A hydrophilic or hydrophobic polypropylene microfiber membrane, a hydrophilic / hydrophobic composite polypropylene microfiber membrane, and their preparation methods

Abstract

This invention discloses a hydrophilic or hydrophobic polypropylene ultrafine fiber membrane, a hydrophilic / hydrophobic composite polypropylene ultrafine fiber membrane, and their preparation methods. The preparation method includes: melt-spinning a bicomponent island-island composite using polyvinyl alcohol as the marine phase and polypropylene as the island phase; cooling, stretching, web laying, and hot-rolling to form a bicomponent island-island fiber nonwoven fabric; and dissolving and removing the marine phase of the bicomponent island-island fiber nonwoven fabric using a first or second solvent to obtain the hydrophilic or hydrophobic polypropylene ultrafine fiber membrane. This invention, by employing and controlling the island-island composite spinning technology, combined with polyvinyl alcohol post-treatment dissolution technology, prepares hydrophilic or hydrophobic polypropylene ultrafine fiber membranes at the micro / nanofiber scale, achieving the control and preparation of hydrophilic or hydrophobic polypropylene ultrafine fiber membranes of the same size. The prepared polypropylene ultrafine fiber membrane material has practical application value in filtration, medical and health care, and civilian textiles.

Description

Technical Field

[0001] This invention relates to the field of fiber composite membrane preparation technology, specifically to a hydrophilic or hydrophobic polypropylene microfiber membrane, a hydrophilic / hydrophobic composite polypropylene microfiber membrane, and a method for preparing the same. Background Technology

[0002] The ultrafine processing of fiber materials and the functional post-treatment of fiber membrane surfaces have always been common concerns in the fields of fiber and textile materials.

[0003] Polypropylene (PP) is a polyolefin polymer formed by the polymerization of propylene and is one of the three most widely used polymers. Currently, due to its advantages such as lowest cost, ease of processing into fibers, diverse types, corrosion resistance, and light weight, polypropylene is widely used as a raw material for nonwoven fabrics, especially for disposable medical and hygiene nonwoven fabrics. In industrialization, polypropylene fiber nonwoven fabrics mainly include two categories: spunbond nonwoven fabrics and meltblown nonwoven fabrics. Meltblown nonwoven fabrics, spunbond nonwoven fabrics, and meltblown-spunbond composite fiber nonwoven fabrics are widely used in fields such as adult incontinence products, medical masks, baby diapers, medical protective clothing, wet wipes, and cleaning products.

[0004] Currently, polypropylene nonwoven fabrics prepared by spunbond technology typically have fiber diameters exceeding 10 μm. These large fiber diameters, small specific surface areas, and low porosity result in poor hand feel, filtration, and adsorption capabilities. Polypropylene nonwoven fabrics prepared using meltblown technology have fiber diameters of approximately 2-5 μm. While falling into the category of ultrafine fibers, they do not yet reach the level of nanofibers. Furthermore, meltblown nonwoven materials exhibit poor mechanical properties and usually require compounding with other materials for use, significantly limiting their applications. Moreover, both meltblown and spunbond nonwoven materials lack controllable fiber membrane surface properties, hindering their wider applicability.

[0005] Therefore, there is an urgent need to study a method for preparing polypropylene fiber membranes that can control the surface properties of polypropylene fiber membranes to be hydrophobic or hydrophilic, and can adjust the diameter of polypropylene fiber membranes so that polypropylene fiber membranes can be adapted to a wider range of application scenarios. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing polypropylene microfiber membranes, so as to prepare polypropylene microfiber membranes with corresponding hydrophilic or hydrophobic properties according to different end-use application requirements.

[0007] To achieve the above objectives, the present invention provides a method for preparing a hydrophilic or hydrophobic polypropylene microfiber membrane. The method involves melt spinning of a bicomponent island-island composite using polyvinyl alcohol as the marine phase and polypropylene as the island phase, followed by cooling, stretching, web laying, and hot rolling to form a bicomponent island-island fiber nonwoven fabric. A first solvent is used to dissolve and remove the marine phase of the bicomponent island-island fiber nonwoven fabric, yielding a hydrophilic polypropylene microfiber membrane. A second solvent is then used to dissolve and remove the marine phase of the bicomponent island-island fiber nonwoven fabric, yielding a hydrophobic polypropylene microfiber membrane.

[0008] In a preferred embodiment, the first solvent is water.

[0009] As a preferred embodiment, the island bicomponent fiber nonwoven fabric is partially dissolved and removed from the marine phase in water at a temperature of 95-100℃ to obtain a hydrophilic polypropylene microfiber membrane.

[0010] In a preferred embodiment, the second solvent is dimethyl sulfoxide (DMSO).

[0011] As a preferred embodiment, the island-based bicomponent fiber nonwoven fabric is dissolved and removed in DMSO at a temperature of 50-65℃ to obtain a hydrophobic polypropylene microfiber membrane.

[0012] As a preferred embodiment, the hydrophilic polypropylene microfiber membrane is subjected to secondary dissolution and removal of polyvinyl alcohol in DMSO at a temperature of 50-65℃ to obtain a hydrophobic polypropylene microfiber membrane.

[0013] As a preferred embodiment, the polypropylene is any one of homopolymer polypropylene, random copolymer polypropylene, or block copolymer polypropylene with a melt index of 10-100 g / 10 min.

[0014] As a preferred embodiment, the mass ratio of polyvinyl alcohol to polypropylene is 1-9:9-1. The fiber diameter of the hydrophilic or hydrophobic polypropylene microfiber membrane can be adjusted by regulating the mass ratio of polyvinyl alcohol to polypropylene.

[0015] The present invention also provides a hydrophilic polypropylene microfiber membrane, which is prepared by the method for preparing the hydrophilic or hydrophobic polypropylene microfiber membrane.

[0016] The present invention also provides a hydrophobic polypropylene microfiber membrane, which is prepared by the method for preparing the hydrophilic or hydrophobic polypropylene microfiber membrane.

[0017] As a preferred embodiment, the fiber diameter of the hydrophilic polypropylene microfiber membrane or the hydrophobic polypropylene microfiber membrane is 0.8μm-5μm.

[0018] This invention provides a method for preparing a hydrophilic / hydrophobic composite polypropylene microfiber membrane. The method involves melt spinning of polyvinyl alcohol as the marine phase and polypropylene as the island phase into a two-component island-island composite, followed by cooling, stretching, web laying, and hot rolling to form an island-island two-component fiber nonwoven fabric. The marine phase of the island-island two-component fiber nonwoven fabric is dissolved and removed using a first solvent to obtain a hydrophilic polypropylene microfiber membrane. The marine phase of the island-island two-component fiber nonwoven fabric is then dissolved and removed using a second solvent to obtain a hydrophobic polypropylene microfiber membrane. The hydrophilic and hydrophobic polypropylene microfiber membranes are then stacked to obtain a multilayer hydrophilic / hydrophobic composite fiber membrane.

[0019] The present invention also provides a hydrophilic / hydrophobic composite polypropylene microfiber membrane, which is prepared by the method for preparing the hydrophilic / hydrophobic composite polypropylene microfiber membrane.

[0020] Compared with existing technologies, the beneficial effects of this invention are as follows: By employing and controlling island-based composite spinning technology, combined with marine polyvinyl alcohol post-treatment dissolution technology, this invention not only achieves the large-scale preparation of polypropylene ultrafine fiber membranes, controlling the fiber diameter to 0.8-5 μm, but also discloses a method for controlling the surface properties of polypropylene fibers that exceeds existing scientific knowledge and understanding in the industry. Specifically, the surface properties of the polypropylene ultrafine fiber membrane can be controlled by selecting the post-treatment solvent, resulting in permanent hydrophilicity or hydrophobicity. This enables the control and preparation of hydrophilic or hydrophobic polypropylene ultrafine fiber membranes at the micro-nano scale. The polypropylene ultrafine fiber membrane material prepared by this invention can adapt to a wider range of application scenarios and has practical application value in fields such as filtration, medical and health care, and civilian textiles.

[0021] Although the following detailed description uses island-type bicomponent fibers and nonwoven fabrics as examples, the principles, methods, processes, and chemical mechanisms described herein are also applicable to other bicomponent fiber configurations of polypropylene and polyvinyl alcohol, including daisy-petal, side-by-side, and core-sheath types. Those skilled in the art can readily obtain hydrophilic or hydrophobic fibers, fabrics, nonwovens, and their combined membranes with different configurations and proportions by extrapolating the invention and using different bicomponent fiber spinning components. Attached Figure Description

[0022] Figure 1 This is a structural diagram of the spinning equipment used in this invention;

[0023] Figure 2 This is a partial process flow diagram of the present invention;

[0024] Figure 3 The above are the surface Fourier transform infrared spectra of the polypropylene fiber membranes obtained in Examples 1-4 of this invention.

[0025] Figure 4 The graphs show the surface O element content of the polypropylene fiber membranes obtained in Examples 1-4 of this invention, obtained by XPS spectroscopy.

[0026] Figure 5 This is a scanning electron microscope image of the polypropylene ultrafine fiber membrane obtained in Example 1 of the present invention;

[0027] Figure 6 This is a scanning electron microscope image of the polypropylene ultrafine fiber membrane obtained in Example 2 of the present invention;

[0028] Figure 7 This is a scanning electron microscope image of the polypropylene ultrafine fiber membrane obtained in Example 3 of the present invention;

[0029] Figure 8 This is a scanning electron microscope image of the polypropylene ultrafine fiber membrane obtained in Example 4 of the present invention;

[0030] Figure 9 This is a contact angle test diagram of the polypropylene composite fiber membrane obtained in Example 5 of the present invention;

[0031] In the diagram: 1-Hopper A; 2-Screw motor A; 3-Heating zone 1 A; 4-Heating zone 2 A; 5-Hopper B; 6-Screw motor B; 7-Heating zone 1 B; 8-Heating zone 2 B; 9-Spinning box; 10-Cooling airflow device; 11-Gun-type drafter; 12-Wire mesh curtain; 13-Hot rolling roll; 14-Winding roll. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. Those skilled in the art should understand that the specific description below is illustrative and not restrictive, and should not be construed as limiting the scope of protection of this invention.

[0033] The method for preparing the hydrophilic or hydrophobic polypropylene fiber ultrafine membrane of the present invention includes the following steps:

[0034] 1) Feed thermoplastic polyvinyl alcohol and polypropylene chips into two hoppers of the melt spinning island bicomponent system respectively. Use polyvinyl alcohol as the sea phase and polypropylene as the island phase to perform island bicomponent melt spinning and lay them into a web to obtain island bicomponent fiber web.

[0035] 2) The obtained island bicomponent fiber web is fed into a hot rolling mill, where it is solidified and shaped under the temperature and pressure of the rolling mill to obtain an island bicomponent fiber nonwoven fabric with a certain strength.

[0036] 3) The marine phase of the island-island bicomponent fiber nonwoven fabric is dissolved and removed using the first solvent to obtain a hydrophilic polypropylene microfiber membrane; or, the marine phase of the island-island bicomponent fiber nonwoven fabric is dissolved and removed using the second solvent to obtain a hydrophobic polypropylene microfiber membrane.

[0037] The hydrophilic polypropylene fiber ultrafine membrane of the present invention is prepared by the above-described method for preparing hydrophilic or hydrophobic polypropylene fiber ultrafine membranes.

[0038] The hydrophobic polypropylene fiber ultrafine membrane of the present invention is prepared by the above-described method for preparing hydrophilic or hydrophobic polypropylene fiber ultrafine membranes.

[0039] The mass ratio of polyvinyl alcohol to polypropylene is 1-9:9-1. By adjusting the mass ratio of polyvinyl alcohol to polypropylene, the fiber diameter of hydrophilic or hydrophobic polypropylene microfiber membranes can be adjusted.

[0040] The hydrophilic or hydrophobic polypropylene microfiber membrane of the present invention has a fiber diameter of 0.8μm-5μm, which falls within the category of microfiber. It can effectively achieve the microfiberization of polypropylene fibers, and the fibers are soft and comfortable, which can effectively broaden the application fields of polypropylene fibers.

[0041] The method for preparing the hydrophilic / hydrophobic composite polypropylene microfiber membrane of the present invention includes the following steps:

[0042] 1) Feed thermoplastic polyvinyl alcohol and polypropylene chips into two hoppers of the melt spinning island bicomponent system respectively. Use polyvinyl alcohol as the sea phase and polypropylene as the island phase to perform island bicomponent melt spinning and lay them into a web to obtain island bicomponent fiber web.

[0043] 2) The obtained island bicomponent fiber web is fed into a hot rolling mill, where it is solidified and shaped under the temperature and pressure of the rolling mill to obtain an island bicomponent fiber nonwoven fabric with a certain strength.

[0044] 3) The marine phase of the island-island bicomponent fiber nonwoven fabric is dissolved and removed using the first solvent to obtain a hydrophilic polypropylene microfiber membrane; or, the marine phase of the island-island bicomponent fiber nonwoven fabric is dissolved and removed using the second solvent to obtain a hydrophobic polypropylene microfiber membrane.

[0045] 4) The hydrophilic polypropylene microfiber membrane and the hydrophobic polypropylene microfiber membrane from step 3) are stacked together to obtain a multilayer hydrophilic / hydrophobic composite polypropylene microfiber membrane.

[0046] The hydrophilic / hydrophobic composite polypropylene microfiber membrane of the present invention is prepared by the above-described method for preparing hydrophilic / hydrophobic composite polypropylene microfiber membrane.

[0047] Step 1): Thermoplastic polyvinyl alcohol is dried in a vacuum oven at 70-90℃ for 12 hours. After drying, the thermoplastic polyvinyl alcohol is easier to spin and more conducive to the formation of the sea phase. The dried polyvinyl alcohol is used as the sea phase and polypropylene as the island phase for melt island-island composite spinning. The island-island composite melt is cooled, drawn, laid into a web, and hot-rolled to form a bi-component island-island nonwoven fabric.

[0048] Step 1) The polypropylene is any one of homopolymer polypropylene, random copolymer polypropylene, or block copolymer polypropylene with a melt index of 10-100 g / 10 min, which is more conducive to polypropylene spinning and more conducive to the formation of island phases in polyethylene.

[0049] Step 3) The island bicomponent fiber nonwoven fabric is obtained by dissolving and removing polyvinyl alcohol in water at a temperature of 95-100℃ to obtain a hydrophilic polypropylene microfiber membrane.

[0050] The island bicomponent fiber nonwoven fabric is made by dissolving and removing polyvinyl alcohol in water at a temperature of 95-100℃ to obtain a hydrophilic polypropylene microfiber membrane.

[0051] The hydrophilic polypropylene ultrafine fiber membrane can be obtained by secondary treatment with dimethyl sulfoxide (DMSO) at 50-65℃ to obtain a hydrophobic polypropylene ultrafine fiber membrane.

[0052] Step 3) The island bicomponent fiber nonwoven fabric is obtained by dissolving and removing polyvinyl alcohol in dimethyl sulfoxide (DMSO) at a temperature of 50-65℃ to obtain a hydrophobic polypropylene microfiber membrane.

[0053] The island-type bicomponent fiber nonwoven fabric can be dissolved multiple times in water until the weight of the fiber membrane no longer changes.

[0054] Island-type bicomponent fiber nonwoven fabric or hydrophilic polypropylene microfiber membrane can be dissolved multiple times in water until the weight of the fiber membrane no longer changes.

[0055] Step 4) The number and order of the hydrophilic polypropylene microfiber membrane and the hydrophobic polypropylene microfiber membrane can be selected according to actual needs, and no specific restrictions are imposed here.

[0056] Figure 1The equipment and process flow diagram used in this invention are shown in Table 1. The spinning process parameters for the island-island bicomponent fiber nonwoven fabric are also shown. Polyvinyl alcohol (PVA) and polypropylene (PP) chips are fed into hoppers A1 and B5, respectively. PVA, powered by screw motor A2, passes through heating zones A3 and A4 sequentially before entering spinning box 9. PP, powered by screw motor B6, passes through heating zones B7 and B8 sequentially before entering spinning box 9. PVA and PP are spun in spinning box 9. The resulting fibers are processed by cooling airflow device 10 and gun-type drafter 11, and then laid on a mesh screen 12 to form a web, obtaining island-island bicomponent fibers. The island-island bicomponent fibers are fed into hot rollers 13 and winding rollers 14 for consolidation and shaping, resulting in island-island bicomponent fiber nonwoven fabric.

[0057] Table 1

[0058] Screw A (Marine Component) Temperature (°C) 210-250 Screw B (island component) temperature (°C) 190-250 Metering pump A (marine component) temperature (°C) 210-250 Metering pump B (island component) temperature (°C) 190-250 Spinning box (°C) 220-250 Cooling airflow temperature (°C) 5-20 Stretch pressure (psi) 5-20 Hot rolling roll temperature (°C) 120-160 Mass ratio of marine component to island component 1:9-9:1

[0059] Example 1

[0060] This embodiment describes a method for preparing a hydrophilic polypropylene microfiber membrane, comprising the following steps:

[0061] (1) Place thermoplastic polyvinyl alcohol in a vacuum oven at 80°C and dry for 12 hours. Then feed the dried polyvinyl alcohol and polypropylene chips into the two hoppers of the melt-spun island bicomponent system at a feeding rate of 38 g / 10 min.

[0062] (2) A bicomponent island-island fiber was obtained by melt spinning and web formation of thermoplastic polyvinyl alcohol (PVA) as the marine phase and polypropylene as the island phase. The mass ratio of PVA to polypropylene was controlled at 9:1 by a metering pump; the stretching pressure was 10 psi; the processing temperature of each zone of PVA was 220℃-240℃; the processing temperature of each zone of polypropylene was 200℃-230℃; and the spinning box temperature was 240℃.

[0063] (3) The obtained island bicomponent fiber is fed into a hot rolling roll, and it is solidified and shaped under the high temperature and high pressure of the roll to obtain an island bicomponent fiber nonwoven fabric with a certain strength. The hot rolling temperature is 140℃.

[0064] (4) The island-type bicomponent fiber nonwoven fabric was dissolved in water to remove polyvinyl alcohol, and finally a hydrophilic polypropylene microfiber membrane was obtained. The water dissolution treatment temperature was 95℃, the treatment was performed 6 times, and each treatment lasted 20 minutes.

[0065] The polypropylene fiber membrane obtained in this embodiment was tested in a JY-PHb type contact angle tester manufactured by Chengde Jinhe Instrument Manufacturing Co., Ltd. The measurement results are shown in Table 2. The contact angle result is 0°, indicating that the polypropylene fiber membrane obtained in this embodiment is hydrophilic.

[0066] By calculating the weight of the island-island bicomponent fiber nonwoven fabric and the polypropylene fiber membrane in this embodiment, the weight loss rate of the polypropylene fiber membrane was found to be 91.2%, which is basically consistent with the weight ratio of polyvinyl alcohol of 90%, indicating that the polyvinyl alcohol component in the island-island bicomponent fiber nonwoven fabric was basically dissolved and removed.

[0067] To reveal the scientific principles of the polypropylene ultrafine fiber membrane surface performance treatment technology disclosed in this invention, spectroscopic analysis of the fiber surface composition and chemical composition was performed. Specifically:

[0068] First, the hydrophilic polypropylene ultrafine fiber membrane obtained in this embodiment was analyzed for fiber surface functional groups using an IS10 Fourier transform infrared spectrometer manufactured by Thermo Scientific in the United States. The infrared test results are as follows: Figure 3 As shown, Figure 3 The polypropylene fiber membrane of this embodiment is shown at 3352 cm⁻¹. -1 There is a weak -OH characteristic peak, which indicates that there are trace amounts of PVA molecular chains on the surface of the fiber membrane.

[0069] Second, the hydrophilic polypropylene ultrafine fiber membrane obtained in this embodiment was subjected to elemental analysis of the fiber surface using Scientific K-Alpha X-ray photoelectron spectroscopy produced by Thermo Scientific in the United States. The measurement results are as follows: Figure 4 As shown, Figure 4 The results show that the surface of the polypropylene fiber membrane in this embodiment contains 12.8% O element, which further proves that the surface of the fiber membrane is attached with trace amounts of PVA molecular chains.

[0070] The hydrophilic polypropylene ultrafine fiber membrane obtained in this embodiment was observed using a scanning electron microscope (MVE0352891782) manufactured by Phenom GmbH, Germany. (See attached image.) Figure 5 As can be seen, the polypropylene fiber membrane obtained in this embodiment is composed of solid columnar fibers with smooth surfaces, and the measured fiber diameter of the polypropylene fiber membrane is 0.82 μm.

[0071] Based on the above analysis, the following scientific interpretations are proposed. These interpretations are intended to help industry practitioners understand this new technology, but do not affect the existence of other scientific interpretations or the creativity and practicality of technological inventions that do not rely on any scientific interpretation. During the relatively high temperature and pressure of the island-based spinning melt flow process, although polypropylene and polyvinyl alcohol are two incompatible phases, limited molecular chain interdiffusion occurs at the interface between the two components. This results in a very small portion of polyvinyl alcohol molecular chains diffusing into the polypropylene, forming a situation where polyvinyl alcohol is "semi-embedded" on the surface of the polypropylene fibers. Consequently, when washing polyvinyl alcohol with hot water, only the un-"embedded" molecular chains are removed, while the very few "semi-embedded" polyvinyl alcohol molecular chains remain at the polypropylene interface, thus giving the polypropylene microfiber membrane excellent surface hydrophilicity. In summary, this embodiment prepares a hydrophilic polypropylene micro / nanofiber membrane by combining island-based composite spinning technology with aqueous solution post-treatment technology.

[0072] Example 2

[0073] This embodiment describes a method for preparing a hydrophobic polypropylene microfiber membrane, comprising the following steps:

[0074] (1) Place thermoplastic polyvinyl alcohol in a vacuum oven at 80°C and dry for 12 hours. Then feed the dried polyvinyl alcohol and polypropylene chips into the two hoppers of the melt-spun island bicomponent system at a feeding speed of 38 g / 10 min.

[0075] (2) A sea-island bicomponent melt spinning process was carried out using thermoplastic polyvinyl alcohol as the sea phase and polypropylene as the island phase, and the fibers were laid up to form a web to obtain sea-island bicomponent fibers. The mass ratio of polyvinyl alcohol to polypropylene was controlled at 9:1 by a metering pump; the stretching pressure was 10 psi; the processing temperature of each zone of polyvinyl alcohol was 220℃-240℃; the processing temperature of each zone of polypropylene was 200℃-230℃; and the spinning box temperature was 240℃.

[0076] (3) The obtained island bicomponent fiber is fed into a hot rolling roll, and it is solidified and shaped under the high temperature and high pressure of the roll to obtain an island bicomponent fiber nonwoven fabric with a certain strength. The hot rolling temperature is 140℃.

[0077] (4) The island-type bicomponent fiber nonwoven fabric was dissolved in DMSO to remove polyvinyl alcohol, and finally a hydrophobic polypropylene fiber membrane was obtained. The DMSO treatment temperature was 55℃, the treatment was performed 4 times, and each treatment lasted 15 minutes.

[0078] The polypropylene fiber membrane obtained in this embodiment was tested in a JY-PHb type contact angle tester manufactured by Chengde Jinhe Instrument Manufacturing Co., Ltd. The measurement results are shown in Table 2. The contact angle result is 113.8°, indicating that the polypropylene fiber membrane is hydrophobic.

[0079] By calculating the weights of the island-island bicomponent fiber nonwoven fabric and the polypropylene fiber membrane in this embodiment, the weight loss rate of the polypropylene fiber membrane was found to be 91.3%. This is basically consistent with the weight ratio of polyvinyl alcohol (PVA) of 90%, indicating that the PVA component in the island-island bicomponent fiber nonwoven fabric has been essentially dissolved and removed.

[0080] To reveal the scientific principles of the polypropylene ultrafine fiber membrane surface performance treatment technology disclosed in this invention, spectroscopic analysis of the fiber surface composition and chemical composition was performed. Specifically:

[0081] First, the hydrophobic polypropylene ultrafine fiber membrane obtained in this embodiment was analyzed for fiber surface functional groups using an IS10 Fourier transform infrared spectrometer manufactured by Thermo Scientific in the United States. The infrared test results are as follows: Figure 3 As shown, Figure 3 The polypropylene fiber membrane of this embodiment is shown at 3352 cm⁻¹. -1 There is a weak -OH characteristic peak at the location, which is consistent with the result in Example 1.

[0082] Second, the hydrophobic polypropylene ultrafine fiber membrane obtained in this embodiment was subjected to elemental analysis of the fiber surface using Scientific K-Alpha X-ray photoelectron spectroscopy manufactured by Thermo Scientific in the United States. The measurement results are as follows: Figure 4 As shown, Figure 4 The polypropylene fiber membrane of this embodiment contains 4.6% oxygen on its surface. Compared with Example 1, the oxygen content on the surface of the polypropylene fiber membrane of this embodiment is significantly reduced.

[0083] The hydrophilic polypropylene ultrafine fiber membrane obtained in this embodiment was observed using a scanning electron microscope (MVE0352891782) manufactured by Phenom GmbH, Germany. (See attached image.) Figure 6 As can be seen, the polypropylene fiber membrane obtained in this embodiment is composed of solid columnar fibers with smooth surfaces, and the measured fiber diameter of the polypropylene fiber membrane is 0.82 μm.

[0084] Based on the above analysis, the following scientific interpretations are proposed. These interpretations are intended to help industry practitioners understand this new technology, but do not affect the existence of other scientific interpretations or the creativity and practicality of the technological invention that does not rely on any scientific interpretation. During the relatively high temperature and high pressure melt flow process in spinning, although polypropylene and polyvinyl alcohol are two incompatible phases, limited molecular chain interdiffusion occurs at the interface between the two components. This allows a very small portion of the polyvinyl alcohol molecular chains at the interface to diffuse into the polypropylene, forming a "semi-embedded" state on the surface of the polypropylene fibers. When cleaning the polyvinyl alcohol with DMSO, not only are the un-"embedded" molecular chains removed, but the "semi-embedded" polyvinyl alcohol molecular chains can also be pushed to further extend and diffuse into the amorphous phase of the polypropylene, thus entering the inner surface of the polypropylene. This results in the polypropylene micro / nanofiber membrane prepared in this embodiment becoming hydrophobic. In summary, this embodiment prepares a hydrophobic polypropylene micro / nanofiber membrane by combining island-of-sea composite spinning technology with DMSO solution post-treatment technology.

[0085] Example 3

[0086] This embodiment describes a method for preparing a hydrophobic polypropylene microfiber membrane, comprising the following steps:

[0087] (1) Place thermoplastic polyvinyl alcohol in a vacuum oven and dry it at 80°C for 12 hours. Feed the dried polyvinyl alcohol and polypropylene chips into the two hoppers of the melt-spun island bicomponent system at a feeding rate of 38 g / 10 min.

[0088] (2) A sea-island bicomponent melt spinning process was carried out using thermoplastic polyvinyl alcohol as the sea phase and polypropylene as the island phase, and the fibers were laid up to form a web to obtain sea-island bicomponent fibers. The mass ratio of polyvinyl alcohol to polypropylene was controlled at 9:1 by a metering pump; the stretching pressure was 10 psi; the processing temperature of each zone of polyvinyl alcohol was 220℃-240℃; the processing temperature of each zone of polypropylene was 200℃-230℃; and the spinning box temperature was 240℃.

[0089] (3) The obtained island bicomponent fiber is fed into a hot rolling roll, and it is solidified and shaped under the high temperature and high pressure of the roll to obtain an island bicomponent fiber nonwoven fabric with a certain strength. The hot rolling temperature is 140℃.

[0090] (4) The island fiber nonwoven fabric was dissolved in water to remove polyvinyl alcohol, and a hydrophilic polypropylene microfiber membrane was obtained. The obtained hydrophilic polypropylene microfiber membrane was then treated with DMSO to obtain a hydrophobic polypropylene fiber membrane. The water dissolution temperature was 95℃, the treatment was performed 6 times, and each treatment lasted 20 min. The DMSO treatment temperature was 55℃, the treatment was performed 3 times, and each treatment lasted 15 min.

[0091] The polypropylene fiber membrane obtained in this embodiment was tested in a JY-PHb type contact angle tester produced by Chengde Jinhe Instrument Manufacturing Co., Ltd. The contact angle results in Table 2 show that the membrane is 111.3°, indicating that the surface of the ultrafine fiber membrane is hydrophobic.

[0092] By calculating the weights of the island-island bicomponent fiber nonwoven fabric and the hydrophobic polypropylene fiber membrane in this embodiment, the weight loss rate of the polypropylene fiber membrane was found to be 90.9%. This is basically consistent with the weight ratio of polyvinyl alcohol (PVA) of 90%, indicating that the PVA component in the island-island bicomponent fiber nonwoven fabric has been essentially dissolved and removed.

[0093] To reveal the scientific principles of the polypropylene ultrafine fiber membrane surface performance treatment technology disclosed in this invention, spectroscopic analysis of the fiber surface composition and chemical composition was performed. Specifically:

[0094] First, the hydrophobic polypropylene ultrafine fiber membrane obtained in this embodiment was analyzed for fiber surface functional groups using an IS10 Fourier transform infrared spectrometer manufactured by Thermo Scientific in the United States. The infrared test results are as follows: Figure 3 As shown, Figure 3 The polypropylene fiber membrane of this embodiment is shown at 3352 cm⁻¹. -1 There is a weak -OH characteristic peak at the location, which is consistent with the results in Examples 1 and 2.

[0095] Second, the hydrophobic polypropylene ultrafine fiber membrane obtained in this embodiment was subjected to elemental analysis of the fiber surface using Scientific K-Alpha X-ray photoelectron spectroscopy manufactured by Thermo Scientific in the United States. The measurement results are as follows: Figure 4 As shown, Figure 4 The polypropylene fiber membrane of this embodiment contains 3.8% O element on its surface, which is basically the same as that in Example 2.

[0096] The hydrophobic polypropylene ultrafine fiber membrane obtained in this embodiment was observed using a scanning electron microscope (MVE0352891782) manufactured by Phenom GmbH, Germany. (See attached image.) Figure 7 As can be seen, the polypropylene fiber membrane obtained in this embodiment is composed of solid columnar fibers with smooth surfaces, and the measured fiber diameter of the polypropylene fiber membrane is 0.88 μm.

[0097] Based on the above analysis, during the high-temperature and high-pressure island-island spinning process, polypropylene and polyvinyl alcohol (PVA) undergo interdiffusion at the interface between the two components. This results in a small portion of PVA molecules diffusing into the polypropylene, forming a "semi-embedded" state on the surface of the polypropylene fibers. Consequently, when washing the PVA with hot water, only the unembedded molecules are removed. However, during a secondary cleaning with DMSO, the "semi-embedded" PVA molecules diffuse further into the amorphous phase of the polypropylene, thus entering the inner surface of the polypropylene. This leads to the transformation of the polypropylene micro / nanofiber membrane prepared in this embodiment into a hydrophobic surface. In summary, this embodiment combines the post-treatment methods for island-island fiber nonwoven fabrics from Examples 1 and 2 to obtain a hydrophobic polypropylene fiber membrane.

[0098] Example 4

[0099] This embodiment describes a method for preparing a hydrophilic polypropylene microfiber membrane, comprising the following steps:

[0100] (1) Place thermoplastic polyvinyl alcohol in a vacuum oven and dry it at 80°C for 12 hours. Feed the dried polyvinyl alcohol and polypropylene chips into the two hoppers of the melt-spun island bicomponent system at a feeding rate of 38 g / 10 min.

[0101] (2) A sea-island bicomponent melt spinning process was carried out using thermoplastic polyvinyl alcohol as the sea phase and polypropylene as the island phase, and the fibers were laid up to form a web to obtain sea-island bicomponent fibers. The mass ratio of polyvinyl alcohol to polypropylene was controlled at 5:5 by a metering pump; the stretching pressure was 10 psi; the processing temperature of each zone of polyvinyl alcohol was 220℃-240℃; the processing temperature of each zone of polypropylene was 200℃-230℃; and the spinning box temperature was 240℃.

[0102] (3) The obtained island bicomponent fiber is fed into a hot rolling roll, and it is solidified and shaped under the high temperature and high pressure of the roll to obtain an island bicomponent fiber nonwoven fabric with a certain strength. The hot rolling temperature is 140℃.

[0103] (4) The island-type bicomponent fiber nonwoven fabric was dissolved in water to remove polyvinyl alcohol, and finally a hydrophilic polypropylene microfiber membrane was obtained. The water dissolution temperature was 95℃, and the treatment was performed 6 times, each time for 20 minutes.

[0104] The hydrophilic polypropylene microfiber membrane obtained in this embodiment was tested in a JY-PHb type contact angle tester produced by Chengde Jinhe Instrument Manufacturing Co., Ltd. The contact angle results in Table 2 show that the membrane is 0°, indicating that the surface of the microfiber membrane is hydrophilic.

[0105] By calculating the weights of the island-island bicomponent fiber nonwoven fabric and the polypropylene fiber membrane in this embodiment, the weight loss rate of the polypropylene fiber membrane was found to be 59.1%. This is basically consistent with the weight ratio of polyvinyl alcohol (PVA) of 50%, indicating that the PVA component in the island-island bicomponent fiber nonwoven fabric was dissolved and removed.

[0106] To reveal the scientific principles of the polypropylene ultrafine fiber membrane surface performance treatment technology disclosed in this invention, spectroscopic analysis of the fiber surface composition and chemical composition was performed. Specifically:

[0107] First, the hydrophilic polypropylene ultrafine fiber membrane obtained in this embodiment was analyzed for fiber surface functional groups using an IS10 Fourier transform infrared spectrometer manufactured by Thermo Scientific in the United States. The infrared test results are as follows: Figure 3 As shown, Figure 3 The polypropylene fiber membrane of this embodiment is shown at 3352 cm⁻¹. -1 There is a weak -OH characteristic peak, which indicates that there are trace amounts of PVA molecular chains on the surface of the fiber membrane.

[0108] Second, the hydrophilic polypropylene ultrafine fiber membrane obtained in this embodiment was subjected to elemental analysis of the fiber surface using Scientific K-Alpha X-ray photoelectron spectroscopy produced by Thermo Scientific in the United States. The measurement results are as follows: Figure 4 As shown, Figure 4 The results show that the surface of the polypropylene fiber membrane in this embodiment contains 13.4% O element, which further proves that a trace amount of PVA molecular chains are attached to the surface of the fiber membrane.

[0109] The hydrophilic polypropylene ultrafine fiber membrane obtained in this embodiment was observed using a scanning electron microscope (MVE0352891782) manufactured by Phenom GmbH, Germany. (See attached image.) Figure 8 As can be seen, the polypropylene fiber membrane obtained in this embodiment is composed of solid columnar fibers with smooth surfaces, and the measured average fiber diameter is 3.2 μm.

[0110] Based on the above analysis, during the high-temperature and high-pressure island-island spinning process, polypropylene and polyvinyl alcohol (PVA) undergo interdiffusion at the interface between the two components. This results in a very small portion of PVA molecules diffusing into the polypropylene, forming a "semi-embedded" state on the surface of the polypropylene fiber. Consequently, when washing PVA with hot water, only the unembedded molecules are removed, while the very few "semi-embedded" PVA molecules remain at the interface, contributing to the excellent hydrophilicity of the polypropylene micro / nanofiber membrane. In summary, compared to Example 1, this example increases the proportion of polypropylene in the island-island composite fiber, resulting in a significantly increased diameter of the final hydrophilic polypropylene fiber. The results demonstrate that the diameter of the polypropylene ultrafine fiber can be controlled by adjusting the ratio of polypropylene to PVA.

[0111] Table 2 shows the test data of the polypropylene fiber membranes obtained in Examples 1-4.

[0112] Contact angle (°) Average fiber diameter (μm) Weight loss rate (%) Example 1 0 0.82 91.2 Example 2 113.8 0.85 91.3 Example 3 111.3 0.88 90.9 Example 4 0 3.2 59.1

[0113] Example 5

[0114] This embodiment describes a method for preparing a unidirectional moisture-wicking polypropylene microfiber composite membrane, comprising the following steps:

[0115] The hydrophilic polypropylene microfiber membrane of Example 1 and the hydrophobic polypropylene microfiber membrane of Example 2 were composited in a hot rolling mill at a temperature of 140°C to prepare a polypropylene microfiber composite membrane with one-way moisture-wicking function.

[0116] The polypropylene ultrafine fiber composite membrane obtained in this embodiment was tested using a JY-PHb contact angle meter manufactured by Chengde Jinhe Instrument Manufacturing Co., Ltd. The hydrophobic layer faced upwards (in contact with the water droplet), and the hydrophilic layer faced downwards. The changes in the water droplet within the composite fiber membrane were recorded in real time, and the process is shown in the attached figure. Figure 9 As shown in the figure. The results indicate that the large difference in hydrophilicity between the two fiber membranes triggers the directional transport of water, with water droplets being transported unidirectionally from the hydrophobic layer to the hydrophilic layer.

[0117] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0118] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions claimed by the present invention.

Claims

1. A method for preparing a hydrophobic polypropylene ultrafine fiber membrane, characterized in that, Polyvinyl alcohol as the marine phase and polypropylene as the island phase are used for melt island-island bicomponent composite spinning, and then cooled, stretched, laid up, and hot rolled to form island-island bicomponent fiber nonwoven fabric. The marine phase of the island-island bicomponent fiber nonwoven fabric is dissolved and removed using a first solvent to obtain a hydrophilic polypropylene ultrafine fiber membrane. The first solvent is water; The mass ratio of polyvinyl alcohol to polypropylene is 1-9:9-1 to adjust the fiber diameter of the hydrophilic polypropylene microfiber membrane; the fiber diameter of the hydrophilic polypropylene microfiber membrane is 0.8μm-5μm. The hydrophilic polypropylene microfiber membrane was subjected to a secondary treatment with polyvinyl alcohol in DMSO at a temperature of 50-65℃ to obtain a hydrophobic polypropylene microfiber membrane.

2. The method for preparing the hydrophobic polypropylene ultrafine fiber membrane according to claim 1, characterized in that: The island bicomponent fiber nonwoven fabric is dissolved and removed in water at a temperature of 95-100℃ to obtain a hydrophilic polypropylene microfiber membrane.

3. The hydrophobic polypropylene microfiber membrane prepared by the method for preparing hydrophobic polypropylene microfiber membrane according to claim 1.

4. A method for preparing a hydrophilic-hydrophobic composite polypropylene ultrafine fiber membrane, characterized in that, Polyvinyl alcohol as the marine phase and polypropylene as the island phase are used for melt island-island bicomponent composite spinning, and then cooled, stretched, laid up, and hot rolled to form island-island bicomponent fiber nonwoven fabric. The marine phase of the island-island bicomponent fiber nonwoven fabric is dissolved and removed using a first solvent to obtain a hydrophilic polypropylene ultrafine fiber membrane. The first solvent is water; The mass ratio of polyvinyl alcohol to polypropylene is 1-9:9-1 to adjust the fiber diameter of the hydrophilic polypropylene microfiber membrane; the fiber diameter of the hydrophilic polypropylene microfiber membrane is 0.8μm-5μm. The hydrophilic polypropylene microfiber membrane was subjected to a secondary treatment with polyvinyl alcohol in DMSO at a temperature of 50-65℃ to obtain a hydrophobic polypropylene microfiber membrane. The hydrophilic polypropylene microfiber membrane and the hydrophobic polypropylene microfiber membrane are stacked to obtain a multilayer hydrophilic-hydrophobic composite polypropylene microfiber membrane.

5. The hydrophilic-hydrophobic composite polypropylene ultrafine fiber membrane prepared by the method for preparing the hydrophilic-hydrophobic composite polypropylene ultrafine fiber membrane according to claim 4.

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