-containing dihydroxy compound DOPO-HQ and nitrogen-containing dihydroxy compound HPIMP were dissolved in N,N-dimethylformamide solution (DMF) at a molar ratio of 7:3, with the DMF amount being 4 times that of the dihydroxy compounds. 0.1 wt% of dibutyltin sulfide catalyst was added, and the solution was transferred to the final polymerization reactor (the total amount of DOPO-HQ and HPIMP was 3 / 7 of the amount of polypropylene glycol). The mixture was reacted with the prepolymer at 50°C for 20 min to obtain a low molecular weight polyurethane containing phosphorus in its molecular chain. Finally, 30 mol% of diisocyanate chain extenders butanediamine and N,N-dihydroxyethyl-diethyl... Phosphate ester (DEPHA) (in a ratio of 2:8) and auxiliary agents, including light stabilizer 622, antioxidant 168, and antibacterial quaternary ammonium salt, were dissolved and dispersed in a polar amine solution (auxiliary agent dosage was 1 wt%). This solution was added to the final polymerization reactor via a 5-position injection method and reacted at 80°C for 30 min to extend the chain of the phosphorus-containing prepolymer, yielding a phosphorus-containing polyurethane urea solution with a weight-average molecular weight of 131,000. Finally, the phosphorus-containing polyurethane urea solution was cured to obtain a spinning solution with a viscosity of 33 Pa·s. This solution was then pumped into a spinning box and extruded through a spinneret with 100 spinneret holes. The filaments were cured in a spinning tunnel filled with nitrogen at 235°C at a gas flow rate of 0.9 m / s and a winding speed of 800 m / min, resulting in a high-performance flame-retardant spandex filament with a strength of 1.76 cN / dtex, an elongation at break of 360%, and a limiting oxygen index of 31.1%.

[0048] Example 4

[0049] This embodiment describes a high-performance flame-retardant spandex fiber and its preparation method, with the following steps:

[0050] Polybutylene succinate diol and 4,4'-methylenebis(phenyl isocyanate) were added to a prepolymer reactor at a molar ratio of 1:2.1 and reacted at high speed at 65°C for 95 min to prepare a prepolymer, which was then transferred to a final polymerization reactor. Next, phosphorus-containing dihydroxy compound MH-PPOA and nitrogen-containing dihydroxy compound HPIMP were dissolved in N,N-dimethylacetamide solution (DMAC) at a molar ratio of 6:4, with the DMAC amount being 3.5 times that of the dihydroxy compounds. 0.15 wt% of stannous octoate catalyst was added, and the solution was transferred to the final polymerization reactor (the total amount of MH-PPOA and HPIMP was 2 / 3 of that of polybutylene succinate diol). The mixture was reacted with the prepolymer at 45°C for 25 min to obtain a low molecular weight polyurethane containing phosphorus in its molecular chain. Finally, cyclohexanediamine and N,N-dimethylacetamide (40 mol% diisocyanate chain extender) were added. Hydroxyethyl-diethyl phosphate (DEPHA) (in a ratio of 8:2) and additives including light stabilizer 292, antioxidant 1010, and antibacterial agent chitosan were dissolved and dispersed in a polar amine solution (additive dosage 1.5 wt%). This solution was then added to the final polymerization reactor via a 5-position injection method. The phosphorus-containing prepolymer was chain-extended at 60°C for 70 min to obtain a phosphorus-containing polyurethane urea solution with a weight-average molecular weight of 135,000. Finally, the phosphorus-containing... After aging, the polyurethane urea solution yields a spinning solution with a viscosity of 36 Pa·s. This solution is then pumped into the spinning box via a metering pump and extruded through a spinneret with 120 spinneret holes. The filaments are cured in a spinning tunnel filled with nitrogen at 255°C at a gas flow rate of 0.8 m / s and a winding speed of 900 m / min. This process produces a high-performance flame-retardant spandex filament with a strength of 1.66 cN / dtex, an elongation at break of 390%, and a limiting oxygen index of 32.5%.

[0051] Example 5

[0052] This embodiment describes a high-performance flame-retardant spandex fiber and its preparation method, with the following steps:

[0053] Polybutylene adipate diol and 4,4'-methylenebis(phenyl isocyanate) were added to a prepolymer reactor at a molar ratio of 1:2.2 and reacted at high speed at 60°C for 100 min to prepare a prepolymer, which was then transferred to a final polymerization reactor. Next, phosphorus-containing dihydroxy compound DOPO-HQ and nitrogen-containing dihydroxy compound NBP6 were dissolved in N,N-dimethylformamide solution (DMF) at a molar ratio of 5:5, with the DMF amount being 4.5 times that of the dihydroxy compounds. 0.2 wt% of dibutyltin dilaurate catalyst was added, and the mixture was transferred to the final polymerization reactor (the total amount of DOPO-HQ and NBP6 was equal to that of polybutylene adipate diol). The mixture was reacted with the prepolymer at 40°C for 30 min to obtain a low molecular weight polyurethane containing phosphorus in its molecular chain. Finally, a chain extender of 45 mol% diisocyanate, p-phenylenediamine, and N,N-di... Hydroxyethyl-diethyl phosphate (DEPHA) (in a ratio of 3:7) and auxiliary agents, including light stabilizer 119, antioxidant 168, and antibacterial agent chitosan, were dissolved and dispersed in a polar amine solution (auxiliary agent dosage: 2wt%). This solution was added to the final polymerization reactor via a 3-position injection method and reacted at 70°C for 60 min to extend the chain of the phosphorus-containing prepolymer, yielding a phosphorus-containing polyurethane urea solution with a weight-average molecular weight of 115,000. Finally, the phosphorus-containing polyurethane urea solution was cured to obtain a spinning solution with a viscosity of 39 Pa·s. This solution was then pumped into a spinning box and extruded through a spinneret with 140 spinneret holes. The filaments were solidified in a spinning tunnel filled with nitrogen at 245°C at a gas flow rate of 0.3 m / s and a winding speed of 1000 m / min, resulting in a high-performance flame-retardant spandex filament with a strength of 1.59 cN / dtex, an elongation at break of 440%, and a limiting oxygen index of 33.2%.

[0054] Example 6

[0055] This embodiment describes a high-performance flame-retardant spandex fiber and its preparation method, with the following steps:

[0056] Polybutylene sebacic acid diol and 4,4'-methylenebis(phenyl isocyanate) were added to a prepolymer reactor at a molar ratio of 1:2.3 and reacted at high speed at 75°C for 82 min to prepare a prepolymer, which was then transferred to a final polymerization reactor. Next, phosphorus-containing dihydroxy compound MH-PPOA and nitrogen-containing dihydroxy compound NBP6 were dissolved in N,N-dimethylacetamide solution (DMAC) at a molar ratio of 4:6, with the DMAC amount being 3 times that of the dihydroxy compounds. 0.25 wt% of dibutyltin sulfide catalyst was added, and the solution was transferred to the final polymerization reactor (the total amount of MH-PPOA and NBP6 was 2 / 3 of that of polybutylene sebacic acid diol). The mixture was reacted with the prepolymer at 35°C for 25 min to obtain a low molecular weight polyurethane containing phosphorus in its molecular chain. Finally, ethylenediamine and N,N-dihydroxyacetamide (50 mol% diisocyanate chain extender) were added. Diethyl phosphate (DEPHA) (in a ratio of 7:3) and auxiliary agents, including light stabilizer 622, antioxidant 1010, and antibacterial agent zinc oxide, were dissolved and dispersed in a polar amine solution (auxiliary agent dosage: 2.5 wt%). This solution was added to the final polymerization reactor via a 3-position injection method and reacted at 50°C for 90 min to extend the chain of the phosphorus-containing prepolymer, yielding a phosphorus-containing polyurethane urea solution with a weight-average molecular weight of 136,000. Finally, the phosphorus-containing polyurethane urea solution was cured to obtain a spinning solution with a viscosity of 40 Pa·s. This solution was then pumped into a spinning box and extruded through a spinneret with 160 spinneret holes. The filaments were solidified in a spinning tunnel filled with nitrogen at 270°C at a gas flow rate of 0.7 m / s and a winding speed of 1100 m / min, resulting in a high-performance flame-retardant spandex filament with a strength of 1.55 cN / dtex, an elongation at break of 485%, and a limiting oxygen index of 33.5%.

[0057] Example 7

[0058] This embodiment describes a high-performance flame-retardant spandex fiber and its preparation method, with the following steps:

[0059] Polytetrahydrofuran ether diol and 4,4'-methylenebis(phenyl isocyanate) were added to a prepolymer reactor at a molar ratio of 1:2.4 and reacted at high speed at 85°C for 87 min to prepare a prepolymer, which was then transferred to a final polymerization reactor. Next, phosphorus-containing dihydroxy compound MH-PPOA and nitrogen-containing dihydroxy compound HPIMP were dissolved in N,N-dimethylacetamide solution (DMF) at a molar ratio of 3:7, with the DMF amount being 4 times that of the dihydroxy compounds. 0.3 wt% of stannous octoate catalyst was added, and the solution was transferred to the final polymerization reactor (the total amount of MH-PPOA and HPIMP was equal to that of polytetrahydrofuran ether diol). The mixture was reacted with the prepolymer at 30°C for 30 min to obtain a low molecular weight polyurethane containing phosphorus in its molecular chain. Finally, 40 mol% of diisocyanate chain extender propylenediamine and N,N-dihydroxyethyl-diisocyanate were added. Ethyl phosphate (DEPHA) (in a ratio of 4:6) and auxiliary agents, including light stabilizer 292, antioxidant 1076, and antibacterial quaternary ammonium salt, were dissolved and dispersed in a polar amine solution (auxiliary agent dosage: 2.7 wt%). This solution was added to the final polymerization reactor via a 3-position injection method and reacted at 70°C for 30 min to extend the chain of the phosphorus-containing prepolymer, yielding a phosphorus-containing polyurethane urea solution with a weight-average molecular weight of 134,000. Finally, the phosphorus-containing polyurethane urea solution was cured to obtain a spinning solution with a viscosity of 38 Pa·s. This solution was then pumped into a spinning box and extruded through a spinneret with 300 spinneret holes. The filaments were solidified in a spinning tunnel filled with nitrogen at 230°C at a gas flow rate of 1 m / s and a winding speed of 1500 m / min, resulting in a high-performance flame-retardant spandex filament with a strength of 1.49 cN / dtex, an elongation at break of 640%, and a limiting oxygen index of 33.9%.

[0060] Example 8

[0061] This embodiment describes a high-performance flame-retardant spandex fiber and its preparation method, with the following steps:

[0062] Polyethylene glycol and 4,4'-methylenebis(phenyl isocyanate) were added to a prepolymer reactor at a molar ratio of 1:2.5 and reacted at high speed at 60°C for 100 min to prepare a prepolymer, which was then transferred to a final polymerization reactor. Next, phosphorus-containing dihydroxy compound DOPO-HQ and nitrogen-containing dihydroxy compound NBP6 were dissolved in N,N-dimethylformamide solution (DMAC) at a molar ratio of 2:8, with the DMAC amount being 5 times that of the dihydroxy compounds. 0.35 wt% of dibutyltin dilaurate catalyst was added, and the solution was transferred to the final polymerization reactor (the total amount of DOPO-HQ and NBP6 was 3 / 7 of the amount of polyethylene glycol). The mixture was reacted with the prepolymer at 30°C for 25 min to obtain a low molecular weight polyurethane containing phosphorus in its molecular chain. Finally, 35 mol% of diisocyanate chain extender butanediamine and N,N-dihydroxyethyl... Diethyl phosphate (in a 5:5 ratio) and additives such as light stabilizer 622, antioxidant 1076, and antibacterial agent chitosan are dissolved and dispersed in a polar amine solution (additive dosage is 3 wt%). This solution is then added to the final polymerization reactor via a 4-position injection method. The phosphorus-containing prepolymer is chain-extended at 50°C for 90 min to obtain a phosphorus-containing polyurethane urea solution with a weight-average molecular weight of 142,000. Finally, the phosphorus-containing polyurethane urea solution is cured to obtain a spinning solution with a viscosity of 50 Pa·s. This solution is then pumped into the spinning box and extruded through a spinneret with 180 spinneret holes. The filaments are solidified in a spinning tunnel filled with nitrogen at 265°C at a gas flow rate of 0.4 m / s and a winding speed of 1400 m / min, resulting in a high-performance flame-retardant spandex filament with a strength of 1.45 cN / dtex, an elongation at break of 660%, and a limiting oxygen index of 32.5%.

[0063] Example 9

[0064] This embodiment describes a high-performance flame-retardant spandex fiber and its preparation method, with the following steps:

[0065] Polypropylene glycol and 4,4'-methylenebis(phenyl isocyanate) were added to a prepolymer reactor at a molar ratio of 1:2.15 and reacted at 55°C with high-speed stirring for 90 min to prepare a prepolymer, which was then transferred to a final polymerization reactor. Next, phosphorus-containing dihydroxy compound MH-PPOA and nitrogen-containing dihydroxy compound HPIMP were dissolved in N,N-dimethylformamide solution (DMF) at a molar ratio of 1:9, with the DMF amount being 4.5 times that of the dihydroxy compounds. 0.4 wt% of dibutyltin sulfide catalyst was added, and the solution was transferred to the final polymerization reactor (the total amount of MH-PPOA and HPIMP was 1 / 4 of that of polypropylene glycol). The mixture was reacted with the prepolymer at 35°C for 20 min to obtain a low molecular weight polyurethane containing phosphorus in its molecular chain. Finally, cyclohexanediamine and N,N-dihydroxyethyl-diethyl chain extenders (20 mol% of diisocyanate) were added. Phosphate ester (DEPHA) (in a ratio of 6:4) and auxiliary agents, including light stabilizer 292, antioxidant 168, and antibacterial agent zinc oxide, were dissolved and dispersed in a polar amine solution (auxiliary agent dosage: 2.2 wt%). This solution was added to the final polymerization reactor via a 3-position injection method and reacted at 70°C for 40 min to extend the chain of the phosphorus-containing prepolymer, yielding a phosphorus-containing polyurethane urea solution with a weight-average molecular weight of 132,000. Finally, the phosphorus-containing polyurethane urea solution was cured to obtain a spinning solution with a viscosity of 35 Pa·s. This solution was then pumped into a spinning box and extruded through a spinneret with 200 spinneret holes. The filaments were cured in a spinning tunnel filled with nitrogen at 260°C at a gas flow rate of 0.6 m / s and a winding speed of 1300 m / min, resulting in a high-performance flame-retardant spandex filament with a strength of 1.40 cN / dtex, an elongation at break of 700%, and a limiting oxygen index of 34.2%.

[0066] Example 10

[0067] This embodiment describes a high-performance flame-retardant spandex fiber and its preparation method, with the following steps:

[0068] Polybutylene succinate diol and 4,4'-methylenebis(phenyl isocyanate) were added to a prepolymer reactor at a molar ratio of 1:2.45 and reacted at high speed at 80°C for 95 min to prepare a prepolymer, which was then transferred to a final polymerization reactor. Next, phosphorus-containing dihydroxy compound DOPO-HQ and nitrogen-containing dihydroxy compound NBP6 were dissolved in N,N-dimethylacetamide solution (DMAC) at a molar ratio of 1:9, with the DMAC amount being 3.5 times that of the dihydroxy compounds. 0.45 wt% of stannous octoate catalyst was added, and the solution was transferred to the final polymerization reactor (the total amount of DOPO-HQ and NBP6 was 1 / 4 of the amount of polybutylene succinate diol). The mixture was reacted with the prepolymer at 40°C for 15 min to obtain a low molecular weight polyurethane containing phosphorus in its molecular chain. Finally, a chain extender p-phenylenediamine and N,N-dihydroxyacetamide (50 mol% diisocyanate) were added. Ethyl-diethyl phosphate (DEPHA) (in a ratio of 7:3) and additives, including light stabilizer 622, antioxidant 1010, and antibacterial quaternary ammonium salt, were dissolved and dispersed in a polar amine solution (additive dosage: 1.7 wt%). This solution was then added to the final polymerization reactor via a 3-position injection method. The phosphorus-containing prepolymer was chain-extended at 60°C for 50 min to obtain a phosphorus-containing polyurethane urea solution with a weight-average molecular weight of 139,000. Finally, the phosphorus-containing polyurethane... After aging, the urea urethane solution yields a spinning solution with a viscosity of 48 Pa·s. This solution is then pumped into the spinning box and extruded through a spinneret with 220 spinneret holes. The filaments are solidified in a spinning tunnel filled with nitrogen at 240°C with a gas flow rate of 0.5 m / s and a winding speed of 1250 m / min. This process produces a high-performance flame-retardant spandex filament with a strength of 1.45 cN / dtex, an elongation at break of 660%, and a limiting oxygen index of 30.5%.

[0069] Example 11

[0070] This embodiment describes a high-performance flame-retardant spandex fiber and its preparation method, with the following steps:

[0071] Polybutylene adipate diol and 4,4'-methylenebis(phenyl isocyanate) were added to a prepolymer reactor at a molar ratio of 1:2.35 and reacted at high speed at 70°C for 92 min to prepare a prepolymer, which was then transferred to a final polymerization reactor. Next, phosphorus-containing dihydroxy compound DOPO-HQ and nitrogen-containing dihydroxy compound NBP6 were dissolved in N,N-dimethylacetamide solution (DMF) at a molar ratio of 9:1, with the DMF amount being 3 times that of the dihydroxy compounds. 0.5 wt% of dibutyltin dilaurate catalyst was added, and the solution was transferred to the final polymerization reactor (the total amount of DOPO-HQ and NBP6 was 3 / 7 of the amount of polybutylene adipate diol). The mixture was reacted with the prepolymer at 45°C for 10 min to obtain a low molecular weight polyurethane containing phosphorus in its molecular chain. Finally, ethylenediamine and N,N-dihydroxyacetamide (22.5 mol% diisocyanate chain extender) were added. Ethyl-diethyl phosphate (DEPHA) (in a ratio of 3:7) and additives, including light stabilizer 292, antioxidant 168, and antibacterial quaternary ammonium salt, were dissolved and dispersed in a polar amine solution (additive dosage: 1.2 wt%). This solution was then added to the final polymerization reactor via a 5-position injection method. The phosphorus-containing prepolymer was chain-extended at 90°C for 30 min to obtain a phosphorus-containing polyurethane urea solution with a weight-average molecular weight of 136,000. Finally, the phosphorus-containing polyurethane... After aging, the urea ester solution yields a spinning solution with a viscosity of 45 Pa·s. This solution is then pumped into the spinning box via a metering pump and extruded through a spinneret with 240 spinneret holes. The filaments are solidified in a spinning tunnel filled with nitrogen at 245°C with a gas flow rate of 0.15 m / s and a winding speed of 1350 m / min. This process produces a high-performance flame-retardant spandex filament with a strength of 1.75 cN / dtex, an elongation at break of 210%, and a limiting oxygen index of 34.6%.

[0072] Example 12

[0073] This embodiment describes a high-performance flame-retardant spandex fiber and its preparation method, with the following steps:

[0074] Polybutylene sebacic acid diol and 4,4'-methylenebis(phenyl isocyanate) were added to a prepolymer reactor at a molar ratio of 1:2.25 and reacted at 60°C with high-speed stirring for 95 min to prepare a prepolymer, which was then transferred to a final polymerization reactor. Next, phosphorus-containing dihydroxy compound MH-PPOA and nitrogen-containing dihydroxy compound HPIMP were dissolved in N,N-dimethylformamide solution (DMAC) at a molar ratio of 5:5, with the DMAC amount being 4.5 times that of the dihydroxy compounds. 0.5 wt% of dibutyltin sulfide catalyst was added, and the solution was transferred to the final polymerization reactor (the total amount of DOPO-HQ and HPIMP was 2 / 3 of the amount of polybutylene sebacic acid diol). The mixture was reacted with the prepolymer at 50°C for 15 min to obtain a low molecular weight polyurethane containing phosphorus in its molecular chain. Finally, 40 mol% of diisocyanate chain extender propylenediamine and N,N-dimethylformamide were added. Ethyl-diethyl phosphate (DEPHA) (in a ratio of 4:6) and additives, including light stabilizer 622, antioxidant 1010, and antibacterial agent zinc oxide, were dissolved and dispersed in a polar amine solution (additive dosage: 0.7 wt%). This solution was then added to the final polymerization reactor via a 3-position injection method. The phosphorus-containing prepolymer was chain-extended at 60°C for 40 min to obtain a phosphorus-containing polyurethane urea solution with a weight-average molecular weight of 131,000. Finally, the phosphorus-containing polyurethane... After aging, the urea ester solution yields a spinning solution with a viscosity of 34.5 Pa·s. This solution is then pumped into the spinning box via a metering pump and extruded through a spinneret with 260 spinneret holes. The filaments are solidified in a spinning tunnel filled with nitrogen at 250°C at a gas flow rate of 0.55 m / s and a winding speed of 1450 m / min. This process produces a high-performance flame-retardant spandex filament with a strength of 1.6 cN / dtex, an elongation at break of 480%, and a limiting oxygen index of 34.8%.

[0075] Comparative Example 1

[0076] Polytetrahydrofuran ether diol and 4,4'-methylenebis(phenyl isocyanate) were added to a prepolymer reactor at a molar ratio of 1:1.5 and reacted at high speed at 90°C for 80 min to prepare a prepolymer, which was then transferred to a final polymerization reactor. Next, chain extender ethylenediamine, N,N-dihydroxyethyl-diethyl phosphate (DEPHA) (in a molar ratio of 1:9), and additives light stabilizer 119, antioxidant 1067, and antibacterial quaternary ammonium salt were dissolved and dispersed in a polar amine N,N-dimethylformamide (DMF) solution (the amount of DMF was 3 times that of polytetrahydrofuran ether diol, and the additives...). Using 0.1 wt%, the prepolymer was chain extended in the final polymerization reactor to obtain a polyurethane urea solution with a weight-average molecular weight of 62,000. Finally, the polyurethane urea solution was aged to obtain a spinning solution with a viscosity of 3-5 Pa·s, which was then pumped into the spinning box and extruded through a spinneret with 60 spinneret holes. The filaments were solidified in a spinning tunnel filled with nitrogen at 280°C with a gas flow rate of 0.1 m / s and a winding speed of 600 m / min, resulting in spandex filaments with a strength of 1.2 cN / dtex, an elongation at break of 560%, and a limiting oxygen index of 19.7%.

[0077] In Comparative Example 1, the molecular structure and chain extension method of conventional spandex were used. Because its molecular chain did not contain aromatic phosphorus-nitrogen diol compounds, its elongation at break was greater than 500%, its elasticity was high, but its breaking strength was only 1.2 cN / dtex, and its limiting oxygen index was only 19.27%, thus lacking flame retardant properties. In contrast, this invention, through molecular structure design, introduces aromatic phosphorus-containing flame-retardant units, achieving a significant increase in the limiting oxygen index of spandex fiber (29-35%) while also effectively improving its mechanical properties (1.4-1.9 cN / dtex), resulting in high-performance flame-retardant spandex fiber.

[0078] Comparative Example 2

[0079] Polytetrahydrofuran ether diol and 4,4'-methylenebis(phenyl isocyanate) were added to a prepolymer reactor at a molar ratio of 1:1.5 and reacted at 90°C with high-speed stirring for 80 min to prepare a prepolymer, which was then transferred to a final polymerization reactor. Next, a phosphorus-containing dihydroxy compound, DOPO-HQ, was dissolved in N,N-dimethylformamide (DMF) solution (3.5 times the amount of the dihydroxy compound), and 0.01 wt% of stannous octoate catalyst was added. This solution was then transferred to the final polymerization reactor (DOPO-HQ was 1 / 4 the amount of polytetrahydrofuran ether diol) and reacted with the prepolymer at 60°C for 10 min to obtain a low molecular weight polyurethane containing phosphorus in its molecular chain. Finally, ethylenediamine (20 mol% diisocyanate), N,N-dihydroxyethyl-diethyl phosphate (DEPH) and other chain extenders were added. A) (in a ratio of 1:9) and auxiliary agents, light stabilizer 119, antioxidant 1067, and antibacterial quaternary ammonium salt, are dissolved and dispersed in a polar amine solution (auxiliary agent dosage is 0.1 wt%). This solution is added to the final polymerization reactor via a 3-position injection method and reacted at 40°C for 60 min to extend the chain of the phosphorus-containing prepolymer, resulting in a phosphorus-containing polyurethane urea solution with a weight-average molecular weight of 99,000. Finally, the phosphorus-containing polyurethane urea solution is cured to obtain a spinning solution with a viscosity of 20 Pa·s. This solution is then pumped into the spinning box and extruded through a spinneret with 60 spinneret holes. The filaments are solidified in a spinning tunnel filled with nitrogen at 280°C with a gas flow rate of 0.1 m / s and a winding speed of 600 m / min, resulting in flame-retardant spandex filaments with a strength of 1.42 cN / dtex, an elongation at break of 450%, and a limiting oxygen index of 27.2%.

[0080] Comparative Example 3

[0081] Polytetrahydrofuran ether diol and 4,4'-methylenebis(phenyl isocyanate) were added to a prepolymer reactor at a molar ratio of 1:1.5 and reacted at 90°C with high-speed stirring for 80 min to prepare a prepolymer, which was then transferred to a final polymerization reactor. Next, a nitrogen-containing dihydroxy compound, HPIMP, was dissolved in N,N-dimethylformamide solution (DMF), with the DMF amount being 3.5 times that of the dihydroxy compound. 0.01 wt% of stannous octoate catalyst was added, and the mixture was transferred to the final polymerization reactor (DOPO-HQ was added at 1 / 4 the amount of polytetrahydrofuran ether diol). The mixture was reacted with the prepolymer at 60°C for 10 min to obtain a low molecular weight polyurethane containing phosphorus in its molecular chain. Finally, ethylenediamine (a chain extender at 20 mol% diisocyanate) and N,N-dihydroxyethyl-diethyl phosphate (N,N-dihydroxyethyl-diethyl phosphate) were added. DEPHA (in a 1:9 ratio) and additives, including light stabilizer 119, antioxidant 1067, and antibacterial quaternary ammonium salt, are dissolved and dispersed in a polar amine solution (additive dosage: 0.1 wt%). This solution is then added to the final polymerization reactor via a 3-position injection method. The prepolymer is chain-extended at 40°C for 60 min to obtain a polyurethane urea solution with a weight-average molecular weight of 872,000. Finally, the polyurethane urea solution is cured to obtain a spinning solution with a viscosity of 12 Pa·s. This solution is then pumped into the spinning box and extruded through a spinneret with 60 spinneret holes. The filaments are solidified in a spinning tunnel filled with nitrogen at 280°C at a gas flow rate of 0.1 m / s and a winding speed of 600 m / min, resulting in flame-retardant spandex filaments with a strength of 1.36 cN / dtex, an elongation at break of 526%, and a limiting oxygen index of 22.6%.

[0082] In Comparative Examples 2 and 3, phosphorus-containing dihydroxy compound DOPO-HQ and nitrogen-containing dihydroxy compound were introduced into the molecular chain, respectively. It can be seen that compared with conventional spandex (Comparative Example 1), the introduction of phosphorus- and nitrogen-containing dihydroxy compounds can improve the flame retardancy and mechanical properties of spandex fibers, but the effect is not significant and is far inferior to the performance of spandex fibers in Example 1. Simultaneous introduction of phosphorus- and nitrogen-containing dihydroxy compounds can fully utilize the high-temperature crosslinking of C=N and N=N bonds and the synergistic flame-retardant properties of P and N, effectively enhancing the intermolecular chain forces and flame-retardant properties, achieving a balance between mechanical and flame-retardant properties.

[0083] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing high-performance flame-retardant spandex fiber, characterized in that, Includes the following steps: (1) The polydiol and diisocyanate were mixed and then prepolymerized to obtain the prepolymer; (2) Dissolve phosphorus-containing dihydroxy compounds, nitrogen-containing dihydroxy compounds and catalysts in a polar amide solution to prepare a mixed solution. Mix the mixed solution with the prepolymer and carry out a polymerization reaction to obtain a low molecular weight polyurethane containing phosphorus in the molecular chain. (3) After mixing low molecular weight polyurethane with a chain extender, a chain extension reaction is carried out to obtain a phosphorus-containing polyurethane urea solution; (4) After the phosphorus-containing polyurethane urea solution is cured, it is spun to obtain high-performance flame-retardant spandex yarn; The polar amide solution is N,N-dimethylformamide or N,N-dimethylacetamide; The chain extender comprises a diamine and a diol, and its amount is 20-50 mol% of the diisocyanate; the molar ratio of the diamine and the diol is (1:9)-(9:1); the diamine is one of ethylenediamine, propylenediamine, butylenediamine, cyclohexanediamine, and p-phenylenediamine; the diol is N,N-dihydroxyethyl-diethyl phosphate. The molar ratio of the polydiol to the diisocyanate is 1:(1.8-2.5); the temperature of the prepolymerization reaction is 60-90℃ and the time is 80-100 min; The phosphorus-containing dihydroxy compound is one of the following structures: ； The nitrogen-containing dihydroxy compound has one of the following structures: ； The molar ratio of the phosphorus-containing dihydroxy compound and the nitrogen-containing dihydroxy compound is (1:9) to (9:1), and the molar ratio of the total amount of the two compounds to the polydiol is (1:9) to (5:5).

2. The method for preparing high-performance flame-retardant spandex fiber according to claim 1, characterized in that, The polydiol is a polyether diol or a polyester diol with a molecular weight of 1000-3000; the polyether diol is one of polytetrahydrofuran ether diol, polyethylene glycol, and polypropylene glycol; the polyester diol is one of polybutylene succinate diol, polybutylene adipate diol, and polybutylene sebacate diol.

3. The method for preparing high-performance flame-retardant spandex fiber according to claim 1, characterized in that, The polymerization reaction is carried out at a temperature of 30-60℃ for a time of 10-30 minutes.

4. The method for preparing high-performance flame-retardant spandex fiber according to claim 1, characterized in that, The catalyst is stannous octoate, dibutyltin dilaurate, or dibutyltin sulfide, and its amount is 0.01-0.5 wt% of the total mass of phosphorus-containing dihydroxy compounds and nitrogen-containing dihydroxy compounds; the amount of the polar amide solution is 3-5 times the total mass of phosphorus-containing dihydroxy compounds.

5. The method for preparing high-performance flame-retardant spandex fiber according to claim 1, characterized in that, The chain extension reaction is carried out at a temperature of 40-80℃ for a time of 30-90 minutes.

6. The method for preparing high-performance flame-retardant spandex fiber according to any one of claims 1-5, characterized in that, The phosphorus-containing polyurethane urea solution in step (3) also contains an auxiliary agent, the amount of which is 0.1-3 wt% of the total mass of the phosphorus-containing polyurethane urea solution; the auxiliary agent includes any one or more of light stabilizers, antioxidants, and antibacterial agents.

7. The high-performance flame-retardant spandex fiber prepared by the method according to any one of claims 1-6, characterized in that, Weight-average molecular weight greater than 90,000, tensile strength greater than 1.3 cN / dtex, limiting oxygen index greater than 30%.

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