A full bio-based fabric for unidirectional moisture management of different viscosity liquids, and a preparation method and application thereof

Abstract

This invention relates to the field of textile materials, specifically to a fully bio-based fabric suitable for unidirectional moisture wicking in liquids of varying viscosities, its preparation method, and its applications. The fully bio-based fabric comprises a double-layer composite structure formed by hot-melt bonding of spunlace nonwoven fabric and meltblown nonwoven fabric. The spunlace nonwoven fabric is made of hydrophilic cellulose, and the meltblown nonwoven fabric is made of bio-based polyurethane. The fiber diameter D1 of the spunlace nonwoven fabric is 5–20 μm, the thickness H1 is 0.5–1.0 mm, and the basis weight M1 is 40–80 g / m². 2 The fiber diameter D2 of meltblown nonwoven fabric is 20um to 60um, the thickness H2 is 0.05 to 0.2mm, and the basis weight M2 is 10 to 50g / m². 2 Furthermore, D2>D1, H1>H2, and M1>M2. The all-bio-based fabric of this invention not only exhibits high-flux unidirectional permeability to sweat (Newtonian fluid) but also unidirectional permeability to fluids with a certain viscosity (non-Newtonian fluid), making it a promising candidate for applications in human body thermal management clothing, sanitary napkins, diapers, and medical protective materials, particularly in areas such as moisture wicking, blood flow, and micro-control of viscous fluids.

Description

Technical Field

[0001] This invention relates to the field of textile materials, specifically to a fully bio-based fabric that can be used for unidirectional moisture wicking of liquids of different viscosities, its preparation method, and its application. Background Technology

[0002] Unidirectional moisture wicking refers to the one-way nature of liquid transport; that is, liquid can only spontaneously travel along the thickness direction or from one side of the material to the other, and cannot travel in the opposite direction. The unidirectional moisture wicking property of fabrics has significant application value in many fields, including sportswear, outdoor equipment, medical and nursing supplies, and protective clothing. However, existing unidirectional moisture-wicking textiles have certain shortcomings in terms of application targets, material design, and manufacturing processes.

[0003] 1) Application goals: The current application goals of unidirectional moisture-wicking textile research have been limited to the directional conduction of liquid water. In fact, in our daily lives, apart from water and air, most other fluids are non-Newtonian fluids, such as blood, lymph and other biological fluids, milk, ink, paint, petroleum and polymer solutions, etc.

[0004] 2) Material design: A significant portion of unidirectional moisture-wicking textiles are designed and produced using traditional chemical fibers. Chemical fibers have high energy consumption per unit, are generally non-recyclable and difficult to degrade naturally, and pose a significant threat to the ecological environment. This is not conducive to the realization of my country's long-term goal of "carbon peaking and carbon neutrality".

[0005] 3) Preparation process: Existing main methods include weaving with hydrophobic and hydrophilic yarns, constructing a hydrophobic layer on a hydrophilic matrix fiber or fabric through electrospinning, and chemically modifying hydrophilic or hydrophobic fabrics to create differences in wettability of fabric layers or structures. These methods all involve the use of organic solvents, and electrospinning cannot yet be mass-produced due to limitations in process conditions and processing efficiency.

[0006] For example, patent CN115071232A discloses a smart one-way moisture-wicking fabric, which uses hydrophilic chemical fibers, hydrophobic chemical fibers, and a composite fiber of both twisted together to create a wetting gradient in the fabric's thickness direction. Patent CN114379186A discloses a breathable and sweat-wicking skin-friendly fabric and its preparation method, which involves dissolving polyurethane, polylactic acid-glycolic acid copolymer, and polyacrylonitrile in tetrahydrofuran and preparing a multilayer fiber membrane through electrospinning, then combining the skin-friendly layer and the drainage layer using hot pressing to obtain the breathable and sweat-wicking skin-friendly fabric. Similarly, patent CN116676718A discloses a one-way moisture-wicking TPU elastic bandage, which uses electrospinning to place TPU dissolved in DMAc solvent onto the surface of a meltblown nonwoven fabric matrix to form a nanofiber membrane, and then hot pressing to obtain the elastic bandage. Patent CN114797282A discloses an antibacterial, antiviral, and unidirectional moisture-wicking composite filter material and its application. From the inside out, it includes a hydrophobic support layer, a filter layer, and a hydrophobic protective layer. The filter layer consists of a conventional meltblown polypropylene nonwoven fabric layer and an antibacterial, antiviral, and hydrophilic modified meltblown polypropylene nonwoven fabric layer. Patent CN117325526A discloses a TPU composite meltblown membrane and a composite fabric using the TPU composite meltblown membrane. The TPU composite meltblown membrane is used to bond a nylon-spandex four-way stretch fabric with good moisture permeability and air permeability, along with a woven / knitted composite base fabric, into a single unit, resulting in a composite fabric with good moisture permeability and air permeability. And a breathable one-way moisture-wicking protective material disclosed in patent CN105729918A, which uses electrospinning of water-repellent and hydrophilic polymer spinning solutions to obtain fibers with different wettability, then plasma or brushing treatment of pure cotton fine yarn high-density fabric to be used as water-repellent layer, polyamide and other chemical fibers as lining, and finally the water-repellent layer fabric layer, hot melt adhesive mesh, electrospun nanofiber layer, secondary hot melt adhesive mesh and lining are stacked in sequence and heat-pressed to obtain a three-layer breathable one-way moisture-wicking protective material. The patents CN205467700U (disclosed a unidirectional moisture-wicking nonwoven fabric), CN116200872A (disclosed a pure cotton unidirectional moisture-wicking fabric), CN113215714A (disclosed a unidirectional moisture-wicking dyed fabric), CN117568970A (disclosed a production method for polyester filament and cellulose yarn and interwoven unidirectional moisture-wicking functional fabric), CN118007442A (disclosed a unidirectional moisture-wicking fabric and its preparation method), CN113564918A (disclosed a preparation method for Janus fabric with unidirectional droplet permeability), and CN113308871A (disclosed a preparation method for unidirectional moisture-wicking and stain-resistant fabric based on cleaning technology) all employ chemical treatment methods such as impregnation, spraying, and chemical grafting to load low surface energy chemical substances onto one side of hydrophilic fabrics such as cotton fabrics to construct multi-layered fabrics with different wettability, thereby achieving unidirectional moisture wicking.

[0007] In summary, it is of great significance to develop a functional material that not only has unidirectional permeability to liquid water, blood, and viscous fluids, but also possesses biodegradability and green recycling properties, using an environmentally friendly, low-cost, and scalable production method. Summary of the Invention

[0008] Existing unidirectional moisture-wicking fabrics suffer from several drawbacks, such as the extensive use of petroleum-based chemical fibers in their material design, chemical treatments involving organic solvents in their production processes, and limited application scenarios, restricting their ability to wick away only liquid water. This invention aims to address these issues by providing a functional bio-based fabric that not only exhibits unidirectional wicking properties for liquid water, blood, and viscous fluids, but also possesses biodegradability, can be produced solvent-free, and can be mass-produced.

[0009] To achieve the above objectives, on the one hand, the present invention provides a fully bio-based fabric that can be used for unidirectional moisture wicking of liquids of different viscosities. The fully bio-based fabric is a double-layer composite structure formed by hot-melt pressing technology of spunlace nonwoven fabric and meltblown nonwoven fabric. The spunlace nonwoven fabric is made of hydrophilic cellulose, and the meltblown nonwoven fabric is made of bio-based polyurethane.

[0010] Among them, the fiber diameter D1 of the spunlace nonwoven fabric is 5-20 μm, the average opening size L1 in the vertical direction of the fabric is 0.1-2 μm, the thickness H1 is 0.5-1.0 mm, and the basis weight M1 is 40-80 g / m². 2 The fiber diameter D2 of meltblown nonwoven fabric is 20um to 60um, the average pore size L2 in the vertical direction of the fabric is 30 to 100um, the thickness H2 is 0.05 to 0.25um, and the basis weight M2 is 10 to 50g / m². 2 And D2>D1, L2>L1, H1>H2, M1>M2.

[0011] As a further preferred technical solution of the present invention, the molecular weight (Mw) of the bio-based polyurethane is 20,000 to 120,000 g / mol, and its prepolymer components, polyether / ester polyol and diisocyanate, are both derived from biomass materials.

[0012] As a further preferred technical solution of the present invention, the hydrophilic cellulose is any one or more of wood cellulose, cotton cellulose, bamboo cellulose, hemp cellulose and grass cellulose.

[0013] According to another aspect of the present invention, the present invention also provides a method for preparing a fully bio-based fabric that can be used for unidirectional moisture wicking of liquids of different viscosities, comprising the following steps:

[0014] S1. Using thermoplastic bio-based polyurethane granules as raw materials, meltblown nonwoven fabric is obtained through meltblown spinning technology;

[0015] S2. Adopt the hot melt pressing technology to melt the melt-blown non-woven fabric, and then bond it to the spunlace non-woven fabric under pressure to form a laminated fabric, that is, a fully biodegradable fabric that can be used for one-way moisture conduction of liquids with different viscosities is obtained.

[0016] As a further preferred technical solution of the present invention, the melt-blown spinning is processed as follows:

[0017] After the thermoplastic biodegradable polyurethane pellets are heated, transferred and melted in a twin-screw extruder, the melt stream is extruded from the spinneret holes of the melt-blown processing nozzle, and is continuously blown by the hot pressing air flow continuously supplied by the spinneret holes dispersed on the surface of the spinneret plate. The melt is stretched to form microfibers, and then self-adheres and forms on the winding machine to obtain the melt-blown non-woven fabric.

[0018] As a further preferred technical solution of the present invention, the diameter of the spinneret holes of the melt-blown processing nozzle is 0.2 - 0.3 mm, and the center distance of the spinneret holes is 0.6 - 0.8 mm.

[0019] As a further preferred technical solution of the present invention, the parameters of the melt-blown spinning are: the hot air flow pressure is 0.2 - 0.4 MPa, the receiving distance of the winding machine is 20 - 25 cm, and the winding speed is 0.5 - 5 m / min.

[0020] As a further preferred technical solution of the present invention, the parameters of the hot melt pressing are: the temperature T is 120 - 180 °C, the pressure P is 0.05 - 0.5 MPa, and the time t is 1 / 30 min - 10 min.

[0021] As a further preferred technical solution of the present invention, the processing equipment for the hot melt pressing technology is a hot pressing machine, a hot melt bonding machine, a flat laminating machine, a heat printing machine or a vacuum hot press.

[0022] According to another aspect of the present invention, the present invention also provides an application of the fully biodegradable fabric in one-way moisture conduction of non-Newtonian fluids. Compared with Newtonian fluids (such as water), the viscous dissipation of viscous fluids will form a blockage to the liquid transmission. In order to enhance the directional liquid transmission ability from the hydrophobic layer (melt-blown non-woven fabric) to the hydrophilic layer (spunlace non-woven fabric), the design of the fully biodegradable fabric of the present invention involves the synergistic effect of two gradients: 1) Wettability gradient: from the hydrophobic layer to the hydrophilic layer; 2) Geometric structure (capillary force gradient): D2 > D1 in the fiber diameter and L1 < L2 in the vertical direction between fibers, that is, the bifurcated network structure forms a hierarchical connected pore channel of large pores - small pores.

[0023] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0024] 1. The one-way moisture-wicking, fully bio-based fabric of this invention uses hydrophilic cellulose spunlace nonwoven fabric (also known as natural cellulose fabric) as the base material, and a bio-based polyurethane (Bio TPU) meltblown nonwoven fabric as the hydrophobic layer. It does not contain any other chemical substances. Compared with the traditional petrochemical-based fabric base and polyurethane used in the prior art, the fully bio-based fabric has advantages such as reduced carbon emissions, sustainable regeneration of raw materials, green production, and biodegradability.

[0025] 2. This invention uses a chemical solvent-free processing technology, namely hot-press bonding, which is more environmentally friendly than chemical modification methods such as coating and grafting used in other inventions. Compared with electrospinning technology, it has lower production costs and higher efficiency, and has the advantages of sustainable and large-scale processing and production.

[0026] 3. Compared with other inventions that use petroleum-based polyurethane hot melt adhesive film as an adhesive to laminate and bond multiple layers of fabric, this invention designs fewer fabric layers, namely, hydrophilic spunlace nonwoven fabric (also known as natural cellulose fabric) as the base material, and bio-based polyurethane (Bio TPU) meltblown nonwoven fabric as the hydrophobic layer, which is simple in design and low in cost.

[0027] 4. The unidirectional moisture-wicking bio-based fabric of the present invention not only has high-throughput unidirectional permeability for sweat (Newtonian fluid), but also has unidirectional permeability for fluids with a certain viscosity (non-Newtonian fluid), making it a promising material for applications in human body thermal management clothing, sanitary napkins, diapers and medical protective materials, such as moisture-wicking and perspiration-wicking, blood flow and micro-control of viscous fluids. Attached Figure Description

[0028] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0029] Figure 1 The images show physical specimens and optical microscope images of the natural cellulose fabric and Bio TPU meltblown nonwoven fabric used in the embodiments and comparative examples of this invention, as well as pore size distribution and fabric porosity distribution diagrams. Figures a1 and a2 are physical images of the natural cellulose fabric and Bio TPU meltblown nonwoven fabric, respectively; Figures b and c show the corresponding fiber diameter distributions; Figure dg shows the Bio TPU basis weight of 15 g / m³ in Examples 1-4. 2 30g / m 2 45g / m 2 60g / m 2 Pore ​​size distribution of meltblown microfiber fabric; Figure h shows the Bio TPU basis weight of 15 g / m² in Comparative Example 2. 2 Pore ​​size distribution of meltblown microfiber fabric.

[0030] Figure 2The images shown are scanning electron microscope images, Fourier transform infrared spectral curves, and porosity of the corresponding functional bio-based fabrics prepared by hot-press bonding process in Examples 1-4 of this invention.

[0031] Figure 3 The results of unidirectional conductivity tests on fluids of different viscosities are shown for the corresponding functional bio-based fabrics prepared by hot-press bonding process in Examples 1-4 and Comparative Examples 1-2 of this invention.

[0032] Figure 4 The results of unidirectional permeability and impermeability tests on the functional bio-based fabrics prepared by the hot-press bonding process in Examples 1-4 of this invention are shown.

[0033] The objectives, features, and advantages of this invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0034] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0035] Unless otherwise defined, the technical terms used in the following embodiments have the same meanings as commonly understood by those skilled in the art to which this invention pertains. Unless otherwise specified, the experimental reagents used in the following embodiments are conventional biochemical reagents; and the experimental methods described are conventional methods.

[0036] Example 1:

[0037] 1) Preparation of bio-based polyurethane (Bio TPU) meltblown nonwoven fabric

[0038] Bio-based polyurethane with a molecular weight of 60,000 g / mol (prepolymer components are bio-based PDI, namely 1,5-pentanediisocyanate, sebacic acid polyester polyol, and 1,4-butanediol) was used for meltblown processing. The processing nozzle (spinneret) of the twin-screw meltblown equipment had a diameter of 0.2 mm and a center-to-center distance of 0.6 mm. First, the polyurethane granules were dried, then added to the twin-screw feed inlet where they were continuously transferred, melted, and homogenized into a melt. This melt was then sprayed and stretched under the pressure of hot gas to form fibers on an automatic receiving device. The temperatures of the five processing zones on the screw were: Zone 1: 160℃, Zone 2: 190℃, Zones 3 and 4: 220℃, and Zone 5 (die head): 240℃. The screw extrusion speed was 12 rpm. The meltblown hot gas flow pressure was 0.25 MPa, the receiving distance of the winding machine was 20 cm, and the winding speed was 2.4 m / min. The final product with a basis weight of 15 g / cm³ was obtained through meltblowing processing. 2The Bio TPU meltblown nonwoven fabric has a fabric thickness of 0.05um, a fiber diameter of 35um to 45um, an average pore size of 81.75um in the vertical direction, and a porosity of 75.88%.

[0039] 2) Hot melt composite

[0040] A composite material was created by using spunlace nonwoven fabric made from natural fiber cotton as the cellulose fabric substrate and combining it with Bio TPU meltblown nonwoven fabric. The Bio TPU meltblown nonwoven fabric and the spunlace nonwoven fabric were bonded together using a continuous hot-press bonding machine. Specifically, the Bio TPU meltblown nonwoven fabric roll and the spunlace nonwoven fabric roll were placed on fabric rod 1 and fabric rod 2, respectively. The preload of the pressure rollers was set to 0.01 MPa, the rotation speed to 60 rpm, and the conveying speed to 2.5 m / min. The pressure of the pressure rollers in the hot-melt bonding zone was 0.025 MPa, the temperature was 136℃, and the rotation speed was 60 rpm. Here, the basis weight of the spunlace nonwoven fabric was 60 g / cm³. 2 The fiber has a thickness of 0.8 mm, a fiber diameter of 10 μm to 15 μm, an average pore size of 0.1 to 2 μm in the vertical direction, and a porosity of 79.44%.

[0041] Through the above process, a fully bio-based fabric with a Bio TPU meltblown nonwoven fabric to spunlace nonwoven fabric weight ratio of 1:4, i.e. Bio TPU content of 20wt%, and a fabric porosity of 71.64% is finally obtained.

[0042] Examples 2-4 below use Bio TPU with the same components as in Example 1.

[0043] Example 2:

[0044] 1) Preparation of bio-based polyurethane (Bio TPU) meltblown nonwoven fabric

[0045] Bio-based polyurethane with a molecular weight of 60,000 g / mol was used for meltblown processing. The twin-screw meltblown equipment used had a nozzle diameter of 0.2 mm and a spinneret center-to-center distance of 0.6 mm. First, the polyurethane granules were dried, then fed into the twin-screw feed inlet where they were continuously transferred, melted, and homogenized into a melt. This melt was then sprayed and stretched under the pressure of hot gas to form fibers on an automatic receiving device. The temperatures in the five processing zones of the screw were: Zone 1 160℃, Zone 2 190℃, Zones 3 and 4 220℃, and Zone 5 (die head) 240℃. The screw extrusion speed was 12 rpm. The meltblown hot gas flow pressure was 0.25 MPa, the receiving distance of the winding machine was 20 cm, and the winding speed was 1.6 m / min. The final product obtained through the meltblown process had a basis weight of 30 g / cm³. 2The Bio TPU meltblown nonwoven fabric has a fabric thickness of 0.066um, a fiber diameter of 35um to 45um, an average pore size of 55.21um in the vertical direction, and a porosity of 50.69%.

[0046] 2) Hot melt composite

[0047] A composite process was performed using spunlace nonwoven fabric made from natural fiber cotton as the base material for cellulose fabric and Bio TPU meltblown nonwoven fabric. The Bio TPU meltblown nonwoven fabric and the cellulose fabric were thermally bonded together using a continuous hot-press bonding machine (also known as hot-melt bonding). The Bio TPU meltblown nonwoven fabric roll and the spunlace nonwoven cotton roll were placed on fabric rod 1 and fabric rod 2, respectively. The pre-pressure of the pressure rollers was set to 0.01 MPa, the rotation speed to 60 rpm, and the conveying speed to 2.5 m / min. The pressure of the pressure rollers in the hot-melt bonding zone was 0.25 MPa, the temperature was 136℃, and the rotation speed was 60 rpm. The basis weight of the spunlace nonwoven cotton fabric was 60 g / cm³. 2 The fiber thickness is 0.8 mm, the fiber diameter is 10 μm to 15 μm, the average pore size in the vertical direction is 0.1 to 2 μm, and the porosity is 79.44%.

[0048] The above process ultimately yields a fully bio-based fabric with a Bio TPU meltblown nonwoven fabric to spunlace nonwoven fabric weight ratio of 1:2, i.e., a Bio TPU content of 33wt%, and a fabric porosity of 63.47%.

[0049] Example 3:

[0050] 1) Preparation of bio-based polyurethane (Bio TPU) meltblown nonwoven fabric

[0051] Bio-based polyurethane with a molecular weight of 60,000 g / mol was used for meltblown processing. The twin-screw meltblown equipment used had a spinneret diameter of 0.2 mm and a center-to-center distance of 0.6 mm. First, the polyurethane granules were dried. Then, the granules were added to the twin-screw feed inlet and continuously transferred, melted, and homogenized into a melt. This melt was then sprayed and stretched under the pressure of hot gas to form fibers on an automatic receiving device. The temperatures in the five processing zones of the screw were: Zone 1 160℃, Zone 2 190℃, Zones 3 and 4 220℃, and Zone 5 (die head) 240℃. The screw extrusion speed was 12 rpm. The meltblown hot gas pressure was 0.25 MPa, the receiving distance of the winding machine was 20 cm, and the winding speed was 0.8 m / min. The final product obtained through the meltblown process had a basis weight of 45 g / cm³. 2 The Bio TPU meltblown nonwoven fabric has a fabric thickness of 0.091um, a fiber diameter of 35um to 45um, an average pore size of 43.58um in the vertical direction, and a porosity of 23.26%.

[0052] 2) Hot melt composite

[0053] A composite material was created by using spunlace nonwoven fabric made from natural fiber cotton as the base material for a cellulose fabric and combining it with Bio TPU meltblown nonwoven fabric. A continuous hot-press bonding machine was used to bond the Bio TPU meltblown nonwoven fabric and the cellulose fabric together. The Bio TPU meltblown nonwoven fabric and the spunlace nonwoven cotton fabric were rolled onto fabric rods 1 and 2, respectively. The pre-pressure of the pressure rollers was set to 0.01 MPa, the rotation speed to 60 rpm, and the conveying speed to 2.5 m / min. The pressure of the pressure rollers in the hot-melt bonding zone was 0.025 MPa, the temperature was 136℃, and the rotation speed was 60 rpm. The basis weight of the spunlace nonwoven cotton fabric was 60 g / cm³. 2 The fiber has a thickness of 0.8 mm, a fiber diameter of 10 μm to 15 μm, an average pore size of 0.1 to 2 μm in the vertical direction, and a porosity of 79.44%.

[0054] The above process ultimately yields a fully bio-based fabric with a Bio TPU meltblown nonwoven fabric to spunlace nonwoven fabric weight ratio of 3:4, i.e., a Bio TPU content of 43wt%, and a fabric porosity of 53.12%.

[0055] Example 4:

[0056] 1) Preparation of bio-based polyurethane (Bio TPU) meltblown nonwoven fabric

[0057] Bio-based polyurethane with a molecular weight of 60,000 g / mol was used for meltblown processing. The twin-screw meltblown equipment used had a spinneret diameter of 0.2 mm and a center-to-center distance of 0.6 mm. First, the polyurethane granules were dried. Then, the granules were added to the twin-screw feed inlet and continuously transferred, melted, and homogenized into a melt. This melt was then sprayed and stretched under the pressure of hot gas to form fibers on an automatic receiving device. The temperatures in the five processing zones of the screw were: Zone 1: 160℃, Zone 2: 190℃, Zones 3 and 4: 220℃, and Zone 5 (die head): 240℃. The screw extrusion speed was 12 rpm. The meltblown hot gas pressure was 0.25 MPa, the receiving distance of the winding machine was 20 cm, and the winding speed was 0.4 m / min. The final product obtained through the meltblown process had a basis weight of 60 g / cm³. 2 The Bio TPU meltblown nonwoven fabric has a fabric thickness of 0.117um, a fiber diameter of 35um to 45um, an average pore size of 32.98um in the vertical direction, and a porosity of 6.92%.

[0058] 2) Hot melt composite

[0059] A composite material was created by using spunlace nonwoven fabric made from natural fiber cotton as the base material for a cellulose fabric and combining it with Bio TPU meltblown nonwoven fabric. A continuous hot-press bonding machine was used to bond the Bio TPU meltblown nonwoven fabric and the cellulose fabric together. The Bio TPU meltblown nonwoven fabric and the spunlace nonwoven cotton fabric were rolled onto fabric rods 1 and 2, respectively. The pre-pressure of the pressure rollers was set to 0.01 MPa, the rotation speed to 60 rpm, and the conveying speed to 2.5 m / min. The pressure of the pressure rollers in the hot-melt bonding zone was 0.025 MPa, the temperature was 136℃, and the rotation speed was 60 rpm. The basis weight of the spunlace nonwoven cotton fabric was 60 g / cm³. 2 The thickness is 0.8 mm, and the fiber diameter is 10 μm to 15 μm. Through the above process, a fully bio-based fabric with a Bio TPU meltblown nonwoven fabric to spunlace nonwoven fabric weight ratio of 1:1, i.e., a Bio TPU content of 50 wt%, and a fabric porosity of 40.90% is finally obtained.

[0060] Comparative Example 1:

[0061] To compare the unidirectional droplet conductivity of fully bio-based fabrics and pure cellulose fabrics, a pure cellulose fabric was used as a blank sample for processing and comparison. The cellulose fabric was a spunlace nonwoven fabric made of natural fiber cotton with a basis weight of 60 g / cm³. 2 The thickness is 0.8 mm, and the fiber diameter is 10 μm to 15 μm. The cellulose fabric is rolled onto the fabric rod 1, and the pre-pressure of the pressure roller is set to 0.01 MPa, the rotation speed is 60 rpm, the conveying speed is 2.5 m / min, the pre-pressure of the pressure roller in the hot melt bonding zone is 0.025 MPa, the temperature is 136℃, and the rotation speed is 60 rpm. Finally, a pure cellulose fabric with a Bio TPU content of 0 wt% is obtained.

[0062] Comparative Example 2:

[0063] The unidirectional conductivity of viscous droplets in this invention is based on the geometric parameters of Bio TPU meltblown nonwoven fabric. The capillary force generated by these geometric structures can counteract the flow dissipation of viscous fluids, thereby achieving unidirectional moisture conduction. To verify the influence of fiber diameter and porosity in the geometric parameters of meltblown nonwoven fabric on the unidirectional conductivity of different fluids, a comparative example is proposed as a comparison experiment of Example 1, the difference being that the diameter of the processing nozzle (spinneret) of meltblown spinning is adjusted to 0.1 mm.

[0064] 1) Preparation of bio-based polyurethane (Bio TPU) meltblown nonwoven fabric

[0065] Bio-based polyurethane with a molecular weight of 60,000 g / mol was used for meltblown processing. The twin-screw meltblown equipment used had a spinneret diameter of 0.1 mm and a center-to-center distance of 0.6 mm. First, the polyurethane granules were dried. Then, the granules were added to the twin-screw feed inlet and continuously transferred, melted, and homogenized into a melt. This melt was then sprayed and stretched under the pressure of hot gas to form fibers on an automatic receiving device. The temperatures in the five processing zones of the screw were: Zone 1: 160℃, Zone 2: 190℃, Zones 3 and 4: 220℃, and Zone 5 (die head): 240℃. The screw extrusion speed was 12 rpm. The meltblown hot gas pressure was 0.25 MPa, the receiving distance of the winding machine was 35 cm, and the winding speed was 0.4 m / min. The final product obtained through the meltblown process had a basis weight of 15 g / cm³. 2 The Bio TPU meltblown nonwoven fabric has a fabric thickness of 0.65µm, a fiber diameter of ~4µm, an average pore size of 14.87µm in the vertical direction, and a porosity of 45.27%.

[0066] 2) Hot melt composite

[0067] A composite material was created by combining natural fiber cotton spunlace nonwoven fabric as the cellulose fabric substrate with Bio TPU microfibers. The Bio TPU microfibers and cellulose fabric were bonded together using a continuous hot-press bonding machine. The Bio TPU microfibers and spunlace nonwoven cotton fabric were rolled onto fabric rods 1 and 2, respectively. The pre-pressure of the pressure rollers was set to 0.01 MPa, the rotation speed to 60 rpm, the conveying speed to 2.5 m / min, and the pressure of the pressure rollers in the hot-melt bonding zone to 0.025 MPa, the temperature to 136℃, and the rotation speed to 60 rpm. The basis weight of the spunlace nonwoven cotton fabric was 60 g / cm³. 2 The thickness is 0.8 mm, and the fiber diameter is 10 μm to 15 μm. Through the above process, a fully bio-based fabric with a Bio TPU meltblown nonwoven fabric to cellulose fabric weight ratio of 1:4, i.e., a Bio TPU content of 20 wt%, is finally obtained.

[0068] Based on the samples prepared in the above embodiments and comparative examples, their material characterization, performance testing, and result analysis are discussed below:

[0069] 1. Basic characterization of materials

[0070] Figure 1 The images show physical specimens and optical microscope images of the natural cellulose fabrics and Bio TPU microfibers used in the embodiments and comparative examples of this invention, as well as pore size distribution and fabric porosity distribution diagrams. Figures a1 and a2 are physical images of the natural cellulose fabric and Bio TPU microfibers, respectively. Figure 1b and c represent the corresponding fiber diameter distributions. We can see that the fiber diameter of spunlace nonwoven cotton fabric ranges from 5µm to 25µm, with an average diameter of approximately 15µm, and the pores between fibers are relatively small; while the diameter of Bio TPU microfibers ranges from 25µm to 55µm, with an average diameter of approximately 40µm, and the pores between fibers are slightly larger. Figure 1 The middle and dh represent the weight of Bio TPU as 15g / m³. 2 (Example 1), 30g / m 2 (Example 2), 45g / m 2 (Example 3), 60g / m 2 (Example 4) and 15g / m 2 (Comparative Example 2) Pore size distribution of microfiber fabric: It can be seen that as the basis weight increases, the pore size between fibers gradually decreases. When the Bio TPU basis weight is 60 g / m², the pore size distribution is significantly smaller. 2 The average pore size is 33 μm, at which point the bonded material tends to form a film.

[0071] Figure 2 These are scanning electron microscope images of the corresponding functional bio-based fabrics prepared by the hot-press bonding process in Examples 1-4 of this invention. Figure 2 The loading amounts of Bio TPU hot melt adhesive mesh in the ad were 15g (20wt%), 30g (33wt%), 45g (43wt%), and 60g (50wt%). The Fourier transform infrared spectral curves of the combined functional bio-based fabrics were then analyzed. Figure 2 In the middle (e), it appears at 1720cm. -1 The presence of ester groups (C=O) indicates that the meltblown nonwoven fabric is well bonded to the cellulose fabric via a thermo-press bonding process, and the absence of new peak migrations suggests that Bio TPU did not decompose during this process. Scanning electron microscopy images reveal that as the loading of the meltblown nonwoven fabric increases, the porosity of the inner layer decreases. At a loading of 60g (50wt%), a tendency for the Bio TPU meltblown nonwoven fabric to crosslink into a sealing film with a certain thickness can be observed. Furthermore, due to the dual gradient differences in surface wettability (Bio TPU is water-repellent, cellulose fabric is hydrophilic) and geometric structure (pore size, porosity) among the three loading fabrics, liquid in the inner layer can penetrate and diffuse to the surface layer under the combined action of gravity, capillary force, and surface tension, completing the fluid transfer. Figure 2 In the figure, f represents the porosity of fabrics with different BioTPU loadings (Examples 1-4), showing a basis weight of 60 g / m². 2 The porosity of the spunlace nonwoven cotton fabric is about 80%. As the Bio TPU loading increases, the porosity gradually decreases. When the loading is 60 g / m³, the porosity decreases further. 2At 50 wt%, the fabric porosity drops below 50%. The pore size and porosity distributions above are experimental parameter values ​​for unidirectional flow of viscous droplets.

[0072] 2. One-way conductivity test of fully bio-based fabrics (also known as functional bio-based fabrics) for fluids of different viscosities.

[0073] To investigate the unidirectional conductivity of functional bio-based fabrics to fluids of different viscosities, four fluids with different viscosities were prepared. Pure water was used as a Newtonian fluid, and then sodium carboxymethyl cellulose (CMC-Na) aqueous solutions with mass fractions of 0.5 wt%, 1 wt%, and 2 wt% were prepared respectively. At room temperature, a certain mass fraction of CMC-Na was added to a beaker containing the pure aqueous solution and mechanically stirred for 6 hours, then allowed to stand for 1 hour. The CMC-Na aqueous solution exhibited a certain viscosity and was therefore a non-Newtonian fluid. The droplet transport behavior in porous media is essentially a physical phenomenon of fluid permeation and diffusion under the combined action of gravity, capillary force, and surface tension. Therefore, the fluid properties related to the above physical forces were tested, as shown in Table 1. It was found that compared to pure water, the density of the CMC-Na aqueous solution remained almost unchanged, while the surface tension and contact angle changed slightly, essentially not affecting the droplet permeation and diffusion behavior. However, the viscosity changed by orders of magnitude, so the difference in viscous dissipation is the main difference among non-Newtonian fluids. The unidirectional permeability test of fluids with different viscosities was studied by investigating the penetration and diffusion behavior of droplets on a horizontally placed fabric surface under quasi-static conditions. The fabric (Bio TPU meltblown nonwoven fabric - hydrophobic layer) was placed horizontally on absorbent A4 paper with the inner layer facing upwards. The outer layer of the fabric (pure cellulose fabric - hydrophilic layer) was in direct contact with the A4 paper. When the quasi-static droplet penetrated the inner layer of the fabric and diffused vertically to the outer layer, the A4 paper became wet. The test results are as follows: Figure 3 As shown.

[0074] Table 1 Physical properties of fluids with different viscosities

[0075]

[0076] like Figure 3 As shown, the effects of the loading amount of Bio TPU meltblown nonwoven fabric, the viscosity of the solution, and the volume of the droplets on the unidirectional conduction behavior of different fluids on the surface of the functional bio-based fabric were investigated. We were able to find that:

[0077] 1) Pure cellulose fabric (Comparative Example 1) (Bio TPU meltblown nonwoven fabric loading of 60g (0wt%)) Due to the lack of surface wettability and the dual gradient difference in geometry, it does not have unidirectional conductivity for fluids of different viscosities and volumes.

[0078] 2) The functional fabric with a Bio TPU meltblown nonwoven fabric loading of 60g (50wt%) (Example 4) undergoes in-situ melting and film formation due to the overload of the water-repellent meltblown nonwoven fabric on the surface, resulting in a water-repellent film with almost no pore structure on the fabric surface, which prevents fluid from penetrating and does not have unidirectional conductivity.

[0079] 3) The functional fabrics with Bio TPU meltblown nonwoven fabric loadings of 15g (20wt%), 30g (33wt%), and 45g (43wt%) exhibit a dual gradient difference in the wettability of the fabric components and their geometric structure (pore size and fiber diameter). This allows droplets in the inner layer of the fabric to be pumped into the cellulose fabric under the influence of capillary force and gravity, and then diffuse to the surface of A4 paper to wet it. When droplets are placed from the outer layer, the strong capillary force of the hydrophilic fiber fabric causes the droplets to diffuse laterally inside the cellulose fabric, preventing them from penetrating and spreading in the inner layer to wet the A4 paper. Therefore, the aforementioned functional bio-based fabrics possess a certain degree of unidirectional permeability to droplets of different viscosities.

[0080] 4) In addition, according to Figure 3 We can also conclude that increasing the solution viscosity, i.e., increasing viscous dissipation, increases the resistance to fluid penetration and diffusion within the fabric, hindering unidirectional fluid flow. For example, in functional bio-based fabrics with a Bio TPU meltblown nonwoven fabric loading of 20 wt%, the... Figure 3 As can be seen from AC, the former only exhibits unidirectional conductivity for pure aqueous solutions of varying volumes, while when the fluid is a 0.5wt% CMC-Na solution, it only exhibits unidirectional conductivity for droplets up to 50µL, and completely lacks unidirectional conductivity for a 1wt% CMC-Na solution; furthermore, from Figure 3 As can be seen from the data, when the loading of Bio TPU meltblown nonwoven fabric is 43wt%, the dual gradient difference of the functional bio-based fabric results in the best unidirectional conductivity of droplets of different viscosities.

[0081] 5) Through Figure 3 The test results of Comparative Example 2, using the same Bio TPU meltblown nonwoven fabric loading of 15g (20wt%), show that the microfiber geometric parameters are outside the limitations of this invention. In this case, the bio-based fabric can only achieve unidirectional conduction of Newtonian fluid—water. Furthermore, the two core indicators of liquid water management capability—the unidirectional transport index (R) and the comprehensive moisture-wicking and quick-drying capacity index (OMMC)—are only 289.81% and 0.8, respectively. According to the fabric unidirectional moisture-wicking performance evaluation standard (Table 2), this is only grade 2, which is relatively poor. Importantly, the fabric no longer exhibits unidirectional conduction with a 1wt% CMC-Na solution (a non-Newtonian fluid). Increasing the Bio TPU meltblown nonwoven fabric loading or the solution viscosity, such as a 2wt% CMC-Na solution, will only worsen the dissipation of viscous droplets, far from achieving unidirectional conduction.

[0082] 3. Liquid Moisture Management Capability of Functional Bio-based Fabrics - One-way Moisture Traction / Moisture Diffusion Performance Test

[0083] The functional bio-based fabrics prepared in Examples 1-4 above and the comparative example—pure cellulose fabric—were used to test the liquid moisture management capabilities of the fabrics, referring to GB / T21655.2-2019 "Evaluation of the moisture absorption and quick-drying properties of textiles—Part 2: Dynamic moisture transfer method" and AATCC 195-2009 "Liquid moisture management performance of textiles". The unidirectional transfer capability of the fabric to liquid water was divided into 1-5 levels, with level 5 being the best, and levels above 3 were considered to have a unidirectional moisture-wicking effect. The test method was to place the sample in a liquid moisture management tester (MMT) with the skin-friendly inner layer (Bio TPU meltblown nonwoven fabric-hydrophobic layer) facing upwards and the outer layer—pure cellulose fabric—facing downwards. The instrument automatically pumps a certain amount of water droplets (test solution: 9g / L sodium chloride solution) into the center of the skin-friendly layer of the test fabric. The moisture content on both sides of the fabric can be measured by the sensor. The instrument calculates and compares the mutual transfer of moisture content between the two sides of the fabric based on the change of moisture content on both sides of the fabric over time, and calculates the wetting time, water absorption rate, maximum wetting radius, diffusion rate and unidirectional transport index of the sample. The test results are shown in Table 2.

[0084] Table 2 Evaluation criteria for unidirectional moisture wicking performance of fabrics and MMT test results of fabrics in Examples 1-4 and Comparative Examples 1 and 2.

[0085]

[0086] The One-Way Moisture Transfer Index (R) and the Overall Moisture-Wicking and Quick-Drying Capability Index (OMMC) are built-in data systems of the MMT instrument. They are obtained by comprehensively evaluating various indicators on both sides of the fabric and can directly express the fabric's one-way moisture-wicking performance. The R index reflects the cumulative difference in moisture content between the two sides of the fabric. The OMMC value, as a composite liquid moisture management index, is affected by several parameters (such as relative moisture content difference, water absorption rate, and water diffusivity), representing the overall moisture management capability of the fabric. As shown in Table 2, for pure cellulose fabric (comparative example), there is almost no difference in wetting time, water absorption rate, maximum wetting radius, and diffusion rate between the inner and outer layers. Therefore, the R value of 121.68% for pure cellulose fabric corresponds to level 2, and the O value of 0.59 corresponds to level 3, meaning that pure cellulose fabric has no one-way moisture-wicking effect.

[0087] For functional bio-based fabrics loaded with Bio TPU meltblown nonwoven fabric (Examples 1-3), the wetting time of the inner layer (>4.5s) was greater than that of the corresponding outer layer (<3.0s), indicating that the inner layer absorbs moisture slowly, with most of the moisture transferred to the outer layer. The shorter wetting time of the outer layer suggests that moisture can be absorbed quickly and cannot flow back to the inner layer. The absorption rate of the inner layer of the functional fabric was <23% / s, while the absorption rate of the outer layer was >63% / s, showing a significant rate difference that greatly improves its unidirectional moisture-wicking performance. The inner layer of the bio-based fabric has a slow absorption rate and is not easily absorbed, with moisture transferred to the outer layer and rapidly absorbed there. The difference in wetting radius between the inner and outer layers indicates that moisture does not easily diffuse in the inner layer. Furthermore, with the increase of Bio TPU loading, the differences in wetting time, absorption rate, maximum wetting radius, and water diffusivity between the inner and outer layers of the functional fabric continuously increase, indicating that the overall moisture management capability of the fabric is continuously enhanced. The corresponding R values ​​are all >850%, and the OMMC values ​​are all ≥0.9, indicating that the functional bio-based fabrics (Examples 1-3) all have unidirectional moisture wicking effect and have all reached the level 5 standard. Furthermore, when the Bio TPU loading is 43wt% (Example 3), the R value and OMMC value reach excellent values ​​of 1393.82% and 0.91, respectively. Therefore, the unidirectional moisture wicking performance of this functional bio-based fabric is excellent.

[0088] 4. Characteristics of functional bio-based fabrics in unidirectional conduction of liquids of different viscosities and hydrostatic pressure resistance test

[0089] To investigate the unidirectional conductivity of functional bio-based fabrics to fluids of different viscosities, a bio-based fabric with a Bio TPU meltblown nonwoven fabric loading of 30g (33wt%) was used to conduct unidirectional conductivity tests on solutions of different viscosities. The results are as follows: Figure 4 As shown in ab. First, through... Figure 4 The difference in wetting area between the inner and outer layers indicates that water droplets hardly spread in the water-repellent inner layer, i.e., the value is less than 0.25 cm. 2 When water droplets penetrate and come into contact with the hydrophilic outer layer—the cellulose fabric—the hydrophilic properties of the numerous hydroxyl groups cause the water droplets to diffuse. Within less than 10 seconds, the maximum spreading area (greater than 2.0 cm²) is reached. 2 When the water droplets were replaced with a CMC-Na solution of a certain viscosity, the test results were as follows: Figure 4 As shown in b, for a 0.5 wt% CMC-Na aqueous solution, the droplet diffusion time is 120 s, while for 1 wt% and 2 wt% CMC-Na aqueous solutions, the diffusion times are 160 s and 1350 s, respectively. This indicates that the difference in viscous dissipation caused by the viscosity difference of the fluid affects its diffusion rate; the higher the viscosity, the slower the diffusion. Furthermore, as the fluid viscosity increases, the hysteresis effect caused by the increased viscous dissipation gradually reduces the final diffusion area.

[0090] Furthermore, for unidirectional conductive materials, impermeability is also essential. To test the impermeability of functional bio-based fabrics with different Bio TPU meltblown nonwoven fabric loadings to fluids, quasi-static fluid pressure tests were conducted. For example... Figure 4 As shown in Figure c, a 40cm long, 1.2cm inner diameter transparent polycarbonate tube is securely attached to the fabric. Deionized water is injected into the tube at a rate of 10µL / s using a micro-injection pump, while a camera records the height of the water column H in real time, and the osmosis threshold height Hp caused by hydrostatic pressure is determined. Liquid injection is immediately stopped when osmosis occurs, while recording continues to observe the decrease in H and determine the osmosis cessation height Hs. Figure 4 de represents the static breakthrough pressure values ​​of the fluid, measured when a water column is placed on the inner layer (water column in contact with hydrophilic cellulose fabric) and the outer layer (water column in contact with water-repellent Bio TPU meltblown nonwoven fabric). Figure 4 As shown in de, during this process, the critical penetration pressure from the inner layer to the outer layer is always less than the critical penetration pressure from the outer layer to the inner layer. Furthermore, as... Figure 4 As shown in d, the breakthrough pressure increases with increasing Bio TPU loading. For pure cotton fabric, the water permeability resistance is 0. The water permeability resistance of bio-based fabrics with Bio TPU loadings of 30g (33wt%) and 45g (43wt%) is above 60mmH2O. For bio-based fabrics with a Bio TPU loading of 60g (50wt%), the inner layer is essentially a water-repellent sealing film, with no fluid unidirectional permeability. Therefore, it exhibits excellent osmotic pressure resistance regardless of whether the water column contacts the inner layer (cellulose fabric) or the outer layer (Bio TPU meltblown nonwoven fabric). However, because the inner layer of the bio-based fabric, such as the Bio TPU meltblown nonwoven fabric with loadings of 15g (20wt%), 30g (33wt%), and 45g (43wt%), has good unidirectional fluid permeability, it can transfer liquid from the water column to the outer layer, as shown in the figure. Figure 4 As shown in e, its hydrostatic pressure resistance is 0. Functional bio-based fabrics with Bio TPU loadings of 30g (33wt%) and 45g (43wt%) exhibit good impermeability.

[0091] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and various changes or modifications can be made to these embodiments without departing from the principles and essence of the present invention. The scope of protection of the present invention is defined only by the appended claims.

Claims

1. A fully bio-based fabric suitable for unidirectional moisture wicking in liquids of varying viscosities, characterized in that, This fully bio-based fabric is a double-layer composite structure formed by hot-melt pressing of spunlace nonwoven fabric and meltblown nonwoven fabric. The spunlace nonwoven fabric is made of hydrophilic cellulose, and the meltblown nonwoven fabric is made of bio-based polyurethane. Among them, the fiber diameter D1 of the spunlace nonwoven fabric is 5~20 μm, the average opening size L1 in the vertical direction of the fabric is 0.1~2 μm, the thickness H1 is 0.5~1.0 mm, and the basis weight M1 is 40~80 g / m². 2 The fiber diameter D2 of meltblown nonwoven fabric is 20 μm to 60 μm, the average pore size L2 in the vertical direction of the fabric is 30 to 100 μm, the thickness H2 is 0.05 to 0.25 μm, and the basis weight M2 is 10 to 50 g / m². 2 And D2>D1, L2>L1, H1>H2, M1>M2.

2. The all-bio-based fabric for unidirectional moisture wicking of liquids of different viscosities according to claim 1, characterized in that, The bio-based polyurethane has a molecular weight (Mw) of 20,000 to 120,000 g / mol, and its prepolymer components, polyether / ester polyol and diisocyanate, are both derived from biomass materials.

3. The all-bio-based fabric for unidirectional moisture wicking of liquids of different viscosities according to claim 1, characterized in that, The hydrophilic cellulose is any one or more of wood cellulose, cotton cellulose, bamboo cellulose, hemp cellulose, and grass cellulose.

4. The method for preparing a fully bio-based fabric suitable for unidirectional moisture wicking of liquids of different viscosities, as described in any one of claims 1-3, is characterized in that... Includes the following steps: S1. Using thermoplastic bio-based polyurethane granules as raw materials, meltblown nonwoven fabric is obtained through meltblown spinning technology; S2. Using hot melt pressing technology, meltblown nonwoven fabric is melted and then bonded to spunlace nonwoven fabric under pressure to form a laminated fabric, thus obtaining a fully bio-based fabric that can be used for unidirectional moisture wicking of liquids of different viscosities.

5. The method for preparing a fully bio-based fabric suitable for unidirectional moisture wicking of liquids of different viscosities according to claim 4, characterized in that, The meltblown spinning process is as follows: After being heated, transferred and melted in a twin-screw extruder, thermoplastic bio-based polyurethane granules are extruded from the spinneret holes of the meltblown processing nozzle. The hot pressurized airflow, continuously supplied by the spinneret holes on the surface of the spinneret, is continuously blown, and the melt is stretched to form microfibers. Then, it is self-adhesive and formed on a winding machine to obtain meltblown nonwoven fabric.

6. The method for preparing a fully bio-based fabric suitable for unidirectional moisture wicking of liquids of different viscosities according to claim 5, characterized in that, The diameter of the spinneret nozzle in the meltblown processing head is 0.2~0.3mm, and the center distance between the spinnerets is 0.6~0.8mm.

7. The method for preparing a fully bio-based fabric suitable for unidirectional moisture wicking of liquids of different viscosities according to claim 4 or 5, characterized in that, The parameters for the meltblown spinning process are: hot air pressure 0.2~0.4 MPa, receiving distance of the winding machine 20~25cm, and winding speed 0.5~5 m / min.

8. The method for preparing a fully bio-based fabric suitable for unidirectional moisture wicking of liquids of different viscosities according to claim 4, characterized in that, The parameters for hot melt pressing are: temperature T is 120~180℃, pressure P is 0.05~0.5 MPa, and time t is 1 / 30min~10 min.

9. The method for preparing a fully bio-based fabric suitable for unidirectional moisture wicking of liquids of different viscosities according to claim 4, characterized in that, The processing equipment for hot melt pressing technology includes heat press machines, hot melt bonding machines, flatbed laminating machines, hot printing machines, or vacuum hot press machines.

10. The application of the all-bio-based fabric according to any one of claims 1-3, which can be used for unidirectional moisture wicking of liquids of different viscosities, in unidirectional moisture wicking of non-Newtonian fluids.

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