CN112877903A

CN112877903A - Oriented water-guiding non-woven material with photo-thermal conversion function and preparation method thereof

Info

Publication number: CN112877903A
Application number: CN202110044546.7A
Authority: CN
Inventors: 方远远; 张鹏程; 曹元生; 傅峰; 张伟; 戚晶磊; 胡宁宁; 李伟钦; 李玉; 李斌
Original assignee: Shanghai Investigation Design and Research Institute Co Ltd SIDRI
Current assignee: Shanghai Investigation Design and Research Institute Co Ltd SIDRI
Priority date: 2021-01-13
Filing date: 2021-01-13
Publication date: 2021-06-01

Abstract

The invention relates to the technical field of energy utilization, in particular to a directional water guide non-woven material with a photo-thermal conversion function and a preparation method thereof. The directional water guide non-woven material sequentially comprises a hydrophobic layer, a hydrophilic layer and a carbon nano tube layer; the hydrophobic layer and the hydrophilic layer respectively comprise hydrophobic fibers and hydrophilic fibers which are mutually entangled and distributed; the hydrophobic layer comprises a hydrophobic surface, and the hydrophilic layer comprises a hydrophilic surface; the hydrophobic fibers gradually decrease from the hydrophobic surface to the hydrophilic surface, and the hydrophilic fibers gradually increase from the hydrophobic surface to the hydrophilic surface; both the hydrophobic and hydrophilic fibers have a density less than that of water. The invention combines the directional water guide function and the photo-thermal conversion performance, and realizes the high-efficiency matching of the moisture transmission rate and the moisture evaporation rate. Meanwhile, the multi-walled carbon nanotubes attached to the hydrophilic surface of the non-woven material endow the material with excellent absorbance, and the material can permanently float on the water surface by selecting fibers with low thermal conductivity and density lower than that of water, has low heat loss and realizes centralized heat energy management.

Description

Oriented water-guiding non-woven material with photo-thermal conversion function and preparation method thereof

Technical Field

The invention relates to the technical field of energy utilization, in particular to a directional water guide non-woven material with a photo-thermal conversion function and a preparation method thereof.

Background

With the rapid development of economic society, serious environmental problems are brought about while energy is developed and utilized, and the development and the use of renewable clean energy are concerned. The most basic renewable energy on the earth is solar energy, and solar photo-thermal conversion materials can concentrate solar radiation energy through reflection, absorption or other modes and convert the solar radiation energy into heat so as to meet the requirements of subsequent applications. At present, interface type water evaporation by utilizing a photothermal conversion technology has a relatively high application prospect, and a new solution is provided for the development of the fields of seawater desalination, sewage purification and the like.

In an interface type water evaporation system, photothermal conversion materials such as plasma nano materials, graphene oxide, carbon nanotube-based materials, bionic materials, polymer hydrogel materials and the like are directly floated on the water surface or attached to a base material capable of floating on the water surface, light energy is absorbed and converted into heat energy, the heat energy is concentrated at a gas-liquid interface, more energy is used for rapidly raising the temperature of local water at the interface, a large amount of steam is generated on the surface of the material, and higher energy conversion and utilization efficiency is realized. In the process of water evaporation, the temperature of the water in the main body part is hardly changed, and the heat loss is effectively reduced. Therefore, research on the interface type photothermal conversion material has mainly focused on four aspects: efficient light energy absorption, continuous moisture transport, concentrated thermal energy management and efficient moisture evaporation.

The prior art discloses a preparation method of a photothermal distillation membrane and a high-efficiency solar desalination device containing the photothermal distillation membrane. In the device, the polypyrrole fiber paper with high absorbance and high water stability is obtained by soaking the fiber paper in pyrrole monomer solution, and when the polypyrrole fiber paper is used for photothermal conversion, the polypyrrole fiber paper and the foamable polyethylene foam form a double-layer structure so as to effectively reduce heat loss.

In addition, the prior art discloses a preparation method of a biochar/polymer composite membrane applied to solar water evaporation. The composite membrane is internally of a porous hollow structure, and the surface of the composite membrane is provided with hydroxyl, amino and carboxyl functional groups, so that the surface of the biochar/polymer composite membrane is provided with hydrophilic groups for water transmission, and the composite membrane has excellent photo-thermal performance and can efficiently convert solar energy into heat energy for water evaporation.

In addition, the prior art discloses a light absorption and heat insulation integrated photo-thermal evaporation material and a preparation method and application thereof. The vertical-orientation graphene with the surface modified by the hydrophilic functional groups is used as a light absorber, the graphene foam is used as a heat insulator, the light absorber and the heat insulator are connected in a covalent bond mode, the problem that the light absorber and the heat insulator are easy to separate and the problem of heat loss caused by liquid permeating into the heat insulator are solved, the stability and the photo-thermal conversion efficiency of a local heating system are improved, and the rapid and efficient photo-thermal evaporation is realized.

In addition, the prior art discloses a method based on CuInSe₂The seawater desalination structure of the/MXene nano composite material. It comprises a photo-thermal conversion layer, a water delivery layer, a supporting layer and a water delivery belt. The supporting layer is made of foam materials and is used for supporting the photothermal conversion layer and the water delivery layer; the water conveying layer and the water conveying belt are both made of hydrophilic materials, and the water conveying belt is used for conveying the water body to be desalinated to the water conveying layer; the photothermal conversion layer comprises CuInSe₂the/MXene nano composite material film is used for absorbing light energy and converting the light energy into heat energy so as to heat and evaporate the water body to be desalinated. The seawater desalination structure has a wider sunlight absorption range, high-efficiency photothermal conversion performance and excellent local thermal effect

In the prior art, the first three are developed interface type photothermal water evaporation systems from different angles, but all the systems are researched only from a certain single entry point, and the comprehensive performance is not considered. In the last item, although a comprehensive structure is designed, the moisture transmission of the material depends on the hydrophilic performance of the hydrophilic material, the matching problem of the moisture transmission speed and the moisture evaporation rate is not considered, and when the material is placed on a water surface for photo-thermal evaporation, a thin water layer is easily formed on the surface due to the hydrophilic characteristic of the material, so that the heat loss is caused. Therefore, the development of an oriented water-guiding non-woven material with a photothermal conversion function is urgently needed.

Disclosure of Invention

In view of the above disadvantages of the prior art, an object of the present invention is to provide a directional water-guiding nonwoven material with a photothermal conversion function and a preparation method thereof, so as to solve the problems in the prior art that optimal matching between a moisture transmission rate and a moisture evaporation rate and efficient management of heat energy cannot be achieved, so as to achieve higher photothermal conversion efficiency, and at the same time, large-scale preparation and low cost are possible.

The invention is realized by the following technical scheme:

the invention provides a directional water guide non-woven material, which sequentially comprises a hydrophobic layer, a hydrophilic layer and a carbon nano tube layer; the hydrophobic layer and the hydrophilic layer respectively comprise hydrophobic fibers and hydrophilic fibers which are mutually entangled and distributed; the hydrophobic layer comprises a hydrophobic surface and the hydrophilic layer comprises a hydrophilic surface; the hydrophobic fibers gradually decrease from the hydrophobic surface to the hydrophilic surface, and the hydrophilic fibers gradually increase from the hydrophobic surface to the hydrophilic surface; the hydrophobic fibers and the hydrophilic fibers both have a density less than the density of water.

In some embodiments of the present invention, the hydrophobic layer has a thickness of 1 to 1.5 mm.

In some embodiments of the present invention, the hydrophilic layer has a thickness of 1 to 1.5 mm.

In some embodiments of the invention, the thickness of the carbon nanotube layer is 0.5-1 mm.

In some embodiments of the invention, the mass ratio of hydrophilic fibers to hydrophobic fibers is 3: 1-1: 1.

in some embodiments of the invention, the carbon nanotube layer is selected from carboxylated multi-walled carbon nanotubes.

In some embodiments of the invention, the hydrophobic fibers have a density of less than 1 g-mL.

In some embodiments of the invention, the hydrophobic fibers have a thermal conductivity of less than 0.3 W.m^-1·k^-1。

In some embodiments of the invention, the hydrophilic fibers have a density of less than 1 g-mL.

In some embodiments of the invention, the hydrophilic fibers have a thermal conductivity of less than 0.3 W.m^-1·k^-1。

In some embodiments of the invention, the hydrophilic fibers are selected from hydrophilic bicomponent sheath-core structured fibers.

In some embodiments of the invention, the hydrophilic fibers are selected from hydrophilic polypropylene/polyethylene bicomponent fibers.

In some embodiments of the invention, the hydrophobic fibers are selected from hydrophobic bicomponent sheath-core structured fibers.

In some embodiments of the invention, the hydrophobic fibers are selected from hydrophobic polypropylene/polyethylene bicomponent fibers.

In some embodiments of the invention, the pore size of the directionally water-directing nonwoven material is 40-50 microns.

In another aspect, the present invention provides a method for preparing a directionally water-directing nonwoven material according to the present invention, the method comprising the steps of:

1) respectively preparing hydrophilic fibers and hydrophobic fibers through a web forming process to obtain a hydrophilic fluffy fiber web and a hydrophobic fluffy fiber web;

2) laminating the hydrophilic fluffy fiber net and the hydrophobic fluffy fiber net provided in the step 1) and mechanically reinforcing to obtain a hydrophilic layer and a hydrophobic layer;

3) providing a dispersion liquid of the carbon nano tubes, and spraying the dispersion liquid of the carbon nano tubes on the hydrophilic surface of the hydrophilic layer provided in the step 2) for heat treatment.

In some embodiments of the invention, in the step 1), the mass ratio of the hydrophilic fibers to the hydrophobic fibers is 3: 1-1: 1.

in some embodiments of the invention, in step 1), the web forming process is dry-laid.

In some embodiments of the present invention, in the step 3), the dispersion of the carbon nanotubes is obtained by dispersing carbon nanotubes in a solvent through carboxylation modification.

In some embodiments of the invention, the solvent is selected from the group consisting of ethanol, deionized water, N-dimethylformamide, and combinations of one or more thereof.

In some embodiments of the present invention, in the step 3), the temperature of the heat treatment is 100 to 150 ℃.

The invention also provides application of the directional water guide non-woven material in the fields of water evaporation and seawater desalination.

Compared with the prior art, the invention has the following advantages:

the invention combines the directional water guide function and the photo-thermal conversion performance, and realizes the high-efficiency matching of the moisture transmission rate and the moisture evaporation rate. Meanwhile, the multi-walled carbon nanotubes attached to the hydrophilic surface of the non-woven material endow the material with excellent absorbance, and the material can permanently float on the water surface by selecting fibers (such as PP/PE bi-component fibers) with low thermal conductivity and density lower than that of water, has low heat loss and realizes concentrated heat energy management.

Drawings

Fig. 1 is a flow chart of a process for preparing the oriented water-guiding nonwoven material with photothermal conversion function according to the invention.

FIG. 2 is a schematic diagram of the stable attachment of multi-walled carbon nanotubes of the present invention to fibers.

Fig. 3 is a schematic view of the directional water-guiding effect of the directional water-guiding nonwoven material with photothermal conversion function of the invention.

Fig. 4 is a schematic view of the oriented water-guiding nonwoven material with photothermal conversion function of the invention in simulated use.

Fig. 5 is a schematic view of the oriented water-guiding nonwoven material with photothermal conversion function of the invention in actual use.

Detailed Description

The inventor of the invention unexpectedly discovers the directional water guide non-woven material with the photo-thermal conversion function through a great deal of research, the directional water guide non-woven material with the photo-thermal conversion function comprehensively considers the four aspects of light energy absorption, moisture transmission, heat energy management and moisture evaporation in design, the optimal matching of the moisture transmission rate and the moisture evaporation rate can be realized by adjusting the proportion of the hydrophilic fibers and the hydrophobic fibers, and the photo-thermal conversion efficiency is effectively improved. The material has the characteristics of high absorbance, low heat energy loss, high-efficiency water evaporation and the like, can permanently float on the water surface, can directionally transmit water to the hydrophilic surface by the hydrophobic surface in contact with the water, and can be matched with the evaporation speed. The material can be produced in a large scale through a non-woven process, is simple to operate and low in cost, and can be applied in the fields of solar water evaporation, seawater desalination and the like in a large scale. On the basis of this, the present invention has been completed.

The invention provides an oriented water guide non-woven material with a photothermal conversion function, which sequentially comprises a hydrophobic layer, a hydrophilic layer and a carbon nano tube layer; the hydrophobic layer and the hydrophilic layer respectively comprise hydrophobic fibers and hydrophilic fibers which are mutually entangled and distributed; the hydrophobic layer comprises a hydrophobic surface and the hydrophilic layer comprises a hydrophilic surface; the hydrophobic fibers gradually decrease from the hydrophobic surface to the hydrophilic surface, and the hydrophilic fibers gradually increase from the hydrophobic surface to the hydrophilic surface; the hydrophobic fibers and the hydrophilic fibers both have a density less than the density of water.

In the oriented water guide non-woven material with the photo-thermal conversion function, the content of the hydrophilic fibers is gradually increased from the hydrophobic surface to the hydrophilic surface, the hydrophobic fibers are gradually reduced to form a wetting gradient, and a differential capillary effect is generated, so that the oriented water guide function in the thickness direction is realized, namely water can spontaneously permeate from the hydrophobic surface to the hydrophilic surface and cannot permeate from the hydrophilic surface to the hydrophobic surface.

In the oriented water guide non-woven material with the photo-thermal conversion function, the thickness of the hydrophobic layer is 1-1.5 mm. In some embodiments, the thickness of the hydrophobic layer can also be 1-1.2 mm; or 1.2 to 1.5 mm.

The thickness of the hydrophilic layer is 1-1.5 mm. In some embodiments, the thickness of the hydrophilic layer can also be 1-1.2 mm; or 1.2 to 1.5 mm.

The thickness of the carbon nanotube layer is 0.5-1 mm. In some embodiments, the thickness of the carbon nanotube layer may also be 0.5-0.8 mm; or 0.8 to 1 mm.

In the oriented water guide non-woven material with the photo-thermal conversion function, the oriented water guide non-woven material is placed in water, a hydrophobic surface in contact with the water surface can transmit the water to a hydrophilic surface, and the transmission rate can be adjusted through the proportion of the hydrophilic fibers and the hydrophobic fibers, so that the optimal matching with the water evaporation rate is achieved. In one embodiment, the mass ratio of the hydrophilic fibers to the hydrophobic fibers is 3: 1-1: 1. specifically, the mass ratio of the hydrophilic fibers to the hydrophobic fibers may also be 2: 1-1: 1; or 3: 1-2: 1, etc.

In the oriented water guide non-woven material with the photothermal conversion function, the carbon nanotube layer is a carboxylated multi-wall carbon nanotube. For example, the hydrophilic surface can be uniformly attached with carboxylated multi-wall carbon nanotubes, and the carboxylated multi-wall carbon nanotubes are modified by carboxylation and have better dispersion performance in a solution, especially in an ethanol solution. And hydrogen bonds are formed with fiber molecules in the attachment process, so that higher attachment fastness is realized. And the absorbance is higher in the wavelength range of 500-2500nm and can reach 97.6%. The wavelength range can also be 500-1500 nm; 1500-2500 nm; 500-1000 nm; 1000-1500 nm; 1500-2000 nm; or 2000 to 2500 nm.

In some embodiments, the carboxylated multi-wall carbon nanotubes may have a length of 10 to 30 microns; 10-20 microns; or 20-30 microns, etc. The diameter is 10 nm. The thermal conductivity coefficient is 2860 W.m^-1·k^-1。

In some embodiments, the mass ratio of the carboxylated multi-walled carbon nanotubes to ethanol is 1: 999.

in some embodiments, the carboxylated multi-walled carbon nanotubes comprise 3 to 8% by mass of the oriented water-conducting nonwoven material. More specifically, for example, the mass percentage of the carboxylated multi-walled carbon nanotubes in the oriented water-guiding nonwoven material may be 3 to 5%; 5-8%; 3-4%; 4-5%; 5-6%; 6-7%; or 7-8%, etc.

In the oriented water guide non-woven material with the photothermal conversion function, the density of the hydrophobic fibers and the density of the hydrophilic fibers are both less than the density of water. Typically, the hydrophobic fibers have a density of less than 1 g-mL. In some embodiments, the hydrophobic fibers can also have a density of 0.1 to 1 g-mL; 0.1-0.5 g/mL; 0.5-1 g/mL; 0.1-0.3 g/mL; 0.3-0.5 g/mL; 0.5-0.8 g/mL; or 0.8 to 1 g/mL. The hydrophobic fibers have a thermal conductivity of less than 0.3 Wm^-1·k^-1. In some embodiments, the hydrophobic fibers may also have a thermal conductivity of 0.01 to 0.3 W.m^-1·k^-1；0.01～0.038W·m^-1·k^-1；0.038W·m^-1·k^-1～0.3W·m^-1·k^-1；0.038W·m^-1·k^-1～0.1W·m^-1·k^-1；0.1W·m^-1·k^-1～0.2W·m^-1·k^-1(ii) a Or 0.2 W.m^-1·k^-1～0.3W·m^-1·k^-1And the like.

The hydrophilic fibers have a density of less than 1 g-mL. In some embodiments, the hydrophilic fiber density can also be 0.1-1 g-mL; 0.1-0.5 g/mL; 0.5 to 1gmL; 0.1-0.3 g/mL; 0.3-0.5 g/mL; 0.5-0.8 g/mL; or 0.8 to 1 g/mL. The hydrophilic fiber has a thermal conductivity of less than 0.3 W.m^-1·k^-1. In some embodiments, the hydrophilic fibers may also have a thermal conductivity of 0.01 to 0.3 W.m^-1·k^-1；0.01～0.038W·m^-1·k^-1；0.038W·m^-1·k^-1～0.3W·m^-1·k^-1；0.038W·m^-1·k^-1～0.1W·m^-1·k^-1；0.1W·m^-1·k^-1～0.2W·m^-1·k^-1(ii) a Or 0.2 W.m^-1·k^-1～0.3W·m^-1·k^-1And the like.

In one embodiment, the hydrophilic fibers are selected from hydrophilic bicomponent sheath-core structured fibers. Preferably, the hydrophilic fibers are selected from hydrophilic polypropylene/polyethylene bicomponent fibers. The hydrophobic fibers are selected from hydrophobic bicomponent sheath-core structured fibers. Preferably, the hydrophobic fibers are selected from hydrophobic polypropylene/polyethylene bicomponent fibers. Adopts hydrophilic polypropylene/polyethylene bi-component fiber and hydrophobic polypropylene/polyethylene bi-component fiber, has density lower than that of water and low heat conductivity coefficient (0.038 W.m)^-1·K^-1) The prepared non-woven material can permanently float on the water surface, the downward conduction loss of heat can be reduced when the fiber is subjected to photothermal conversion due to the low heat conductivity coefficient, an evaporation area is separated from a water area, the heat is concentrated in the evaporation area, and the efficient management of the heat is realized.

Preferably, the bicomponent fiber, such as hydrophobic polypropylene/polyethylene bicomponent fiber and hydrophilic polypropylene/polyethylene bicomponent fiber, has a core layer of polypropylene (PP) and a sheath layer of Polyethylene (PE), and the polyethylene sheath layer is melted and softened after high temperature treatment, and the carbon nanotubes on the hydrophilic fiber surface of the nonwoven material are embedded into the polyethylene sheath layer, so as to achieve the effect of "thermal welding".

In the oriented water guide non-woven material with the photo-thermal conversion function, the non-woven material is of a full-fiber structure, and is excellent in mechanical strength and high in flexibility. The multi-walled carbon nano-tubes on the surface of the hydrophilic fiber absorb light energy and convert the light energy into heat energy, the large specific surface area of the fiber provides a perfect place for water evaporation, and less water is evaporated by more concentrated heat energy. Among them, since the nonwoven material is directly from the fibers to the fabric, the fibers are entangled with each other and no yarn is formed, so that the fibers have a larger surface area and the carbon nanotubes can be attached to a larger number of places to evaporate water, and thus the specific surface area is larger than that of other textile materials such as woven fabrics and knitted fabrics. Bicomponent fibers are cylindrical and the fiber aspect ratio is large.

In the oriented water guide non-woven material with the photo-thermal conversion function, the aperture of the oriented water guide non-woven material is 40-50 micrometers. In some embodiments, the pore size of the oriented water-conducting nonwoven material can also be 40-45 microns; or 45 to 50 microns.

In another aspect, the invention provides a method for preparing the above directional water-conducting nonwoven material with photothermal conversion function, the method comprising the following steps:

3) and providing a dispersion liquid of the carbon nano tubes, spraying the dispersion liquid of the carbon nano tubes on the hydrophilic surface of the provided hydrophilic layer, and carrying out heat treatment.

In the preparation method of the oriented water guide non-woven material with the photothermal conversion function, step 1) is to prepare hydrophilic fluffy fiber nets and hydrophobic fluffy fiber nets by respectively using hydrophilic fibers and hydrophobic fibers through a net forming process. The hydrophilic fiber can be, for example, a hydrophilic bicomponent sheath-core structure fiber, and more specifically, a hydrophilic polypropylene/polyethylene bicomponent fiber. The hydrophobic fibers may be, for example, hydrophobic bicomponent sheath-core structured fibers, and more particularly hydrophobic polypropylene/polyethylene bicomponent fibers. The hydrophilic and hydrophobic fibers have a density and thermal conductivity similar to those of the oriented water-conducting nonwoven material of the first aspect of the invention. More for example, the web forming process may be a dry web forming process, for example. More for example, both the hydrophilic and hydrophobic lofty webs are uniform lofty webs. In one embodiment, the hydrophilic polypropylene/polyethylene bicomponent fibers and the hydrophobic polypropylene/polyethylene bicomponent fibers may be separately formed into a uniform lofty web by a dry-laid process.

In the step 1), the mass ratio of the hydrophilic fibers to the hydrophobic fibers is 3: 1-1: 1. specifically, the mass ratio of the hydrophilic fibers to the hydrophobic fibers may also be 2: 1-1: 1; or 3: 1-2: 1, etc. And a better directional water guide effect can be realized between the proportion ranges.

In the preparation method of the oriented water guide non-woven material with the photothermal conversion function, step 2) is to stack the hydrophilic fluffy fiber net and the hydrophobic fluffy fiber net obtained in step 1) and mechanically reinforce the stacked layers to obtain the hydrophilic layer and the hydrophobic layer. In particular, if hydrophilic polypropylene/polyethylene bicomponent fibers are used as the hydrophilic fibers, a hydrophilic PP/PE web is obtained. If hydrophobic fibers are used, hydrophobic polypropylene/polyethylene bicomponent fibers are obtained, a hydrophobic PP/PE web. The hydrophilic PP/PE web was stacked on the hydrophobic PP/PE web and mechanically consolidated. The mechanical reinforcement can be, for example, needle punching, hydroentangling, etc. In the mechanical reinforcement process, the hydrophilic fibers and the hydrophobic fibers are displaced in the longitudinal direction and the transverse direction and are mutually entangled, and gradient distribution of the hydrophilic fibers and the hydrophobic fibers is formed in the thickness direction of the material, so that gradient wettability is formed, a differential capillary effect is generated, and the function of directional water guiding is realized. The material is placed on the water surface, and liquid can be directionally transmitted from the hydrophobic surface contacted with the water to the hydrophilic surface, so that the directional transmission of the water from the hydrophobic surface to the hydrophilic surface is realized.

In the preparation method of the oriented water guide non-woven material with the photo-thermal conversion function, step 3) is to provide a dispersion liquid of carbon nano tubes, and the dispersion liquid of the carbon nano tubes is sprayed on the hydrophilic surface of the hydrophilic layer provided in step 2) for heat treatment. Specifically, the dispersion liquid of the carbon nanotubes is obtained by dispersing the carbon nanotubes in a solvent. The inherent porous structure of the non-woven material can effectively increase the light path and reach the absorbance of 97.6 percent in the wavelength range of 500-2500 nm.

The solvent is selected from one or more of ethanol, deionized water and N, N-dimethylformamide. In a specific embodiment, the multi-walled carbon nanotubes are subjected to carboxylation modification, uniformly dispersed in ethanol through an ultrasonic process to obtain a dispersion liquid of the carbon nanotubes, and the carboxylated multi-walled carbon nanotubes are uniformly attached to the hydrophilic surface of the non-woven material with the directional water guide function through a spraying method. And hydrogen bonds are formed with fiber molecules in the attachment process, so that higher attachment fastness is realized.

In the step 3), the temperature of the heat treatment can be 100-150 ℃, 100-120 ℃ or 120-150 ℃. The time of the heat treatment can be 10-20 min; 10-15 min; or 15-20 min. Before the heat treatment, a drying step is also carried out. Specifically, the material with the attached carboxylated multi-walled carbon nanotubes is dried and then is subjected to heat treatment. In one embodiment, the material with the attached carboxylated multi-walled carbon nanotubes is dried at 80 ℃ and then treated at 120 ℃ for 10min, and the high temperature treatment generates the effect of thermal welding: the polyethylene skin of the bi-component fiber is melted, the carbon nano tube on the surface of the hydrophilic fiber is embedded into the polyethylene skin, and after cooling, the carbon nano tube is higher in stable adhesion, so that the adhesion fastness of the nano material is effectively improved.

The preparation method of the invention adopts dry-method net forming and mechanical reinforcement, and the obtained non-woven material has higher mechanical strength, flexibility, air permeability and larger specific surface area, and is beneficial to water evaporation.

The dry-laid and mechanical reinforcement process used by the non-woven material of the invention has low cost and the cost of the used PP/PE bi-component fiber, and meets the application requirements in the fields of water evaporation, seawater desalination and the like.

In summary, in the oriented water-guiding nonwoven material of the present invention, the hydrophilic fibers (e.g., hydrophilic polypropylene/polyethylene bicomponent fibers) and the hydrophobic fibers (hydrophobic polypropylene/polyethylene bicomponent fibers) are subjected to dry-laying and mechanical reinforcement processes to realize a wetting gradient in the thickness direction, so as to generate a differential capillary effect, and provide the nonwoven material with an oriented water-guiding function in the thickness direction. The material is placed on water, the hydrophobic bottom surface of the material in contact with the water can pump the water to the hydrophilic surface of the material, the phenomenon of self-pumping is generated, the moisture transmission rate can be adjusted by adjusting the proportion of the hydrophilic fiber and the hydrophobic fiber, and the optimal matching with the moisture evaporation speed is achieved. And meanwhile, the hydrophilic surface layer of the material is attached with the carboxylated multi-walled carbon nanotube which can be used for light energy absorption and photo-thermal conversion.

The following examples are provided to further illustrate the advantageous effects of the present invention.

In order to make the objects, technical solutions and advantageous technical effects of the present invention more clear, the present invention is further described in detail below with reference to examples. However, it should be understood that the embodiments of the present invention are only for explaining the present invention and are not for limiting the present invention, and the embodiments of the present invention are not limited to the embodiments given in the specification. The examples were prepared under conventional conditions or conditions recommended by the material suppliers without specifying specific experimental conditions or operating conditions.

Furthermore, it is to be understood that one or more method steps mentioned in the present invention does not exclude that other method steps may also be present before or after the combined steps or that other method steps may also be inserted between these explicitly mentioned steps, unless otherwise indicated; it is also to be understood that a combined connection between one or more devices/apparatus as referred to in the present application does not exclude that further devices/apparatus may be present before or after the combined device/apparatus or that further devices/apparatus may be interposed between two devices/apparatus explicitly referred to, unless otherwise indicated. Moreover, unless otherwise indicated, the numbering of the various method steps is merely a convenient tool for identifying the various method steps, and is not intended to limit the order in which the method steps are arranged or the scope of the invention in which the invention may be practiced, and changes or modifications in the relative relationship may be made without substantially changing the technical content.

In the following examples, reagents, materials and instruments used are commercially available unless otherwise specified.

In the examples of the present invention, the hydrophobic PP/PE fibers were purchased from Jiangsu south high fiber Co. The hydrophilic PP/PE fiber is obtained by hydrophilic finishing, and the used hydrophilic agent is K-994 high-concentration chemical fiber hydrophilic ternary silicone oil of Guangdong Kefeng new material company Limited.

Carboxylated multi-walled carbon nanotubes were purchased from national institute of organic chemistry, ltd, model TNEMC 3.

Example 1

The preparation method of the oriented water guide non-woven material with the photothermal conversion function comprises the following steps:

step 1): as shown in figure 1, hydrophilic PP/PE fibers and hydrophobic PP/PE fibers with equal mass ratio are weighed and respectively fed into dry-laid equipment to output a fluffy hydrophilic fiber net and a fluffy hydrophobic fiber net;

step 2): as shown in fig. 1, after the hydrophilic fiber net is stacked above the hydrophobic fiber net, mechanical reinforcement is carried out, fibers in the fiber net are mutually entangled in the transverse direction and the longitudinal direction, from the hydrophobic surface to the hydrophilic surface, the hydrophobic fibers gradually decrease, the hydrophilic fibers gradually increase, and finally the directional water-guiding non-woven material with the wetting gradient is formed;

step 3): as shown in fig. 1, 0.1g of carboxylated multi-walled carbon nanotubes are uniformly dispersed in 99.9g of ethanol solution by an ultrasonic dispersion method to obtain a carbon nanotube dispersion solution with a concentration of 0.1%, and the carboxylated multi-walled carbon nanotubes accounting for 5.14% by mass of the oriented water-guiding nonwoven material are uniformly attached to the hydrophilic surface of the oriented water-guiding nonwoven material by using a spraying process.

Step 4): the material is placed at 80 ℃ for drying, and then is treated at 120 ℃ for 10min to melt the PE layer of the bi-component fiber, the carboxylated multi-walled carbon nanotubes on the hydrophilic surface of the fiber are embedded into the PE cortex of the fiber, and the material is stably attached to the surface of the hydrophilic fiber after cooling, as shown in figure 2.

The oriented water guide non-woven material with the photo-thermal conversion function prepared in the steps can realize oriented transmission of moisture. As shown in fig. 3, when moisture contacts the hydrophobic surface, the moisture vertically permeates to the other surface through the holes communicated with each other inside the moisture under the action of the wetting gradient of the material and the flow guiding action of the hydrophilic fiber, and meanwhile, when the liquid penetrates to the hydrophilic surface, the liquid can be rapidly diffused under the action of the hydrophilic surface, so that the permeation effect of the liquid from the hydrophobic layer to the hydrophilic layer is further accelerated. When the hydrophilic layer faces upwards, once the liquid contacts the hydrophilic surface, the liquid horizontally spreads to the whole surface under the action of the hydrophilic fibers, so that enough liquid level height cannot be accumulated to overcome the hydrostatic pressure resistance of the hydrophobic layer, and the vertical penetration from the hydrophilic layer to the hydrophobic layer cannot be realized. The directional water guide performance of the material can be tested by a liquid-state moisture manager, and the experimental steps of the experiment are as follows: the liquid water management capability of the directional water guide non-woven material is tested by adopting an M290 type liquid water management tester, a sample is cut into the size of 8cm multiplied by 8cm and placed between upper and lower concentric sensors of the tester, the hydrophobic surface is the upper surface, and the hydrophilic surface is the lower surface. A certain amount of test solution (synthetic sweat: sodium chloride solution with conductivity of 16ms ± 0.2 ms) was dropped onto the hydrophobic surface of the material within 20s, and then the test solution was transferred on the material in three directions within 100 s. Finally, an excel table is given by an experimental instrument to display the AOTC index and the OMMC index, and the oriented water guiding performance of the material is comprehensively represented by the oriented water guiding one-way transmission index (AOTC) and the liquid water dynamic transmission comprehensive index (OMMC). The performance rating tables for the two indices are as follows:

TABLE 1 AOTC and OMMC Performance rating Table

In this example, the ratio of hydrophilic fibers to hydrophobic fibers was 1/1, the AOTC of the oriented water-conducting nonwoven with photothermal conversion function was 1032.25, and the OMMC was 0.959.

Example 2

step 1): as shown in fig. 1, a certain weight of hydrophilic PP/PE fiber and hydrophobic PP/PE fiber are respectively weighed, and the mass ratio is 2: feeding the materials into dry-method web forming equipment, and outputting a fluffy hydrophilic fiber web and a fluffy hydrophobic fiber web;

step 3): as shown in fig. 1, 0.1g of carboxylated multi-walled carbon nanotubes are uniformly dispersed in 99.9g of ethanol solution by an ultrasonic dispersion method, and the carboxylated multi-walled carbon nanotubes accounting for 5.14% by mass of the oriented water-guiding nonwoven material are uniformly attached to the hydrophilic surface of the oriented water-guiding nonwoven material by a spray coating process.

In this example, the ratio of hydrophilic fibers to hydrophobic fibers was 2: 1, the oriented water-guiding non-woven material with the photothermal conversion function has the AOTC of 819.73 and the OMMC of 0.887.

Example 3

step 1): as shown in fig. 1, a certain weight of hydrophilic PP/PE fiber and hydrophobic PP/PE fiber are respectively weighed, and the mass ratio is 3: feeding the materials into dry-method web forming equipment, and outputting a fluffy hydrophilic fiber web and a fluffy hydrophobic fiber web;

In this example, the ratio of hydrophilic fibers to hydrophobic fibers was 3: 1, the AOTC of the oriented water-guiding non-woven material with the photothermal conversion function is 695.73, and the OMMC is 0.868.

Comparative example 1

step 1): as shown in fig. 1, a certain weight of hydrophilic PP/PE fiber and hydrophobic PP/PE fiber are respectively weighed, and the mass ratio is 5: feeding the materials into dry-method web forming equipment, and outputting a fluffy hydrophilic fiber web and a fluffy hydrophobic fiber web;

In this example, the ratio of hydrophilic fibers to hydrophobic fibers was 5: 1, the AOTC of the oriented water-guiding non-woven material with the photothermal conversion function is 188.82, and the OMMC is 0.467.

Example 4

Simulation experiment:

1. configuration of simulated seawater

Seawater salinity refers to the ratio of total dissolved solids in seawater to the weight of seawater, usually expressed in grams per kilogram of seawater. Salinity is used to represent the mass fraction of salt species in seawater. The average salinity of oceans in the world is 35 per thousand. Thus, we prepared a 3.5% strength simulated seawater solution of NaCl particles dissolved in deionized water.

2. Experiment for simulating solar water evaporation

The simulated solar water evaporation experiment was performed at 25 ℃ at a relative humidity of 60%. As shown in FIG. 4, a beaker having a diameter of 2.5cm and containing simulated seawater was placed on a balance with an accuracy of 0.001g, a xenon lamp with an AM1.5G filter was used to simulate solar irradiance, and the voltage was adjusted to 1 kw.m in radiant intensity using an optical power meter^-2. The sample is placed into a beaker, self-pumping is generated under the action of directional water guide, simulated seawater is pumped to the hydrophilic surface of the non-woven material and then is uniformly diffused, the whole material still stably floats on water, when simulated sunlight irradiates on the experimental sample, the quality of the water in the beaker begins to change, and specific quality values are recorded at intervals. The whole water evaporation test experiment lasts for 120min, the surface temperature and the thermogram of the material are recorded in real time by using a thermal infrared imager, and a temperature-time data curve is formed in computer software. The temperature change of the whole simulated seawater in the beaker before and after the experiment was measured by a thermometer.

3. Results of the experiment

The experimental result shows that under 1 simulated sunlight, the oriented water-guiding non-woven material with the photo-thermal conversion functionThe surface temperature can reach 48 ℃ within 200s and can be kept stable continuously in the water evaporation process, the material has the directional water guiding function, water is continuously pumped to the hydrophilic surface of the non-woven material at a certain speed, the quality change of water in the beaker gradually tends to be stable within 2h, and the non-woven materials with the photothermal conversion function in the embodiments 1-3 respectively realize 1.44kg · m · s^-2·h^-1，1.24kg·m^-2·h^-1,1.09kg·m^-2·h^-1The evaporation rate of (1) was only 0.89kg · m in the nonwoven material having photothermal conversion function in the comparative example^-2·h^-1The evaporation rate of (1), the highest evaporation rate of example 1 of the three examples, had a photothermal conversion efficiency of 87.9%, and was able to achieve 1.07kg · m in an outdoor environment^-2·h^-1The evaporation rate and the photo-thermal conversion efficiency of 62.7 percent exceed the water evaporation experimental effect of most of the prior interface type photo-thermal conversion materials. Before and after the whole water evaporation experiment, the overall temperature of the water in the beaker is 25 ℃, and no obvious change occurs, so that the low heat conductivity coefficient of the PP/PE bi-component fiber provides better heat insulation performance for the whole material, and the downward conduction of heat is hindered. Therefore, the heat obtained by the photothermal conversion is concentrated on the gas-liquid interface, and the evaporation area and the integral water area in the beaker are separated, so that the high-efficiency concentration and utilization of the heat are realized.

The evaporation rate V can be calculated by the following formula:

m₁、m₂mass of liquid at two moments (kg)

A-surface area of the test sample (m)²)

h-liquid quality recording time interval (h)

In actual tests, the invention performs a water evaporation experiment for 8 hours, obtains a plurality of evaporation rate values, and then takes an average value as final evaporation rate data.

The formula of the photothermal conversion efficiency is as follows:

eta-photothermal conversion efficiency of solar water evaporation system, i.e., steam generation efficiency (%)

m-Net Evaporation Rate for solar Water Evaporation experiment (kg. m)^-2·h^-1)

h_lvTotal enthalpy of evaporation (kJ. kg) after stabilization of the water evaporation process at a certain temperature^-1)

C_optSimulation of solar light source optical concentration

P₀Solar energy density under 1 Sun (1kw · m)^-2)

Wherein the net evaporation rate m is the difference between the average evaporation rate obtained in the water evaporation experiment and the evaporation rate in the dark environment.

In conclusion, in the oriented water guide non-woven material with the photothermal conversion function, the hydrophilic fibers and the hydrophobic fibers form gradient distribution in the thickness direction, the gradient wettability is presented, and the differential capillary effect is generated, so that the oriented water guide function is realized. The material is placed on the water surface, and moisture is directionally transmitted to the hydrophilic surface from the hydrophobic bottom surface which is in contact with water, so that the self-pumping capacity is realized. The PP/PE bi-component fiber PP is a core layer, the PE is a skin layer, the PE skin layer is melted and softened under the action of high temperature, and the multi-wall carbon nano tube is stably embedded into the fiber PE skin layer, so that high adhesion fastness is realized. As shown in fig. 5, the above materials are placed on simulated seawater, and simulated solar irradiation is given, so that the multiwall carbon nanotubes on the surface of the hydrophilic fiber of the non-woven material absorb light energy and convert the light energy into heat energy, and water directionally transmitted from the bottom is heated, and stable and efficient interface type solar water evaporation can be realized.

While the invention has been described in terms of preferred embodiments, it will be apparent to those skilled in the art that the techniques of the invention can be practiced with modification, or with appropriate modification and combination, of the techniques described herein without departing from the spirit, scope, and spirit of the invention. It is expressly intended that all such similar substitutes and modifications which would be obvious to those skilled in the art are deemed to be within the spirit, scope and content of the invention.

Claims

1. The directional water guide non-woven material is characterized by sequentially comprising a hydrophobic layer, a hydrophilic layer and a carbon nano tube layer; the hydrophobic layer and the hydrophilic layer respectively comprise hydrophobic fibers and hydrophilic fibers which are mutually entangled and distributed; the hydrophobic layer comprises a hydrophobic surface and the hydrophilic layer comprises a hydrophilic surface; the hydrophobic fibers gradually decrease from the hydrophobic surface to the hydrophilic surface, and the hydrophilic fibers gradually increase from the hydrophobic surface to the hydrophilic surface; the hydrophobic fibers and the hydrophilic fibers both have a density less than the density of water.

2. The directional water guide nonwoven material of claim 1, wherein the hydrophobic layer has a thickness of 1 to 1.5 mm; and/or the thickness of the hydrophilic layer is 1-1.5 mm; and/or the thickness of the carbon nano tube layer is 0.5-1 mm.

3. The directionally water directing nonwoven as claimed in claim 1, wherein the mass ratio of hydrophilic fibers to hydrophobic fibers is from 3: 1-1: 1.

4. the directionally water directing nonwoven material of claim 1, wherein the carbon nanotube layer is selected from carboxylated multi-walled carbon nanotubes.

5. The directionally water directing nonwoven material of claim 1, wherein the hydrophobic fibers have a density of less than 1 g-mL;

and/or the hydrophobic fibers have a thermal conductivity of less than 0.3 W.m^-1·k^-1；

And/or the density of the hydrophilic fiber is less than 1 g-mL;

and/or the thermal conductivity of the hydrophilic fiber is less than 0.3 W.m^-1·k^-1；

And/or, the hydrophilic fibers are selected from hydrophilic bicomponent sheath-core structured fibers; preferably, the hydrophilic fibers are selected from hydrophilic polypropylene/polyethylene bicomponent fibers;

and/or, the hydrophobic fibers are selected from hydrophobic bicomponent sheath-core structured fibers; preferably, the hydrophobic fibers are selected from hydrophobic polypropylene/polyethylene bicomponent fibers.

6. The directional water conducting nonwoven material as claimed in claim 1, wherein the pore size of the directional water conducting nonwoven material is 40-50 μm.

7. A method for preparing the directional water guide non-woven material as claimed in any one of claims 1 to 6, the method comprising the steps of:

8. The method for preparing the oriented water guide nonwoven material according to claim 7, wherein in the step 1), the mass ratio of the hydrophilic fibers to the hydrophobic fibers is 3: 1-1: 1;

and/or, in the step 1), the web forming process is dry web forming.

9. The method for preparing the directional water guide non-woven material as claimed in claim 7, wherein in the step 3), the dispersion liquid of the carbon nanotubes is obtained by dispersing the carbon nanotubes in a solvent through carboxylation modification; preferably, the solvent is selected from one or more of ethanol, deionized water and N, N-dimethylformamide;

and/or in the step 3), the temperature of the heat treatment is 100-150 ℃.

10. The use of the directional water-conducting nonwoven material as claimed in any one of claims 1 to 6 in the fields of water evaporation and seawater desalination.