Preparation method and application of a self-adhesive moisture-absorbing and cooling composite nanofiber membrane loaded with sugar alcohol

Abstract

The present invention relates to the field of functional polymer materials, and discloses a preparation method and application of a self-adhesive moisture-absorbing and temperature-reducing composite nanofiber membrane loaded with sugar alcohol. The preparation method includes: (1) using a sugar alcohol solution and a PVA / DA solution as the core layer and shell layer spinning solutions respectively, and performing coaxial electrospinning to obtain a sugar alcohol@PVA / DA composite nanofiber membrane; (2) crosslinking the composite nanofiber membrane to prepare a self-adhesive moisture-absorbing and temperature-reducing composite nanofiber membrane loaded with sugar alcohol. In the present invention, sugar alcohol with excellent heat absorption by dissolution is used as the core layer, and PVA / DA with self-adhesive properties is used as the shell layer, and a stable composite nanofiber membrane is prepared through coaxial electrospinning and crosslinking treatment. The fiber membrane can absorb heat by contacting skin sweat at high temperatures to achieve the effect of moisture absorption and temperature reduction, and at the same time has good biological safety and skin adhesiveness, and is suitable for the preparation of human skin local wet-heat management products.

Description

Technical Field

[0001] The present invention relates to the field of functional polymer materials, and particularly to a preparation method and application of a self-adhesive moisture-absorbing and cooling composite nanofiber membrane loaded with sugar alcohols. Background Art

[0002] Hot and humid weather can bring discomfort to people and even cause serious heat damage to the human body. Therefore, thermal management materials with the function of cooling the body surface have received extensive attention. At present, some functional thermal management materials that can achieve cooling can be classified into the following types: phase change materials, moisture-conducting types, heat-conducting types, and light radiation regulation types, etc.

[0003] Chinese Patent CN112252019 discloses a sweat-cooling fabric, in which a superhydrophilic structure is formed on the unilateral 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 method utilizes the difference in wetting gradient to enable sweat to penetrate to the hydrophilic surface of the fabric and evaporate on the hydrophilic surface of the fabric to take away heat. Chinese Patent CN110105749 discloses a polyamide cooling material, and the preparation method includes the following steps: adding a polyamide resin, a nucleating agent, and an antioxidant into an extruder for mixing and granulating to obtain a prefabricated material; adding the prefabricated material into the extruder, and then injecting a pore-forming agent, and extruding and granulating to obtain a carrier material; after mixing an organic peroxide and a solubilizer, uniformly dispersing and absorbing them in the carrier material to obtain a polyamide cooling material with good sweat-cooling function. However, the cooling performance of the above materials depends on their multi-layer composite structure and special pore structure, the material preparation is cumbersome, and the cooling effect is limited.

[0004] Chinese Patent CN111155332 discloses a radiation cooling passive cooling fabric and its preparation method, which sequentially includes an infrared high-emission top layer, a sunlight low-absorption fabric layer, and a sunlight high-reflection bottom layer from top to bottom. Through the coordinated cooperation of the three layers, the fabric of this invention can achieve the effects of high infrared emissivity and strong sunlight reflectivity during the day, improving the radiation cooling performance of the material during the day. However, this material can only show its only cooling effect during the day, with limited use. Chinese Patent CN101451307 discloses a long-lasting cool cooling composite powder, fiber, and its manufacturing method. Using a nano-high-porosity mesoporous material as the base material, a phase change material is dispersed and filled into the pores of the base material, and then the base material with the phase change material is micro-fine processed and mixed with a porous high-specific heat material that adsorbs or contains water vapor in the pores to obtain the cooling composite powder. The cooling composite powder is added to various fibers in proportion to form cooling fibers. When the body heat of a human is conducted to the cooling fibers, the micro-fine phase change material on the surface of the cooling fibers can adsorb the body heat and undergo a phase change to lower the temperature. Chinese Patent CN108560252 discloses an anti-scratch radiation cooling fiber, including a fiber body, a silver-plated layer is provided on the surface of the fiber body, and a radiation cooling protective layer is provided on the surface of the silver-plated layer. The radiation cooling protective layer is a transparent film layer composed of inorganic non-metallic microspheres and a polymer matrix. The technical solution of this invention can passively radiate infrared rays of 8-13μm externally to produce a cooling function. Chinese Patent CN115262217 discloses a process method for improving the heat conduction and cooling performance of fabrics. This method is to compound graphene with an aqueous polyurethane solution and form a special heat conduction film on the fabric surface through a solution grafting method. This invention uses aqueous polyurethane to firmly attach graphene to the surface of the fiber fabric and forms a graphene network for heat conduction and cooling on the fabric surface, which can improve the temperature conduction efficiency. However, the cooling effects of the above materials rely on the compounding of powder materials with radiation cooling performance or good heat conductivity and fibers. The preparation and application environments are relatively complex, and there are problems of biological safety, making it difficult to be directly applied to local cooling of human skin. Therefore, it is very meaningful to develop a thermal management material that can be directly used for local cooling of human skin.

[0005] Sugar alcohols have excellent endothermic dissolution properties. When absorbing moisture, they can carry away a large amount of heat and have excellent heat dissipation performance. Moreover, sugar alcohols are substances with good biocompatibility and have great research potential for their use in local skin heat management. However, how to prepare an ideal and effective thermal management composite material using them is a challenging problem. So far, due to the excellent water solubility of sugar alcohols, no one has reported directly loading sugar alcohols inside fibers in the form of a core-shell fiber structure to achieve the function of moisture absorption and heat dissipation. Through thinking about the preparation of phase change materials, we found that the core-shell electrospinning technology can be used to load small molecule sugar alcohols inside nanofibers, enabling the composite fibers to absorb skin sweat, allowing sweat molecules to enter the fibers and dissolve the sugar alcohols, thereby achieving endothermic heat dissipation, reducing local skin heat stress, and improving thermal comfort. The combination of sugar alcohols and fibers endows the material with moisture absorption - heat dissipation properties, contact heat dissipation, simple preparation, and good affinity for the skin, which has practical significance for local wet - heat management of the human body. Summary of the Invention

[0006] To solve the above technical problems, the present invention provides a method for preparing a self - adhesive moisture - absorbing and heat - dissipating composite nanofiber membrane loaded with sugar alcohol and its application. The present invention uses sugar alcohol with excellent endothermic dissolution and polyvinyl alcohol / dopamine hydrochloride (PVA / DA) as the core layer and shell layer respectively for coaxial electrospinning to prepare a composite nanofiber membrane, and then cross - links the shell - layer polyvinyl alcohol nanofibers through glutaraldehyde treatment to improve the water stability of the material. This composite nanofiber membrane can absorb heat by contacting skin sweat in hot weather to achieve the effect of moisture absorption and heat dissipation. At the same time, it has good biological safety and good adhesion to the skin, and is suitable for the preparation of human skin local wet - heat management products.

[0007] The specific technical solution of the present invention is as follows:

[0008] In the first aspect, the present invention provides a method for preparing a self - adhesive moisture - absorbing and heat - dissipating composite nanofiber membrane loaded with sugar alcohol, comprising the following steps:

[0009] (1) Dissolve sugar alcohol, polyvinyl alcohol, and dopamine hydrochloride in water respectively; add the obtained dopamine hydrochloride solution to the obtained polyvinyl alcohol solution; use the obtained sugar alcohol solution and the obtained polyvinyl alcohol / dopamine hydrochloride solution as the core - layer spinning solution and the shell - layer spinning solution respectively, and perform coaxial electrospinning to obtain a sugar alcohol@polyvinyl alcohol / dopamine hydrochloride composite nanofiber membrane.

[0010] (2) The composite nanofiber membrane obtained in step (1), an acid catalyst, and a desiccant are placed together in a sealed container with an aqueous glutaraldehyde solution at the bottom. The composite nanofiber membrane, the acid catalyst, and the desiccant are located above the aqueous glutaraldehyde solution. After the surface of the composite nanofiber membrane comes into contact with the volatilized glutaraldehyde, a cross-linking reaction occurs to obtain a self-adhesive moisture-absorbing and temperature-reducing composite nanofiber membrane loaded with sugar alcohol.

[0011] As described in the background art section of this application, for human body local cooling materials, the existing preparation methods make the material preparation and application environment complex and the skin affinity poor. Sugar alcohol has a low cost and particularly good moisture-absorbing, temperature-reducing, and biocompatible properties. However, how to use it to prepare a human skin local wet-heat management material is a challenging problem.

[0012] Therefore, in the present invention, a core-shell structured composite nanofiber material can be obtained by coaxial electrospinning of sugar alcohol (core) and polyvinyl alcohol / dopamine hydrochloride (shell). The sugar alcohol loaded in the inner layer of the nanofiber can endow the material with the characteristics of moisture absorption, temperature reduction, and skin-friendly. However, we further found in the previous experiments that since the sugar alcohol has good fluidity after being absorbed and dissolved in water, and the polyvinyl alcohol in the shell layer is also a water-soluble substance, when the nanofiber absorbs moisture (such as sweat), not only is it easy for the sugar alcohol to leak due to the damage of the shell layer structure, but also the strength of the composite nanofiber membrane is reduced. Therefore, in the present invention, the composite nanofiber membrane is cross-linked with glutaraldehyde under the action of an acid catalyst, thereby improving the water stability of the sugar alcohol@polyvinyl alcohol composite nanofiber membrane. The specific principle of this process is: the composite nanofiber membrane, the acid catalyst, and the desiccant are located above the aqueous glutaraldehyde solution. Both glutaraldehyde and concentrated hydrochloric acid are volatile substances. The volatilized glutaraldehyde and concentrated hydrochloric acid come into contact with the surface of the composite nanofiber membrane. In an acidic environment, H + catalyzes the condensation reaction between the hydroxyl group of sugar alcohol and the aldehyde group of glutaraldehyde, thereby forming a cross-link. The desiccant is used to absorb the moisture in the air and the moisture volatilized from the solution to prevent the nano-composite fiber membrane from absorbing moisture and dissolving.

[0013] On the other hand, conventional nanofiber membranes are often difficult to adhere to sweating skin and are prone to falling off. However, the shell layer of the nanofiber in the present invention is loaded with dopamine. The catechol structure in dopamine can react with the free sulfhydryl groups in the skin surface proteins to form chemical bonds, endowing the moisture-absorbing and temperature-reducing fiber material with the ability to spontaneously and stably adhere to the skin surface, and improving the practical value of the material.

[0014] Preferably, in step (1), the polyvinyl alcohol is heated to ≥95 °C and dissolved after adding water.

[0015] Preferably, in step (1), the sugar alcohol is sorbitol and / or xylitol.

[0016] Sugar alcohols belong to small-molecule compounds. Through preliminary experiments, the present invention found that most small-molecule compounds are not suitable for being processed into nanofibers alone by electrospinning. The reason is that the viscosity of small-molecule compound solutions is relatively low and the fluidity is too high. Even when coaxial electrospinning is used, it is difficult for the shell polymer to completely wrap the small-molecule compound without leakage during the electrospinning process. Finally, through investigation and screening, the present invention found that the viscosities of the above-mentioned several types of sugar alcohols are appropriate and, due to the presence of a large number of hydroxyl groups, they can form hydrogen bond adsorption with the hydroxyl groups of the macromolecule polyvinyl alcohol. Therefore, the core-shell structure nanofibers with sugar alcohols coated can be successfully prepared by electrospinning with the help of the electric field force traction of the shell layer.

[0017] Preferably, in step (1), the concentration of the sugar alcohol solution is 60-70 wt%; in the polyvinyl alcohol / dopamine hydrochloride solution, the concentration of the polyvinyl alcohol solution is 8-12 wt%, and the content of dopamine hydrochloride is 3-5 wt%.

[0018] Preferably, in step (1), the parameters of the coaxial electrospinning are: the flow rate ratio of the core-shell layer is 1:8-10, the needle size 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.

[0019] The present invention found through experiments that the flow rate ratio of the core-shell layer of the coaxial electrospinning composite nanofiber material is extremely important. If the flow rate ratio of the core-shell layer of the nanofibers is relatively high, the polyvinyl alcohol fiber shell cannot completely wrap the small-molecule sugar alcohol, and the sugar alcohol solution is likely to leak; if the flow rate ratio of the core-shell layer of the nanofibers is relatively low, the content of the core layer sugar alcohol is relatively low, and the moisture absorption and cooling effect is not obvious.

[0020] Preferably, in step (1), the electrospinning time of the coaxial electrospinning is 4-12 h, and the flow rate of the core layer spinning solution propulsion pump is 0.0002-0.0004 mm / s.

[0021] Preferably, in step (1), the diameter of the composite nanofibers in the sugar alcohol@polyvinyl alcohol / dopamine hydrochloride composite nanofiber membrane is 400-1000 nm; the thickness of the sugar alcohol@polyvinyl alcohol / dopamine hydrochloride composite nanofiber membrane is 0.2-0.4 mm.

[0022] Preferably, in step (2), the crosslinking temperature is 25-30 °C and the time is 5-11 h.

[0023] Preferably, in step (2), the acid catalyst is concentrated hydrochloric acid; the desiccant is anhydrous calcium chloride.

[0024] Preferably, in step (2), the dosage ratio of the acid catalyst to the composite nanofiber membrane is 8 - 12 mL / 5 g; the dosage ratio of the desiccant to the composite nanofiber membrane is 8 - 12 g / 5 g; the concentration of the glutaraldehyde aqueous solution is 25 - 50 wt%, and the dosage ratio of the glutaraldehyde aqueous solution to the composite nanofiber membrane is 8 - 12 mL / 5 g.

[0025] Second, the present invention provides the application of the above-mentioned self-adhesive moisture-absorbing and cooling composite nanofiber membrane loaded with sugar alcohol as a raw material in the preparation of human skin local wet-heat management products.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] (1) The present invention ingeniously utilizes the endothermic property of sugar alcohol dissolution. Through coaxial electrospinning, sugar alcohol small molecules are encapsulated in a polyvinyl alcohol shell, and then crosslinked with glutaraldehyde to obtain a sugar alcohol@polyvinyl alcohol / dopamine hydrochloride (PVA / DA) composite nanofiber membrane with good stability. In a heat-stimulated environment, this material can be used as a contact cooling material. When attached to the skin surface, the sugar alcohol contacts the surface sweat and absorbs heat by dissolution, achieving the effect of local cooling of the human body.

[0028] (2) The composite nanofiber membrane has good biosafety, and the surface is loaded with dopamine, so it has good adhesion to the skin and is suitable for the preparation of human skin local wet-heat management products such as antipyretic patches and cooling dressings. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the device when the crosslinking treatment is carried out in step (2) of this application;

[0030] Figure 2 It is a microscopic morphology image of the sugar alcohol@PVA / DA composite nanofiber membrane of Example 1;

[0031] Figure 3 It is a thermal imaging comparison diagram of the temperature reduction effect before and after moisture absorption of the sugar alcohol@PVA / DA composite nanofiber membrane of Example 1 and the PVA / DA composite fiber membrane of Comparative Example 1;

[0032] Figure 4 It is an adhesion performance diagram of the sugar alcohol@PVA / DA composite nanofiber membrane (sugar alcohol@PVA / DA) of Example 1 and the sugar alcohol@PVA composite nanofiber membrane (sugar alcohol@PVA) of Comparative Example 2;

[0033] Figure 5 It is an SEM image of the sugar alcohol@PVA / DA composite nanofiber membrane prepared by Comparative Example 3 at different core-shell flow rate ratios. DETAILED DESCRIPTION OF THE INVENTION

[0034] The present invention will be further described below in conjunction with embodiments.

[0035] Sorbitol and xylitol are both food-grade, polyvinyl alcohol is of type 224, and the purity of dopamine hydrochloride is 98%.

[0036] General Embodiment

[0037] A method for preparing a self-adhesive moisture-absorbing and temperature-reducing composite nanofiber membrane loaded with sugar alcohols, comprising the following steps:

[0038] (1) Dissolve sugar alcohols (sorbitol and / or xylitol), polyvinyl alcohol, and dopamine hydrochloride in water respectively (when adding polyvinyl alcohol to water, it needs to be heated to ≥95°C); add the obtained dopamine hydrochloride solution (concentration 0.03 - 0.05 g / mL) to the obtained polyvinyl alcohol solution; use the obtained sugar alcohol solution (concentration 40 - 70 wt%) and the obtained polyvinyl alcohol / dopamine hydrochloride solution (PVA content 8 - 12 wt%, DA content 3 - 5 wt%) as the core layer spinning solution and the shell layer spinning solution respectively, and perform coaxial electrospinning. The parameters are: the flow rate of the core layer spinning solution propulsion pump is 0.0002 - 0.0004 mm / s, the flow rate ratio of the core-shell layer spinning is 1:8 - 10, the needle head specification is 20 - 22G, the distance is 15 - 20 cm, the voltage is 18 - 28 kv, the temperature is 25 - 30°C, the humidity is 40 - 50%RH, and the spinning time is 4 - 6 h. After spinning, a sugar alcohol@polyvinyl alcohol / dopamine hydrochloride composite nanofiber membrane is obtained (the diameter of a single composite nanofiber is 400 - 1000 nm, and the thickness of the composite nanofiber membrane is 0.2 - 0.4 mm).

[0039] (2) As Figure 1 shown, place the composite nanofiber membrane obtained in step (1), an acid catalyst (35 - 40 wt% concentrated hydrochloric acid), a desiccant (anhydrous calcium chloride), and a glutaraldehyde aqueous solution (25 - 50 wt%) in a sealed container with the glutaraldehyde aqueous solution at the bottom. The composite nanofiber membrane, the acid catalyst, and the desiccant are located above the glutaraldehyde aqueous solution. The glutaraldehyde volatilized at 25 - 30°C contacts the surface of the composite nanofiber membrane to undergo a cross-linking reaction. After reacting for 5 - 12 h, a self-adhesive moisture-absorbing and temperature-reducing composite nanofiber membrane loaded with sugar alcohols is prepared. Among them, the dosage ratio of the acid catalyst to the composite nanofiber membrane is 8 - 12 mL / 5 g; the dosage ratio of the desiccant to the composite nanofiber membrane is 8 - 12 g / 5 g; the dosage ratio of the glutaraldehyde aqueous solution (25 - 50 wt%) to the composite nanofiber membrane is 8 - 12 mL / 5 g.

[0040] Example 1

[0041] 1) Dissolve xylitol, PVA, and DA in deionized water respectively. Among them, polyvinyl alcohol needs to be in a water bath at 95 °C. Mix the PVA solution and the DA solution. Finally, obtain a PVA / DA solution containing 10 wt% PVA and 5 wt% DA and a 60 wt% xylitol solution. Then, use the sugar alcohol solution and the PVA / DA solution as the core layer and the shell layer respectively, and perform coaxial electrospinning with a high-voltage electrospinning machine for 5 hours to obtain a (400 - 500 nm in diameter, 0.2 mm in thickness) sugar alcohol@PVA / DA composite nanofiber membrane. The electrospinning parameters are as follows: core-shell flow rate ratio: 0.0003 mm / s: 0.0024 mm / s, needle: 22G, distance: 15 cm, voltage: 25 kv, temperature: 25 - 30 °C, humidity: 40 - 50% RH.

[0042] 2) Take 5 g of the composite nanofiber membrane prepared in step (1), 10 mL of 37% concentrated hydrochloric acid, and 10 g of anhydrous calcium chloride and put them together into a sealed glass container containing 10 mL of 25% glutaraldehyde aqueous solution. Among them, the glutaraldehyde aqueous solution is placed at the bottom layer of the container, and the composite nanofiber membrane, anhydrous calcium chloride, and concentrated hydrochloric acid (placed in an open petri dish) are located at the upper layer. The volatilized glutaraldehyde and concentrated hydrochloric acid crosslink with the surface of the composite nanofiber membrane to improve the water stability of the composite nanofiber. The crosslinking times are 5 h, 7 h, 9 h, and 11 h respectively, and the environmental temperature is 25 - 30 °C.

[0043] Example 2

[0044] 1) Dissolve sorbitol, PVA, and DA in deionized water respectively. Among them, polyvinyl alcohol needs to be in a water bath at 95 °C. Mix the PVA solution and the DA solution. Finally, obtain a PVA / DA solution containing 10 wt% PVA and 5 wt% DA and a 70 wt% sorbitol aqueous solution. Then, use the sorbitol solution and the PVA / DA solution as the core layer and the shell layer respectively, and perform coaxial electrospinning with a high-voltage electrospinning machine for 5 hours to obtain a (400 - 500 nm in diameter, 0.2 mm in thickness) sorbitol@PVA / DA composite nanofiber membrane. The electrospinning parameters are as follows: core-shell flow rate ratio: 0.0003 mm / s: 0.0024 mm / s, needle: 22G, distance: 15 cm, voltage: 22 kv, temperature: 25 - 30 °C, humidity: 40 - 50% RH.

[0045] 2) Take 5 g of the composite nanofiber membrane prepared in step (1), 10 mL of 37% concentrated hydrochloric acid, and 10 g of anhydrous calcium chloride, and put them together into a sealed glass container containing 10 mL of 25% glutaraldehyde aqueous solution. The glutaraldehyde aqueous solution is placed at the bottom layer of the container, while the composite nanofiber membrane, anhydrous calcium chloride, and concentrated hydrochloric acid (placed in an open petri dish) are located at the upper layer. The volatilized glutaraldehyde and concentrated hydrochloric acid crosslink with the surface of the composite nanofiber membrane to improve the water stability of the composite nanofiber. The crosslinking times are 5 h, 7 h, 9 h, and 11 h respectively, and the environmental temperature is 25 - 30 °C.

[0046] Comparative Example 1 (without adding sugar alcohol)

[0047] 1) Dissolve polyvinyl alcohol and dopamine hydrochloride separately in deionized water (in a 95 °C water bath), and mix them to obtain a PVA / DA solution containing 10 wt% PVA and 5 wt% DA. Then, use a high-voltage electrospinning machine for electrospinning for 5 h to obtain a PVA / DA nanofiber membrane (with a diameter of 400 - 500 nm and a thickness of 0.2 mm). The electrospinning parameters are: flow rate: 0.0024 mm / s, needle: 22G, distance: 15 cm, voltage: 18 kv, temperature: 25 - 30 °C, humidity: 40 - 50% RH.

[0048] 2) Take 5 g of the polyvinyl alcohol-dopamine hydrochloride nanofiber membrane prepared in step (1), 10 mL of 37% concentrated hydrochloric acid, and 10 g of anhydrous calcium chloride, and put them together into a sealed glass container. The glutaraldehyde aqueous solution is placed at the bottom layer of the container, while the composite nanofiber membrane, anhydrous calcium chloride, and concentrated hydrochloric acid (placed in an open petri dish) are located at the upper layer. The volatilized glutaraldehyde and concentrated hydrochloric acid crosslink with the surface of the composite nanofiber membrane to improve the water stability of the nanofiber membrane. The crosslinking times are 5 h, 7 h, 9 h, and 11 h respectively, and the environmental temperature is 25 - 30 °C.

[0049] Comparative Example 2 (without adding DA)

[0050] 1) Dissolve xylitol polyvinyl alcohol separately in deionized water, where polyvinyl alcohol needs a 95 °C water bath, to obtain a 60 wt% xylitol aqueous solution and a 10 wt% polyvinyl alcohol solution. Then, use the sugar alcohol solution and the polyvinyl alcohol solution as the core layer and the shell layer respectively, and use a high-voltage electrospinning machine for coaxial electrospinning to obtain a sugar alcohol@polyvinyl alcohol composite nanofiber membrane (membrane thickness is about 0.2 mm, fiber diameter is about 400 - 500 nm). The electrospinning parameters are: core-shell flow rate ratio: 0.0003 mm / s: 0.0024 mm / s, needle: 22G, distance: 15 cm, voltage: 25 kv, temperature: 25 - 30 °C, humidity: 40 - 50% RH.

[0051] 2) Take 5 g of the composite nanofiber membrane prepared in step (1), 10 mL of 37% concentrated hydrochloric acid, and 10 g of anhydrous calcium chloride, and place them together in a sealed glass container containing 10 mL of 25% glutaraldehyde aqueous solution. The glutaraldehyde aqueous solution is placed at the bottom layer of the container, while the composite nanofiber membrane, anhydrous calcium chloride, and concentrated hydrochloric acid (placed in an open petri dish) are located at the upper layer. The volatilized glutaraldehyde and concentrated hydrochloric acid crosslink with the surface of the composite nanofiber membrane to improve the water stability of the composite nanofiber. The crosslinking times are 5 h, 7 h, 9 h, and 11 h respectively, and the environmental temperature is 25 - 30 °C.

[0052] Comparative Example 3 (different core-shell flow rate ratios)

[0053] 1) Dissolve sorbitol, xylitol, PVA, and DA in deionized water respectively. Among them, polyvinyl alcohol needs to be in a water bath at 95 °C. Mix the PVA solution and the DA solution. Finally, obtain a PVA / DA solution containing 10 wt% PVA, 5 wt% DA, a 70 wt% sorbitol solution, and a 60 wt% xylitol solution. Then, use the two sugar alcohol solutions and the PVA / DA solution as the core layer and the shell layer respectively, and perform coaxial electrospinning using a high-voltage electrospinning machine to obtain a sorbitol@PVA / DA composite nanofiber membrane and a xylitol@PVA / DA composite nanofiber membrane. Among them, the membrane thickness is about 0.2 mm, and the fiber diameter is about 400 - 500 nm. The electrospinning parameters are: different core-shell flow rate ratios: 0.0003 mm / s∶0.0009 mm / s, 0.0003 mm / s∶0.0015 mm / s, 0.0003 mm / s∶0.0021 mm / s, needle: 22G, distance: 15 cm, voltage: 22 kv, temperature: 25 - 30 °C, humidity: 40 - 50% RH.

[0054] 2) Take 5 g of each composite nanofiber membrane prepared in step (1) respectively, and place them together with 10 mL of 37% concentrated hydrochloric acid and 10 g of anhydrous calcium chloride in a sealed glass container containing 10 mL of 25% glutaraldehyde aqueous solution. The glutaraldehyde aqueous solution is placed at the bottom layer of the container, while the composite nanofiber membrane, anhydrous calcium chloride, and concentrated hydrochloric acid (placed in an open petri dish) are located at the upper layer. The volatilized glutaraldehyde and concentrated hydrochloric acid crosslink with the surface of the nanofiber membrane to improve the water stability of the composite nanofiber. The crosslinking times are 5 h, 7 h, 9 h, and 11 h respectively, and the environmental temperature is 25 - 30 °C.

[0055] Comparative Example 4 (uncrosslinked)

[0056] 1) Dissolve xylitol, PVA, and DA separately in deionized water. Among them, polyvinyl alcohol requires a water bath at 95 °C. Mix the PVA solution and the DA solution. Finally, obtain a PVA / DA solution containing 10 wt% PVA and 5 wt% DA, as well as a 60 wt% xylitol aqueous solution. Then, use the xylitol solution and the PVA / DA solution as the core layer and the shell layer respectively, and perform coaxial electrospinning with a high-voltage electrospinning machine to obtain a sugar alcohol@PVA / DA composite nanofiber membrane (with a thickness of about 0.2 mm and a diameter of about 400 - 500 nm). The electrospinning parameters are: core-shell flow rate ratio: 0.0003 mm / s∶0.0024 mm / s, needle: 22G, distance: 15 cm, voltage: 25 kv, temperature: 25 - 30 °C, humidity: 40 - 50% RH.

[0057] Comparative Example 5 (different concentrations of sugar alcohol aqueous solutions)

[0058] 1) Dissolve different masses of xylitol, PVA, and DA separately in deionized water. Among them, polyvinyl alcohol requires a water bath at 95 °C. Mix the PVA solution and the DA solution. Finally, obtain a PVA / DA solution containing 10 wt% PVA and 5 wt% DA, as well as different sugar alcohol concentration solutions: 40 wt% xylitol aqueous solution, 20 wt% xylitol aqueous solution. Then, use different sugar alcohol solutions and the PVA / DA solution as the core layer and the shell layer respectively, and perform coaxial electrospinning with a high-voltage electrospinning machine for 5 h to obtain different sugar alcohol@PVA / DA composite nanofiber membranes (with a thickness of about 0.2 mm and a diameter of about 400 - 500 nm). The electrospinning parameters are: core-shell flow rate ratio: 0.0003 mm / s∶0.0024 mm / s, needle: 22G, distance: 15 cm, voltage: 25 kv, temperature: 25 - 30 °C, humidity: 40 - 50% RH.

[0059] 2) Take 5 g of the different composite nanofiber membranes prepared in step (1) respectively, and put them together with 10 mL of concentrated hydrochloric acid and 10 g of anhydrous calcium chloride into a sealed glass container containing 10 mL of 25% glutaraldehyde aqueous solution. Among them, the glutaraldehyde aqueous solution is placed at the bottom layer of the container, and the composite nanofiber membranes, anhydrous calcium chloride, and concentrated hydrochloric acid (placed in an open petri dish) are located on the upper layer. The volatilized glutaraldehyde and concentrated hydrochloric acid crosslink on the surface of the fiber membrane to improve the water stability of the composite nanofiber membrane. The crosslinking times are 5 h, 7 h, 9 h, and 11 h respectively, and the environmental temperature is 25 - 30 °C.

[0060] Performance testing

[0061] Test the nanofiber membranes in each example and comparative example. Among them, the surface morphology of the fibers is characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The crosslinking effect (water stability), adhesion performance, and moisture absorption and cooling performance are characterized as follows:

[0062] Crosslinking effect test: Cut the nanofiber membranes before and after crosslinking into blocks, then drop a drop of water on the nanofiber membranes, and observe whether the nanofiber membranes dissolve after encountering water.

[0063] Adhesion performance test: Similar to the adhesion principle of hydrogels, under wet conditions, the phenolic hydroxyl groups of the DA component and the hydroxyl groups in water can cooperate to form bonding keys with the sulfhydryl groups in skin proteins. Specific test method: Make the wetted skin contact with the nanofiber membrane, and observe the falling time of the nanofiber membrane to judge the adhesion performance of the membrane material to the skin. If the adhesion time is greater than 2 minutes, it is judged that the nanofiber membrane has adhesion performance on the skin surface.

[0064] Moisture absorption and cooling performance test: The moisture absorption and cooling effect of the nanofiber membrane is carried out in a space with a relatively stable ambient temperature. First, wet 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. In addition, an infrared thermal imager is used to record the temperature of the nanofiber membrane before and after moisture absorption.

[0065] The test results of each performance are as follows:

[0066]

[0067]

[0068] It can be seen from the above results that:

[0069] Compared with Comparative Example 1, in Examples 1-2, sugar alcohol small molecules with endothermic dissolution performance were encapsulated inside polyvinyl alcohol nanofibers by the coaxial electrospinning method. It can be seen from the test data of the moisture absorption and cooling performance that the surface temperature of the sugar alcohol@PVA / DA composite nanofiber membrane can be reduced by about 2-3 °C after moisture absorption in the thermocouple temperature sensor, while the moisture absorption and cooling effect of the composite nanofiber membrane without encapsulated sugar alcohol (Comparative Example 1) is only about 0.6 °C. At the same time, in the thermal imager, the sugar alcohol@PVA / DA group (Example 1) has a lower cooling effect compared with the PVA / DA group without sugar alcohol (Comparative Example 1) (about 2 °C lower, Figure 2 )

[0070] Compared with Comparative Example 2, the DA component was introduced into the composite nanofiber membranes of Examples 1-2. Through the comparison of the adhesion data, it can be seen that the introduction of DA makes the composite nanofiber membrane have a certain adhesion effect on the skin, improving the usability of the material.

[0071] From the comparison between Examples 1-2 and Comparative Example 3, it can be seen that the spinnability of the shell solution is a decisive factor for the formation of core-shell structured nanofibers. As the flow rate of the shell polymer solution increases (the core-shell flow rate ratios are 1:3, 1:5, 1:7, and 1:8 respectively), the composite nanofiber membrane of Example 1 (1:8) has a relatively uniform fiber morphology ( Figure 1 ). In Comparative Example 3, at different core-shell flow rate ratios, as shown in Figure 4 , the obtained nanofiber morphology has an uneven surface and exposed particles (1:3 and 1:5), or the surface of the nanofibers is not smooth (1:7). This is because the sugar alcohol is not well coated by the polyvinyl alcohol nanofibers, and the preparation of the core-shell structured nanofiber membrane fails. Therefore, no subsequent cooling data tests were conducted on it.

[0072] When comparing Examples 1-2 with Comparative Example 4, the composite nanofiber membranes of Examples 1-2 were treated with glutaraldehyde cross-linking. Compared with the non-cross-linked fiber membranes of Comparative Example 4, the water stability of the cross-linked composite nanofiber membranes was significantly improved. Since its water stability was unqualified, no subsequent adhesion and cooling tests were conducted on it.

[0073] When comparing Examples 1-2 with Comparative Example 5, the relative sugar alcohol concentration in the core spinning solution of Examples 1-2 is relatively high, the viscosity of the core solution is relatively high, and obvious core-shell structures are formed after spinning and solidification crystallization. In Comparative Example 5, due to too little sugar alcohol content, an obvious core-shell structure cannot be formed, so the moisture absorption and cooling effect of Comparative Example 2 is also poor.

[0074] Unless otherwise specified, the raw materials and equipment used in the present invention are all common raw materials and equipment in the art; unless otherwise specified, the methods used in the present invention are all conventional methods in the art.

[0075] 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 based on the technical essence of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A preparation method of a self-adhesive moisture-absorbing and cooling composite nanofiber membrane loaded with sugar alcohol, characterized in that It includes the following steps: (1) Dissolve sugar alcohol, polyvinyl alcohol, and dopamine hydrochloride in water respectively; add the obtained dopamine hydrochloride solution to the obtained polyvinyl alcohol solution; use the obtained sugar alcohol solution with a concentration of 60-70 wt% and the obtained polyvinyl alcohol / dopamine hydrochloride solution as the core layer spinning solution and the shell layer spinning solution respectively, and perform coaxial electrospinning with a core-shell layer spinning flow rate ratio of 1:8-10 to obtain a sugar alcohol@polyvinyl alcohol / dopamine hydrochloride composite nanofiber membrane; (2) Place the composite nanofiber membrane obtained in step (1), an acid catalyst, and a desiccant together in a sealed container with an aqueous glutaraldehyde solution at the bottom, where the composite nanofiber membrane, the acid catalyst, and the desiccant are above the aqueous glutaraldehyde solution. After the surface of the composite nanofiber membrane comes into contact with the volatilized glutaraldehyde, a cross-linking reaction occurs to prepare a self-adhesive moisture-absorbing and cooling composite nanofiber membrane loaded with sugar alcohol.

2. The preparation method according to claim 1, characterized in that: In step (1), the polyvinyl alcohol is heated to ≥95 °C and dissolved after adding water.

3. The preparation method according to claim 1, characterized in that: In step (1), the sugar alcohol is sorbitol and / or xylitol; the content of polyvinyl alcohol in the polyvinyl alcohol / dopamine hydrochloride solution is 8-12 wt%, and the content of dopamine hydrochloride is 3-5 wt%.

4. The preparation method according to claim 1, characterized in that: In step (1), the parameters of the coaxial electrospinning are: needle gauge 20-22G, distance 15-20 cm, voltage 18-28 kv, temperature 25-30 °C, humidity 40-50%RH.

5. The preparation method according to claim 4, characterized in that: In step (1), the electrospinning time of the coaxial electrospinning is 4-12 h, and the flow rate of the core layer spinning solution propulsion pump is 0.0002-0.0004 mm / s.

6. The preparation method according to claim 1, characterized in that: In step (1), the diameter of the composite nanofibers in the sugar alcohol@polyvinyl alcohol / dopamine hydrochloride composite nanofiber membrane is 400-1000 nm; the thickness of the sugar alcohol@polyvinyl alcohol / dopamine hydrochloride composite nanofiber membrane is 0.2-0.4 mm.

7. The preparation method according to claim 1, characterized in that: In step (2), the temperature of the cross-linking is 25-30 °C, and the time is 5-11 h.

8. The preparation method according to claim 1, characterized in that: In step (2), the acid catalyst is concentrated hydrochloric acid; the desiccant is anhydrous calcium chloride.

9. The preparation method according to claim 1 or 8, characterized in that: In step (2), the dosage ratio of the acid catalyst to the composite nanofiber membrane is 8-12 mL / 5 g; the dosage ratio of the desiccant to the composite nanofiber membrane is 8-12 g / 5 g; the concentration of the aqueous glutaraldehyde solution is 25-50 wt%, and the dosage ratio of the aqueous glutaraldehyde solution to the composite nanofiber membrane is 8-12 mL / 5 g.

10. Use of the self-adhesive moisture-absorbing and cooling composite nanofiber membrane loaded with sugar alcohol prepared by the preparation method according to any one of claims 1-9 as a raw material in the preparation of human skin local wet-heat management products.

Images