Photochromic window shade fabric and method of making same

Abstract

The present application relates to the technical field of textile materials, in particular to a photochromic curtain fabric and a preparation method thereof. The present application overcomes the problems of unstable discoloration performance and poor durability of the curtain fabric. The present application synthesizes modified polyimide through copolymerization and imidization reaction; the photochromic microcapsules, composite dispersing agent and other components are two-stage melt blended with the modified polyimide to obtain a mixture containing polyimide; then the surface of the polyimide fiber is modified through spinning forming and surface modification; finally, the photochromic curtain fabric is obtained through dip coating, curing and weaving processes. The mechanical properties and discoloration stability of the fabric are enhanced by modifying the polyimide; the aging resistance of the fabric is improved by the synergistic effect of the other components, thereby meeting the functional and durable requirements of the textile material.

Description

Technical Field

[0001] This invention relates to the field of textile materials technology, specifically to a photochromic curtain fabric and its preparation method. Background Technology

[0002] Since its discovery in the early 20th century, photochromic materials such as spiropyran and azobenzene have been continuously developed, and their reversible color-changing properties under light have been widely used in optical information storage, anti-counterfeiting, and many other fields. In the textile industry, color-changing fabrics are fabrics that can change color due to changes in external conditions such as light, temperature, humidity, and stress. Photochromic materials endow fabrics with the ability to adjust color and light transmittance according to light, enhancing the decorative properties of curtain fabrics.

[0003] Currently, polyimide fabrics, such as clothing and non-woven fabrics, have expanded their applications to a certain extent in fields such as labor protection, fire fighting, and bulletproof vests. However, due to factors such as the limited color options available for polyimide, its application scope remains relatively narrow. With the increasing market demand for polyimide fabrics in diverse colors, by modifying polyimide, such as introducing photochromic groups or combining it with photochromic materials, it is possible to prepare polyimide fabrics with photochromic properties for use as curtain fabrics.

[0004] However, during the preparation of 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. This can lead to a reduction in the photochromic effect of the photochromic polyimide fabric. Furthermore, during processing and use, photochromic polyimide fibers 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] To address this, a photochromic curtain fabric and its preparation method are proposed. Summary of the Invention

[0006] The purpose of this invention is to design a photochromic curtain fabric and its preparation method. This invention prepares modified polyimide through copolymerization and imidization reactions, then adds photochromic microcapsules, a composite dispersant, a composite antioxidant, and a composite ultraviolet absorber for two-stage melt blending to obtain a mixture. This mixture is then spun and modified to obtain surface-modified fibers, and finally, through dip coating curing and weaving, the photochromic curtain fabric is obtained. The modified polyimide, photochromic microcapsules, and composite dispersant synthesized in this invention synergistically improve the mechanical properties and color-changing stability of the curtain fabric; the composite antioxidant, composite ultraviolet absorber, and the two-stage melt blending process improve the fabric's resistance to photo-oxidation; and the spinning, surface modification, and dip coating curing processes synergistically improve the fabric's aging resistance.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] This invention provides a method for preparing a photochromic curtain fabric, the method comprising the following steps:

[0009] S1. Spiropyran-benzoxazine was added to 4,4'-diaminodiphenyl ether and mixed. Then, pyromellitic dianhydride was added to carry out copolymerization and imidization reaction to obtain modified polyimide.

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

[0011] S3 spins the mixture with a draw ratio of 2-4:1 and a spinning speed of 800 m / min to obtain spun fibers; the spun fibers are then immersed in a 5% (w / w) γ-aminopropyltriethoxysilane solution for 5 min-15 min and dried at 80℃ to obtain surface-modified fibers.

[0012] S4 applies a composite coating liquid to the surface-modified fibers via dip coating, and then weaves the resulting photochromic curtain fabric.

[0013] Preferably, the specific process of copolymerization and imidization reaction, by weight, is as follows: 90-110 parts of 4,4'-diaminodiphenyl ether are added to a four-necked flask, nitrogen gas is introduced, followed by 200 parts of N-methylpyrrolidone. Stirring is started at 280 rpm, the reaction temperature is 25°C, and stirring is carried out for 30-60 minutes to obtain a premixed solution; 5-15 parts of spiropyran-benzoxazine are added to the premixed solution, and stirring is continued for 80 minutes to obtain a mixed solution; 100-105 parts of pyromellitic dianhydride are slowly added to the mixed solution, controlling the time at 80 minutes and the temperature at 5°C. After the feed is completed, the reaction temperature is slowly raised to 25℃ and stirred continuously for 15-20 hours to form a polyamic acid solution. The polyamic acid solution is placed in a vacuum oven and heated to 100℃ at a rate of 3℃ / min under vacuum conditions, and held for 1.5 hours. Then, the temperature is raised to 150℃ at a rate of 2℃ / min and held for 1.5 hours. Next, the temperature is raised to 200℃ at a rate of 2℃ / min and held for 1.5 hours. Finally, the temperature is raised to 250℃ at a rate of 1℃ / min and held for 2-3 hours to obtain modified polyimide with a viscosity of 0.8 dL / g-1.2 dL / g.

[0014] Preferably, the preparation method of photochromic microcapsules by weight 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℃-70℃ for 2 hours 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 7000 rpm for 25 minutes to form a homogeneous emulsion; the prepolymer solution is slowly added dropwise to the homogeneous emulsion, the pH value of the reaction system is adjusted to 4 with hydrochloric acid solution, the reaction vessel is heated to 65℃, and the mixture is stirred for 2-3 hours to obtain a semi-finished microcapsule; after the reaction is completed, the reaction vessel 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 includes sodium tripolyphosphate and sodium dodecylbenzene sulfonate, wherein 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, with the weight ratio of antioxidant 1010 and antioxidant 626 being 3:1-5; the composite ultraviolet absorber includes Tinuvin 326 and Tinuvin 770, with the weight ratio of Tinuvin 326 and Tinuvin 770 being 1-3:1.

[0017] Preferably, the specific process of two-stage melt blending, by weight, is as follows: 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 extruder front section temperature is set to 320°C, the middle section temperature to 330°C, and the rear section temperature to 340°C. The mixture is blended at 600 rpm for 10 minutes to obtain the first mixture. 0.1-0.5 parts of composite antioxidant and 0.1-0.5 parts of composite ultraviolet absorber are added to the first mixture, and the mixture is blended at 300-500 rpm for 5-10 minutes. After extrusion, the final mixture is obtained.

[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 as follows: the surface-modified fiber is immersed in the composite coating liquid, the dip coating time is controlled to be 1min-5min, and after being taken out, it is cured at 120℃ for 8min-12min.

[0019] Another aspect of the present invention provides a photochromic curtain fabric, wherein the raw materials for preparing the curtain fabric include modified polyimide, photochromic microcapsules, composite dispersant, composite antioxidant and 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 beneficial effects of the present invention are as follows:

[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 forms a stable imide structure in the polymer. This structure has high strength and toughness. An appropriate amount of spiropyran-benzoxazine can further enhance the intermolecular forces through intermolecular interactions, thereby improving the mechanical properties of the curtain fabric.

[0022] 2. Modified polyimide, as the matrix material, provides support and protection for the photochromic microcapsules, enabling them to be uniformly dispersed in the system. Simultaneously, the photochromic properties of the modified polyimide itself complement the properties of the photochromic microcapsules, enhancing the color-changing effect of the curtain fabric. The azobenzene within the photochromic microcapsules undergoes a photochromic reaction under light, and microencapsulation protects the azobenzene from external environmental influences, improving its light stability and lifespan. The composite dispersant ensures uniform dispersion of the photochromic microcapsules in the modified polyimide, preventing agglomeration and improving the bonding between the microcapsules and the modified polyimide, thus enhancing compatibility. The combined effect of these three factors improves the stability of the color-changing performance of the curtain fabric.

[0023] 3. The first stage of melt blending ensures thorough and uniform mixing of the modified polyimide, photochromic microcapsules, and composite dispersant, providing a homogeneous matrix for subsequent processes. The second stage of melt blending involves adding composite antioxidants and composite UV absorbers, followed by further blending to ensure uniform dispersion of both within the system. This two-stage melt blending method guarantees the uniform distribution of various additives within the modified polyimide, allowing them to work synergistically and effectively improve the photo-oxidation resistance of the curtain fabric. The composite UV absorber first absorbs most of the ultraviolet light, 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 these two agents improves the photo-oxidation resistance of the curtain fabric from both UV shielding and oxidation reaction inhibition perspectives, extending the fabric's durability.

[0024] 4. The surface-modified fibers in S3 increase adhesion to the composite coating liquid, allowing the composite coating liquid in S4 to be better coated on the fiber surface, forming a uniform and firm coating. The composite coating formed by nano-titanium dioxide and polyurethane resin works synergistically with the surface-modified fibers. The silanized film and the composite coating work together to improve the aging resistance of the curtain fabric in multiple ways, such as blocking ultraviolet rays, preventing oxygen and moisture erosion, and improving abrasion resistance, so that the curtain fabric can maintain good performance during long-term use. Attached Figure Description

[0025] Figure 1 The UVA shielding efficiency diagrams for Examples 18 and 18-21 of this invention before and after water washing are shown. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] For details, please refer to [link / reference]. Figure 1 This invention provides a photochromic curtain fabric and its preparation method, the technical solution of which is as follows:

[0028] Example 1

[0029] 15 parts urea and 30 parts formaldehyde were added to a three-necked flask, and the pH was adjusted to 8 with sodium hydroxide solution. The mixture was stirred in a water bath at 60°C for 2 hours to obtain a prepolymer solution. In another container, 10 parts azobenzene and 30 parts deionized water were added, along with 1 part sodium dodecylbenzenesulfonate. The mixture was stirred at 7000 rpm for 25 minutes to form a homogeneous emulsion. The prepolymer solution was slowly added dropwise to the homogeneous emulsion, and the pH of the reaction system was adjusted to 4 with hydrochloric acid solution. The reaction vessel was heated to 65°C and stirred for 2 hours to obtain semi-finished microcapsules. After the reaction was completed, the reaction vessel was cooled to room temperature, and the pH 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 dodecylbenzenesulfonate, with a weight ratio of 1:2; the composite antioxidant includes antioxidant 1010 and antioxidant 626, with a weight ratio of 3:1; the composite ultraviolet absorber includes Tinuvin 326 and Tinuvin 770, with a weight ratio of 1:1.

[0031] Preparation of photochromic curtain fabric:

[0032] S1. Add 90 parts of 4,4'-diaminodiphenyl ether to a four-necked flask, purge with nitrogen, then add 200 parts of N-methylpyrrolidone, start stirring at 280 rpm, maintain the reaction temperature at 25°C, and stir for 30 min to obtain a premixed solution; add 5 parts of spiropyran-benzoxazine to the premixed solution, and continue stirring for 80 min to obtain a mixed solution; slowly add 100 parts of pyromellitic dianhydride to the mixed solution, controlling the time at 80 min and the temperature at 5°C. After the addition is complete, slowly reduce the reaction temperature. The temperature was raised to 25°C and stirred continuously for 15 hours to form a polyamic acid solution. The polyamic acid solution was placed in a vacuum oven and heated to 100°C at a rate of 3°C / min under vacuum conditions, and held for 1.5 hours. Then, the temperature was raised to 150°C at a rate of 2°C / min and held for 1.5 hours. Next, the temperature was raised to 200°C at a rate of 2°C / min and held for 1.5 hours. Finally, the temperature was raised to 250°C at a rate of 1°C / min and held for 2 hours to obtain modified polyimide with a viscosity of 0.8 dL / g.

[0033] S2 adds 100 parts of modified polyimide, 1 part of photochromic microcapsules, and 0.3 parts of composite dispersant to a twin-screw extruder. The extruder front section temperature is set to 320℃, the middle section temperature to 330℃, and the rear section temperature to 340℃. The mixture is stirred at 600 rpm for 10 minutes to obtain the first mixture. Then, 0.1 parts of composite antioxidant and 0.1 parts of composite ultraviolet absorber are added to the first mixture, and the mixture is stirred at 300 rpm for 5 minutes. After extrusion, a final mixture is obtained.

[0034] S3 spins the mixture at a draw ratio of 2:1 and a spinning speed of 800 m / min to obtain spun fibers; the spun fibers are then immersed in a 5% (w / w) γ-aminopropyltriethoxysilane solution for 5 min and dried at 80°C to obtain surface-modified fibers.

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

[0036] Examples 2-5

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

[0038] Table 1 Parameters and Conditions for Examples 1-5

[0039]

[0040] Comparative Example 1

[0041] Referring to the parameters and conditions in Example 1, the difference is that spiropyran-benzoxazine is not added during the copolymerization and imidization reactions.

[0042] Comparative Example 2

[0043] Referring to the parameters and conditions in Example 1, the difference is that only the copolymerization reaction is carried out.

[0044] Comparative Example 3

[0045] The parameters and conditions are the same as in Example 1, except that only the imidization reaction is carried out.

[0046] Comparative Example 4

[0047] Referring to the parameters and conditions in Example 1, the difference is that commercially available polyimide is directly added to participate in the subsequent reaction.

[0048] Experiment Example 1: Mechanical Properties and Color Change Properties Test

[0049] The mechanical properties of Examples 1-5 and Comparative Examples 1-4 were tested according to GB / T 3923.1-2013 standard; the curtain fabrics of Examples 1-5 and Comparative Examples 1-4 were irradiated with ultraviolet light to observe whether photochromism occurred; the results are shown in Table 2.

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

[0051] Example Elongation at break / % Fracture stress / MPa Color-changing 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 exhibited good mechanical and color-changing properties. In Comparative Example 1, the absence of spiropyran-benzoxazine altered the structure and properties of the modified polyimide. While polyimide itself possesses high strength, the lack of spiropyran-benzoxazine altered the interactions between molecular chains, resulting in a decrease in the mechanical properties of the final fabric. Spiropyran-benzoxazine is a compound with photochromic properties; its absence directly affects the fabric's color-changing performance. The fabric failed to achieve the desired photochromic effect. The results of Comparative Example 2 show that copolymerization can link different monomers together to form copolymers, but imidization is crucial for the structural formation and performance improvement of polyimide. If only copolymerization is carried out, the molecular chain structure of the polymer will be 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 can introduce some photochromic groups, imidization helps to form a more stable conjugated structure, which has an important impact on photochromic performance. Without imidization, the stability and binding of photochromic microcapsules and other components in subsequent processing will be worse, affecting the color-changing performance of the fabric. In Comparative Example 3, without a copolymerization reaction to link the different monomers, there is no basic polymer chain available 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 groups or structures are introduced through copolymerization, imidization alone cannot provide a basis for photochromism in the fabric. The color-changing performance is only provided by photochromic capsules, resulting in poor photochromic properties. In Comparative Example 4, the directly added polyimide has not undergone copolymerization with spiropyran-benzoxazine and imidization modification. Its molecular structure and properties are relatively simple, which will affect the mechanical properties of the curtain fabric in subsequent processing. Furthermore, the directly added polyimide does not possess photochromic properties, leading to poor final color-changing performance. In summary, the addition of spiropyran-benzoxazine to the copolymerization system of 4,4'-diaminodiphenyl ether and pyromellitic dianhydride introduces the spiropyran-benzoxazine structure into the polyimide molecular chain through copolymerization, giving the polyimide photochromic properties. The imidization reaction forms a stable imide structure in the polymer, which has high strength and toughness. An appropriate amount of spiropyran-benzoxazine can further enhance the intermolecular forces through intermolecular interactions, thereby improving the mechanical properties of the curtain fabric.

[0053] Examples 6-10

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

[0055] Table 3. Parameters and conditions for Examples 3 and 6-10

[0056]

[0057] Comparative Example 5

[0058] Referring to the parameters and conditions in Example 3, the difference is that only polyimide is added, without modifying it.

[0059] Comparative Example 6

[0060] Referring to the parameters and conditions in Example 3, the difference is that only azobenzene is added, and no phenolic resin is used for coating.

[0061] Comparative Example 7

[0062] The parameters and conditions are the same as in Example 3, except that photochromic microcapsules are not added.

[0063] Comparative Example 8

[0064] Referring to the parameters and conditions in Example 3, the difference is that only sodium tripolyphosphate is added as a dispersant.

[0065] Comparative Example 9

[0066] Referring to the parameters and conditions in Example 3, the difference is that only sodium dodecylbenzenesulfonate is added as a dispersant.

[0067] Comparative Example 10

[0068] The parameters and conditions are the same as in Example 3, except that no composite dispersant is added.

[0069] Experiment Example 2: Color-Changing Performance Test

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

[0071] Table 4. Color-changing performance tests of Examples 3, 6-10, and Comparative Examples 5-10

[0072] Example Sunlight duration (4 hours) Sunlight duration (12 hours) Sunlight duration (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] Table 4 shows that the color-changing performance of all embodiments is relatively stable. In Comparative Example 5, only polyimide was added without modification. The unmodified polyimide lacks the spiropyran-benzoxazine structure, which leads to reduced light sensitivity of the fabric, slower color-changing speed, and easy degradation of color-changing performance during long-term use. In Comparative Example 6, only azobenzene was added without phenolic resin coating. Azobenzene is easily affected by factors such as oxygen and moisture and becomes ineffective, resulting in a decrease in the photochromic performance of the fabric, with problems such as indistinct 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 substances in the modified polyimide alone cannot achieve photochromic function in the long term. In Comparative Examples 8-9, only sodium tripolyphosphate or sodium dodecylbenzenesulfonate was added as a dispersant, which resulted in poor dispersion and uneven distribution of photochromic microcapsules in the system, thus making the photochromic performance of the fabric unstable. In Comparative Example 10, without the addition of a composite dispersant, the photochromic microcapsules were difficult to disperse uniformly in the modified polyimide, resulting in agglomeration and severely affecting the photochromic performance. This led to poor color-changing properties in the fabric and further reduced the color-changing stability of the curtain fabric. In summary, the modified polyimide, as the matrix material, provides support and protection for the photochromic microcapsules, enabling them to disperse uniformly in the system. Simultaneously, the photochromic properties of the modified polyimide itself complement the properties of the photochromic microcapsules, improving the color-changing effect of the curtain fabric. The azobenzene in the photochromic microcapsules undergoes a photochromic reaction under light, and microencapsulation protects the azobenzene from external environmental influences, improving its light stability and lifespan. The composite dispersant ensures uniform dispersion of the photochromic microcapsules in the modified polyimide, prevents agglomeration, and improves the bonding between the microcapsules and the modified polyimide, enhancing compatibility. The combined effect of these three factors improves the stability of the color-changing 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 for Examples 8 and 11-15

[0077]

[0078] Comparative Example 11

[0079] Referring to the parameters and conditions in Example 8, the difference is that only antioxidant 1010 is added as an antioxidant.

[0080] Comparative Example 12

[0081] Referring to the parameters and conditions in Example 8, the difference is that only antioxidant 626 is added as an antioxidant.

[0082] Comparative Example 13

[0083] The parameters and conditions are the same as in Example 8, except that no composite antioxidant is added.

[0084] Comparative Example 14

[0085] Referring to the parameters and conditions in Example 8, the difference is that only Tinuvin 326 is added as an ultraviolet absorber.

[0086] Comparative Example 15

[0087] Referring to the parameters and conditions in Example 8, the difference is that only Tinuvin 770 is added as an ultraviolet absorber.

[0088] Comparative Example 16

[0089] The parameters and conditions are the same as in Example 8, except that no composite ultraviolet absorber is added.

[0090] Comparative Example 17

[0091] Referring to the parameters and conditions in Example 8, the difference lies in the fact that photochromic microcapsules, composite dispersant, composite antioxidant and composite ultraviolet absorber are added together and melt-blended to obtain a mixture.

[0092] Experimental Example 3: Anti-photooxidation performance

[0093] The UV protection performance of Examples 8, 11-15, and Comparative Examples 11-17 was tested according to GB / T 18830-2009 standard. Quantitative analysis was performed using spectrophotometry based on the DPPH analysis method. The antioxidant performance of Examples 8, 11-15, and Comparative Examples 11-17 was tested by measuring the free radical scavenging rate. The results are shown in Table 6.

[0094] Table 6. Anti-photooxidation performance tests of Examples 8, 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 exhibit strong resistance to photo-oxidation. In Comparative Examples 11-12, only antioxidant 1010 or antioxidant 626 were added as antioxidants. A single antioxidant cannot fully exert the synergistic effect of a composite antioxidant, and therefore cannot comprehensively and effectively inhibit oxidation reactions. The effects on inhibiting free radical generation and terminating chain reactions are diminished, leading to a decrease in the fabric's antioxidant performance. In Comparative Example 13, without the addition of a composite antioxidant, the fabric is easily affected by factors such as oxygen in the air and light during use, resulting in oxidation reactions and a significant reduction in antioxidant performance, thus shortening the fabric's lifespan. In Comparative Examples 14-15, only Tinuvin 326 or Tinuvin 770 were added as UV absorbers. The range of UV wavelengths protected is limited, resulting in insufficient protection against certain wavelengths of UV radiation, thereby reducing the fabric's UV protection performance. In Comparative Example 16, without the addition of the composite UV absorber, UV rays cause photodegradation and photooxidation reactions in the polymer materials of the fabric, leading to a decline in fabric performance. At this point, the fabric cannot effectively block UV rays, exhibiting extremely poor UV protection and becoming susceptible to UV damage, resulting in fading and aging. In Comparative Example 17, this method affects the uniformity of dispersion of each component in the modified polyimide, causing interference between components and poor dispersion, thus impacting the fabric's UV protection and antioxidant properties. In summary, the first stage of melt blending ensures thorough and uniform mixing of the modified polyimide, photochromic microcapsules, and composite dispersant, providing a uniform matrix for subsequent processes. The second stage of melt blending, involving the addition of the composite antioxidant and composite UV absorber, ensures uniform dispersion of both in the system. This two-stage melt blending method guarantees the uniform distribution of various additives in the modified polyimide, allowing them to work synergistically and effectively improving the photooxidation resistance of the curtain fabric. The composite UV absorber first absorbs most of the UV rays, reducing the oxidation reaction caused by UV rays; the composite antioxidant captures and decomposes the remaining free radicals and peroxides, further inhibiting the oxidation reaction; the two work synergistically to improve the anti-photooxidation performance of the curtain fabric from both UV shielding and oxidation reaction inhibition aspects, thus 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 for Examples 13 and 16-20

[0100]

[0101] Comparative Example 18

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

[0103] Comparative Example 19

[0104] Referring to the parameters and conditions in Example 13, the difference is that no dip coating and curing treatment is performed in S4.

[0105] Comparative Example 20

[0106] Referring to the parameters and conditions in Example 13, the difference is that the resin used for impregnation and curing in S4 is polyurethane resin.

[0107] Comparative Example 21

[0108] Referring to the parameters and conditions in Example 13, the difference is that dip coating and curing treatment is performed first, followed by surface modification treatment.

[0109] Experiment Example 4: Aging Resistance Test

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

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

[0112]

[0113] From Table 8 and Figure 1It can be observed that the aging resistance of the examples is better. Comparative Example 18 shows that treatment with γ-aminopropyltriethoxysilane solution can improve fiber surface properties and enhance the adhesion between the fiber and subsequent coatings. Without surface modification treatment, the composite coating solution will not adhere firmly to the fiber surface, and after 50 washes, the coating is prone to peeling off, resulting in the loss of components with UV protection and antioxidant properties, such as nano-titanium dioxide, thus 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 properties, and the polyurethane resin can also protect the fiber from oxidation to a certain extent, without 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 the UV protection and antioxidant properties will significantly decrease. In Comparative Example 20, only polyurethane resin is used for dip-coating and curing. Although it provides some protection, compared with the composite coating solution containing nano-titanium dioxide, its UV protection and antioxidant properties are weaker, and the protective effect of the fabric will be even worse after 50 washes. In Comparative Example 21, the order of dip-coating curing followed by surface modification treatment prevents the surface modifier from effectively adhering to the fiber surface. Because the fiber surface is covered by the coating after dip-coating curing, the γ-aminopropyltriethoxysilane solution has difficulty directly contacting and reacting with the fiber. This affects the adhesion between the fiber and the coating, making the coating prone to peeling off after washing, thus impacting the fabric's UV protection and antioxidant properties. In summary, the surface-modified fibers in S3 increase adhesion to the composite coating liquid, allowing the composite coating liquid in S4 to better coat the fiber surface, forming a uniform and robust coating. The composite coating formed by nano-titanium dioxide and polyurethane resin works synergistically with the surface-modified fibers. The silanized film and the composite coating work together to synergistically improve the aging resistance of the curtain fabric from multiple aspects, including blocking UV rays, preventing oxygen and moisture erosion, and improving abrasion resistance, enabling the curtain fabric to maintain good performance during long-term use.

[0114] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which 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, by weight, includes the following steps: S1. Spiropyran-benzoxazine was added to 4,4'-diaminodiphenyl ether and mixed. Then, pyromellitic dianhydride was added to carry out copolymerization and imidization reaction to obtain modified polyimide. S2 adds photochromic microcapsules, a composite dispersant, a composite antioxidant, and a composite ultraviolet absorber to the modified polyimide and performs a two-stage melt blending to obtain a mixture. The photochromic microcapsules include azobenzene, urea, and formaldehyde. The composite dispersant includes sodium tripolyphosphate and sodium dodecylbenzene sulfonate, with a weight ratio of 1-5:

2. The composite antioxidant includes antioxidant 1010 and antioxidant 626, with a weight ratio of 3:1-5. The composite ultraviolet absorber includes Tinuvin 326 and Tinuvin 770, with a weight ratio of 1-3:

1. 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 extruder front section temperature is set to 320°C, the middle section temperature to 330°C, and the rear section temperature to 340°C. The mixture is blended at 600 rpm for 10 minutes to obtain a first mixture. 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 mixture. The mixture is blended at 300-500 rpm for 5-10 minutes. After extrusion, the final mixture is obtained. S3. The mixture is spun into fibers with a draw ratio of 2-4:1 and a spinning speed of 800m / min to obtain spun fibers; the spun fibers are then immersed in a 5% (w / w) γ-aminopropyltriethoxysilane solution for 5-15 minutes and dried at 80°C to obtain surface-modified fibers. S4 The composite coating liquid is cured on the surface-modified fibers by dip coating, and then the photochromic curtain fabric is woven; 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%.

2. The method for preparing a photochromic curtain fabric according to claim 1, characterized in that: 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 gas is introduced, followed by 200 parts of N-methylpyrrolidone. Stirring is started at 280 rpm, the reaction temperature is 25°C, and stirring is carried out for 30-60 minutes to obtain a premixed solution. 5-15 parts of the spiropyran-benzoxazine are added to the premixed solution, and stirring is continued for 80 minutes to obtain a mixed solution. 100-105 parts of the pyromellitic dianhydride are slowly added to the mixed solution, controlling the time at 80 minutes and the temperature at 5°C. After completion, the reaction temperature is slowly raised to 25°C, and the reaction is continuously stirred for 15-20 hours 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 held for 1.5 hours. Then, the temperature is raised to 150°C at a rate of 2°C / min and held for 1.5 hours. Then, the temperature is raised to 200°C at a rate of 2°C / min and held for 1.5 hours. Finally, the temperature is raised to 250°C at a rate of 1°C / min and held for 2-3 hours to obtain the modified polyimide with a viscosity of 0.8 dL / g-1.2 dL / g.

3. The method for preparing a photochromic curtain fabric according to claim 1, characterized in that: The preparation method of the photochromic microcapsules is as follows: 15-20 parts of the urea and 30-40 parts of the 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℃-70℃ for 2 hours to obtain a prepolymer solution; in another container, 10 parts of the azobenzene and 30 parts of deionized water are added, and 1 part of sodium dodecylbenzenesulfonate is added, and the mixture is stirred at 7000 rpm for 25 minutes to form a homogeneous emulsion; the prepolymer solution is slowly added dropwise to the homogeneous emulsion, the pH value of the reaction system is adjusted to 4 with hydrochloric acid solution, the reaction vessel is heated to 65℃, and the mixture is stirred for 2-3 hours to obtain semi-finished microcapsules; after the reaction is completed, the reaction vessel 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 the photochromic microcapsules.

4. The method for preparing a photochromic curtain fabric according to claim 1, characterized in that: The specific process of dip coating and curing is as follows: the surface-modified fiber is immersed in the composite coating liquid, the dip coating time is controlled to be 1 min-5 min, and after being taken out, it is cured at 120℃ for 8 min-12 min.

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

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