Cellulose nanocrystal colored lyocell fiber and method of making the same

Abstract

The application provides a cellulose nanocrystal colored lyocell fiber and a preparation method thereof. The lyocell fiber technology field is related, and the preparation method of the cellulose nanocrystal colored lyocell fiber comprises the following steps: providing a spinning solution, wherein the spinning solution comprises cellulose pulp, N-methyl morpholine-N-oxide solvent and cellulose nanocrystal; and solidifying the spinning solution in a coagulation bath to obtain the cellulose nanocrystal colored lyocell fiber; wherein the coagulation bath comprises an ammonium sulfate solution. In the technical scheme in the application, the use of traditional chemical dyes can be reduced in the preparation process, the cellulose nanocrystal is introduced into the spinning solution and is solidified to form a fiber, the optical properties of the cellulose nanocrystal are utilized to impart the lyocell fiber with color development effect, and therefore, the green coloring of the fiber is realized.

Description

Technical Field

[0001] This invention relates to the field of lyocell fiber technology, specifically to a cellulose nanocrystal color-developing lyocell fiber and its preparation method. Background Technology

[0002] Lyocell fiber, as an environmentally friendly regenerated cellulose fiber, is increasingly widely produced and used. However, the current coloring of lyocell fibers and fabrics relies almost entirely on chemical dyes. Traditional chemical dyeing processes have significant drawbacks: firstly, the production process consumes large amounts of water resources and discharges wastewater containing residual dyes, heavy metals, and various chemical auxiliaries, causing serious environmental pollution; secondly, some synthetic dyes may irritate or sensitize human skin, posing health risks; and thirdly, dyed fibers are prone to fading after repeated washing or exposure to sunlight, and colorfastness needs improvement. With increasingly stringent global environmental regulations and growing consumer demand for healthy and safe products, developing a green coloring technology that does not require chemical dyes has become an important research direction for the textile industry. Summary of the Invention

[0003] In view of the technical problems existing in the background art, this application provides a cellulose nanocrystal colored lyocell fiber and its preparation method. The preparation method of the cellulose nanocrystal colored lyocell fiber can reduce the use of traditional chemical dyes in the preparation process. By introducing cellulose nanocrystals into the spinning solution and solidifying them, the optical properties of the cellulose nanocrystals themselves are used to give the lyocell fiber a coloring effect, thereby achieving green coloring of the fiber.

[0004] Lyocell fiber, as an environmentally friendly regenerated cellulose fiber, is increasingly widely produced and used. However, the current coloring of lyocell fibers and fabrics relies almost entirely on chemical dyes. Traditional chemical dyeing processes have significant drawbacks: firstly, the production process consumes large amounts of water resources and discharges wastewater containing residual dyes, heavy metals, and various chemical auxiliaries, causing serious environmental pollution; secondly, some synthetic dyes may irritate or sensitize human skin, posing health risks; and thirdly, dyed fibers are prone to fading after repeated washing or exposure to sunlight, and colorfastness needs improvement. With increasingly stringent global environmental regulations and growing consumer demand for healthy and safe products, developing a green coloring technology that does not require chemical dyes has become an important research direction for the textile industry.

[0005] To address the aforementioned technical problems, this invention proposes a method for preparing cellulose nanocrystalline color-developing Lyocell fibers, comprising: The spinning solution is provided, comprising cellulose pulp, N-methylmorpholine-N-oxide solvent, and cellulose nanocrystals; The spinning solution was solidified in a coagulation bath to obtain cellulose nanocrystal colored lyocell fibers; wherein the coagulation bath included an ammonium sulfate solution.

[0006] In the spinning solution, the mass of the cellulose pulp is 4%-5% of the mass of the N-methylmorpholine-N-oxide solvent; and / or, In the spinning solution, the mass of cellulose nanocrystals is 0.3%-0.6% of the mass of the N-methylmorpholine-N-oxide solvent; and / or, In N-methylmorpholine-N-oxide solvent, the mass fraction of N-methylmorpholine-N-oxide is 40%-60%.

[0007] Furthermore, the spinning solution also includes stabilizers.

[0008] Furthermore, in the spinning solution, the mass of the stabilizer is 0.01%-0.04% of the mass of the N-methylmorpholine-N-oxide solvent; and / or, Stabilizers include at least one of calcium-zinc stabilizers, vitamin E, tea polyphenols, rosemary extract, and propyl gallate.

[0009] Furthermore, in the ammonium sulfate solution, the mass fraction of ammonium sulfate is 5wt%-50wt%; and / or, The temperature of the coagulation bath is 15℃-65℃; and / or, The coagulation bath has multiple stages.

[0010] Furthermore, a spinning solution is provided, comprising cellulose pulp, N-methylmorpholine-N-oxide solvent, and cellulose nanocrystals, including: Cellulose pulp and N-methylmorpholine-N-oxide solvent are mixed and ultrasonically treated to obtain a first liquid. Cellulose nanocrystals are then added to the first liquid for dispersion treatment to obtain a spinning solution.

[0011] Furthermore, the power of the ultrasonic treatment is 700W-1000W; and / or, The ultrasonic treatment time is 10 min-60 min; and / or, The dispersion treatment temperature is 5℃-55℃; and / or, The dispersion treatment time is 1-3 hours; and / or, Dispersion processing includes stirring.

[0012] Furthermore, the spinning solution is solidified in a coagulation bath to obtain cellulose nanocrystal color-developed Lyocell fibers, including: The spinning solution is spun to obtain the precursor. The precursor is solidified in a coagulation bath to obtain the intermediate; After washing and drying the intermediate, cellulose nanocrystal colored Lyocell fiber is obtained.

[0013] Furthermore, the orifice diameter of the spinning needle in the spinning process is 0.18mm-0.84mm.

[0014] Secondly, the present invention also proposes a cellulose nanocrystal color-developing lyocell fiber, which is prepared by the above-mentioned method for preparing cellulose nanocrystal color-developing lyocell fiber.

[0015] The beneficial effects of this invention are: In the technical solution of this invention, cellulose nanocrystals are introduced into the spinning solution, and color is generated by modulating light through the microscopic physical structure of the material. Cellulose nanocrystals, as a nanomaterial extractable from natural cellulose, can self-assemble under specific conditions to form an ordered arrangement with a chiral nematic structure, thereby producing a vibrant structural color. This color development method does not rely on chemical dyes, reducing environmental pollution problems caused by traditional dyeing processes at the source. Simultaneously, cellulose nanocrystals, as a natural biomass material, have good biocompatibility and biodegradability, similar to lyocell fiber, which can improve the overall biocompatibility of the fiber. Furthermore, the cellulose nanocrystal-colored lyocell fiber prepared by this method has cellulose nanocrystals cross-linked in the molecular network structure of the lyocell fiber, and the resulting structural color has high stability and is not easily faded by washing, friction, or light exposure. Compared with traditionally dyed fibers, the colored lyocell fiber prepared by this invention can maintain the vibrancy and durability of the color during long-term use, extending the product's lifespan.

[0016] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in this application will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort.

[0018] Figure 1 This is an electronic image of Embodiment 1 of the present invention; Figure 2 This is an electronic image of Embodiment 2 of the present invention; Figure 3 This is an electronic image of Embodiment 3 of the present invention; Figure 4 This is an electronic image of Embodiment 4 of the present invention; Figure 5This is an electronic image of Embodiment 5 of the present invention; Figure 6 This is an electronic image of Embodiment 6 of the present invention; Figure 7 This is an electronic image of Embodiment 7 of the present invention; Figure 8 This is an electronic image of Comparative Example 1 of the present invention; Figure 9 This is an electronic image of Comparative Example 2 of the present invention; Figure 10 This is an electronic image of Comparative Example 3 of the present invention; Figure 11 This is an SEM (Scanning Electron Microscope) image of Embodiment 1 of the present invention; Figure 12 This is a POM (Polarized Optical Microscope) image of Embodiment 1 of the present invention. Detailed Implementation

[0019] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[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 application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0021] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0022] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0023] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0024] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0025] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0026] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0027] Lyocell fiber, as an environmentally friendly regenerated cellulose fiber, is increasingly widely produced and used. However, the current coloring of lyocell fibers and fabrics relies almost entirely on chemical dyes. Traditional chemical dyeing processes have significant drawbacks: firstly, the production process consumes large amounts of water resources and discharges wastewater containing residual dyes, heavy metals, and various chemical auxiliaries, causing serious environmental pollution; secondly, some synthetic dyes may irritate or sensitize human skin, posing health risks; and thirdly, dyed fibers are prone to fading after repeated washing or exposure to sunlight, and colorfastness needs improvement. With increasingly stringent global environmental regulations and growing consumer demand for healthy and safe products, developing a green coloring technology that does not require chemical dyes has become an important research direction for the textile industry.

[0028] To address the aforementioned technical problems, in a first aspect, this invention proposes a method for preparing cellulose nanocrystalline color-developing Lyocell fibers, comprising: The spinning solution is provided, comprising cellulose pulp, N-methylmorpholine-N-oxide solvent, and cellulose nanocrystals; The spinning solution was solidified in a coagulation bath to obtain cellulose nanocrystal colored lyocell fibers; wherein the coagulation bath included an ammonium sulfate solution.

[0029] In the technical solution of this invention, cellulose nanocrystals are introduced into the spinning solution, and color is generated by modulating light through the microscopic physical structure of the material. Cellulose nanocrystals, as a nanomaterial extractable from natural cellulose, can self-assemble under specific conditions to form an ordered arrangement with a chiral nematic structure, thereby producing a vibrant structural color. This color development method does not rely on chemical dyes, reducing environmental pollution problems caused by traditional dyeing processes at the source. Simultaneously, cellulose nanocrystals, as a natural biomass material, have good biocompatibility and biodegradability, similar to lyocell fiber, which can improve the overall biocompatibility of the fiber. Furthermore, the cellulose nanocrystal-colored lyocell fiber prepared by this method has cellulose nanocrystals cross-linked in the molecular network structure of the lyocell fiber, and the resulting structural color has high stability and is not easily faded by washing, friction, or light exposure. Compared with traditionally dyed fibers, the colored lyocell fiber prepared by this invention can maintain the vibrancy and durability of the color during long-term use, extending the product's lifespan. Furthermore, the coagulation bath provides a controllable environment for the solidification of the spinning solution, allowing the solvent in the spinning solution to diffuse and exchange in an orderly manner, thereby promoting the rearrangement and solidification of cellulose molecular chains. The structure and properties of the fiber can be controlled by parameters such as the composition, concentration, and temperature of the coagulation bath. Using ammonium sulfate solution as the coagulation bath, its high ionic strength can effectively promote the solidification of cellulose nanocrystals in the spinning solution within the fiber. In addition, as a neutral salt, ammonium sulfate is less likely to chemically react with cellulose or cellulose nanocrystals in the spinning solution during the solidification process, reducing interference with the formation of structural colors in the fiber and helping to maintain the orderly arrangement of the chiral nematic structure of the cellulose nanocrystals, thus ensuring the stability of the color development effect.

[0030] It can be explained that spinning solutions can be prepared by using raw materials in a specific ratio, resulting in better spinnability. At the same time, the color change of regenerated cellulose fibers can be improved, making them display brighter and richer colors.

[0031] In some embodiments, the mass of the cellulose pulp in the spinning solution is 4%-5% of the mass of the N-methylmorpholine-N-oxide solvent.

[0032] In this embodiment, by limiting the mass of cellulose pulp within this range, the spinning solution can have a suitable viscosity to meet the requirements of the spinning process, ensuring the continuity and uniformity of fiber formation. In addition, it can provide sufficient space for the uniform dispersion of cellulose nanocrystals.

[0033] In some embodiments, the mass of cellulose nanocrystals in the spinning solution is 0.3%-0.6% of the mass of the N-methylmorpholine-N-oxide solvent.

[0034] In this embodiment, by limiting the mass of cellulose nanocrystals to this range, the helical structure of cellulose nanocrystals can be controlled as a source of structural color, so that they exhibit a clear and uniform structural color.

[0035] In some embodiments, the mass fraction of N-methylmorpholine-N-oxide in the N-methylmorpholine-N-oxide solvent is 40%-60%.

[0036] In this embodiment, by limiting the mass of N-methylmorpholine-N-oxide to this range, cellulose pulp can be effectively dissolved to form a stable spinning solution system, ensuring that the cellulose molecular chains are fully extended, which facilitates the subsequent uniform mixing with cellulose nanocrystals and the curing and shaping of fibers.

[0037] In some embodiments, the spinning solution also includes a stabilizer.

[0038] In this embodiment, the addition of a stabilizer can reduce the thermal oxidative degradation and hydrolytic degradation of the fiber during the spinning process and improve the fiber strength.

[0039] In some embodiments, the mass of the stabilizer in the spinning solution is 0.01%-0.04% of the mass of the N-methylmorpholine-N-oxide solvent.

[0040] In this embodiment, by limiting the mass of the stabilizer to this range, its stabilizing effect can be effectively exerted to inhibit the oxidation, hydrolysis and other degradation reactions of the spinning solution during preparation and subsequent spinning process, while avoiding the negative impact on the rheological properties of the spinning solution and the mechanical properties of the fiber due to excessive addition, thus ensuring the fiber forming quality and overall performance.

[0041] In some embodiments, the stabilizer includes at least one of calcium-zinc stabilizer, vitamin E, tea polyphenols, rosemary extract, and propyl gallate.

[0042] In this embodiment, by selecting the aforementioned natural or environmentally friendly stabilizers, not only can the stability of the spinning solution and fibers be effectively improved, but they can also be compatible with the natural properties of cellulose nanocrystals and lyocell fibers, reducing the introduction of new chemical pollution. Specifically, natural antioxidants such as vitamin E, tea polyphenols, and rosemary extract can delay the oxidative degradation of cellulose molecules in the spinning solution by capturing free radicals and inhibiting oxidative chain reactions, while also possessing good biocompatibility and biodegradability. Calcium-zinc stabilizers, as an environmentally friendly composite stabilizer, can effectively inhibit the hydrolysis of cellulose under high temperatures or specific chemical environments. Working synergistically with other stabilizers, they can improve the weather resistance and service life of fibers in multiple ways.

[0043] In some embodiments, the mass fraction of the solute in the coagulation bath is 5wt%-50wt%.

[0044] In this embodiment, by limiting the mass fraction of the solute in the coagulation bath to this range, the solidification rate of the spinning solution can be precisely controlled. Furthermore, by adjusting the concentration, the arrangement density of the cellulose nanocrystals can be fine-tuned, thereby achieving subtle control over the structural color tone to meet different color requirements.

[0045] In some embodiments, the temperature of the coagulation bath is 15°C-65°C.

[0046] In this embodiment, by controlling the temperature of the coagulation bath within this range, the solvent diffusion rate and the mobility of cellulose molecular chains can be synergistically regulated.

[0047] In some embodiments, the coagulation bath is provided with multiple stages.

[0048] In this embodiment, by setting up multiple coagulation baths, the solidification process of the spinning solution can be controlled stepwise. For example, the first coagulation bath can use a high-concentration ammonium sulfate solution to quickly fix the basic morphology of the fiber and the initial arrangement of cellulose nanocrystals, preventing fiber deformation in subsequent processing. Subsequent coagulation baths can gradually reduce the concentration of the ammonium sulfate solution or adjust the temperature to allow the solvent inside the fiber to diffuse more fully, reducing internal fiber stress and promoting a more stable bond between cellulose molecular chains and cellulose nanocrystals, thus optimizing the fiber's mechanical properties and the uniformity of its structural color. The multi-stage coagulation baths allow for more precise control of the fiber forming process, reducing fiber structural defects caused by excessively fast or slow single-stage solidification rates, such as surface roughness, excessively high internal porosity, or uneven distribution of structural color, thereby improving the quality and performance stability of the final colored lyocell fiber.

[0049] In some embodiments, a spinning solution is provided, comprising cellulose pulp, N-methylmorpholine-N-oxide solvent and cellulose nanocrystals, comprising: mixing cellulose pulp and N-methylmorpholine-N-oxide solvent and then subjecting the mixture to ultrasonic treatment to obtain a first liquid, and adding cellulose nanocrystals to the first liquid for dispersion treatment to obtain the spinning solution.

[0050] In this embodiment, cellulose pulp and N-methylmorpholine-N-oxide solvent are first mixed, followed by ultrasonic treatment. The cavitation effect and mechanical vibration of ultrasound effectively break down the aggregated structure of the cellulose pulp, promoting its uniform dispersion and full swelling in the solvent, shortening the dissolution time, and improving the dissolution efficiency, thus obtaining a first liquid with uniform composition. Next, cellulose nanocrystals are added to this first liquid for dispersion treatment. This dispersion treatment can be achieved through high-speed stirring, mechanical shearing, or further ultrasonic dispersion, ensuring that the cellulose nanocrystals are uniformly and stably dispersed in the first liquid, reducing their agglomeration. This improves the mechanical properties of the final product.

[0051] In some embodiments, the power of the ultrasonic treatment is 700W-1000W.

[0052] In this embodiment, by limiting the power of ultrasonic treatment to this range, it is possible to ensure the effective breaking of the aggregated structure of cellulose pulp while reducing the excessive degradation of cellulose molecular chains or the thermal decomposition of N-methylmorpholine-N-oxide solvent due to excessive power, thereby ensuring the integrity of cellulose molecules in the first liquid and the stability of the solvent system.

[0053] In some embodiments, the ultrasonic treatment time is 10 min to 60 min.

[0054] In this embodiment, by controlling the ultrasonic treatment time within this range, the cellulose pulp can be fully dispersed and swollen in the solvent, ensuring that it can be uniformly dissolved to form a stable first liquid, while reducing the energy consumption and possible damage to the cellulose molecular chains caused by excessively long treatment time, thus achieving a balance between efficiency and effectiveness.

[0055] In some embodiments, the dispersion treatment temperature is 5°C-55°C.

[0056] In this embodiment, by controlling the temperature of the dispersion process within this range, cellulose nanocrystals can be uniformly dispersed in the first liquid.

[0057] In some embodiments, the dispersion processing time is 1-3 hours.

[0058] In this embodiment, by controlling the dispersion time within this range, it is possible to ensure that the cellulose nanocrystals are fully and stably dispersed in the first liquid, reducing local agglomeration caused by too short a dispersion time, and also reducing the increase in energy consumption and possible structural changes of the cellulose nanocrystals caused by too long a dispersion time, thereby ensuring both dispersion effect and process efficiency.

[0059] In some embodiments, the dispersion process includes stirring.

[0060] In this embodiment, by using a stirring method for dispersion, the cellulose nanocrystals can be uniformly distributed in the first liquid with the help of mechanical force.

[0061] In some embodiments, the spinning solution is solidified in a coagulation bath to obtain cellulose nanocrystal colored lyocell fibers, comprising: The spinning solution is spun to obtain the precursor. The precursor is solidified in a coagulation bath to obtain the intermediate; After washing and drying the intermediate, cellulose nanocrystal colored Lyocell fiber is obtained.

[0062] In this embodiment, the spinning solution is first extruded through a spinning process (such as wet spinning) to form a precursor with a preliminary morphology. During this process, under the shearing force and traction of the spinneret, the cellulose molecular chains and cellulose nanocrystals begin to undergo preliminary orientation and alignment.

[0063] It can be understood that during the spinning process, the shear force is changed by selecting different spinning needle aperture sizes to control the formation of cellulose nanocrystals, and the coagulation bath concentration is changed to control the rate of coagulation of cellulose nanocrystals in the fiber. The pitch of the cellulose nanocrystals is controlled, thereby changing the fiber to present different colors and obtaining cellulose nanocrystal colored Lyocell fibers.

[0064] In some embodiments, the aperture of the spinning needle in the spinning process is 0.18 mm to 0.84 mm.

[0065] In this embodiment, by limiting the aperture of the spinning needle within this range, a suitable shear force environment can be provided according to the required linear density and structural color of the fiber. At the same time, a suitable aperture range also ensures the smooth progress of the spinning process, reducing the risk of excessive flow resistance in the spinning solution and easy clogging of the needle due to excessively small apertures.

[0066] Specifically, in one embodiment, the spinning process can be as follows: under air pump pressure, the spinning solution is extruded into filaments through a spinneret and stretched vertically in air, then solidified in a coagulation bath, and finally wound onto a take-up drum under the action of a traction device to obtain cellulose nanocrystalline color-developed lyocell fibers. The spinning air pressure is 3MPa-10MPa, the circulating water temperature of the spinning nozzle is 95℃-115℃, the spinning speed is 10m / min-50m / min, and the drawing speed is 15m / min-60m / min. By controlling parameters such as the spinning air pressure, the nozzle circulating water temperature, the spinning speed, and the drawing speed, the flow state of the spinning solution at the spinneret outlet, the solidification rate, and the stretching ratio during fiber formation can be effectively adjusted, thereby optimizing the fiber diameter uniformity, orientation, and mechanical properties.

[0067] Specifically, in one embodiment, washing can be performed with deionized water for 15-30 minutes. This effectively removes residues without causing excessive swelling of the fiber structure or disruption of the orderly arrangement of cellulose nanocrystals due to prolonged washing time.

[0068] Secondly, this invention proposes a cellulose nanocrystalline color-developing lyocell fiber, prepared by the aforementioned method for preparing cellulose nanocrystalline color-developing lyocell fibers. This cellulose nanocrystalline color-developing lyocell fiber possesses all the beneficial effects of the preparation method for cellulose nanocrystalline color-developing lyocell fibers, which will not be elaborated upon here.

[0069] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0070] I. Preparation Method Example 1 Cellulose pulp and propyl gallate were added to N-methylmorpholine-N-oxide solvent, ultrasonicated at 800W for 30 min, then cellulose nanocrystals were added, and the mixture was stirred at 40℃ for 2 h to obtain spinning solution.

[0071] In the spinning solution, the mass of cellulose nanocrystals, cellulose pulp, and propyl gallate is 0.4%, 4.5%, and 0.03% of the mass of N-methylmorpholine-N-oxide solvent, respectively; and the mass fraction of N-methylmorpholine-N-oxide in the N-methylmorpholine-N-oxide solvent is 50%.

[0072] The spinning solution was subjected to air pressure spinning to obtain the precursor. The circulating water temperature in the spinning tank was 98℃, the spinning air pressure was 6MPa, the spinning speed was 20m / min, the orifice diameter of the spinning needle was 0.24mm, and the drawing speed was 20m / min.

[0073] The precursor is passed through a first ammonium sulfate coagulation bath at 45°C and 35wt% and a second ammonium sulfate coagulation bath at 40°C and 40wt% respectively, and then wound onto a take-up drum under the action of a traction device to obtain an intermediate.

[0074] The intermediate was washed with deionized water for 20 minutes and dried in an oven at 55°C to obtain the cellulose nanocrystal color-developed Lyocell fiber of Example 1.

[0075] Example 2 Compared with Example 1, the difference is that the mass of cellulose nanocrystals in the spinning solution is 0.5% of the mass of N-methylmorpholine-N-oxide solvent. The other steps are roughly the same as in Example 1, and will not be repeated here. The cellulose nanocrystal colored Lyocell fiber of Example 2 is obtained.

[0076] Example 3 The difference from Example 1 is that the mass of cellulose nanocrystals in the spinning solution is 0.3% of the mass of N-methylmorpholine-N-oxide solvent. The other steps are roughly the same as in Example 1 and will not be repeated here.

[0077] Example 4 Compared with Example 1, the difference is that the mass of cellulose nanocrystals in the spinning solution is 0.6% of the mass of N-methylmorpholine-N-oxide solvent. The other steps are roughly the same as in Example 1 and will not be repeated here.

[0078] Example 5 Compared with Example 1, the difference is that the orifice diameter of the spinning needle is 0.4 mm. The other steps are roughly the same as in Example 1, and will not be repeated here.

[0079] Example 6 Compared with Example 1, the difference is that the orifice diameter of the spinning needle is 0.18 mm. The other steps are roughly the same as in Example 1, and will not be repeated here.

[0080] Example 7 Compared with Example 1, the difference is that the orifice diameter of the spinning needle is 0.84 mm. The other steps are roughly the same as in Example 1, and will not be repeated here.

[0081] Comparative Example 1 The difference from Example 1 is that the mass of cellulose nanocrystals in the spinning solution is 0. The other steps are roughly the same as in Example 1 and will not be repeated here.

[0082] Comparative Example 2 Compared with Example 1, the difference is that the ammonium sulfate coagulation bath is replaced with a 50% NMMO coagulation bath. The other steps are roughly the same as in Example 1, and will not be repeated here.

[0083] Comparative Example 3 Compared with Example 1, the difference is that the ammonium sulfate coagulation bath is replaced with a 30% ethanol solution coagulation bath. The other steps are roughly the same as in Example 1, and will not be repeated here.

[0084] II. Testing Methods The mechanical properties of the fibers were tested using an XQ-1AN electronic single-fiber strength tester (Shanghai Xinxian Instrument Co., Ltd.). Under constant temperature and humidity conditions, the fiber clamp distance was set to 10 mm, and the moving speed was 20 mm / min. Each sample underwent 30 parallel experiments, and the average value of the data was taken as the final test result.

[0085] The microstructure of the fiber surface was tested using a field emission scanning electron microscope (JEOL-7800F) (Nippon Electron Ltd.). The colored lyocell fibers were first dried and separated, then cut to appropriate lengths and attached to conductive adhesive. Subsequently, gold sputtering was performed to enhance surface conductivity. Finally, the fiber surface was randomly scanned using a scanning electron microscope.

[0086] The distribution of cellulose nanocrystals in the fiber cross-section was tested using a super depth-of-field microscope (DSX1000) (Ingenie). The test conditions were room temperature and polarized light mode.

[0087] III. Analysis of Test Results for Each Embodiment and Comparative Example from Figures 1 to 7 As can be seen, the Lyocell fibers obtained in Examples 1-7 show obvious color changes compared to Comparative Example 1, indicating that adding cellulose nanocrystals can prepare colored Lyocell fibers.

[0088] from Figure 1 , Figures 5 to 7 As can be seen, the Lyocell fibers obtained in Examples 1, 5 to 7 have obvious color changes compared to Comparative Example 1, indicating that different colored Lyocell fibers can be prepared by changing the aperture size of the spinning needle.

[0089] from Figure 1 , Figures 9 to 10It can be seen that, compared with Comparative Examples 2 and 3, the Lyocell fibers obtained in Example 1 have obvious color change, indicating that ammonium sulfate coagulation bath can prepare brightly colored Lyocell fibers, while under NMMO coagulation bath and ethanol solution coagulation bath conditions, the color development effect of the fibers is weak or even non-color development.

[0090] from Figure 11 It can be seen that the addition of cellulose nanocrystals results in a smooth microscopic surface of the prepared fiber, indicating that the addition of cellulose nanocrystals does not affect the microscopic surface structure of the fiber.

[0091] from Figure 12 It can be seen that the cross-section of cellulose exhibits obvious birefringence under a polarizing microscope, indicating that cellulose nanocrystals are dispersed inside the fiber.

[0092] Table 1 Mechanical properties of Lyocell fibers prepared in Examples 1-7 and Comparative Examples 1-3 As can be seen from Table 1, compared with Comparative Examples 1-3, the fibers of Examples 1-7 have higher breaking strength and breaking elongation, indicating that the addition of cellulose nanocrystals enhances the breaking strength and breaking elongation of the fibers.

[0093] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A method for preparing cellulose nanocrystal color-developing Lyocell fibers, characterized in that, include: A spinning solution is provided, the spinning solution comprising cellulose pulp, N-methylmorpholine-N-oxide solvent and cellulose nanocrystals; The spinning solution is subjected to spinning treatment to obtain a precursor; The precursor is solidified in a coagulation bath to obtain an intermediate; The intermediate is washed and dried to obtain the cellulose nanocrystal color-developed Lyocell fiber; wherein the coagulation bath includes an ammonium sulfate solution; In the spinning solution, the mass of the cellulose pulp is 4%-5% of the mass of the N-methylmorpholine-N-oxide solvent, the mass of the cellulose nanocrystals is 0.3%-0.6% of the mass of the N-methylmorpholine-N-oxide solvent, and the mass fraction of the N-methylmorpholine-N-oxide in the N-methylmorpholine-N-oxide solvent is 40%-60%. In the ammonium sulfate solution, the mass fraction of ammonium sulfate is 5%-50%, and the temperature of the coagulation bath is 15℃-65℃; The aperture of the spinning needle in the spinning process is 0.18mm-0.84mm; The spinning solution also includes a stabilizer; In the spinning solution, the stabilizer accounts for 0.01%-0.04% of the mass of the N-methylmorpholine-N-oxide solvent; The stabilizer includes at least one of calcium-zinc stabilizer, vitamin E, tea polyphenols, rosemary extract, and propyl gallate; The coagulation bath has multiple stages.

2. The method for preparing cellulose nanocrystalline color-developing Lyocell fibers according to claim 1, characterized in that, The provided spinning solution comprises cellulose pulp, N-methylmorpholine-N-oxide solvent, and cellulose nanocrystals, including: The cellulose pulp and the N-methylmorpholine-N-oxide solvent are mixed and ultrasonically treated to obtain a first liquid. The cellulose nanocrystals are then added to the first liquid for dispersion treatment to obtain the spinning solution.

3. The method for preparing cellulose nanocrystalline color-developing Lyocell fibers according to claim 2, characterized in that, The power of the ultrasonic treatment is 700W-1000W; and / or, The ultrasonic treatment time is 10 min-60 min; and / or, The dispersion treatment temperature is 5℃-55℃; and / or, The dispersion treatment time is 1 hour to 3 hours; and / or, The dispersion process includes stirring.

4. A cellulose nanocrystal color-developing lyocell fiber, characterized in that, It is prepared by the method for preparing cellulose nanocrystal color-developing lyocell fibers according to any one of claims 1 to 3.

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