Process for the preparation of photochromic fibers

Abstract

The application provides a preparation method of photochromic fiber, which comprises the following steps: adding a hydrate nitrate of a photochromic element into a sodium tungstate solution, adding hydrochloric acid to adjust the pH value, carrying out a hydrothermal reaction in a reaction kettle, adding polyvinyl alcohol into the obtained reaction solution, stirring at room temperature, and obtaining a color-changing coating; washing and drying a fiber, putting the fiber into the color-changing coating, soaking and drying, and obtaining the photochromic fiber. The sodium tungstate and the photochromic element (such as Ni, Eu, and Nd) are combined to synthesize the color-changing coating through the hydrothermal reaction, the fiber which is washed and dried is soaked in the prepared color-changing coating, the fiber surface is adsorbed with the coating to form a film with photochromic property, and the photochromic fiber is obtained after washing and drying. The photochromic fiber prepared by the application has the advantages of simple operation, low cost, wide range of flexible fiber as a base material, easy preparation, and the like, and the photochromic property of the fiber is not changed after weaving, so that the application of the fiber in the wearable field is widened.

Description

Technical Field

[0001] This invention relates to the field of fiber technology, and in particular to a method for preparing photochromic fibers. Background Technology

[0002] With increasing demand for functions such as physiological signal acquisition, performance monitoring, temperature control, and energy storage, modern clothing is developing towards greater intelligence. However, most smart clothing currently is made by integrating electronic technology into ordinary garments, rather than being made of truly functional fibers. In recent years, many light-emitting devices have seen widespread development due to their unique one-dimensional structure, enabling them to be perfectly embedded in textiles or clothing and showing broad application prospects in portable and wearable devices. Examples include solar cells, supercapacitors, color changers, and electroluminescent devices. These functional devices represent an important direction for the development of smart textiles. Among various functional memory devices, intelligent color-changing memory has become a potential hotspot for applications such as wearable displays, visual sensors, and military cameras.

[0003] Photochromic applications do not require complex circuits and power supplies; the material changes color when heated by a light source. Among currently researched photochromic materials, tungsten trioxide (WO3) has become one of the most widely used. Combining WO3 nanomaterials with other photosensitive substances can improve its photochromic properties. Rare earth elements such as Ni, Nd, and Eu all exhibit significant photosensitivity. How to combine these photosensitive substances with fibers to prepare photochromic fibers that are both flexible and enable intelligent visualization is a problem that needs to be solved.

[0004] In view of this, it is necessary to design an improved method for preparing photochromic fibers to solve the above problems. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a method for preparing photochromic fibers that is simple to synthesize, low in cost, fast in color-changing switching rate, stable in cycle, and flexible.

[0006] To achieve the above objectives, the present invention provides a method for preparing photochromic fibers, comprising the following steps:

[0007] S1. Prepare a sodium tungstate solution for later use;

[0008] S2. Add the hydrated nitrate of the photochromic element to the sodium tungstate solution obtained in step S1, cover the light and stir for 20-30 min, add hydrochloric acid to adjust the pH value, continue to cover the light and stir for 20-30 min to obtain a mixed solution.

[0009] S3. Transfer the mixed solution obtained in step S2 into a reaction vessel for hydrothermal reaction. After the reaction is completed, remove the reaction solution for later use.

[0010] S4. Add polyvinyl alcohol to the reaction solution obtained in step S3, stir at room temperature for 10-15 minutes to obtain a color-changing coating;

[0011] S5. After cleaning and drying the fibers, place them in the color-changing coating obtained in step S4, soak and dry them to obtain photochromic fibers.

[0012] As a further improvement of the present invention, in step S1, the concentration of the sodium tungstate solution is 0.05 to 0.1 mol / L.

[0013] As a further improvement of the present invention, in step S2, the hydrated nitrate of the photochromic element is Eu(NO3)3·6H2O, Ni(NO3)2·6H2O or Nd(NO3)3·6H2O.

[0014] Furthermore, the amount of the hydrated nitrate of the photochromic element added accounts for 20-50 wt% of the sodium tungstate.

[0015] As a further improvement of the present invention, in step S2, the concentration of hydrochloric acid added is 3-5 mol / L, and the pH value is adjusted to 1.2±0.05.

[0016] As a further improvement of the present invention, in step S3, the reaction temperature of the hydrothermal reaction is 120-150°C and the reaction time is 3-5 hours.

[0017] Furthermore, the concentration of the resulting reaction solution is 0.25–0.5 mol / L.

[0018] As a further improvement of the present invention, in step S4, the amount of polyvinyl alcohol added accounts for 1 to 3 wt% of the reaction solution.

[0019] As a further improvement of the present invention, in step S5, the fiber is cotton fiber, polyester fiber or aramid fiber; the fiber is cleaned by ultrasonication in ethanol and deionized water for 15 to 20 minutes respectively.

[0020] As a further improvement of the present invention, in step S5, the soaking time is 20-30 minutes, the number of soaking times is 2-3 times, and the drying temperature is 60-65°C.

[0021] The beneficial effects of this invention are:

[0022] (1) The method for preparing photochromic fibers provided by this invention involves mixing sodium tungstate solution with hydrated nitrates of photochromic elements and synthesizing a photochromic coating through a hydrothermal reaction. The cleaned and dried fibers are then immersed in the prepared photochromic coating, allowing the coating to adsorb onto the fiber surface and form a photochromic film. After cleaning and drying, the photochromic fibers are obtained. The hydrothermal method for preparing photochromic coatings does not produce toxic or harmful substances, is environmentally friendly and pollution-free, and is simple to operate with low cost. It can be used as a substrate for a wide range of flexible fibers, is readily available, and can be woven without altering its photochromic properties, thus broadening its application in the wearable field.

[0023] (2) The color of the photochromic fiber of the present invention can change with different wavelengths of light, and the color change is obvious and has good stability. After irradiating the photochromic fiber with a 365nm ultraviolet lamp for 3 to 5 minutes, the color-changing coating on the fiber surface can change from grayish-white to blue-black; when the colored fiber is irradiated with an 800 to 1500nm infrared lamp for about 15 minutes, the color of the fiber surface returns to grayish-white.

[0024] (3) In this invention, sodium tungstate is combined with hydrated nitrates of other photosensitive elements, which significantly enhances the photochromic properties of WO3 and increases the color contrast between the colored state and the original state. Among them, Nd element has better light sensitivity, and the synthesized color-changing coating is more uniform and more tightly combined with the fiber, thus giving the obtained color-changing fiber excellent photochromic properties and stability. Attached Figure Description

[0025] Figure 1 This is a SEM image of the photochromic fiber prepared in Example 1 of the present invention.

[0026] Figure 2 The following are actual images of the photochromic fiber prepared in Example 1 of this invention: (a) original state, (b) colored state, (c) faded state.

[0027] Figure 3 This is a SEM image of the photochromic fiber prepared in Example 2 of the present invention.

[0028] Figure 4 This is a SEM image of the photochromic fiber prepared in Example 3 of the present invention.

[0029] Figure 5 This is a SEM image of the photochromic fiber prepared in Example 4 of the present invention.

[0030] Figure 6 This is a SEM image of the photochromic fiber prepared in Example 5 of the present invention.

[0031] Figure 7The following are actual images of the photochromic fiber prepared in Example 5 of the present invention: (a) original state, (b) colored state, (c) faded state.

[0032] Figure 8 The following are actual images of the photochromic fibers prepared for Comparative Example 1: (a) original state, (b) colored state, (c) faded state.

[0033] Figure 9 The following are actual images of the photochromic fiber prepared for Comparative Example 2: (a) original state, (b) colored state.

[0034] Figure 10 SEM image of the photochromic fiber prepared in Comparative Example 3. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] It should also be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and / or processing steps closely related to the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.

[0037] Additionally, it should be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0038] The present invention provides a method for preparing photochromic fibers, comprising the following steps:

[0039] S1. Prepare a sodium tungstate solution for later use.

[0040] Specifically, sodium tungstate is added to deionized water and stirred for 5–10 minutes to prepare a sodium tungstate solution with a concentration of 0.05–0.1 mol / L.

[0041] S2. Add the hydrated nitrate of the photochromic element to the sodium tungstate solution obtained in step S1, cover with light and stir for 20-30 minutes, add hydrochloric acid to adjust the pH value, and continue to cover with light and stir for 20-30 minutes to obtain a mixed solution.

[0042] Specifically, the amount of hydrated nitrate of the photochromic element added is 20-50 wt% of the sodium tungstate. The mixture is then stirred in the dark for 20-30 minutes, and hydrochloric acid is added to adjust the pH to 1.2 ± 0.05. The mixture is then stirred in the dark for another 20-30 minutes to obtain a mixed solution.

[0043] In the above steps, the concentration of hydrochloric acid added is preferably 3-5 mol / L. The hydrated nitrate of the photochromic element is preferably Eu(NO3)3·6H2O, Ni(NO3)2·6H2O, or Nd(NO3)3·6H2O. More preferably, the hydrated nitrate of the photochromic element is Nd(NO3)3·6H2O.

[0044] S3. Transfer the mixed solution obtained in step S2 into the reactor for hydrothermal reaction. After the reaction is completed, remove the reaction solution for later use.

[0045] Specifically, the mixed solution obtained in step S2 is transferred into the liner of a polytetrafluoroethylene reactor and reacted at 120-150°C for 3-5 hours. After the reaction is completed, the solution is taken out, the supernatant is removed, and the reaction solution with a certain concentration is left for later use.

[0046] The concentration of the reaction solution remaining after removing part of the supernatant (calculated mainly with WO3) is 0.25–0.5 mol / L.

[0047] S4. Add polyvinyl alcohol (PVA) to the reaction solution obtained in step S3, stir at room temperature for 10-15 minutes to obtain a color-changing coating.

[0048] Specifically, the amount of polyvinyl alcohol (PVA) added is preferably 1 to 3 wt% of the reaction solution.

[0049] More preferably, the amount of polyvinyl alcohol (PVA) added accounts for 1 to 2 wt% of the reaction solution.

[0050] S5. After cleaning and drying the fiber, place it in the color-changing coating obtained in step S4, soak and dry it to obtain photochromic fiber.

[0051] Specifically, the fiber is ultrasonically treated in ethanol and deionized water for 15-20 minutes respectively, then dried, and then immersed in the color-changing coating obtained in step S4 for 20-30 minutes. After being removed, it is dried in an oven at 60°C. After 2-3 immersion and drying cycles, photochromic fiber is obtained.

[0052] Fibers include, but are not limited to, cotton fiber, polyester fiber, aramid fiber, etc.

[0053] The preparation method of the photochromic fiber provided by the present invention will be described below with reference to specific embodiments.

[0054] Example 1

[0055] Example 1 provides a method for preparing photochromic fibers, comprising the following steps:

[0056] S1. Prepare a sodium tungstate solution with a concentration of 0.1 mol / L using deionized water and stir for 5 min.

[0057] S2. Add Nd(NO3)3·6H2O to the sodium tungstate solution obtained in step S1. The amount added is 20wt% of the sodium tungstate. Protect the solution from light and stir for 20 min. Add hydrochloric acid with a concentration of 3 mol / L to adjust the pH of the solution to 1.2. Continue to protect the solution from light and stir for 20 min to obtain a mixed solution.

[0058] S3. Add the mixed solution prepared in step S2 into the lining of the polytetrafluoroethylene reactor for hydrothermal reaction. The hydrothermal reaction conditions are: reaction temperature 150℃, reaction time 3h. After the reaction is completed, remove part of the supernatant. The concentration of the remaining reaction solution (calculated mainly with WO3) is 0.25mol / L.

[0059] S4. Add 1 wt% polyvinyl alcohol to the reaction solution obtained in step S3, stir at room temperature for 10 min to obtain the color-changing coating.

[0060] S5. Take 5cm of cotton fiber, sonicate it in ethanol and deionized water for 15min respectively, then dry it. Soak it in the color-changing coating of step S4 for 20min, take it out and dry it in an oven at 60℃. After soaking and drying twice, photochromic fiber is obtained.

[0061] Please see Figure 1 The image shown is a SEM image of the photochromic fiber prepared in Example 1. As can be seen from the image, the cotton fiber surface is uniformly covered with a color-changing coating of a certain thickness. WO3 particles and Nd crystals are visible attached to the color-changing coating, indicating that the hydrothermal method for preparing this composite color-changing coating is feasible.

[0062] Please see Figure 2 The images shown are actual photos of the photochromic fibers prepared in Example 1: (a) original state, (b) colored state, and (c) faded state. The cotton fibers, after being soaked in the color-changing coating, remain white. Figure 2 As shown in (a), when the color-changing fiber is irradiated under a UV lamp for 3 minutes, it is stained and can be seen that the fiber clearly turns blue-black, as shown in (a). Figure 2 As shown in (b); the color-changing fiber was irradiated under an infrared lamp for 15 minutes to decolorize it, and the fiber returned to its white color, as shown in (b). Figure 2 As shown in (c), however, compared to the original white, this color is grayish-white. This is because the crystals of WO3 and Nd have a certain degree of retention in the absorption of light particles, so the color is partially changed.

[0063] Example 2

[0064] Example 2 provides a method for preparing photochromic fibers. Compared with Example 1, the difference is that in step S2, 50wt% of Nd(NO3)3·6H2O is added. Other experimental parameters and conditions are basically the same as in Example 1, and will not be repeated here.

[0065] Please see Figure 3 The image shown is a SEM image of the photochromic fiber prepared in Example 2. As the concentration of the hydrated nitrate of the photochromic element increases to 50 wt%, Nd... 3+ Nd has gradually occupied all the voids in the internal structure of hexagonal WO3. 3+ The composite has reached saturation. SEM shows large aggregates. Although the color-changing fiber can still achieve photochromism, its color-changing time has increased significantly. The coloring time under ultraviolet light has increased to 7 minutes, and the fading time under infrared light requires about 18 minutes.

[0066] Example 3

[0067] Example 3 provides a method for preparing photochromic fibers. Compared with Example 1, the difference is that 3 wt% PVA is added in step S4. Other experimental parameters and conditions are basically the same as in Example 1, and will not be repeated here.

[0068] Please see Figure 4 The image shown is an SEM image of the photochromic fiber prepared in Example 3. PVA mainly enhances the adhesion of the photochromic coating to the fiber. It can be seen that when the PVA content reaches 3wt%, the photochromic layer on the fiber surface begins to break, and the film thickness increases significantly. Due to the PVA coating, the photochromic particles on the fiber surface are not conducive to absorbing light energy. Although photochromism can still be achieved, the color change is not obvious compared with Example 1.

[0069] Example 4

[0070] Example 4 provides a method for preparing photochromic fibers. Compared with Example 1, the difference is that in step S2, 20wt% of Eu(NO3)3·6H2O is added. Other experimental parameters and conditions are basically the same as in Example 1, and will not be repeated here.

[0071] Please see Figure 5 The image shows a SEM image of the photochromic fiber prepared in Example 4. Figure 5 It can be seen that the number of attached particles on the fiber surface is significantly reduced, and the integrity of the WO3 particles is somewhat compromised, indicating that Eu... 3+ It has a significant impact on the WO3 crystal form, but the color-changing coating applied to the fiber still has a certain color-changing ability. The coloring time under ultraviolet light is increased to 8 minutes, and the fading time under infrared light is increased to 30 minutes, and the fading is not obvious.

[0072] Example 5

[0073] Example 5 provides a method for preparing photochromic fibers. Compared with Example 1, the difference is that in step S2, 20wt% of Ni(NO3)2·6H2O is added. Other experimental parameters and conditions are basically the same as in Example 1, and will not be repeated here.

[0074] Please see Figure 6 The image shown is a SEM image of the photochromic fiber prepared in Example 5. As can be seen from the image, the cotton fiber is uniformly covered with a color-changing coating, with a high concentration of WO3 particles and a low concentration of NiO crystals.

[0075] Please see Figure 7 The image shows the actual color-changing state of the photochromic fiber prepared in Example 5: (a) original state, (b) colored state, and (c) faded state. Photochromic testing revealed that its coloring time under ultraviolet light was 5–6 minutes, and its fading time under infrared light was 16–17 minutes. Furthermore, the image shows that the faded state exhibits a bluish-gray color, indicating that its fading ability is slightly weak.

[0076] Comparative Example 1

[0077] Comparative Example 1 provides a method for preparing photochromic fibers. Compared with Example 1, the difference is that in step S2, hydrated nitrate of the photochromic element is not added. Other experimental parameters and conditions are basically the same as those in Example 1, and will not be repeated here.

[0078] Please see Figure 8 The images shown are actual photos of the photochromic fibers prepared from hydrated nitrates without the addition of photochromic elements in Comparative Example 1: (a) original state, (b) colored state, (c) faded state. Figure 8 It can be seen that when no hydrated nitrate containing photochromic elements is added, and only WO3 is used as the photochromic coating, the fiber shows a light gray color after adhesion, a deep black color after exposure to ultraviolet light, and an infrared light restoration time of more than 30 minutes. Moreover, the color remains grayish-blue after fading, and the color contrast is significantly reduced compared to the composite color-changing coating in Example 1.

[0079] Comparative Example 2

[0080] Comparative Example 2 provides a method for preparing photochromic fibers. Compared with Example 1, the difference is that PVA is not added in step S4. Other experimental parameters and conditions are basically the same as in Example 1, and will not be repeated here.

[0081] Please see Figure 9The image shows the photochromic fibers prepared without PVA in Comparative Example 2: (a) original state, (b) colored state. Compared with Example 1, without the addition of PVA, its adhesion to the cotton fibers was too small, resulting in the fibers only changing from white to gray after 10 minutes of UV irradiation. This indicates that the color-changing coating on the fiber needs to reach a certain thickness to achieve color change. The presence of PVA can enhance the composite between the coating and the fiber, improving its color-changing stability.

[0082] Comparative Example 3

[0083] Comparative Example 3 provides a method for preparing photochromic fibers. Compared with Example 1, the difference is that in step S2, 3 mol / L HCl is replaced with 3 mol / L H2SO4. Other experimental parameters and conditions are basically the same as in Example 1, and will not be repeated here.

[0084] Please see Figure 10 The image shown is a SEM image of the photochromic fiber prepared in Comparative Example 3. Compared with Example 1, the pH was adjusted using H2SO4, resulting in a more vigorous reaction in the system during the preparation of the precursor solution. This affected the synthesis of Nd crystals, leading to more dispersed particles and a lower solution concentration in the reaction solution. Consequently, the number of effective color-changing particles decreased, and the color-changing performance deteriorated.

[0085] Comparative Example 4

[0086] Comparative Example 4 provides a method for preparing photochromic fibers. The difference from Example 1 is that 3.5 wt% PVA is added in step S4. Other experimental parameters and conditions are the same as in Example 1, and will not be repeated here.

[0087] Experiments show that as the PVA concentration continues to increase, the viscosity of the solution increases significantly, which is not conducive to the adhesion of the reaction solution to the fiber and results in very low uniformity, leading to poor photochromic properties of the fiber.

[0088] In summary, the method for preparing photochromic fibers provided by this invention, by combining sodium tungstate with hydrated nitrates of other photosensitive elements, significantly enhances the photochromic properties of WO3, and the resulting photochromic fibers exhibit good photochromic properties and stability.

[0089] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing photochromic fibers, characterized in that, Includes the following steps: S1. Prepare a sodium tungstate solution for later use; S2. Add the hydrated nitrate of the photochromic element to the sodium tungstate solution obtained in step S1, cover with light and stir for 20-30 min, add hydrochloric acid to adjust the pH value, and continue stirring in the dark for 20-30 min to obtain a mixed solution; the hydrated nitrate of the photochromic element is Ni(NO3)2·6H2O or Nd(NO3)3·6H2O; the amount of the hydrated nitrate of the photochromic element added is 20-50 wt% of the sodium tungstate. S3. Transfer the mixed solution obtained in step S2 into a reaction vessel for hydrothermal reaction. After the reaction is completed, remove the reaction solution for later use. S4. Add polyvinyl alcohol to the reaction solution obtained in step S3, stir at room temperature for 10-15 minutes to obtain a color-changing coating; the amount of polyvinyl alcohol added is 1-3 wt% of the reaction solution; S5. After cleaning and drying the fibers, place them in the color-changing coating obtained in step S4, soak and dry them to obtain photochromic fibers.

2. The method for preparing photochromic fibers according to claim 1, characterized in that, In step S1, the concentration of the sodium tungstate solution is 0.05~0.1 mol / L.

3. The method for preparing photochromic fibers according to claim 1, characterized in that, In step S2, the concentration of hydrochloric acid is 3~5 mol / L, and the pH value is adjusted to 1.2±0.

05.

4. The method for preparing photochromic fibers according to claim 1, characterized in that, In step S3, the hydrothermal reaction temperature is 120~150℃ and the reaction time is 3~5h.

5. The method for preparing photochromic fibers according to claim 1, characterized in that, In step S3, the concentration of the reaction solution is 0.25~0.5mol / L.

6. The method for preparing photochromic fibers according to claim 1, characterized in that, In step S5, the fiber is cotton fiber, polyester fiber or aramid fiber; the fiber is cleaned by ultrasonication in ethanol and deionized water for 15-20 minutes respectively.

7. The method for preparing photochromic fibers according to claim 1, characterized in that, In step S5, the soaking time is 20-30 minutes, the soaking is repeated 2-3 times, and the drying temperature is 60-65℃.

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