Durable flame-retardant cellulose fiber, and yarns and fabric products thereof

Abstract

The present application relates to a durable flame-retardant cellulose fiber, and a yarn and a fabric product thereof, and belongs to the technical field of functional textile materials. The cellulose fiber exhibits a dry breaking strength of ≥2.5 cN / dtex, a dry breaking elongation of 12-18%, a limiting oxygen index (LOI) of ≥30% after 100 washing cycles, thermal stability of ≤5% at 180 °C, and a moisture regain of 10-13%. The preparation method includes: first, synthesizing a phosphorus-nitrogen composite flame retardant using di-pentaerythritol, phosphoric acid, and urea in a specific molar ratio as raw materials; then, dispersing the flame retardant powder into a finishing solution, adding dicyandiamide as a catalyst and urea as a promoter, and impregnating, nipping, and baking the cellulose fiber with the flame-retardant finishing solution. The present application overcomes the technical barrier of simultaneously achieving high durable flame-retardancy and high-quality fiber performance.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to Chinese Patent Application No. 202610281951.3, filed on March 09, 2026, which is hereby incorporated by reference in its entirety.TECHNICAL FIELD

[0002] The present application relates to the technical field of functional textile materials, and in particular, to a durable flame-retardant cellulose fiber, and a yarn and a fabric product thereof.BACKGROUND

[0003] Cellulose fibers (such as viscose fibers, lyocell fibers, and cotton fibers) are widely applied in the fields of clothing, home textiles, and industrial textiles due to excellent moisture absorption, air permeability, comfort, and biodegradability; however, cellulose fibers are inherently flammable, and a limiting oxygen index (LOI) is only about 18%, resulting in a serious fire hazard; therefore, imparting durable and efficient flame-retardant performance to cellulose fibers has important practical significance.

[0004] In the prior art, the flame-retardant finishing of cellulose fibers mainly adopts phosphorus-nitrogen flame retardants. The common methods include applying a flame retardant to fibers or fabrics through padding, coating, or blending. However, these methods often have one or more of the following technical problems:

[0005] Insufficient flame-retardant durability: after multiple washing cycles, a flame retardant is prone to falling off, resulting in a significant decrease in flame-retardant performance;

[0006] Damage to mechanical properties of fibers: intense chemical treatment or high-temperature baking destroys a cellulose molecular structure, resulting in deterioration of mechanical properties such as fiber strength and elongation, and affecting spinnability and wearability;

[0007] Reduction in comfort: introduction of a flame retardant changes moisture regain and surface characteristics of fibers, resulting in stiff hand feel of a fabric and deterioration of moisture absorption and sweat-wicking performance; and

[0008] Poor thermal stability: during subsequent textile processing (such as dyeing and heat setting), or during use when exposed to heat, fibers or a flame retardant attached to fibers may undergo decomposition, yellowing, or strength loss.

[0009] In the prior art, for example, the Chinese Patent Application Publication No. CN120192345A discloses a method for preparing a phosphorus-nitrogen composite flame retardant using raw materials such as pentaerythritol, phosphoric acid, and urea. However, such an method and obtained products are often difficult to achieve an ideal balance among high flame-retardant durability, high retention of mechanical properties, good comfort, and thermal stability when applied to cellulose fibers; particularly, obtaining a flame-retardant cellulose fiber that simultaneously satisfies an extreme durability requirement of "LOI ≥ 30% after 100 washing cycles" and maintains high-quality wearable fiber indicators such as "dry breaking strength ≥ 2.5 cN / dtex" and "moisture regain of 10-13%" remains a technical problem that has not been well solved in the art for a long time.

[0010] Therefore, the development of a cellulose fiber having excellent durable flame-retardant performance, good mechanical properties, comfortable hand feel, and stable processing performance has important significance for improving quality of high-end flame-retardant textiles and expanding application scenarios of such textiles.SUMMARY

[0011] The present application provides a durable flame-retardant cellulose fiber, and a yarn and a fabric product thereof, where the fiber maintains a high flame-retardant level under extreme washing conditions, and possesses high strength, suitable elongation, good moisture absorption, and thermal stability; and the present application efficiently and stably prepares the high-performance fiber by selecting specific raw materials and optimizing a reaction-finishing process.

[0012] The technical solutions of the present application for solving the above technical problem are as follows:

[0013] According to a first aspect, the present application provides a method for preparing a durable flame-retardant cellulose fiber, which includes the following steps:

[0014] a. synthesis of a phosphorus-nitrogen composite flame retardant: mixing Di-PE (di-pentaerythritol) and an aqueous phosphoric acid solution and heating the mixture to 100-140 °C for 1-3 h; adding urea, raising a temperature to 100-170 °C, and continuously stirring for 2-3 h, where a molar ratio of the Di-PE, the phosphoric acid, and the urea is 1:4:8; after the reaction is completed, filtering a precipitate, repeatedly washing the precipitate with anhydrous ethanol to remove impurities, drying the precipitate at 50-80 °C for 1-3 h, and pulverizing the dried solid to obtain a phosphorus-nitrogen composite flame retardant powder having a particle size of 300-1000 mesh;

[0015] b. preparation of the durable flame-retardant cellulose fiber: formulating the phosphorus-nitrogen composite flame retardant powder obtained in step a with distilled water to prepare a flame-retardant finishing solution having a solid content of 20-65%; adding dicyandiamide as a catalyst and urea as a promoter to the finishing solution and dissolving the mixture by heating in a water bath, where an addition amount of the dicyandiamide is 1-15% by weight of the flame retardant powder, and an addition amount of the urea is 1-15% by weight of the flame retardant powder; immersing cellulose fibers in the flame-retardant finishing solution for 1-30 min and removing the fibers; pressing the fibers by a nip roller to achieve a wet pickup of 50-150%; and baking the impregnated and pressed fibers at 120-200 °C for 1-15 min to obtain the durable flame-retardant cellulose fiber.

[0016] According to a second aspect, the present application provides a durable flame-retardant cellulose fiber, where the fiber is prepared by the method described in the first aspect, and has a dry breaking strength of ≥ 2.5 cN / dtex, a dry breaking elongation of 12-18%, a length of 30-60 mm, a limiting oxygen index of ≥ 30% after 100 washing cycles, a thermal stability of ≤ 5% at 180 °C, a moisture regain of 10-13%, and an oil content of 0.2-0.5%.

[0017] According to a third aspect, the present application provides a durable flame-retardant yarn, where the yarn is prepared by blending the durable flame-retardant cellulose fiber described in the first aspect with at least one other fiber, and a mass content of the durable flame-retardant cellulose fiber in the yarn is ≥ 10%.

[0018] According to a fourth aspect, the present application provides a durable flame-retardant fabric product, where the fabric product is prepared from the durable flame-retardant cellulose fiber described in the first aspect or the durable flame-retardant yarn described in the third aspect, and a mass content of the durable flame-retardant cellulose fiber in the fabric product is ≥ 10%.

[0019] Based on the above technical solutions, the present application may be further improved as follows.

[0020] Further, the at least one other fiber may be selected from one or more of meta-aramid, para-aramid, modified acrylic, polyimide, PBO, PBI, viscose fiber, cotton fiber, and lyocell fiber, where blending the durable flame-retardant cellulose fiber with high-performance fibers such as meta-aramid, para-aramid, polyimide, PBO, or PBI can significantly improve extreme properties of the finished product, including high-temperature resistance, anti-drip performance, and mechanical strength, making the product suitable for high-end fields such as firefighting and specialized protection; and blending the durable flame-retardant cellulose fiber with conventional cellulose fibers such as cotton, viscose, or lyocell enables maintaining basic flame-retardant requirements while improving hand feel, reducing cost, enhancing moisture comfort, or meeting specific product style requirements, thereby expanding applications of the present application in civil and occupational apparel fields.

[0021] Further, the durable flame-retardant yarn may be spun by conventional spinning processes, including ring spinning, vortex spinning, air spinning, or compact siro spinning, all of which are mature and widely used technologies in the textile industry and do not require development of special or expensive equipment. This enables the fibers provided by the present application to be seamlessly integrated into existing yarn production systems, allows stable and efficient preparation of yarns of various specifications and qualities, facilitates rapid technology transfer and large-scale promotion, and reduces production barriers and investment risk.

[0022] Further, the durable flame-retardant fabric product may be a woven fabric, a knitted fabric, or a nonwoven fabric, where the woven fabric has a stable structure and high strength, and is suitable for products such as outerwear, workwear, and curtains that require good dimensional stability and durability; the knitted fabric is soft, elastic, and breathable, and is suitable for products such as underwear, T-shirts, and sportswear that are close-fitting or require certain elasticity; and the nonwoven fabric enables efficient production and one-time use, and is widely applied in medical and hygiene materials, filtration materials, home textiles, and some industrial linings, covering a plurality of end-product fields from apparel to home textiles, and from industrial use to healthcare, thereby exhibiting strong market adaptability.

[0023] The present application has the following beneficial effects: the present application provides a durable flame-retardant cellulose fiber, and a yarn and a fabric product thereof, which have the following advantages:

[0024] 1. The present application overcomes the technical barrier of simultaneously achieving high durable flame retardancy and high-quality fibers, and achieves a perfect combination of extreme durability (LOI ≥ 30% after 100 washing cycles), high strength (≥ 2.5 cN / dtex), good comfort (moisture regain of 10-13%), and excellent thermal stability (≤ 5% at 180 °C).

[0025] 2. The present application adopts a unique method design by selecting Di-PE as the starting material. Compared with the conventional pentaerythritol, Di-PE exhibits higher hydroxyl functionality and molecular rigidity, and the reaction with phosphoric acid and urea forms a phosphorus-nitrogen network structure having higher crosslinking density and thermal stability. This unique flame-retardant structure inherently imparts the fiber with ultra-durable flame retardancy and low thermal shrinkage. A dicyandiamide-urea composite catalyst / promoter system efficiently catalyzes covalent crosslinking between the flame retardant and cellulose molecules during baking, thereby significantly enhancing the fixation rate of the flame retardant and ensuring wash durability; and the relatively mild reaction conditions minimize damage to cellulose molecular chains, so that the high strength and the moisture regain are maintained.

[0026] 3. The present application has broad application prospects, where the fiber provided by the present application maintains good spinnability and wearability and can be blended with various high-performance or conventional fibers; and the resulting yarns and fabrics achieve excellent flame-retardant safety while simultaneously ensuring comfort, durability, and dyeing processability. These properties enable wide application in firefighting apparel, military uniforms, specialized workwear, high-end flame-retardant home textiles, and interior materials for aircraft and high-speed trains.

[0027] The above description is only an overview of the technical solutions of the present application. To clearly understand the technical means of the present application and to enable implementation in accordance with the contents of the specification, the following provides detailed descriptions of preferred embodiments of the present application in conjunction with the accompanying drawings. The specific embodiments of the present application are set forth in detail in the following examples and the accompanying drawings.BRIEF DESCRIPTION OF DRAWINGS

[0028] The accompanying drawings described herein are provided to further understand the present application and form a part of the present application. The illustrative embodiments and the descriptions thereof are used to explain the present application and do not constitute an improper limitation of the present application. In the drawings:

[0029] FIG. 1 is a synthetic route of a phosphorus-nitrogen high-efficiency composite flame retardant for a durable flame-retardant cellulose fiber, and a yarn and a fabric product thereof according to an embodiment of the present application;

[0030] FIG. 2 is a preparation route of a durable flame-retardant cellulose fiber for a durable flame-retardant cellulose fiber, and a yarn and a fabric product thereof according to an embodiment of the present application; and

[0031] FIG. 3 is a diagram illustrating specific finished fabric indicators of a durable flame-retardant cellulose fiber, and a yarn and a fabric product thereof according to an embodiment of the present application.DESCRIPTION OF EMBODIMENTS

[0032] The principles and features of the present application are described below in conjunction with FIGS. 1-3. The examples provided are only for the purpose of explaining the present application and are not intended to limit the scope of the present application. The present application is further described in detail by referring to the drawings in the following paragraphs. The advantages and features of the present application will become clearer based on the following description. It should be noted that the drawings are presented in highly simplified form and are not drawn to precise scale, and are provided solely to facilitate and clarify the description of embodiments of the present application.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application pertains. The terminology used in the specification of the present application is only for the purpose of describing specific embodiments and is not intended to limit the present application. The term "and / or" as used herein encompasses any and all possible combinations of one or more of the listed items.Embodiment 1: Preparation of a durable flame-retardant cellulose fiber

[0034] As shown in FIG. 1, Step 1: Synthesis of a phosphorus-nitrogen high-efficiency composite flame retardant

[0035] 1. In a three-necked flask equipped with a stirrer, a thermometer, and a reflux condenser, 85% phosphoric acid solution (calculated as P2O5, corresponding to 4 mol of phosphoric acid) and di-pentaerythritol (Di-PE, 1 mol) were sequentially added.

[0036] 2. The mixture was stirred, the reaction system was slowly heated to 110 °C, and the mixture was stirred at this temperature for 2 h.

[0037] 3. Urea (8 mol) was added to the reaction mixture, and the mixture was further heated to 150 °C and stirred at this temperature for 2.5 h, during which a large amount of white precipitate was generated.

[0038] 4. After the reaction, the mixture was cooled to room temperature and subjected to vacuum filtration to collect a precipitate.

[0039] 5. The precipitate was washed multiple times (for example, 3-5 times) with anhydrous ethanol until the washing liquid was neutral, thereby removing unreacted monomers and by-products.

[0040] 6. The washed precipitate was dried at 65 °C in an oven for 2 h.

[0041] 7. The dried solid was pulverized using a pulverizer and sieved to obtain a white phosphorus-nitrogen composite flame retardant powder (P-N FR) with a particle size distribution of 300-1000 mesh.

[0042] As shown in FIG. 2, Step 2: Preparation of the durable flame-retardant cellulose fiber

[0043] 1. Preparation of the flame-retardant finishing solution: 300 g of the P-N FR powder obtained in Step 1 was weighed and added to 700 g of distilled water. The mixture was dispersed uniformly by high-speed stirring to prepare a flame-retardant finishing solution with a solid content of approximately 30%.

[0044] 2. Dicyandiamide (15 g, 5% by weight of the P-N FR powder) and urea (15 g, 5% by weight of the P-N FR powder) were added to the above finishing solution. The mixture was stirred in a 60 °C water bath until completely dissolved, and a homogeneous flame-retardant working solution was obtained.

[0045] 3. 1 kg of ordinary viscose staple fibers (specification: 1.5D × 38 mm, dry breaking strength approximately 2.2 cN / dtex) was completely immersed in the above flame-retardant working solution and treated at room temperature for 15 min, during which the fibers were gently turned over to ensure uniform wetting.

[0046] 4. The impregnated fibers were removed and pressed using a laboratory small nip roller, and a wet pickup was controlled at 80%.

[0047] 5. The pressed fibers were evenly laid on a mesh tray in an oven and baked under hot air at 170 °C for 8 min.

[0048] 6. After baking, the fibers were removed and allowed to cool naturally to room temperature, thereby obtaining the durable flame-retardant cellulose fiber.

[0049] Performance testing:

[0050] The prepared durable flame-retardant viscose fiber was subjected to performance testing, and the results were as follows:

[0051] Dry breaking strength: 2.8 cN / dtex (tested according to GB / T 14337-2008)

[0052] Dry breaking elongation: 15.5% (tested according to GB / T 14337-2008)

[0053] Limiting oxygen index (LOI, original): 34.5% (tested according to GB / T 5454-1997)

[0054] Limiting oxygen index (after 100 standard washing cycles): 31.2% (tested after accelerated washing according to Appendix C of GB / T 17596-1998 or AATCC 61-2013, Test 2A)

[0055] Thermal stability at 180 °C (strength loss after 30-min treatment): 3.8% (tested by thermogravimetric analysis or strength retention test)

[0056] Moisture regain (under standard temperature and humidity conditions): 11.8% (tested according to GB / T 9995-1997)

[0057] Oil content: 0.35% (tested by Soxhlet extraction)

[0058] The test results indicate that the flame-retardant viscose fiber prepared in this embodiment fully meets the technical specifications described in claim 1, and exhibits excellent durable flame-retardancy, good mechanical performance, and desirable comfort.

[0059] Embodiment 2: Preparation of a durable flame-retardant yarn and a durable flame-retardant fabricStep 1: Spinning

[0060] 1. The durable flame-retardant viscose fiber prepared in Embodiment 1 (specification: 1.5D × 38 mm, after flame-retardant treatment) was mixed with ordinary lyocell fibers in a 50 / 50 weight ratio and opened for blending.

[0061] 2. The blended fibers were spun into a 32 Ne (approximately 18.2 tex) durable flame-retardant blended yarn using a conventional ring spinning process, including cleaning, carding, drawing, roving, and spinning. In the resulting yarn, the durable flame-retardant cellulose fiber accounted for 50% by weight, which is substantially greater than 10%.Step 2: Weaving and post-finishing

[0062] 1. The above-spun flame-retardant yarn was used as weft yarn and interlaced with ordinary cotton yarn of the same specification (warp yarn) on a rapier loom to produce a plain woven greige fabric.

[0063] 2. The greige fabric was subjected to conventional desizing, scouring, and bleaching treatments, and then heat-set at 190 °C for 1 min.

[0064] 3. The final durable flame-retardant woven fabric according to the present application was obtained.

[0065] Performance testing: The prepared fabric was subjected to performance testing, and some key properties are shown in FIG. 3. For example, the limiting oxygen index (LOI) was 32%, the thermal stability was excellent as indicated by low dimensional shrinkage, the flame-retardant performance was superior (no after-flame or smoldering, short damage length), and the high thermal protective performance (TPP value) was observed. These properties resulted from the incorporation of the durable flame-retardant cellulose fiber according to the present application.

[0066] It should be noted that the testing methods for the performance parameters of the present application were as follows: dry breaking strength and elongation: tested according to GB / T 14337-2008, "Man-made fibers-Determination of breaking strength and breaking elongation of staple fibers"; limiting oxygen index (LOI): tested according to GB / T 5454-1997, "Textiles-Burning behavior-Oxygen index method"; wash durability: 100 standard washing cycles were performed according to GB / T 12490-2014, "Textiles-Tests for color fastness-Color fastness to domestic and commercial laundering" and LOI was measured after washing; thermal stability (weight loss at 180 °C): tested by thermogravimetric analysis (TGA) under a nitrogen atmosphere, the fiber was heated from room temperature to 180 °C at a rate of 10 °C / min and maintained at 180 °C for 10 min, and the percentage of mass loss was recorded; and moisture regain: tested according to GB / T 9995-1997, "Determination of moisture content and moisture regain of textile-Oven-drying method"; and oil content: tested according to GB / T 6504-2017, "Man-made fiber-Test method for oil content".

[0067] The above description is merely the preferred embodiments of the present application and does not constitute any form of limitation on the present application. Those of ordinary skill in the art can smoothly implement the present application according to the above description and the accompanying drawings. However, any minor modifications, alterations, or variations made by those skilled in the art without departing from the scope of the technical solutions of the present application, based on the technical content disclosed above, are considered equivalent embodiments of the present application. Likewise, any such equivalent modifications, alterations, or variations made to the above embodiments in accordance with the essential technical features of the present application remain within the scope of the technical solutions of the present application.

Claims

1. A method for preparing a durable flame-retardant cellulose fiber, comprising:a. synthesis of a phosphorus-nitrogen composite flame retardant: mixing di-pentaerythritol (Di-PE) with an aqueous phosphoric acid solution and heating the mixture to 100-140 °C for 1-3 h, adding urea, further heating the mixture to 100-170 °C and stirring for 2-3 h, wherein a molar ratio of the Di-PE, the phosphoric acid, and the urea is 1:4:8, filtering a resulting precipitate, repeatedly washing the precipitate with anhydrous ethanol to remove impurities, drying the washed precipitate in an oven at 50-80 °C for 1-3 h, and pulverizing the dried precipitate to obtain a phosphorus-nitrogen composite flame retardant powder having a particle size of 300-1000 mesh;b. preparation of the durable flame-retardant cellulose fiber: dispersing the phosphorus-nitrogen composite flame retardant powder in distilled water to prepare a flame-retardant finishing solution having a solid content of 20-65%, adding dicyandiamide as a catalyst and urea as a promoter to the prepared solution, dissolving the mixture by heating in a water bath, wherein a weight of the dicyandiamide is 1-15% of an effective weight of the flame retardant, and a weight of the urea is 1-15% of the effective weight of the flame retardant, immersing cellulose fibers in the flame-retardant finishing solution for 1-30 min, removing excess solution using a nip roller to achieve a wet pickup of 50-150%, and baking the fibers at 120-200 °C for 1-15 min to obtain the durable flame-retardant cellulose fiber.

2. A durable flame-retardant cellulose fiber, prepared by the method according to claim 1, wherein the durable flame-retardant cellulose fiber has a dry breaking strength of ≥ 2.5 cN / dtex, a dry breaking elongation of 12-18%, a length of 30-60 mm, a limiting oxygen index of ≥ 30% after 100 washing cycles, a thermal stability of ≤ 5% at 180 °C, a moisture regain of 10-13%, and an oil content of 0.2-0.5%.

3. A durable flame-retardant yarn, prepared by blending the durable flame-retardant cellulose fiber according to claim 1 with at least one other fiber, wherein a mass content of the durable flame-retardant cellulose fiber in the yarn is ≥ 10%.

4. The durable flame-retardant yarn according to claim 3, wherein the at least one other fiber is selected from one or more of meta-aramid, para-aramid, modified acrylic, polyimide, PBO, PBI, viscose fiber, cotton fiber, and lyocell fiber.

5. The durable flame-retardant yarn according to claim 3, spun by ring spinning, vortex spinning, air spinning, or compact siro spinning.

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