A micro-overlapping bionic bamboo fiber-based hollow material and its preparation method

Abstract

The present invention provides a micro-overlapping bionic bamboo fiber-based hollow material and a preparation method thereof, belonging to the field of non-woven composite materials, and is used to solve the technical problems of low directional liquid guiding ability and poor mechanical properties of fiber-based humidifying materials. The method includes the following steps: using a highly oriented polylactic acid fiber non-woven material and a viscose fiber non-woven fabric as raw materials, and preparing the bionic bamboo fiber-based hollow material through hot rolling composite and winding forming. The present invention provides a laminated structure that alternates in the thickness direction of the material and is loose inside and tight outside, and presents continuous or quasi-continuous layered micropores parallel to the length direction. This structure is beneficial to the rapid diffusion of liquid in a specific direction and the improvement of tensile strength. By changing the drawing air pressure and the volume density of the material, the moisture absorption efficiency, drying efficiency, and mechanical properties can be regulated. This provides the possibility for the application of the highly oriented fiber-based hollow material with a bionic bamboo joint structure in a humidifying core.

Description

Technical Field

[0001] The present invention relates to the field of non-woven composite materials, and particularly to a micro-overlapping bionic bamboo-joint fiber-based hollow material and a preparation method thereof. Background Art

[0002] An appropriate indoor air humidity (40 - 60%) is the core to reduce the incidence of diseases such as pharyngitis, tracheitis, and pneumonia, and to ensure human health and environmental comfort. The existing air humidity adjustment means are mainly infiltration evaporation humidifiers with a fiber-based humidifying core as the liquid guiding system. This is because the fiber-based humidifying core has the advantages of simple working principle (liquid water is transported along the fiber gaps under the induction of capillary force, wets and spreads on the fiber surface and contacts the air for evaporation, thereby achieving the improvement of air humidity), low usage cost, and wide humidifying range. The existing fiber-based humidifying cores are mostly bundles composed of cellulose fibers and polyester fibers. Although their fluffy fiber structure can achieve the transmission of liquid water, their transmission efficiency is low, the humidifying ability is weak, and their tensile strength is poor and they are easily damaged, making it difficult to meet the requirements of high transmission efficiency and long-term use in a dry environment. Therefore, there are still certain challenges in developing a new type of fiber-based humidifying core with both fast liquid guiding ability and a certain tensile strength for infiltration evaporation humidifiers.

[0003] The rapid development of biofibers such as polylactic acid (PLA) also provides a raw material basis for the technological progress and new product development of healthy and environmentally friendly infiltration evaporation humidifiers. However, the mechanical properties and liquid directional transport efficiency of pure polylactic acid fibers are low, which greatly limits the application of polylactic acid fibers in the field of liquid transport. For example, Patent No. CN115748107 discloses a preparation method of a polylactic acid ultrafine fiber non-woven material with both toughness and liquid conductivity. Polylactic acid, polyethylene glycol, and sodium dodecyl sulfate are melt-blended to form a blend polymer, and the blend polymer is made into a polylactic acid ultrafine fiber non-woven material by a melt-blown method. By adding sodium dodecyl sulfate, the crystallization rate and crystallization ability of polylactic acid are improved, and its mechanical properties and liquid conductivity characteristics are somewhat enhanced; Patent No. CN116005352A discloses a preparation method of a bionic highly oriented polylactic acid ultrafine fiber non-woven material. Mainly, polylactic acid, polyethylene glycol, and sodium dodecyl sulfate are melt-blended to form a blend melt. The blend melt forms ultrafine fibers through a spinneret die and is collected by a receiving wire mesh curtain, and then is in-situ drawn by a drawing roller to obtain a polylactic acid ultrafine fiber non-woven material. By changing the drawing ratio, the fiber diameter, diameter distribution, crystallinity, mechanical properties, and wetting properties are changed. Although this method can improve the liquid directional transport efficiency to a certain extent, the improvement is limited and it is difficult to meet the actual application requirements.

[0004] The bionics-based structural design of fiber materials provides a good reference for improving the functionality of fiber materials. Continuously or quasi-continuously highly oriented structures such as lotus root filaments, leaf veins, and bamboo nodes can efficiently achieve the directional transmission of liquids. They are highly efficient liquid transmission structures evolved by plants over hundreds of millions of years and have been used by many scholars in the design and optimization of the structures of functional fiber materials. Among them, bamboo nodes are composite materials composed of vascular bundles and parenchyma cell matrices. The gradient distribution structure of the fibers endows bamboo with excellent mechanical properties on the one hand and excellent moisture absorption and liquid transmission properties on the other hand. The highly oriented microporous structure is the key to enhancing the capillary force of liquid directional transmission and reducing the transmission resistance. Therefore, finding a new type of fiber material with both a highly oriented structure and stable mechanical properties for the preparation of fiber-based humidification cores has become a key problem that needs to be solved urgently at this stage. Summary of the Invention

[0005] Aiming at the technical problems of low liquid directional transmission efficiency and low tensile strength of fiber-based humidification cores, the present invention proposes a micro-overlapping bionic bamboo node fiber-based hollow material and its preparation method, which significantly improves the liquid directional transmission efficiency and mechanical strength of fiber-based humidification materials.

[0006] In order to achieve the above object, the technical solution of the present invention is realized as follows:

[0007] A micro-overlapping bionic bamboo node fiber-based hollow material, comprising PLA micro-nano fiber layers and viscose fiber layers arranged alternately from the inside to the outside; the PLA micro-nano fiber layers and the viscose fiber layers form a laminated structure with a loose inner and tight outer hierarchical distribution in the material thickness direction, and present continuous or quasi-continuous layered micro-pores in the parallel length direction.

[0008] The PLA micro-nano fiber layer is a polylactic acid fiber nonwoven material, with an average fiber diameter of 4.8 - 8.6 μm and a pore size of 36.1 - 58.4 μm.

[0009] The viscose fiber layer is a viscose fiber nonwoven fabric with a basis weight of 97.3 g / m 2 and a thickness of 0.51 mm.

[0010] The preparation method of the micro-overlapping bionic bamboo node fiber-based hollow material is characterized in that the steps are as follows:

[0011] (1) Meltblowing and in-situ drawing to prepare a highly oriented polylactic acid fiber nonwoven material: Mix polylactic acid (PLA), secondary alkyl sulfonate (SAS), and polyethylene glycol (PEG) evenly to obtain a blend polymer, add it to a screw extruder for blending to form a blend melt, enter a metering pump after passing through a filter, and send the blend melt to a spinneret die after passing through the metering pump. The fibers are deposited on a receiving screen curtain by hot air drawing, and then in-situ drawing is carried out by a drawing roller to obtain a highly oriented polylactic acid fiber nonwoven material.

[0012] During the above meltblown forming process, after the PLA melt is extruded from the spinneret, it is refined into fibers under the action of high-speed air flow drawing, and accumulates on the forming screen below the spinneret to form a PLA random fiber web with a certain temperature. Enhancing the high-speed air flow pressure can effectively increase the air flow drawing force, which is the main method for adjusting the fiber fineness. Therefore, during the preparation process of the polylactic acid fiber nonwoven material, polylactic acid fiber nonwoven materials with various fiber finenesses are obtained by adjusting the drawing air pressure.

[0013] Furthermore, during the winding process of the PLA random fiber web by the winder, due to the low glass transition temperature (~60 °C) of the PLA polymer and the winding tension, in-situ drawing occurs to form a polylactic acid fiber nonwoven material with a highly oriented arrangement. Adjusting the speed ratio between the winder and the forming screen can change the in-situ drawing tension, which is the core for controlling the fiber orientation degree. Therefore, during the drawing preparation process of the highly oriented polylactic acid fiber nonwoven material, the speed ratio is set to 1.8.

[0014] (2) Preparation of viscose fiber nonwoven fabric: Using viscose fiber as the raw material, a viscose fiber web is obtained by carding with a carding machine, and then the waterjet process is used to reinforce the carded web to prepare the viscose fiber nonwoven fabric.

[0015] (3) Laminating and compounding of the bionic bamboo fiber-based hollow material: The polylactic acid nonwoven material in step (1) and the viscose fiber membrane in step (2) are laminated up and down and hot-rolled and compounded to prepare a two-layer structured PLA / CEL nonwoven composite material.

[0016] (4) Winding and fixing: Cut a rectangular material with a length of 170 cm and a width of 100 mm from the polylactic acid / viscose fiber nonwoven composite material in step (3) along the machine direction, wind the material along the width direction and place it in die tubes with inner diameters of 8 mm, 9 mm, 10 mm, 11 mm, and 12 mm respectively for fixing to obtain the micro-overlapping bionic bamboo fiber-based hollow material.

[0017] In step (1), the mass ratio of polylactic acid, secondary alkyl sulfonate, and polyethylene glycol is (94 - 97):(2 - 3):(1 - 3).

[0018] The process parameters of meltblowing in step (1) are as follows: the temperature of the first zone of the screw in the screw extruder is 150 - 170 °C, the temperature of the second zone is 230 - 250 °C, the temperature of the third zone is 270 - 290 °C, the temperature of the metering pump is 270 - 290 °C, the rotation speed of the metering pump is 2.7 r / min, and the die head temperature is 260 - 280 °C; the pipeline temperature is 270 - 290 °C, the hot air temperature is 270 - 290 °C, and the drawing air pressure is 24 - 40 Kpa.

[0019] In step (2), the viscose fiber has a length of 38 mm and a fineness of 1.38 denier, and is purchased from Xingda Chemical Fiber Co., Ltd., Tangshan Sanyou Group, China.

[0020] The hot rolling process parameters in step (3) are as follows: the hot rolling temperature is 110 °C, the hot rolling pressure is 2.3 MPa, and the hot rolling speed is 2 m / min.

[0021] In step (4), the bulk density of the fiber-based humidifying material is 1.1 - 1.8 g / cm 3 .

[0022] Advantages of the present invention:

[0023] (1) The cylindrical shape formed after winding and molding of the polylactic acid / viscose fiber nonwoven composite material has a highly similar structure to bamboo nodes. It forms a laminated structure with a loose inner and tight outer layer distribution in an alternating arrangement in the thickness direction of the sample, and has continuous or quasi-continuous layered micropore distribution parallel to the length direction, which is beneficial to improving the liquid transmission ability and maintaining mechanical properties.

[0024] (2) By changing the draft air pressure and bulk density, the tensile fracture strength of the micro-overlapped bionic bamboo node fiber-based hollow material can be changed. When the draft air pressure increases from 24 kPa to 40 kPa, the tensile fracture strength increases from 262.2 N to 346.4 N; since the number of fibers per unit volume increases with the increase of the bulk density, the bonding points between fibers increase, and the fibers are more evenly stressed, which helps to resist external forces and increase the tensile fracture strength. When the bulk density of the sample increases from 1.1 g / cm 3 to 1.8 g / cm 3 , the tensile fracture strength increases from 255.2 N to 286.0 N, an increase of about 12.1%.

[0025] (3) With the increase of the draft air pressure, the liquid holding rate of the fiber-based humidifying material decreases, while the liquid retention rate, liquid absorption rate, and drying rate all show an increasing trend. When the draft air pressure is 40 kPa, the liquid holding rate of the sample decreases to 465.5%, the liquid retention rate reaches 386.0%, the liquid absorption rate increases to 108.4 mg / s, and the drying rate increases to 0.69 mL / hour.

[0026] (4) With the decrease of the bulk density, the liquid holding rate, liquid retention rate, drying rate, and liquid absorption rate of the fiber-based humidifying material all show an increasing trend. When the bulk density is 1.1 g / cm 3 , the liquid holding rate of the sample reaches 489.0%, the liquid retention rate reaches 382.5%, the liquid absorption rate increases to 112.4 mg / s, and the drying rate increases to 1.03 mL / hour.

[0027] (5) With a draft air pressure of 36 kPa and a bulk density of 1.8 g / cm 3 of the sample as the humidification core, the humidification capacity of this humidification core is 78 mL / h, meeting the standard requirements of the single-port rated humidification capacity (>70 mL / h) of this commercial humidifier. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following-described drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0029] Figure 1 It is a schematic diagram of the preparation process of a micro-overlapping bionic bamboo joint fiber-based hollow material according to an embodiment of the present invention.

[0030] Figure 2 They are scanning electron microscope images of the cross-section of a bamboo joint (a), the cross-section of the micro-overlapping bionic bamboo joint fiber-based hollow material prepared in Example 1 (b), and the surface of the polylactic acid micro-nano fiber layer (c).

[0031] Figure 3 It is the fiber orientation angle distribution of the polylactic acid fiber nonwoven material prepared in Example 1 of the present invention.

[0032] Figure 4 It is the fiber diameter and pore size distribution of the PLA fiber nonwoven materials prepared in Examples 1-5 of the present invention under different draft air pressures.

[0033] Figure 5 They are the liquid absorption properties of the micro-overlapping bionic bamboo joint fiber-based hollow materials prepared in Examples 1-5 of the present invention under different draft air pressures: (a) liquid absorption curve; (b) liquid absorption rate of the sample.

[0034] Figure 6 They are the liquid absorption properties of the bionic bamboo joint fiber-based hollow materials with different bulk densities prepared in Examples 4, 6-9 of the present invention: (a) liquid absorption curve; (b) liquid absorption rate of the sample.

[0035] Figure 7 It is the moisture absorption curve of the polylactic acid fiber-based humidification material prepared in Comparative Example 1 of the present invention.

[0036] Figure 8 They are the liquid retention rate and liquid holding rate of the micro-overlapping bionic bamboo joint fiber-based hollow materials prepared in Examples 1-5 of the present invention under different draft air pressures.

[0037] Figure 9For Example 4, 6 - 9 of the present invention, the liquid - holding rate and liquid - retaining rate of the micro - overlapping bionic bamboo - joint fiber - based hollow materials with different volume densities are shown.

[0038] Figure 10 For the micro - overlapping bionic bamboo - joint fiber - based hollow materials prepared in Examples 1 - 5 of the present invention, the drying performance under different draft air pressures: (a) drying curve; (a) drying rate.

[0039] Figure 11 For the micro - overlapping bionic bamboo - joint fiber - based hollow materials with different volume densities prepared in Examples 4, 6 - 9 of the present invention, the drying performance: (a) drying curve; (a) drying rate.

[0040] Figure 12 The drying curve of the polylactic acid fiber - based humidifying material prepared in Comparative Example 1 of the present invention.

[0041] Figure 13 The tensile fracture curves of the micro - overlapping bionic bamboo - joint fiber - based hollow materials prepared in the present invention: (a) different draft air pressures; (b) different bulk densities.

[0042] Figure 14 The tensile fracture curve of the polylactic acid fiber - based humidifying material prepared in Comparative Example 1 of the present invention.

[0043] Figure 15 The example diagram of the application of the micro - overlapping bionic bamboo - joint fiber - based hollow materials prepared in the present invention to a humidifier.

[0044] Figure 16 The water consumption record diagram of the humidifying core prepared in Example 6 of the present invention. Detailed implementation manners

[0045] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0046] Example 1

[0047] The preparation method of a micro - overlapping bionic bamboo - joint fiber - based hollow material in this example is shown in the following Figure 1 figure, and the steps are as follows:

[0048] (1) 94.2% polylactic acid polymer chips, 2.8% secondary alkyl sulfonate, and 3% polyethylene glycol are fully mixed and then added to a screw extruder. They are melted by heating and extrusion, filtered through a filter to remove impurities, and then enter a metering pump. The melt is accurately metered by the metering pump and sent to a die head, flowing out through spinneret holes, and finally refined into fibers by the action of high-speed air flow stretching. It is aggregated into a PLA random fiber web with a certain temperature on a forming screen below the spinneret plate, and then a polylactic acid fiber nonwoven material is obtained through in-situ stretching. Among them, the temperature of the first zone of the screw is 160 °C, the temperature of the second zone of the screw is 240 °C, the temperature of the third zone of the screw is 280 °C, the temperature of the die head is 270 °C, the temperature of the hot air is 280 °C, the temperature of the pipeline is 280 °C, the stretching air pressure is 24 kPa, the temperature of the metering pump is 280 °C, the rotation speed of the metering pump is 2.7 r / min, and the stretching ratio is 1.8.

[0049] (2) Viscose fibers with a length of 38 mm and a fineness of 1.38 denier are opened, mixed and carded, stacked into a fiber web, stretched and rectified. After waterjet reinforcement and drying of the fiber web using high-pressure water flow, a viscose fiber nonwoven fabric with a weight of 97.3 g / m 2 and a thickness of 0.51 mm is obtained.

[0050] (3) The highly oriented polylactic acid fiber nonwoven material and the viscose fiber nonwoven fabric are stacked up and down and hot-rolled and compounded to prepare a two-layer structured polylactic acid / viscose fiber nonwoven composite material. Among them, the hot-rolling temperature is 110 °C, the hot-rolling pressure is 2.5 MPa, and the hot-rolling speed is 2 m / min.

[0051] (4) The obtained two-layer structured polylactic acid / viscose fiber nonwoven composite material is cut into a rectangular material with a length of 170 cm and a width of 100 mm along the machine direction, and then wound along the width direction and placed in a mold tube with an inner diameter of 9 mm for fixation, forming a micro-overlapping bionic bamboo joint fiber-based hollow material with a bulk density of 1.6 g / cm 3 .

[0052] The morphology and structure of the bamboo joints, the bionic bamboo joint fiber-based hollow material of this example, and the PLA micro-nano fiber layer are tested by a JSM-IT 200 type scanning electron microscope (ZEISS, Germany), and the results are as Figure 2 shown. Figure 2 are the scanning electron microscope images of the cross-section of the bamboo joint, the cross-section of the bionic bamboo joint fiber-based hollow material, and the surface of the PLA micro-nano fiber layer, Figure 2Figure a shows a scanning electron microscope image of the cross-section of a bamboo node. It can be seen from the figure that the cross-section of the bamboo node is a cylindrical thin-walled hollow structure with a uniform distribution, and there are parallel micropores (vascular bundles) that are hierarchically distributed in the wall thickness direction and gradually decrease from the inside to the outside. The parallel micropores extend along the length of the bamboo to form a highly oriented arrangement. On the one hand, it provides a channel for the liquid transmission inside the bamboo wall, and on the other hand, it ensures the structural strength and stability in the length direction of the bamboo; Figure 2 Figure b shows a cross-sectional electron microscope image of the bionic bamboo node fiber-based hollow material sample. It can be found that the PLA micro-nano fiber layer and the viscose fiber layer are alternately arranged in the thickness direction of the sample to form a laminated structure with a loose inside and a tight outside in a hierarchical distribution; Figure 2 Figure c shows the surface morphology of the PLA micro-nano fiber layer. Due to the in-situ drawing effect, the PLA fibers formed by meltblowing are highly oriented along the machine direction.

[0053] The fiber orientation angle distribution was measured using ImagineJ software, and the results are as Figure 3 shown. The fiber orientation angle is defined as the angle between the fiber length direction and the equipment output direction. Figure 3 is the structural characteristic of the PLA micro-nano fiber material, Figure 3 is the fiber orientation angle distribution curve graph. The distribution frequency of the fiber orientation angle between -10° and 10° (i.e., along the machine direction) is 46.1%, indicating that the tube formed after the winding molding of the polylactic acid / viscose fiber nonwoven composite material has a highly similar structure to the bamboo node, and both have continuous or quasi-continuous layered micro-pore distributions parallel to the length direction, which provides an excellent porous structure for the improvement of liquid transmission ability and the maintenance of mechanical properties.

[0054] Example 2

[0055] A preparation method of a micro-overlapping bionic bamboo node fiber-based hollow material in this example is as follows:

[0056] (1) 94.2% polylactic acid polymer chips, 2.8% secondary alkyl sulfonate, and 3% polyethylene glycol are fully mixed and then added to a screw extruder. After heating and extrusion, they are melted, and then the impurities are filtered through a filter, and then enter a metering pump. The melt is accurately metered by the metering pump and sent to a die head, and flows out through a spinneret hole. Finally, it is refined into fibers by the high-speed air flow drawing effect and aggregated into a PLA random fiber web with a certain temperature on the forming curtain below the spinneret plate, and then a polylactic acid fiber nonwoven material is obtained through in-situ drawing. Among them, the temperature of the first zone of the screw is 160 °C, the temperature of the second zone of the screw is 240 °C, the temperature of the third zone of the screw is 280 °C, the temperature of the die head is 270 °C, the temperature of the hot air is 280 °C, the temperature of the pipeline is 280 °C, the drawing air pressure is 28 kPa, the temperature of the metering pump is 280 °C, the rotation speed of the metering pump is 2.7 r / min, and the drawing ratio is 1.8.

[0057] (2) Open up, mix and card viscose fibers with a length of 38 mm and a fineness of 1.38 denier, stack them into a fiber web, draw and rectify. After hydroentangling and drying the fiber web with high-pressure water flow, a viscose fiber non-woven fabric with a weight of 97.3 g / m 2 and a thickness of 0.51 mm is obtained.

[0058] (3) Stack the highly oriented polylactic acid fiber non-woven material and the viscose fiber non-woven fabric up and down and perform hot rolling and lamination to prepare a two-layer structure of polylactic acid / viscose fiber non-woven composite material. Among them, the hot rolling temperature is 110 °C, the hot rolling pressure is 2.5 MPa, and the hot rolling speed is 2 m / min.

[0059] (4) Cut a rectangular material with a length of 170 cm and a width of 100 mm from the obtained two-layer structure of polylactic acid / viscose fiber non-woven composite material along the machine direction, then wind the material along the width direction and place it in a mold tube with an inner diameter of 9 mm for fixation to form a micro-overlapping bionic bamboo joint fiber-based hollow material with a volume density of 1.6 g / cm 3 .

[0060] Example 3

[0061] A preparation method of a micro-overlapping bionic bamboo joint fiber-based hollow material in this example is as follows:

[0062] (1) Thoroughly mix 94.2% polylactic acid polymer chips, 2.8% secondary alkyl sulfonate and 3% polyethylene glycol, add them to a screw extruder, melt them by heating and extrusion, filter impurities through a filter, then enter a metering pump. The melt is accurately metered by the metering pump and sent to a die head, and flows out through a spinneret hole. Finally, it is refined into fibers by the stretching action of high-speed air flow and aggregated into a PLA random fiber web with a certain temperature on a forming curtain below the spinneret plate, and then a polylactic acid fiber non-woven material is obtained through in-situ drawing. Among them, the temperature of the first zone of the screw is 160 °C, the temperature of the second zone of the screw is 240 °C, the temperature of the third zone of the screw is 280 °C, the temperature of the die head is 270 °C, the temperature of the hot air is 280 °C, the temperature of the pipeline is 280 °C, the stretching air pressure is 32 kPa, the temperature of the metering pump is 280 °C, the rotation speed of the metering pump is 2.7 r / min, and the stretching ratio is 1.8.

[0063] (2) Open up, mix and card viscose fibers with a length of 38 mm and a fineness of 1.38 denier, stack them into a fiber web, draw and rectify. After hydroentangling and drying the fiber web with high-pressure water flow, a viscose fiber non-woven fabric with a weight of 97.3 g / m 2 and a thickness of 0.51 mm is obtained.

[0064] (3) Stack the high - orientation arranged polylactic acid micro - and nano - fiber non - woven material and viscose fiber non - woven fabric up and down, and then perform hot - rolling compounding to prepare a two - layer polylactic acid / viscose fiber non - woven composite material. Among them, the hot - rolling temperature is 110 °C, the hot - rolling pressure is 2.5 MPa, and the hot - rolling speed is 2 m / min.

[0065] (4) Cut out a rectangular material with a length of 170 cm and a width of 100 mm from the obtained two - layer polylactic acid / viscose fiber non - woven composite material along the machine direction, then wind the material along the width direction and fix it in a die tube with an inner diameter of 9 mm to form a micro - overlapping bionic bamboo - joint fiber - based hollow material with a bulk density of 1.6 g / cm 3 ³.

[0066] Example 4

[0067] A preparation method of a micro - overlapping bionic bamboo - joint fiber - based hollow material in this example is as follows:

[0068] (1) Thoroughly mix 94.2% polylactic acid polymer chips, 2.8% secondary alkyl sulfonate, and 3% polyethylene glycol, then add them to a screw extruder, melt them by heating and extrusion, filter impurities through a filter, then enter a metering pump. The melt is accurately metered by the metering pump and sent to a die head, and flows out through a spinneret hole. Finally, it is refined into fibers under the action of high - speed air current drawing and aggregated into a PLA random fiber web with a certain temperature on a forming curtain below the spinneret plate, and then an in - situ drawing is carried out to obtain a polylactic acid fiber non - woven material. Among them, the temperature of the first zone of the screw is 160 °C, the temperature of the second zone of the screw is 240 °C, the temperature of the third zone of the screw is 280 °C, the temperature of the die head is 270 °C, the temperature of the hot air is 280 °C, the temperature of the pipeline is 280 °C, the drawing air pressure is 36 kPa, the temperature of the metering pump is 280 °C, the rotation speed of the metering pump is 2.7 r / min, and the drawing ratio is 1.8.

[0069] (2) Open, mix, card, stack, draw, and rectify viscose fibers with a length of 38 mm and a fineness of 1.38 denier, and then use high - pressure water jets to reinforce and dry the fiber web to obtain a viscose fiber non - woven fabric with a basis weight of 97.3 g / m 2 ² and a thickness of 0.51 mm.

[0070] (3) Stack the high - orientation arranged polylactic acid micro - and nano - fiber non - woven material and viscose fiber non - woven fabric up and down, and then perform hot - rolling compounding to prepare a two - layer polylactic acid / viscose fiber non - woven composite material. Among them, the hot - rolling temperature is 110 °C, the hot - rolling pressure is 2.5 MPa, and the hot - rolling speed is 2 m / min.

[0071] (4) Cut out a rectangular material with a length of 170 cm and a width of 100 mm from the obtained two-layer polylactic acid / viscose fiber nonwoven composite along the machine direction, then wind the material along the width direction and fix it in a die tube with an inner diameter of 9 mm to form a micro-overlapped bionic bamboo fiber-based hollow material with a bulk density of 1.6 g / cm 3 of the micro-overlapped bionic bamboo fiber-based hollow material.

[0072] Example 5

[0073] A preparation method of a micro-overlapped bionic bamboo fiber-based hollow material in this example is as follows:

[0074] (1) Thoroughly mix 94.2% polylactic acid polymer chips, 2.8% secondary alkyl sulfonate, and 3% polyethylene glycol, then add them to a screw extruder, melt them by heating and extrusion, filter impurities through a filter, then enter a metering pump. The melt is accurately metered by the metering pump and sent to a die head, and flows out through a spinneret hole. Finally, it is refined into fibers by the action of high-speed air flow drawing and aggregated into a PLA random fiber web with a certain temperature on a forming curtain below the spinneret plate, and then a polylactic acid fiber nonwoven material is obtained through in-situ drawing. Among them, the temperature of the first zone of the screw is 160 °C, the temperature of the second zone of the screw is 240 °C, the temperature of the third zone of the screw is 280 °C, the temperature of the die head is 270 °C, the temperature of the hot air is 280 °C, the temperature of the pipeline is 280 °C, the drawing air pressure is 40 kPa, the temperature of the metering pump is 280 °C, the rotation speed of the metering pump is 2.7 r / min, and the drawing ratio is 1.8.

[0075] (2) Open, mix and card the viscose fibers with a length of 38 mm and a fineness of 1.38 denier, stack them into a fiber web, draw and rectify, and then use high-pressure water flow to hydroentangle and dry the fiber web to obtain a viscose fiber nonwoven fabric with a weight of 97.3 g / m 2 and a thickness of 0.51 mm.

[0076] (3) Stack the highly oriented polylactic acid micro-nano fiber nonwoven material and the viscose fiber nonwoven fabric up and down and perform hot rolling composite to prepare a two-layer polylactic acid / viscose fiber nonwoven composite. Among them, the hot rolling temperature is 110 °C, the hot rolling pressure is 2.5 MPa, and the hot rolling speed is 2 m / min.

[0077] (4) Cut out a rectangular material with a length of 170 cm and a width of 100 mm from the obtained two-layer polylactic acid / viscose fiber nonwoven composite along the machine direction, then wind the material along the width direction and fix it in a die tube with an inner diameter of 9 mm to form a micro-overlapped bionic bamboo fiber-based hollow material with a bulk density of 1.6 g / cm 3 of the micro-overlapped bionic bamboo fiber-based hollow material.

[0078] Example 6

[0079] A preparation method of a micro-overlapping bionic bamboo-joint fiber-based hollow material according to this embodiment is as follows:

[0080] (1) 94.2% polylactic acid polymer chips, 2.8% secondary alkyl sulfonate, and 3% polyethylene glycol are fully mixed and then added to a screw extruder. After being heated and extruded to melt, impurities are filtered through a filter, and then it enters a metering pump. The melt is accurately metered by the metering pump and sent to a die head, and flows out through a spinneret hole. Finally, it is refined into fibers under the action of high-speed air current stretching and aggregates into a PLA random fiber web with a certain temperature on a forming curtain below the spinneret plate. Then, a polylactic acid fiber nonwoven material is obtained through in-situ stretching. Among them, the temperature of the first zone of the screw is 160 °C, the temperature of the second zone of the screw is 240 °C, the temperature of the third zone of the screw is 280 °C, the temperature of the die head is 270 °C, the temperature of the hot air is 280 °C, the temperature of the pipeline is 280 °C, the stretching air pressure is 36 kPa, the temperature of the metering pump is 280 °C, the rotation speed of the metering pump is 2.7 r / min, and the stretching ratio is 1.8.

[0081] (2) Viscose fibers with a length of 38 mm and a fineness of 1.38 denier are opened, mixed and carded, stacked into a fiber web, stretched, and rectified. After being hydroentangled and dried with high-pressure water flow on the fiber web, a viscose fiber nonwoven fabric with a weight of 97.3 g / m 2 and a thickness of 0.51 mm is obtained.

[0082] (3) The highly oriented polylactic acid micro-nano fiber nonwoven material and the viscose fiber nonwoven fabric are stacked up and down and hot-rolled and compounded to prepare a two-layer structure of polylactic acid / viscose fiber nonwoven composite material. Among them, the hot-rolling temperature is 110 °C, the hot-rolling pressure is 2.5 MPa, and the hot-rolling speed is 2 m / min.

[0083] (4) The obtained two-layer structure of polylactic acid / viscose fiber nonwoven composite material is cut into a rectangular material with a length of 170 cm and a width of 100 mm along the machine direction, and then the material is wound along the width direction and placed in a mold tube with an inner diameter of 8 mm and fixed to form a micro-overlapping bionic bamboo-joint fiber-based hollow material with a bulk density of 1.8 g / cm 3 .

[0084] Example 7

[0085] A preparation method of a micro-overlapping bionic bamboo-joint fiber-based hollow material according to this embodiment is as follows:

[0086] (1) 94.2% polylactic acid polymer chips, 2.8% secondary alkyl sulfonate, and 3% polyethylene glycol are fully mixed and then added to a screw extruder. They are melted by heating and extrusion, filtered through a filter to remove impurities, and then enter a metering pump. The melt is accurately metered by the metering pump and sent to a die head, flowing out through spinneret holes, and finally refined into fibers by the stretching action of high-speed air flow, and aggregated into a PLA random fiber web with a certain temperature on a forming screen below the spinneret plate. Then, a polylactic acid fiber nonwoven material is obtained through in-situ stretching. Among them, the temperature of the first zone of the screw is 160 °C, the temperature of the second zone of the screw is 240 °C, the temperature of the third zone of the screw is 280 °C, the temperature of the die head is 270 °C, the temperature of the hot air is 280 °C, the temperature of the pipeline is 280 °C, the stretching air pressure is 36 kPa, the temperature of the metering pump is 280 °C, the rotation speed of the metering pump is 2.7 r / min, and the stretching ratio is 1.8.

[0087] (2) Viscose fibers with a length of 38 mm and a fineness of 1.38 denier are opened, mixed and carded, stacked into a fiber web, stretched and rectified, and then the fiber web is hydroentangled and dried using high-pressure water flow to obtain a viscose fiber nonwoven fabric with a weight of 97.3 g / m 2 , and a thickness of 0.51 mm.

[0088] (3) The highly oriented polylactic acid micro-nano fiber nonwoven material and the viscose fiber nonwoven fabric are stacked up and down and hot-rolled and compounded to prepare a two-layer structured polylactic acid / viscose fiber nonwoven composite material. Among them, the hot-rolling temperature is 110 °C, the hot-rolling pressure is 2.5 MPa, and the hot-rolling speed is 2 m / min.

[0089] (4) The obtained two-layer structured polylactic acid / viscose fiber nonwoven composite material is cut into a rectangular material with a length of 170 cm and a width of 100 mm along the machine direction, and then the material is wound along the width direction and placed and fixed in a mold tube with an inner diameter of 10 mm to form a micro-overlapping bionic bamboo-joint fiber-based hollow material with a bulk density of 1.4 g / cm 3 .

[0090] Example 8

[0091] A preparation method of a micro-overlapping bionic bamboo-joint fiber-based hollow material in this example is as follows:

[0092] (1) 94.2% polylactic acid polymer chips, 2.8% secondary alkyl sulfonate, and 3% polyethylene glycol are fully mixed and then added to a screw extruder. They are melted by heating and extrusion, filtered through a filter to remove impurities, and then enter a metering pump. The melt is accurately metered by the metering pump and sent to a die head, flowing out through spinneret holes, and finally refined into fibers by the stretching effect of high-speed air flow, and aggregated into a PLA random fiber web with a certain temperature on a forming screen below the spinneret plate. Then, a polylactic acid fiber nonwoven material is obtained through in-situ stretching. Among them, the temperature of the first zone of the screw is 160 °C, the temperature of the second zone of the screw is 240 °C, the temperature of the third zone of the screw is 280 °C, the temperature of the die head is 270 °C, the temperature of the hot air is 280 °C, the temperature of the pipeline is 280 °C, the stretching air pressure is 36 kPa, the temperature of the metering pump is 280 °C, the rotation speed of the metering pump is 2.7 r / min, and the stretching ratio is 1.8.

[0093] (2) Viscose fibers with a length of 38 mm and a fineness of 1.38 denier are opened, mixed and carded, stacked into a fiber web, stretched, and rectified. After waterjet reinforcement and drying of the fiber web using high-pressure water flow, a viscose fiber nonwoven fabric with a weight of 97.3 g / m 2 and a thickness of 0.51 mm is obtained.

[0094] (3) The highly oriented polylactic acid micro-nano fiber nonwoven material and the viscose fiber nonwoven fabric are stacked up and down and hot-rolled and compounded to prepare a two-layer structured polylactic acid / viscose fiber nonwoven composite material. Among them, the hot-rolling temperature is 110 °C, the hot-rolling pressure is 2.5 MPa, and the hot-rolling speed is 2 m / min.

[0095] (4) The obtained two-layer structured polylactic acid / viscose fiber nonwoven composite material is cut into a rectangular material with a length of 170 cm and a width of 100 mm along the machine direction, and then wound along the width direction and placed in a mold tube with an inner diameter of 11 mm for fixation to form a micro-overlapping bionic bamboo-joint fiber-based hollow material with a bulk density of 1.2 g / cm 3 .

[0096] Example 9

[0097] A method for preparing a micro-overlapping bionic bamboo-joint fiber-based hollow material in this example is as follows:

[0098] (1) 94.2% of polylactic acid polymer chips, 2.8% of secondary alkyl sulfonate, and 3% of polyethylene glycol are fully mixed and then added to a screw extruder. After heating and extrusion to melt, impurities are filtered through a filter, and then it enters a metering pump. The melt is accurately metered by the metering pump and sent to a die head, flowing out through spinneret holes, and finally refined into fibers under the action of high-speed air flow drawing, and aggregated into a PLA random fiber web with a certain temperature on a forming screen below the spinneret plate. Then, a polylactic acid fiber nonwoven material is obtained through in-situ drawing. Among them, the temperature of the first zone of the screw is 160 °C, the temperature of the second zone of the screw is 240 °C, the temperature of the third zone of the screw is 280 °C, the temperature of the die head is 270 °C, the temperature of the hot air is 280 °C, the temperature of the pipeline is 280 °C, the drawing air pressure is 36 kPa, the temperature of the metering pump is 280 °C, the rotation speed of the metering pump is 2.7 r / min, and the drawing ratio is 1.8.

[0099] (2) Viscose fibers with a length of 38 mm and a fineness of 1.38 denier are opened, mixed and carded, stacked into a fiber web, drawn, and rectified. After water-jet reinforcement and drying of the fiber web with high-pressure water flow, a viscose fiber nonwoven fabric with a weight of 97.3 g / m 2 and a thickness of 0.51 mm is obtained.

[0100] (3) The polylactic acid fiber nonwoven material with high-directional arrangement and the viscose fiber nonwoven fabric are stacked up and down and hot-rolled and compounded to prepare a two-layer-structured polylactic acid / viscose fiber nonwoven composite material. Among them, the hot-rolling temperature is 110 °C, the hot-rolling pressure is 2.5 MPa, and the hot-rolling speed is 2 m / min.

[0101] (4) The obtained two-layer-structured polylactic acid / viscose fiber nonwoven composite material is cut into a rectangular material with a length of 170 cm and a width of 100 mm along the machine direction, and then the material is wound along the width direction and fixed in a mold tube with an inner diameter of 12 mm to form a micro-overlapping bionic bamboo-joint fiber-based hollow material with a bulk density of 1.1 g / cm 3 .

[0102] Example 10

[0103] A preparation method of a micro-overlapping bionic bamboo-joint fiber-based hollow material in this example is as follows:

[0104] (1) 97% polylactic acid polymer chips, 2% secondary alkyl sulfonate, and 1% polyethylene glycol are fully and evenly mixed and then added to a screw extruder. They are melted by heating and extrusion, filtered through a filter to remove impurities, and then enter a metering pump. The melt is accurately metered by the metering pump and sent to a die head, flowing out through a spinneret hole. Finally, it is refined into fibers by the action of high-speed air flow drawing and aggregated into a PLA random fiber web with a certain temperature on a forming screen below the spinneret plate. Then, a polylactic acid fiber nonwoven material is obtained through in-situ drawing. Among them, the temperature of the first zone of the screw is 150 °C, the temperature of the second zone of the screw is 230 °C, the temperature of the third zone of the screw is 270 °C, the temperature of the die head is 260 °C, the temperature of the hot air is 270 °C, the temperature of the pipeline is 270 °C, the drawing air pressure is 24 kPa, the temperature of the metering pump is 270 °C, the rotation speed of the metering pump is 2.7 r / min, and the drawing ratio is 1.8.

[0105] (2) Viscose fibers with a length of 38 mm and a fineness of 1.38 denier are opened, mixed and carded, stacked into a fiber web, drawn, and leveled. After water-jet reinforcement and drying of the fiber web using high-pressure water flow, a viscose fiber nonwoven fabric with a weight of 97.3 g / m 2 and a thickness of 0.51 mm is obtained.

[0106] (3) The highly oriented polylactic acid fiber nonwoven material and the viscose fiber nonwoven fabric are stacked up and down and hot-rolled and compounded to prepare a two-layer-structured polylactic acid / viscose fiber nonwoven composite material. Among them, the hot-rolling temperature is 110 °C, the hot-rolling pressure is 2.5 MPa, and the hot-rolling speed is 2 m / min.

[0107] (4) The obtained two-layer-structured polylactic acid / viscose fiber nonwoven composite material is cut into a rectangular material with a length of 170 cm and a width of 100 mm along the machine direction, and then wound along the width direction and placed in a mold tube with an inner diameter of 9 mm for fixation, forming a micro-overlapping bionic bamboo-joint fiber-based hollow material with a bulk density of 1.6 g / cm 3 .

[0108] Example 11

[0109] A method for preparing a micro-overlapping bionic bamboo-joint fiber-based hollow material in this example is as follows:

[0110] (1) 94% polylactic acid polymer chips, 3% secondary alkyl sulfonate, and 3% polyethylene glycol are fully mixed and then added to a screw extruder. They are melted by heating and extrusion, filtered through a filter to remove impurities, and then enter a metering pump. The melt is accurately metered by the metering pump and sent to a die head, flowing out through spinneret holes. Finally, it is refined into fibers by the stretching action of high-speed air flow and aggregated into a PLA random fiber web with a certain temperature on a forming screen below the spinneret plate. Then, a polylactic acid fiber nonwoven material is obtained through in-situ stretching. Among them, the temperature of the first zone of the screw is 170 °C, the temperature of the second zone of the screw is 250 °C, the temperature of the third zone of the screw is 290 °C, the temperature of the die head is 280 °C, the temperature of the hot air is 290 °C, the temperature of the pipeline is 290 °C, the stretching air pressure is 24 kPa, the temperature of the metering pump is 290 °C, the rotation speed of the metering pump is 2.7 r / min, and the stretching ratio is 1.8.

[0111] (2) Viscose fibers with a length of 38 mm and a fineness of 1.38 denier are opened, mixed, carded, stacked into a fiber web, stretched, and rectified. After being hydroentangled and dried with high-pressure water flow on the fiber web, a viscose fiber nonwoven fabric with a weight of 97.3 g / m 2 and a thickness of 0.51 mm is obtained.

[0112] (3) The polylactic acid fiber nonwoven material with high directional arrangement and the viscose fiber nonwoven fabric are stacked up and down and hot-rolled and compounded to prepare a two-layer structured polylactic acid / viscose fiber nonwoven composite material. Among them, the hot-rolling temperature is 110 °C, the hot-rolling pressure is 2.5 MPa, and the hot-rolling speed is 2 m / min.

[0113] (4) The obtained two-layer structured polylactic acid / viscose fiber nonwoven composite material is cut into a rectangular material with a length of 170 cm and a width of 100 mm along the machine direction, and then wound along the width direction and placed in a mold tube with an inner diameter of 9 mm for fixation to form a micro-overlapping bionic bamboo-joint fiber-based hollow material with a bulk density of 1.6 g / cm 3 .

[0114] Comparative Example 1

[0115] (1) 94.2% polylactic acid polymer chips, 2.8% secondary alkyl sulfonate, and 3% polyethylene glycol are fully mixed and then added to a screw extruder. They are melted by heating and extrusion, filtered through a filter to remove impurities, and then enter a metering pump. The melt is accurately metered by the metering pump and sent to a die head, flowing out through a spinneret hole, and finally refined into fibers by the stretching effect of high-speed air flow, and aggregated into a PLA random fiber web with a certain temperature on a forming screen below the spinneret plate, and then a polylactic acid fiber nonwoven material is obtained through in-situ stretching. Among them, the temperature of the first zone of the screw is 160 °C, the temperature of the second zone of the screw is 240 °C, the temperature of the third zone of the screw is 280 °C, the temperature of the die head is 270 °C, the temperature of the hot air is 280 °C, the temperature of the pipeline is 280 °C, the stretching air pressure is 24 kPa, the temperature of the metering pump is 280 °C, the rotation speed of the metering pump is 2.7 r / min, and the stretching ratio is 1.8.

[0116] (2) The polylactic acid fiber nonwoven material obtained in step (1) is cut into a rectangular material with a length of 170 cm and a width of 100 mm along the machine direction, and then wound along the width direction and fixed in a mold tube with an inner diameter of 9 mm to form a polylactic acid fiber-based humidifying material.

[0117] Test Example

[0118] The liquid absorption performance, drying performance, and mechanical properties of the micro-overlapped bionic bamboo joint fiber-based hollow materials prepared in Examples 1-5 and 4, 6-9 and the polylactic acid fiber-based humidifying material prepared in Comparative Example 1 are tested respectively. In the following text, the micro-overlapped bionic bamboo joint fiber-based hollow materials prepared in Examples 1-5 are represented by stretching air pressures of 24 kPa, 28 kPa, 32 kPa, 36 kPa, and 40 kPa in turn; the micro-overlapped bionic bamboo joint fiber-based hollow materials prepared in Example 4 and Examples 6-9 are represented by volume densities of 1.8 g / cm 3 、1.6 g / cm 3 、1.4 g / cm 3 、1.2 g / cm 3 and 1.1 g / cm 3 in turn.

[0119] The fiber diameter and the pore diameter between fibers are measured using NanoMeasurer, and the results are as Figure 4 shown. Figure 4 For the fiber diameter and pore size distribution of the PLA fiber nonwoven materials with different stretching air pressures, it can be seen from the figure that as the stretching air pressure increases, the average fiber diameter of the PLA fiber nonwoven material decreases from 8.6 μm to 4.8 μm, and the pore diameter between fibers decreases from 58.4 μm to 36.1 μm.

[0120] The liquid absorption rate of the test sample was measured according to ASTM D5802-1995(R2001) "Standard Test Method for Sorption of Bibulous Paper Products (Sorptive Rate and Capacity Using Gravimetric Principles)", as shown in Equation 1.

[0121]

[0122] Where: V l is the moisture absorption rate, mg / s; g(t + Δt) is the weight of the absorbed liquid at t + Δt, g; g(t) is the weight of the absorbed liquid at t, g. The results are as Figure 5 , Figure 6 and Figure 7 shown.

[0123] The liquid absorption performance of the micro-overlapping bionic bamboo fiber-based hollow materials prepared under different drafting air pressures in Examples 1-5 was tested, and the results are as shown in Figure 5. Figure 5 In Figure a, it is the liquid absorption curve. It can be seen that the liquid absorption mass at 400 s (the mass of the liquid water absorbed at 400 s of liquid absorption) increases from 3185 mg to 4483 mg, showing the typical liquid absorption law of porous materials. In the initial stage, the higher slope of the liquid absorption curve means a faster liquid absorption speed. This is mainly because in the initial stage of the liquid climbing from the bottom of the sample, the capillary force is much greater than the gravity and resistance of the liquid. After that, as the climbing height of the liquid increases, the curve slope decreases and the trend becomes gentle. The test results are as Figure 5 shown in Figure b. It can be seen that as the drafting air pressure increases from 24 kPa to 40 kPa, the liquid absorption rate increases from 80.1 mg / s to 108.4 mg / s, and the liquid absorption efficiency increases by 26.1%. This may be because the pores of the PLA micro-nano fiber layer formed by the larger hot air pressure are smaller and have a greater capillary force, which cooperates with the large pore structure of the viscose fiber layer, thus realizing the rapid transmission of liquid in the height direction.

[0124] Figure 6 shows the liquid absorption performance of the micro-overlapping bionic bamboo fiber-based hollow materials with different volume densities. From Figure 6 the liquid absorption curve in Figure a and Figure 6 the liquid absorption rate in Figure b, it can be seen that as the sample density decreases from 1.8 g / cm 3 to 1.1 g / cm 3, the liquid absorption rate increased from 72.4 mg / s to 112.4 mg / s (the liquid absorption efficiency increased by 55.2%), and the liquid absorption mass at 400 s (the mass of liquid water absorbed at 400 s of liquid absorption) increased from 3337 mg to 4383 mg. This may be because the sample with low bulk density has a large pore structure. On the one hand, the large pore structure is conducive to the high-speed transmission of liquid water when it contacts the sample instantaneously, so the front slope of the liquid absorption curve is large; on the other hand, the large pores have more liquid storage space, so the final liquid absorption mass is large.

[0125] Figure 7 It is the moisture absorption curve of the polylactic acid fiber-based humidifying material prepared in Comparative Example 1. It can be seen that the moisture absorption capacity of the sample in Comparative Example 1 decreased significantly compared with that of the bionic bamboo joint sample. The moisture absorption rate in the initial stage was 50.28 mg / s, and the total mass of liquid absorbed at 400 s was 2351 mg. This shows that a single structure cannot provide better power for the high-speed and large-scale climbing of liquid.

[0126] The liquid holding rate and liquid retention rate of the micro-overlapped bionic bamboo joint fiber-based hollow materials prepared in Examples 1-5 and 4, 6-9 were tested respectively: According to GB / T 24218.6-2010 "Textiles - Test methods for nonwovens - Part 6: Determination of absorbency", the liquid holding rate and liquid retention rate of the samples were tested, as shown in Formulas (2) and (3).

[0127] C = (Z2 - Z1) / Z1 (2)

[0128] B = (Z3 - Z1) / Z1 (3)

[0129] In the formula: C is the liquid holding rate, %; B is the liquid retention rate, %; Z1 is the dry weight of the specimen, g; Z2 is the weight measured after the wetted specimen is left standing, g; Z3 is the weight measured after the wetted specimen is pressed, g. The test results of the liquid holding rate and liquid retention rate are as Figure 8 and Figure 9 shown.

[0130] Figure 8 are the liquid holding rate and liquid retention rate of the micro-overlapped bionic bamboo joint fiber-based hollow materials prepared under different draft air pressures. It can be seen from Figure 8 that when the hot air pressure increased from 24 kPa to 40 kPa, the liquid holding rate decreased from 491.3% to 465.5%, and the liquid retention rate increased from 360.6% to 386.0%. This is because as the hot air pressure increases, the fiber diameter decreases, the pores between the fibers become smaller, and a dense and oriented arrangement structure is formed, reducing the liquid absorption amount of the sample; but the specific surface area of the fiber increases with the decrease of the fiber diameter, providing more moisture absorption sites for liquid water molecules, so the change of the liquid retention rate is not significant.

[0131] Figure 9The liquid holding rate and liquid retention rate of micro-overlapping bionic bamboo fiber-based hollow materials with different volume densities are shown in Table 1. Figure 9 It can be seen that when the volume density of the sample increases from 1.8 g / cm 3 Reduced to 1.1 g / cm 3 , the liquid retention rate increased from 462.9% to 489.0%, and the liquid retention rate increased from 364.0% to 382.5%. This may be because the loose structure formed when the sample volume density decreases is more conducive to the retention of liquid water.

[0132] The drying rate test was conducted on the micro-overlapping bionic bamboo fiber-based hollow materials prepared in Examples 1-5 and 4, 6-9 and the polylactic acid fiber-based humidifying material prepared in Comparative Example 1: According to AATCC·201-2014 "Drying Rate of Fabrics: Heated Plate Method", the prepared micro-overlapping bionic bamboo fiber-based hollow materials were tested using a drying rate tester (Shanghai Luozhong Technology Development Co., Ltd.) to obtain the drying curve and drying rate. The test sample height was 3 mm, and the results were as follows: Figure 10 , Figure 11 and Figure 12 shown.

[0133] Figure 10 It is the drying performance of micro-overlapping bionic bamboo fiber-based hollow materials prepared with different drafting wind pressures. Figure 10 Figure a in the middle is the drying curve under different hot air pressures. It can be seen that the constant drying time decreases with the increase of hot air pressure; the surface temperature of the material shows a trend of decreasing, gentle, increasing and gentle changes with the increase of drying time. Under the breeze of 1.5±0.5m / s, the liquid water evaporates quickly and maintains a stable evaporation rate. The sample temperature remains stable during this time; when the liquid water in the sample is not enough to support a constant evaporation rate, the sample temperature begins to rise and remains stable as the water evaporation process ends. Figure 10 It can be seen from the drying rate in Figure b that when the drafting air pressure increases from 24 kPa to 40 kPa, the drying rate of the sample increases from 0.57 mL / hour to 0.69 mL / hour, and the drying efficiency is improved by 21.1%.

[0134] Figure 11 The drying performance of micro-overlapping bionic bamboo fiber-based hollow materials with different volume densities. Figure 11 Middle a picture and Figure 11 As can be seen in Figure b, when the sample volume density increases from 1.8 g / cm 3 Reduced to 1.1 g / cm 3, the drying rate of the sample increased from 0.68 mL / hour to 1.03 mL / hour, and the drying efficiency increased by 51.5%.

[0135] Figure 12 It is the drying curve graph of the polylactic acid fiber-based humidifying material prepared in Comparative Example 1. It can be seen that the drying rate of the sample also decreased to 0.48 mL / hour.

[0136] The mechanical properties of the micro-overlapped bionic bamboo node fiber-based hollow materials prepared in Examples 1-5 and 4, 6-9 and the polylactic acid fiber-based humidifying material prepared in Comparative Example 1 were tested respectively: According to GB / T 24218.3-2010 "Textiles-Test methods for nonwovens-Part 3: Determination of tensile strength and elongation (Strip method)", the tensile fracture properties of the samples were tested by using an HD026S-100 electronic fabric strength tester (Nantong Hongda Experimental Instrument Co., Ltd., China). The tensile rate was 100 mm / min, the clamping gauge length was 100 mm, the experimental temperature was 25 °C, and the ambient humidity was 60%. The results are as Figure 13 and Figure 14 shown.

[0137] Figure 13 It is the tensile fracture curve of the micro-overlapped bionic bamboo node fiber-based hollow material prepared by the present invention. Among them, Figure 13 Figure a is the displacement-stress curve of the micro-overlapped bionic bamboo node fiber-based hollow material prepared with different drafting air pressures. It can be seen that as the drafting air pressure increased from 24 kPa to 40 kPa, the tensile fracture strength increased from 262.2 N to 346.4 N, an increase of about 32.1%. Figure 13 Figure b in it is the displacement-stress curve of the micro-overlapped bionic bamboo node fiber-based hollow material with different volume densities. It can be seen that the tensile strength of the sample increases with the increase of the sample volume density. Specifically, when the sample volume density increased from 1.1 g / cm 3 to 1.8 g / cm 3 , the tensile fracture strength increased from 255.2 N to 286.0 N, an increase of about 12.1%. The reason for this phenomenon may be that the number of fibers per unit volume increases with the increase of the volume density, the number of bonding points between the fibers increases, and the fibers are more evenly stressed, which helps to resist external forces and increase the tensile fracture strength. Figure 14The figure shows the tensile curve of the polylactic acid fiber-based humidifying material prepared in Comparative Example 1. It can be seen that the tensile breaking strength of the sample directly wound from the polylactic acid fiber nonwoven material is 48.5 N. From the above mechanical property tests, it can be seen that the laminated cylindrical structure prepared by hot rolling and compounding the polylactic acid fiber nonwoven material and the viscose fiber material overcomes the deficiency of the weak mechanical properties of the polylactic acid fiber nonwoven material, demonstrates excellent tensile resistance, and illustrates the rationality of the bionic bamboo joint structure design obtained in this patent, meeting the mechanical property requirements for the application of the humidifying core.

[0138] Application Example

[0139] Using the micro-overlapped bionic bamboo joint fiber-based hollow material prepared in Example 6 as the humidifying core of a humidifier, and conducting a humidifying performance test:

[0140] According to the standard (GB / T 23331-2018 Humidifiers), a small humidifier is used to characterize the humidifying ability of the sample, and the calculation of the humidifying amount is as shown in formula (4).

[0141] Q = (m1 - m2) / (ρ × T) × 3600 (4)

[0142] In the formula: Q is the humidifying amount, mL / h; m1 is the initial water amount, g; m2 is the final water amount, g; ρ is the water density, g / mL; T is the test time, s. The test calculates the average value through 5 tests, that is, the humidifying amount when using this sample as the humidifying core is obtained.

[0143] A small humidifier is used to characterize the humidifying ability of the sample. Figure 15 It is the application scenario diagram of the micro-overlapped bionic bamboo joint fiber-based hollow material and an example diagram of the humidifying core. First, fix the material in Example 6 in the liquid guide groove, the sample is immersed in the liquid groove to continuously absorb water, and continuously supply liquid water to the humidifying element; through the continuous operation of the humidifying element, the rapid evaporation of liquid water is realized, and then the change in the water amount in the water tank per unit time is used as the liquid amount transmitted by the humidifying core, which is also the standard index for the applicability of the humidifying core. The result of the change in the liquid mass after the humidifier works for 1 h is as Figure 16 shown. According to the standard (GB / T 23331-2018 Humidifiers), the calculated humidifying amount of this sample as the humidifying core is 78 mL / h, meeting the standard requirements of the single-port rated humidifying amount (>70 mL / h) of this commercial humidifier. This shows that the micro-overlapped bionic bamboo joint fiber-based hollow material has excellent liquid guiding performance and can be used as a liquid guiding material in the humidifying field and for improving the indoor environment.

[0144] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A micro-overlapping bionic bamboo joint fiber-based hollow material, characterized in that It includes PLA micro-nano fiber layers and viscose fiber layers arranged alternately from the inside to the outside; the PLA micro-nano fiber layers and viscose fiber layers form a laminated structure with a loose inner and tight outer hierarchical distribution in the material thickness direction, and present continuous or quasi-continuous layered micro-pores in the direction parallel to the length direction.

2. The hollow material based on the micro-overlapping bionic bamboo fiber according to claim 1, characterized in that, The PLA micro-nano fiber layer is a polylactic acid fiber non-woven material, with an average fiber diameter of 4.8 - 8.6 μm and a pore size of 36.1 - 58.4 μm.

3. The hollow material based on the micro-overlapping bionic bamboo fiber according to claim 1, characterized in that, The viscose fiber layer is a viscose fiber non-woven fabric with a basis weight of 97.3 g / m 2 , and a thickness of 0.51 mm.

4. The preparation method of the micro-overlapping bionic bamboo joint fiber-based hollow material according to any one of claims 1-3, characterized in that, The steps are as follows: (1) A uniform blend of polylactic acid, secondary alkyl sulfonate, and polyethylene glycol is prepared into a polylactic acid fiber non-woven material, i.e., the PLA micro-nano fiber layer, by melt blowing and in-situ drawing. (2) The viscose fibers are carded and laid to form a viscose fiber web, and then hydroentangled and dried to obtain a viscose fiber non-woven fabric, i.e., the viscose fiber layer. (3) The polylactic acid fiber non-woven material in step (1) and the viscose fiber non-woven fabric in step (2) are stacked up and down and hot-rolled and compounded to obtain a polylactic acid / viscose fiber non-woven composite material. (4) The polylactic acid / viscose fiber non-woven composite material in step (3) is wound and formed and placed in a cylindrical mold device for fixation to obtain a micro-overlapped bionic bamboo joint fiber-based hollow material.

5. The preparation method of the micro-overlapping bionic bamboo fiber-based hollow material according to claim 4, characterized in that, In step (1), the mass ratio of polylactic acid, secondary alkyl sulfonate, and polyethylene glycol is (94 - 97):(2 - 3):(1 - 3).

6. The preparation method of the micro-overlapping bionic bamboo joint fiber-based hollow material according to claim 5, wherein, The process parameters of melt blowing in step (1) are as follows: the temperature of the first zone of the screw in the screw extruder is 150 - 170 °C, the temperature of the second zone is 230 - 250 °C, the temperature of the third zone is 270 - 290 °C, the temperature of the metering pump is 270 - 290 °C, the rotation speed of the metering pump is 2.7 r / min, and the die head temperature is 260 - 280 °C; the pipeline temperature is 270 - 290 °C, the hot air temperature is 270 - 290 °C, and the drawing air pressure is 24 - 40 Kpa.

7. The preparation method of the micro-overlapping bionic bamboo joint fiber-based hollow material according to claim 6, characterized in that, The drawing ratio of in-situ drawing in step (1) is 1.

8.

8. The preparation method of the micro-overlapping bionic bamboo joint fiber-based hollow material according to claim 4, characterized in that, In step (2), the length of the viscose fiber is 38 mm and the fineness is 1.38 denier.

9. The preparation method of the micro-overlapping bionic bamboo joint fiber-based hollow material according to claim 4, wherein, The hot-rolling process parameters in step (3) are: the hot-rolling temperature is 110 °C, the hot-rolling pressure is 2.5 MPa, and the hot-rolling speed is 2 m / min.

10. The preparation method of the micro-overlapping bionic bamboo joint fiber-based hollow material according to claim 4, wherein, The volume density of the micro-overlapped bionic bamboo fiber-based hollow material in the step (4) is 1.1-1.8 g / cm 3 .

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