Flame-retardant lyocell fibers and methods for making the same

Abstract

The present application relates to a kind of flame-retardant lyocell fiber and its preparation method, belong to flame-retardant fiber technical field, at least one of the problems such as poor flame-retardant durability of flame-retardant lyocell fiber in prior art, high energy consumption, insufficient fiber specific strength, poor spinning process stability is solved.The present application provides a kind of flame-retardant lyocell fiber, including fiber core body and the skin layer directly formed on the surface layer of fiber core body, the fiber core body includes first flame retardant and cellulose, the skin layer includes the modified graphene oxide of second flame retardant loading.The flame-retardant lyocell fiber provided by the present application has a double-layer structure of "fiber core body + skin layer", the fiber core body has low flame retardant content, improves the specific strength and comprehensive performance of fiber;Skin layer has high flame retardant content, good flame-retardant performance, and the fiber surface layer of fiber core body forms a whole, completely avoids the problem of falling off, and has good flame-retardant durability.

Description

Technical Field

[0001] This invention relates to the field of flame-retardant fiber technology, and in particular to a flame-retardant lyocell fiber and its preparation method. Background Technology

[0002] Lyocell fiber, as a new generation of regenerated cellulose fiber, possesses high polymerization, crystallinity, and orientation, resulting in excellent mechanical properties, water absorption and swelling properties, and outstanding fibrillation characteristics. However, Lyocell fiber is flammable, and flame-retardant modification to obtain flame-retardant Lyocell fiber with good flame-retardant properties has always been a key research topic in the field of fiber modification. Flame-retardant Lyocell fiber has the characteristics of resisting melt dripping and not producing dense smoke, and its strength reduction after flame-retardant treatment is not as significant as that of flame-retardant viscose, thus attracting much attention.

[0003] Currently, there are two main methods for flame-retardant modification of lyocell fibers:

[0004] (1) Flame retardant treatment of lyocell fabric is carried out by preparing flame retardant and then finishing the fabric. The flame retardant is attached to the fiber surface. This treatment has problems such as uncontrollable uniformity of flame retardant coverage, poor flame retardant durability, easy peeling of flame retardant layer, and high energy consumption in the preparation process.

[0005] (2) The flame retardant is prepared into an NMMO solution and blended with it before lyocell spinning. This treatment method (blending) has very high requirements for the preparation and selection of flame retardants, and must take into account acid and alkali resistance, heat resistance, dispersibility and compatibility with the NMMO system. At the same time, it has a certain impact on the stability of the lyocell fiber spinning process. In particular, this treatment method requires the addition of a large amount of flame retardant to the fiber to obtain a better flame retardant effect. Generally, the addition amount is 15-50 wt.%. Under normal circumstances, the higher the flame retardant content, the better the flame retardant effect, but the fiber properties will decrease, especially the fiber specific strength will decrease significantly.

[0006] In conclusion, it is necessary to provide a flame-retardant lyocell fiber and its preparation method to resolve the contradiction between flame retardancy and spinnability (mainly referring to fiber specific strength). Summary of the Invention

[0007] Based on the above analysis, the present invention aims to provide a flame-retardant lyocell fiber and its preparation method to solve at least one of the following problems of existing flame-retardant lyocell fibers: poor flame-retardant durability, easy peeling of flame-retardant layer, high energy consumption in preparation, insufficient fiber specific strength, and poor stability of spinning process.

[0008] The present invention provides a flame-retardant lyocell fiber, comprising a fiber core and a sheath formed directly on the surface of the fiber core, wherein the fiber core comprises a first flame retardant and cellulose, and the sheath comprises modified graphene oxide loaded with a second flame retardant.

[0009] Specifically, the fiber core is formed by spinning a spinning solution containing a first flame retardant and cellulose.

[0010] Furthermore, the skin layer is formed directly on the surface of the fiber core in a coagulation bath containing modified graphene oxide loaded with a second flame retardant.

[0011] Furthermore, the skin layer is formed directly on the surface of the fiber core through a double diffusion effect and a micro-swelling effect.

[0012] Specifically, the first flame retardant is one or more of kaolin, montmorillonite, silica powder, and talc.

[0013] Specifically, the first flame retardant in the fiber core has a mass content of 8-11%, and / or the diameter of the fiber core is 7-12 μm.

[0014] Specifically, the second flame retardant is a mixture of component A and component B, with the mass ratio of component A to component B being 1:1 to 9;

[0015] Component A is one of melamine, dicyandiamide, guanidine carbonate, guanidine phosphate, condensed guanidine phosphate, guanidine aminosulfonate, and their derivatives; component B is tetramethylolphosphine sulfate or... KWB.

[0016] Specifically, in the modified graphene oxide loaded with the second flame retardant, the mass ratio of the second flame retardant to the graphene oxide is 10 to 20:1.

[0017] Specifically, the modified graphene oxide content in the skin layer is 0.5-2% by mass; and / or the thickness of the skin layer is 0.5-2 μm.

[0018] The present invention also provides a method for preparing the flame-retardant lyocell fiber, comprising the following specific steps:

[0019] S1: Take the dispersant, the first flame retardant, and deionized water to prepare the first flame retardant dispersion;

[0020] S2: After mixing the first flame retardant dispersion with cellulose pulp and the first NMMO aqueous solution, the mixture is heated, dissolved, and dehydrated to obtain the spinning solution;

[0021] S3: Prepare a modified graphene oxide dispersion loaded with a second flame retardant, and mix the modified graphene oxide dispersion with a second NMMO aqueous solution to obtain a solution for coagulation bath.

[0022] S4: After the spinning solution exits the fiber, it enters the coagulation bath and undergoes post-treatment to obtain the flame-retardant lyocell fiber.

[0023] Specifically, in step S1, the composition of the first flame retardant dispersion is, by mass, 0.5 to 2 parts of dispersant, 5 to 15 parts of the first flame retardant, and 80 to 100 parts of water; wherein the dispersant is a modified lignin sulfonate dispersant.

[0024] Specifically, in step S2, the mass ratio of the first flame retardant dispersion, cellulose pulp, and the first NMMO aqueous solution is 10-20:55-65:20-25; wherein, the NMMO mass concentration in the first NMMO aqueous solution is 50%, and the NMMO mass concentration in the spinning solution is 72-88%.

[0025] Specifically, in step S3, the volume ratio of the modified graphene oxide dispersion to the second NMMO aqueous solution is 1:1; wherein the mass concentration of the modified graphene oxide dispersion is 5% to 15%, and the solvent is water; the mass concentration of NMMO in the second NMMO aqueous solution is 10% to 20%.

[0026] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0027] 1. The flame-retardant lyocell fiber provided by this invention has good flame-retardant properties, with a limiting oxygen index (LOI) ≥ 28%, and the flame-retardant skin has good uniformity, making it difficult (or almost impossible) to fall off. In addition, the fiber has excellent properties and high specific strength.

[0028] The present invention provides a flame-retardant lyocell fiber, comprising a fiber core and a sheath formed directly on the surface of the fiber core, wherein the fiber core comprises a first flame retardant and cellulose, and the sheath comprises modified graphene oxide loaded with a second flame retardant.

[0029] The skin layer is obtained by introducing modified graphene oxide into the surface layer of the fiber core, and the fiber core and the skin layer are a single unit. Specifically, due to the double diffusion effect, the modified graphene oxide enters the surface layer of the fiber core from the coagulation bath solution; at the same time, the modified graphene oxide enters the surface fiber, and undergoes a slight volume expansion due to the micro-swelling effect, thereby forming a structure different from the interior of the fiber core, which is the skin layer described in this invention.

[0030] It is worth emphasizing that the above-mentioned "fiber core + sheath" structure is significantly different from existing core-sheath composite fibers.

[0031] In this invention, to achieve the flame-retardant effect of the skin layer, modified graphene oxide (GO) loaded with a second flame retardant is used as its main component. Due to the high specific surface area and abundant active groups of graphene oxide, the second flame retardant can be firmly adsorbed on the GO surface without affecting its flame-retardant performance. Moreover, since graphene oxide provides better sealing and thermal conductivity, the skin layer can better absorb heat, promote char formation and self-extinguishing, and the flame-retardant performance is further improved.

[0032] In the preparation process of flame-retardant fibers, before the inner core fibers are completely solidified, a solution containing graphene oxide is used for treatment in the coagulation bath stage. Due to the double diffusion effect and micro-swelling effect, the modified graphene oxide in the solution enters into the surface fibers of the core to form a flame-retardant skin layer. Therefore, the skin layer and the core are actually a whole. The modified graphene oxide in the skin layer and the surface fibers are inseparable, which fundamentally avoids the defects of uneven distribution and easy detachment of the flame-retardant skin layer added by post-processing in the existing technology. Unless the flame-retardant fiber is subjected to an external force sufficient to destroy the basic structure of the fiber, the skin layer will basically not detach.

[0033] It is worth noting that the flame retardant effect of the skin layer is actually the result of the combined effect of the first flame retardant and the second flame retardant, because the surface layer of the fiber core is actually composed of the first flame retardant and cellulose. In other words, the skin layer includes the first flame retardant, cellulose, and modified graphene oxide loaded with the second flame retardant.

[0034] Because the amount of flame retardant added in the core (i.e. the fiber body) of the present invention is very small, not exceeding 11 wt.%, the breaking strength of the flame retardant fiber is better than that of the flame retardant fiber in the prior art under the same flame retardant performance conditions, reaching 4.5 cN / dtex.

[0035] 2. The flame-retardant fiber disclosed in this invention uses relatively common and readily available raw materials, and the preparation process can be achieved with existing equipment. The operation is relatively simple, the process conditions are mild, and the production cycle is short. Moreover, it has good stability during the spinning process, and can achieve continuous factory production. It is suitable for widespread promotion and large-scale application, and has great market prospects and application potential.

[0036] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0037] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0038] Figure 1 This is a schematic diagram of the structure of flame-retardant lyocell fiber.

[0039] Figure label:

[0040] 1. First flame retardant; 2. Second flame retardant; 3. Fiber core; 4. Sheath. Detailed Implementation

[0041] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0042] The present invention provides a flame-retardant lyocell fiber, comprising a fiber core and a sheath formed directly on the surface of the fiber core, wherein the fiber core comprises a first flame retardant and cellulose, and the sheath comprises modified graphene oxide loaded with a second flame retardant.

[0043] Specifically, the fiber core is formed by spinning a spinning solution containing a first flame retardant and cellulose.

[0044] Furthermore, the skin layer is formed directly on the surface of the fiber core in a coagulation bath containing modified graphene oxide loaded with a second flame retardant.

[0045] Furthermore, the skin layer is formed directly on the surface of the fiber core through a double diffusion effect and a micro-swelling effect.

[0046] Specifically, due to the double diffusion effect, modified graphene oxide enters the surface layer of the fiber core from the coagulation bath solution; at the same time, modified graphene oxide enters the surface fiber, and undergoes a slight volume expansion due to the micro-swelling effect, thereby forming a structure different from the inside of the fiber core, which is the skin layer described in this invention.

[0047] It is worth emphasizing that the above-mentioned "fiber core + sheath" structure is significantly different from existing core-sheath composite fibers.

[0048] In this invention, to achieve the flame-retardant effect of the skin layer, modified graphene oxide (GO) loaded with a second flame retardant is used as its main component. Due to the high specific surface area and abundant active groups of graphene oxide, the second flame retardant can be firmly adsorbed on the GO surface without affecting its flame-retardant performance. Moreover, since graphene oxide provides better sealing and thermal conductivity, the skin layer can better absorb heat, promote char formation and self-extinguishing, and the flame-retardant performance is further improved.

[0049] In the preparation process of flame-retardant fibers, before the inner core fibers are completely solidified, a solution containing graphene oxide is used for treatment in the coagulation bath stage. Due to the double diffusion effect and micro-swelling effect, the modified graphene oxide in the solution enters into the surface fibers of the core to form a flame-retardant skin layer. Therefore, the skin layer and the core are actually a whole. The modified graphene oxide in the skin layer and the surface fibers are inseparable, which fundamentally avoids the defects of uneven distribution and easy detachment of the flame-retardant skin layer added by post-processing in the existing technology. Unless the flame-retardant fiber is subjected to an external force sufficient to destroy the basic structure of the fiber, the skin layer will basically not detach.

[0050] It is worth noting that the flame retardant effect of the skin layer is actually the result of the combined effect of the first flame retardant and the second flame retardant, because the surface layer of the fiber core is actually composed of the first flame retardant and cellulose. In other words, the skin layer includes the first flame retardant, cellulose, and modified graphene oxide loaded with the second flame retardant.

[0051] In this invention, the flame-retardant effect is achieved through a combination of "fiber core and outer layer." In practice, the flame-retardant effect of the outer layer is primary, while that of the fiber core is secondary. However, it is worth emphasizing that the addition of the first flame retardant to the fiber core is indispensable; otherwise, a situation may occur where the outer flame-retardant layer remains intact and still functions, but the core has already been damaged due to high temperatures.

[0052] Specifically, the first flame retardant is one or more of kaolin, montmorillonite, silica powder, and talc. The aforementioned first flame retardant is an inorganic flame retardant, which is easy to disperse, free of metal ion impurities, and easy to mix with NMMO solution, resulting in a high safety factor; flame retardants containing metal ions are prone to decomposition, which can seriously cause explosions.

[0053] Specifically, in the fiber core, the mass content of the first flame retardant is 8-11%, and / or the diameter of the fiber core is 7-12 μm. The core diameter mainly affects the fiber strength. Too low a content of the first flame retardant in the core will result in poor flame retardant performance; too high a content will damage the fiber strength. The diameter of the core determines the diameter of the final finished fiber. A core with the aforementioned diameter, while ensuring strength, is suitable for the preparation of various downstream products. A finished fiber diameter that is too low or too high is detrimental to subsequent processing and product manufacturing.

[0054] Because the amount of flame retardant added to the core (i.e., the fiber body) of this invention is very small, not exceeding 11 wt.%, under the same flame retardant performance conditions, the specific strength of the flame-retardant fiber is superior to that of existing flame-retardant lyocell fibers, and the breaking strength is not less than 4.5 cN / dtex. The strength meets the usage requirements and basically reaches the level of conventional lyocell fibers, while also exhibiting good spinnability. This good spinnability is mainly reflected in the following two aspects:

[0055] Physical properties: While ensuring the fiber breaking strength, it can spin finer fibers to meet most downstream application scenarios, and the fiber evenness and crimp stability are also good.

[0056] Appearance: The flame-retardant fibers provided by this invention are lint-free and have uniform coloring.

[0057] Specifically, the second flame retardant is a mixture of component A and component B, with the mass ratio of component A to component B being 1:1 to 9;

[0058] The second flame retardant in the above ratio can form a good nitrogen-phosphorus synergistic effect. The interaction between the two elements during pyrolysis and combustion enhances the flame retardant effect of the material. If the amount of any component added is too high or too low, it will destroy its synergistic effect and thus lead to a decrease in flame retardant ability.

[0059] Component A is one of melamine, dicyandiamide, guanidine carbonate, guanidine phosphate, condensed guanidine phosphate, guanidine aminosulfonate, and their derivatives; component B is tetramethylolphosphine sulfate or... KWB. The above-mentioned substances are easy to disperse and grind, and the particle size is easy to control. They are relatively mature commercial flame retardants that can be purchased directly. Commonly used specifications of the above-mentioned substances can meet the implementation needs of this invention.

[0060] Specifically, in the modified graphene oxide loaded with the second flame retardant, the mass ratio of the second flame retardant to graphene oxide is 10-20:1. The amount of the second flame retardant added is matched with the specific surface area and loading capacity of the graphene oxide; too much flame retardant cannot be stably loaded onto the graphene oxide, while too little flame retardant will lead to a decrease in flame retardant ability.

[0061] For example, the preparation process of modified graphene oxide is as follows: Graphene oxide is added to a dispersion vessel and stirred for 30 min to 1 h. Then, a second flame retardant is added in proportion, and the mixture is stirred for 10 min to 15 min. The mixture is then transferred to a basket mill or horizontal mill for grinding and dispersion at a speed of 1500 to 2500 rpm for 10 to 20 min. The modified graphene oxide is obtained when the particle size distribution is measured by a laser particle size analyzer and the particle size distribution is D90 ≤ 2 μm. Alternatively, an ultrasonic-assisted wet grinding and dispersion process can be used to prepare a dispersion of modified graphene oxide.

[0062] Specifically, the modified graphene oxide content in the skin layer is 0.5% to 2% of the fiber mass; and / or, the thickness of the skin layer is 0.5 to 2 μm. Specifically, the modified graphene oxide content in the skin layer is 0.5% to 2% of the fiber mass. Too low a content will impair flame retardant properties, while too high a content will reduce the strength of the finished fiber. The thickness of the skin layer is 0.5 to 2 μm, which is approximately the depth to which the modified graphene oxide can penetrate the skin layer. During the coagulation bath, the fiber undergoes a certain degree of stretching. At a certain spinning speed, the fiber molecular orientation is stable, and the depth to which the modified graphene oxide penetrates the skin is basically fixed. A skin layer that is too thin will impair the flame retardant effect, while a skin layer that is too thick will affect the overall performance of the fiber (mainly referring to strength).

[0063] The present invention also provides a method for preparing the flame-retardant lyocell fiber, comprising the following specific steps:

[0064] S1: Take the dispersant, the first flame retardant, and deionized water to prepare the first flame retardant dispersion;

[0065] S2: After mixing the first flame retardant dispersion with cellulose pulp and the first NMMO aqueous solution, the mixture is heated, dissolved, and dehydrated to obtain the spinning solution;

[0066] S3: Prepare a modified graphene oxide dispersion loaded with a second flame retardant, and mix the modified graphene oxide dispersion with a second NMMO aqueous solution to obtain a solution for coagulation bath.

[0067] S4: After the spinning solution exits the fiber, it enters the coagulation bath and undergoes post-treatment to obtain the flame-retardant lyocell fiber.

[0068] Specifically, in step S1, the first flame retardant dispersion comprises, by mass, 0.5-2 parts dispersant, 5-15 parts flame retardant, and 80-100 parts water. The dispersant is a modified lignin sulfonate dispersant; currently, considering both cost and dispersion effect, modified sodium lignin sulfonate is generally chosen, and commercially available models / specifications are sufficient for implementation. The addition of dispersant ensures uniform dispersion of the flame retardant; excessive dispersant will affect the rheological properties of the dispersion, thus affecting the mixing effect with the spinning solution; insufficient dispersant will affect the dispersion effect.

[0069] Specifically, in step S2, the mass ratio of the first flame retardant dispersion, cellulose pulp, and the first NMMO aqueous solution is 10-20:55-65:20-25. If the flame retardant content is too high, the dispersion stability will be poor, affecting the mixing effect and ultimately the fiber strength; if it is too low, the flame retardant effect will be affected. Cellulose pulp is the main matrix of the fiber, and its addition should be higher to ensure both flame retardant effect and dispersion performance. Verification has shown that an addition amount (mass ratio) of 55-65 is appropriate. The addition of the first NMMO aqueous solution is to ensure the viscosity of the spinning solution; the final NMMO concentration in the spinning solution will be adjusted subsequently through processes such as dehydration.

[0070] The first NMMO aqueous solution contains 50% NMMO by mass, while the spinning solution contains 72-88% NMMO by mass. These NMMO concentrations ensure the required spinning viscosity for dry-jet wet spinning. Dry-jet wet spinning requires a high-viscosity spinning solution, and the concentration and viscosity of NMMO are closely related; excessively high or low NMMO concentrations will result in unsatisfactory spinning solution viscosity. The NMMO concentration in the first NMMO aqueous solution should not be too low to avoid excessively long dehydration processes.

[0071] Specifically, in step S3, the volume ratio of the modified graphene oxide dispersion to the second NMMO aqueous solution is 1:1; wherein the mass concentration of the modified graphene oxide dispersion is 5%–15%, and the solvent is water; the mass concentration of NMMO in the second NMMO aqueous solution is 10%–20%. Excessive addition of the modified graphene oxide dispersion will result in poor coagulation, causing a rough skin layer and affecting quality; insufficient addition will result in insufficient loading of modified graphene oxide in the skin layer, affecting the flame retardant effect.

[0072] Specifically, the coagulation bath temperature is 15-30℃, such as 15, 18, 20, 23, 25, 28, and 30℃. If the coagulation bath temperature is too high, the fiber will not coagulate completely; if the coagulation bath temperature is too low, the fiber will coagulate too quickly, and the modified graphene oxide will penetrate the fiber surface layer too shallowly, both of which are detrimental to the overall performance and flame retardant properties of the fiber.

[0073] Specifically, the structure and size of the sheath are also related to the spinning speed. Experiments have shown that when the spinning speed is 40-60 m / min, the flame-retardant fiber has good overall performance.

[0074] Preferably, the coagulation bath can be equipped with an automatic circulating liquid supply component to ensure the stability of the concentration of modified graphene oxide around the fiber in the coagulation bath.

[0075] Specifically, the post-processing steps in step S4 include washing, chopping, steaming, and drying.

[0076] Example 1

[0077] S1: Measure modified sodium lignosulfonate, kaolin, and deionized water in a ratio of 0.5:10:80 to prepare the first flame retardant dispersion;

[0078] S2: After mixing the first flame retardant dispersion with cellulose pulp and the first NMMO aqueous solution, the mixture is heated, dissolved, and dehydrated to obtain a spinning solution, wherein the mass ratio of the first flame retardant dispersion, cellulose pulp, and the first NMMO aqueous solution is 15:58:22.

[0079] S3: A modified graphene oxide dispersion loaded with a second flame retardant was prepared by ultrasonic-assisted wet grinding and dispersion process. The mass ratio of the second flame retardant to the graphene oxide in the modified graphene oxide was 10:1. The modified graphene oxide dispersion was mixed with a second NMMO aqueous solution to obtain a solution for coagulation bath.

[0080] The second flame retardant is a mixture of melamine and tetramethylolphosphine sulfate, with a mass ratio of melamine to tetramethylolphosphine sulfate of 1:2.

[0081] The volume ratio of the modified graphene oxide dispersion to the second NMMO aqueous solution is 1:1; wherein the mass concentration of the modified graphene oxide dispersion is 10% and the solvent is water; the mass concentration of NMMO in the second NMMO aqueous solution is 13%.

[0082] S4: After the spinning solution is filtered and degassed, it is fed into a coagulation bath through a metering pump and spinneret. The coagulation bath temperature is 25℃ and the spinning speed is 50m / min. After washing, cutting, cooking, drying and packaging, flame-retardant lyocell fibers are obtained.

[0083] Tests showed that the LOI index of the above-mentioned lyocell fiber was 28.5%, the breaking strength was 4.5 cN / dtex, and the LOI index could be maintained above 28% after 30 washes.

[0084] Example 2

[0085] S1: Measure modified sodium lignosulfonate, montmorillonite, and deionized water in a ratio of 2:8:95 to prepare the first flame retardant dispersion;

[0086] S2: After mixing the first flame retardant dispersion with cellulose pulp and the first NMMO aqueous solution, the mixture is heated, dissolved, and dehydrated to obtain a spinning solution, wherein the mass ratio of the first flame retardant dispersion, cellulose pulp, and the first NMMO aqueous solution is 10:65:21.

[0087] S3: A modified graphene oxide dispersion loaded with a second flame retardant was prepared by ultrasonic-assisted wet grinding and dispersion process. The mass ratio of the second flame retardant to the graphene oxide in the modified graphene oxide was 13:1. The modified graphene oxide dispersion was mixed with a second NMMO aqueous solution to obtain a solution for coagulation bath.

[0088] Among them: the second flame retardant is dicyandiamide and A mixture of KWB components, including dicyandiamide and... The mass ratio of KWB is 1:7;

[0089] The volume ratio of the modified graphene oxide dispersion to the second NMMO aqueous solution is 1:1; wherein the mass concentration of the modified graphene oxide dispersion is 5% and the solvent is water; the mass concentration of NMMO in the second NMMO aqueous solution is 17%.

[0090] S4: After the spinning solution is filtered and degassed, it is fed into a coagulation bath through a metering pump and spinneret. The coagulation bath temperature is 25℃ and the spinning speed is 60m / min. After washing, cutting, cooking, drying and packaging, flame-retardant lyocell fibers are obtained.

[0091] Tests showed that the LOI index of the above-mentioned lyocell fiber was 28.3%, the breaking strength was 4.7 cN / dtex, and the LOI index could be maintained above 28.1% after 30 washes.

[0092] Example 3

[0093] S1: Measure modified sodium lignosulfonate, silica powder, and deionized water in a ratio of 1:5:85 to prepare the first flame retardant dispersion;

[0094] S2: After mixing the first flame retardant dispersion with cellulose pulp and the first NMMO aqueous solution, the mixture is heated, dissolved, and dehydrated to obtain a spinning solution, wherein the mass ratio of the first flame retardant dispersion, cellulose pulp, and the first NMMO aqueous solution is 13:55:23.

[0095] S3: A modified graphene oxide dispersion loaded with a second flame retardant was prepared by ultrasonic-assisted wet grinding and dispersion process. The mass ratio of the second flame retardant to the graphene oxide in the modified graphene oxide was 15:1. The modified graphene oxide dispersion was mixed with a second NMMO aqueous solution to obtain a solution for coagulation bath.

[0096] The second flame retardant is a mixture of guanidine carbonate and tetramethylolphosphine sulfate, with a mass ratio of guanidine carbonate to tetramethylolphosphine sulfate of 1:5.

[0097] The volume ratio of the modified graphene oxide dispersion to the second NMMO aqueous solution is 1:1; wherein the mass concentration of the modified graphene oxide dispersion is 8% and the solvent is water; the mass concentration of NMMO in the second NMMO aqueous solution is 15%.

[0098] S4: After the spinning solution is filtered and degassed, it is fed into a coagulation bath through a metering pump and spinneret. The coagulation bath temperature is 25℃ and the spinning speed is 55m / min. After washing, cutting, cooking, drying and packaging, flame-retardant lyocell fibers are obtained.

[0099] Tests showed that the LOI index of the above-mentioned lyocell fiber was 28.7%, the breaking strength was 4.8 cN / dtex, and the LOI index could be maintained above 28.4% after 30 washes.

[0100] Example 4

[0101] S1: Measure the modified sodium lignosulfonate, the mixed powder of "kaolin + silica powder" (mass ratio 1:1), and deionized water, and prepare the first flame retardant dispersion in a ratio of 1.5:13:100;

[0102] S2: After mixing the first flame retardant dispersion with cellulose pulp and the first NMMO aqueous solution, the mixture is heated, dissolved, and dehydrated to obtain a spinning solution, wherein the mass ratio of the first flame retardant dispersion, cellulose pulp, and the first NMMO aqueous solution is 20:60:25.

[0103] S3: A modified graphene oxide dispersion loaded with a second flame retardant was prepared by ultrasonic-assisted wet grinding and dispersion process. The mass ratio of the second flame retardant to the graphene oxide in the modified graphene oxide was 19:1. The modified graphene oxide dispersion was mixed with a second NMMO aqueous solution to obtain a solution for coagulation bath.

[0104] Among them: the second flame retardant is guanidine aminosulfonate and The mixture of KWB components, including guanidine aminosulfonate and... The mass ratio of KWB is 1:3;

[0105] The volume ratio of the modified graphene oxide dispersion to the second NMMO aqueous solution is 1:1; wherein the mass concentration of the modified graphene oxide dispersion is 15% and the solvent is water; the mass concentration of NMMO in the second NMMO aqueous solution is 18%.

[0106] S4: After the spinning solution is filtered and degassed, it is fed into a coagulation bath through a metering pump and spinneret. The coagulation bath temperature is 25℃ and the spinning speed is 45m / min. After washing, cutting, cooking, drying and packaging, flame-retardant lyocell fibers are obtained.

[0107] Tests showed that the LOI index of the above-mentioned lyocell fiber was 29.1%, the breaking strength was 4.6 cN / dtex, and the LOI index could be maintained above 28.6% after 30 washes.

[0108] Example 5

[0109] S1: Measure modified sodium lignosulfonate, talc powder, and deionized water in a ratio of 1:15:90 to prepare the first flame retardant dispersion;

[0110] S2: After mixing the first flame retardant dispersion with cellulose pulp and the first NMMO aqueous solution, the mixture is heated, dissolved, and dehydrated to obtain a spinning solution, wherein the mass ratio of the first flame retardant dispersion, cellulose pulp, and the first NMMO aqueous solution is 17:57:24.

[0111] S3: A modified graphene oxide dispersion loaded with a second flame retardant was prepared by ultrasonic-assisted wet grinding and dispersion process. The mass ratio of the second flame retardant to the graphene oxide in the modified graphene oxide was 17:1. The modified graphene oxide dispersion was mixed with a second NMMO aqueous solution to obtain a solution for coagulation bath.

[0112] Among them: the second flame retardant is condensed guanidine phosphate and A mixture of KWB components, including condensed guanidine phosphate and... The mass ratio of KWB is 1:9;

[0113] The volume ratio of the modified graphene oxide dispersion to the second NMMO aqueous solution is 1:1; wherein the mass concentration of the modified graphene oxide dispersion is 13% and the solvent is water; the mass concentration of NMMO in the second NMMO aqueous solution is 10%.

[0114] S4: After the spinning solution is filtered and degassed, it is fed into a coagulation bath through a metering pump and spinneret. The coagulation bath temperature is 25℃ and the spinning speed is 40m / min. After washing, cutting, cooking, drying and packaging, flame-retardant lyocell fibers are obtained.

[0115] Tests showed that the LOI index of the above-mentioned lyocell fiber was 28.9%, the breaking strength was 4.5 cN / dtex, and the LOI index could be maintained above 28.5% after 30 washes.

[0116] The lyocell fibers prepared in Examples 1-5 had a diameter of 13 μm (with unavoidable errors), an initial LOI index of no less than 28.3%, and a breaking strength ≥4.5 cN / dtex. After 30 washes, the LOI index remained above 28.1%, demonstrating excellent flame retardant effect and fiber strength. In comparison, fibers with higher flame retardant content and lower spinning speed (slightly thicker sheath) exhibited better flame retardant performance, but with a slight decrease in breaking strength. Overall, however, they showed superior performance and represented a significant improvement over existing technologies.

[0117] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A flame-retardant lyocell fiber, characterized in that, The invention comprises a fiber core and a sheath formed directly on the surface of the fiber core. The fiber core includes a first flame retardant and cellulose, and the sheath includes the first flame retardant, cellulose, and modified graphene oxide loaded with a second flame retardant. The fiber core is spun from a spinning solution containing the first flame retardant and cellulose. The sheath is formed directly on the surface of the fiber core by the fiber core entering a coagulation bath containing modified graphene oxide loaded with the second flame retardant. The sheath is formed directly on the surface of the fiber core through a double diffusion effect and a micro-swelling effect.

2. The flame-retardant lyocell fiber according to claim 1, characterized in that, The first flame retardant is one or more of kaolin, montmorillonite, silica powder, and talc.

3. The flame-retardant lyocell fiber according to claim 1, characterized in that, In the fiber core, the mass content of the first flame retardant is 8-11%, and / or the diameter of the fiber core is 7-12 μm.

4. The flame-retardant lyocell fiber according to claim 1, characterized in that, The second flame retardant is a mixture of component A and component B, wherein the mass ratio of component A to component B is 1:1 to 9; Component A is one of melamine, dicyandiamide, guanidine carbonate, guanidine phosphate, condensed guanidine phosphate, guanidine aminosulfonate, and their derivatives; component B is tetramethylolphosphine sulfate or... .

5. The flame-retardant lyocell fiber according to claim 1, characterized in that, In the modified graphene oxide loaded with the second flame retardant, the mass ratio of the second flame retardant to the graphene oxide is 10 to 20:

1.

6. The flame-retardant lyocell fiber according to claim 1, characterized in that, The modified graphene oxide content in the skin layer is 0.5-2% by mass; and / or the thickness of the skin layer is 0.5-2 μm.

7. A method for preparing flame-retardant lyocell fiber according to any one of claims 1 to 6, characterized in that, The specific steps include the following: S1: Take the dispersant, the first flame retardant, and deionized water to prepare the first flame retardant dispersion; S2: After mixing the first flame retardant dispersion with cellulose pulp and the first NMMO aqueous solution, the mixture is heated, dissolved, and dehydrated to obtain the spinning solution; S3: Prepare a modified graphene oxide dispersion loaded with a second flame retardant, and mix the modified graphene oxide dispersion with a second NMMO aqueous solution to obtain a solution for coagulation bath. S4: After the spinning solution exits the fiber, it enters the coagulation bath and undergoes post-treatment to obtain the flame-retardant lyocell fiber.

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