Photochromic curtain fabric and preparation method thereof

Abstract

The invention relates to the technical field of textile materials, in particular to a photochromic curtain fabric and a preparation method thereof. The color-changing curtain fabric overcomes the problems of unstable color-changing performance and poor durability of the existing curtain fabric. The modified polyimide is synthesized through copolymerization and imidization reaction; carrying out two-stage melt blending on components such as a photochromic microcapsule and a composite dispersant with the modified polyimide to prepare a mixed material containing polyimide; performing spinning forming and surface modification to form surface modified polyimide fibers; and finally obtaining the photochromic curtain fabric through dip-coating curing and weaving processes. Polyimide is modified, so that the mechanical property and the color change stability of the fabric are enhanced; the other components cooperate with one another to improve the aging resistance of the fabric, and the requirements of the textile material on functionality and durability are met.

Description

Technical Field

[0001] The invention relates to the technical field of textile materials, in particular to a photochromic curtain fabric and a preparation method thereof. Background Art

[0002] Since the discovery of photochromism in the early 20th century, photochromic materials such as spiropyran and azobenzene have continued to develop. Their reversible color change under illumination has found widespread application in fields such as optical information storage and anti-counterfeiting. In the textile field, color-changing fabrics are fabrics that change color in response to changes in external conditions such as light, temperature, humidity, and force. Photochromic materials enable fabrics to adjust their color and light transmittance in response to light, enhancing the decorative properties of curtain fabrics.

[0003] Currently, polyimide fabrics, such as clothing and nonwovens, have seen a significant expansion in applications such as labor protection, firefighting, and bulletproof vests. However, due to factors such as the single color of polyimide, their application remains relatively narrow. With increasing market demand for polyimide fabrics with diverse colors, polyimide fabrics with photochromic properties can be prepared for curtain fabrics by modifying polyimide, such as by introducing photochromic groups or compounding with photochromic materials.

[0004] However, when preparing photochromic polyimide fabrics, due to the differences in chemical structure and physical properties between polyimide and photochromic materials (such as azobenzene, spiropyran-benzoxazine, etc.), phase separation may occur during the blending process, which will lead to a reduction in the photochromic effect of the photochromic polyimide fabric; and during the processing and use of photochromic polyimide fibers, they may be affected by factors such as oxidation and hydrolysis, thereby affecting the synergistic effect between the polyimide fabric and the photochromic material, further reducing the stability and durability of the photochromic polyimide fabric.

[0005] Therefore, a photochromic curtain fabric and a preparation method thereof are proposed. Summary of the Invention

[0006] The purpose of the present invention is to design a photochromic curtain fabric and a preparation method thereof. The present invention prepares a modified polyimide through copolymerization and imidization reaction, then adds photochromic microcapsules, a composite dispersant, a composite antioxidant, and a composite ultraviolet absorber to perform two-stage melt blending to obtain a mixed material, and then performs spinning and modification to obtain surface-modified fibers. Finally, the photochromic curtain fabric is obtained by dip-coating, curing, and weaving. The modified polyimide, photochromic microcapsules, and composite dispersant synthesized by the present invention can synergistically improve the mechanical properties and color change stability of the curtain fabric; the composite antioxidant, composite ultraviolet absorber, and the two-stage melt blending process can improve the curtain fabric's resistance to light oxidation; and the spinning, surface modification, and dip-coating curing processes synergistically improve the curtain fabric's aging resistance.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] In one aspect, the present invention provides a method for preparing a photochromic curtain fabric, the method comprising the following steps:

[0009] S1: adding spiropyran-benzoxazine to 4,4'-diaminodiphenyl ether and mixing, and then adding pyromellitic dianhydride to carry out copolymerization and imidization reaction to obtain a modified polyimide;

[0010] S2: adding photochromic microcapsules, a composite dispersant, a composite antioxidant, and a composite ultraviolet absorber to the modified polyimide for two-stage melt blending to obtain a mixed material; the photochromic microcapsules include azobenzene, urea, and formaldehyde;

[0011] S3: spinning the mixed material with a stretching ratio of 2-4:1 and a spinning speed of 800 m / min to obtain spun fibers; soaking the spun fibers in a 5% by mass γ-aminopropyltriethoxysilane solution for 5 min-15 min, and drying at 80° C. to obtain surface-modified fibers;

[0012] S4 solidifies the composite coating liquid on the surface modified fiber by dip coating, and then weaves it to obtain the photochromic curtain fabric.

[0013] Preferably, the specific process of the copolymerization and imidization reaction is as follows: 90-110 parts of 4,4'-diaminodiphenyl ether are added to a four-necked flask, nitrogen is introduced, and then 200 parts of N-methylpyrrolidone are added. The stirring speed is 280 rpm, the reaction temperature is 25 ° C, and the stirring is 30 min-60 min to obtain a premixed solution; 5-15 parts of spiropyran-benzoxazine are added to the premixed solution and the stirring is continued for 80 min to obtain a mixed solution; 100-105 parts of pyromellitic dianhydride are slowly added to the mixed solution, the time is controlled to be 80 min, and the temperature is 5 ° C. After the addition is completed, the reaction temperature is slowly raised to 25°C, and the reaction is stirred continuously for 15h-20h to form a polyamic acid solution; the polyamic acid solution is placed in a vacuum oven, and under vacuum conditions, the temperature is raised to 100°C at a heating rate of 3°C / min, and maintained for 1.5h; then the temperature is raised to 150°C at a rate of 2°C / min, and maintained for 1.5h; then the temperature is raised to 200°C at a rate of 2°C / min, and maintained for 1.5h; finally, the temperature is raised to 250°C at a rate of 1°C / min, and maintained for 2h-3h to obtain a modified polyimide with a viscosity of 0.8dL / g-1.2dL / g.

[0014] Preferably, the preparation method of the photochromic microcapsules is as follows: 15-20 parts of urea and 30-40 parts of formaldehyde are added to a three-necked flask, the pH value is adjusted to 8 with sodium hydroxide solution, and the mixture is stirred in a water bath at 60°C-70°C for 2h to obtain a prepolymer solution; in another container, 10 parts of azobenzene and 30 parts of deionized water are added, and 1 part of sodium dodecylbenzenesulfonate is added, and the mixture is stirred at a speed of 7000 rpm for 25min to form a uniform emulsion; the prepolymer solution is slowly added dropwise to the uniform emulsion, the pH value of the reaction system is adjusted to 4 with hydrochloric acid solution, the reactor is heated to 65°C, and the reaction is stirred for 2h-3h to obtain semi-finished microcapsules; after the reaction is completed, the reactor is cooled to room temperature, the pH value is adjusted to neutral with sodium hydroxide solution, the product is filtered, washed with deionized water and vacuum dried to obtain photochromic microcapsules.

[0015] Preferably, the composite dispersant comprises sodium tripolyphosphate and sodium dodecylbenzene sulfonate, and the weight ratio of sodium tripolyphosphate to sodium dodecylbenzene sulfonate is 1-5:2.

[0016] Preferably, the composite antioxidant includes antioxidant 1010 and antioxidant 626, and the weight ratio of antioxidant 1010 to antioxidant 626 is 3:1-5; the composite ultraviolet absorber includes Tinuvin 326 and Tinuvin 770, and the weight ratio of Tinuvin 326 to Tinuvin 770 is 1-3:1.

[0017] Preferably, the specific process of the two-stage melt blending is as follows, by weight: 100 parts of modified polyimide, 1-5 parts of photochromic microcapsules and 0.3-0.8 parts of composite dispersant are added to a twin-screw extruder, the temperature of the front section of the extruder is set to 320°C, the temperature of the middle section is set to 330°C, and the temperature of the rear section is set to 340°C, and the mixture is blended at a speed of 600rpm for 10min to obtain a first mixed material; 0.1-0.5 parts of composite antioxidant and 0.1-0.5 parts of composite ultraviolet absorber are added to the first mixed material, and the mixture is blended at a speed of 300rpm-500rpm for 5min-10min, and a mixed material is obtained after extrusion.

[0018] Preferably, the composite coating liquid is obtained by dispersing nano-titanium dioxide in polyurethane resin, wherein the mass fraction of nano-titanium dioxide is 1%-5%; the specific process of dip coating and curing is: immersing the surface modified fiber in the composite coating liquid, controlling the dipping time to be 1min-5min, and curing it at 120°C for 8min-12min after taking it out.

[0019] Another aspect of the present invention provides a photochromic curtain fabric. The raw materials for preparing the curtain fabric include modified polyimide, photochromic microcapsules, a composite dispersant, a composite antioxidant and a composite ultraviolet absorber; the modified polyimide includes spiropyran-benzoxazine, 4,4'-diaminodiphenyl ether and pyromellitic dianhydride, and the photochromic microcapsules include azobenzene, urea and formaldehyde.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. Spiropyran-benzoxazine is added to the copolymerization system of 4,4'-diaminodiphenyl ether and pyromellitic dianhydride. The copolymerization reaction introduces the spiropyran-benzoxazine structure into the polyimide molecular chain, giving the polyimide photochromic properties; the imidization reaction enables the polymer to form a stable imide structure, which has high strength and toughness. An appropriate amount of spiropyran-benzoxazine can further enhance the force between molecular chains through intermolecular interactions, thereby improving the mechanical properties of curtain fabrics.

[0022] 2. Modified polyimide serves as a matrix material, providing support and protection for the photochromic microcapsules, enabling them to be evenly dispersed throughout the system. Furthermore, the photochromic properties of the modified polyimide complement those of the photochromic microcapsules, enhancing the color-changing effect of the curtain fabric. The azobenzene in the photochromic microcapsules undergoes a photochromic reaction under the influence of light, and microencapsulation protects the azobenzene from the external environment, improving its photostability and service life. The composite dispersant evenly disperses the photochromic microcapsules in the modified polyimide, preventing agglomeration and enhancing compatibility between the microcapsules and the modified polyimide. These three factors work together to improve the stability of the curtain fabric's color-changing properties.

[0023] 3. The first stage of melt blending thoroughly mixes the modified polyimide, photochromic microcapsules, and composite dispersant, providing a uniform matrix for subsequent application. The second stage of melt blending adds the composite antioxidant and composite UV absorber, followed by further blending to evenly disperse them throughout the system. This two-stage melt blending ensures uniform distribution of the various additives within the modified polyimide, synergizing to effectively improve the curtain fabric's resistance to photooxidation. The composite UV absorber absorbs most of the UV radiation, reducing UV-induced oxidation reactions; the composite antioxidant captures and decomposes the remaining free radicals and peroxides, further inhibiting oxidation reactions. The synergistic effect of the two enhances the curtain fabric's resistance to photooxidation from both UV shielding and oxidation inhibition, extending its durability.

[0024] 4. The surface-modified fibers in S3 enhance adhesion to the composite coating solution, allowing the composite coating solution in S4 to be more effectively applied to the fiber surface, forming a uniform, durable coating. The composite coating formed by nano-titanium dioxide and polyurethane resin works in conjunction with the surface-modified fibers. The silanized film and the composite coating work together to improve the curtain fabric's aging resistance by blocking UV rays, preventing oxygen and moisture erosion, and enhancing wear resistance, ensuring the curtain fabric maintains excellent performance over long-term use. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a graph showing the UVA shielding rates of Example 18 and Comparative Examples 18-21 before and after washing in the present invention. DETAILED DESCRIPTION

[0026] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0027] Specific reference Figure 1 The present invention provides a photochromic curtain fabric and a preparation method thereof, and the technical solution is as follows:

[0028] Example 1

[0029] 15 parts of urea and 30 parts of formaldehyde were added to a three-necked flask, the pH value was adjusted to 8 with sodium hydroxide solution, and the mixture was stirred in a water bath at 60°C for 2 hours to obtain a prepolymer solution; in another container, 10 parts of azobenzene and 30 parts of deionized water were added, and 1 part of sodium dodecylbenzenesulfonate was added, and the mixture was stirred at a speed of 7000 rpm for 25 minutes to form a uniform emulsion; the prepolymer solution was slowly added dropwise to the uniform emulsion, the pH value of the reaction system was adjusted to 4 with hydrochloric acid solution, the reactor was heated to 65°C, and the mixture was stirred for 2 hours to obtain semi-finished microcapsules; after the reaction, the reactor was cooled to room temperature, the pH value was adjusted to neutral with sodium hydroxide solution, the product was filtered, washed with deionized water and vacuum dried to obtain photochromic microcapsules.

[0030] The composite dispersant includes sodium tripolyphosphate and sodium dodecylbenzene sulfonate, and the weight ratio of sodium tripolyphosphate to sodium dodecylbenzene sulfonate is 1:2; the composite antioxidant includes antioxidant 1010 and antioxidant 626, and the weight ratio of antioxidant 1010 to antioxidant 626 is 3:1; the composite ultraviolet absorber includes Tinuvin 326 and Tinuvin 770, and the weight ratio of Tinuvin 326 to Tinuvin 770 is 1:1.

[0031] Preparation of photochromic curtain fabric:

[0032] S1: Add 90 parts of 4,4'-diaminodiphenyl ether into a four-necked flask, introduce nitrogen, then add 200 parts of N-methylpyrrolidone, start stirring, the speed is 280 rpm, the reaction temperature is 25 ° C, and stir for 30 minutes to obtain a premixed solution; add 5 parts of spiropyran-benzoxazine to the premixed solution, continue stirring for 80 minutes to obtain a mixed solution; slowly add 100 parts of pyromellitic dianhydride to the mixed solution, control the time to be 80 minutes, and the temperature to 5 ° C. After the addition is completed, slowly lower the reaction temperature to 5 ° C. The temperature was raised to 25°C, and the reaction was continued with stirring for 15 hours to form a polyamic acid solution; the polyamic acid solution was placed in a vacuum oven, and under vacuum conditions, the temperature was raised to 100°C at a heating rate of 3°C / min and maintained for 1.5 hours; then the temperature was raised to 150°C at a rate of 2°C / min and maintained for 1.5 hours; then the temperature was raised to 200°C at a rate of 2°C / min and maintained for 1.5 hours; finally, the temperature was raised to 250°C at a rate of 1°C / min and maintained for 2 hours to obtain a modified polyimide with a viscosity of 0.8 dL / g;

[0033] S2: 100 parts of modified polyimide, 1 part of photochromic microcapsules and 0.3 parts of composite dispersant are added to a twin-screw extruder, and the temperature of the front section of the extruder is set to 320° C., the temperature of the middle section is set to 330° C., and the temperature of the back section is set to 340° C., and the mixture is blended at a speed of 600 rpm for 10 minutes to obtain a first mixed material; 0.1 parts of composite antioxidant and 0.1 parts of composite ultraviolet absorber are added to the first mixed material, and the mixture is blended at a speed of 300 rpm for 5 minutes, and a mixed material is obtained after extrusion;

[0034] S3: spinning the mixed material with a stretching ratio of 2:1 and a spinning speed of 800 m / min to obtain spun fibers; soaking the spun fibers in a 5% by mass γ-aminopropyltriethoxysilane solution for 5 minutes, and drying at 80° C. to obtain surface-modified fibers;

[0035] S4 immerses the surface-modified fiber in a composite coating liquid, controls the immersion time to be 1 minute, takes it out and cures it at 120°C for 8 minutes, and then weaves it to obtain a photochromic curtain fabric; the composite coating liquid is obtained by dispersing nano-titanium dioxide in a polyurethane resin, wherein the mass fraction of the nano-titanium dioxide is 1%.

[0036] Examples 2-5

[0037] With reference to the parameter conditions in Example 1, the specific differences are shown in Table 1.

[0038] Table 1 Parameter conditions of Examples 1-5

[0039]

[0040] Comparative Example 1

[0041] The parameters and conditions are similar to those in Example 1, except that spiropyran-benzoxazine is not added to the copolymerization and imidization reactions.

[0042] Comparative Example 2

[0043] The parameters and conditions are similar to those in Example 1, except that only copolymerization reaction is performed.

[0044] Comparative Example 3

[0045] The parameters and conditions are similar to those in Example 1, except that only the imidization reaction is performed.

[0046] Comparative Example 4

[0047] The parameters and conditions are similar to those in Example 1, except that commercially available polyimide is directly added to participate in the subsequent reaction.

[0048] Experimental Example 1 Mechanical Properties and Color Change Performance Test

[0049] The mechanical properties of Examples 1-5 and Comparative Examples 1-4 were tested with reference to GB / T 3923.1-2013. Ultraviolet light was irradiated on Examples 1-5 and Comparative Examples 1-4 to observe whether the curtain fabrics showed photochromic changes. The results are shown in Table 2.

[0050] Table 2 Mechanical properties and color change performance tests of Examples 1-5 and Comparative Examples 1-4

[0051] Example Elongation at break / % Fracture stress / MPa Photochromic effect Example 1 38.4 41 Excellent Example 2 38.3 41 Excellent Example 3 38.6 43 Excellent Example 4 38.2 42 Excellent Example 5 38.0 40 Excellent Comparative Example 1 35.2 38 Poor Comparative Example 2 20.7 21 Poor Comparative Example 3 12.6 12 Poor Comparative Example 4 31.7 35 Poor

[0052] Table 2 shows that Examples 1-5 exhibit good mechanical and color-changing properties. In Comparative Example 1, the omission of spiropyran-benzoxazine alters the structure and properties of the modified polyimide. While the polyimide itself possesses high strength, the absence of spiropyran-benzoxazine alters the interactions between the molecular chains, resulting in a decrease in the mechanical properties of the final fabric. Spiropyran-benzoxazine is a photochromic compound, and its omission directly affects the fabric's color-changing properties. Consequently, the fabric fails to achieve the desired photochromic effect. The results of Comparative Example 2 show that copolymerization can connect different monomers together to form a copolymer, but imidization reaction is crucial for the structural formation and performance improvement of polyimide. If only copolymerization reaction is carried out, the molecular chain structure of the polymer is incomplete and a stable polyimide structure cannot be formed, which will lead to a significant decrease in the mechanical properties of the fabric; although copolymerization reaction can introduce some photochromic-related groups, imidization reaction helps to form a more stable conjugated structure, which has an important influence on the photochromic performance. Without imidization reaction, the stability of ingredients such as photochromic microcapsules in subsequent processing and their binding to the matrix will deteriorate, affecting the color change performance of the fabric. In Comparative Example 3, without copolymerization to connect the different monomers, there is no basic polymer chain for the imidization reaction. The imidization reaction cannot proceed effectively, and a polyimide with good mechanical properties cannot be formed, resulting in poor mechanical properties of the fabric. Since no photochromic-related groups or structures are introduced through copolymerization, the imidization reaction alone cannot provide the basis for photochromism in the fabric. The color-changing properties are provided only by the photochromic capsules, resulting in poor photochromic properties. In Comparative Example 4, the polyimide was directly added without undergoing copolymerization and imidization with spiropyran-benzoxazine. Its molecular structure and properties are relatively simple, and the mechanical properties of the curtain fabric will be affected during subsequent processing. Furthermore, the directly added polyimide lacks photochromic properties, resulting in poor color-changing properties. In summary, spiropyran-benzoxazine is added to the copolymerization system of 4,4'-diaminodiphenyl ether and pyromellitic dianhydride. The copolymerization reaction introduces the spiropyran-benzoxazine structure into the polyimide molecular chain, giving the polyimide photochromic properties; the imidization reaction enables the polymer to form a stable imide structure, which has high strength and toughness. An appropriate amount of spiropyran-benzoxazine can further enhance the force between molecular chains through intermolecular interactions, thereby improving the mechanical properties of curtain fabrics.

[0053] Examples 6-10

[0054] Referring to the parameter conditions in Example 3, the specific differences are shown in Table 3.

[0055] Table 3 Parameter conditions of Example 3 and Examples 6-10

[0056]

[0057] Comparative Example 5

[0058] Refer to the parameter conditions in Example 3, except that only polyimide is added without modification.

[0059] Comparative Example 6

[0060] Refer to the parameter conditions in Example 3, except that only azobenzene is added and no phenolic resin is used for coating.

[0061] Comparative Example 7

[0062] Refer to the parameter conditions in Example 3, except that no photochromic microcapsules are added.

[0063] Comparative Example 8

[0064] Refer to the parameter conditions in Example 3, except that only sodium tripolyphosphate is added as a dispersant.

[0065] Comparative Example 9

[0066] Refer to the parameter conditions in Example 3, except that only sodium dodecylbenzenesulfonate is added as the dispersant.

[0067] Comparative Example 10

[0068] Refer to the parameter conditions in Example 3, except that no composite dispersant is added.

[0069] Experimental Example 2 Color Change Performance Test

[0070] Example 3, Examples 6-10 and Comparative Examples 5-10 were irradiated with ultraviolet light to observe their color change effects. ◎ represents excellent color change, △ represents poor color change, and X represents no color change. The results are shown in Table 4.

[0071] Table 4 Color change performance test of Example 3, Examples 6-10 and Comparative Examples 5-10

[0072] Example Daylight hours (4 hours) Daylight hours (12 hours) Daylight hours (24 hours) Example 3 ◎ ◎ ◎ Example 6 ◎ ◎ ◎ Example 7 ◎ ◎ ◎ Example 8 ◎ ◎ ◎ Example 9 ◎ ◎ ◎ Example 10 ◎ ◎ ◎ Comparative Example 5 △ △ △ Comparative Example 6 ◎ △ △ Comparative Example 7 △ △ X Comparative Example 8 ◎ ◎ △ Comparative Example 9 ◎ ◎ △ Comparative Example 10 △ △ △

[0073] It can be found from Table 4 that the color-changing properties of all examples are relatively stable. In Comparative Example 5, only polyimide is added without modification. The unmodified polyimide lacks the spiropyran-benzoxazine structure, which will lead to a decrease in the sensitivity of the fabric to light, a slow color change speed, and a tendency for the color-changing properties to decline during long-term use. In Comparative Example 6, only azobenzene is added without coating with phenolic resin. Azobenzene is easily affected by factors such as oxygen and moisture and loses its effectiveness, resulting in a decrease in the photochromic properties of the fabric, with problems such as unclear color change and poor reversibility. In Comparative Example 7, without the addition of photochromic microcapsules, the fabric loses the material basis for photochromism, and the color-changing substance in the modified polyimide alone cannot achieve the photochromic function for a long time. In Comparative Examples 8-9, only sodium tripolyphosphate or sodium dodecylbenzene sulfonate is added as a dispersant, which will result in poor dispersion effect and uneven distribution of the photochromic microcapsules in the system, thereby making the photochromic properties of the fabric unstable. In Comparative Example 10, without the addition of a composite dispersant, the photochromic microcapsules were difficult to evenly disperse in the modified polyimide, resulting in agglomeration and other phenomena, seriously affecting the photochromic performance, leading to poor color change performance of the fabric and further reducing the color change stability of the curtain fabric. In summary, the modified polyimide, as a matrix material, provides support and protection for the photochromic microcapsules, enabling them to be evenly dispersed in the system. At the same time, the photochromic properties of the modified polyimide itself complement those of the photochromic microcapsules, enhancing the color change effect of the curtain fabric. The azobenzene in the photochromic microcapsules undergoes a photochromic reaction under the influence of light, and microencapsulation protects the azobenzene from the external environment, improving its photostability and service life. The composite dispersant enables the photochromic microcapsules to be evenly dispersed in the modified polyimide, preventing agglomeration, and better bonds between the microcapsules and the modified polyimide, improving compatibility. The combined effects of these three factors improve the stability of the color change performance of the curtain fabric.

[0074] Examples 11-15

[0075] Referring to the parameter conditions in Example 8, the specific differences are shown in Table 5.

[0076] Table 5 Parameters and conditions of Example 8 and Examples 11-15

[0077]

[0078] Comparative Example 11

[0079] Refer to the parameter conditions in Example 8, except that only antioxidant 1010 is added as the antioxidant.

[0080] Comparative Example 12

[0081] Refer to the parameter conditions in Example 8, except that only antioxidant 626 is added as the antioxidant.

[0082] Comparative Example 13

[0083] Refer to the parameter conditions in Example 8, except that no composite antioxidant is added.

[0084] Comparative Example 14

[0085] The parameters and conditions in Example 8 are the same, except that only Tinuvin 326 is added as the UV absorber.

[0086] Comparative Example 15

[0087] The parameters and conditions in Example 8 are the same, except that only Tinuvin 770 is added as the UV absorber.

[0088] Comparative Example 16

[0089] Refer to the parameter conditions in Example 8, except that no composite ultraviolet absorber is added.

[0090] Comparative Example 17

[0091] The parameters and conditions are similar to those in Example 8, except that the photochromic microcapsules, the composite dispersant, the composite antioxidant and the composite ultraviolet absorber are added together and melt-blended to obtain a mixed material.

[0092] Experimental Example 3 Anti-photooxidation performance

[0093] Example 8, Examples 11-15, and Comparative Examples 11-17 were tested for UV protection according to GB / T 18830-2009. Quantitative analysis was performed using spectrophotometry using the DPPH analysis method. The antioxidant properties of Examples 8, Examples 11-15, and Comparative Examples 11-17 were also tested by measuring their free radical scavenging rates. The results are shown in Table 6.

[0094] Table 6 Anti-photooxidation performance test of Example 8, Examples 11-15 and Comparative Examples 11-17

[0095] Example UVA shielding rate / % Free radical scavenging rate / % Example 8 98.2 88.91 Example 11 98.5 89.34 Example 12 98.8 89.97 Example 13 99.0 90.53 Example 14 98.9 89.86 Example 15 98.5 89.12 Comparative Example 11 94.3 70.22 Comparative Example 12 94.6 69.36 Comparative Example 13 85.8 41.25 Comparative Example 14 79.7 82.79 Comparative Example 15 80.3 82.14 Comparative Example 16 42.6 70.48 Comparative Example 17 86.2 76.32

[0096] Table 6 shows that the examples have strong anti-photooxidation capabilities. In Comparative Examples 11-12, only Antioxidant 1010 or Antioxidant 626 was added as an antioxidant. A single antioxidant is unable to fully and effectively inhibit the oxidation reaction, and its effectiveness in inhibiting free radical generation and terminating chain reactions is compromised, resulting in a decrease in the antioxidant performance of the fabric. In Comparative Example 13, no composite antioxidant was added. The fabric was susceptible to oxidation reactions caused by factors such as oxygen in the air and light during use, resulting in a significant decrease in antioxidant performance and a shortened service life of the fabric. In Comparative Examples 14-15, only Tinuvin 326 or Tinuvin 770 was added as an ultraviolet absorber. The range of ultraviolet wavelengths protected was limited, resulting in insufficient protection of the fabric against certain wavelengths of ultraviolet light, thereby reducing the fabric's ultraviolet protection. In Comparative Example 16, without the addition of a composite UV absorber, UV rays would cause the polymer materials in the fabric to undergo photodegradation and photooxidation reactions, resulting in a decrease in fabric performance. The fabric would then be unable to effectively block UV rays, resulting in extremely poor UV protection and being susceptible to UV damage, leading to problems such as fading and aging. In Comparative Example 17, this approach would affect the uniformity of the dispersion of the various components in the modified polyimide, causing interference between the components and poor dispersion, which in turn impacts the fabric's UV protection and antioxidant properties. In summary, the first stage of melt blending ensures a thorough and uniform mixing of the modified polyimide, photochromic microcapsules, and composite dispersant, providing a uniform matrix for subsequent processing. The second stage of melt blending, followed by the addition of the composite antioxidant and composite UV absorber, allows them to be evenly dispersed throughout the system. This two-stage melt blending ensures that the various additives are evenly distributed throughout the modified polyimide, working synergistically to effectively improve the curtain fabric's photooxidative resistance. The composite UV absorber first absorbs most of the UV rays to reduce the oxidation reaction caused by UV rays; the composite antioxidant captures and decomposes the remaining free radicals and peroxides to further inhibit the oxidation reaction; the two work synergistically to improve the anti-photooxidation performance of curtain fabrics from the two aspects of UV shielding and oxidation reaction inhibition, thereby extending the durability of the fabric.

[0097] Examples 16-20

[0098] Referring to the parameter conditions in Example 13, the specific differences are shown in Table 7.

[0099] Table 7 Parameters and conditions of Example 13 and Examples 16-20

[0100]

[0101] Comparative Example 18

[0102] Refer to the parameter conditions in Example 13, except that no surface modification treatment is performed in S3.

[0103] Comparative Example 19

[0104] Refer to the parameter conditions in Example 13, except that no dip coating and curing treatment is performed in S4.

[0105] Comparative Example 20

[0106] Refer to the parameter conditions in Example 13, except that the resin used for dip coating and curing in S4 is polyurethane resin.

[0107] Comparative Example 21

[0108] Refer to the parameter conditions in Example 13, except that the dip coating and curing treatment is performed first and then the surface modification treatment is performed.

[0109] Experimental Example 4 Aging resistance test

[0110] Referring to the test method of Experimental Example 3, the UV protection and antioxidant properties of Example 13, Examples 16-20 and Comparative Examples 18-21 were tested before and after washing 50 times. The results are shown in Table 8. The UVA shielding rates of Example 18 and Comparative Examples 18-21 before and after washing are shown in Table 8. Figure 1 shown.

[0111] Table 8 Aging resistance test of Example 13, Examples 16-20 and Comparative Examples 18-21

[0112]

[0113] From Table 8 and Figure 1It can be seen that the examples have good aging resistance. Comparative Example 18 shows that treatment with a γ-aminopropyltriethoxysilane solution can improve the surface properties of the fiber and enhance the bonding strength between the fiber and the subsequent coating. Without surface modification, the composite coating solution will not adhere firmly to the fiber surface. After 50 washes, the coating will easily fall off, causing the loss of components with UV protection and antioxidant properties, such as nano-titanium dioxide, and reducing the fabric's UV protection and antioxidant properties. In Comparative Example 19, because the nano-titanium dioxide in the composite coating solution has good UV protection, and the polyurethane resin can also protect the fiber from oxidation to a certain extent, without the dip-coating and curing treatment, the fabric lacks this protective coating and is directly exposed to the external environment. After washing, the fiber is more susceptible to UV and oxidation attacks, and its UV protection and antioxidant properties will be significantly reduced. In Comparative Example 20, only the polyurethane resin is used for dip-coating and curing. Although it can provide some protection, its UV protection and antioxidant properties are weaker than those of the composite coating solution containing nano-titanium dioxide. After 50 washes, the fabric's protective effect is even worse. In Comparative Example 21, the dip coating and curing treatment is performed first and then the surface modification treatment is performed. This order will result in the surface modifier being unable to effectively act on the fiber surface, because after the dip coating and curing are performed first, the fiber surface is covered with the coating, and the γ-aminopropyltriethoxysilane solution is difficult to directly contact and react with the fiber, which will affect the bonding between the fiber and the coating. The coating is easy to fall off after washing, thereby affecting the UV protection and antioxidant properties of the fabric. In summary, the surface modified fiber in S3 increases the adhesion to the composite coating liquid, so that the composite coating liquid in S4 can be better coated on the fiber surface to form a uniform and firm coating. The composite coating formed by nano-titanium dioxide and polyurethane resin cooperates with the surface modified fiber, and the silanized film and the composite coating work together to synergistically improve the aging resistance of the curtain fabric from multiple aspects such as blocking ultraviolet rays, preventing oxygen and moisture erosion, and improving wear resistance, so that the curtain fabric can maintain good performance during long-term use.

[0114] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a photochromic curtain fabric, characterized in that: The preparation method comprises the following steps: S1: adding spiropyran-benzoxazine to 4,4'-diaminodiphenyl ether and mixing, and then adding pyromellitic dianhydride to carry out copolymerization and imidization reaction to obtain a modified polyimide; S2: adding photochromic microcapsules, a composite dispersant, a composite antioxidant, and a composite ultraviolet absorber to the modified polyimide for two-stage melt blending to obtain a mixed material; the photochromic microcapsules include azobenzene, urea, and formaldehyde; S3 spinning the mixed material with a stretching ratio of 2-4:1 and a spinning speed of 800 m / min to obtain spun fibers; soaking the spun fibers in a 5% by mass solution of γ-aminopropyltriethoxysilane for 5 min-15 min, and drying at 80° C. to obtain surface-modified fibers; S4 solidifies the composite coating liquid on the surface-modified fiber by dip coating, and then weaves the photochromic curtain fabric.

2. The method for preparing a photochromic curtain fabric according to claim 1, wherein: The specific process of the copolymerization and imidization reaction is as follows: 90-110 parts of the 4,4'-diaminodiphenyl ether are added to a four-necked flask, nitrogen is introduced, and then 200 parts of N-methylpyrrolidone are added, stirring is started, the speed is 280 rpm, the reaction temperature is 25 ° C, and stirring is performed for 30 min-60 min to obtain a premixed solution; 5-15 parts of the spiropyran-benzoxazine are added to the premixed solution and stirring is continued for 80 min to obtain a mixed solution; 100-105 parts of the pyromellitic dianhydride are slowly added to the mixed solution, the time is controlled at 80 min, and the temperature is 5 ℃, after the addition is completed, the reaction temperature is slowly raised to 25℃, and the reaction is stirred continuously for 15h-20h to form a polyamic acid solution; the polyamic acid solution is placed in a vacuum oven, and under vacuum conditions, the temperature is raised to 100℃ at a heating rate of 3℃ / min, and maintained for 1.5h; then the temperature is raised to 150℃ at a rate of 2℃ / min, and maintained for 1.5h; then the temperature is raised to 200℃ at a rate of 2℃ / min, and maintained for 1.5h; finally, the temperature is raised to 250℃ at a rate of 1℃ / min, and maintained for 2h-3h to obtain the modified polyimide with a viscosity of 0.8dL / g-1.2dL / g.

3. The method for preparing a photochromic curtain fabric according to claim 1, wherein: The preparation method of the photochromic microcapsules is as follows: adding 15-20 parts of the urea and 30-40 parts of the formaldehyde into a three-necked flask, adjusting the pH value to 8 with a sodium hydroxide solution, and stirring the mixture in a water bath at 60° C.-70° C. for 2 hours to obtain a prepolymer solution; adding 10 parts of the azobenzene and 30 parts of deionized water and 1 part of sodium dodecylbenzenesulfonate into another container, and stirring the mixture at a speed of 7000 rpm for 25 minutes to form a uniform emulsion; slowly adding the prepolymer solution dropwise into the uniform emulsion, adjusting the pH value of the reaction system to 4 with a hydrochloric acid solution, heating the reactor to 65° C., stirring the mixture for 2 hours to 3 hours to obtain semi-finished microcapsules; after the reaction is completed, cooling the reactor to room temperature, adjusting the pH value to neutral with a sodium hydroxide solution, filtering the product, washing it with deionized water, and vacuum drying the product to obtain the photochromic microcapsules.

4. The method for preparing a photochromic curtain fabric according to claim 1, wherein: The composite dispersant comprises sodium tripolyphosphate and sodium dodecylbenzene sulfonate, and the weight ratio of the sodium tripolyphosphate to the sodium dodecylbenzene sulfonate is 1-5:

2.

5. The method for preparing a photochromic curtain fabric according to claim 1, wherein: The composite antioxidant includes antioxidant 1010 and antioxidant 626, and the weight ratio of the antioxidant 1010 to the antioxidant 626 is 3:1-5; the composite ultraviolet absorber includes Tinuvin 326 and Tinuvin 770, and the weight ratio of the Tinuvin 326 to the Tinuvin 770 is 1-3:

1.

6. The method for preparing a photochromic curtain fabric according to claim 1, wherein: The specific process of the two-stage melt blending is as follows: 100 parts of the modified polyimide, 1-5 parts of the photochromic microcapsules and 0.3-0.8 parts of the composite dispersant are added to a twin-screw extruder, the temperature of the front section of the extruder is set to 320°C, the temperature of the middle section is set to 330°C, and the temperature of the rear section is set to 340°C, and the mixture is blended at a speed of 600rpm for 10 minutes to obtain a first mixed material; 0.1-0.5 parts of the composite antioxidant and 0.1-0.5 parts of the composite ultraviolet absorber are added to the first mixed material, and the mixture is blended at a speed of 300rpm-500rpm for 5min-10min, and the mixed material is obtained after extrusion.

7. The method for preparing a photochromic curtain fabric according to claim 1, wherein: The composite coating liquid is obtained by dispersing nano-titanium dioxide in polyurethane resin, wherein the mass fraction of the nano-titanium dioxide is 1%-5%; the specific process of the dip coating and curing is: immersing the surface modified fiber in the composite coating liquid, controlling the dipping time to be 1min-5min, and curing it at 120°C for 8min-12min after taking it out.

8. A photochromic curtain fabric, characterized by: The curtain fabric is prepared by the preparation method according to any one of claims 1 to 7, and the raw materials for preparing the curtain fabric include modified polyimide, photochromic microcapsules, a composite dispersant, a composite antioxidant and a composite ultraviolet absorber; the modified polyimide includes spiropyran-benzoxazine, 4,4'-diaminodiphenyl ether and pyromellitic dianhydride, and the photochromic microcapsules include azobenzene, urea and formaldehyde.

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