A calamus-like leaf polylactic acid ultrafine fiber composite material, a preparation method and application thereof

Abstract

The application provides a kind of aloe-like leaf polylactic acid ultrafine fiber composite material and its preparation method and application, belong to medical protective material technical field.The aloe-like leaf polylactic acid ultrafine fiber composite material is prepared by using paraffin wax (PW) and polydimethylsiloxane (PDMS) hydrophobic modified polylactic acid (PLA) as raw material, through melt blowing method, using melt blowing in-situ drafting process to obtain directional PLA fiber material, then the directional PLA fiber material is used as upper and lower surface layer, PLA spunbond fiber material is used as intermediate layer, and template net curtain is covered, and the aloe-like leaf structure can give polylactic acid fiber liquid directional rolling characteristics and excellent mechanical properties, to provide new ideas for multifunctional, high-quality medical and health care protective materials.

Description

Technical Field

[0001] This invention relates to the field of medical protective materials technology, and in particular to a polylactic acid ultrafine fiber composite material resembling calamus leaf, its preparation method, and its application. Background Technology

[0002] With the increasing awareness of health and the pursuit of a high quality of life, medical protective materials, as the last physical barrier against bacteria, viruses, and pollutants, have become crucial functional materials for ensuring public health safety, protecting the health of medical personnel, and enhancing individual protective effectiveness. Polylactic acid (PLA) microfiber materials, due to their large specific surface area, high porosity, and dense structure, exhibit excellent liquid shielding performance and high permeability, showing broad application prospects in many fields such as medical and health care, personal protection, and outdoor protection. However, pure PLA is brittle and has a high surface energy, resulting in strong liquid adhesion and weak mechanical properties. Furthermore, PLA's often disordered structure easily leads to liquid accumulation, causing risks of secondary contamination and cross-infection. Therefore, improving the liquid roll-off capability and mechanical properties of PLA microfiber materials has become a key common problem that urgently needs to be solved in the fields of functional fiber materials and medical and health protective materials. Summary of the Invention

[0003] The purpose of this invention is to provide a calamus leaf-like polylactic acid (PLA) microfiber composite material, its preparation method, and its application. The calamus leaf-like PLA microfiber composite material has excellent liquid roll-off ability and mechanical properties, solving the problem of easy liquid accumulation caused by the disordered structure of polylactic acid (PLA).

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing a polylactic acid ultrafine fiber composite material resembling calamus leaf, comprising the following steps: Paraffin wax is mixed with polydimethylsiloxane to obtain a modified material; The modified material is mixed with polylactic acid to obtain a blend; The blend is sequentially heated and melted, then melt-blown and in-situ stretched into a web to obtain oriented PLA ultrafine fibers; The oriented PLA microfiber is used as the upper and lower surface layers, and PLA spunbond fiber material is used as the middle reinforcing layer. After being stacked in the order of upper surface layer, middle reinforcing layer and lower surface layer, a template mesh is covered on the top layer of one side and thermally bonded to obtain a calamus leaf-like polylactic acid microfiber composite material.

[0005] Preferably, the mass ratio of paraffin to polydimethylsiloxane is 1~5:0.5~2.5.

[0006] Preferably, the mass ratio of polylactic acid to modified material is 93.5~97.5:2.5~6.5.

[0007] Preferably, the temperature of the screw extruder used for heating and melting is: 175~195℃ in zone one, 205~225℃ in zone two, and 215~235℃ in zone three.

[0008] Preferably, the conditions for the meltblown in-situ stretching into a web include: hot air pressure of 30~50 kPa and hot air temperature of 250~270℃.

[0009] Preferably, the conditions for in-situ stretching of the meltblown wire into a web include: a meltblown die temperature of 215~235℃, a die spinneret diameter of 0.22 mm, an aspect ratio of 10:1, and a receiving distance of 18 cm for the receiving screen.

[0010] Preferably, the thickness of the upper surface layer is 0.40~0.60mm, the thickness of the intermediate reinforcing layer is 0.10~0.14mm, and the thickness of the lower surface layer is 0.40~0.60mm; The template mesh curtain has a linear grid pattern.

[0011] Preferably, the conditions for thermal bonding include: a thermal bonding speed of 2~4 m / s, a thermal bonding pressure of 0.20~0.40 MPa, and a thermal bonding temperature of 100~120 ℃.

[0012] The present invention provides a polylactic acid ultrafine fiber composite material similar to calamus leaf prepared by the preparation method described in the above technical solution.

[0013] This invention provides the application of the calamus leaf-like polylactic acid microfiber composite material described above in the field of medical and health protective materials.

[0014] This invention provides a method for preparing a calamus leaf-like polylactic acid (PLA) microfiber composite material. Using paraffin (PW) and polydimethylsiloxane (PDMS) hydrophobically modified PLA as raw materials, oriented PLA fiber material is obtained through a melt-blowing in-situ stretching process. The oriented PLA fiber material is then used as the upper and lower surface layers, with PLA spunbond fiber material as the middle layer, and covered with a template mesh. The calamus leaf-like PLA microfiber composite material is then prepared through a thermal composite process. This calamus leaf-like structure endows the PLA fibers with directional liquid roll-off characteristics and excellent mechanical properties, providing a new approach for multifunctional, high-quality medical and health protective materials.

[0015] This invention controls the size of small fibers by controlling the temperature of the meltblown die and the hot air temperature; and controls the mesh size by laying meshes of different sizes through a thermal bonding process. The orderly construction of small fibers and directional grooves in the calamus leaf-like structure formed by thermal bonding gives the composite material excellent liquid directional roll-off characteristics, with a longitudinal and transverse roll-off angle difference of 36.4°.

[0016] This invention successfully prepared gradient composite materials with different pore size and diameter distributions by controlling the hot air pressure and thermal bonding temperature, and with calamus leaf-like structural characteristics, providing a structural basis for liquid directional rolling performance.

[0017] In this invention, the PLA spunbond layer in the middle layer possesses excellent mechanical properties. The three-layer sandwich structure of the dense meltblown layer and the loose, large-pore spunbond layer significantly improves the mechanical properties of the material, increasing the longitudinal breaking strength and bursting strength to 56.30 N and 116.03 N, respectively. Simultaneously, as the thermal bonding temperature increases to 120 °C, the longitudinal and transverse flexibility values ​​increase to 8.0 N and 14.8 N, respectively, while the water vapor transmission rate decreases to 1424.2 g / (m²). 2 (24h) provides new ideas for the design and development of high-performance medical and health protective materials. Attached Figure Description

[0018] Figure 1 This is a schematic diagram illustrating the preparation of the calamus leaf-like polylactic acid ultrafine fiber composite material of the present invention; Figure 2 The images show surface electron microscope (SEM) images (a-e) of the calamus leaf-like PLA ultrafine fiber composite materials prepared at different thermal bonding temperatures in Examples 1, 6-9, and Example 1 (f). (a) T n = 100 ℃、(b) T n = 105 ℃, (c) T n = 110 ℃, (d) T n = 115 ℃, (e) T n = 120℃、(f) T n = 110 ℃; Figure 3The diameter distribution curves (a~b) and pore size distribution curves (c~d) for different materials are shown, where (a) corresponds to the commercially available PLA spunbond fiber layer, (b) corresponds to the oriented PLA microfiber meltblown layer in Example 1, (c) corresponds to the PLA microfiber composite material in Examples 1 and 6~9, and (d) corresponds to the PLA microfiber composite material in Examples 2~5. Figure 4 The liquid directional roll-off characteristics of PLA ultrafine fiber composites resembling calamus leaves prepared under different hot air pressures and different thermal bonding temperatures are shown in the figures. (a) is the water contact angle of samples 1 and 6-9, (b) is the water contact angle of samples 2-5, (c) is the alcohol-time curve of sample 1, (d) is the roll-off curve of sample 1, (e) is the roll-off angle of samples 1 and 6-9, and (f) is the roll-off angle of samples 2-5. Figure 5 To assess the permeability and comfort of calamus leaf-like PLA microfiber composites prepared under different conditions, where (a)~(c) correspond to Examples 1 and 6~9, and (d)~(f) correspond to Examples 2~5; Figure 6 The tensile fracture strength and bursting strength variation curves of the calamus leaf-like PLA ultrafine fiber composite material prepared under different thermal bonding temperatures and hot air pressures are shown, where (a~c) correspond to Examples 1 and Examples 6~9, and (d~f) correspond to Examples 2~5. Figure 7 Photograph of the grid template used in Example 1; Figure 8 Photograph of the calamus leaf-like PLA ultrafine fiber composite material prepared in Example 1. Detailed Implementation

[0019] In this invention, unless otherwise specified, the raw materials or reagents required for preparation are all commercially available products well known to those skilled in the art.

[0020] like Figure 1 As shown, this invention provides a method for preparing a polylactic acid microfiber composite material resembling calamus leaf, comprising the following steps: Paraffin wax is mixed with polydimethylsiloxane to obtain a modified material; The modified material is mixed with polylactic acid to obtain a blend; The blend is sequentially heated and melted, then melt-blown and in-situ stretched into a web to obtain oriented PLA ultrafine fibers; The oriented PLA microfiber is used as the upper and lower surface layers, and PLA spunbond fiber material is used as the middle reinforcing layer. After being stacked in the order of upper surface layer, middle reinforcing layer and lower surface layer, a template mesh is covered on the top layer of one side and thermally bonded to obtain a calamus leaf-like polylactic acid microfiber composite material.

[0021] In this invention, the mass ratio of paraffin wax to polydimethylsiloxane is preferably 1~5:0.5~2.5, more preferably 2~4:1.0~2.0, and even more preferably 3:1.5; the mass ratio of polylactic acid to the modifier is preferably 93.5~97.5:2.5~6.5, more preferably 95~97:3~5, and even more preferably 95.5:4.5.

[0022] In this invention, paraffin (PW) is heated to melt at 80°C, then polydimethylsiloxane (PDMS) is added and stirred until uniformly mixed. After cooling to room temperature, the mixture is sliced ​​to obtain PW@PDMS modified material.

[0023] The polylactic acid (PLA) of the present invention is in the form of slices. Preferably, the PLA slices are vacuum dried at 80°C for 12 hours to remove moisture, and then mixed with the modified material.

[0024] The present invention does not impose any special limitations on the mixing process of the modified material and polylactic acid; mechanical mixing can be carried out in accordance with a process known in the art to achieve uniformity.

[0025] In this invention, paraffin wax acts as a nucleating agent, serving as a heterogeneous nucleation site in the PLA melt to promote PLA crystallization. Secondly, the low melting point of paraffin wax reduces the viscosity of the blended melt, improving the melt-blown drawing effect and thus refining the fiber diameter. Furthermore, paraffin wax increases the surface roughness of the fibers, enhancing their hydrophobicity.

[0026] In this invention, PDMS is an organosilicon elastomer with low surface energy and flexible segments, serving as both a hydrophobic modifier and a structural stabilizer. Its low surface energy characteristic allows it to spontaneously migrate to the fiber surface during meltblowing, forming a continuous hydrophobic layer and reducing the surface energy of the fiber material, thereby enhancing its hydrophobicity. Furthermore, the flexible siloxane backbone in PDMS improves its mechanical properties.

[0027] In this invention, the blended material is preferably fed into a meltblown experimental device, heated and melted by a screw extruder, and quantitatively delivered to the meltblown die by a metering pump. Under the stretching action of the high-speed hot air flow, the melt stream is refined into ultrafine fibers and deposited on a wire mesh to form a PLA ultrafine fiber web. Subsequently, under the action of winding tension, the fiber web is further stretched and oriented longitudinally to obtain oriented PLA ultrafine fibers. This invention does not have a specific limitation on the meltblown experimental device; any meltblown system well-known in the art for preparing nonwoven fabrics is acceptable.

[0028] In this invention, the preferred temperatures of the screw extruder used for heating and melting are: zone 1 temperature 175~195℃, zone 2 temperature 205~225℃, and zone 3 temperature 215~235℃; more preferably, zone 1 temperature 180~190℃, zone 2 temperature 210~220℃, and zone 3 temperature 220~230℃; even more preferably, zone 1 temperature 185℃, zone 2 temperature 215℃, and zone 3 temperature 225℃.

[0029] In this invention, the preferred conditions for meltblown in-situ stretching and web formation include: a hot air pressure of 30-50 kPa, more preferably 35-45 kPa, even more preferably 40 kPa, and a hot air temperature of 250-270°C, more preferably 260°C. This invention uses a Roots blower to adjust the hot air pressure and temperature, thereby controlling the fiber diameter and orientation structure through the hot air pressure.

[0030] In this invention, the preferred conditions for in-situ stretching of meltblown wire into a web include: a meltblown die temperature of 215~235℃, more preferably 225℃, a die spinneret diameter of 0.22 mm, and an aspect ratio of 10:1; and a receiving distance of 18 cm for the receiving screen.

[0031] In this invention, the PLA spunbond fiber material is a nonwoven material prepared from PLA using a spunbonding method. This invention does not impose any special limitations on the source or specific specifications of the PLA spunbond fiber material; commercially available products well-known in the art are acceptable. In an embodiment of this invention, the areal density of the PLA spunbond fiber material is specifically 25 g / m³. 2 .

[0032] In this invention, the thickness of the upper surface layer (meltblown layer) is preferably 0.40~0.60mm, more preferably 0.45~0.55mm, and even more preferably 0.50mm; the thickness of the intermediate reinforcing layer (spunbond layer) is preferably 0.10~0.14mm, more preferably 0.11~0.12mm; and the thickness of the lower surface layer (meltblown layer) is preferably 0.40~0.60mm, more preferably 0.50mm.

[0033] In this invention, oriented PLA microfibers are used as the upper and lower surface layers, and a layer of PLA spunbond fiber material is used as the middle reinforcing layer. The layers are stacked in the order of "upper surface layer / spunbond layer / lower surface layer", and a template mesh is covered on the top layer of one side. The entire stack is then sent into a hot melt bonding machine for hot pressing and solidification.

[0034] In this invention, the template mesh curtain has a linear grid pattern; the grid pattern is preferably a linear parallel pattern, and more preferably a rhomboid or rectangular grid pattern. This invention does not impose any special limitations on the specific arrangement size of the grid pattern; commercially available sizes of template mesh curtains known in the art are acceptable.

[0035] The present invention does not have any special limitation on the source of the template mesh curtain; any commercially available product known in the art is acceptable.

[0036] In this invention, the top layer of the single-sided surface is the surface of the upper or lower surface layer.

[0037] In this invention, the preferred conditions for thermal bonding include: a thermal bonding speed of 2-4 m / s, more preferably 3 m / s; a thermal bonding pressure of 0.20-0.40 MPa, more preferably 0.30 MPa; and a thermal bonding temperature of 100-120 °C, more preferably 105-115 °C, and even more preferably 110 °C. The thermal bonding is preferably carried out in a hot melt bonding machine to achieve thermal solidification and molding.

[0038] During the thermal bonding process, under the synergistic effect of heat and pressure, the fibers soften and rearrange, and the grid structure of the template is transferred to the surface of the composite material, forming a parallel groove structure similar to that of calamus leaves; at the same time, thermal bonding points are generated between the interlayer fibers, so that the three-layer structure is firmly composited and formed.

[0039] The calamus-leaf-like polylactic acid ultrafine fiber composite material of this invention is a three-layer sandwich structure (meltblown / spunbond / meltblown) formed by hot-press bonding. Both the upper and lower meltblown layers have a calamus-leaf-like structure, which can be precisely controlled by adjusting the hot-pressing temperature and the pattern of the template (the template pattern is formed by covering the upper or lower surface of the three-layer composite material with a grid template and then hot-rolling it using a hot-pressing device). The resulting fiber material has a controllable, regular groove structure, and the fiber orientation is highly oriented along the longitudinal direction. Liquid roll-off is achieved through the synergistic effect of a rough surface (Wenzel model) and low surface energy (Cassie-Baxter model). Therefore, the fiber material of this invention exhibits significant longitudinal and transverse roll-off angle differences, i.e., directional roll-off characteristics, and possesses liquid roll-off performance. Moreover, the three-layer sandwich structure results in excellent mechanical properties of the fiber material, especially bursting strength.

[0040] The present invention provides a polylactic acid ultrafine fiber composite material similar to calamus leaf prepared by the preparation method described in the above technical solution.

[0041] This invention provides the application of the calamus leaf-like polylactic acid microfiber composite material described above in the field of medical and health protective materials. This invention does not specifically limit the method of application; it can be applied according to methods well known in the art.

[0042] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0043] Unless otherwise specified, the experimental methods described in the various embodiments of this invention are conventional methods; unless otherwise specified, the raw materials used are all commercially available products, and the proportions are all by mass percentage.

[0044] The specifications and sources of the raw materials used in the following examples are as follows: PLA: 6252D, Nature Works LLC, USA, with a molecular weight of 1.0×10⁵ and a melt index of 21.3 g / (10 min) (210 ℃); PW: 8002-74-2, Zhengzhou Jiajie Chemical Products Co., Ltd., melting point is 58 ℃; PDMS: QL-200 DM 50, Huangshan Qiangli Chemical Co., Ltd., density 0.96 g / cm³ 3 The viscosity coefficient is 0.59; PLA spunbond fiber material (areal density 25g / m²) 2 (Source: Quanzhou Xinyangguang Nonwoven Fabric Co., Ltd.; Melting point: 165℃) Template mesh curtain (such as) Figure 7 (As shown): Mesh diameter 2 mm, mesh width 1 m, areal density 68 g / m² 2 It has a thickness of 0.55mm and is sourced from Anping County Banzhu Metal Products Factory. It is made of PP material.

[0045] Example 1

[0046] 1) Raw material pretreatment: Polylactic acid (PLA) chips were vacuum dried at 80℃ for 12h to remove moisture; paraffin (PW) was heated to melt at 80℃, polydimethylsiloxane (PDMS) was added and stirred vigorously. After mixing evenly, the mixture was cooled to room temperature and sliced ​​to obtain PW@PDMS modified chips. The dried PLA chips and PW@PDMS modified chips were mechanically mixed evenly at a mass ratio of 95.5:4.5 (wherein, by mass percentage, PLA 95.5%, PW 3%, and PDMS 1.5%) to obtain a blend.

[0047] 2) Preparation of Oriented PLA Ultrafine Fibers by In-situ Meltblowing Stretching: The blend was fed into the meltblowing experimental system and heated and melted sequentially in Zone 1 (185℃), Zone 2 (215℃), and Zone 3 (225℃). The blend was metered and pumped to the meltblowing die at a temperature of 225℃. The diameter of the spinneret orifice was 0.22 mm and the aspect ratio was 12:1. The hot air pressure was set to 40 kPa. Under the stretching action of the high-speed hot air flow at a temperature of 260℃, the melt stream was refined into ultrafine fibers and deposited on a mesh screen with a receiving distance of 18 cm to form a PLA ultrafine fiber web. Subsequently, under the action of winding tension, the fiber web was further stretched and oriented in the longitudinal direction to obtain an oriented PLA ultrafine fiber layer.

[0048] 3) Layered construction and hot-press transfer lamination: The oriented PLA microfibers prepared above are used as the upper and lower surface layers (meltblown layers), respectively, and PLA spunbond fiber material (area density 25 g / m²) is added. 2 As the intermediate reinforcing layer (spunbond layer), the upper surface layer is 0.50 mm thick, the intermediate reinforcing layer is 0.12 mm thick, and the lower surface layer is 0.50 mm thick, and the layers are stacked in the order of "upper surface layer / spunbond layer / lower surface layer". A template mesh curtain with a linear grid pattern (such as...) is then placed over the surface of the upper surface layer. Figure 7 As shown), the constructed laminate was fed into a hot-melt bonding machine for hot-pressing and solidification. The hot-bonding speed was 3 m / s, the hot-bonding pressure was 0.30 MPa, and the hot-bonding temperature was set to 110℃, resulting in a PLA ultrafine fiber composite material resembling calamus leaf (as shown). Figure 8 (As shown).

[0049] Examples 2-5

[0050] The only difference between this set of embodiments and Embodiment 1 is that, in step 2), the hot air pressure ( Ap ) are: 30 kPa, 35kPa, 45 kPa, 50 kPa.

[0051] Examples 6-9

[0052] The only difference between this set of embodiments and Embodiment 1 is that in step 3), the thermal bonding temperature ( T n The temperatures are as follows: 100℃, 105℃, 115℃, and 120℃.

[0053] Comparative Example 1

[0054] The only difference between this comparative example and Example 1 is that the layering and hot-pressing transfer composite in step 3) are not performed. Instead, the oriented PLA microfiber layer obtained in step 2) is directly used as a single-layer material to obtain a single-layer PLA meltblown fabric sample that has not undergone hot rolling treatment.

[0055] The specific steps are as follows: 1) The raw material pretreatment and blend preparation are the same as step 1 in Example 1.

[0056] 2) Preparation of oriented PLA ultrafine fibers by meltblown in-situ stretching: The process parameters are the same as in step 2 of Example 1, and a single-layer oriented PLA ultrafine fiber material is obtained.

[0057] The comparative sample lacks a three-layer sandwich structure, and its surface does not have artificially controllable parallel grooves. Fiber orientation relies solely on a weak longitudinal arrangement formed by winding tension, lacking the structural characteristics of a calamus leaf. Testing revealed poor liquid roll-off performance; the difference between the longitudinal and transverse roll-off angles was insignificant (less than 10°), allowing liquid to easily spread or roll randomly on the surface, making directional roll-off difficult. Furthermore, due to the lack of an intermediate reinforcing layer and the absence of hot-pressing consolidation, the longitudinal breaking strength of the single-layer meltblown fabric is approximately 35-45 N, the transverse breaking strength is approximately 12-18 N, and the bursting strength is in the range of 30-50 N, significantly lower than in Example 1. In practical use, it is prone to deformation or breakage due to external forces. The above comparison demonstrates that single-layer PLA materials prepared solely by meltblowing cannot simultaneously meet the dual requirements of directional liquid roll-off and high mechanical properties, further highlighting the necessity and technical advantages of this invention in constructing a calamus leaf-like composite material through a three-layer structural design and hot-pressing transfer.

[0058] Characterization and performance testing

[0059] Figure 2 The images show surface electron microscope (SEM) images (a-e) of the calamus leaf-like PLA ultrafine fiber composite materials prepared at different thermal bonding temperatures in Examples 1, 6-9, and Example 1 (f). (a) T n = 100 ℃、(b) T n = 105 ℃, (c) T n = 110 ℃, (d) T n = 115 ℃, (e) T n = 120℃、(f) T n = 110 ℃; Depend on Figure 2 It can be seen that, under the thermal action of the linear grid patterned roller, the surface PLA microfiber material of the prepared sample interconnects and forms a highly parallel groove structure, which is highly similar to the leaf surface structure of calamus. Furthermore, the PLA microfiber composite material exhibits typical characteristics of meltblown nonwoven materials, namely, randomly assembled circular fibers of varying thicknesses forming a dense mesh structure, providing a structural basis for improving its waterproof and liquid roll-off properties. (Comparison) Figure 2Further observations (a~e) show that as the thermal bonding temperature increases, the PLA fibers become more compactly arranged, and the resulting groove structure becomes clearer. This phenomenon is mainly attributed to the increase in thermal bonding temperature, which makes PLA, which has a low glass transition temperature, more prone to displacement and rearrangement after heating. Under the action of the linear roller, the PLA rearranges along the longitudinal direction, making its directional groove structure characteristics clearer and providing more transport paths for the liquid to roll down in the direction. Figure 2 Image (f) shows a cross-sectional electron microscope image of the sample from Example 1, with a thermal bonding temperature of 110°C and a hot air pressure of 40 kPa. It can be seen that the prepared sample forms a complete gradient core structure from top to bottom in the thickness direction. That is, the porous structure of the middle layer is significantly different from the dense upper and lower layers, maintaining a high degree of similarity to the cross-sectional morphology of calamus leaves, thus providing a basis for the excellent structural stability of the fiber material.

[0060] Figure 3 The diameter distribution curves (a~b) and pore size distribution curves (c~d) for different materials are shown, where (a) corresponds to the commercially available PLA spunbond fiber layer, (b) corresponds to the oriented PLA microfiber meltblown layer in Example 1, (c) corresponds to the PLA microfiber composite material in Examples 1 and 6~9, and (d) corresponds to the PLA microfiber composite material in Examples 2~5. Depend on Figure 3 As shown in (a-b), the commercially available PLA spunbond fiber layer exhibits significant differences from the PLA fiber layer obtained by the meltblown method in Example 1. Specifically, the fiber diameter of the spunbond layer is mainly concentrated in the range of 9-18 μm, with an average fiber diameter of 12.65 μm, accounting for 42.66% of the total, and is predominantly coarse fiber. Conversely, the PLA fiber material in the meltblown layer is mainly concentrated in the range of 2-10 μm, with an average diameter of 5.02 μm, accounting for 30.92% of the total. The formation of this fine fiber is inseparable from the hot air pressure and the high-speed stretching effect of the winding roller on the PLA melt during the meltblown process, thus obtaining a small fiber diameter, providing a structural basis for shielding liquid penetration. The small fiber diameter distribution also has a certain influence on the forming of the fiber material. Figure 3 As shown in (c~d), the modal pore size of PLA microfiber composite materials gradually decreases with increasing heat bonding temperature and hot air pressure. Specifically, when the heat bonding temperature increases from 100 ℃ to 120 ℃, the median modal pore size decreases from 57.4 μm to 4.6 μm. Similarly, when the hot air pressure increases to 50 kPa, the median modal pore size decreases by 90.91%.

[0061] Figure 4The liquid directional roll-off characteristics of PLA microfiber composite materials for calamus leaf prepared under different hot air pressures and different thermal bonding temperatures are shown in the figures. (a) is the water contact angle of samples 1 and 6-9, (b) is the water contact angle of samples 2-5, (c) is the alcohol-time curve of sample 1, (d) is the roll-off curve of sample 1, (e) is the roll-off angle of samples 1 and 6-9, and (f) is the roll-off angle of samples 2-5.

[0062] from Figure 4 As shown in (a), the contact angle of the sample surface increases with increasing heat bonding temperature. This is because the increased heat bonding temperature causes fiber rearrangement, increasing the surface roughness of the sample. It is known that increased surface roughness makes hydrophilic fabrics more hydrophilic and hydrophobic fabrics more hydrophobic. Therefore, when the heat bonding temperature increases from 100 ℃ to 120 ℃, the water contact angle of the fabric surface increases from 133.5 ° to 151.7 °. Figure 4 As shown in (b), the water contact angle of the sample surface increases with increasing hot air pressure. From 30 kPa to 50 kPa, the water contact angle increased from 130.4° to 146.5°. This is because the hot air pressure makes the fibers more densely packed, reducing the contact area between the liquid and the sample, thus resulting in a gradually decreasing contact angle. Figure 4 As shown in (c), the sample still exhibits excellent shielding properties against alcohol as the concentration increases to 30%. After 5 minutes, the alcohol contact angle remains greater than 120°, indicating that this sample not only provides barrier protection against water but also against alcohol, and this property is not limited to water. Figure 4 As shown in (d), with the increase of the tilt angle, both the longitudinal and lateral advance angles gradually increase, while the retreat angles decrease until gravity overcomes the liquid adhesion force, and the liquid rolls off the sample surface in a specific direction. Specifically, from Figure 4As shown in (e-f), with the increase of the thermal bonding temperature to 120 ℃, the longitudinal and transverse roll angles decreased from 69.6 ° and 88.6 ° to 33.2 ° and 55.0 °, respectively, representing decreases of 52.30% and 37.92%. Similarly, hot air pressure also has a positive impact on the rolling characteristics of the sample. When the hot air pressure increases from 30 kPa to 50 kPa, the longitudinal roll angle decreases from 69.4 ° to 35.4 °, while the transverse roll angle decreases from 79.8 ° to 50.2 °. Notably, the longitudinal roll angle is always significantly lower than the transverse roll angle, indicating that the liquid rolls more easily along the longitudinal direction on the sample surface, exhibiting excellent liquid directional roll characteristics. This phenomenon is mainly due to the calamus-like leaf structure providing the liquid with more longitudinal transport paths, giving it clear anisotropic characteristics and providing a functional basis for its high-quality application in the field of medical protective materials.

[0063] Figure 5 To assess the permeability and comfort of PLA microfiber composite materials prepared under different conditions, where (a) to (c) correspond to Examples 1 and 6 to 9, and (d) to (f) correspond to Examples 2 to 5.

[0064] Breathability and comfort are important evaluation indicators for the application of fabrics in medical protective materials. Figure 5 The diagram shows the softness force-displacement curves and air permeability variation curves of samples at different thermal bonding temperatures and hot air pressures. From... Figure 5 As shown in (a~b), both longitudinal and transverse force values ​​gradually increase with increasing heat bonding temperature. When the heat bonding temperature increases from 100 ℃ to 120 ℃, the longitudinal and transverse softening forces increase from 3.8 N and 9.7 N to 8.0 N and 14.8 N, respectively. Under the Handle-O-meter test method, a smaller softening force value means that the external force required for material deformation is relatively small, indicating that the fabric has higher softness characteristics. This phenomenon indicates that the softness of the composite material sample decreases accordingly with increasing heat bonding temperature. This is because the increase in heat bonding temperature leads to an increase in fiber bonding points, resulting in a worse hand feel of the fabric. Figure 5 (a) and (b)). Similarly, air permeability and water vapor permeability also decreased with increasing heat bonding temperature, decreasing by 31.26% and 10.33%, respectively. Figure 5 (c)). Hot air pressure also has a negative correlation with the flexibility of the composite material. Specifically, when the hot air pressure increases from 30 kPa to 50 kPa, the longitudinal and transverse flexibility forces increase from 3.7 N and 10.3 N to 5.6 N and 15.6 N, respectively, representing increases of 51.35% and 51.46%. Figure 5(d) and (e)). Meanwhile, the air permeability and water vapor transmission rate increased from 13.1 mm / s and 1672.5 g / (m²) respectively. 2 The concentration decreased to 8.8 mm / s and 1424.2 g / (m²) over 24 hours. 2 24h) Figure 5 (f) This is mainly because the increased hot air pressure causes a decrease in fiber diameter, an increase in the number of fibers per unit area, and a reduction in pore structure, resulting in an increase in bonding points, which in turn leads to a worse fabric feel and a reduction in gas transmission channels. Figure 5 (d)~(f)).

[0065] Figure 6 The tensile fracture strength and bursting strength of the calamus leaf-like PLA ultrafine fiber composite materials prepared under different thermal bonding temperatures and hot air pressures are shown in Table 1. (a~c) correspond to Examples 1 and 6~9, and (d~f) correspond to Examples 2~5. Specific data are shown in Table 1.

[0066] Table 1 Mechanical property parameters of PLA ultrafine fiber composites from different types of calamus leaves

[0067] from Figure 6 As shown in Figures (a-c) and Table 1, the tensile strength and bursting strength of the samples gradually increase with increasing thermal bonding temperature. This is likely because the number of bonding points between fibers increases with increasing thermal bonding temperature, leading to enhanced entanglement and consolidation, thus increasing both tensile strength and bursting strength. Specifically, at thermal bonding temperatures of 100 ℃, 105 ℃, 110 ℃, 115 ℃, and 120 ℃, the longitudinal tensile strengths were 53.94 N, 54.17 N, 56.12 N, 56.42 N, and 56.43 N, respectively; the transverse tensile strengths were 15.85 N, 16.96 N, 17.24 N, 17.73 N, and 19.48 N, respectively; and the bursting strengths were 85.20 N, 86.90 N, 88.40 N, 92.4 N, and 93.5 N, respectively. It is worth noting that the longitudinal tensile strength of composite materials is always greater than that of fabrics in the transverse tensile strength. This is because during the melt-blown molding process of PLA microfiber materials, PLA undergoes stretching to form a fiber web with a certain degree of orientation, resulting in greater fabric strength along the machine direction. Similarly, increasing the hot air pressure also has a positive impact on the mechanical properties of composite materials.

[0068] from Figure 6As shown in Figures (d~f) and Table 1, as the hot air pressure increases from 30 kPa to 50 kPa, the longitudinal and transverse breaking strengths increase from 44.98 N and 16.57 N to 56.30 N and 23.18 N, respectively, while the bursting strength increases from 94.6 N to 116.03 N. This phenomenon indicates that the controlled meltblowing and thermal composite processes of this invention can controllably prepare calamus leaf-like PLA ultrafine fiber composite materials and significantly improve their comprehensive performance, providing a foundation for their use as high-performance medical protective materials.

[0069] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a polylactic acid ultrafine fiber composite material resembling calamus leaf, characterized in that, Includes the following steps: Paraffin wax is mixed with polydimethylsiloxane to obtain a modified material; The modified material is mixed with polylactic acid to obtain a blend; The blend is sequentially heated and melted, then melt-blown and in-situ stretched into a web to obtain oriented PLA ultrafine fibers; The oriented PLA microfiber is used as the upper and lower surface layers, and PLA spunbond fiber material is used as the middle reinforcing layer. After being stacked in the order of upper surface layer, middle reinforcing layer and lower surface layer, a template mesh is covered on the top layer of one side and thermally bonded to obtain a calamus leaf-like polylactic acid microfiber composite material.

2. The preparation method according to claim 1, characterized in that, The mass ratio of paraffin wax to polydimethylsiloxane is 1~5:0.5~2.

5.

3. The preparation method according to claim 1 or 2, characterized in that, The mass ratio of polylactic acid to modified material is 93.5~97.5:2.5~6.

5.

4. The preparation method according to claim 3, characterized in that, The temperatures of the screw extruder used for heating and melting are: Zone 1 temperature 175~195℃, Zone 2 temperature 205~225℃, and Zone 3 temperature 215~235℃.

5. The preparation method according to claim 1, characterized in that, The conditions for meltblown in-situ stretching into a web include: hot air pressure of 30~50 kPa and hot air temperature of 250~270℃.

6. The preparation method according to claim 1 or 5, characterized in that, The conditions for in-situ stretching of meltblown wire into a web include: meltblown die temperature of 215~235℃, die spinneret diameter of 0.22 mm, length-to-diameter ratio of 10:1; and receiving distance of 18cm for the receiving screen.

7. The preparation method according to claim 1, characterized in that, The thickness of the upper surface layer is 0.40~0.60mm, the thickness of the intermediate reinforcing layer is 0.10~0.14mm, and the thickness of the lower surface layer is 0.40~0.60mm; The template mesh curtain has a linear grid pattern.

8. The preparation method according to claim 1 or 7, characterized in that, The conditions for thermal bonding include: thermal bonding speed of 2~4 m / s, thermal bonding pressure of 0.20~0.40 MPa, and thermal bonding temperature of 100~120 ℃.

9. The calamus leaf-like polylactic acid ultrafine fiber composite material prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the calamus leaf-like polylactic acid microfiber composite material according to claim 9 in the field of medical and health protective materials.

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