High-toughness flame-retardant yarn as well as preparation method and application thereof

Abstract

The invention provides a high-toughness flame-retardant yarn and a preparation method and application thereof, and belongs to the technical field of textile materials. High-strength filaments are used as core yarns, flame-retardant staple fiber yarns are used as skin layers to prepare skin-core yarns, the skin-core yarns are pre-brushed, the skin-core yarns are soaked and rolled twice in water-based flame-retardant finishing liquid containing chitosan quaternary ammonium salt derivatives, citric acid polyol ester and organic silicon softeners, and the finished yarns are prepared through pre-drying and heat setting. According to the invention, the skin-core structure design is matched with the process of the bio-based flame-retardant finishing liquid, so that the balance between flame retardance and high toughness is realized, and the flame retardance is still excellent after water washing; the yarn is small in color difference, good in air permeability, free of formaldehyde, low in smoke density grade and capable of meeting the harsh standard of vehicle interior cloth. The process does not need special equipment, no toxic solvent is released, the production cost is low, and the prepared yarn can be widely applied to the fields of flame-retardant curtains, sofa fabrics, curtains, traffic interior fabrics and the like, and has a good industrialization prospect.

Description

Technical Field

[0001] This invention relates to the field of textile materials technology, and in particular to a high-toughness flame-retardant yarn, its preparation method, and its application. Background Technology

[0002] Flame-retardant decorative fabrics are core textile materials used in public places such as hotels, shopping malls, rail transit, and home settings. Flame-retardant safety is a basic performance requirement, while performance characteristics such as hand feel, breathability, color aesthetics, and durability must also be taken into account. Furthermore, the market demand for large-scale, multi-variety, and low-cost industrialization of flame-retardant decorative fabrics is increasing. Currently, the industry's flame-retardant treatment for flame-retardant decorative fabrics mainly focuses on post-fabric finishing, which involves first weaving a basic fabric and then applying flame retardant to achieve a flame-retardant effect. While this process is simple to operate and achieves initial flame-retardant results, it has several intractable technical drawbacks: First, the applied flame retardant tends to form a thick film on the fabric surface, resulting in a stiff feel and significantly reduced breathability. Furthermore, the bond between the flame retardant and the fiber is merely a simple physical adhesion, making it prone to detachment during subsequent washing and daily friction, resulting in insufficient flame-retardant durability and potential safety hazards with long-term use. Second, most existing high-efficiency flame retardants are chemically synthesized, which have poor compatibility with dyes, easily affecting the dyeing effect and causing the fabric to appear dull and have reduced colorfastness. Some flame retardants also have inherent colors, severely limiting the freedom of color matching and pattern design in flame-retardant decorative fabrics and making it difficult to meet the aesthetic requirements of decorative fabrics.

[0003] To address the shortcomings of the aforementioned fabric finishing processes, some technical solutions attempt to add functional masterbatches or auxiliaries to the spinning raw materials, achieving flame-retardant properties in the yarn through integrated spinning, while simultaneously adding multiple functions such as high strength and antibacterial properties. However, to achieve this high-performance combination, such solutions often require the addition of large quantities of expensive flame-retardant and antibacterial functional masterbatches, significantly increasing raw material costs. Furthermore, the addition of functional masterbatches and the spinning process require specific high-temperature polymerization spinning equipment, resulting in complex processes, high energy consumption, poor production flexibility, difficulty in quickly adjusting product performance according to market demand, limited capacity expansion, and an inability to meet the large-scale, multi-variety production needs of the flame-retardant decorative fabric market.

[0004] Meanwhile, existing flame-retardant fibers have inherent performance defects. Most high-efficiency flame-retardant fibers are brittle and have low breaking strength, resulting in yarns with poor tear resistance. Fabrics made from these fibers are prone to damage and pilling. Simply increasing the amount of flame-retardant fibers to improve strength will further exacerbate the problem of stiff fabric feel, making it difficult to balance the relationship between flame retardancy, toughness, and feel. In addition, the functional modification layers of existing yarns are mostly chemically synthesized coatings, which have poor cross-linking effects with fibers and easily cover the color of the fiber itself. Furthermore, some coating preparation processes release toxic solvents, which is neither environmentally friendly nor in line with the trend of green production of textile materials.

[0005] In summary, the industry urgently needs a flame-retardant yarn preparation technology that balances flame retardancy, safety, high toughness, aesthetics, and durability. This technology needs to address issues such as easy detachment of flame retardants, poor hand feel, and limited color options in traditional flame-retardant processing, while reducing production costs, energy consumption, and improving production flexibility. Simultaneously, it should achieve a high-efficiency combination of flame retardancy with high strength and antibacterial properties to meet the application needs of flame-retardant decorative fabrics in various scenarios and drive technological upgrades in the flame-retardant decorative fabric industry. Summary of the Invention

[0006] The purpose of this invention is to provide a high-toughness flame-retardant yarn, its preparation method, and its application, in order to solve the above-mentioned technical problems.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing high-toughness flame-retardant yarn, comprising the following steps: Step 1) Mix the chitosan quaternary ammonium salt derivative aqueous solution, crosslinking agent and softener to obtain flame retardant finishing liquid; Step 2) After the flame-retardant short fiber yarn is combed and drawn, it is covered with high-strength filament as the core yarn to obtain core-sheath yarn; Step 3) After pre-cleaning and brushing the core yarn, dip and rub it twice in the flame retardant finishing solution, then pre-dry and heat set in sequence, and obtain high-toughness flame retardant yarn after natural cooling.

[0008] Furthermore, in step 1), the flame retardant finishing liquid contains, by mass, 5-10 parts of chitosan quaternary ammonium salt derivative, 2-5 parts of crosslinking agent, 1-3 parts of softener, and the remainder is water. The crosslinking agent is citric acid polyol ester, and the softener is an organosilicon softener; The solid content of the flame-retardant finishing liquid is 10~20wt%.

[0009] Furthermore, in step 1), the mixing is carried out under stirring conditions, with a stirring temperature of 25~30℃, a stirring time of 15~20min, and a stirring speed of 300~500r / min.

[0010] Furthermore, in step 2), the high-strength filament includes aramid or high-strength polyester, with a linear density ranging from 100 to 500D. The flame-retardant staple fiber yarn includes flame-retardant acrylic or flame-retardant polyester staple fiber, with a fiber length of 38~51mm and a fineness of 1.5~3.0D.

[0011] Furthermore, in step 2), the coating is performed using ring spinning or Siro spinning processes, with a coating rate ≥85%, a twist of 600~900T / m, and a twist coefficient α of 120~140.

[0012] Furthermore, in step 3), during the two dips and two rolls, the dip time for each dip is 30-60 seconds, and the roll residue after dip and roll is 50-60%.

[0013] Furthermore, in step 3), the pre-baking temperature is 60~70℃, and the pre-baking time is 3~5 minutes; The heat setting temperature is 120~150℃, and the heat setting time is 2~4 minutes.

[0014] This invention provides a high-toughness flame-retardant yarn prepared by the above-described preparation method.

[0015] The present invention also provides an application of the above-mentioned high-toughness flame-retardant yarn in the preparation of flame-retardant decorative fabrics, the flame-retardant decorative fabrics including flame-retardant curtains, sofa fabrics, curtains and vehicle interior fabrics.

[0016] The beneficial effects of this invention are: The high-toughness flame-retardant yarn prepared by this invention, through its core-sheath structure design and process adaptation to water-based bio-based flame-retardant finishing liquid, solves many technical defects of traditional flame-retardant yarns, resulting in significant comprehensive benefits: First, the core-sheath structure uses aramid / high-strength polyester filament as the core and flame-retardant staple fiber yarn as the sheath. Combined with precise spinning parameters, the finished yarn exhibits excellent mechanical properties, compensating for the brittleness of flame-retardant fibers. The dual flame-retardant design achieves a high balance between flame retardancy and toughness. Second, the water-based bio-based flame-retardant layer is firmly adhered after cross-linking, maintaining flame-retardant performance even after washing. Furthermore, the film does not obscure the fiber's natural color. Combined with silicone softener and secondary finishing, it balances fabric aesthetics, softness, and breathability, overcoming limitations in color design. Third, the outer functional film achieves superimposed functions such as flame retardancy and antibacterial properties, reducing the use of expensive functional masterbatches. The entire process involves no high-temperature polymerization and no toxic solvents, reducing raw material and energy costs. No specialized equipment is required; simply changing the yarn type and adjusting process parameters allows for the development of a series of products, enabling flexible and easily scalable production. Fourth, by adjusting the technical characteristics such as the ratio of flame-retardant finishing liquid and heat setting parameters, the finished yarn can achieve low smoke and low toxicity, meet the stringent standards for vehicle interior fabrics, and expand its application scenarios from hotel curtains and sofa fabrics to vehicle interiors, making it widely applicable; the entire process parameters are quantified, the quality control standards are clear, the product performance is stable, and it is easy to industrialize. Detailed Implementation

[0017] This invention provides a method for preparing high-toughness flame-retardant yarn, comprising the following steps: Step 1) Mix the chitosan quaternary ammonium salt derivative aqueous solution, crosslinking agent and softener to obtain flame retardant finishing liquid; Step 2) After the flame-retardant short fiber yarn is combed and drawn, it is covered with high-strength filament as the core yarn to obtain core-sheath yarn; Step 3) After pre-cleaning and brushing the core yarn, dip and rub it twice in the flame retardant finishing solution, then pre-dry and heat set in sequence, and obtain high-toughness flame retardant yarn after natural cooling.

[0018] In this invention, in step 1), the flame retardant finishing liquid contains, by mass, 5-10 parts of chitosan quaternary ammonium salt derivative, preferably 7-9 parts; 2-5 parts of crosslinking agent, preferably 3-4 parts; 1-3 parts of softener, preferably 2 parts; and the remainder is water. The crosslinking agent is citric acid polyol ester, and the softener is an organosilicon softener; The solid content of the flame-retardant finishing liquid is 10-20 wt%, preferably 13-16 wt%.

[0019] In this invention, the chitosan quaternary ammonium salt derivative includes one or more of O-(2-hydroxypropyltrimethylammonium chloride) chitosan, N-p-benzoxymethyl chitosan quaternary ammonium salt, N-p-phenylhydroxymethyl chitosan quaternary ammonium salt, O-(2-hydroxypropyltrimethylammonium chloride)-N-p-hydroxybenzoyl chitosan, (2-hydroxy-3-dimethylalkylammonium)propyl chitosan oligosaccharide, and N-(2-hydroxypropyl)trimethyl chitosan ammonium chloride.

[0020] In this invention, chitosan quaternary ammonium salt has broad-spectrum antibacterial properties, and the crosslinking agent fixes the antibacterial components to the fiber surface, thereby improving antibacterial durability.

[0021] In this invention, the citric acid polyol ester includes one or more of tributyl citrate, triethyl citrate, polyglycerol citrate, pentaerythritol citrate, tri(2-ethylhexyl) citrate, and polymeric citric acid polyol ester.

[0022] In this invention, chitosan quaternary ammonium salt derivatives form an expanded char layer when heated, which plays a role in heat insulation and oxygen barrier. Citric acid polyol ester crosslinking agent participates in the char formation reaction, promotes the densification of the char layer, and improves the strength of the char layer. The two work together to form a more uniform and denser flame retardant barrier.

[0023] In this invention, the silicone softener includes one or more of epoxy-modified silicone oil, silicone quaternary ammonium salt, amino silicone oil, terminal epoxy polyether silicone oil, and block polyether amino silicone oil.

[0024] In this invention, the crosslinking agent enables the chitosan quaternary ammonium salt to form a chemical bond with the fiber, and the flame retardant layer is firmly attached. The organosilicon softener can participate in the crosslinking reaction, which not only significantly improves the feel of the product, but also forms a three-dimensional network structure. The three work together to significantly improve the water resistance of the flame retardant layer.

[0025] In this invention, in step 1), the mixing is carried out under stirring conditions, the stirring temperature is 25~30℃, preferably 28℃; the stirring time is 15~20min, preferably 17min; and the stirring speed is 300~500r / min, preferably 350~450r / min.

[0026] In this invention, the pH of the flame-retardant finishing liquid is preferably 5.5 to 6.5, and the pH adjuster is a 10wt% citric acid aqueous solution.

[0027] In this invention, in step 2), the high-strength filament includes aramid or high-strength polyester, preferably high-strength polyester; the linear density ranges from 100 to 500D, preferably from 200 to 400D. The flame-retardant staple fiber yarn includes flame-retardant acrylic or flame-retardant polyester staple fiber, and the fiber length of the flame-retardant staple fiber yarn is 38~51mm, preferably 40~48mm; the fineness is 1.5~3.0D, preferably 2.0~2.5D.

[0028] In this invention, in step 2), the coating is performed using ring spinning or Siro spinning, preferably Siro spinning; the coating rate is preferably ≥85%; the twist is 600~900T / m, preferably 700~800T / m; and the twist coefficient α is 120~140, preferably 125~135.

[0029] In this invention, in step 3), the time for each immersion in the two dips and two rolls is 30-60 seconds, preferably 40 seconds; the roll residue after immersion and rolling is preferably 50-60%.

[0030] In this invention, in step 3), the pre-drying temperature is 60~70℃, preferably 62~68℃; the pre-drying time is 3~5min, preferably 4min; The heat setting temperature is 120~150℃, preferably 130~140℃; the heat setting time is 2~4min, preferably 3min.

[0031] This invention provides a high-toughness flame-retardant yarn prepared by the above-described preparation method.

[0032] The present invention also provides an application of the above-mentioned high-toughness flame-retardant yarn in the preparation of flame-retardant decorative fabrics, the flame-retardant decorative fabrics including flame-retardant curtains, sofa fabrics, curtains and vehicle interior fabrics.

[0033] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0034] Example 1

[0035] Take 7 parts of O-(2-hydroxypropyltrimethylammonium chloride) chitosan, 3 parts of tributyl citrate, 2 parts of amino silicone oil, and the remainder is water. Adjust the pH of the system to 5.5 and stir for 17 minutes at 28℃ and 350r / min to obtain a flame retardant finishing liquid with a solid content of 13wt%. High-strength polyester filament with a linear density of 200D was selected as the core yarn. After constant tension adjustment by a tensioner, the untwisted yarn was fed into the feed end of a Siro spinning machine. Flame-retardant polyester staple fiber yarn with a fiber length of 40mm and a fineness of 2.0D was taken and, after two carding processes and three drawing processes, produced a roving with a basis weight of 18g / 5m. This roving was fed into the Siro spinning machine in two parallel strands, symmetrically distributed on both sides of the core yarn. The core-sheath coating process was employed, with the spinning machine spindle speed set at 12000 r / min and the front roller speed at 280 r / min. With a roller spacing of 18mm×25mm, a twist of 700T / m, and a twist coefficient of 125, the corrugated roving is evenly wrapped around the core yarn, resulting in a corrugated core yarn with a coverage rate of 85%. The obtained corrugated core yarn is then passed through a brush cleaning machine to remove floating fibers, fuzz, and impurities from the yarn surface. Afterward, the corrugated core yarn is immersed and rubbed twice in a flame retardant finishing solution, with each immersion lasting 40 seconds and a 50% rub-off rate. Subsequently, it is pre-dried at 62℃ for 4 minutes, heat-set at 130℃ for 3 minutes, and then naturally cooled to room temperature to obtain a high-toughness flame retardant yarn.

[0036] Example 2

[0037] Take 8 parts of N-(2-hydroxypropyl)trimethylchitosan ammonium chloride, 3.5 parts of polyglycerol citrate, 2 parts of organosilicon quaternary ammonium salt, and the remainder is water. Adjust the pH of the system to 6.0, and stir for 17 minutes at 28℃ and 400 r / min to obtain a flame retardant finishing solution with a solid content of 15wt%. Select aramid filament with a linear density of 300D as the core yarn, adjust the constant tension with a tensioner, and feed it into the feed end of a Siro spinning machine after untwisting. Take flame retardant acrylic staple fiber yarn with a fiber length of 45mm and a fineness of 2.2D, and after two cardings and three drawing processes, make a corrugated roving with a basis weight of 20g / 5m. Feed it into the Siro spinning machine in two parallel strands, symmetrically distributed on the core yarn. Both sides; Siro spinning process is used for core-sheath covering, with the spindle speed set at 12500r / min, front roller speed at 290r / min, roller spacing at 18mm×25mm, twist at 750T / m, and twist coefficient at 130, so that the roving is evenly covered around the core yarn, resulting in a core-sheath yarn with a coverage rate of 88%. The obtained core-sheath yarn is then passed through a brush cleaning machine to remove floating fibers, fuzz, and impurities from the yarn surface. After that, the core-sheath yarn is dipped and rubbed twice in a flame retardant finishing solution, each dip lasting 40s, with a 55% rub-off rate. Subsequently, it is pre-dried at 65℃ for 4min, heat-set at 135℃ for 3min, and naturally cooled to room temperature to obtain a high-toughness flame retardant yarn.

[0038] Example 3

[0039] Nine parts of (2-hydroxy-3-dimethylalkylammonium)propyl chitosan oligosaccharide, four parts of pentaerythritol citrate, two parts of block polyether amino silicone oil, and the remainder being water were taken. The pH of the system was adjusted to 6.5, and the mixture was stirred for 17 minutes at 28℃ and 450 r / min to obtain a flame-retardant finishing solution with a solid content of 16 wt%. High-strength polyester filament with a linear density of 400D was selected as the core yarn. After being adjusted to constant tension by a tensioner, the yarn was fed into the feed end of a Siro spinning machine without twisting. Flame-retardant polyester staple fiber yarn with a fiber length of 48 mm and a fineness of 2.5D was taken, and after two cardings and three drawing processes, a corrugated roving with a basis weight of 22 g / 5m was prepared. The roving was fed into the Siro spinning machine in two parallel strands and distributed symmetrically. The core yarn is coated with a sheath using Siro spinning technology. The spinning machine spindle speed is set to 13000 r / min, the front roller speed is 300 r / min, the roller spacing is 18 mm × 25 mm, the twist is 800 T / m, and the twist coefficient is 135. This ensures that the sheath roving is evenly coated around the core yarn, resulting in a sheath core yarn with a 90% coating rate. The obtained sheath core yarn is then passed through a brush cleaning machine to remove floating fibers, fuzz, and impurities from the yarn surface. Afterward, the sheath core yarn is immersed and nibbled twice in a flame retardant finishing solution, with each immersion lasting 40 seconds and a nibble rate of 60%. Subsequently, it is pre-dried at 68℃ for 4 minutes, heat-set at 140℃ for 3 minutes, and then naturally cooled to room temperature to obtain a high-toughness flame retardant yarn.

[0040] Example 4

[0041] Take 10 parts of O-(2-hydroxypropyltrimethylammonium chloride)-N-p-hydroxybenzoyl chitosan, 5 parts of polymeric citrate polyol ester, 2 parts of epoxy modified silicone oil, and the remainder is water. Adjust the pH of the system to 6.0 and stir for 17 min at 28℃ and 450 r / min to obtain a flame retardant finishing liquid with a solid content of 20 wt%. Aramid filament with a linear density of 300D was selected as the core yarn. After constant tension adjustment by a tensioner, the untwisted yarn was fed into the feeding end of a ring spinning machine. Flame-retardant aramid staple fiber yarn with a fiber length of 45mm and a fineness of 2.5D was taken and, after secondary carding and three drawing processes, produced a roving with a basis weight of 21g / 5m. This roving was fed into the ring spinning machine in two parallel strands, symmetrically distributed on both sides of the core yarn. Core-sheath covering spinning was performed using ring spinning technology, with the spinning machine spindle speed set at 11000r / min, the front roller speed at 270r / min, and the roving speed at 270r / min. With a spacing of 18mm×25mm, a twist of 800T / m, and a twist coefficient of 135, the corrugated roving is evenly wrapped around the core yarn to produce a corrugated core yarn with a coverage rate of 90%. The obtained corrugated core yarn is then passed through a brush cleaning machine to remove floating fibers, fuzz, and impurities from the yarn surface. After that, the corrugated core yarn is immersed and rubbed twice in a flame retardant finishing solution, with each immersion lasting 40 seconds and a 55% rub-off rate. Subsequently, it is pre-dried at 65℃ for 4 minutes, heat-set at 145℃ for 3 minutes, and then naturally cooled to room temperature to obtain a high-toughness flame retardant yarn.

[0042] Comparative Example 1

[0043] Unlike Example 1, in this comparative example, flame-retardant polyester staple fiber yarn with a fiber length of 40 mm and a fineness of 2.0 D was taken, and after two carding and three drawing processes, it was directly spun into yarn to replace the core yarn in Example 1, and finally flame-retardant yarn was obtained.

[0044] Comparative Example 2

[0045] In this comparative example, unlike Example 1, 10 parts of decabromodiphenyl ethane, 2 parts of sodium methylene bis(naphthalene) sulfonate, 1 part of fatty alcohol polyoxyethylene ether, 0.3 parts of sodium carboxymethyl cellulose and 86.7 parts of deionized water were mixed to prepare a dispersible flame retardant finishing liquid.

[0046] Comparative Example 3

[0047] In this comparative example, unlike Example 1, no crosslinking agent was added when preparing the flame-retardant finishing liquid.

[0048] Performance verification

[0049] The flame-retardant yarns obtained in Examples 1-4 and Comparative Examples 1-3 were subjected to performance tests. The test items and evaluation criteria are as follows: 1) Limiting Oxygen Index: GB / T 5454-1997; 2) Vertical combustion performance: GB / T 5455-2014; Tests showed that the damaged length of the flame-retardant yarns obtained in Examples 1-4 was ≤85mm, with no molten droplets, indicating that the flame-retardant layer was dense and uniformly charred. Comparative Example 1, lacking a core-sheath structure design, resulted in a yarn with poor flame-retardant effect, exceeding the damage length limit (210mm) and exhibiting molten droplets. Comparative Example 2, lacking a crosslinking system, resulted in a yarn with poor flame-retardant layer adhesion, a damaged length of 145mm, and slight molten droplets. Comparative Example 3, lacking a crosslinking agent, resulted in a yarn with a flame-retardant layer that easily detached, a damaged length of 132mm, and no molten droplets.

[0050] 3) Fracture strength: GB / T 14344-2022; 4) Water wash resistance: GB / T 3921, after 20 washes, the limiting oxygen index is tested to evaluate flame retardant durability; 5) Abrasion resistance: ISO 12947, pressure 12kPa, abrasive is standard cotton cloth, number of times abrasion to breakage; 6) Color fastness to soap washing: GB / T 3921; 7) Lightfastness: GB / T 8427; 8) Color difference: Spectrophotometry; 9) Formaldehyde content: GB / T 2912.1; 10) Breathability: GB / T 5453-1997; 11) Smoke density grade: GB / T 8627-2017.

[0051] Table 1. Characterization of various performance data of the flame-retardant yarns obtained in Examples 1-4 and Comparative Examples 1-3

[0052] As can be seen from the above embodiments, the present invention provides a high-toughness flame-retardant yarn, its preparation method, and its application. Table 1 shows that, in terms of flame-retardant performance, the limiting oxygen index of the yarn in the embodiments reaches 33-35%, and remains at 31-33% after 20 washes, far exceeding that of the comparative example, demonstrating outstanding flame-retardant durability. Regarding toughness and abrasion resistance, the breaking strength of the embodiments is 3.8-4.2 cN / dtex, and the abrasion resistance is 15,000-18,000 cycles. Comparative example 1, lacking a core-sheath structure, exhibits significantly reduced strength and abrasion resistance. In terms of appearance and environmental performance, the color difference of the products obtained in embodiments 1-4 is only 0.5-0.8, indicating that the flame-retardant yarn obtained by the present invention better meets the color and environmental protection requirements of decorative fabrics. Regarding breathability, the present invention effectively solves the problem of poor breathability in traditional flame-retardant yarns. In terms of smoke density rating, the SDR of the embodiments is 65-70, meeting the stringent standards for interior fabrics in transportation vehicles. Overall, the high-toughness flame-retardant yarn obtained by this invention exhibits excellent performance in terms of flame retardancy, toughness, durability, aesthetics, breathability, and environmental friendliness.

[0053] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a high-toughness flame-retardant yarn, characterized in that, Includes the following steps: Step 1) Mix the chitosan quaternary ammonium salt derivative aqueous solution, crosslinking agent and softener to obtain flame retardant finishing liquid; Step 2) After the flame-retardant short fiber yarn is combed and drawn, it is covered with high-strength filament as the core yarn to obtain core-sheath yarn; Step 3) After pre-cleaning and brushing the core yarn, dip and rub it twice in the flame retardant finishing solution, then pre-dry and heat set in sequence, and obtain high-toughness flame retardant yarn after natural cooling.

2. The method for preparing a high-toughness flame-retardant yarn according to claim 1, characterized in that, In step 1), the flame retardant finishing liquid contains, by mass, 5-10 parts of chitosan quaternary ammonium salt derivative, 2-5 parts of crosslinking agent, 1-3 parts of softener, and the remainder is water. The crosslinking agent is citric acid polyol ester, and the softener is an organosilicon softener; The solid content of the flame-retardant finishing liquid is 10~20wt%.

3. The method for preparing a high-toughness flame-retardant yarn according to claim 2, characterized in that, In step 1), the mixing is carried out under stirring conditions, with a stirring temperature of 25~30℃, a stirring time of 15~20min, and a stirring speed of 300~500r / min.

4. A method for preparing a high-toughness flame-retardant yarn according to claim 1 or 2, characterized in that, In step 2), the high-strength filament includes aramid or high-strength polyester, with a linear density ranging from 100 to 500D; The flame-retardant staple fiber yarn includes flame-retardant acrylic or flame-retardant polyester staple fiber, with a fiber length of 38~51mm and a fineness of 1.5~3.0D.

5. The method for preparing a high-toughness flame-retardant yarn according to claim 4, characterized in that, In step 2), the coating is performed using ring spinning or Siro spinning processes, with a coating rate ≥85%, a twist of 600~900T / m, and a twist coefficient α of 120~140.

6. A method for preparing a high-toughness flame-retardant yarn according to claim 1 or 5, characterized in that, In step 3), during the two dips and two rolls, the dip time for each dip is 30-60 seconds, and the roll residue after dip and roll is 50-60%.

7. The method for preparing a high-toughness flame-retardant yarn according to claim 6, characterized in that, In step 3), the pre-drying temperature is 60~70℃, and the pre-drying time is 3~5 minutes; The heat setting temperature is 120~150℃, and the heat setting time is 2~4 minutes.

8. The high-toughness flame-retardant yarn prepared by the preparation method according to any one of claims 1 to 7.

9. The application of the high-toughness flame-retardant yarn according to claim 8 in the preparation of flame-retardant decorative fabric, characterized in that, The flame-retardant decorative fabrics include flame-retardant curtains, sofa fabrics, drapes, and vehicle interior fabrics.

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