Moisture-Heat Synergistic Management Multilayer Nanofiber Membrane Based on Sugar Alcohol and Its Preparation Method

Abstract

The present invention relates to the field of functional fiber materials, and discloses a multi-layer nanofiber membrane for synergistic management of humidity and heat based on sugar alcohol and a preparation method thereof. The multi-layer nanofiber membrane comprises a sugar alcohol@UCST type thermosensitive polymer nanofiber membrane layer, a sugar alcohol@PU nanofiber membrane layer and a sugar alcohol@LCST type thermosensitive polymer nanofiber membrane layer which are composited in sequence. In the present invention, sugar alcohol is respectively encapsulated in a UCST type thermosensitive polymer, PU and an LCST type thermosensitive polymer by coaxial electrospinning to prepare an intelligent multi-layer nanofiber membrane with temperature responsiveness for synergistic management of humidity and heat. At high temperatures, after the material comes into contact with skin sweat, it can conduct the sweat outwards, and at the same time, the sugar alcohol absorbs moisture and dissolves, achieving the effect of cooling the human body; at low temperatures, the sugar alcohol solidifies and releases heat, and the multi-layer nanofiber membrane becomes hydrophobic on the outside and hydrophilic on the inside, so that moisture and heat are locked inside, achieving the effect of locking moisture and keeping warm.

Description

Technical Field

[0001] The present invention relates to the field of functional fiber materials, and particularly to a multi-layer nanofiber membrane for synergistic management of humidity and heat based on sugar alcohol and a preparation method thereof. Background Art

[0002] With the continuous increase of the global temperature, the annual refrigeration energy consumption accounts for a quite large proportion. Thermal comfort and health are essential physiological and psychological needs of people, and currently they are all met based on space cooling technology. Space cooling technology has high energy consumption and low utilization efficiency. Therefore, it is urgent to develop efficient personal-based thermal management materials. Based on different heat dissipation methods of the human body, a large number of thermal management materials have been invented (such as radiative cooling, conductive cooling, and moisture absorption cooling), but most of the materials are complex in preparation and application, and it is difficult to achieve the synergistic management of sweat and heat on the human skin.

[0003] Chinese Patent CN107022799A discloses a fiber for long-term cool cooling. It uses a mesoporous material with high nano-porosity as the base material, disperses the phase change material and fills it into the pores of the base material, then mixes it with a high specific heat material, and then adds it to various fibers to form a cooling fiber; the material undergoes a phase change through body heat to achieve a cooling and cool cooling effect. The preparation of this material is complex, the cooling depends on the body heat temperature, and the cooling effect is limited, and it cannot achieve the synergistic management of sweat and body temperature. Chinese Patent CN111576044A discloses a preparation method of an efficient radiative cooling fiber, which includes the following steps: (1) extruding and molding a polymer melt and then cooling to obtain a nascent fiber; (2) spraying and modifying the nascent fiber with a modified slurry, and the modified slurry includes 50-90% of polyacrylate emulsion and 10-50% of core-shell structure radiative cooling particles, the core of the core-shell structure radiative cooling particles is a heat-reflecting particle, and the shell layer is a light-transmitting radiative layer; (3) the nascent fiber after spraying and modification is oiled and then enters a hot air spinning channel for spinning; (4) after spinning, it is stretched and wound to obtain an efficient radiative cooling fiber. The present invention combines the outward radiation of the far-infrared rays radiated by the human body by the shell layer of the core-shell structure radiative cooling particles and the reflection of the external visible light and near-infrared light by the core, so that the fiber achieves the radiative cooling effect. In a hot climate environment, this material cannot achieve the synchronous management of humidity and heat of the human body. Chinese Patent CN112252019A discloses a sweat-cooling fabric, and a super-hydrophilic structure is processed on one side surface of a hydrophobic fabric, so that one side of the fabric is a hydrophobic surface and the other side is a hydrophilic surface. This design can form a super-hydrophilic structure on one side of the hydrophobic fabric, so that the sweat on the hydrophobic surface of the fabric can quickly penetrate to the hydrophilic surface of the fabric and evaporate on the hydrophilic surface of the fabric to achieve the function of sweat-cooling. However, the cooling performance of this material completely depends on the evaporation of sweat, and the cooling effect is limited.

[0004] In summary, various cooling fiber materials in the prior art all have their own defects, so it is of practical significance to invent a fiber material that can coordinate moisture and heat management and directly and effectively cool down.

[0005] Sugar alcohols have good hygroscopic heat of dissolution. When dissolved, they can absorb a large amount of surrounding heat and have excellent cooling performance. Sugar alcohols are abundant in production and have good biocompatibility, and have the research potential of human body cooling materials. However, how to cleverly use sugar alcohols to effectively exert their performance is a challenge. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a multilayer nanofiber membrane for moisture and heat coordinated management based on sugar alcohols and a preparation method thereof. The present invention wraps sugar alcohols in UCST-type thermosensitive polymers, PU and LCST-type thermosensitive polymers respectively through coaxial electrospinning to obtain a temperature-responsive intelligent moisture and heat coordinated management multilayer nanofiber membrane. At high temperatures, the material can conduct sweat outward after contacting the skin, while the sugar alcohol absorbs moisture and dissolves, which has a cooling effect on the human body; at low temperatures, the sugar alcohol solidifies and releases heat, and the multilayer nanofiber membrane becomes hydrophobic on the outside and hydrophilic on the inside, so that moisture and heat are locked inside, achieving a moisture-locking and heat-insulating effect.

[0007] The specific technical scheme of the present invention is:

[0008] In a first aspect, the present invention provides a multilayer nanofiber membrane for moisture-heat synergistic management based on sugar alcohols, comprising the following three layers compounded in sequence:

[0009] Sugar alcohol@UCST type thermosensitive polymer nanofiber membrane layer, sugar alcohol@UCST type thermosensitive polymer nanofiber presents a core-shell structure, the core layer is sugar alcohol, and the shell layer is UCST type thermosensitive polymer;

[0010] Sugar alcohol@PU nanofiber membrane layer, sugar alcohol@PU nanofiber presents a core-shell structure, the core layer is sugar alcohol, and the shell layer is PU;

[0011] The sugar alcohol@LCST type thermosensitive polymer nanofiber membrane layer is used to fit the skin. The sugar alcohol@LCST type thermosensitive polymer nanofiber has a core-shell structure, the core layer is sugar alcohol, and the shell layer is LCST type thermosensitive polymer.

[0012] As described in the background art of the present application, the existing preparation methods of human body cooling materials are complex and cannot achieve effective management of the combination of humidity and heat. Sugar alcohols have low cost and particularly good moisture absorption and cooling performance. However, how to use them to prepare composite materials with the combination of humidity and heat management for skin thermal management is a challenging problem. For this reason, the present invention attempts to use the coaxial electrospinning technology to first coat sugar alcohols in UCST nanofibers to obtain a sugar alcohol@UCST type thermosensitive polymer nanofiber membrane layer; then coat sugar alcohols in PU nanofibers to obtain a sugar alcohol@PU nanofiber membrane layer; and finally coat sugar alcohols in LCST nanofibers to obtain a sugar alcohol@LCST type thermosensitive polymer nanofiber membrane layer. In the above three-layer composite structure, the sugar alcohol@LCST type thermosensitive polymer nanofiber membrane layer is used to fit with the skin, and the sugar alcohol@UCST type thermosensitive polymer nanofiber membrane layer is located on the outermost layer; while the sugar alcohol@PU nanofiber membrane layer serves as a wettability gradient layer.

[0013] The principle of the present invention for the combination of humidity and heat management of the multi-layer nanofiber membrane is as follows: After the sugar alcohol@LCST type thermosensitive polymer nanofiber membrane layer of the membrane is attached to the skin surface, when the skin is in a high-temperature state and sweating, using the thermal response behavior of the thermosensitive polymer, the inner LCST type thermosensitive polymer is hydrophobic, the outer UCST type thermosensitive polymer is hydrophilic, and the hydrophilicity and hydrophobicity of the sugar alcohol@PU nanofiber membrane layer are between the two. Thus, a Laplace pressure difference is generated among the three, and with the participation of capillary force, the sweat on the skin surface can be efficiently transported unidirectionally from the LCST side to the UCST hydrophilic side. During this process, the sugar alcohols loaded in the nanofibers absorb moisture and dissolve, absorbing the surrounding heat to achieve the purpose of skin cooling, realizing the coordinated management of sweat and heat, and keeping the skin state dry and cool. At low temperature, the inner LCST type thermosensitive polymer is hydrophilic, the outer UCST type thermosensitive polymer is hydrophobic, transforming into an outer UCST hydrophobic - inner LCST hydrophilic structure, which can lock water vapor and heat inside the membrane, thus realizing the self-adaptive microclimate humidity and heat management balance.

[0014] Preferably, the sugar alcohol is selected from sorbitol and xylitol.

[0015] Sugar alcohol substances belong to small molecule compounds and have the characteristics of moisture absorption and heat absorption. Through previous experiments, the present invention found that most small molecule compounds are not suitable for being processed into nanofibers alone by electrospinning because the viscosity of the small molecule compound solution is relatively low and the fluidity is too high. To effectively exert the moisture absorption and heat absorption function of sugar alcohol substances, the present invention uses the core-shell electrospinning technology to wrap sugar alcohols in the core layer of nanofibers, so that the nanofibers can absorb moisture and heat to achieve the purpose of humidity and heat management.

[0016] Preferably, the UCST type thermosensitive polymer is poly(N,N-dimethyl(methacryloylethyl)ammonium propane sulfonate) having a critical transition temperature of 26-27°C.

[0017] 26℃ is considered to be the most comfortable body temperature. As a UCST-type thermosensitive polymer, poly(N,N-dimethyl(methacryloylethyl)ammonium propane sulfonate) has a critical transition temperature of 26-27℃, which is close to the most comfortable body temperature. Therefore, it is very suitable as a polymer material for thermal management. When the temperature is high, poly(N,N-dimethyl(methacryloylethyl)ammonium propane sulfonate) will become hydrophilic, thereby generating a Laplace pressure difference with the LCST-type thermosensitive polymer with opposite wettability. With the participation of capillary force, sweat can be transported to the side away from the body surface.

[0018] The LCST type thermosensitive polymer is poly(acrylamide-co-acrylonitrile-co-N-hydroxymethyl acrylamide), the critical transition temperature is 26-27° C., and the molar ratio of the three monomers is (70-79%):(16-20%):(10-5%).

[0019] In order to coordinate with the temperature transition point of the UCST type thermosensitive polymer, the LCST type thermosensitive polymer of the present invention adopts poly(acrylamide-co-acrylonitrile-co-N-hydroxymethyl acrylamide), whose critical transition point is 26-27°C, so that the perspiration mechanism can be changed under a very close temperature environment, from efficient perspiration to temperature locking and moisture retention.

[0020] Preferably, the thickness of the sugar alcohol@UCST type thermosensitive polymer nanofiber membrane layer is 30-60 μm; the thickness of the sugar alcohol@PU nanofiber membrane layer is 10-20 μm; the thickness of the sugar alcohol@LCST type thermosensitive polymer nanofiber membrane layer is 5-10 μm.

[0021] The thickness of each single-layer nanofiber membrane has a certain influence on the material's synergistic management performance of moisture and heat. Specifically, for the outer layer of the sugar alcohol @ UCST thermosensitive polymer nanofiber membrane layer, if the thickness is too thin, it cannot provide good hydrophilicity for the absorption of sweat at high temperature; on the contrary, if the thickness is too thick, the material will have poor air permeability. For the interlayer sugar alcohol @ PU nanofiber membrane layer, if the thickness is too thick, the forward transport of sweat will be blocked, which is not conducive to the efficient perspiration of the material; on the contrary, if the thickness is too thin, it will not provide an effective wettability gradient. For the inner layer of the sugar alcohol @ LCST thermosensitive polymer nanofiber membrane layer, if the thickness is too thick, sweat will find it difficult to overcome the resistance of the hydrophobic layer and be discharged at high temperature, resulting in poor air permeability of the material; on the contrary, if the thickness is too thin, the sweat discharged at high temperature may re-infiltrate the skin, causing the material to adhere to the skin and reduce the sense of comfort.

[0022] Second aspect, the present invention provides a method for preparing a multi-layer nanofiber membrane for synergistic management of humidity and heat based on sugar alcohol, comprising the following steps:

[0023] (1) Using a sugar alcohol solution as the core layer spinning solution and a 10-20 wt% UCST-type thermosensitive polymer solution as the shell layer spinning solution, coaxial electrospinning is carried out using a high-voltage electrospinning machine, and the core-shell layer spinning flow rate ratio is 1:(7-9) to obtain a sugar alcohol@UCST-type thermosensitive polymer nanofiber membrane layer.

[0024] (2) Using a sugar alcohol solution as the core layer spinning solution and a 10-15 wt% polyurethane (PU) solution as the shell layer spinning solution, coaxial electrospinning is carried out on the surface of the sugar alcohol@UCST-type thermosensitive polymer nanofiber membrane layer to form a sugar alcohol@PU nanofiber membrane layer, and the core-shell layer spinning flow rate ratio is 1:(5-8) to obtain a nanofiber membrane with a composite wetting gradient layer.

[0025] (3) Using a sugar alcohol solution as the core layer spinning solution and a 10-20 wt% LCST-type thermosensitive polymer solution as the shell layer spinning solution, coaxial electrospinning is carried out on the surface of the sugar alcohol@PU nanofiber membrane layer to form a sugar alcohol@LCST-type thermosensitive polymer nanofiber membrane layer, and the core-shell layer spinning flow rate ratio is 1:(4-9) to obtain a multi-layer nanofiber membrane for synergistic management of humidity and heat based on sugar alcohol.

[0026] Since sugar alcohol is a small molecule substance, it is very difficult to prepare a core-shell nanofiber membrane by electrospinning. In order to successfully encapsulate it inside the shell polymer, the present invention finds that the control of the core-shell layer flow rate ratio during the electrospinning process of each layer of nanofiber membrane is crucial. The core-shell layer flow rate ratio has a significant impact on the microscopic morphology of the prepared core-shell nanofibers. If the core layer flow rate is too fast relative to the shell layer flow rate, the small molecule sugar alcohol cannot be encapsulated, resulting in the inability to form nanofibers and the exposure of sugar alcohol. If the core layer flow rate is relatively slow compared to the shell layer flow rate, the sugar alcohol loading is too small and the moisture absorption and cooling effect is poor.

[0027] In addition, the present invention also found that during the spinning process, the polymer concentration in each shell layer spinning solution has a significant impact on the performance of the multi-layer nanofiber membrane for synergistic management of heat and humidity. Specifically, for the outer layer of the sugar alcohol@UCST type thermosensitive polymer nanofiber membrane layer, if the polymer concentration is too low, the hydrophilic layer is too thin at high temperatures and cannot provide good hydrophilicity for the absorption of sweat; conversely, if the concentration is too high, the air permeability of the material will be poor, resulting in poor human comfort. For the sugar alcohol@PU nanofiber membrane layer in the interlayer, when the temperature changes, the hydrophilicity and hydrophobicity on both sides of the multi-layer nanofiber membrane change, and the wettability of PU is always between UCST and LCST type polymers, so it can provide a wetting gradient to accelerate the export of sweat. However, if the PU concentration is too high, the forward transport of sweat will be blocked, which is not conducive to the efficient sweating of the material; conversely, if the PU concentration is too low, an effective wetting gradient cannot be provided. For the inner layer of the sugar alcohol@LCST type thermosensitive polymer nanofiber membrane layer, if the polymer concentration is too high, it is difficult for sweat to overcome the resistance of the hydrophobic layer and be discharged at high temperatures, and the air permeability of the material will be poor, reducing comfort; conversely, if the polymer concentration is too low, the sweat discharged at high temperatures may re-wet the skin, resulting in the material adhering to the skin and a decrease in the sense of comfort.

[0028] Preferably, in steps (1) to (3), the concentration of the sugar alcohol solution is 60-70 wt%.

[0029] Preferably, in steps (1) to (3), the solvent of the sugar alcohol solution is water.

[0030] Preferably, in step (1), the solvent of the UCST type thermosensitive polymer solution is N,N-dimethylformamide.

[0031] Preferably, in step (2), the solvent of the polyurethane solution is a mixed solution of acetone and N,N-dimethylformamide, and the mass ratio is 1:(1-2).

[0032] Preferably, in step (3), the solvent of the LCST type thermosensitive polymer solution is N,N-dimethylformamide.

[0033] Preferably, in steps (1) to (3), the flow rate of the core layer spinning solution propulsion pump is 0.0002-0.0004 mm / s.

[0034] Preferably, in step (1), the spinning time is 3-5 h; in step (2), the spinning time is 10-30 min. In step (3), the spinning time is 10-30 min.

[0035] Preferably, in step (1), the coaxial electrospinning parameters are as follows: the needle gauge is 20 - 22G, the distance is 15 - 20 cm, the voltage is 18 - 28 kv, the temperature is 25 - 30 °C, and the humidity is 40 - 50% RH.

[0036] Preferably, in step (2), the coaxial electrospinning parameters are as follows: the needle gauge is 20 - 22G, the distance is 13 - 16 cm, the voltage is 9 - 11 kv, the temperature is 25 - 30 °C, and the humidity is 40 - 50% RH.

[0037] Preferably, in step (3), the coaxial electrospinning parameters are as follows: the needle gauge is 20 - 22G, the distance is 15 - 20 cm, the voltage is 10 - 14 kv, the temperature is 25 - 30 °C, and the humidity is 40 - 50% RH.

[0038] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention ingeniously utilizes the heat absorption property of sugar alcohol dissolution. Through coaxial electrospinning, small sugar alcohol molecules are respectively encapsulated in UCST - type thermosensitive polymers, PU, and LCST - type thermosensitive polymers to prepare a sequentially composite sugar alcohol@UCST - type thermosensitive polymer nanofiber membrane layer, sugar alcohol@PU nanofiber membrane layer, and sugar alcohol@LCST - type thermosensitive polymer nanofiber membrane layer, thereby obtaining an intelligent humid - heat synergistic management multi - layer nanofiber membrane with temperature responsiveness. In a high - temperature environment, based on the wettability gradient of the three - layer structure, when the material contacts skin sweat, it can conduct the sweat outwards. At the same time, the sugar alcohol in the nanofibers absorbs moisture and dissolves, absorbing the surrounding heat to achieve the effect of cooling the human body. At low temperatures, the sugar alcohol solidifies and releases heat, and the multi - layer nanofiber membrane becomes hydrophobic on the outside and hydrophilic on the inside, so that moisture and heat are locked inside, achieving the effect of locking moisture and keeping warm. Therefore, the multi - layer nanofiber membrane of the present invention can provide an intelligent humid - heat synergistic management for the human body, making the epidermal micro - environment reach a humid - heat balance. Description of the Drawings

[0039] Figure 1 shows the liquid - conducting process of the multi - layer nanofiber membrane in Example 1 under a high - temperature environment;

[0040] Figure 2 is the TEM photograph of the gradient - layer nanofibers in Example 1;

[0041] Figure 3 is the photograph of the non - liquid - conducting process of the multi - layer nanofiber membrane in Example 2 under a low - temperature environment;

[0042] Figure 4 is the photograph showing that the nanofiber membrane in Comparative Example 1 cannot conduct liquid unidirectionally;

[0043] Figure 5 is the SEM photograph of the multi - layer nanofiber membrane in Comparative Example 10. Detailed Embodiments

[0044] The present invention will be further described below in conjunction with embodiments.

[0045] Both sorbitol and xylitol are food-grade, and the PU used in the gradient layer is PU glue.

[0046] General Embodiment

[0047] A multi-layer nanofiber membrane for synergistic management of humidity and heat based on sugar alcohol, comprising the following three layers laminated in sequence: a sugar alcohol@UCST-type thermosensitive polymer nanofiber membrane layer (with a thickness of 30 - 60 μm), a sugar alcohol@PU nanofiber membrane layer (with a thickness of 10 - 20 μm), and a sugar alcohol@LCST-type thermosensitive polymer nanofiber membrane layer (with a thickness of 5 - 10 μm). Among them, the sugar alcohol@UCST-type thermosensitive polymer nanofibers have a core-shell structure, with the core layer being sugar alcohol and the shell layer being a UCST-type thermosensitive polymer; the sugar alcohol@PU nanofibers have a core-shell structure, with the core layer being sugar alcohol and the shell layer being PU; the sugar alcohol@LCST-type thermosensitive polymer nanofibers have a core-shell structure, with the core layer being sugar alcohol and the shell layer being an LCST-type thermosensitive polymer.

[0048] Preferably, the sugar alcohol is selected from sorbitol and xylitol; the UCST-type thermosensitive polymer is poly(N,N-dimethyl(methacryloylethyl)ammonium propane sulfonate), with a critical transition temperature of 26 - 27 °C; the LCST-type thermosensitive polymer is poly(acrylamide-co-acrylonitrile-co-N-hydroxymethylacrylamide), with a critical transition temperature of 26 - 27 °C, and the molar ratio of the three monomers is (70 - 79%)∶(16 - 20%)∶(10 - 5%).

[0049] The preparation method of the above multi-layer nanofiber membrane for synergistic management of humidity and heat based on sugar alcohol includes the following steps:

[0050] (1) Using a 60 - 70 wt% sugar alcohol solution (preferably water as the solvent) as the core layer spinning solution and a 10 - 20 wt% UCST-type thermosensitive polymer solution (preferably N,N-dimethylformamide as the solvent) as the shell layer spinning solution, coaxial electrospinning is carried out using a high-voltage electrospinning machine to obtain the sugar alcohol@UCST-type thermosensitive polymer nanofiber membrane layer. The coaxial electrospinning parameters are: needle size 20 - 22G, distance 15 - 20 cm, voltage 18 - 28 kv, temperature 25 - 30 °C, humidity 40 - 50% RH, the flow rate of the core layer spinning solution feeding pump is 0.0002 - 0.0004 mm / s, the spinning flow rate ratio of the core-shell layer is 1∶(7 - 9), and the spinning time is 3 - 5 h.

[0051] (2) Using a sugar alcohol solution at 60-70 wt% (preferably water as the solvent) as the core layer spinning solution, and a polyurethane (PU) solution at 10-15 wt% (preferably a mixed solution of acetone and N,N-dimethylformamide with a mass ratio of 1:(1-2)) as the shell layer spinning solution, coaxial electrospinning is carried out on the surface of the sugar alcohol@UCST type thermosensitive polymer nanofiber membrane layer to form a sugar alcohol@PU nanofiber membrane layer, obtaining a nanofiber membrane with a composite wetting gradient layer. The coaxial electrospinning parameters are: needle size 20-22G, distance 13-16 cm, voltage 9-11 kv, temperature 25-30 °C, humidity 40-50%RH, the flow rate of the core layer spinning solution propulsion pump is 0.0002-0.0004 mm / s, the core-shell layer spinning flow rate ratio is 1:(5-8), and the spinning time is 10-30 min.

[0052] (3) Using a sugar alcohol solution at 60-70 wt% (preferably water as the solvent) as the core layer spinning solution, and an LCST type thermosensitive polymer solution at 10-20 wt% (preferably N,N-dimethylformamide as the solvent) as the shell layer spinning solution, coaxial electrospinning is carried out on the surface of the sugar alcohol@PU nanofiber membrane layer to form a sugar alcohol@LCST type thermosensitive polymer nanofiber membrane layer, obtaining a multi-layer nanofiber membrane for synergistic management of heat and humidity based on sugar alcohol. The coaxial electrospinning parameters are: needle size 20-22G, distance 15-20 cm, voltage 10-14 kv, temperature 25-30 °C, humidity 40-50%RH, the flow rate of the core layer spinning solution propulsion pump is 0.0002-0.0004 mm / s, the core-shell layer spinning flow rate ratio is 1:(4-9), and the spinning time is 10-30 min.

[0053] Example 1

[0054] (1) Using a 60 wt% aqueous solution of xylitol and an N,N-dimethylformamide solution of 12 wt% poly(N,N-dimethyl(methacryloylethyl)ammonium propane sulfonate) (critical transition temperature is 26 °C) as the core layer and shell layer spinning solutions respectively, coaxial spinning is carried out using a high-voltage electrospinning machine. The electrospinning parameters are: needle size 22G, distance 15 cm, voltage 18 kv, temperature 25-30 °C, humidity 40-50%RH, spinning time is 3 h, the flow rate of the shell layer spinning solution is 0.0016 mm / s, the flow rate of the core layer spinning solution is 0.0002 mm / s, and the layer thickness is 30 μm, obtaining a sugar alcohol@UCST type thermosensitive polymer nanofiber membrane.

[0055] (2) Dissolve polyurethane (PU) in a mixed solution of acetone and N,N-dimethylformamide (mass ratio 1:1) to prepare a 13 wt% shell spinning solution, and use a 60 wt% aqueous xylitol solution as the core spinning solution. Using the nanofiber membrane obtained in (1) as the base membrane, conduct coaxial electrospinning. The electrospinning parameters are: needle 22G, distance 13 cm, voltage 10 kv, temperature 25 - 30 °C, humidity 40 - 50% RH, spinning time 20 min, shell spinning solution flow rate 0.0012 mm / s, core spinning solution flow rate 0.0002 mm / s, layer thickness 15 μm, to obtain a nanofiber membrane with a composite wetting gradient layer.

[0056] (3) Add poly(acrylamide-co-acrylonitrile-co-N-hydroxymethylacrylamide) with a critical transition temperature of 26 °C (molar contents of the three monomers are 77%, 18%, and 5%) to N,N-dimethylformamide to prepare a 15 wt% shell spinning solution, and use a 60 wt% aqueous xylitol solution as the core spinning solution. Using the nanofiber membrane obtained in (2) as the base membrane, use an electrospinning device to spin the core spinning solution and the shell solution onto the PU side of the base membrane. The relevant electrospinning parameters are: needle size 22G, distance 13 cm, voltage 9 kv, temperature 25 - 30 °C, humidity 40 - 50% RH, spinning time 15 min, shell spinning solution flow rate 0.001 mm / s, core spinning solution flow rate 0.0002 mm / s, layer thickness 5 μm, to obtain a nanofiber membrane for thermohygroscopic synergistic management.

[0057] Example 2

[0058] (1) Use a 60 wt% aqueous xylitol solution and an N,N-dimethylformamide solution of 12 wt% poly(N,N-dimethyl(methacryloylethyl)ammonium propane sulfonate) (critical transition temperature 26 °C) as the core and shell spinning solutions respectively, and conduct coaxial electrospinning using a high-voltage electrospinning machine. The electrospinning parameters are: needle size 22G, distance 16 cm, voltage 18 kv, temperature 25 - 30 °C, humidity 40 - 50% RH, spinning time 3 h, shell spinning solution flow rate 0.0016 mm / s, core spinning solution flow rate 0.0002 mm / s, layer thickness 30 μm, to obtain a sugar alcohol@UCST type thermosensitive polymer nanofiber membrane.

[0059] (2) Dissolve polyurethane (PU) in a mixed solution of acetone and N,N-dimethylformamide (mass ratio 1:1) to prepare a 13 wt% shell spinning solution, and use a 60 wt% aqueous xylitol solution as the core spinning solution. Using the nanofiber membrane obtained in (1) as the base membrane, conduct coaxial electrospinning. The electrospinning parameters are: needle 22G, distance 13 cm, voltage 10 kV, temperature 25 - 30 °C, humidity 40 - 50% RH, spinning time 20 min, shell spinning solution flow rate 0.0012 mm / s, core spinning solution flow rate 0.0002 mm / s, layer thickness 15 μm, to obtain a nanofiber membrane with a composite wetting gradient layer.

[0060] (3) Add poly(acrylamide-co-acrylonitrile-co-N-hydroxymethylacrylamide) with a critical transition temperature of 26 °C (molar contents of the three monomers are 77%, 18%, and 5%) to N,N-dimethylformamide to prepare a 15 wt% shell spinning solution, and use a 60 wt% aqueous xylitol solution as the core spinning solution. Using the nanofiber membrane obtained in (2) as the base membrane, use an electrospinning device to spin the core spinning solution and the shell solution onto the PU side of the base membrane. The relevant electrospinning parameters are: needle size 22G, distance 13 cm, voltage 9 kV, temperature 25 - 30 °C, humidity 40 - 50% RH, spinning time 15 min, shell spinning solution flow rate 0.001 mm / s, core spinning solution flow rate 0.0002 mm / s, layer thickness 5 μm, to obtain a nanofiber membrane for synergistic management of heat and humidity.

[0061] Example 3

[0062] (1) Use a 60 wt% aqueous xylitol solution and an N,N-dimethylformamide solution of 12 wt% poly(N,N-dimethyl(methacryloylethyl)ammonium propane sulfonate) (critical transition temperature 26 °C) as the core and shell spinning solutions respectively, and conduct coaxial electrospinning using a high-voltage electrospinning machine. The electrospinning parameters are: needle size 22G, distance 15 cm, voltage 18 kV, temperature 25 - 30 °C, humidity 40 - 50% RH, spinning time 3 h, shell spinning solution flow rate 0.0016 mm / s, core spinning solution flow rate 0.0002 mm / s, layer thickness 30 μm, to obtain a sugar alcohol@UCST type thermosensitive polymer nanofiber membrane.

[0063] (2) Dissolve polyurethane (PU) in a mixed solution of acetone and N,N-dimethylformamide (mass ratio 1:1) to prepare a 13 wt% shell spinning solution, and use a 60 wt% aqueous xylitol solution as the core spinning solution. Using the nanofiber membrane obtained in (1) as the base membrane, perform coaxial electrospinning. The electrospinning parameters are: needle 22G, distance 13 cm, voltage 10 kV, temperature 25 - 30 °C, humidity 40 - 50% RH, spinning time 20 min, shell spinning solution flow rate 0.0012 mm / s, core spinning solution flow rate 0.0002 mm / s, layer thickness 15 μm, to obtain a nanofiber membrane with a composite wetting gradient layer.

[0064] (3) Add poly(acrylamide-co-acrylonitrile-co-N-hydroxymethylacrylamide) with a critical transition temperature of 26 °C (molar contents of the three monomers are 77%, 18%, and 5%) to N,N-dimethylformamide to prepare a 15 wt% shell spinning solution, and use a 60 wt% aqueous xylitol solution as the core spinning solution. Using the nanofiber membrane obtained in (2) as the base membrane, use an electrospinning device to spin the core spinning solution and the shell solution onto the PU side of the base membrane. The relevant electrospinning parameters are: needle size 22G, distance 13 cm, voltage 9 kV, temperature 25 - 30 °C, humidity 40 - 50% RH, spinning time 15 min, shell spinning solution flow rate 0.001 mm / s, core spinning solution flow rate 0.0002 mm / s, layer thickness 5 μm, to obtain a nanofiber membrane for thermohygroscopic synergistic management.

[0065] Comparative Example 1 (single gradient layer)

[0066] (1) Dissolve polyurethane (PU) in a mixed solution of acetone and N,N-dimethylformamide (mass ratio 1:1) to prepare a 13 wt% shell spinning solution, and use a 60 wt% aqueous xylitol solution as the core spinning solution. Perform coaxial electrospinning. The electrospinning parameters are: needle 22G, distance 13 cm, voltage 10 kV, temperature 25 - 30 °C, humidity 40 - 50% RH, spinning time 20 min, shell spinning solution flow rate 0.0012 mm / s, core spinning solution flow rate 0.0002 mm / s, layer thickness 15 μm, to obtain a nanofiber membrane.

[0067] Comparative Example 2 (without sugar alcohol)

[0068] (1) Prepare a spinning solution by mixing a 12 wt% solution of poly(N,N-dimethyl(methacryloylethyl)ammonium propane sulfonate) (critical transition temperature: 26 °C) in N,N-dimethylformamide. Then, perform electrospinning using a high-voltage electrospinning machine. The electrospinning parameters are as follows: needle gauge 22G, distance 15 cm, voltage 18 kV, temperature 25 - 30 °C, humidity 40 - 50% RH, spinning time 3 h, spinning solution flow rate 0.0016 mm / s, and layer thickness 30 μm, to obtain a UCST-type thermosensitive polymer nanofiber membrane.

[0069] (2) Dissolve polyurethane (PU) in a mixed solution of acetone and N,N-dimethylformamide (mass ratio 1:1) to prepare a 13 wt% spinning solution. Using the nanofiber membrane obtained in (1) as the base membrane, perform electrospinning. The electrospinning parameters are: needle 22G, distance 13 cm, voltage 10 kV, temperature 25 - 30 °C, humidity 40 - 50% RH, spinning time 20 min, spinning solution flow rate 0.0012 mm / s, and layer thickness 15 μm, to obtain a nanofiber membrane with a composite wetting gradient layer.

[0070] (3) Add poly(acrylamide-co-acrylonitrile-co-N-hydroxymethylacrylamide) (molar contents of the three monomers are 77%, 18%, and 5%) with a critical transition temperature of 26 °C to N,N-dimethylformamide to prepare a 15 wt% spinning solution. Using the nanofiber membrane obtained in (2) as the base membrane, use an electrospinning device to spin the spinning solution onto the PU side of the base membrane. The relevant electrospinning parameters are: needle gauge 22G, distance 13 cm, voltage 9 kV, temperature 25 - 30 °C, humidity 40 - 50% RH, spinning time 15 min, spinning solution flow rate 0.001 mm / s, and layer thickness 5 μm, to obtain a nanofiber membrane.

[0071] Comparative Example 3 (without gradient layer)

[0072] (1) Use a 60 wt% aqueous xylitol solution and a 12 wt% solution of poly(N,N-dimethyl(methacryloylethyl)ammonium propane sulfonate) (critical transition temperature: 26 °C) in N,N-dimethylformamide as the core layer and shell layer spinning solutions respectively, and perform coaxial electrospinning using a high-voltage electrospinning machine. The electrospinning parameters are: needle gauge 22G, distance 15 cm, voltage 18 kV, temperature 25 - 30 °C, humidity 40 - 50% RH, spinning time 3 h, shell layer spinning solution flow rate 0.0016 mm / s, core layer spinning solution flow rate 0.0002 mm / s, and layer thickness 30 μm, to obtain a xylitol@UCST-type thermosensitive polymer nanofiber membrane.

[0073] (2) Poly(acrylamide-co-acrylonitrile-co-N-hydroxymethylacrylamide) with a critical transition temperature of 26 °C (the molar contents of the three monomers are 77%, 18% and 5%) was added to N,N-dimethylformamide to prepare a 15 wt% shell spinning solution, and a 60 wt% aqueous xylitol solution was used as the core spinning solution. Using the nanofiber membrane obtained in (1) as the substrate membrane, the core spinning solution and the shell solution were spun onto the substrate membrane by an electrospinning device. The relevant electrospinning parameters were: needle gauge 22G, distance 13 cm, voltage 9 kV, temperature 25 - 30 °C, humidity 40 - 50% RH, spinning time 15 min, the flow rate of the shell spinning solution was 0.001 mm / s, the flow rate of the core spinning solution was 0.0002 mm / s, and the layer thickness was 5 μm to obtain a nanofiber membrane.

[0074] The nanofiber membranes in each example and comparative example were tested. The surface morphology of the nanofibers was characterized by scanning electron microscopy (SEM). The unidirectional transport performance and the moisture absorption and cooling performance were characterized as follows:

[0075] Hydrostatic pressure difference test: First, fix the hydrophobic side of the material upward between two filter cups, use a dropper to drip water into the upper filter cup until the first drop of water drips from below the membrane, and record the liquid column height at this time. Reverse the direction of the membrane and repeat the above operation to record the liquid column height. The hydrostatic pressure difference is the difference between the two liquid column heights.

[0076] Unidirectional transport performance test: Under high temperature (35 °C) and low temperature (20 °C) environments, clamp both ends of the nanofiber membrane material to be tested (with the hydrophobic layer upward) by a fixing platform, use a dropper to drip water droplets on the upper surface of the nanofiber membrane and observe the movement of the water droplets over time; then reverse the front and back sides of the material and observe the movement of the water droplets in the same previous steps.

[0077] Moisture absorption and cooling performance test: The moisture absorption and cooling effect of the nanofiber membrane was carried out in a space with a relatively stable ambient temperature. First, moisten the arm skin with water vapor, then attach the nanofiber membrane to the arm, and use a thermocouple surface temperature sensor to measure the temperature change of the membrane surface before and after moisture absorption. The results are as follows:

[0078]

[0079] As can be seen from the above table results, by using two types of thermosensitive polymers to prepare core-shell structured nanofibers loaded with sugar alcohols and compounding a wettability gradient layer, a three-layer structured nanofiber composite material can be obtained, which is used to efficiently unidirectionally conduct sweat in a high-temperature environment and achieve a cooling effect. When the temperature is low, a moisture-locking and heat-preserving function is realized. At the same time, the presence of the wetting gradient layer will also enhance the moisture-locking and heat-preserving effect, thereby constructing an intelligent balance of moisture and temperature (Examples 1 - 3). Among them, Figure 1 is the unidirectional liquid conduction process of Example 1 in a high-temperature environment.Figure 3 Photo showing that Example 2 cannot conduct liquid unidirectionally in a low-temperature environment.

[0080] If the nanofiber membrane is a single-layer sugar alcohol@PU nanofiber membrane layer (Comparative Example 1), there is no hydrostatic pressure difference on both sides of the membrane, so it cannot achieve unidirectional sweat export in a high-temperature environment (as Figure 4 shown), nor can it prevent heat dissipation in a low-temperature environment. The loading amount of sugar alcohol in the single-layer membrane is small, which will also reduce the cooling effect. If the nanofiber membrane is not loaded with sugar alcohol (Comparative Example 2), the material does not have a cooling performance. If the gradient layer is missing in the nanofiber membrane (Comparative Example 3), the hydrostatic pressure difference on both sides of the membrane decreases, and the sweating and heat preservation efficiency are reduced.

[0081] Comparative Example 4 (too long spinning time of the gradient layer)

[0082] (1) Respectively use a 60 wt% aqueous solution of xylitol and a solution of 12 wt% poly(N,N-dimethyl(methacryloylethyl)(critical transition temperature is 26 °C)ammonium propane sulfonate) in N,N-dimethylformamide as the core layer and shell layer spinning solutions, and use a high-voltage electrospinning machine for coaxial electrospinning. The electrospinning parameters are: needle size 22G, distance 15 cm, voltage 18 kv, temperature 25 - 30 °C, humidity 40 - 50% RH, spinning time 3 h, shell layer spinning solution flow rate 0.0016 mm / s, core layer spinning solution flow rate 0.0002 mm / s, layer thickness 30 μm, to obtain a sugar alcohol@UCST type thermosensitive polymer nanofiber membrane.

[0083] (2) Dissolve polyurethane (PU) in a mixed solution of acetone and N,N-dimethylformamide (mass ratio 1:1) to prepare a 13 wt% shell layer spinning solution, and use a 60 wt% aqueous solution of xylitol as the core layer spinning solution. Using the nanofiber membrane obtained in (1) as the base membrane, perform coaxial electrospinning. The electrospinning parameters are needle 22G, distance 13 cm, voltage 10 kv, temperature 25 - 30 °C, humidity 40 - 50% RH, spinning time 1 h, shell layer spinning solution flow rate 0.0012 mm / s, core layer spinning solution flow rate 0.0002 mm / s, layer thickness 45 μm, to obtain a nanofiber membrane with a composite wetting gradient layer.

[0084] (3) Poly(acrylamide-co-acrylonitrile-co-N-hydroxymethylacrylamide) with a critical transition temperature of 26 °C (the molar contents of the three monomers are 77%, 18%, and 5%) was added to N,N-dimethylformamide to prepare a 15 wt% shell spinning solution, and a 60 wt% aqueous xylitol solution was used as the core spinning solution. Using the nanofiber membrane obtained in (2) as the base membrane, the core spinning solution and the shell solution were electrospun onto the PU side of the base membrane. The relevant electrospinning parameters were: needle gauge 22G, distance 13 cm, voltage 9 kV, temperature 25 - 30 °C, humidity 40 - 50% RH, spinning time 15 min, shell spinning solution flow rate 0.001 mm / s, core spinning solution flow rate 0.0002 mm / s, layer thickness 5 μm, and a nanofiber membrane was obtained.

[0085] Comparative Example 5 (Excessively long spinning time of sugar alcohol@UCST type thermosensitive polymer)

[0086] (1) A 60 wt% aqueous xylitol solution and a N,N-dimethylformamide solution of 12 wt% poly(N,N-dimethyl(methacryloylethyl)ammonium propane sulfonate) (with a critical transition temperature of 26 °C) were used as the core and shell spinning solutions respectively, and coaxial electrospinning was carried out using a high-voltage electrospinning machine. The electrospinning parameters were: needle gauge 22G, distance 15 cm, voltage 18 kV, temperature 25 - 30 °C, humidity 40 - 50% RH, spinning time 8 h, shell spinning solution flow rate 0.0016 mm / s, core spinning solution flow rate 0.0002 mm / s, layer thickness 80 μm, and a sugar alcohol@UCST type thermosensitive polymer nanofiber membrane was obtained.

[0087] (2) Polyurethane (PU) with a critical transition temperature of 26 °C was dissolved in a mixed solution of acetone and N,N-dimethylformamide (mass ratio 1:1) to prepare a 13 wt% shell spinning solution, and a 60 wt% aqueous xylitol solution was used as the core spinning solution. Using the nanofiber membrane obtained in (1) as the base membrane, coaxial electrospinning was carried out. The spinning parameters were needle 22G, distance 13 cm, voltage 10 kV, temperature 25 - 30 °C, humidity 40 - 50% RH, spinning time 20 min, shell spinning solution flow rate 0.0012 mm / s, core spinning solution flow rate 0.0002 mm / s, layer thickness 15 μm, and a nanofiber membrane with a composite wetting gradient layer was obtained.

[0088] (3) Poly(acrylamide-co-acrylonitrile-co-N-hydroxymethylacrylamide) with a critical transition temperature of 26 °C (the molar contents of the three monomers are 77%, 18% and 5%) was added to N,N-dimethylformamide to prepare a 15 wt% shell spinning solution, and a 60 wt% aqueous xylitol solution was used as the core spinning solution. Using the nanofiber membrane obtained in (2) as the base membrane, the core spinning solution and the shell solution were spun onto the PU side of the base membrane by an electrospinning device. The relevant electrospinning parameters were: needle gauge 22G, distance 13 cm, voltage 9 kV, temperature 25 - 30 °C, humidity 40 - 50% RH, spinning time 15 min, the flow rate of the shell spinning solution was 0.001 mm / s, the flow rate of the core spinning solution was 0.0002 mm / s, and the layer thickness was 5 μm to obtain a nanofiber membrane.

[0089] Comparative Example 6 (Too short spinning time of sugar alcohol@UCST type thermosensitive polymer)

[0090] (1) A 60 wt% aqueous xylitol solution and an N,N-dimethylformamide solution of 12 wt% poly(N,N-dimethyl(methacryloylethyl)ammonium sulfonate) (critical transition temperature of 26 °C) were used as the core and shell spinning solutions respectively, and coaxial electrospinning was carried out using a high-voltage electrospinning machine. The electrospinning parameters were: needle gauge 22G, distance 15 cm, voltage 18 kV, temperature 25 - 30 °C, humidity 40 - 50% RH, spinning time 30 min, the flow rate of the shell spinning solution was 0.0016 mm / s, the flow rate of the core spinning solution was 0.0002 mm / s, and the layer thickness was 5 μm to obtain a sugar alcohol@UCST type thermosensitive polymer nanofiber membrane.

[0091] (2) Polyurethane (PU) was dissolved in a mixed solution of acetone and N,N-dimethylformamide (mass ratio 1:1) to prepare a 13 wt% shell spinning solution, and a 60 wt% aqueous xylitol solution was used as the core spinning solution. Using the nanofiber membrane obtained in (1) as the base membrane, coaxial electrospinning was carried out. The spinning parameters were needle 22G, distance 13 cm, voltage 10 k v , temperature 25 - 30 °C, humidity 40 - 50% RH, spinning time 20 min, the flow rate of the shell spinning solution was 0.0012 mm / s, the flow rate of the core spinning solution was 0.0002 mm / s, and the layer thickness was 15 μm to obtain a nanofiber membrane with a composite wetting gradient layer.

[0092] (3) Poly(acrylamide-co-acrylonitrile-co-N-hydroxymethylacrylamide) with a critical transition temperature of 26 °C (the molar contents of the three monomers are 77%, 18% and 5%) was added to N,N-dimethylformamide to prepare a 15 wt% shell spinning solution, and a 60 wt% aqueous xylitol solution was used as the core spinning solution. Using the nanofiber membrane obtained in (2) as the base membrane, the core spinning solution and the shell solution were spun onto the PU side of the base membrane by an electrospinning device. The relevant electrospinning parameters were: needle gauge 22G, distance 13 cm, voltage 9 kV, temperature 25 - 30 °C, humidity 40 - 50% RH, spinning time 15 min, the flow rate of the shell spinning solution was 0.001 mm / s, the flow rate of the core spinning solution was 0.0002 mm / s, and the layer thickness was 5 μm to obtain a nanofiber membrane.

[0093] Comparative Example 7 (Excessively long spinning time of sugar alcohol@LCST type thermosensitive polymer)

[0094] (1) A 60 wt% aqueous xylitol solution and an N,N-dimethylformamide solution of 12 wt% poly(N,N-dimethyl(methacryloylethyl)ammonium sulfonate) (critical transition temperature of 26 °C) were used as the core and shell spinning solutions respectively, and coaxial electrospinning was carried out using a high-voltage electrospinning machine. The electrospinning parameters were: needle gauge 22G, distance 15 cm, voltage 18 kV, temperature 25 - 30 °C, humidity 40 - 50% RH, spinning time 3 h, the flow rate of the shell spinning solution was 0.0016 mm / s, the flow rate of the core spinning solution was 0.0002 mm / s, and the layer thickness was 30 μm to obtain a sugar alcohol@UCST type thermosensitive polymer nanofiber membrane.

[0095] (2) Polyurethane (PU) was dissolved in a mixed solution of acetone and N,N-dimethylformamide (mass ratio 1:1) to prepare a 13 wt% shell spinning solution, and a 60 wt% aqueous xylitol solution was used as the core spinning solution. Using the nanofiber membrane obtained in (1) as the base membrane, coaxial electrospinning was carried out. The spinning parameters were needle 22G, distance 13 cm, voltage 10 kV, temperature 25 - 30 °C, humidity 40 - 50% RH, spinning time 20 min, the flow rate of the shell spinning solution was 0.0012 mm / s, the flow rate of the core spinning solution was 0.0002 mm / s, and the layer thickness was 15 μm to obtain a nanofiber membrane with a composite wetting gradient layer.

[0096] (3) Poly(acrylamide-co-acrylonitrile-co-N-hydroxymethylacrylamide) with a critical transition temperature of 26 °C (the molar contents of the three monomers are 77%, 18% and 5%) was added to N,N-dimethylformamide to prepare a 15 wt% shell spinning solution, and a 60 wt% aqueous xylitol solution was used as the core spinning solution. Using the nanofiber membrane obtained in (2) as the base membrane, the core spinning solution and the shell solution were electrospun onto the PU side of the base membrane. The relevant electrospinning parameters were: needle gauge 22G, distance 13 cm, voltage 9 kV, temperature 25 - 30 °C, humidity 40 - 50% RH, spinning time 2 h, the flow rate of the shell spinning solution was 0.001 mm / s, the flow rate of the core spinning solution was 0.0002 mm / s, and the layer thickness was 40 μm to obtain a nanofiber membrane.

[0097] Comparative Example 8 (Too short spinning time of sugar alcohol@LCST type thermosensitive polymer)

[0098] (1) A 60 wt% aqueous xylitol solution and an N,N-dimethylformamide solution of 12 wt% poly(N,N-dimethyl(methacryloylethyl)ammonium propane sulfonate) (critical transition temperature of 26 °C) were used as the core and shell spinning solutions respectively, and coaxial electrospinning was carried out using a high-voltage electrospinning machine. The electrospinning parameters were: needle gauge 22G, distance 15 cm, voltage 18 kV, temperature 25 - 30 °C, humidity 40 - 50% RH, spinning time 3 h, the flow rate of the shell spinning solution was 0.0016 mm / s, the flow rate of the core spinning solution was 0.0002 mm / s, and the layer thickness was 30 μm to obtain a sugar alcohol@UCST type thermosensitive polymer nanofiber membrane.

[0099] (2) Polyurethane (PU) was dissolved in a mixed solution of acetone and N,N-dimethylformamide (mass ratio 1:1) to prepare a 13 wt% shell spinning solution, and a 60 wt% aqueous xylitol solution was used as the core spinning solution. Using the nanofiber membrane obtained in (1) as the base membrane, coaxial electrospinning was carried out. The spinning parameters were needle 22G, distance 13 cm, voltage 10 kV, temperature 25 - 30 °C, humidity 40 - 50% RH, spinning time 20 min, the flow rate of the shell spinning solution was 0.0012 mm / s, the flow rate of the core spinning solution was 0.0002 mm / s, and the layer thickness was 15 μm to obtain a nanofiber membrane with a composite wetting gradient layer.

[0100] (3) Poly(acrylamide-co-acrylonitrile-co-N-hydroxymethylacrylamide) with a critical transition temperature of 26°C (the molar contents of the three monomers are 77%, 18% and 5%) is added to N,N-dimethylformamide to prepare a 15wt% shell spinning solution, a 60wt% xylitol aqueous solution is used as the core spinning solution, and the nanofiber membrane obtained in (2) is used as the base membrane. The core spinning solution and the shell solution are spun onto the PU side of the base membrane using an electrospinning device. The relevant electrospinning parameters are: needle specification 22G, distance 13cm, voltage 9kv, temperature 25-30°C, humidity 40-50%RH, spinning time 5min, shell spinning solution flow rate 0.001mm / s, core spinning solution flow rate 0.0002mm / s, layer thickness 1.6μm, and a nanofiber membrane is obtained.

[0101] The thickness of each layer has a key influence on the effective performance of the moisture-heat coordinated management function of the nanofiber membrane. The thickness of each layer is measured by a membrane thickness measuring instrument, and other related test methods are the same as above. The relevant data of each embodiment and comparative example are statistically analyzed, and the results are as follows:

[0102]

[0103] From the comparison of the data in the above table, it can be seen that: if the spinning time of the gradient layer is too long (Comparative Example 4), the sweat cannot overcome the gradient layer and is discharged, and the unidirectional perspiration performance is lost. If the spinning time of the outer layer of the nanofiber membrane is too long (Comparative Example 5), when the temperature drops, the outer layer is transformed into an overly thick hydrophobic layer, which reduces the air permeability and comfort of the material. If the spinning time of the outer layer of the nanofiber membrane is too short (Comparative Example 6), then under high temperature conditions, it is not possible to provide effective hydrophilicity for the discharge of sweat, and the hydrostatic pressure difference on both sides is small, resulting in inability to perspire in one direction. If the spinning time of the inner layer of the nanofiber membrane is too long (Comparative Example 7), the hydrophobic layer is too thick under high temperature conditions, causing sweat to be unable to overcome the hydrophobic force and be discharged. If the spinning time of the inner layer of the nanofiber membrane is too short (Comparative Example 8), the discharged sweat easily re-infiltrates the skin, causing the material to adhere to the skin and the sense of comfort to decrease.

[0104] Comparative Example 9 (the flow rate of the core layer spinning solution of each layer is relatively too small)

[0105] (1) The 60 wt% xylitol aqueous solution and the N,N-dimethylformamide solution of 12 wt% poly(N,N-dimethyl(methacryloylethyl)ammonium propane sulfonate) (critical transition temperature is 26 °C) were used as the core layer and shell layer spinning solutions respectively, and coaxial electrospinning was carried out using a high-voltage electrospinning machine. The electrospinning parameters were: needle gauge 22G, distance 15 cm, voltage 18 kv, temperature 25 - 30 °C, humidity 40 - 50%RH, spinning time 3 h, shell layer spinning solution flow rate 0.0016 mm / s, core layer spinning solution flow rate 0.0001 mm / s, layer thickness 30 μm, and a sugar alcohol@UCST type thermosensitive polymer nanofiber membrane was obtained.

[0106] (2) Polyurethane (PU) was dissolved in a mixed solution of acetone and N,N-dimethylformamide (mass ratio 1:1) to prepare a 13 wt% shell layer spinning solution, and a 60 wt% xylitol aqueous solution was used as the core layer spinning solution. Using the nanofiber membrane obtained in (1) as the base membrane, coaxial electrospinning was carried out. The electrospinning parameters were needle 22G, distance 13 cm, voltage 10 kv, temperature 25 - 30 °C, humidity 40 - 50%RH, spinning time 20 min, shell layer spinning solution flow rate 0.0012 mm / s, core layer spinning solution flow rate 0.0001 mm / s, layer thickness 15 μm, and a nanofiber membrane with a composite wetting gradient layer was obtained.

[0107] (3) Poly(acrylamide-co-acrylonitrile-co-N-hydroxymethylacrylamide) with a critical transition temperature of 26 °C (molar contents of the three monomers are 77%, 18% and 5%) was added to N,N-dimethylformamide to prepare a 15 wt% shell layer spinning solution, and a 60 wt% xylitol aqueous solution was used as the core layer spinning solution. Using the nanofiber membrane obtained in (2) as the base membrane, the core layer spinning solution and the shell layer solution were electrospun onto the PU side of the base membrane using an electrospinning device. The relevant electrospinning parameters were: needle gauge 22G, distance 13 cm, voltage 9 kv, temperature 25 - 30 °C, humidity 40 - 50%RH, spinning time 15 min, shell layer spinning solution flow rate 0.001 mm / s, core layer spinning solution flow rate 0.0001 mm / s, layer thickness 5 μm, and a nanofiber membrane was obtained.

[0108] Comparative Example 10 (the shell layer spinning solution flow rate of each layer is relatively too small)

[0109] (1) A 60 wt% aqueous xylitol solution and an N,N-dimethylformamide solution of 12 wt% poly(N,N-dimethyl(methacryloylethyl)ammonium propane sulfonate) (critical transition temperature: 26 °C) were used as the core layer and shell layer spinning solutions respectively, and coaxial electrospinning was carried out using a high-voltage electrospinning machine. The electrospinning parameters were as follows: needle gauge 22G, distance 15 cm, voltage 18 kV, temperature 25 - 30 °C, humidity 40 - 50% RH, spinning time 3 h, shell layer spinning solution flow rate 0.0005 mm / s, core layer spinning solution flow rate 0.0002 mm / s, layer thickness 30 μm, to obtain a sugar alcohol@UCST type thermosensitive polymer nanofiber membrane.

[0110] (2) Polyurethane (PU) was dissolved in a mixed solution of acetone and N,N-dimethylformamide (mass ratio 1:1) to prepare a 13 wt% shell layer spinning solution, and a 60 wt% aqueous xylitol solution was used as the core layer spinning solution. Using the nanofiber membrane obtained in (1) as the base membrane, coaxial electrospinning was carried out. The electrospinning parameters were: needle 22G, distance 13 cm, voltage 10 kV, temperature 25 - 30 °C, humidity 40 - 50% RH, spinning time 20 min, shell layer spinning solution flow rate 0.0004 mm / s, core layer spinning solution flow rate 0.0002 mm / s, layer thickness 15 μm, to obtain a nanofiber membrane with a composite wetting gradient layer.

[0111] (3) Poly(acrylamide-co-acrylonitrile-co-N-hydroxymethylacrylamide) with a critical transition temperature of 26 °C (molar contents of the three monomers were 77%, 18%, and 5%) was added to N,N-dimethylformamide to prepare a 15 wt% shell layer spinning solution, and a 60 wt% aqueous xylitol solution was used as the core layer spinning solution. Using the nanofiber membrane obtained in (2) as the base membrane, the core layer spinning solution and the shell layer solution were electrospun onto the PU side of the base membrane using an electrospinning device. The relevant electrospinning parameters were: needle gauge 22G, distance 13 cm, voltage 9 kV, temperature 25 - 30 °C, humidity 40 - 50% RH, spinning time 15 min, shell layer spinning solution flow rate 0.0004 mm / s, core layer spinning solution flow rate 0.0002 mm / s, layer thickness 5 μm, to obtain a nanofiber membrane.

[0112] The flow rate of the core-shell nanofiber spinning solution is crucial for the formation of core-shell structured nanofibers. The existence state of the sugar alcohol and the nanofiber structure were observed by SEM and TEM respectively, and other relevant testing methods were the same as above. The relevant data of each example and comparative example were statistically analyzed, and the results were as follows:

[0113]

[0114] It can be seen from the data comparison in the above table that by reasonably controlling the flow rates of the core layer and shell layer spinning solutions, nanofibers with a core-shell two-layer structure can be successfully prepared, and thus sugar alcohols can be successfully encapsulated in the core layer (Examples 1-3). Among them Figure 2 Figure Figure 2 is a TEM photograph of the sugar alcohol@PU layer in Example 1. It can be seen that there is a core-shell two-layer structure, and the sugar alcohol is successfully loaded in the core layer of the nanofibers. If the flow rate of the core layer spinning solution of each layer is too small (Comparative Example 9), then the amount of sugar alcohol loaded in the nanofibers is too small, and the degree of reduction under high temperature conditions is relatively low, and the cooling effect cannot be effectively exerted. If the flow rate of the shell layer spinning solution of each layer is too small (Comparative Example 10), then the sugar alcohol cannot be encapsulated, resulting in the exposure of the internal sugar alcohol (as Figure 5 shown), thereby reducing the water contact angle, and the sugar alcohol@LCST type nanofiber membrane that is hydrophobic at low temperature becomes hydrophilic, and the core-shell structure nanofibers cannot be formed.

[0115] In the present invention, the raw materials and equipment used, unless otherwise specified, are all common raw materials and equipment in the art; the methods used in the present invention, unless otherwise specified, are all conventional methods in the art.

[0116] The above are only preferred embodiments of the present invention, and do not impose any limitations on the present invention. Any simple modifications, changes, and equivalent transformations made to the above embodiments according to the technical essence of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A multi-layer nanofiber membrane for synergistic management of heat and humidity based on sugar alcohol, characterized in that: It comprises the following three layers which are compounded successively: A sugar alcohol@UCST type thermosensitive polymer nanofiber membrane layer. The sugar alcohol@UCST type thermosensitive polymer nanofibers have a core-shell structure, where the core layer is sugar alcohol and the shell layer is a UCST type thermosensitive polymer; A sugar alcohol@PU nanofiber membrane layer. The sugar alcohol@PU nanofibers have a core-shell structure, where the core layer is sugar alcohol and the shell layer is PU; A sugar alcohol@LCST type thermosensitive polymer nanofiber membrane layer for fitting with the skin. The sugar alcohol@LCST type thermosensitive polymer nanofibers have a core-shell structure, where the core layer is sugar alcohol and the shell layer is an LCST type thermosensitive polymer; The UCST type thermosensitive polymer is poly(N,N-dimethyl(methacryloylethyl)ammonium propane sulfonate), and the critical transition temperature is 26-27°C; The LCST type thermosensitive polymer is poly(acrylamide-co-acrylonitrile-co-N-hydroxymethylacrylamide), and the critical transition temperature is 26-27°C.

2. The multi-layer nanofiber membrane according to claim 1, wherein: The sugar alcohol is selected from sorbitol and xylitol.

3. The multi-layer nanofiber membrane according to claim 1, wherein: The thickness of the sugar alcohol@UCST type thermosensitive polymer nanofiber membrane layer is 30-60 µm; The thickness of the sugar alcohol@PU nanofiber membrane layer is 10-20 µm; The thickness of the sugar alcohol@LCST type thermosensitive polymer nanofiber membrane layer is 5-10 µm.

4. A method for preparing a multi-layer nanofiber membrane for synergistic management of heat and humidity based on sugar alcohol as described in any one of claims 1-3, characterized in that It includes the following steps: (1) Using a sugar alcohol solution as the core layer spinning solution and a 10-20 wt% UCST type thermosensitive polymer solution as the shell layer spinning solution, performing coaxial electrospinning with a core-shell layer spinning flow rate ratio of 1:(7-9) to obtain a sugar alcohol@UCST type thermosensitive polymer nanofiber membrane layer; (2) Using a sugar alcohol solution as the core layer spinning solution and a 10-15 wt% polyurethane solution as the shell layer spinning solution, performing coaxial electrospinning on the surface of the sugar alcohol@UCST type thermosensitive polymer nanofiber membrane layer to form a sugar alcohol@PU nanofiber membrane layer, with a core-shell layer spinning flow rate ratio of 1:(5-8), to obtain a nanofiber membrane with a composite wetting gradient layer; (3) Using a sugar alcohol solution as the core layer spinning solution and a 10-20 wt% LCST type thermosensitive polymer solution as the shell layer spinning solution, performing coaxial electrospinning on the surface of the sugar alcohol@PU nanofiber membrane layer to form a sugar alcohol@LCST type thermosensitive polymer nanofiber membrane layer, with a core-shell layer spinning flow rate ratio of 1:(4-9), to obtain a sugar alcohol-based multi-layer nanofiber membrane for synergistic management of heat and humidity.

5. The preparation method according to claim 4, characterized in that: In steps (1)-(3), the concentration of the sugar alcohol solution is 60-70 wt%.

6. The preparation method according to claim 5, characterized in that: In steps (1)-(3), the solvent of the sugar alcohol solution is water.

7. The preparation method according to claim 4, wherein: In step (1), the solvent of the UCST type thermosensitive polymer solution is N,N-dimethylformamide; In step (2), the solvent of the polyurethane solution is a mixed solution of acetone and N,N-dimethylformamide with a mass ratio of 1:(1-2); In step (3), the solvent of the LCST type thermosensitive polymer solution is N,N-dimethylformamide.

8. The preparation method according to any one of claims 4-7, characterized in that: In steps (1) to (3), the flow rate of the core layer spinning solution propulsion pump is 0.0002 - 0.0004 mm / s.

9. The preparation method according to claim 8, characterized in that: In step (1), the spinning time is 3 - 5 h; In step (2), the spinning time is 10 - 30 min; In step (3), the spinning time is 10 - 30 min.

10. The preparation method according to claim 9, characterized in that: In step (1), the coaxial electrospinning parameters are: needle size 20 - 22G, distance 15 - 20 cm, voltage 18 - 28 kv, temperature 25 - 30 °C, humidity 40 - 50%RH; In step (2), the coaxial electrospinning parameters are: needle size 20 - 22G, distance 13 - 16 cm, voltage 9 - 11 kv, temperature 25 - 30 °C, humidity 40 - 50%RH; In step (3), the coaxial electrospinning parameters are: needle size 20 - 22G, distance 15 - 20 cm, voltage 10 - 14 kv, temperature 25 - 30 °C, humidity 40 - 50%RH.

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