Alkali lignin nanosphere / cotton fabric composite fabric as well as preparation method and application thereof

Abstract

The invention relates to the technical field of ultraviolet shielding materials, in particular to a preparation method and application of an alkali lignin nanosphere / cotton fabric composite fabric. The alkali lignin nanosphere / cotton fabric composite fabric is prepared according to the following steps: carrying out self-assembly by adopting a solvent-anti-solvent method to prepare alkali lignin nanospheres; the preparation method comprises the following steps: preparing alkali lignin nanospheres into a suspension, coating the suspension on a cotton fabric, and curing the alkali lignin nanospheres on the cotton fabric by adopting hot pressing operation to obtain the alkali lignin nanosphere / cotton fabric composite fabric. The alkali lignin is prepared into a sphere structure by utilizing the advantage of high specific surface area of spheres, the defects of low specific surface area and large volume of the alkali lignin are overcome, the alkali lignin nanospheres are combined with the fiber cotton fabric, the defects of application of the alkali lignin in anti-ultraviolet products at present are overcome, and the self-cleaning cotton fabric is obtained.

Description

Technical Field

[0001] The invention relates to the technical field of ultraviolet shielding materials, in particular to an alkali lignin nanosphere / cotton fabric composite fabric and a preparation method and application thereof. Background Art

[0002] Ultraviolet rays are a type of high-frequency electromagnetic radiation emitted by the sun. Generally speaking, ultraviolet rays from the sun can be divided into three parts: long-wave ultraviolet rays (UVA, 320-400nm), medium-wave ultraviolet rays (UVB, 280-320nm) and short-wave ultraviolet rays (UVC, 200-280nm). Exposure to strong ultraviolet rays may cause sunburn, skin damage, and even cancer. Ultraviolet rays can be absorbed by the ozone layer to prevent it from posing a threat to people's health. However, due to the random emission of freon gas, the ozone layer is damaged, the ozone layer is rapidly consumed, and an ozone hole appears. The ultraviolet rays entering the ground continue to increase, and excessive exposure to ultraviolet rays will threaten people's health. Therefore, it is particularly important to seek efficient ultraviolet shielding methods.

[0003] The commonly used UV shielding method is to use UV shielding agents, which are divided into two types: inorganic UV shielding agents and organic UV shielding agents. Inorganic UV shielding agents use nano-sized inorganic compounds to reflect, scatter or absorb ultraviolet rays to achieve the effect of shielding ultraviolet rays. Currently, commonly used inorganic UV shielding agents include zinc oxide, titanium dioxide, and cerium oxide; however, inorganic compounds have many disadvantages, including short service life, environmental pollution, and poor compatibility, which greatly limits the application of inorganic UV shielding agents. Organic UV shielding agents mainly use small molecule compounds to absorb ultraviolet rays to achieve the effect of UV shielding. Currently, commonly used organic UV shielding agents include benzophenone compounds, benzotriazole compounds, avobenzone, and methoxycinnamate. However, there are many problems in the use of organic UV shielding agents, such as poor photostability, only absorbing ultraviolet rays of a specific wavelength, and having certain toxicity, which leads to the gradual elimination of organic UV shielding agents in the use of human skin. Therefore, it is extremely urgent to develop safe, environmentally friendly and efficient UV shielding agents to replace traditional UV shielding agents and apply them to efficient UV protection of human skin.

[0004] Compared with traditional UV shielding agents, alkali lignin is derived from biomass raw materials and has great advantages in terms of environmental protection and safety. In addition, when alkali lignin is irradiated by ultraviolet light, the photons in the ultraviolet light can collide with the electrons of the aromatic ring and carbonyl group of alkali lignin, and produce n→π* transition or π→π* transition, so that the ground state alkali lignin molecules transition to the excited state. When the excited state molecules return to the ground state, the excess energy is converted into heat or light, so that the alkali lignin has the ability to absorb ultraviolet rays; therefore, alkali lignin is a potential natural ultraviolet absorber, which is expected to replace traditional ultraviolet shielding agents in the field of ultraviolet shielding daily chemical products. However, due to the irregular flaky structure of alkali lignin, it has the defects of low specific surface area and excessive volume, which makes it unable to achieve good interface compatibility with the substrate, so its application is limited. Summary of the invention

[0005] In view of the deficiencies in the above-mentioned prior art, the present invention provides an alkali lignin nanosphere / cotton fabric composite fabric and a preparation method and application thereof. The present invention utilizes the advantage of the high specific surface area of ​​the sphere to prepare the alkali lignin into a spherical structure, thereby overcoming the defects of the alkali lignin such as low specific surface area and large volume. The alkali lignin nanospheres are combined with fiber cotton fabrics to solve the defects of the current application of alkali lignin in anti-ultraviolet products, and obtains a cotton fabric with excellent ultraviolet shielding and self-cleaning.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A method for preparing an alkali lignin nanosphere / cotton fabric composite fabric comprises the following steps:

[0008] Using alkali lignin as raw material, the solvent-antisolvent method was used for self-assembly to prepare alkali lignin nanospheres.

[0009] The alkali lignin nanospheres are prepared into a suspension, and then the suspension is coated on cotton fabric, and then the alkali lignin nanospheres are solidified on the cotton fabric by hot pressing to obtain an alkali lignin nanosphere / cotton fabric composite fabric. The surface of the cotton fabric is silky, which is conducive to the attachment of the alkali lignin nanospheres. Other fabrics that can achieve the attachment of alkali lignin nanospheres can also be used as carriers in this application.

[0010] Preferably, in the alkali lignin nanosphere / cotton fabric composite fabric, the attachment amount of the alkali lignin nanosphere on the cotton fabric is 125 g / m 2 -625g / m 2 , the adhesion reaches 625g / m 2 At the same time, studies have shown that the shielding rate of alkali lignin nanospheres / cotton fabric composite fabrics for the entire ultraviolet band is as high as 99.7%, so it is meaningless to attach a large amount of alkali lignin nanospheres.

[0011] Preferably, the conditions for the hot pressing operation are: hot pressing at 160° C.-180° C. for 20 min-30 min. Under this condition, the structural stability of the cotton fabric and the alkali lignin nanospheres is ensured, and the composite of the alkali lignin nanospheres and the cotton fabric is achieved.

[0012] Preferably, the alkali lignin nanospheres are prepared according to the following steps:

[0013] dissolving alkali lignin in tetrahydrofuran by ultrasonication to obtain an alkali lignin / tetrahydrofuran mixed solution;

[0014] Add deionized water dropwise to the alkali lignin / tetrahydrofuran mixture until the mass percentage of deionized water reaches 70%-80%, then stop adding dropwise to obtain a precursor solution;

[0015] The precursor solution is dialyzed until tetrahydrofuran is no longer present in the dialyzate, and then centrifuged and dried to obtain alkali lignin nanospheres.

[0016] The invention also protects the alkali lignin nano ball / cotton fabric composite fabric prepared by the preparation method.

[0017] The invention also protects the application of the alkali lignin nanosphere / cotton fabric composite fabric in the preparation of ultraviolet shielding fabric.

[0018] Preferably, the shielding rate of the alkali lignin nanosphere / cotton fabric composite fabric against the entire ultraviolet band is as high as 99.7%.

[0019] Preferably, the ultraviolet protection factor of the alkali lignin nanosphere / cotton fabric composite fabric against medium-wave ultraviolet rays exceeds 900.

[0020] The present invention also protects the use of the above-mentioned alkali lignin nanosphere / cotton fabric composite fabric in the preparation of self-cleaning fabric.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The present invention uses alkali lignin as a raw material, uses tetrahydrofuran to dissolve the alkali lignin, and then uses deionized water as an anti-solvent to uniformly drip into an alkali lignin / tetrahydrofuran mixture to precipitate the alkali lignin. During the precipitation of small molecular alkali lignin, a self-assembly reaction occurs and alkali lignin nanospheres are generated. The present invention adopts a solvent-anti-solvent method based on the layer-by-layer self-assembly of alkali lignin molecules to prepare alkali lignin nanospheres with good dispersibility, compatibility and stability, thereby improving the problems of alkali lignin in application, such as excessive volume, low specific surface area and easy occurrence of serious agglomeration.

[0023] 2. The alkali lignin nanospheres of the present invention are obtained by self-assembly, and are formed into spheres only by physical action, without changing the chemical composition and functional groups of the alkali lignin, and maintaining the original ultraviolet absorption capacity of the alkali lignin.

[0024] 3. The present invention also loads alkali lignin nanospheres onto cotton fabric to prepare an anti-ultraviolet alkali lignin nanosphere / cotton fabric composite fabric. It has excellent ultraviolet shielding performance. After loading 5wt% alkali lignin nanospheres, the shielding rate of full-band ultraviolet rays is as high as 99.7%, and the ultraviolet protection factor of medium-wave ultraviolet rays exceeds 900.

[0025] 4. The air permeability and self-cleaning ability of the alkali lignin nanoball / cotton fabric composite fabric of the present invention are also very good. The self-cleaning ability enables the alkali lignin nanoball / cotton fabric composite fabric to meet the use of daily harsh environments, and in the durability performance test, the ultraviolet shielding effect and self-cleaning ability of the alkali lignin nanoball / cotton fabric composite fabric can be well maintained, showing very good reliability; the air permeability is convenient for daily wear and can directly contact the skin. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 In the figure, (a) is the SEM image of alkali lignin; (b) is the particle size distribution diagram of alkali lignin; (c) is the SEM image of the alkali lignin nanospheres of Example 1; (d) is the particle size distribution diagram of the alkali lignin nanospheres of Example 1; (e) and (f) are TEM images of the alkali lignin nanospheres of Example 1, respectively; (g) is the carbon element distribution diagram of the alkali lignin nanospheres of Example 1; (h) is the oxygen element distribution diagram of the alkali lignin nanospheres of Example 1; (i) is the stability diagram of alkali lignin; (j) is the stability diagram of the alkali lignin nanospheres of Example 1; (k) is the UV-visible absorption spectrum diagram of alkali lignin and the alkali lignin nanospheres of Example 1; (l) is the infrared absorption spectrum diagram of alkali lignin and the alkali lignin nanospheres of Example 1.

[0027] Figure 2In the figure, (a) is an appearance image of cotton fabric and LNPs / cotton fabric composite fabrics of Examples 1-3; (b) is an SEM image of cotton fabric; (c) is an SEM image of the LNPs / cotton fabric composite fabric of Example 1; (d) is an SEM image of the LNPs / cotton fabric composite fabric of Example 2; (e) and (f) are SEM images of the LNPs / cotton fabric composite fabric of Example 3; (g) is a carbon element and oxygen element distribution map of the LNPs / cotton fabric composite fabric of Example 3; (h) is a carbon element distribution map of the LNPs / cotton fabric composite fabric of Example 3; (i) is an oxygen element distribution map of the LNPs / cotton fabric composite fabric of Example 3.

[0028] Figure 3 In the figure, (a) is an infrared absorption spectrum of cotton fabric and LNPs / cotton fabric composite fabric of Example 1-3; (b) is an ultraviolet-visible transmittance graph of cotton fabric and LNPs / cotton fabric composite fabric of Example 1-3; (c) is an ultraviolet protection factor graph of cotton fabric and LNPs / cotton fabric composite fabric of Example 1-3; (d) is a bar graph of air permeability test of cotton fabric and LNPs / cotton fabric composite fabric of Example 1-3; (e) is a bar graph of hydrophobicity test of cotton fabric and LNPs / cotton fabric composite fabric of Example 1-3; (f) is a self-cleaning performance test graph of LNPs / cotton fabric composite fabric of Example 3.

[0029] Figure 4 In the figure, (a)-(f) are graphs showing the change in ultraviolet shielding performance of the LNPs / cotton fabric composite fabric of Example 3 under different conditions, and the corresponding conditions are: (a) temperature of -20°C, (b) temperature of -5°C, (c) temperature of 50°C, (d) temperature of 150°C, (e) water immersion, and (f) wear; (g) wear test graph, (h) and (i) are SEM graphs after 200 wears; (j) is a carbon and oxygen element distribution graph after 200 wears; (k) is a carbon element distribution graph after 200 wears; (j) is an oxygen element distribution graph after 200 wears. DETAILED DESCRIPTION

[0030] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings, but it should be understood that the protection scope of the present invention is not limited by the specific implementation. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0031] The present invention dissolves alkali lignin in a specific organic solvent, and through a solvent-antisolvent self-assembly method and a dialysis method, the alkali lignin can be self-assembled to form a stable polymer-alkali lignin nanosphere, and the alkali lignin nanosphere is a micro-nano material. The size of the alkali lignin nanosphere is significantly smaller than that of the alkali lignin particles, and has the advantages of good dispersibility in water and stable suspension, and the stability and dispersibility are improved, and the inherent defects of the alkali lignin are well overcome, and the chemical performance characteristics of the alkali lignin are not changed, so that the application of the alkali lignin in the anti-ultraviolet products becomes possible.

[0032] The present invention also uses a droplet coating method to load alkali lignin nanospheres (LNPs) onto cotton fabric, and solidifies it by hot pressing. The LNPs / cotton fabric composite fabric loaded with 5wt% LNPs has a full-band ultraviolet light shielding rate of 99.7%, and a UV protection factor of up to 900 for medium-wave ultraviolet rays. At the same time, the LNPs / cotton fabric composite fabric also has good air permeability and self-cleaning ability. In addition, by conducting high temperature, low temperature, water immersion, and wear tests on the LNPs / cotton fabric composite fabric, it is proved that it has excellent durability.

[0033] Alkali lignin is an amorphous polymer composed of phenylpropane structural units. It is the second most abundant chemical component in plants after cellulose and is the largest aromatic renewable resource in nature. In industry, alkali lignin mainly comes from black liquor in pulp and paper production and is the main by-product of the paper industry. Therefore, it is of great value and far-reaching significance to use industrial alkali lignin as raw material and obtain high-value-added biomass materials through deep processing to replace fossil resources.

[0034] The technical solution of the present invention is further explained by using embodiments and comparative examples, as shown below:

[0035] Example 1

[0036] A method for preparing an alkali lignin nanosphere / cotton fabric composite fabric comprises the following steps:

[0037] S1. Preparation of alkali lignin nanoparticles (LNPs):

[0038] The alkali lignin nanospheres were prepared by self-assembly using a solvent-antisolvent method; 30 mg of alkali lignin was dissolved in 10 mL of tetrahydrofuran under ultrasound to obtain an alkali lignin / tetrahydrofuran mixed solution; deionized water was added to the alkali lignin / tetrahydrofuran mixed solution at a rate of 72 mL / h using a syringe pump at 500 rpm, and the addition was stopped when the mass percentage of deionized water accounted for 80% of the entire reaction system to obtain a precursor solution; the precursor solution was transferred to a dialysis bag and immersed in excess dialysis water, and the dialysis water was replaced every 12 hours until there was no tetrahydrofuran in the dialysis solution. After the dialysis was completed, the alkali lignin nanosphere powder was obtained by centrifugation and freeze-drying;

[0039] S2. Preparation of alkali lignin nanosphere / cotton fabric composite fabric (LNPs / cotton fabric composite fabric):

[0040] Alkali lignin nanospheres / cotton fabric composite fabrics were prepared by a simple droplet coating method; the cotton fabric was washed three times with anhydrous ethanol and deionized water, dried and set aside; the alkali lignin nanospheres were prepared into a 1wt% suspension, and the suspension was dripped onto the surface of the cotton fabric, 3 drops each time, and dried at 105°C. This process was repeated until 5mL of the suspension was dripped onto the cotton fabric, and the adhesion amount of the alkali lignin nanospheres on the cotton fabric was 125g / m 2 Finally, the mixture was placed in a flat vulcanizer and hot-pressed at 180°C for 20 minutes to solidify the alkali lignin nanospheres to obtain an alkali lignin nanosphere / cotton fabric composite fabric.

[0041] Example 2

[0042] A method for preparing an alkali lignin nanosphere / cotton fabric composite fabric, the preparation steps are the same as those in Example 1, the only difference is that the mass percentage of the suspension in step S2 is replaced by 1wt% to 3wt%, and the attachment amount of the alkali lignin nanospheres on the cotton fabric is 375g / m 2 .

[0043] Example 3

[0044] A method for preparing an alkali lignin nanosphere / cotton fabric composite fabric, which has the same preparation steps as Example 1, except that the mass percentage of the suspension in step S2 is replaced by 5wt% from 1wt%, and the attachment amount of the alkali lignin nanospheres on the cotton fabric is 625g / m 2 .

[0045] Example 4

[0046] A method for preparing an alkali lignin nanosphere / cotton fabric composite fabric comprises the following steps:

[0047] S1. Preparation of alkali lignin nanoparticles (LNPs):

[0048] The alkali lignin nanospheres were prepared by self-assembly using a solvent-antisolvent method; 30 mg of alkali lignin was dissolved in 10 mL of tetrahydrofuran under ultrasound to obtain an alkali lignin / tetrahydrofuran mixed solution; deionized water was added to the alkali lignin / tetrahydrofuran mixed solution at a rate of 72 mL / h using a syringe pump at 500 rpm, and the addition was stopped when the mass percentage of deionized water accounted for 70% of the entire reaction system to obtain a precursor solution; the precursor solution was transferred to a dialysis bag and immersed in excess dialysis water, and the dialysis water was replaced every 12 hours until there was no tetrahydrofuran in the dialysis solution. After the dialysis was completed, the alkali lignin nanosphere powder was obtained by centrifugation and freeze-drying;

[0049] S2. Preparation of alkali lignin nanosphere / cotton fabric composite fabric (LNPs / cotton fabric composite fabric):

[0050] Alkali lignin nanospheres / cotton fabric composite fabric was prepared by a simple droplet coating method; the cotton fabric was washed three times with anhydrous ethanol and deionized water, dried and set aside; the alkali lignin nanospheres were prepared into a 5wt% suspension, and the suspension was dripped onto the surface of the cotton fabric, 4 drops were added each time, and dried at 100°C. This process was repeated until 5mL of the suspension was dripped onto the cotton fabric, and the adhesion amount of the alkali lignin nanospheres on the cotton fabric was 625g / m 2 Finally, the mixture was placed in a flat vulcanizer and hot-pressed at 160°C for 30 minutes to solidify the alkali lignin nanospheres to obtain an alkali lignin nanosphere / cotton fabric composite fabric.

[0051] Examples 1-4 of the present invention all prepared alkali lignin nanosphere / cotton fabric composite fabrics with excellent ultraviolet shielding effect and self-cleaning ability. The alkali lignin nanosphere / cotton fabric composite fabric prepared in Example 1-3 is used as an example for research. The specific research method and results are as follows:

[0052] 1. Testing and Characterization:

[0053] (1) Fourier transform infrared spectroscopy (FTIR): The sample was mixed with potassium bromide and pressed into a pellet, and then FT-IR was performed. -1 Scanning within the wavenumber range with a resolution of 2cm -1 .

[0054] (2) X-ray diffraction analysis (XRD): The XRD pattern of the sample is tested using an X-ray diffractometer.

[0055] (3) Ultraviolet-visible absorption spectroscopy analysis (UV-vis): The UV-vis absorption spectrum of the LNPs / cotton fabric composite fabric was detected using an ultraviolet-visible spectrophotometer.

[0056] (4) Water contact angle analysis (CA): The CA of LNPs / cotton fabric composites was measured at room temperature using a contact angle meter. The dynamic contact angle method was used to measure the CA of cotton fabrics, and a 4 μL water droplet was used to measure the CA of all samples.

[0057] (6) Wear resistance test: The wear resistance of the LNPs / cotton fabric composite fabric was tested by dragging the LNPs / cotton fabric composite fabric with a 100 g weight placed on sandpaper back and forth.

[0058] 2. Results and Discussion

[0059] 1. Study on the morphology, size and structure of alkali lignin nanospheres:

[0060] In order to study the morphological characteristics of LNPs, SEM was used to characterize them. Figure 1 As shown. Figure 1 As can be seen from (a) and 1(b), the alkali lignin (AL) raw material is a spherical structure with a diameter between 20 μm and 100 μm, which is widely distributed, and there is a serious agglomeration phenomenon between the AL blocks. In addition, the AL suspension has an obvious layered structure, which is mainly due to the large size of the AL raw material and poor dispersion. Figure 1 As shown in Figures 1(c) and 1(d), LNPs are spherical with highly consistent morphology, and their diameters are distributed between 80nm and 800nm, which is a narrow distribution. Compared with AL raw materials, LNPs show good dispersibility and no obvious agglomeration phenomenon. They still show good dispersibility after standing for a long time.

[0061] In addition, the hollow structure of LNPs was observed from the TEM images, e.g. Figure 1 As shown in (e) and 1(f), compared with the prior art alkali lignin nanomaterials, the spheres prepared by the present invention have a smaller diameter and a more obvious hollow structure. The hollow structure may be formed because the organic solvent inside the sphere evaporates faster during the freeze-drying process, breaking through the shell structure of the sphere and causing the sphere to break. In addition, Figure 1 As shown in Figures 1(g) and 1(h), EDS was further used to evaluate the uniformity of the target elements on the surface of LNPs. It was found that carbon and oxygen elements showed good dispersion and compatibility on the surface of LNPs, indicating that AL formed a uniform and stable spherical shell structure during self-assembly.

[0062] The long-term stability of AL raw materials and LNPs was characterized by tracking the changes in particle size of AL raw materials and LNPs over time. Figure 1 (i) and 1(j) show the time-dependent changes in the average particle size of AL raw materials and LNPs. It can be seen that the stability of the AL suspension is very poor, and its average particle size gradually increases in violent ups and downs; in contrast, LNPs show excellent stability. After standing for 25 days, the average particle size of the suspension has not changed significantly, and the average particle size has remained at around 341nm. The long-term stability of LNPs in deionized water is mainly attributed to the repulsive effect of the double electron layer formed on the surface of LNPs.

[0063] Figure 1 (k) shows the UV-visible absorption characteristics of AL raw material and LNPs in aqueous solution. Compared with AL suspension, LNPs suspension has lower absorbance in the visible light region and higher absorbance in the UV region, which indicates that LNPs suspension can effectively absorb UV light while maintaining a high visible light transmittance, and has potential application prospects in the field of UV protection products. In addition, AL raw material has a strong absorption peak at 285nm, which may be attributed to the π-π transition of the guaiacyl structural unit. Compared with the absorption peak of AL raw material, the absorption peak of LNPs at around 280nm is blue-shifted by 5nm. According to previous studies, lignin is easy to agglomerate to form aggregates, and the formation of lignin aggregation will cause slight changes in the UV absorption spectrum.

[0064] To investigate the chemical characteristics of LNPs, FT-IR spectra of AL raw materials and LNPs were as shown in Figure 1 (l) As shown. In the infrared of LNPs, at 3370cm -1 、2930cm -1 、1695cm -1 、1595cm -1 、1508cm -1 、1421cm -1 、1328cm -1 、1212cm -1 、833cm -1 The absorption peaks can be clearly observed, which are attributed to OH stretching vibration, -CH2- stretching vibration, -C=O vibration conjugated with aromatic nucleus, aromatic nucleus vibration, clove nucleus vibration, -CO- stretching vibration, and -CH- vibration in aromatic nucleus. Compared with the infrared spectrum of AL raw material, there is no obvious change in the absorption peak, indicating that the functional group has not changed during the self-assembly of AL into spheres. In summary, the FT-IR absorption spectra of AL raw material and LNPs are highly similar, and the chemical properties of AL have not changed during the self-assembly of AL into spheres.

[0065] 2. Characterization of LNPs / cotton fabric composite fabric morphology:

[0066] In order to study the morphology of cotton fabric and LNPs / cotton fabric composite fabric, SEM was used to characterize them. The results are shown in Figure 2 As shown. Figure 2 As can be seen in (a), with the loading of LNPs, the color of the cotton fabric changes from white to brown, and the color gradually deepens with the increase of LNPs loading. Figure 2 (b)-2(e) It can be seen that the surface of the cotton fabric is smooth, bare and flat, without any material attached. At the same time, the surface fibrillation can be clearly observed, which provides favorable conditions for the loading of LNPs. After loading LNPs, it can be clearly seen that the LNPs are evenly distributed on the surface of the cotton fabric. In addition, with the increase in the amount of LNPs added, it can be clearly observed that the loading amount of LNPs on the cotton fabric surface increases, which is consistent with the results shown in the above intuitive figure. SEM element mapping is further used to characterize the distribution of target elements (including carbon and oxygen elements) in LNPs / cotton fabric composite fabrics, such as Figure 2 As shown in (f)-2(i), carbon and oxygen elements show excellent compatibility and dispersion uniformity in the LNPs / cotton fabric composite fabric, further proving that the loading of LNPs on cotton fabric is relatively uniform and stable.

[0067] 3. Chemical structure and performance characterization of LNPs / cotton fabric composite fabrics:

[0068] FT-IR spectra were used to compare the chemical structure changes of cotton fabrics before and after loading LNPs. Figure 3 As shown in (a), in the infrared spectrum of cotton fabric, it can be seen that at 1029cm -1 and 1160cm -1 There are two characteristic infrared absorption peaks near the wave number, which are respectively attributed to the CO stretching vibration or the cyclic COC asymmetric stretching vibration in cellulose; however, in the infrared spectrum of LNPs / cottonfabric composite fabric, in addition to the CO stretching vibration peak and COC asymmetric stretching vibration peak attributed to cellulose, there is also a peak at 1596cm -1 A new absorption diffraction peak appeared nearby, which was attributed to the characteristic absorption peak of the aromatic ring in AL, further indicating that LNPs were successfully loaded on cotton fabric without destroying the aromatic ring skeleton structure of AL. In addition, compared with the infrared spectrum of cotton fabric, the LNPs / cotton fabric composite fabric had a strong absorption peak at 3331cm -1The nearby absorption peak attributed to -OH was blue-shifted, which proved that the hydroxyl groups in the cellulose molecules of cotton fabric combined with the hydroxyl groups in LNPs to form hydrogen bonds.

[0069] The UV transmittance of fabric is an important part of the fabric's UV protection performance. In order to evaluate the UV protection ability of LNPs / cotton fabric composite fabrics, the transmittance of LNPs / cotton fabric composite fabrics in the visible light region and the ultraviolet light region was tested. The results are as follows: Figure 3 (b) As shown. Cotton fabric has a high transmittance in the ultraviolet band, but a weak shielding effect on ultraviolet rays. This is mainly because cotton fabric can only reflect and absorb a small part of ultraviolet rays through its own porous structure. In contrast, LNPs / cotton fabric composite fabric has a lower transmittance in the ultraviolet region and can effectively shield long-wave ultraviolet rays and medium-wave ultraviolet rays, but its shielding effect on short-wave ultraviolet rays is slightly worse than that of long-wave ultraviolet rays and medium-wave ultraviolet rays. In real life, short-wave ultraviolet rays cannot penetrate the ozone layer and will not pose a threat to human health.

[0070] Ultraviolet protection factor (UPF) is an important indicator to measure the anti-ultraviolet performance of textiles in practical applications. The UPF results of cotton fabrics and LNPs / cotton fabric composite fabrics are shown in Figure 3 (c) As shown. The UPF value of cotton fabric is greater than 100, which has certain UV shielding performance. With the addition of LNPs, the UPF value of LNPs / cotton fabric composite fabric increases compared with cotton fabric. When the LNPs loading is 5%, the UPF value of LNPs / cotton fabric composite fabric under ultraviolet light of about 300nm even exceeds 900, which far exceeds the requirements of GB / T18830-2009 national standard for UV protection fabrics (UPF>40), indicating that LNPs / cotton fabric composite fabric has excellent UV protection performance and is expected to replace traditional UV protection fabrics for UV protection in human daily life.

[0071] UV protective fabrics are mainly used for contact with human skin, and the requirement for their air permeability is extremely important. For this reason, the present invention characterizes the air permeability data of LNPs / cotton fabric composite fabrics to evaluate the wearing comfort of LNPs / cotton fabric composite fabrics. Figure 3 As shown in (d), the air permeability of cotton fabric is 489.437 cm 3 / m 2.d.Pa, and with the addition of LNPs, the air permeability of LNPs / cotton fabric composite fabrics decreased. The air permeabilities of LNPs / cotton fabric composite fabrics with 1%, 3%, and 5% LNPs added were 372.252cm 3 / m 2 .d.Pa, 293.154cm 3 / m 2 .d.Pa and 258.756cm 3 / m 2 .d.Pa, which may be due to the fact that LNPs covered the gaps between the cotton threads. In summary, the LNPs / cotton fabric composite fabric not only exhibits excellent UV protection performance, but also ensures the wearing comfort of the user.

[0072] LNPs are mainly composed of phenylpropane structures and have certain hydrophobic properties. Loading LNPs on cotton fabrics gives cotton fabrics good self-cleaning properties. In order to characterize the self-cleaning ability of LNPs / cotton fabric composite fabrics, the surface hydrophobicity of LNPs / cotton fabric composite fabrics was tested using a static contact angle meter. The results are shown in Figure 3 (e) As shown. The contact angle of cotton fabric is only 49.7°, showing extremely poor self-cleaning ability, which is attributed to the fact that the chemical composition of cotton fabric is mainly cellulose, which has abundant hydroxyl groups and is a typical hydrophilic group. In contrast, the addition of LNPs significantly increased the contact angle of cotton fabric, and with the increase of LNPs loading, the contact angle of LNPs / cotton fabric composite fabric gradually increased. When the LNPs loading is 5%, the contact angle of LNPs / cotton fabric composite fabric is 144°, which is very close to the performance requirements of superhydrophobic materials (≥150°). In addition, as Figure 3 As shown in (f), in common use environments, such as drinking tea, milk, juice, and coffee, it can also show good self-cleaning ability and UV protection performance. In summary, the LNPs / cottonfabric composite fabric exhibits excellent self-cleaning performance and can meet the needs of daily harsh environments.

[0073] 4. Characterization of application stability of LNPs / cotton fabric composite fabrics:

[0074] Since LNPs / cotton fabric composite fabrics are expected to be used as sun-protective clothing fabrics needed in daily life, in addition to having good UV protection performance, basic UV protection performance requirements must be met in extreme environments such as high temperature, low temperature, rain soaking and wear. In order to evaluate the above required results, the UPF value of LNPs / cotton fabric composite fabrics under 350nm UV light was recorded. The results are as follows: Figure 4 shown.

[0075] The present invention studies the changes in the ultraviolet shielding properties of LNPs / cotton fabric composite fabrics at -20°C, 5°C, 50°C, and 150°C. Figure 4 As shown in (a)-4(d), after the LNPs / cotton fabric composite fabric was placed in high temperature (50℃ and 150℃) and low temperature (-20℃ and 5℃) environments for 96 hours, the results showed that the UPF value of the LNPs / cotton fabric composite fabric did not change and remained at around 188, indicating that the LNPs / cotton fabric composite fabric has stable UV protection and self-cleaning capabilities in extreme temperature environments. In addition, the LNPs / cotton fabric composite fabric was also simulated to be immersed in rainwater for a long time, such as Figure 4 As shown in (e), the results show that after 120 hours of static immersion, the UPF of the LNPs / cotton fabric composite fabric showed a slight decrease from 200 to 192, but the LNPs / cotton fabric composite fabric still maintained good self-cleaning ability.

[0076] The present invention studies the wear performance of LNPs / cotton fabric composite fabric as UV protection clothing required in daily life. The results are as follows Figure 4 (f) As shown. It can be observed that after 200 times of wear, obvious wear marks appeared on the surface of the LNPs / cotton fabric composite fabric. However, it was found through measurement that the LNPs / cotton fabric composite fabric can still maintain a good UV shielding effect (at 350nm, the transmittance is 0.55%) and a good UPF value (at 350nm, the value is 181.8). However, the hydrophobicity of the LNPs / cotton fabric composite fabric is reduced, mainly due to the slight shedding of LNPs on the surface of the cotton fabric. This phenomenon can also be observed by SEM, such as Figure 4As shown in (h)-4(i), it can be found that due to the concentration of weight stress, LNPs fell off in the central area of ​​the LNPs / cotton fabric composite fabric where the weight was placed, causing the UV protection performance and self-cleaning ability of this area to slightly decrease. Figure 4 As shown in (j)-4(l), it can be seen from the element mapping of SEM that after 200 wear tests, the dispersion and uniformity of carbon and oxygen elements on the surface of the LNPs / cotton fabric composite fabric were not affected.

[0077] 3. Conclusion:

[0078] The research content of the present invention is mainly divided into two parts. First, alkali lignin is used as raw material and dissolved in tetrahydrofuran. Then, deionized water is used as an anti-solvent and evenly dripped into the alkali lignin / tetrahydrofuran mixture to precipitate the alkali lignin and generate alkali lignin nanospheres by self-assembly reaction.

[0079] Secondly, the present invention uses a droplet coating method to load the alkali lignin nanospheres onto the cotton fabric and solidifies it by hot pressing. Studies have shown that the loading capacity of alkali lignin nanospheres is 625g / m 2 The alkali lignin nanosphere / cotton fabric composite fabric has a shielding rate of 99.7% for full-band ultraviolet light and a protection factor of up to 900 for medium-wave ultraviolet light. At the same time, the LNPs / cotton fabric composite fabric has good air permeability and self-cleaning ability. In addition, the LNPs / cotton fabric composite fabric has been tested at high temperature, low temperature, water immersion, and wear, proving that it has excellent durability.

[0080] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations. The above-mentioned embodiments are only preferred embodiments for fully illustrating the present invention, and the protection scope thereof is not limited thereto.

Claims

1. A method for preparing an alkali lignin nanosphere / cotton fabric composite fabric, characterized in that: The following steps are involved: Using alkali lignin as raw material, the solvent-antisolvent method was used for self-assembly to prepare alkali lignin nanospheres. The alkali lignin nanospheres are prepared into a suspension, and then the suspension is coated on cotton fabric, and then the alkali lignin nanospheres are solidified on the cotton fabric by hot pressing to obtain an alkali lignin nanosphere / cotton fabric composite fabric.

2. The method for preparing an alkali lignin nanosphere / cotton fabric composite fabric according to claim 1, characterized in that: In the alkali lignin nanosphere / cotton fabric composite fabric, the attachment amount of alkali lignin nanosphere on the cotton fabric is 125g / m 2 -625g / m 2 .

3. The method for preparing an alkali lignin nanosphere / cotton fabric composite fabric according to claim 1, characterized in that: The conditions of the hot pressing operation are: hot pressing at 160°C-180°C for 20min-30min.

4. The method for preparing an alkali lignin nanosphere / cotton fabric composite fabric according to claim 1, characterized in that: Alkali lignin nanospheres were prepared according to the following steps: dissolving alkali lignin in tetrahydrofuran by ultrasonication to obtain an alkali lignin / tetrahydrofuran mixed solution; Add deionized water dropwise to the alkali lignin / tetrahydrofuran mixture until the mass percentage of deionized water reaches 70%-80%, then stop adding dropwise to obtain a precursor solution; The precursor solution is dialyzed until tetrahydrofuran is no longer present in the dialyzate, and then centrifuged and dried to obtain alkali lignin nanospheres.

5. An alkali lignin nanosphere / cotton fabric composite fabric prepared by the preparation method according to any one of claims 1 to 4.

6. Use of the alkali lignin nanosphere / cotton fabric composite fabric according to claim 5 in preparing ultraviolet shielding fabric.

7. The use according to claim 6, characterized in that: The shielding rate of the alkali lignin nanosphere / cotton fabric composite fabric against the entire ultraviolet band reaches 99.7%.

8. The use according to claim 6, characterized in that: The UV protection factor of the alkali lignin nanosphere / cotton fabric composite fabric against medium-wave ultraviolet rays is over 900.

9. Use of the alkali lignin nanosphere / cotton fabric composite fabric according to claim 5 in preparing self-cleaning fabric.

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