Preparation method of three-dimensional fabric photo-thermal evaporator of gradient matrix structure

Abstract

The invention discloses a preparation method of a three-dimensional fabric photo-thermal evaporator with a gradient matrix structure, and belongs to the field of seawater desalination by using clean energy. The method comprises the following steps: 1) weaving a three-dimensional fabric with a matrix structure by adopting hydrophilic yarns as warp yarns and composite yarns prepared by compounding sacrificial yarns or fibers and hydrophilic yarns or fibers as weft yarns; 2) putting the three-dimensional fabric into a hot bath to dissolve the sacrificial yarns; and 3) dispersing the photothermal conversion material in a glutaraldehyde solution to obtain a dispersion liquid, soaking the three-dimensional fabric in the dispersion liquid, and drying to obtain the three-dimensional fabric photothermal evaporator with the gradient matrix structure. The gradient matrix three-dimensional matrix evaporator prepared by the invention can be applied to water treatment in various scenes.

Description

Technical Field

[0001] The present invention belongs to the field of seawater desalination using clean energy, and specifically relates to a preparation method of a three-dimensional fabric photothermal evaporator with a gradient matrix structure. Background Art

[0002] Solar energy, as an inexhaustible and renewable clean energy source, has attracted extensive attention from researchers in the research of seawater desalination by using solar-driven interfacial water evaporation technology to design and develop photothermal evaporators. This process does not require energy input other than solar energy and has the advantages of environmental friendliness and sustainability, showing great application prospects.

[0003] A photothermal evaporator has three key components: an absorptive evaporation layer, a thermal insulation layer, and a water supply layer. Through reasonable design and matching of each component, continuous and stable high-efficiency evaporation can be achieved. The fabric-based photothermal evaporator exhibits excellent water supply capacity by utilizing the superabsorbent capillary effect between fibers and yarns. This characteristic enables it to absorb water from bulk water and transport it to the evaporation layer in photothermal evaporation applications, and the photothermal layer quickly uses heat to drive water evaporation. The literature "Enhanced solar-driven steam generation and water purification using 3D arch solar evaporators[J]. Desalination 586(2024):117810." designed a three-dimensional arched evaporator assembled from PVA@CNTs functional fabrics, with an evaporation rate reaching 1.679 - 3.400 kg·m -2 ·h -1 , and the evaporation efficiency reaching 106.42 - 203.69%, realizing the absorption of ambient heat by the cold evaporation surface to supply evaporation. In addition, the evaporator shows poor salt tolerance during the evaporation of high-concentration brine. In order to improve the salt scale resistance performance, a filter paper layer is introduced under the fabric layer to improve the water supply capacity. Since the design and preparation of this three-dimensional evaporator involve multiple components and do not achieve an integrated design and weaving, it has certain limitations in actual large-scale production and applications, and may lead to phenomena such as deformation of the assembled structure affecting stability. Therefore, designing an integrated three-dimensional fabric-based photothermal evaporator with strong stability in the evaporation of high-concentration brine has important practical value and provides great possibilities for large-scale applications. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the present invention provides a preparation method of a three-dimensional fabric photothermal evaporator with a gradient matrix structure.

[0005] One of the technical problems to be solved by the present invention is that the evaporation rate and evaporation efficiency of the fabric evaporator in the prior art need to be further improved. Most of the photothermal evaporation layers of the existing fabric structures directly dip-coat photothermal materials on the fabric surface, and increase the light absorption by changing the fabric surface structure such as honeycomb texture. The evaporation rate and evaporation efficiency are not ideal. The evaporation layer of the present invention is an evaporator with a three-dimensional matrix structure integrally formed by using sacrificial yarns and hydrophilic yarns. The sacrificial yarns are dissolved by hydrothermal treatment to form a gradient structure, and the photothermal materials are tightly attached to the fiber surface by using gels. At the same time, the multiple absorption and reflection processes of the matrix structure for sunlight enhance the light absorption ability, improving the evaporation rate and evaporation efficiency. In addition, the three-dimensional fabric photothermal evaporator with a gradient matrix structure is directly constructed by using hydrophilic yarns and sacrificial yarns. This method is easy to operate, has low cost, and the prepared fabric evaporator has a simple structure, which is conducive to its large-scale application.

[0006] Another technical problem to be solved by the present invention is that the salt tolerance of the fabric evaporator in the prior art is poor. The current salt tolerance is divided into two types: with salt and without salt. With salt means that the salt is deposited on the side of the evaporator by evaporation and falls off automatically without affecting the normal use of the evaporator. Without salt focuses on achieving efficient salt reflux through excellent hydrophilicity to produce fresh water while maintaining the long-term stability of the evaporator, but this solution is only applicable to the evaporation of low-concentration salt. For the evaporator of the present invention, since the dissolution of the sacrificial yarns will form a porous gel structure on the yarns, improving the hydrophilicity of the fabric and expanding the water circulation of the evaporator. At the same time, due to the dissolution of the yarns, the matrix structure of the fabric becomes a gradient matrix, realizing a directional water delivery channel, which is beneficial to the diffusion and reflux of high-concentration brine, and realizing the evaporation cycle of high-concentration salt, improving the salt tolerance and long-term stability of the evaporator.

[0007] The present invention provides a preparation method (hereinafter referred to as the method) for a three-dimensional fabric photothermal evaporator with a gradient matrix structure, and the method comprises the following steps:

[0008] 1) Using hydrophilic yarns as warp yarns, and using composite yarns prepared by proportionally compounding sacrificial yarns or fibers with hydrophilic yarns or fibers as weft yarns, designing a three-dimensional fabric tissue diagram and a loom draft diagram composed of a continuous bottom flat fabric and a vertical gradient matrix fabric, and integrally weaving a three-dimensional fabric with a matrix structure through a weaving process; wherein, a gradient matrix structure is formed by sequentially increasing the proportion of sacrificial yarns in the weft yarns from top to bottom, and the increase amount each time from top to bottom is 5% - 50%, preferably 10% - 30%.

[0009] The hydrophilic yarn is one or any two or more composite yarns of natural fiber yarns, synthetic fiber yarns, and regenerated fiber yarns. The natural fiber yarns include at least one of cotton, wool, linen, and silk fiber yarns; the synthetic fiber yarns include at least one of hydrophilic modified polyester, spandex, acrylic, and nylon yarns, and their profiled cross-section fibers (including triangle, trilobal, cross-shaped, multi-angular, multi-lobed, and hollow fibers, etc.); the regenerated fiber yarns include at least one of ordinary viscose, bamboo pulp yarn, Lyocell, Tencel, Modal, regenerated protein, and regenerated chitosan fiber yarns. The hydrophilic fiber is one or any two or more composite fibers of natural fibers, synthetic fiber yarns, and regenerated fibers. The natural fibers include at least one of cotton, wool, linen, and silk fibers; the synthetic fibers include at least one of hydrophilic modified polyester, spandex, acrylic, and nylon, and their profiled cross-section fibers; the regenerated fibers include at least one of ordinary viscose, bamboo pulp yarn, Lyocell, Tencel, Modal, regenerated protein, and regenerated chitosan fibers. The fineness of the hydrophilic yarn is 5 - 42 tex, and the breaking strength is 12.6 - 270 cN·tex -1 ;

[0010] The sacrificial yarn or fiber includes at least one of water-soluble polyester yarn or fiber, water-soluble polyvinyl alcohol yarn or fiber, and water-soluble K-II yarn or fiber. The fineness of the sacrificial yarn or fiber is 10 - 50 tex.

[0011] The composite yarn method includes the composite of different yarns and yarns, the composite of different filaments and yarns, and the spinning composite of different fibers and fibers.

[0012] The yarn is at least one of staple fiber yarn, filament yarn, and staple fiber and filament composite yarn;

[0013] The matrix structure organization is at least one of satin, plain, twill, double plain, basket, mountain twill, broken twill, angle twill, and diamond twill. The bottom plane organization is a multi-layer organization, including at least one of three-dimensional through orthogonal organization, three-dimensional stratified orthogonal organization, three-dimensional through angle interlock organization, and three-dimensional stratified angle interlock organization, where the number of layers ≥ 1;

[0014] The specific process of the weaving process on the loom is warping → threading heddles → denting → adjusting the warp tension → inputting the loom parameters → weft preparation → weaving; the warping is to wind the hydrophilic yarn on a small yarn bobbin using a winder, then hang it on the creel, and draw out each warp yarn, passing through the yarn guide and the yarn positioning device; the threading heddles adopts the straight-through method, threading the yarns into the reed teeth one by one in sequence, and the number of heddle frames is 5 - 12 pages; the denting is to thread the yarns after threading heddles into the reed teeth, the reed number of the steel reed is 30 - 100, preferably 40 - 80; the number of yarns per dent is 2 - 16 pieces·dent -1, the reed count is 6 - 200; preferably 6 - 100; adjusting the warp tension means using a tension reed to adjust the warp tension. The loom tension is 15 - 25% of the warp breaking strength. The yarn tension in the matrix part is less than the tension of the bottom plane fabric. The yarns of the first and second heddles need to be taken out separately and weighted to make their tension less than that of the bottom plane. The warp yarns of the remaining heddles are tied to the let-off shaft; inputting the loom parameters means inputting the pattern diagram of the designed matrix structure; weaving is carried out by the multi-shuttle weft insertion method. The first shuttle is a hydrophilic yarn for weaving the bottom plane structure of the fabric; the second shuttle is a composite yarn prepared by compounding a sacrificial yarn / fiber and a hydrophilic yarn / fiber in a ratio of 1:0.2 - 5 (preferably 1:0.5 - 3) for weaving the matrix structure of the fabric.

[0015] The three-dimensional fabric with the gradient matrix structure is woven with hydrophilic yarns as the warp yarns and composite yarns obtained by compounding hydrophilic yarns / fibers and sacrificial yarns / fibers in a quantity ratio of 1:0.2 - 5 (preferably 1:0.5 - 3) as the weft yarns. After forming the matrix structure, the sacrificial yarns are dissolved; the height of the matrix is 2 - 50 mm, preferably 3 - 30 mm; the center distance between two matrices is 2 - 20 mm, preferably 2 - 15 mm; the total number of warp ends of the three-dimensional fabric is 12 - 3200, preferably 16 - 1600; the warp density in the direction of the matrix is 30 - 200 ends per 10 cm -1 , preferably 35 - 100 ends per cm -1 ; the weft density is 30 - 250 picks per 10 cm -1 , preferably 35 - 120 picks per cm -1 .

[0016] 2) Put the three-dimensional fabric in step 1) into a hot water bath to dissolve the sacrificial yarns and then dry it.

[0017] The dissolving method is constant temperature oscillating washing in a hot water bath. The temperature of the hot water bath is 20 - 90 °C, and the dissolving time is 0.5 - 30 min, preferably 2 - 20 min;

[0018] The drying method is freeze-drying, air-drying at room temperature or drying in a blast oven, where the temperature of the blast oven is 25 - 80 °C.

[0019] 3) Disperse the photothermal conversion material in the glutaraldehyde solution to obtain a uniform dispersion liquid. Immerse the three-dimensional fabric obtained in step 2) in it. After a certain period of time, dry it to obtain a three-dimensional fabric photothermal evaporator with a gradient matrix structure.

[0020] The described photothermal materials include at least one of carbon-based materials, metal nanomaterials, semiconductor materials, and organic polymer materials. The carbon-based materials are at least one of organic matter carbonized particles, carbon fibers, carbon quantum dots (CQDs), carbon black (CB), carbon nanotubes (CNTs), graphene (GR), or their derivatives; the metal nanomaterials are at least one of gold (Au), silver (Ag), copper (Cu), aluminum (Al), nickel (Ni), cobalt (Co), chromium (Cr), platinum (Pt), and various metal alloys; the semiconductor materials are at least one of metal oxides, metal sulfides, and other inorganic semiconductor materials. The metal oxides are tungsten oxides (WO 3 -x, where x is between 0 and 0.4), nitrogen (N) and / or phosphorus (P) doped titanium dioxide (TiOx, where x is nitrogen and / or phosphorus), narrow-bandgap Ti 2 O 3 and molybdenum oxides (MoO 3 -x, where x ranges from 0 to 0.9), Fe 2 O 3 , CeO 2 at least one of them. The metal sulfides are copper sulfides (Cu 2 -xS, where x is between 0 and 1; CuS), MoS 2 , NiS, cobalt sulfides (CoS, CoS 2 ), and nickel-cobalt sulfides (ternary nickel-cobalt sulfide) and WS 2 at least one of them. The other inorganic semiconductor materials are at least one of bismuth titanate, nitrides (such as boron nitride), carbides (such as silicon carbide), Bi 2 Ti 2 O 7 , cesium tungstate, and MXene; the organic polymer is at least one of polythiophene (PT), polypyrrole (PPy), polyaniline (PAN), and polydopamine (PDA). The concentration of the photothermal material in the dispersion is 5 - 100 mg·mL -1 , preferably 8 - 80 mg·mL -1 ;

[0021] The concentration of the glutaraldehyde solution is 1 - 10 wt%, and the preferred range is 1 - 5 wt%; the soaking duration is 1 - 120 min, and the preferred range is 4 - 100 min. The drying method is freeze-drying, air-drying at room temperature, or drying in a forced-air oven, where the temperature of the forced-air oven drying is 25 - 80 °C.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] (1) The preparation method of the present invention is simple and low-cost. Using the weaving process, a three-dimensional matrix structure fabric with excellent structural stability can be woven through simple warp and weft yarn interlacing. At the same time, by utilizing the dissolution and gelation process of sacrificial yarns, the photothermal material is fixed on the fiber surface of the fabric; the prepared gradient matrix three-dimensional matrix evaporator can be applied to water treatment in various scenarios (including saltwater treatment resistance) and can be recycled and reused.

[0024] (2) The matrix structure of the present invention enables better light absorption and thermal management design of the fabric. The light diffused reflection is enhanced between the matrices, and the light absorption rate is close to 100%. At the same time, the large light-receiving surface reduces the actual light illumination density per unit area and reduces the surface photothermal temperature under high-magnification light concentration, thereby reducing surface heat radiation and heat convection losses. In addition, the side surface of the matrix provides a large evaporation surface area, which can effectively absorb ambient heat for evaporation, and the comprehensive evaporation efficiency far exceeds 100%.

[0025] (3) The present invention provides a three-dimensional fabric with a gradient matrix structure to realize the construction of a directional water transportation channel. Based on the Marangoni effect, driven by temperature difference and salt difference, the reflux of salt solution is accelerated, which is beneficial to solving the problem that the interfacial salt scale pollution under high-concentration brine and high-magnification light concentration affects light absorption. Description of the Drawings

[0026] Figure 1 It is the radial cross-sectional view of the fabric of Examples 1-7 in the preparation method of the photothermal evaporator of the three-dimensional fabric with a gradient matrix structure of the present invention. The curves represent the warp yarn trajectories, and the circles represent the weft yarn trajectories. Among them, the black circles are cotton threads, and the green circles are composite yarns of cotton yarn and water-soluble polyvinyl alcohol; where a is the radial cross-sectional view of the fabric in Example 1, b is the radial cross-sectional view of the fabric in Examples 2, 4-7, and c is the radial cross-sectional view in Example 3;

[0027] Figure 2 It is the loom draft pattern of Examples 1-7 in the preparation method of the photothermal evaporator of the three-dimensional fabric with a gradient matrix structure of the present invention; where a is the loom draft pattern in Example 1, b is the loom draft pattern in Examples 2, 4-7, and c is the loom draft pattern in Example 3).

[0028] Figure 3 It is a picture of the integrated forming of the three-dimensional fabric with a gradient matrix structure in Example 2 of the present invention on the loom. Among them, the left picture is the front view of the integrated forming evaporator on the loom, and the right picture is the side view of the integration on the loom. Detailed Embodiments

[0029] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0030] The test methods for some performance indicators in the following embodiments are as follows:

[0031]

Evaporation rate

[0032] Under the condition of simulating 1 sun illumination, the sample is placed under a solar simulator for seawater desalination experiment. After 1 hour of illumination, record the change in the mass of water, and calculate the evaporation rate (v) according to formula (1):

[0033]

[0034] where Δm is the weight loss of water (kg), S is the evaporation area of the evaporator (m 2 ), and Δt is the evaporation time (h).

[0035]

Evaporation efficiency

[0036] The evaporation efficiency (η) of the evaporator is calculated by formula (2):

[0037]

[0038] where is the net evaporation rate, which refers to the evaporation rate after subtracting the evaporation rate under dark conditions. P in is the solar radiation power (1.0 sun = 1.0 kW·m -2 ). C op t is the optical concentration on the surface of the absorber. E equ is the evaporation enthalpy of the evaporator (2475 J·g -1 ).

[0039]

Salt concentration before and after desalination

[0040] According to the national standard of the People's Republic of China GB / T 5750.3-2023 Test Methods for Drinking Water Standards - Part 3: Quality Analysis and Quality Control, test the salt concentration before and after desalination.

[0041]

Salt scale fouling resistance

[0042] The 0.8, 3.5, and 4.1 wt% NaCl solutions were used to simulate conventional brines, and the 10 and 20 wt% NaCl solutions were used to simulate high-concentration brines. The evaporator was continuously irradiated under one sun for 12 h, and the salt crystallization on the evaporator surface was observed. Then, the light was turned off for 12 h, and the salt ablation on the evaporator surface was observed. The salt fouling resistance was evaluated by the salt crystallization on the evaporator surface before and after evaporation.

[0043] Example 1

[0044] (1) Yarn selection: Since cotton fibers (with a fineness of 21.2 tex and a breaking strength of 60 cN·tex -1 ) are easily available, low-cost, have good breaking strength, and high hydrophilicity, they were selected as the warp yarns; the water-soluble polyvinyl alcohol yarns (with a fineness of 20.0 tex) can dissolve quickly in hot water and form a three-dimensional porous gel, so they were selected as the sacrificial yarns for the weft.

[0045] Weaving a three-dimensional fabric with a gradient matrix structure: Design the cross-sectional view of the fabric in the warp direction, as shown in Figure 1 a, where the curves represent the warp yarn trajectories and the circles represent the weft yarn trajectories. The black circles are cotton threads, and the green circles are the composite yarns of cotton yarn and water-soluble polyvinyl alcohol. And draw the pattern draft of the fabric, as shown in Figure 2 a. The specific weaving process is as follows:

[0046] a. Use a winding machine to wind the 21.2-tex cotton yarns on the yarn bobbins, and then draw out each warp yarn and pass it through the yarn guide and the yarn positioning device.

[0047] b. Thread the drawn cotton yarns into the heddles of 6 harnesses in sequence; then carry out reed threading, with 6 ends per dent, and thread them into the teeth of a reed with a reed count of 40. The number of ends threaded is 16. -1 c. Hang a 1.5-kg weight on the 1st and 2nd harnesses to make the warp yarn tension 9 cN·tex

[0048] -1 -1 , and adjust the warp yarn tension of the 3rd to 6th harnesses to 12 cN·tex through the tension reed; input the designed weaving pattern draft in -1 ; Figure 2 a into the control panel of the loom.

[0049] d. Weaving a three-dimensional matrix structure fabric on an ordinary loom requires integrally weaving the bottom planar structure and the vertical matrix part. The first shuttle uses cotton yarn to weave the bottom three-dimensional two-layer angle-interlock structure; the second shuttle uses cotton yarn and polyvinyl alcohol yarn to weave the matrix structure, where the proportion of water-soluble polyvinyl alcohol yarn in the composite weft yarn increases by 20% successively from top to bottom starting from a cotton yarn to polyvinyl alcohol yarn quantity ratio of 1:1; the warp and weft yarns are interwoven to obtain a three-dimensional matrix fabric with a matrix height of 0.6 cm and a matrix center spacing of 0.4 cm. Among them, the total number of warp yarns is 96, and the warp density in the matrix direction is 43 yarns per 10 cm -1 , and the weft density is 45 yarns per 10 cm -1 .

[0050] (2) Dissolve the sacrificial yarn in the three-dimensional fabric obtained in step (1) with hot water at 80 °C for 1 minute, wash it with deionized water, and then dry it in a forced-air oven at 40 °C.

[0051] (3) Immerse the fabric in a mixed solution of MXene (8 mg·ml -1 ) and glutaraldehyde (2 wt%), soak it for 5 minutes, and then dry it at room temperature to obtain a three-dimensional fabric photothermal evaporator with a gradient matrix structure.

[0052] (4) Test the obtained three-dimensional photothermal evaporator with a gradient matrix structure. The absorbance of the evaporator is 97.5%; the evaporation rate and evaporation efficiency calculated by the formula are 2.99 kg·m -2 ·h -1 and 164.31% respectively; at the same time, test the salt ion concentrations before and after desalination, which are 250 g·L -1 and 3.55 mg·L -1 respectively; no salt crystallization precipitates during 12 hours of light evaporation at salt concentrations of 10 wt% and 20 wt%.

[0053] Example 2

[0054] (1) Yarn selection: Since cotton fiber (with a fineness of 21.2 tex and a breaking strength of 60 cN·tex -1 ) is easily available, low-cost, has good breaking strength, and high hydrophilicity, it is selected as the warp yarn; water-soluble polyvinyl alcohol yarn (with a fineness of 20.0 tex) can be quickly dissolved in hot water and will form a three-dimensional pore gel, so it is selected as the sacrificial yarn for the weft yarn.

[0055] Weaving a three-dimensional matrix structure fabric: Design the longitudinal sectional view of the fabric, as shown in Figure 1 b, where the curve represents the warp yarn trajectory and the circle represents the weft yarn trajectory, with the black circle being the cotton yarn and the green circle being the composite yarn of cotton yarn and water-soluble polyvinyl alcohol. And draw the pattern layout of the fabric, as shown in Figure 2As shown in b. The specific process of mounting on the loom is as follows:

[0056] a. Use a winding machine to wind 21.2 tex cotton yarn onto a yarn bobbin, and then draw out each warp yarn and pass it through a yarn guide frame and a yarn positioning device.

[0057] b. Thread the drawn-out cotton yarn into the heddle eyes of 6 pages of heddles in sequence; then perform reed threading, with 6 ends per dent, and thread them into the dents of a reed with a reed count of 40, and the number of ends threaded is 16. -1 Thread into the dents of a reed with a reed count of 40, and the number of ends threaded is 16.

[0058] c. Hang a 1.5 kg weight on the 1st and 2nd pages of heddles to make the warp tension 9 cN·tex, and adjust the warp tension of the 3rd - 6th pages of heddles to 12 cN·tex through a tension reed; input the designed mounting pattern drawing on the control screen of the loom. -1 and adjust the warp tension of the 3rd - 6th pages of heddles to 12 cN·tex through a tension reed; -1 ; Figure 2 Input the designed mounting pattern drawing on the control screen of the loom.

[0059] d. When weaving a three-dimensional matrix structure fabric on an ordinary loom, it is necessary to integrally weave the bottom plane structure and the vertical matrix part. The first shuttle is cotton yarn to weave the bottom three-dimensional two-layer angle interlock structure; the second shuttle is cotton yarn and polyvinyl alcohol yarn to weave the matrix structure, where the proportion of water-soluble polyvinyl alcohol yarn in the composite weft yarn starts from a ratio of 1:1 of cotton yarn to polyvinyl alcohol yarn and increases by 20% successively from top to bottom; the warp and weft yarns are interwoven to obtain a three-dimensional matrix fabric with a matrix height of 0.9 cm and a matrix center spacing of 0.4 cm. Among them, the total number of warp ends is 96, the warp density in the matrix direction is 43 ends per 10 cm, -1 and the weft density is 45 ends per 10 cm. -1 .

[0060] (2) Dissolve the sacrificial yarn of the three-dimensional fabric obtained in step (1) with hot water at 80 °C for 1 min, wash it with deionized water, and then dry it in a blast drying oven at 40 °C.

[0061] (3) Immerse the fabric in a mixed solution of MXene (8 mg·ml -1 ) and glutaraldehyde (2 wt%), soak it for 5 min, and then dry it at room temperature to obtain a three-dimensional fabric photothermal evaporator with a gradient matrix structure.

[0062] (4) Test the obtained three-dimensional photothermal evaporator with a gradient matrix structure. The absorbance of the evaporator is measured to be 98.1%; the evaporation rate and evaporation efficiency calculated through the formula are 3.37 kg·m -2 ·h -1 and 193.19% respectively; at the same time, test the salt ion concentrations before and after desalination, which are 250 mg·L -1 and 1.69 mg·L -1; No salt crystallization occurred during 12 h of light evaporation at salt concentrations of 10 wt% and 20 wt%.

[0063] Example 3

[0064] (1) Yarn selection: Since cotton fibers (with a fineness of 21.2 tex and a breaking strength of 60 cN·tex -1 ) are easily available, low-cost, have good breaking strength, and high hydrophilicity, they are selected as the warp yarns; water-soluble polyvinyl alcohol yarns (with a fineness of 21.2 tex) can dissolve quickly in hot water and form a three-dimensional pore gel, so they are selected as the sacrificial yarns for the weft yarns.

[0065] Weaving a three-dimensional matrix structure fabric: Design the warp cross-section diagram of the fabric, as shown in Figure 1 c, where the curves represent the warp yarn trajectories and the circles represent the weft yarn trajectories, with the black circles being cotton threads and the green circles being composite yarns of cotton yarn and water-soluble polyvinyl alcohol. And draw the dobby diagram of the fabric, as shown in Figure 2 c. The specific loom setup process is as follows:

[0066] a. Use a winder to wind 21.2 tex cotton yarns onto yarn bobbins, and then draw out each warp yarn and pass it through the yarn guide and yarn positioning device.

[0067] b. Thread the drawn cotton yarns into the heddle eyes of a 6-page harness in sequence; then perform reed threading, threading 6 yarns per reed -1 into the reed teeth of a reed with a reed count of 40, and the reed threading count is 16.

[0068] c. Hang a 1.5 kg weight on the 1st and 2nd pages of the harness to make the warp yarn tension 9 cN·tex -1 , and adjust the warp yarn tension of the 3rd - 6th pages of the harness to 12 cN·tex through the tension reed -1 ; Input the designed loom dobby diagram into the control screen of the loom. Figure 2 c

[0069] d. When weaving a three-dimensional matrix structure fabric on an ordinary loom, it is necessary to weave the bottom plane structure and the vertical matrix part integrally. The first shuttle weaves the bottom three-dimensional two-layer angle-interlock structure with cotton yarn; the second shuttle weaves the matrix structure with cotton yarn and polyvinyl alcohol yarn, where the proportion of water-soluble polyvinyl alcohol yarn in the composite weft yarn increases by 20% successively from top to bottom starting from a cotton yarn to polyvinyl alcohol yarn quantity ratio of 1:1; the warp and weft yarns are interwoven to obtain a three-dimensional matrix fabric with a matrix height of 1.2 cm and a matrix center spacing of 0.4 cm. The total number of warp yarns is 96, the warp density in the matrix direction is 43 yarns per 10 cm -1 , and the weft density is 45 yarns per 10 cm -1 .

[0070] (2) Dissolve the three-dimensional fabric obtained in step (1) with hot water at 80 °C for 1 min to dissolve the sacrificial yarn, wash it with deionized water, and then dry it in a blast drying oven at 40 °C.

[0071] (3) Immerse the fabric in a mixed solution of MXene (8 mg·ml -1 ) and glutaraldehyde (2 wt%), soak for 5 min, and then dry it at room temperature to obtain a three-dimensional fabric photothermal evaporator with a gradient matrix structure.

[0072] (4) Test the obtained three-dimensional photothermal evaporator with a gradient matrix structure. The absorbance of the evaporator is 97.6%; the evaporation rate and evaporation efficiency calculated by the formula are 3.21 kg·m -2 ·h -1 and 189.75% respectively; at the same time, the salt ion concentrations before and after desalination are tested to be 250 g·L -1 and 2.47 mg·L -1 respectively; no salt crystallization occurs during 12 h of light evaporation at salt concentrations of 10 wt% and 20 wt%.

[0073] Example 4

[0074] (1) Yarn selection: Since cotton fiber (with a fineness of 21.2 tex and a breaking strength of 60 cN·tex -1 ) is easy to obtain, low in cost, has good breaking strength and high hydrophilicity, it is selected as the warp yarn; the water-soluble polyvinyl alcohol yarn (with a fineness of 20.0 tex) can be quickly dissolved in hot water and will form a three-dimensional pore gel, so it is selected as the sacrificial yarn for the weft yarn.

[0075] Weave a three-dimensional matrix structure fabric: Design the warp cross-section diagram of the fabric, as shown in Figure 1 b, where the curve represents the warp yarn trajectory and the circle represents the weft yarn trajectory. The black circle is the cotton thread, and the green circle is the composite yarn of cotton yarn and water-soluble polyvinyl alcohol. And draw the pattern diagram of the fabric, as shown in Figure 2 b. The specific weaving process is as follows:

[0076] a. Use a winding machine to wind the 21.2 tex cotton yarn on the yarn bobbin, and then draw out each warp yarn and pass it through the yarn guide frame and yarn positioning device.

[0077] b. Thread the drawn cotton yarn into the heddles of 6 leaves of heddles in sequence; then carry out reed threading, with a reed insertion of 6 pieces·reed -1 inserted into the reed teeth of a reed with a reed count of 40, and the reed insertion number is 16.

[0078] c. Hang a 1.5 kg weight on the 1st and 2nd leaves of heddles to make the warp yarn tension 9 cN·tex -1, the warp tension on pages 3 - 6 is adjusted to 12 cN·tex by the tension reed. -1 ; Input the designed loom draft pattern into the control panel of the loom. Figure 2 b.

[0079] d. When weaving a three - dimensional matrix - structured fabric on an ordinary loom, it is necessary to integrally weave the bottom - layer planar structure and the vertical matrix part. The first shuttle uses cotton yarn to weave the bottom - layer three - dimensional two - layer angle - interlock organization; the second shuttle uses cotton yarn and polyvinyl alcohol yarn to weave the matrix structure, where the proportion of water - soluble polyvinyl alcohol yarn in the composite weft yarn increases by 10% successively from top to bottom starting from the ratio of cotton yarn to polyvinyl alcohol yarn of 1:0.5; the warp and weft yarns are interwoven to obtain a three - dimensional matrix fabric with a matrix height of 0.9 cm and a matrix center spacing of 0.4 cm. Among them, the total number of warp ends is 96, the warp density in the matrix direction is 43 ends·10 cm -1 , and the weft density is 45 picks·10 cm. -1 .

[0080] (2) Dissolve the sacrificial yarn of the three - dimensional fabric obtained in step (1) with hot water at 80 °C for 1 min, wash it with deionized water, and then dry it in a blast drying oven at 40 °C.

[0081] (3) Immerse the fabric in a mixed solution of MXene (8 mg·ml -1 ) and glutaraldehyde (2 wt%), soak it for 5 min, and then dry it at room temperature to obtain a three - dimensional fabric photothermal evaporator with a gradient matrix structure.

[0082] (4) Test the obtained three - dimensional photothermal evaporator with a gradient matrix structure. The absorbance of the evaporator is 97.8%; the evaporation rate and evaporation efficiency calculated by the formula are 3.13 kg·m -2 ·h -1 and 201.55% respectively; at the same time, the salt - ion concentrations before and after desalination are tested to be 2.5×10 5 mg·L -1 and 1.02 mg·L -1 respectively; no salt crystallization precipitates during 12 - h light evaporation at salt concentrations of 10 wt% and 20 wt%.

[0083] Example 5

[0084] (1) Yarn selection: Since cotton fiber (with a fineness of 21.2 tex and a breaking strength of 60 cN·tex -1 ) is easy to obtain, has a low cost, good breaking strength, and high hydrophilicity, it is selected as the warp yarn; the water - soluble polyvinyl alcohol yarn (with a fineness of 20.0 tex) can be quickly dissolved in hot water and will form a three - dimensional porous gel, so it is selected as the sacrificial yarn of the weft yarn.

[0085] Weaving a three-dimensional matrix-structured fabric: Design the warp cross-section diagram of the fabric, as shown in Figure 1 Figure b. The curves represent the warp trajectories, and the circles represent the weft trajectories. Among them, the black circles are cotton threads, and the green circles are composite yarns of cotton yarn and water-soluble polyvinyl alcohol. Then draw the draft diagram of the fabric, as shown in Figure 2 Figure b. The specific loom setup process is as follows:

[0086] a. Use a winding machine to wind 21.2 tex cotton yarn onto the yarn bobbin, and then draw out each warp yarn, passing it through the yarn guide and the yarn positioning device.

[0087] b. Thread the drawn cotton yarns into the heddles of a 6-page harness in sequence; then perform reed threading, with 6 picks per dent, threading into the teeth of a reed with a reed count of 40, and the number of picks is 16. -1 Thread into the teeth of a reed with a reed count of 40, and the number of picks is 16.

[0088] c. Hang weights of 1.5 kg on the 1st and 2nd pages of the harness to make the warp tension 9 cN·tex -1 , and adjust the warp tension of the 3rd - 6th pages of the harness to 12 cN·tex through a tension reed -1 ; Input the loom setup draft diagram designed in Figure 2 Figure b into the control panel of the loom.

[0089] d. When weaving a three-dimensional matrix-structured fabric on an ordinary loom, it is necessary to weave the bottom planar structure and the vertical matrix part integrally. The first shuttle is cotton yarn to weave the bottom three-dimensional two-layer angle-interlock structure; the second shuttle is cotton yarn and polyvinyl alcohol yarn to weave the matrix structure, where the proportion of water-soluble polyvinyl alcohol yarn in the composite weft yarn starts from a ratio of 1:2 of cotton yarn to polyvinyl alcohol yarn and increases by 30% successively from top to bottom; the warp and weft yarns are interwoven to obtain a three-dimensional matrix fabric with a matrix height of 0.9 cm and a matrix center spacing of 0.4 cm. Among them, the total number of warp ends is 96, the warp density in the matrix direction is 43 ends per 10 cm -1 , and the weft density is 45 picks per 10 cm -1 .

[0090] (2) Dissolve the sacrificial yarn of the three-dimensional fabric obtained in step (1) with hot water at 80°C for 1 minute, wash it with deionized water, and then dry it in a blast oven at 40°C.

[0091] (3) Immerse the fabric in a mixed solution of MXene (8 mg·ml -1 ) and glutaraldehyde (2 wt%), soak for 5 minutes, and then dry it at room temperature to obtain a three-dimensional fabric photothermal evaporator with a gradient matrix structure.

[0092] (4) Test the obtained three-dimensional photothermal evaporator with a gradient matrix structure. The absorbance of the evaporator is 97.2%; the evaporation rate and evaporation efficiency calculated by the formula are 3.41 kg·m -2 ·h -1 and 189.75% respectively; at the same time, test the salt ion concentrations before and after desalination, which are 250 g·L -1 and 2.47 mg·L -1 respectively; no salt crystallization occurs during 12 h of light evaporation at salt concentrations of 10 wt% and 20 wt%.

[0093] Example 6

[0094] (1) Yarn selection: Since cotton fibers (with a fineness of 21.2 tex and a breaking strength of 60 cN·tex -1 ) are easily available, low-cost, have good breaking strength, and high hydrophilicity, they are selected as the warp yarns; water-soluble polyvinyl alcohol yarns (with a fineness of 20.0 tex) can dissolve quickly in hot water and form a three-dimensional pore gel, so they are selected as the sacrificial yarns for the weft yarns.

[0095] Weave a three-dimensional matrix structure fabric: Design the warp cross-section diagram of the fabric, as shown in Figure 1 b. The curves represent the warp yarn trajectories, and the circles represent the weft yarn trajectories. Among them, the black circles are cotton threads, and the green circles are composite yarns of cotton yarn and water-soluble polyvinyl alcohol. And draw the dobby diagram of the fabric, as shown in Figure 2 b. The specific weaving process is as follows:

[0096] a. Use a winding machine to wind 21.2 tex cotton yarns on the yarn bobbins, and then draw out each warp yarn and pass it through the yarn guide and yarn positioning device.

[0097] b. Thread the drawn cotton yarns into the heddles of 6 harnesses in sequence; then carry out reed threading, with 6 ends per dent, and thread them into the teeth of a reed with a reed count of 40, and the reed threading count is 16. -1 Thread them into the teeth of a reed with a reed count of 40, and the reed threading count is 16.

[0098] c. Hang a 1.5 kg weight on the 1st and 2nd harnesses to make the warp yarn tension 9 cN·tex -1 , and adjust the warp yarn tension of the 3rd to 6th harnesses to 12 cN·tex -1 through the tension reed; input the dobby diagram designed in Figure 2 b into the control screen of the loom.

[0099] d. Weaving a three-dimensional matrix structure fabric on an ordinary loom requires one-piece weaving of the bottom planar structure and the vertical matrix part. The first shuttle is made of cotton yarn to weave the bottom three-dimensional two-layer angle-interlocked structure; the second shuttle is made of cotton yarn and polyvinyl alcohol yarn to weave the matrix structure, where the proportion of water-soluble polyvinyl alcohol yarn in the composite weft yarn increases by 30% successively from top to bottom starting from the ratio of cotton yarn to polyvinyl alcohol yarn of 1:2; the warp and weft yarns are interwoven to obtain a three-dimensional matrix fabric with a matrix height of 0.9 cm and a matrix center spacing of 0.4 cm. Among them, the total number of warp yarns is 96, and the warp density in the matrix direction is 43 yarns per 10 cm -1 , and the weft density is 45 yarns per 10 cm -1 .

[0100] (2) Dissolve the sacrificial yarn of the three-dimensional fabric obtained in step (1) with hot water at 60 °C for 1 minute, wash it with deionized water, and then dry it in a forced-air oven at 40 °C.

[0101] (3) Immerse the fabric in a mixed solution of MXene (8 mg·ml -1 ) and glutaraldehyde (2 wt%), soak it for 5 minutes, and then dry it at room temperature to obtain a three-dimensional fabric photothermal evaporator with a gradient matrix structure.

[0102] (4) Test the obtained three-dimensional photothermal evaporator with a gradient matrix structure. The absorbance of the evaporator is 97.8%; the evaporation rate and evaporation efficiency calculated by the formula are 3.11 kg·m -2 ·h -1 and 165.25% respectively; at the same time, the salt ion concentrations before and after desalination are tested to be 250 g·L -1 and 3.47 mg·L -1 respectively; no salt crystallization precipitates during 12-hour light evaporation at salt concentrations of 10 wt% and 20 wt%.

[0103] Example 7

[0104] (1) Yarn selection: Since cotton fiber (with a fineness of 21.2 tex and a strength of 60 cN·tex -1 ) is easy to obtain, has a low cost, good breaking strength, and high hydrophilicity, it is selected as the warp yarn; the water-soluble polyvinyl alcohol yarn (with a fineness of 20.0 tex) can be quickly dissolved in hot water and will form a three-dimensional pore gel, so it is selected as the sacrificial yarn for the weft yarn.

[0105] Weaving a three-dimensional matrix structure fabric: Design the cross-sectional view in the warp direction of the fabric, as shown in Figure 1 b, where the curve represents the warp yarn trajectory and the circle represents the weft yarn trajectory, among which the black circle is the cotton thread and the green circle is the composite yarn of cotton yarn and water-soluble polyvinyl alcohol. And draw the pattern drawing of the fabric, as shown in Figure 2As shown in Figure b. The specific process of setting up the loom is as follows:

[0106] a. Use a winder to wind 21.2 tex cotton yarn onto a yarn bobbin, and then draw out each warp yarn and pass it through a yarn guide and a yarn positioning device.

[0107] b. Thread the drawn cotton yarns into the heddle eyes of a 6 - page heddle in sequence; then perform denting, with 6 ends per dent, -1 Thread them into the teeth of a reed with a reed count of 40, and the number of ends dented is 16.

[0108] c. Hang a 1.5 kg weight on the 1st and 2nd pages of the heddle to make the warp tension 9 cN·tex -1 For the 3rd - 6th pages of the heddle, adjust the warp tension to 12 cN·tex through a tension reed; -1 ; Input the designed loom draft pattern on the control panel of the loom. Figure 2 b

[0109] d. When weaving a three - dimensional matrix - structured fabric on an ordinary loom, it is necessary to weave the bottom - layer planar structure and the vertical matrix part integrally. The first shuttle uses cotton yarn to weave the bottom - layer three - dimensional two - layer angle - interlock structure; the second shuttle uses cotton yarn and polyvinyl alcohol yarn to weave the matrix structure, where the proportion of water - soluble polyvinyl alcohol yarn in the composite weft yarn starts from a ratio of 1:2 of cotton yarn to polyvinyl alcohol yarn and increases by 30% successively from top to bottom; the warp and weft yarns are interwoven to obtain a three - dimensional matrix fabric with a matrix height of 0.9 cm and a matrix center spacing of 0.4 cm. Among them, the total number of warp ends is 96, the warp density in the matrix direction is 43 ends per 10 cm -1 and the weft density is 45 ends per 10 cm -1 .

[0110] (2) Dissolve the sacrificial yarn in the three - dimensional fabric obtained in step (1) with hot water at 60 °C for 3 min, wash it with deionized water, and then dry it in a forced - air oven at 40 °C.

[0111] (3) Immerse the fabric in a mixed solution of MXene (8 mg·ml -1 ) and glutaraldehyde (2 wt%), soak it for 5 min, and then dry it at room temperature to obtain a three - dimensional fabric photothermal evaporator with a gradient matrix structure.

[0112] (4) Test the obtained three - dimensional photothermal evaporator with a gradient matrix structure. The absorbance of the evaporator is 97.5%; the evaporation rate and evaporation efficiency calculated through the formula are 3.31 kg·m -2 ·h -1 and 179.54% respectively; at the same time, test the salt - ion concentrations before and after desalination, which are 250 g·L -1 and 2.33 mg·L -1; No salt crystallization was observed after 12 h of light evaporation at salt concentrations of 10 wt% and 20 wt%.

Claims

1. A method for preparing a three-dimensional fabric photothermal evaporator with a gradient matrix structure, characterized in that: The following steps are included: 1) Using hydrophilic yarn as warp yarn, using composite yarn prepared by composite of sacrificial yarn or fiber and hydrophilic yarn or fiber as weft yarn, designing a three-dimensional fabric organization diagram and machine process diagram consisting of a continuous bottom plane fabric and a vertical gradient matrix fabric, and integrating the weaving process to weave a three-dimensional fabric with a matrix structure; wherein the gradient matrix structure is formed by increasing the proportion of sacrificial yarn in the weft yarn from top to bottom; The hydrophilic yarn is one of natural fiber yarn, synthetic fiber yarn, regenerated fiber yarn, or any two or more composite yarns; the hydrophilic fiber is one of natural fiber, synthetic fiber yarn, regenerated fiber, or any two or more composite fibers; the sacrificial yarn includes at least one of water-soluble polyester yarn, water-soluble polyvinyl alcohol yarn, and water-soluble K-Ⅱ yarn; 2) placing the three-dimensional fabric in step 1) into a hot water bath to dissolve the sacrificial yarn, and drying; 3) fully dispersing the photothermal conversion material in a glutaraldehyde solution to obtain a uniform dispersion, and immersing the three-dimensional fabric obtained in step 2) in the dispersion for a period of time, and then drying to obtain a three-dimensional fabric photothermal evaporator with a gradient matrix structure; The photothermal material includes at least one of a carbon-based material, a metal nanomaterial, a semiconductor material and an organic polymer material.

2. The method for preparing a three-dimensional fabric photothermal evaporator with a gradient matrix structure according to claim 1, characterized in that: In step 1), the natural fiber yarn includes at least one of cotton, wool, linen, and silk fiber yarns; the synthetic fiber yarn includes hydrophilic modified polyester, spandex, acrylic, nylon yarn, and at least one of special-section fiber yarns; the regenerated fiber yarn includes at least one of ordinary viscose, bamboo slurry, Lyocell, Tencel, Modal, regenerated protein, and regenerated chitosan fiber yarn; the natural fiber includes at least one of cotton, wool, linen, and silk fibers; the synthetic fiber includes hydrophilic modified polyester, spandex, acrylic, nylon, and at least one of special-section fibers; the regenerated fiber includes at least one of ordinary viscose, bamboo slurry, Lyocell, Tencel, Modal, regenerated protein, and regenerated chitosan fibers.

3. The method for preparing a three-dimensional fabric photothermal evaporator with a gradient matrix structure according to claim 1, characterized in that: In step 1), the fineness of the hydrophilic yarn is 5 to 42 tex, and the breaking strength is 12.6 to 270 cN·tex -1 ; The fineness of the sacrificial yarn or fiber is 10 to 50 tex.

4. The method for preparing a three-dimensional fabric photothermal evaporator with a gradient matrix structure according to claim 1, characterized in that: The composite yarn method includes composite yarns of different yarns, composite yarns of different filaments, and composite yarns of different fibers. The yarn is at least one of spun yarn, filament yarn, and spun filament composite yarn.

5. The method for preparing a three-dimensional fabric photothermal evaporator with a gradient matrix structure according to claim 1, characterized in that: The matrix structure tissue is at least one of satin, plain, twill, double plain, square plain, mountain twill, broken twill, angle twill, and diamond twill, and the bottom plane tissue is a multi-layer tissue, including at least one of a three-dimensional through-orthogonal tissue, a three-dimensional layered orthogonal tissue, a three-dimensional through-angle interlocking tissue, and a three-dimensional layered angle interlocking tissue, wherein the number of layers is ≥1.

6. The method for preparing a three-dimensional fabric photothermal evaporator with a gradient matrix structure according to claim 1, characterized in that: The weaving method of the three-dimensional fabric of the matrix structure comprises the following steps: (1) Warping: The hydrophilic yarn is wound on the yarn cone using a winding machine, and then each warp yarn is pulled out and passed through the yarn guide frame and the yarn positioning device; (2) Drawing in: The yarns are drawn in order into the reed teeth one by one. The heald frame has 5 to 12 healds. (3) Reeding: The yarn after reeding is inserted into the reed teeth. The reed number of the steel reed is 30 to 100, and the number of reeds is 2 to 16. -1 , the number of reeds is 6 to 200; (4) Adjust the warp tension: Use the tension reed to adjust the warp tension, and the tension on the machine should be 15-25% of the warp breaking strength; (5) Input machine parameters: Input the texture pattern of the designed matrix structure; (6) Weaving: Weaving is carried out by using a multi-shuttle weft insertion method, where the first shuttle is a hydrophilic yarn that weaves the bottom fabric of the fabric; The second shuttle is a composite yarn prepared by combining sacrificial yarn / fiber and hydrophilic yarn / fiber to weave the matrix structure of the fabric.

7. The method for preparing a three-dimensional fabric photothermal evaporator with a gradient matrix structure according to claim 1, characterized in that: The three-dimensional fabric is obtained by weaving a matrix structure with hydrophilic yarn as warp yarn, hydrophilic yarn or fiber and sacrificial yarn or fiber in a ratio of 1:0.2-5 as weft yarn to obtain a composite yarn, and then dissolving the sacrificial yarn; the height of the matrix is ​​0-50 mm, and the center distance between two matrices is 2-20 mm; the total number of warp roots of the three-dimensional fabric is 12-3200, and the warp density in the direction of the matrix is ​​30-200 roots / 10 cm -1 , weft density is 30 to 250 threads per 10 cm -1 .

8. The method for preparing a three-dimensional fabric photothermal evaporator with a gradient matrix structure according to claim 1, characterized in that: The proportion of sacrificial yarn in the weft yarn increases from top to bottom to 5% to 50%.

9. The method for preparing a three-dimensional fabric photothermal evaporator with a gradient matrix structure according to claim 1, characterized in that: In step 2), the dissolution method is constant temperature shaking washing in a hot water bath, the temperature of the hot water bath is 20 to 90° C., and the dissolution time is 0.5 to 30 min; The drying method is freeze drying, air drying at room temperature or air drying, wherein the air temperature is 25-80°C.

10. The method for preparing a three-dimensional fabric photothermal evaporator with a gradient matrix structure according to claim 1, characterized in that: In step 3), the carbon-based material is at least one of organic carbonized particles, carbon fibers, carbon quantum dots, carbon black, carbon nanotubes, graphene or their derivatives; the metal nanomaterial is at least one of gold, silver, copper, aluminum, nickel, cobalt, chromium, platinum and various metal alloys; the semiconductor material is at least one of metal oxides, metal sulfides and other inorganic semiconductor materials, the metal oxide is at least one of tungsten oxide, nitrogen and / or phosphorus doped titanium dioxide, narrow band gap Ti2O3 and molybdenum oxide, Fe2O3, CeO2, the metal sulfide is at least one of copper sulfide, MoS2, NiS, cobalt sulfide, nickel cobalt sulfide and WS2, the other inorganic semiconductor material is at least one of bismuth titanate, nitride, carbide, Bi2Ti2O7, cesium tungstate and MXene; the organic polymer is at least one of polythiophene, polypyrrole, polyaniline and polydopamine; The concentration of photothermal material in the dispersion is 5-100 mg·mL -1 The concentration of glutaraldehyde is 1 to 10 wt %, and the soaking duration is 1 to 120 min; the drying method is freeze drying, room temperature drying or air drying, wherein the air drying temperature is 25 to 80 ° C.

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