Durable flame-retardant cellulose fiber and yarn and fabric product thereof

Abstract

The invention relates to a durable flame-retardant cellulosic fiber and yarn and fabric products thereof, and belongs to the technical field of functional textile materials, the dry breaking strength of the fiber is larger than or equal to 2.5 cN / dtex, the dry elongation at break is 12-18%, the limit oxygen index after 100 times of washing is larger than or equal to 30%, the thermal stability at 180 DEG C is smaller than or equal to 5%, and the moisture regain is 10-13%. The preparation method comprises the following steps: synthesizing a phosphorus-nitrogen composite flame retardant with a specific molar ratio by taking dipentaerythritol, phosphoric acid and urea as raw materials; and then, preparing the flame retardant powder into a finishing liquid, adding a dicyandiamide catalyst and a urea accelerant, and carrying out padding, baking and finishing on the cellulose fibers. The technical barrier that high-durability flame-retardant performance and high-quality fiber performance are difficult to consider at the same time is broken through, and the obtained product still keeps a high flame-retardant grade after extreme water washing, has excellent mechanical property, comfort and processing thermal stability and is suitable for the field of high-end protective clothing and textiles for special industries.

Description

Technical Field

[0001] This invention relates to the field of functional textile materials technology, and in particular to a durable flame-retardant cellulose fiber and its yarn and fabric products. Background Technology

[0002] Cellulose fibers (such as viscose fiber, lyocell fiber, cotton fiber, etc.) are widely used in clothing, home textiles and industrial textiles due to their excellent moisture absorption, breathability, comfort and biodegradability. However, cellulose fibers are flammable, with a limiting oxygen index (LOI) of only about 18%, posing a serious fire hazard. Therefore, endowing cellulose fibers with durable and efficient flame retardant properties is of great practical significance.

[0003] In existing technologies, flame-retardant finishing of cellulose fibers mainly uses phosphorus-nitrogen flame retardants. Common methods include applying the flame retardant to the fiber or fabric through padding, coating, or blending. However, these methods often face one or more of the following technical challenges: Insufficient flame retardant durability: After repeated washing, the flame retardant is easily detached, resulting in a significant decrease in flame retardant performance; Damage to fiber mechanical properties: Severe chemical treatment or high-temperature baking can damage the molecular structure of cellulose, leading to deterioration of mechanical properties such as fiber strength and elongation, affecting spinnability and wearability; Decreased comfort: The introduction of flame retardants may alter the moisture regain and surface properties of fibers, resulting in a stiff fabric feel and reduced moisture absorption and wicking capacity. Poor thermal stability: When exposed to heat during subsequent textile processing (such as dyeing and finishing) or use, the fibers or flame retardants attached to them may decompose, yellow, or lose strength. Existing technologies (such as CN120192345A) disclose methods for preparing phosphorus-nitrogen composite flame retardants using raw materials such as pentaerythritol, phosphoric acid, and urea. However, when these methods and the resulting products are applied to cellulose fibers, it is often difficult to achieve an ideal balance between high flame retardancy and durability, high mechanical property retention, good comfort, and thermal stability. In particular, obtaining a flame-retardant cellulose fiber that can simultaneously meet the extreme durability requirement of "LOI ≥ 30% after 100 washes" and maintain high-quality apparel fiber indicators such as "dry breaking strength ≥ 2.5 cN / dtex" and "moisture regain 10-13%" remains a long-standing technical problem that has not been well solved in this field.

[0004] Therefore, developing a cellulose fiber that combines excellent durability and flame retardancy, superior mechanical properties, comfortable feel, and processing stability is of great significance for improving the quality of high-end flame-retardant textiles and expanding their application scenarios. Summary of the Invention

[0005] This invention provides a durable flame-retardant cellulose fiber and its yarn and fabric products. The fiber can maintain a high flame retardancy rating under extreme washing conditions, while also possessing high strength, suitable elongation, good moisture absorption and thermal stability. The method uses specific raw materials and optimized reaction-finishing processes to efficiently and stably prepare the high-performance fiber.

[0006] The solution of the present invention to the above-mentioned technical problems is as follows: In a first aspect, the present invention provides a method for preparing the durable flame-retardant cellulose fiber, comprising the following steps: a. Synthesis of phosphorus-nitrogen composite flame retardant: Di-PE (dipentaerythritol) and phosphoric acid aqueous solution are mixed and heated to 100-140℃ for 1-3 h. Then urea is added, the temperature is raised to 100-170℃, and the reaction is stirred continuously for 2-3 h. The molar ratio of Di-PE, phosphoric acid and urea is 1:4:8. After the reaction is completed, the precipitate is filtered out, and the precipitate is repeatedly washed with anhydrous ethanol to remove impurities. Then it is dried at a low temperature of 50-80℃ for 1-3 h. The resulting solid is pulverized to obtain phosphorus-nitrogen composite flame retardant powder with a particle size of 300 to 1000 mesh. b. Preparation of durable flame-retardant cellulose fibers: The phosphorus-nitrogen composite flame retardant powder obtained in step a is prepared into a flame-retardant finishing solution with a solid content of 20-65% using distilled water; then, dicyandiamide is added as a catalyst and urea as an accelerator to the finishing solution, and the solution is dissolved by water bath heating, wherein the amount of dicyandiamide added is 1-15% of the weight of the flame retardant powder, and the amount of urea added is 1-15% of the weight of the flame retardant powder; the cellulose fibers are immersed in the flame-retardant finishing solution for 1-30 minutes, and then rolled with a rolling mill, controlling the liquid content to be 50-150%; finally, the rolled fibers are baked at 120-200℃ for 1-15 minutes to obtain the durable flame-retardant cellulose fibers.

[0007] Secondly, the present invention provides a durable flame-retardant cellulose fiber, which is prepared by the above method and has a dry breaking strength ≥2.5cN / dtex, a dry breaking elongation of 12-18%, a length of 30-60mm, a limiting oxygen index ≥30% after 100 washes, a thermal stability ≤5% at 180℃, a moisture regain of 10-13%, and an oil content of 0.2-0.5%.

[0008] Thirdly, the present invention provides a durable flame-retardant yarn, which is made by blending the durable flame-retardant cellulose fiber described in the first aspect with at least one other fiber, and the mass content of the durable flame-retardant cellulose fiber in the yarn is ≥10%.

[0009] Fourthly, the present invention provides a durable flame-retardant fabric product, which is made from the durable flame-retardant cellulose fiber described in the first aspect or the durable flame-retardant yarn described in the third aspect, wherein the mass content of the durable flame-retardant cellulose fiber in the fabric product is ≥10%.

[0010] Based on the above technical solution, the present invention can be further improved as follows.

[0011] Furthermore, the other fibers can be selected from one or more of meta-aramid, para-aramid, modified acrylic, polyimide, PBO, PBI, viscose fiber, cotton fiber, and lyocell fiber. Blending these fibers with high-performance fibers such as meta-aramid, para-aramid, polyimide, PBO, and PBI can significantly improve the finished product's extreme properties such as high-temperature resistance, flame drip resistance, and mechanical strength, making it suitable for high-end fields such as fire protection and special protection. Blending these fibers with conventional cellulose fibers such as cotton, viscose, and lyocell can improve the feel, reduce costs, enhance moisture absorption and comfort, or meet specific product style requirements while ensuring basic flame retardancy requirements, thus broadening the application scope of this invention in civilian and professional clothing fields.

[0012] Furthermore, the durable flame-retardant yarn can be spun using conventional spinning processes such as ring spinning, vortex spinning, air-jet spinning, or compact Siro spinning. The listed ring spinning, vortex spinning, air-jet spinning, and compact Siro spinning are all mature and widely used spinning technologies in the textile industry, requiring no special or expensive dedicated equipment. This means that the fiber provided by this invention can be seamlessly integrated into the existing yarn production system, quickly achieving stable and efficient preparation of yarns of different specifications and qualities. This facilitates the rapid transformation and large-scale promotion of the technology, reducing production barriers and investment risks.

[0013] Furthermore, the durable flame-retardant fabric products can be woven fabrics, knitted fabrics, or non-woven fabrics. Woven fabrics have a stable structure and high strength, making them suitable for products requiring good dimensional stability and durability, such as outerwear, workwear, and curtains. Knitted fabrics are soft, elastic, breathable, and comfortable, making them suitable for underwear, T-shirts, sportswear, and other close-fitting or elastic applications. Non-woven fabrics are highly efficient to produce and can be used disposable, making them widely used in medical and hygiene products, filter materials, home textiles, and certain industrial linings. Their scope covers multiple end-product areas, from clothing to home textiles, and from industrial to healthcare, demonstrating strong market adaptability.

[0014] The beneficial effects of this invention are as follows: This invention provides a durable flame-retardant cellulose fiber and its yarn and fabric products, which have the following advantages: 1. It breaks through the technical barrier that makes it difficult to achieve both "high durability and flame retardancy" and "high quality fiber", and achieves a perfect unity of "extreme durability" (LOI≥30% after 100 washes), high strength (≥2.5 cN / dtex), good comfort (moisture regain 10-13%) and excellent thermal stability (≤5% at 180℃).

[0015] 2. Featuring a unique method design, Di-PE is selected as the starting material. Compared with conventional pentaerythritol, Di-PE has higher hydroxyl functionality and molecular structural rigidity. After reacting with phosphoric acid and urea, it can form a PN network structure with higher crosslinking density and thermal stability. This unique flame retardant structure is the intrinsic reason for the fiber's ultra-durable flame retardancy and low heat shrinkage. A "dicyandiamide-urea" composite catalytic / promoting system is adopted. This system can efficiently catalyze the covalent crosslinking reaction between the flame retardant and cellulose molecules during baking, greatly improving the fixation rate of the flame retardant (thus ensuring washability). At the same time, the reaction conditions are relatively mild, minimizing damage to the cellulose molecular chains (thus maintaining high strength and high moisture regain).

[0016] 3. It has broad application prospects. The provided fibers maintain good spinnability and wearability. They can be blended with a variety of high-performance or conventional fibers. The resulting yarns and fabrics maintain excellent flame retardant safety while taking into account comfort, durability and dyeability. They can be widely used in fire-fighting clothing, military uniforms, special workwear, high-end flame-retardant home textiles, aircraft and high-speed rail interior materials and other fields.

[0017] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it according to the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Specific embodiments of the present invention are given in detail below with reference to the accompanying drawings. Attached Figure Description

[0018] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings: Figure 1 A synthesis route diagram of a phosphorus-nitrogen high-efficiency composite flame retardant for durable flame-retardant cellulose fibers and their yarns and fabrics, provided in an embodiment of the present invention; Figure 2 This is a flowchart illustrating the preparation process of durable flame-retardant cellulose fiber, its yarn, and fabric products, as provided in an embodiment of the present invention. Figure 3 This is a diagram showing the specific indicators of a durable flame-retardant cellulose fiber and its yarn and woven fabric, provided as an embodiment of the present invention. Detailed Implementation

[0019] The following is in conjunction with the appendix Figure 1-3 The principles and features of the present invention are described below. The examples given are for illustrative purposes only and are not intended to limit the scope of the invention. The invention is described more specifically in the following paragraphs by way of example with reference to the accompanying drawings. The advantages and features of the invention will become clearer from the following description. It should be noted that the drawings are in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the invention.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0021] Example 1: Preparation of durable flame-retardant cellulose fibers; like Figure 1 As shown, step one: synthesis of phosphorus-nitrogen high-efficiency composite flame retardant; 1. In a three-necked flask equipped with a stirrer, thermometer and reflux condenser, add 85% phosphoric acid aqueous solution (4 mol of phosphoric acid as P2O5) and dipentaerythritol (Di-PE, 1 mol) in sequence. 2. Turn on the stirrer and slowly heat the reaction system to 110°C, and continue stirring at this temperature for 2 hours; 3. Add urea (8 mol) to the above reaction solution, continue to heat to 150℃, and continue stirring at this temperature for 2.5 hours. A large amount of white precipitate is produced during the reaction. 4. After the reaction is complete, cool the reaction mixture to room temperature, perform vacuum filtration, and collect the precipitate; 5. Wash the precipitate multiple times with anhydrous ethanol (e.g., 3-5 times) until the washing solution is neutral to remove unreacted monomers and byproducts. 6. Place the washed precipitate in an oven and dry it at a low temperature of 65℃ for 2 hours; 7. The dried block solid is crushed with a pulverizer and sieved to obtain a white phosphorus-nitrogen composite flame retardant powder (PN FR) with a particle size distribution of 300-1000 mesh.

[0022] like Figure 2 As shown, step two: preparation of durable flame-retardant cellulose fibers; 1. Preparation of flame retardant finishing liquid: Weigh 300g of PN FR powder obtained in step one, add it to 700g of distilled water, stir at high speed to disperse it evenly, and prepare a flame retardant finishing liquid with a solid content of about 30%. 2. Add 15g of dicyandiamide (5% of the weight of PN FR powder) and 15g of urea (5% of the weight of PN FR powder) to the above finishing solution, and stir in a 60℃ water bath until completely dissolved to obtain a homogeneous flame retardant working solution. 3. Take 1 kg of ordinary viscose staple fiber (specification: 1.5D×38mm, dry breaking strength about 2.2 cN / dtex), completely immerse it in the above flame retardant working solution, and immerse it at room temperature for 15 minutes, gently turning it over during the process to ensure that the fiber is evenly wetted. 4. Remove the impregnated fibers and roll them using a small laboratory rolling mill, controlling the residual rate (liquid content) to be 80%; 5. Spread the rolled fibers evenly on the drying oven rack and bake at 170℃ for 8 minutes. 6. After baking, remove the fiber and allow it to cool naturally to room temperature to obtain the durable flame-retardant cellulose fiber.

[0023] Performance testing: The performance of the prepared durable flame-retardant viscose fiber was tested, and the results are as follows: Dry fracture strength: 2.8 cN / dtex (tested according to GB / T 14337-2008) Elongation at break: 15.5% (tested according to GB / T 14337-2008) Limiting oxygen index (LOI, raw): 34.5% (tested according to GB / T 5454-1997) Limiting oxygen index (after 100 standard washes): 31.2% (tested after accelerated washing according to Appendix C of GB / T 17596-1998 or AATCC61-2013 2A conditions) Thermal stability at 180℃ (strength loss rate after 30 minutes of treatment): 3.8% (refer to thermogravimetric analysis or strength retention rate test). Moisture regain (under standard temperature and humidity): 11.8% (tested according to GB / T 9995-1997) Oil content: 0.35% (tested using Soxhlet extraction method) Test results show that the flame-retardant viscose fiber prepared in this embodiment fully meets the technical indicators described in claim 1, and has excellent durability and flame retardancy, good mechanical properties and comfort.

[0024] Example 2: Preparation of durable flame-retardant yarns and fabrics; Step 1: Spinning 1. Take the durable flame-retardant viscose fiber (specification changed to: 1.5D×38mm, after flame retardant treatment) obtained in Example 1 and ordinary lyocell fiber and mix and open them at a weight ratio of 50 / 50; 2. Using the conventional ring spinning process (cotton cleaning → carding → drawing → roving → spinning), the blended fibers are spun into a 32-count (approximately 18.2 tex) durable flame-retardant blended yarn. The mass content of durable flame-retardant cellulose fiber in this yarn is 50%, which is much greater than 10%.

[0025] Step Two: Weaving and Finishing 1. The flame-retardant yarn spun above is used as the weft yarn and interwoven with ordinary cotton yarn (warp yarn) of the same specification on a rapier loom to produce plain weave fabric; 2. Perform conventional desizing, sizing, and bleaching treatments on the grey fabric, and then heat set at 190℃ for 1 minute; 3. Obtain the final durable flame-retardant woven fabric as described in this invention.

[0026] Performance testing: The fabric was tested, and some key properties are shown in the figure (see the instruction manual appendix). Figure 3 For example, the limiting oxygen index (LOI) is 32%, the thermal stability is good (manifested as low dimensional shrinkage), the flame retardant performance is excellent (no afterflame, no smoldering, short damage length), and it has high thermal protection performance (TPP value). These properties are due to the use of durable flame retardant cellulose fibers as described in this invention in the fabric.

[0027] It should be noted that the test methods for the performance parameters of this invention are as follows: Dry breaking strength and elongation: performed according to GB / T14337-2008 "Determination of breaking strength and elongation at break of short chemical fibers"; Limiting oxygen index (LOI): performed according to GB / T 5454-1997 "Test for flammability of textiles - Oxygen index method"; Washability: performed under the test conditions of GB / T 12490-2014 "Test for color fastness of textiles - Color fastness to household and commercial washing" for 100 washes, and the LOI was measured after each wash; Thermal stability (thermal weight loss at 180℃): using a thermogravimetric analyzer, under a nitrogen atmosphere, the temperature was increased from room temperature to 180℃ at a rate of 10℃ / min, and held for 10 min, and the percentage of mass loss was recorded; Moisture regain: performed according to GB / T The following standards shall be followed: 9995-1997 "Determination of Moisture Content and Moisture Regain of Textile Materials by Oven Drying Method"; Oil content: Refer to GB / T6504-2017 "Test Method for Oil Content of Chemical Fibers".

[0028] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Those skilled in the art can readily implement the present invention based on the accompanying drawings and the above description. However, any modifications, alterations, or variations made by those skilled in the art without departing from the scope of the present invention, utilizing the disclosed technical content, are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, or variations made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the present invention.

Claims

1. A method for preparing durable flame-retardant cellulose fibers, characterized in that, The preparation method includes the following steps: a. Synthesis of phosphorus-nitrogen high-efficiency composite flame retardant, wherein Di-PE and phosphoric acid aqueous solution are mixed and heated to 100-140℃ and reacted for 1-3 hours, then urea is added, the temperature is raised to 100-170℃, and the reaction is continuously stirred for 2-3 hours. The molar ratio of Di-PE, phosphoric acid and urea is 1:4:

8. The precipitate is filtered out by filtration, and the precipitate is repeatedly washed with anhydrous ethanol to remove impurities. Then it is placed in an oven and dried at a low temperature of 50-80℃ for 1-3 hours. The precipitate is pulverized to obtain phosphorus-nitrogen composite flame retardant powder with a particle size of 300 to 1000 mesh. b. Preparation of durable flame-retardant cellulose fibers: A phosphorus-nitrogen high-efficiency composite flame retardant powder is prepared into a flame retardant finishing solution using distilled water, with the flame retardant accounting for 20-65%. Dicyandiamide is then added as a catalyst and urea as an accelerator to the prepared solution, and the solution is dissolved by water bath heating. The weight of dicyandiamide and urea is 1-15% of the effective weight of the flame retardant. Cellulose fibers are immersed in the flame-retardant finishing solution for 1-30 minutes. Excess flame retardant solution is removed using a rolling mill. After rolling, the liquid content of the cellulose fibers is 50-150%. Finally, the fibers are baked at 120-200℃ for 1-15 minutes to obtain durable flame-retardant cellulose fibers.

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

3. A durable flame-retardant yarn, characterized in that, It is made by blending the durable flame-retardant cellulose fiber of claim 1 with at least one other fiber, and the mass content of the durable flame-retardant cellulose fiber in the yarn is ≥10%.

4. The durable flame-retardant yarn according to claim 3, characterized in that, The other fibers are selected from one or more of meta-aramid, para-aramid, modified acrylic, polyimide, PBO, PBI, viscose fiber, cotton fiber, and lyocell fiber.

5. A durable flame-retardant yarn according to claim 3 or 4, characterized in that, It is spun using ring spinning, vortex spinning, air-jet spinning or compact Sirospinning processes.

Images