An ultra-soft fiber and its preparation method

Abstract

This invention discloses an ultra-soft fiber and its preparation method, relating to the field of textiles. The fiber comprises, from the inside out: a supporting core layer comprising ultra-fine denier synthetic fibers with a porous structure, wherein the single filament fineness of the ultra-fine denier synthetic fibers is less than 0.8 dtex; a functional intermediate layer wrapped around the supporting core layer, comprising regenerated cellulose fibers; and a tactile surface layer wrapped around the functional intermediate layer, comprising natural plant fibers treated with bio-enzyme polishing. The supporting core layer, the functional intermediate layer, and the tactile surface layer are integrally formed using composite spinning technology to create the ultra-soft fiber. The ultra-soft fiber has a bending stiffness of less than 0.5 cN / dtex and a compression resilience higher than 85%. This invention has the advantages of uniform structure and high softness.

Description

Technical Field

[0001] This invention relates to the field of textiles, and more specifically to an ultra-soft fiber and its preparation method. Background Technology

[0002] Softness is one of the key indicators for measuring the comfort of textiles. In existing technologies, two main methods are generally used to obtain soft textiles: one is to select natural fibers that are inherently soft, such as cotton and cashmere; the other is to physically blend multiple fibers and add softeners.

[0003] However, the softness of fibers or fabrics obtained through these existing technologies is still significantly insufficient, failing to meet the market's pursuit of an extremely soft touch. In particular, methods that physically mix different types of fibers are difficult to disperse evenly at the microscale, resulting in unstable and uneven softness in the final product, and making it difficult to achieve higher softness indicators.

[0004] Therefore, how to provide a stable, uniform, and ultra-soft fiber is a problem that needs to be solved in this field. Summary of the Invention

[0005] This invention aims to address, to a certain extent, one of the technical problems in related technologies. To this end, this invention provides an ultra-soft fiber and its preparation method, which has the advantages of uniform structure and high softness.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: An ultra-soft fiber comprising, from the inside out: The supporting core layer comprises ultrafine denier synthetic fibers with a porous structure, wherein the single filament fineness of the ultrafine denier synthetic fibers is less than 0.8 dtex; A functional intermediate layer, which is wrapped around the support core layer, the functional intermediate layer comprising regenerated cellulose fibers; A tactile surface layer, which is wrapped around the functional intermediate layer, comprises natural plant fibers that have been treated with bio-enzymes; The supporting core layer, the functional intermediate layer, and the tactile surface layer are integrally formed by composite spinning technology to form the ultra-soft fiber; the bending stiffness of the ultra-soft fiber is less than 0.5 cN / dtex and the compression resilience is higher than 85%.

[0007] In this application, a composite spinning technology is used to integrally mold the three-layer material, preventing the uneven component distribution caused by physically mixing different types of fibers, and ensuring the uniformity and stability of the structure and properties of the resulting ultra-soft fiber. Furthermore, through the synergistic effect of the porous ultra-fine denier synthetic fiber supporting the core layer, the moisture-absorbing and wicking function of the intermediate layer, and the bio-enzyme polishing of the tactile surface layer, the ultra-soft fiber achieves low bending stiffness and high compression resilience, realizing a combination of ultra-softness and high resilience.

[0008] Optionally, the supporting core layer further includes a phase change temperature regulating material; the phase change temperature regulating material is paraffin microcapsules with a particle size of 0.5~5μm, and the amount of paraffin microcapsules added is 0.5%~3% of the total mass of the ultra-soft fibers.

[0009] Optionally, the functional intermediate layer further includes elastic aerogel particles, wherein the amount of aerogel particles added is 0.1% to 2% of the total mass of the ultra-soft fibers.

[0010] Optionally, the fineness of the single filament of the ultrafine denier synthetic fiber is 0.3~0.8 dtex, and the porosity of the ultrafine denier synthetic fiber is 30%~60%.

[0011] Optionally, the regenerated cellulose fiber is lyocell fiber or modal fiber, with a degree of polymerization of 350 to 550.

[0012] Furthermore, the present invention also provides a method for preparing ultra-soft fibers, wherein the ultra-soft fibers include the aforementioned ultra-soft fibers, comprising the following steps: The spinning raw materials that form the supporting core layer, the functional intermediate layer and the tactile surface layer are simultaneously extruded through a composite spinning assembly to form nascent fibers with a three-layer composite structure. The nascent fibers are subjected to bio-enzymatic polishing treatment; The fibers that have undergone bio-enzyme polishing are subjected to supercritical carbon dioxide fluid expansion treatment. Ultra-soft fibers were obtained by subjecting the expanded fibers to low-temperature plasma surface modification treatment.

[0013] Optionally, the bio-enzyme polishing treatment includes: immersing the nascent fibers in a buffer solution containing cellulase and / or protease for treatment at a temperature of 40°C to 60°C for a time of 30 to 90 minutes.

[0014] Optionally, the conditions for the supercritical carbon dioxide fluid expansion treatment include: placing the fiber in a treatment container and introducing carbon dioxide gas, heating and pressurizing the carbon dioxide to reach a supercritical state, maintaining the conditions at a pressure of 8~25MPa and a temperature of 35~60℃ for 1~3 hours, and then depressurizing at a rate of 0.5~2MPa / s.

[0015] Optionally, the low-temperature plasma surface modification treatment includes a first stage and a second stage; the first stage includes: surface activation and etching of the fiber under a nitrogen atmosphere, wherein the flow rate of nitrogen is controlled at 10~30 L / min, the power of the plasma generator is controlled at 100~180W, and the treatment time is 2~5 minutes; the second stage includes: switching the reaction atmosphere to a mixture of nitrogen and oxygen, wherein the volume fraction of oxygen in the mixture is 20%~40%, the power of the plasma generator is increased to 200~300W, and the treatment time is 5~12 minutes.

[0016] Optionally, the spinning raw material forming the supporting core layer is a melt of polyethylene terephthalate or polyamide; the spinning raw material forming the functional intermediate layer is a regenerated cellulose fiber solution; and the spinning raw material forming the tactile surface layer is an aqueous spinning solution of bamboo pulp or alginate.

[0017] These features and advantages of the present invention will be disclosed in detail in the following specific embodiments and accompanying drawings. The preferred embodiments or means of the present invention will be shown in detail in conjunction with the accompanying drawings, but are not intended to limit the technical solutions of the present invention. In addition, each of these features, elements and components appearing in the following text and drawings is a plurality of, and different symbols or numbers are used for convenience of representation, but all represent parts with the same or similar construction or function. Attached Figure Description

[0018] The present invention will be further described below with reference to the accompanying drawings: Figure 1 This is a cross-sectional view of the ultra-soft fiber in this invention.

[0019] The structure consists of: 1. Supporting core layer; 2. Functional intermediate layer; 3. Tactile surface layer. Detailed Implementation

[0020] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described are intended to explain the present invention and should not be construed as limiting the invention.

[0021] The terms "an embodiment," "example," or "trademark" used in this specification refer to a particular feature, structure, or characteristic described in connection with the embodiment itself that may be included in at least one embodiment disclosed in this patent. The phrase "in an embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment.

[0022] Example: This embodiment provides an ultra-soft fiber, such as Figure 1 As shown, the structure comprises, from the inside out: a supporting core layer 1, which includes ultra-fine denier synthetic fibers with a porous structure, the single filament fineness of which is less than 0.8 dtex; a functional intermediate layer 2, which wraps around the supporting core layer 1, and includes regenerated cellulose fibers; and a tactile surface layer 3, which wraps around the functional intermediate layer 2, and includes natural plant fibers that have undergone bio-enzyme polishing treatment. The supporting core layer 1, functional intermediate layer 2, and tactile surface layer 3 are integrally formed using composite spinning technology to create an ultra-soft fiber. The ultra-soft fiber has a bending stiffness of less than 0.5 cN / dtex and a compression resilience higher than 85%.

[0023] In this embodiment, three materials with different functions are integrally formed through composite spinning. Composite spinning is a material processing technology that uses multi-component polymer melts to converge within a spinneret to form composite fibers. Before spinning, each component raw material is processed into a homogeneous melt or solution. These fluids are distributed in a preset geometry (such as concentric circles) by a precise spinning assembly and converged and extruded at the nozzle. Mixing occurs between liquid molecular flows, and its uniformity is controlled by the mold, achieving structural forming. The relative positions of the three layers of ultra-soft fiber, the thickness of each layer, and the overall structure are entirely determined by the design of the composite spinning assembly (such as the distribution plate and the geometry of the spinneret) and the flow rate of each spinning fluid. Therefore, as long as the parameters of the composite spinning equipment are stable, each ultra-soft fiber produced will have a preset composite structure, preventing the problem of uneven component distribution caused by the physical mixing of different types of fibers. The ultra-fine denier synthetic fiber supporting the core layer 1 has a porous structure, thereby providing low bending stiffness for the ultra-soft fiber while ensuring structural support. The regenerated cellulose fibers in the functional intermediate layer 2 provide moisture absorption and wicking functions. With a moisture absorption capacity of 13%–15%, which is 6%–7% higher than cotton fibers, the regenerated cellulose fibers offer excellent breathability and moisture regulation, thus keeping the skin in contact with the ultra-soft fibers dry and helping to maintain their soft touch. The bio-enzyme polishing treatment of the tactile surface layer 3 creates a smooth and supple surface feel for the ultra-soft fibers. The synergistic effect of these three components, combined with the stable interface formed by composite spinning technology, enables the ultra-soft fibers to simultaneously achieve extremely low flexural stiffness (less than 0.5 cN / dtex) and extremely high compression resilience (greater than 85%), resulting in an ultra-soft yet fluffy and non-collapsed effect. This overcomes the problems of unstable performance and lack of durability associated with mixing multiple fiber raw materials in existing technologies.

[0024] The supporting core layer 1 also includes a phase change temperature regulating material; the phase change temperature regulating material is paraffin microcapsules with a particle size of 0.5~5μm, and the amount of paraffin microcapsules added is 0.5%~3% of the total mass of the ultra-soft fibers.

[0025] In this embodiment, before composite spinning, a phase change temperature-regulating material is uniformly mixed into the spinning melt of the support core layer 1 under high-speed shearing conditions at 260-280°C. The phase change temperature-regulating material is paraffin microcapsules with a particle size of 0.5-5 μm. Introducing paraffin microcapsules into the support core layer 1 gives the ultra-soft fiber a temperature-regulating function. It should be noted that in this embodiment, paraffin microcapsules are added instead of bare paraffin. Each microcapsule has a robust polymer shell (commonly such as melamine resin, polyurea, etc.), and the shell encapsulates a paraffin core material. When the ambient or body surface temperature rises, the paraffin inside the microcapsule absorbs heat and melts, producing a cooling sensation; when the temperature drops, the paraffin solidifies and releases heat, providing a warming sensation. The particle size range of 0.5-5 μm ensures its uniform dispersion in the spinning melt, ensuring a significant temperature-regulating effect while avoiding the impact of excessively large particle size on the fiber's main mechanical properties (such as strength and softness), thus giving the ultra-soft fiber high comfort.

[0026] The functional intermediate layer 2 also includes elastic aerogel particles, with the amount of aerogel particles added being 0.1% to 2% of the total mass of the ultra-soft fibers.

[0027] In this embodiment, a low amount of elastic aerogel particles are introduced into the functional intermediate layer 2 to enhance the thermal insulation performance and elastic recovery of the ultra-soft fiber. Aerogel has high porosity and low thermal conductivity; its nanoporous structure effectively blocks heat transfer. Dispersing it in the hygroscopic functional intermediate layer 2 further improves the warmth retention or insulation effect. Simultaneously, the elasticity of the aerogel particles themselves helps improve the overall compression resilience of the ultra-soft fiber. The low addition amount minimizes the impact on the spinnability of the ultra-soft fiber.

[0028] The single filament fineness of ultrafine denier synthetic fibers is 0.3~0.8 dtex, and the porosity of ultrafine denier synthetic fibers is 30%~60%.

[0029] In this embodiment, the fineness (0.3~0.8 dtex) and porosity (30%~60%) of the ultrafine denier synthetic fibers in the supporting core layer 1 are key structural parameters for achieving the mechanical properties (flexural stiffness <0.5 cN / dtex, compression resilience >85%) of the ultra-soft fiber in claim 1. The relatively small fineness of the ultrafine denier synthetic fibers reduces the stiffness and mass of individual fibers. Furthermore, the high porosity of the ultrafine denier synthetic fibers creates numerous tiny elastic cavities within the fiber. These cavities can deform and store energy under pressure, and recover after pressure release, providing high compression resilience. Simultaneously, the pore structure significantly reduces the density of the ultrafine denier synthetic fibers, further reducing the flexural stiffness of the resulting ultra-soft fiber. A porosity less than 30% results in insufficient resilience and lightweight of the ultra-soft fiber, while a porosity exceeding 60% may reduce the structural strength and spinnability of the ultra-soft fiber.

[0030] The regenerated cellulose fiber is lyocell or modal fiber with a degree of polymerization of 350 to 550.

[0031] In this embodiment, the regenerated cellulose fiber is lyocell or modal fiber to optimize its moisture absorption and wicking properties and mechanical properties. Regenerated cellulose fiber itself has good hydrophilicity and moisture absorption. When its degree of polymerization is less than 350, the strength of the ultra-soft fiber may be insufficient, affecting the durability of the textiles made from it; when the degree of polymerization is greater than 550, the fiber will be too stiff, which is not conducive to the overall softness.

[0032] Furthermore, the present invention also provides a method for preparing ultra-soft fibers, the ultra-soft fibers including the aforementioned ultra-soft fibers, comprising the following steps: The spinning raw materials that form the supporting core layer 1, the functional intermediate layer 2 and the tactile surface layer 3 are simultaneously extruded through a composite spinning assembly to form nascent fibers with a three-layer composite structure. The nascent fibers are subjected to bio-enzyme polishing treatment; The fibers that have undergone bio-enzyme polishing are subjected to supercritical carbon dioxide fluid expansion treatment. Ultra-soft fibers were obtained by subjecting the expanded fibers to low-temperature plasma surface modification treatment.

[0033] In this embodiment, composite spinning technology is the preferred method for constructing a three-layer structure of ultra-soft fibers. The bio-enzyme is specifically cellulase. The bio-enzyme polishing treatment acts on the tactile surface layer 3, catalyzing the hydrolysis of the chemical bonds of the natural plant fibers in the tactile surface layer 3 by the cellulase, thereby removing microfibers from the surface of the tactile surface layer 3 and improving the smoothness, feel, and anti-pilling properties of the fabric made from this ultra-soft fiber. Supercritical carbon dioxide fluid expansion treatment helps achieve high porosity in the supporting core layer 1. Supercritical carbon dioxide can penetrate into the amorphous region of the synthetic fiber, and its vaporization expansion force during instantaneous pressure release opens up the polymer chains from the inside, forming uniform nanoscale pores. Low-temperature plasma treatment modifies the overall surface of the synthetic fiber, increasing the surface energy of the fiber to enhance the hydrophilicity of the ultra-soft fiber.

[0034] The bio-enzyme polishing treatment includes immersing the nascent fibers in a buffer solution containing cellulase and / or protease for treatment at a temperature of 40℃~60℃ for 30~90 minutes.

[0035] In this embodiment, cellulase and / or protease are used to target natural plant fibers. A treatment temperature of 40°C to 60°C ensures optimal enzyme activity and reaction efficiency. A treatment time of 30 to 90 minutes is sufficient for the enzyme molecules to fully act to achieve the desired polishing effect (such as a significant reduction in surface roughness Ra) without excessively damaging the bulk strength of the ultra-soft fibers. A buffer solution maintains the stable pH environment required for the enzyme reaction, ensuring the effectiveness of the polishing treatment and contributing to the stable and excellent tactile feel of the ultra-soft fibers.

[0036] The conditions for supercritical carbon dioxide fluid expansion treatment include: placing the fiber in a treatment container and introducing carbon dioxide gas, heating and pressurizing the carbon dioxide to reach a supercritical state, maintaining the conditions at a pressure of 8~25MPa and a temperature of 35~60℃ for 1~3 hours, and then depressurizing at a rate of 0.5~2MPa / s.

[0037] In this embodiment, the pressure is 8–25 MPa and the temperature is 35–60°C. These parameters ensure that carbon dioxide fully penetrates into the fiber and swells the amorphous regions. The pressure holding time is 1–3 hours to ensure that penetration and swelling reach equilibrium. The depressurization rate is 0.5–2 MPa / s. A higher depressurization rate causes the carbon dioxide dissolved in the fiber to rapidly vaporize and expand, thereby forming more pores in the ultra-soft fiber. If the depressurization rate is too slow (less than 0.5 MPa / s), the carbon dioxide will escape slowly, making it difficult to form significant pores; if the rate is too fast, it may cause damage to the fiber structure.

[0038] The low-temperature plasma surface modification treatment includes a first stage and a second stage. The first stage includes surface activation and etching of the fiber under a nitrogen atmosphere, wherein the nitrogen flow rate is controlled at 10~30 L / min, the power of the plasma generator is controlled at 100~180W, and the treatment time is 2~5 minutes. The second stage includes switching the reaction atmosphere to a mixture of nitrogen and oxygen, wherein the oxygen volume fraction in the mixture is 20%~40%, the power of the plasma generator is increased to 200~300W, and the treatment time is 5~12 minutes.

[0039] In this embodiment, a two-stage plasma treatment was used to regulate the surface modification of the ultra-soft fiber. The first stage was in a nitrogen atmosphere. Under high-energy particle bombardment, the micro-roughness of the composite fiber surface increased, and a large number of free radical active sites were generated, preparing for the second-stage reaction. The second stage was in a nitrogen-oxygen mixed atmosphere. After introducing oxygen, the active oxygen species in the plasma (such as O atoms and ozone) reacted with the active sites generated in the first stage, introducing oxygen-containing polar functional groups such as hydroxyl and carboxyl groups onto the fiber surface. This achieved hydrophilic modification of the ultra-soft fiber surface, thereby significantly improving the fiber's moisture absorption and wicking properties.

[0040] The spinning raw material forming the supporting core layer 1 is a melt of polyethylene terephthalate or polyamide; the spinning raw material forming the functional intermediate layer 2 is a regenerated cellulose fiber solution; and the spinning raw material forming the tactile surface layer 3 is an aqueous spinning solution of bamboo pulp or alginate.

[0041] In this embodiment, the supporting core layer 1 is made of polyester or polyamide melt, both of which have good melt spinnability and high strength, and are easily formed into a porous structure through supercritical carbon dioxide fluid expansion treatment. The functional intermediate layer 2 uses a regenerated cellulose fiber solution to ensure its excellent moisture absorption. The tactile surface layer 3 uses an aqueous spinning solution of bamboo pulp or alginate. Both bamboo pulp and alginate are natural polymer materials, making the resulting ultra-soft fiber more skin-friendly and environmentally friendly. Furthermore, their aqueous solutions are easily spun into fibers by wet spinning, facilitating subsequent bio-enzyme treatment.

[0042] Preparation Example 1: This preparation example provides a method for preparing ultra-soft fibers. Polyethylene terephthalate (PET) chips are dried and melted to serve as the spinning raw material for the supporting core layer 1. Cellulose is dissolved in N-methylmorpholine-N-oxide solvent to prepare a lyocell spinning solution as the raw material for the functional intermediate layer 2. Bamboo pulp is dissolved in a specific solvent to prepare a spinning solution as the raw material for the tactile surface layer 3. The three spinning materials are metered separately and simultaneously extruded through a three-channel composite spinning assembly at temperatures of 290°C for the core layer, 95°C for the intermediate layer, and 88°C for the surface layer. After cooling, oiling, and winding, nascent composite fibers are obtained, with a core layer monofilament fineness of approximately 0.5 dtex. The fibers are then processed as follows: (1) Bio-enzyme polishing treatment: The nascent fibers were immersed in an acetate-sodium acetate buffer solution with a pH of 5.0 and containing cellulase with an activity unit of 1500 U / g. The solution was then treated for 60 minutes in a water bath at 50°C with the assistance of ultrasound at a frequency of 28kHz. After treatment, the fibers were thoroughly washed with water, neutralized, and dried.

[0043] (2) Supercritical carbon dioxide puffing treatment: The enzyme-treated fiber is placed in a supercritical treatment vessel, carbon dioxide is introduced, the temperature is raised to 50°C, the pressure is increased to 15 MPa and maintained for 2 hours, and then the pressure is rapidly released at a rate of 1.0 MPa / s.

[0044] (3) Low-temperature plasma surface modification treatment: The expanded fiber was placed in a low-temperature plasma device. First stage: Nitrogen gas was introduced at a flow rate of 20 L / min and treated for 4 minutes at a power of 150 W. Second stage: The gas was switched to a mixture of nitrogen and oxygen in a volume ratio of 7:3, with a total flow rate of 25 L / min. The power was increased to 250 W and the treatment continued for 8 minutes.

[0045] After processing, the ultra-soft fiber of this invention is obtained. Testing shows that the fiber core porosity is approximately 45%, the bending stiffness is approximately 0.36 cN / dtex, and the compression resilience is greater than 88%.

[0046] Preparation Example 2: This preparation example provides a method for preparing an ultra-soft fiber containing a phase change temperature-regulating material. The difference between this method and Preparation Example 1 is that, during the raw material preparation stage of the supporting core layer 1, when drying and melting polyethylene terephthalate (PET) chips, paraffin microcapsules with a particle size of approximately 2 μm are uniformly mixed into the melt. The amount of these microcapsules added is 1.5% of the total fiber mass. Apart from this difference, the remaining raw materials, process steps, and parameters are completely identical to Preparation Example 1. After processing, an ultra-soft fiber containing a phase change temperature-regulating material is obtained. Testing showed that the fiber's bending stiffness is approximately 0.38 cN / dtex, its compression resilience is approximately 87%, and differential scanning calorimetry (DSC) testing revealed a significant phase change peak with a phase change enthalpy of approximately 8 J / g. In tests simulating environmental temperature changes, the fiber exhibited a buffering capacity for endothermic or exothermic temperatures.

[0047] Preparation Example 3: This preparation example provides a method for preparing an ultra-soft fiber containing aerogel particles. The difference between this method and Preparation Example 1 is that, during the preparation stage of the functional intermediate layer 2 raw material, silica aerogel particles with a particle size of 50-100 nm are uniformly dispersed into the lyocell spinning solution. The amount of aerogel particles added is 0.8% (wt%) of the total fiber mass. Apart from this difference, the other raw materials, process steps, and parameters are completely identical to those in Preparation Example 1. After processing, an ultra-soft fiber containing aerogel particles is obtained. Testing shows that the compression resilience of this fiber is increased to approximately 90%, and its thermal conductivity is significantly lower than that of the control sample without added aerogel, exhibiting superior thermal insulation performance.

[0048] Comparative example: A comparative fiber was prepared using a physical mixing method based on existing technology. Three short fibers with similar functional design intent to those in Preparation Example 1 were prepared: polyethylene terephthalate short fibers (mimicking the function of the supporting core layer 1), lyocell short fibers (mimicking the functional intermediate layer 2), and bamboo pulp short fibers (mimicking the tactile surface layer 3) with similar fineness. The three short fibers were physically mixed in proportions similar to the volume ratio of each layer in the fiber of Preparation Example 1. Subsequently, the mixed fiber bundles were processed into blended yarn through conventional opening, carding, drawing, and spinning processes. Testing showed that the bending stiffness of this blended yarn was approximately 1.2 cN / dtex, and the compression recovery rate was approximately 75%. Compared with the fiber obtained in Example 1, its softness (higher bending stiffness) and resilience (lower compression recovery rate) showed significant differences. Furthermore, the yarn exhibited large fluctuations in evenness testing, and the performance repeatability of different batches of samples was poor, indicating that traditional physical mixing methods have inherent defects such as uneven component distribution and unstable performance.

[0049] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that the present invention includes, but is not limited to, the contents described in the accompanying drawings and the specific embodiments above. Any modifications that do not depart from the functional and structural principles of the present invention will be included within the scope of the claims.

Claims

1. An ultra-soft fiber, characterized in that, Including those set from the inside out: The supporting core layer comprises ultrafine denier synthetic fibers with a porous structure, wherein the single filament fineness of the ultrafine denier synthetic fibers is less than 0.8 dtex; A functional intermediate layer, which is wrapped around the support core layer, the functional intermediate layer comprising regenerated cellulose fibers; A tactile surface layer, which is wrapped around the functional intermediate layer, comprises natural plant fibers that have been treated with bio-enzymes; The supporting core layer, the functional intermediate layer, and the tactile surface layer are integrally formed by composite spinning technology to form the ultra-soft fiber; the bending stiffness of the ultra-soft fiber is less than 0.5 cN / dtex and the compression resilience is higher than 85%.

2. The super-soft fiber according to claim 1, wherein, The supporting core layer also includes a phase change temperature regulating material; the phase change temperature regulating material is paraffin microcapsules with a particle size of 0.5~5μm, and the amount of paraffin microcapsules added is 0.5%~3% of the total mass of the ultra-soft fibers.

3. The super-soft fiber according to claim 1, wherein, The functional intermediate layer also includes elastic aerogel particles, the amount of which is 0.1% to 2% of the total mass of the ultra-soft fibers.

4. The super-soft fiber according to claim 1, wherein, The microfilament fineness of the ultrafine denier synthetic fiber is 0.3~0.8 dtex, and the porosity of the ultrafine denier synthetic fiber is 30%~60%.

5. The super-soft fiber according to claim 1, wherein The regenerated cellulose fiber is lyocell fiber or modal fiber, with a degree of polymerization of 350~550.

6. A method for preparing an ultra-soft fiber, characterized in that, The ultra-soft fiber includes the ultra-soft fiber according to any one of claims 1 to 5, comprising the following steps: The spinning raw materials that form the supporting core layer, the functional intermediate layer and the tactile surface layer are simultaneously extruded through a composite spinning assembly to form nascent fibers with a three-layer composite structure. The nascent fibers are subjected to bio-enzymatic polishing treatment; The fibers that have undergone bio-enzyme polishing are subjected to supercritical carbon dioxide fluid expansion treatment. Ultra-soft fibers were obtained by subjecting the expanded fibers to low-temperature plasma surface modification treatment.

7. The preparation method according to claim 6, characterized in that, The bio-enzyme polishing treatment includes: immersing the nascent fibers in a buffer solution containing cellulase and / or protease for treatment at a temperature of 40℃~60℃ for a time of 30~90 minutes.

8. The preparation method according to claim 6, characterized in that, The conditions for the supercritical carbon dioxide fluid expansion treatment include: placing the fiber in a treatment container and introducing carbon dioxide gas, heating and pressurizing the carbon dioxide to reach a supercritical state, maintaining the condition at a pressure of 8~25MPa and a temperature of 35~60℃ for 1~3 hours, and then depressurizing at a rate of 0.5~2MPa / s.

9. The preparation method according to claim 6, characterized in that, The low-temperature plasma surface modification treatment includes a first stage and a second stage. The first stage includes: surface activation and etching of the fiber under a nitrogen atmosphere, wherein the nitrogen flow rate is controlled at 10~30 L / min, the power of the plasma generator is controlled at 100~180W, and the treatment time is 2~5 minutes. The second stage includes: switching the reaction atmosphere to a mixture of nitrogen and oxygen, wherein the oxygen volume fraction in the mixture is 20%~40%, the power of the plasma generator is increased to 200~300W, and the treatment time is 5~12 minutes.

10. The preparation method according to claim 6, characterized in that, The spinning raw material forming the supporting core layer is polyethylene terephthalate or polyamide melt; the spinning raw material forming the functional intermediate layer is regenerated cellulose fiber solution; and the spinning raw material forming the tactile surface layer is bamboo pulp or alginate aqueous spinning solution.

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