Single-component photochromic polyester fiber and preparation method thereof

Abstract

The invention discloses a single-component photochromic polyester fiber and a preparation method thereof, and belongs to the technical field of high polymer materials. The photochromic material is combined with the polyester resin slices, the heat stabilizer, the light stabilizer, the ultraviolet absorption aid, the inert agent and the like, so that the photochromic material and the polyester slices are integrally formed to prepare the single-component polyester photochromic fiber. The test result of the embodiment shows that the polyester photochromic fiber prepared by the method disclosed by the invention is large in color difference value before and after illumination, has the characteristics of high photochromic sensitivity, excellent mechanical property, environmental friendliness and the like, and can be widely applied to the fields of clothes, intelligent textiles, military camouflage and the like.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a single-component photochromic polyester fiber and its preparation method. Background Technology

[0002] With rapid societal development, stimulus-responsive materials have attracted widespread attention from researchers and industry due to their unique properties and broad application prospects, becoming one of the hot research topics in recent years. Polyester materials, with their excellent physical and chemical properties, play an important role in various fields such as automotive plastics, machinery manufacturing, and textiles. In particular, photochromic materials, due to their ability to change color under light, have shown enormous application potential and market value in areas such as functional clothing and anti-counterfeiting smart textiles.

[0003] The core of photochromic materials lies in photochromic groups, which can undergo structural changes under specific wavelengths of light, resulting in color alteration. However, the synthesis and processing of polyester involve high temperatures, causing photochromic materials to decompose easily at high temperatures, exhibiting poor thermal stability, and exhibiting unsatisfactory color-changing sensitivity and durability. Therefore, patent CN105970625A utilizes the characteristics of photochromic masterbatch to prepare polyethylene composite materials, coating these materials onto spinning fibers, which to some extent reduces damage to the photochromic powder during processing. However, from a long-term perspective, materials prepared by physical adsorption or coating methods have poor wear resistance and color-changing durability, as well as insufficient mechanical strength and heat resistance. On the other hand, patent CN103556300A uses conventional fiber-grade polyester as the core layer and polyester with added phenoxynaphthoquinone photochromic materials as the sheath layer to prepare photochromic fibers. Although this method eliminates the need for high-temperature melting and extrusion of photochromic powder, the core-sheath structure of the yarn, being a bicomponent fiber, has significant limitations. Its abrasion resistance and tensile strength are still inferior to those of single-component fibers. Furthermore, the photochromic material exists in the outer layer and is thus poorly protected, reducing its weather resistance and posing risks to human health, wearing comfort, and the environment.

[0004] Furthermore, in some spirocyclic photochromic materials, the internal molecular structure undergoes ring-opening to form chromogenic groups after conventional high-temperature polyester processing. At high temperatures, the acid and oxygen ions in these chromogenic groups are easily affected by the end carboxyl groups of the polyester, leading to further oxidation and loss of color-changing ability. Additionally, the products of this process are mostly yellowish-brown or burnt yellow in color, and if photosensitivity is limited, they can also contaminate the yarn color, further diminishing the material's color-changing properties. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a single-component photochromic fiber for polyester and its preparation method, which greatly improves spinning efficiency, has environmentally friendly characteristics, and the photochromic material and carrier resin are integrally molded. Compared with bicomponent photochromic fibers, it has better wear resistance and tensile strength.

[0006] A single-component photochromic polyester fiber is obtained by melt blending polyester matrix resin, photochromic component, and stabilizing auxiliary component and then melt spinning.

[0007] The polyester matrix resin is selected from one or more combinations of polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and their copolyesters; and / or The photochromic component is an organic photochromic material selected from one or more combinations of spiropyrans, spiroxazines, benzopyrans, and naphthopyrans, and its addition amount is 0.05-5.0 wt% based on polyester matrix resin.

[0008] The stabilizing agent component comprises at least one of a heat stabilizer, a light stabilizer, and / or a UV absorber, wherein: The heat stabilizer comprises hindered phenolic antioxidants and / or phosphite antioxidants, and its total addition amount is 0.02-1.0 wt% based on the polyester matrix resin; The light stabilizer comprises a hindered amine light stabilizer, and its addition amount is 0.02-1.0 wt% based on the polyester matrix resin; The UV absorption aid is selected from one or more of benzotriazole, benzophenone, and triazine UV absorbers, and its addition amount is 0.05-3.0 wt% based on polyester matrix resin.

[0009] The single-component photochromic polyester fiber also includes an inert agent, which is melt-blended with other components in both warp and weft and then melt-spun. The inert agent component is used to suppress adverse reactions related to terminal carboxyl groups during polyester thermal processing, thereby improving the retention of the photochromic effect and / or colorfastness. The inert agent component contains carbodiimide compounds, selected from one or more combinations of monomeric carbodiimide, oligomeric carbodiimide, and polycarbodiimide. The amount of the inert agent component added, based on the polyester matrix resin, is 0.05-2.0 wt%.

[0010] Preferably, the inert agent component is added in the form of microcapsule encapsulation, wherein the core material of the microcapsule comprises polycarbodiimide and / or a solution thereof in a hydrophobic solvent, and the microcapsule has a double-shell structure with an average particle size of 0.1-20 μm and a total shell thickness of 50-2000 nm.

[0011] The outer layer of the microcapsule is a shell containing anhydride groups. During the polyester drying and premixing stage, the acid value increment of the microcapsule in the polyester is no higher than 0.02 mg KOH / g. The outer shell containing anhydride groups undergoes a ring-opening reaction in the melt spinning temperature range of 210-288℃, with a ring-opening conversion rate of 10-90%. The microcapsule undergoes thermally triggered release in the melt spinning temperature range, with a release temperature threshold of 200-280℃.

[0012] The method for preparing microencapsulated inert agents includes the following steps: S1. Polycarbodiimide is mixed and dissolved with a hydrophobic high-boiling-point solvent to obtain an oil phase; S2. Add emulsifier and / or dispersant to deionized water to obtain an aqueous phase; S3. Add the oil phase to the aqueous phase and perform shear emulsification to obtain a water-in-oil emulsion; S4. Introduce a siloxane precursor at the oil droplet interface and hydrolyze and condense it, then introduce a phenolic resin precursor and polycondense and crosslink it to form an inner inorganic-organic composite shell. S5. Introduce an anhydride-containing material onto the surface of the microcapsule with the inner shell to form the outer shell. S6. The obtained microcapsules are subjected to solid-liquid separation, washing, and vacuum drying.

[0013] The parameters in the preparation method satisfy at least one of the following conditions: In step S1, the oil phase preparation temperature is 20-40℃, and the boiling point of the hydrophobic high-boiling solvent is 200-350℃. In step S2, the total amount of emulsifier and / or dispersant is 0.1-5.0% of the mass of the aqueous phase, and the pH of the aqueous phase is 3.0-6.0; In step S3, the shearing speed is 3000-15000 r / min, the emulsification time is 5-30 min, the emulsification temperature is 15-45℃, and the average particle size of the oil droplets after emulsification is 0.1-20 μm.

[0014] In step S4, the shell-forming temperature is 30-70℃ and the shell-forming time is 1-8h; the siloxane precursor is tetraethyl orthosilicate and / or silicate precursor, the amount is 0.5-30 parts by mass per 100 parts by mass of polycarbodiimide, and the dropping time is 10-120min. The phenolic resin precursor contains resorcinol and a formaldehyde source. The amount of resorcinol is 0.1-15 parts by weight per 100 parts by weight of polycarbodiimide, and the amount of formaldehyde source is 0.1-20 parts by weight per 100 parts by weight of polycarbodiimide. The pH of the system during the siloxane hydrolysis stage is 2.5-5.5, and the pH of the system during the phenolic polycondensation stage is adjusted to 7.5-10.5.

[0015] In step S5, the anhydride-containing material is selected from anhydride silanes and / or anhydride-containing copolymers, and the amount used is 0.1-10 parts by mass per 100 parts by mass of polycarbodiimide; the introduction temperature is 20-45℃, the introduction time is 0.5-6h, and the pH of the system is 3.0-6.5; In step S6, solid-liquid separation is performed by centrifugation or filtration, and washing is performed 2-6 times; the vacuum drying temperature is 50-90℃, the time is 4-24h, the vacuum degree is -0.06 to -0.10MPa, and the water content of the microcapsules after drying is not higher than 500ppm.

[0016] A method for preparing the single-component photochromic polyester fiber includes the following steps: (a) Dry the polyester matrix resin at 100-140℃ for 2-10h so that its moisture content is not higher than 50ppm; (b) The dried polyester matrix resin is premixed with the photochromic component, the stabilizing agent component and the inert agent component; (c) The mixture is melt-spun and drawn into fibers, wherein the temperature of each melt-spinning zone is 210-288℃ and the draw ratio is 2.0-6.0 times; In particular, at least a portion of the components in steps (b) and (c) are preferably prepared into a masterbatch with the polyester carrier resin before being added. The masterbatch is prepared by twin-screw extrusion granulation, with an extruder temperature of 170-280℃ and a screw speed of 150-320r / min.

[0017] The beneficial effects of this invention are: (1) The photochromic fiber prepared by the present invention has good thermal stability and can maintain high color sensitivity even after two high-temperature processing. It can improve the photochromic fiber prepared by physical coating method, chemical grafting method and bicomponent composite spinning process in the prior art. It has the advantages of fatigue resistance, friction resistance and human wearing comfort. Moreover, the process is simple and easy to realize market popularization and promotion.

[0018] (2) Through the above technical solution, the fiber of the present invention has good weather resistance, excellent photochromic properties, and fast response time. In addition, the use of a single-component spinning process improves the mechanical and comfort properties of the yarn, while also increasing production efficiency and being friendly to the human body and the environment. The single-component photochromic polyester fiber of the present invention can be widely used in clothing, smart textiles, and military camouflage, and has safety, economic and military value.

[0019] (3) This solution addresses the problem of increased terminal carboxyl groups during conventional high-temperature processing of polyester, which adversely affects the chromogenic groups of photochromic materials and leads to a decrease in color-changing ability. It introduces polycarbodiimide as an inert agent into the single-component polyester photochromic fiber system and microencapsulates it. This isolates the inert agent from environmental moisture and oxygen during the drying and premixing stages before spinning, preventing premature failure. Simultaneously, a double-shell structure is used to achieve a synergistic effect: the microcapsule's outer layer contains anhydride groups to shield the carboxyl groups. The anhydride remains unhydrolyzed or essentially unhydrolyzed during the drying and premixing stages, thus preventing the system from exhibiting free carboxylic acidity and reducing the adverse effects on the polyester before processing. When the microcapsules enter the high-temperature zone of melt spinning (210-288℃) with the polyester, the outer anhydride groups in the melt... Under the influence of moisture or polyester terminal hydroxyl groups, ring-opening occurs, generating carboxyl or hemiester structures. This significantly increases the surface polarity of the microcapsules and enhances their wetting, dispersion, and interfacial anchoring effects in the polyester matrix. The dense, heat-resistant inner shell provides the main physical shielding before processing and, under the combined action of high-temperature zone and core material solvent vapor pressure, promotes microporous formation or physical rupture of the microcapsules, achieving thermally triggered release. This allows polycarbodiimide to capture acidic groups in situ at a high local concentration during the most intense polyester thermal degradation and hydrolysis, when a large number of terminal carboxyl groups are generated. It also weakens the adverse reaction of terminal carboxyl groups on photochromic materials. At the same time, because the release is delayed until the moment of fiber formation, it avoids premature release of polycarbodiimide, which could lead to premature chain extension reactions and problems such as excessively high polyester melt viscosity and pressure fluctuations in spinning components. Thus, while ensuring spinning stability, it improves photochromic efficiency and color fastness and enhances the overall performance of the fiber. Attached Figure Description

[0021] Figure 1 Images showing the yarn color of the single-component photochromic fiber A1 before and after light exposure in Example 2 of this invention; Figure 2 Images showing the yarn color of the single-component photochromic fiber B1 before and after light exposure in Example 3 of this invention; Figure 3 Images of the yarn color of the single-component photochromic fiber C1 before and after light exposure in Example 4 of this invention; Detailed Implementation

[0022] A photochromic fiber for single-component polyester, wherein the photochromic fiber for single-component polyester is composed of polyester resin chips, photochromic material, heat stabilizer, light stabilizer, UV absorber, and inert agent; wherein the polyester resin chips are thermoplastic fiber-forming polyester, not limited to one of conventional polyethylene terephthalate (polyester), polybutylene terephthalate (PBT), and low-melting-point polybutylene terephthalate; In one embodiment of the present invention, the single-component polyester photochromic fiber can also be formed by melt extrusion and drawing into fibers by blending photochromic masterbatch and polyester resin chips; the photochromic masterbatch is composed of photochromic material, heat stabilizer, light stabilizer, ultraviolet absorption additive and inert agent; the polyester resin chips are thermoplastic fiber-forming polyester, not limited to one of conventional polyethylene terephthalate, polybutylene terephthalate and low melting point polyester. In one embodiment of the present invention, the single-component photochromic fiber comprises, by weight, 70-95 parts polyester resin chips, 0.5-30 parts photochromic material, 0-10 parts heat stabilizer, 0-10 parts light stabilizer, 0-10 parts ultraviolet absorber and 0-10 parts inert agent. In one embodiment of the present invention, the photochromic material belongs to organic photochromic powder and is not limited to one of spiropyran, spiroxazine, benzopyran, and naphthopyran; In one embodiment of the present invention, the heat stabilizer is a combination of phosphite antioxidant and hindered phenolic antioxidant, which can protect photochromic materials under high-temperature process conditions, interfere with the photothermal aging process of end products, capture free radicals, and achieve good performance stability; it is not limited to two or more of antioxidants AO-80, antioxidant 1010, antioxidant 1098, antioxidant 1790, antioxidant 168, antioxidant 626, and antioxidant P-EPQ; In one embodiment of the present invention, the light stabilizer is not limited to one or more of light stabilizer 770 and light stabilizer 944; In one embodiment of the present invention, the ultraviolet absorption aid is not limited to one or more of ultraviolet absorber 329, ultraviolet absorber 2360, ultraviolet absorber 3460, and ultraviolet absorber 3577; In one embodiment of the present invention, the inert agent functions to inhibit the degradation effect of conventional polyester itself; and to reduce the negative reaction of the terminal carboxyl groups in conventional polyester to the photochromic material, thereby improving the color-changing efficiency and color fastness of the photochromic material; and is not limited to one or more of polycarbodiimide and monomeric carbodiimide; In one embodiment of the present invention, the inert agent is obtained by microcapsule encapsulation. The microcapsule shell contains, for example, anhydride groups, which can be triggered to transform into carboxyl groups under heating or humid conditions. These masked carboxyl groups do not exhibit free carboxylic acid during the drying and premixing stage, thereby reducing the promotion of polyester hydrolysis. In the high-temperature zone of melt spinning, a ring-opening reaction occurs to generate carboxyl groups, which improves interfacial polarity and anchoring effect, and synergistically triggers the release of polycarbodiimide to capture acidic end groups in situ.

[0023] In one embodiment of the present invention, the core material of the microcapsule is an inert agent or its solvent solution, and its inner shell is made of a heat-resistant and dense organic material, including but not limited to polyurea / polyurethane urea, or a phenolic crosslinked resin layer, to isolate water and oxygen during the premixing and drying stages and prevent the inert agent from deteriorating prematurely. Its outer shell is a carboxyl-shielding base layer, a polymer layer containing an anhydride structure, including but not limited to styrene-maleic anhydride copolymer SMA, or alkenyl ether-maleic anhydride copolymer, with an anhydride ring enriched on the outer surface.

[0024] In one embodiment of the present invention, all the materials involved are available through ordinary commercial channels; In one embodiment of the present invention, the POY yarn of the spun photochromic fiber has a breaking strength of 2.0-4.0 cN / dtex and a breaking elongation of 30-90%; the DTY yarn after processing has a breaking strength of 2.5-5.0 cN / dtex and a breaking elongation of 70-90%. Furthermore, the single-component photochromic fiber is obtained by the following preparation method: S1: Dry the thermoplastic fiber-forming polyester resin chips or powder at a temperature of 120-140℃ for 4-12 hours. The purpose is to make the moisture content of the polyester resin chips less than 50ppm. S2: Before spinning, premix the dried polyester resin chips or powder, photochromic material, heat stabilizer, UV absorber, light stabilizer and inert agent in a certain proportion. S3: Select the appropriate spinneret specifications for the assembly of the spinning components. The spinneret hole shape specifications are not limited to regular or irregular shapes, including one of the following: round holes, triangular holes, and "*" shaped holes. S4: Adjust the temperature of each zone of the spinning screw extruder, wherein the temperature of each zone of the melt spinning is 210~288℃; control the appropriate extrusion speed according to the required yarn fineness specifications, so that the yarn is ejected through the spinneret, oiled, and evenly drawn and wound on the high-speed winding machine, thereby ensuring good mechanical properties of the yarn. At the same time, turn on the side blowing system to cool the yarn; thus obtaining a single-component polyester photochromic fiber.

[0025] Furthermore, the single-component photochromic fiber can also be obtained by the following preparation method: T1: Dry the thermoplastic fiber-forming polyester resin chips or powder at a temperature of 110-140℃ for 4-12 hours. The purpose is to make the moisture content of the polyester resin chips or powder less than 50ppm. T2: Premix the dried polyester resin chips or powder, photochromic material, heat stabilizer, UV absorber, light stabilizer and inert agent in a certain proportion. T3: Adjust the temperature of each zone of the granulation screw extruder to 170-280℃ and the screw speed of the extruder to 150-320r / min, thereby obtaining photochromic masterbatch; T4: The thermoplastic fiber-forming polyester resin chips and photochromic masterbatch are dried at a temperature of 80-120℃ for 4-12 hours. T5: Repeat step S4 above to obtain a single-component polyester photochromic fiber. Example 1

[0026] This embodiment provides a method for preparing photochromic masterbatch A. The photochromic masterbatch is composed of polyester resin chips, photochromic powder, a heat stabilizer, a UV absorber, and a light stabilizer. The polyester resin chips have a melting point of 170-200℃ and a terminal carboxyl group content of 4.8 mol / t; the heat stabilizer consists of antioxidant 1790 and antioxidant 626; the UV absorber is 329; and the light stabilizer is 770. Since the heat stabilizer, UV absorber, and light stabilizer are all powders, the low-melting-point PBT is pre-crushed with liquid nitrogen. 81 parts of low-melting-point PBT powder, 5 parts of naphthopyran-based photochromic pigment, 5.5 parts of antioxidant 1790, 6 parts of antioxidant 626, 1.5 parts of UV absorber 329, and 1.0 part of light stabilizer 944 are mixed in a high-temperature... The powder is mixed evenly in a mixer. The powder (hereinafter referred to as "material") is dried in a 120°C forced-air drying oven for 4 hours to reduce its moisture content to less than 30 ppm. The dried material is fed into a twin-screw extruder with the temperatures of each zone set to 170°C, 215°C, 215°C, 215°C, 210°C, and 210°C, and the rotation speed is 300 r / min. The molten material is extruded into strips through the die outlet of the twin-screw extruder, cooled in a water tank, drawn into a pelletizer, and cut into flat cylindrical photochromic masterbatch A with a 100-particle weight of 1.5 g. Example 2

[0027] This embodiment provides a method for indirectly preparing single-component photochromic fibers. The photochromic fibers are formed by melt extrusion of photochromic masterbatch and polyester resin chips using a single-screw melt spinning machine; the photochromic masterbatch is photochromic masterbatch A from Example 1; the polyester resin chips and photochromic masterbatch A are placed in a forced-air drying oven and dried for 4 hours at a drying temperature of 120°C, so that the moisture content of both is less than 30 ppm; the temperatures of each spinning zone are adjusted to 220°C, 225°C, 225°C, 225°C, 225°C, 225°C, 225°C, 225°C; the spinneret orifice type... Select a round hole type for the spinning assembly installation; mix 8 parts of photochromic masterbatch and 92 parts of polyester resin chips (melting point 170-200℃) evenly and feed them into the feed port of the melt spinning machine; set a side blowing air to cool the fiber at a wind speed of 0.35m / s, a humidity of 75%RH, and a temperature of 26℃, and then apply oil to the nozzle, wind and stretch it with a high-speed winding machine to obtain single-component photochromic polyester fiber A1 with a fineness specification of 150D / 48f and a winding machine speed of 2800r / min.

[0028] The mechanical properties of the yarn were tested using a YG029 fully automatic single yarn tensile testing machine, with a draft length of 200 mm and a stretching speed of 500 mm / min. The breaking strength of the POY yarn was 2.5 cN / dtex, and the breaking elongation was 72%. The breaking strength of the DTY yarn was 2.8 cN / dtex, and the breaking elongation was 83%. A color card was obtained by winding the above-mentioned photochromic fiber A1 into a card with a winding width of 20 mm and a winding layer of 4 layers. Figure 1 Color photographs of fiber A1 before and after light exposure; The color difference meter was used to measure the Lab value of the color chart before and after illumination. The instrument calculated the color change level of A1 based on its internal algorithm. The detailed results are shown in Table 1. Example 3

[0029] This embodiment provides a method for directly preparing single-component photochromic fibers. The photochromic fibers are composed of polyester resin chips, photochromic powder, a heat stabilizer, a UV absorber, and a light stabilizer. The polyester resin chips have a melting point of 170-200℃. The heat stabilizer consists of antioxidant 1790 and antioxidant 626. The UV absorber is 329. The light stabilizer is 944. The polyester resin chips are dried in a 120℃ oven for 4 hours until the moisture content of the chips is less than 30 ppm. The temperatures of each spinning zone were adjusted to 220℃, 225℃, 225℃, 225℃, 225℃, 225℃, 225℃, 225℃; a round-hole spinneret was selected for the spinning assembly installation; 83.8 parts of dried polyester resin chips, 4 parts of photochromic powder, 4.2 parts of antioxidant 1790, 4.5 parts of antioxidant 626, 2 parts of UV absorber 329, and 1.5 parts of light stabilizer 944 were mixed evenly and fed into the feed port of the melt spinning machine; a side-blowing fan was set to cool the fiber at a wind speed of 0.35 m / s, a humidity of 75% RH, and a temperature of 26℃; after oiling with an oil nozzle, winding and drawing on a high-speed winding machine, a single-component photochromic polyester fiber B1 was obtained with a fineness specification of 150D / 48f and a winding machine speed of 2800. The mechanical properties of the yarn were tested using a YG029 fully automatic single yarn tensile testing machine, with a draft length of 200 mm and a stretching speed of 500 mm / min. The breaking strength of the POY yarn was 2.4 cN / dtex, and the breaking elongation was 75%. The breaking strength of the DTY yarn was 2.6 cN / dtex, and the breaking elongation was 81%. A yarn color card winding machine was used to wind the above-mentioned photochromic fiber B1 into a color card with a winding width of 20 mm and a winding layer of 4 layers. The Lab value of the color card before and after light exposure was detected using an X-Rite color difference meter. The instrument calculated the color change grade of B1 according to its internal algorithm. The detailed results are shown in Table 1. Example 4

[0030] This embodiment provides a method for directly preparing single-component photochromic conventional polyester fibers. The photochromic fiber is composed of polyester resin chips, photochromic powder, a heat stabilizer, a UV absorber, a light stabilizer, and an inert agent. The polyester resin chips have a melting point of 250-260℃. The heat stabilizer consists of antioxidant 1790 and antioxidant 626. The UV absorber is 329. The light stabilizer is 770. The inert agent is polycarbodiimide, which disrupts the effect of the terminal carboxyl groups of the polyester on the photochromic powder during high-temperature processing, protecting the color-changing groups. The polyester resin chips were dried in a 120℃ oven for 4 hours to reduce the moisture content to less than 30ppm. The temperatures of each spinning zone were adjusted to 220℃, 225℃, 225℃, 225℃, 225℃, 225℃, 225℃, 225℃. A round-hole spinneret was selected for the spinning assembly. 83.3 parts of dried polyester resin chips, 4 parts of photochromic powder, 4.2 parts of antioxidant 1790, 4.5 parts of antioxidant 626, and 2 parts of UV absorber were then added. After uniformly mixing agent 329, 1.5 parts of light stabilizer 770, and 0.5 parts of polycarbodiimide, the mixture is fed into the feed inlet of a melt spinning machine. A side-blowing fan is used to cool the fiber at a speed of 0.35 m / s, a humidity of 75% RH, and a temperature of 26°C. The fiber is then oiled, wound, and drawn using a high-speed winding machine to obtain single-component photochromic polyester fiber C1 with a fineness specification of 150D / 48f and a winding machine speed of 2800 r / min. YG02 is used. A Type 9 fully automatic single yarn strength testing machine was used to test the mechanical properties of the yarn. The draft length was set to 200 mm and the stretching speed to 500 mm / min. The breaking strength of the POY yarn was 2.3 cN / dtex, and the breaking elongation was 71%. The breaking strength of the DTY yarn was 2.5 cN / dtex, and the breaking elongation was 80%. A yarn color card winding machine was used to wind the above-mentioned photochromic fiber C1 into color cards with a winding width of 20 mm and 4 winding layers to obtain color cards. Figure 3 The images show the color of fiber C1 before and after light exposure. The Lab values ​​of the color chart before and after light exposure were measured using an X-Rite colorimeter. The instrument calculated the color change grade of C1 based on its internal algorithm. Detailed results are shown in Table 1. Example 5

[0031] This embodiment provides a method for preparing a microcapsule-encapsulated polycarbodiimide inert agent. Oil phase A is prepared by mixing and dissolving 10 parts by weight of polycarbodiimide and 20 parts by weight of dibenzyl benzoate, and stirring until a homogeneous oil phase is formed. Aqueous phase is prepared by mixing 200 parts by weight of deionized water, 2 parts by weight of polyvinyl alcohol (PVA), and 0.5 parts by weight of sodium dodecyl sulfate, and stirring until dissolved, then adjusting the pH to 4.0. The oil phase is slowly added to the aqueous phase, and emulsified in a high-speed shear emulsifier to form a water-in-oil emulsion. Subsequently, tetraethyl orthosilicate (TEOS) is added dropwise. 6 parts by mass were added and the reaction continued for 60 min to complete the hydrolysis and initial deposition of silica sol. Then, 1.2 parts by mass of resorcinol and 2.0 parts by mass of 37% formaldehyde solution were added to the system, and the pH was adjusted to 8.5 with ammonia. The reaction was continued at 50℃ for 4 h to form a dense and heat-resistant inorganic-organic composite shell layer in situ at the oil droplet interface. After the inner shell layer was formed, the system was cooled to 30℃ and 0.8 parts by mass of 3-(triethoxysilyl)propylsuccinic anhydride was added and the pH was adjusted to 4.5. The reaction was continued with stirring for 2 h to allow the silane end of the anhydride to condense and anchor with the surface of the inner shell layer and to introduce an anhydride-type carboxyl-masking structure on the outer surface. After the reaction was completed, the mixture was centrifuged and dried with deionized water and ethanol under vacuum to obtain microencapsulated inert agent powder.

[0032] Under the same process conditions as in Example 4, a single-component photochromic conventional polyester fiber was prepared by microencapsulating inert agent powder. The raw material ratio used was 83.3 parts polyester resin chips, 4 parts photochromic powder, 4.2 parts antioxidant 1790, 4.5 parts antioxidant 626, 2 parts UV absorption aid 329, 1.5 parts light stabilizer 770, and 1 part microencapsulated polycarbodiimide powder. The single-component photochromic polyester fiber D1 was prepared by the same method, and the color change grade was detected and calculated.

[0033] Comparative Example 1 The difference from Example 5 is that when preparing the microcapsule-coated polycarbodiimide inert agent, no acid anhydride was introduced to the outer layer to mask the carboxyl structure, that is, 3-(triethoxysilyl)propylsuccinic anhydride was not added for coating. The remaining steps are the same as in Example 5. Finally, a single-component photochromic polyester fiber E1 was obtained, and the color change level was detected and calculated.

[0034] Comparison of Examples: As shown in Table 1, the color difference values ​​and color change grades of fibers A1 and B1 indicate that the photochromic material retains its photosensitivity after two high-temperature processing stages, achieving a color change grade of 1 after light exposure, with a color change damage rate of less than 12%. The single-component photochromic yarn directly prepared from conventional polyester, although exhibiting a color difference value lower than that of low-melting-point PBT after light exposure, still achieves a photosensitivity rate greater than 70%, reaching a color change grade of 1. Therefore, it can be concluded that the single-component photochromic fiber obtained by the method described in this invention exhibits a large color difference value before and after light exposure, and a significant color change effect.

[0035] Table 1. Lab values ​​and color change grades of single-component photochromic fibers A1, B1, and C1 before and after illumination.

[0036] Fiber A1 in Example 2 was obtained using a masterbatch method combined with a low-melting-point matrix. This resulted in more uniform dispersion of the photochromic material and minimal heat damage, leading to the highest color difference value, representing the upper limit of the system's performance. Fiber B1 in Example 3 used a dispersible method, with a color difference value slightly lower than fiber A1. Fiber C1 in Example 4 used conventional polyester, with a processing temperature higher than the low-melting-point polyester used in A1 / B1. Although an inert agent was added to C1, high-temperature shearing and the erosion of numerous terminal carboxyl groups still led to a significant decline in color-changing performance, with the color difference value dropping to 27.45. This indicates that in a conventional polyester high-temperature processing system, simple physical mixing alone cannot effectively protect the photochromic material. Comparing fiber C1 from Example 4, fiber D1 from Example 5, and fiber E1 from Comparative Example 1, although all three used high-melting-point conventional polyester chips, the color difference values ​​were D1 (32.68) > E1 (30.05) > C1 (27.45). This fully demonstrates that microencapsulating the inert agent (E1) can effectively reduce losses before high-temperature processing; and on this basis, introducing a shell containing anhydride groups (D1) and using the carboxyl groups generated in situ at high temperature to reinforce the interface anchoring and synergistic release of the inert agent can eliminate the damage of the terminal carboxyl groups to the photochromic material to the greatest extent, so that conventional polyester fibers can also obtain excellent color-changing properties close to those of low-melting-point polyester (B1).

Claims

1. A single-component photochromic polyester fiber, characterized in that, It is obtained by melt blending polyester matrix resin, photochromic component and stabilizing agent component and then melt spinning.

2. The single-component photochromic polyester fiber as described in claim 1, characterized in that, The polyester matrix resin is selected from one or more combinations of polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and their copolyesters; and / or The photochromic component is an organic photochromic material selected from one or more combinations of spiropyrans, spiroxazines, benzopyrans, and naphthopyrans, and its addition amount is 0.05-5.0 wt% based on polyester matrix resin.

3. The single-component photochromic polyester fiber as described in claim 1 or 2, characterized in that, The stabilizing agent component comprises at least one of a heat stabilizer, a light stabilizer, and / or a UV absorber, wherein: The heat stabilizer comprises hindered phenolic antioxidants and / or phosphite antioxidants, and its total addition amount is 0.02-1.0 wt% based on the polyester matrix resin; The light stabilizer comprises a hindered amine light stabilizer, and its addition amount is 0.02-1.0 wt% based on the polyester matrix resin; The UV absorption aid is selected from one or more of benzotriazole, benzophenone, and triazine UV absorbers, and its addition amount is 0.05-3.0 wt% based on polyester matrix resin.

4. The single-component photochromic polyester fiber as described in any one of claims 1 to 3, characterized in that, The single-component photochromic polyester fiber also includes an inert agent, which is melt-blended with other components in both warp and weft directions and then melt-spun. The inert agent component is used to suppress adverse reactions related to terminal carboxyl groups during polyester thermal processing, thereby improving the retention of the photochromic effect and / or colorfastness. The inert agent component contains carbodiimide compounds, selected from one or more combinations of monomeric carbodiimides, oligomeric carbodiimides, and polycarbodiimides. The amount of the inert agent component added, based on the polyester matrix resin, is 0.05-2.0 wt%. Preferably, the inert agent component is added in the form of microcapsule encapsulation, wherein the core material of the microcapsule comprises polycarbodiimide and / or a solution thereof in a hydrophobic solvent, and the microcapsule has a double-shell structure with an average particle size of 0.1-20 μm and a total shell thickness of 50-2000 nm.

5. The single-component photochromic polyester fiber as described in claim 4, characterized in that, The outer layer of the microcapsule is a shell containing anhydride groups. During the polyester drying and premixing stage, the acid value increase of the microcapsule in the polyester is no higher than 0.02 mg KOH / g. The outer shell containing anhydride groups undergoes a ring-opening reaction in the melt spinning temperature range of 210-288℃, with a ring-opening conversion rate of 10-90%. The microcapsules are thermally triggered to release within the melt spinning temperature range, with a release temperature threshold of 200-280℃.

6. The single-component photochromic polyester fiber as described in claim 5, characterized in that, The preparation method of microcapsules includes the following steps: S1. Polycarbodiimide is mixed and dissolved with a hydrophobic high-boiling-point solvent to obtain an oil phase; S2. Add emulsifier and / or dispersant to deionized water to obtain an aqueous phase; S3. Add the oil phase to the aqueous phase and perform shear emulsification to obtain a water-in-oil emulsion; S4. Introduce a siloxane precursor at the oil droplet interface and hydrolyze and condense it, then introduce a phenolic resin precursor and polycondense and crosslink it to form an inner inorganic-organic composite shell. S5. Introduce an anhydride-containing material onto the surface of the microcapsule with the inner shell to form the outer shell. S6. The obtained microcapsules are subjected to solid-liquid separation, washing, and vacuum drying.

7. The single-component photochromic polyester fiber as described in claim 6, characterized in that, In step S1, the oil phase preparation temperature is 20-40℃, and the boiling point of the hydrophobic high-boiling solvent is 200-350℃; in step S2, the total amount of emulsifier and / or dispersant is 0.1-5.0% of the mass of the aqueous phase, and the pH of the aqueous phase is 3.0-6.0; in step S3, the shearing speed is 3000-15000 r / min, the emulsification time is 5-30 min, the emulsification temperature is 15-45℃, and the average particle size of the oil droplets after emulsification is 0.1-20 μm.

8. The method as described in claim 6 or 7, characterized in that, In step S4, the shell-forming temperature is 30-70℃, and the shell-forming time is 1-8 hours. The siloxane precursor is tetraethyl orthosilicate and / or a silicate ester precursor, with a dosage of 0.5-30 parts by weight per 100 parts by weight of polycarbodiimide, and a dropping time of 10-120 minutes. The phenolic resin precursor contains resorcinol and a formaldehyde source, with the resorcinol dosage being 0.1-15 parts by weight per 100 parts by weight of polycarbodiimide, and the formaldehyde source dosage being 0.1-20 parts by weight per 100 parts by weight of polycarbodiimide. The pH of the system during the siloxane hydrolysis stage is 2.5-5.5, and the pH of the system during the phenolic polycondensation stage is adjusted to 7.5-10.

5.

9. The method according to any one of claims 6 to 8, characterized in that, In step S5, the anhydride-containing material is selected from anhydride silanes and / or anhydride-containing copolymers, and the amount used is 0.1-10 parts by mass per 100 parts by mass of polycarbodiimide; the introduction temperature is 20-45℃, the introduction time is 0.5-6h, and the pH of the system is 3.0-6.5; in step S6, solid-liquid separation is performed by centrifugation or filtration, and washing is performed 2-6 times; the vacuum drying temperature is 50-90℃, the time is 4-24h, the vacuum degree is -0.06 to -0.10MPa, and the water content of the microcapsules after drying is not higher than 500ppm.

10. A method for preparing the single-component photochromic polyester fiber as described in any one of claims 1 to 5, characterized in that, Includes the following steps: (a) Dry the polyester matrix resin at 100-140℃ for 2-10h so that its moisture content is not higher than 50ppm; (b) The dried polyester matrix resin is premixed with the photochromic component, the stabilizing agent component and the inert agent component; (c) The mixture is melt-spun and drawn into fibers, wherein the temperature of each melt spinning zone is 210-288℃ and the draw ratio is 2.0-6.0 times; In particular, at least a portion of the components in steps (b) and (c) are preferably prepared into masterbatch with polyester carrier resin before being added. The masterbatch is prepared by twin-screw extrusion granulation, with an extruder temperature of 170-280℃ and a screw speed of 150-320r / min.

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