Photochromic fibers and textile products and woven / knitted fabrics made therefrom

Abstract

This invention provides a photochromic fiber that can achieve high quality in terms of vivid color development and a soft texture without hardening when exposed to ultraviolet light. [Solution] A photochromic fiber comprising two or more polymers, wherein at least a portion of the fiber cross-section is composed of a nonpolar polymer containing a photochromic dye, and the composite ratio of the polymers is 50% or less.

Description

[Technical Field]

[0001] This invention relates to fibers containing photochromic properties and textile products and woven or knitted fabrics made therefrom. [Background technology]

[0002] Synthetic fibers possess excellent mechanical properties and dimensional stability, making them widely used in both clothing and non-clothing applications. However, with the increasing sophistication of people's lives, there is a growing demand for fibers that possess advanced functions not found in conventional synthetic fibers and that appeal to people's senses.

[0003] One direction in the research and technological development of these synthetic fibers is to enhance visibility and functionality by modifying pigments within the fibers and controlling their dispersion state. In recent years, progress has been made in developing fibers that reversibly change color depending on the external environment by forming fibers from resins containing specific pigments.

[0004] Photochromic fibers are a type of fiber that enables reversible color changes. By incorporating dyes that react to light irradiation, such as ultraviolet light, they exhibit photochromic functionality, allowing for reversible color changes upon light exposure.

[0005] The principle of photochromic function is that the chemical structure of photochromic dyes undergoes rearrangement of bonds upon irradiation with ultraviolet light, causing a change in color. Patent Document 1 states that photochromic dyes undergo thermal degradation when exposed to high temperatures during melt mixing with matrix polymers or during molding, leading to the deactivation of the photochromic function, i.e., a decrease in color development. Therefore, various technologies have been disclosed to improve color development upon ultraviolet irradiation in textile applications where melt molding is required.

[0006] Patent Document 2 proposes a photochromic fiber in which microcapsules containing a photochromic dye and a styrene-based oligomer are fabricated, and these microcapsules are kneaded into a thermoplastic resin and molded. In this fiber, the photochromic dye can be protected by microcapsules, thereby improving light resistance and enabling the development of excellent coloration.

[0007] Patent Document 3 proposes a mixed fiber of photochromic fibers and polyamide fibers, in which photochromic dyes are directly kneaded into a low-melting-point polymer to form fibers. In this fiber, by using a low-melting-point polymer as the matrix polymer, melt kneading and melt spinning are possible at temperatures below 200°C, which is the typical heat resistance temperature of the dye, enabling the realization of excellent color development in the mixed fiber.

[0008] Patent Document 4 proposes a photochromic core-sheath composite fiber in which a microcapsule coated with a photochromic dye using epoxy resin or the like, or a polymer in which the dye alone is kneaded into a low-melting-point polymer, is used as the core component, and a thermoplastic resin that does not contain the photochromic dye is used as the sheath component. In this composite fiber, as with Patent Documents 1 and 2, light resistance is improved by protecting the photochromic dye with microcapsules, and the deactivation of the photochromic function due to thermal degradation is suppressed by lowering the melting temperature by using a low-melting-point polymer. Furthermore, by using a thermoplastic resin that does not contain the dye as the sheath component, it is possible to manufacture a photochromic fiber that also has excellent basic properties such as durability and gloss of the fiber surface. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2008-38288 [Patent Document 2] Japanese Patent Publication No. 2006-233351 [Patent Document 3] Japanese Patent Publication No. 2015-81388 [Patent Document 4] Japanese Patent Application Publication No. 4-202811 [Overview of the project] [Problems that the invention aims to solve]

[0010] As described in Patent Document 2, coating and protecting photochromic dyes with microcapsules can suppress the deactivation of the photochromic function due to thermal degradation of the dye during melting, kneading, and molding, and can achieve high color development when irradiated with ultraviolet light. However, in Patent Document 2, it is necessary to coat the dye with microcapsules, and the microcapsules containing the dye naturally have an average particle size of about 5 to 20 μm, which is a coarse particle size compared to the diameter of general-purpose fibers. For this reason, when spinning general-purpose fibers, molding conditions are restricted and it is limited to thick fibers such as monofilaments. In addition, uneven color development occurs due to the non-uniform dispersion of microcapsules, making it difficult to apply to clothing applications where fine diameter, soft texture, and uniform color development are important, and it has been used in some material applications such as embroidery thread and toy hair.

[0011] Patent Document 3 describes how using a low-melting-point polymer as a matrix allows the melting temperature to be set below 200°C, which is the heat resistance temperature of the dye. As a result, the deactivation of the photochromic function due to heat can be suppressed. However, low-melting-point polymer fibers are prone to fusion on the fiber surface during heat treatment in higher-order processing, which can result in a hard texture. In particular, when developing for clothing, processing at high temperatures is often performed during weaving and knitting, as well as during the finishing of fabrics. This often leads to glossiness due to melting and crushing of the fibers, as well as effects due to fusion between fibers, which can result in deterioration of texture and a decrease in quality.

[0012] Patent Document 4 focuses on arranging a thermoplastic resin that does not contain the dye in the sheath component, which may solve the problems of Patent Document 2. However, in order to improve the color development when irradiated with ultraviolet light, it is necessary to set a high composite ratio of low-melting-point polymer containing photochromic dye. In Patent Document 4, as in Patent Document 3, the low-melting-point polymer softens due to the heat of weaving or finishing processes, causing the fibers to deform easily, resulting in a dense fabric without voids between fibers, or causing the fiber bundles to become partially flat, resulting in a glare. Therefore, in order to develop the material for clothing applications where a soft touch is particularly important, there were problems such as limitations on the processing temperature during higher-order processing and the materials that could be combined.

[0013] As described above, research and technological development are being conducted on photochromic fibers that exhibit high color development when irradiated with ultraviolet light. However, there is no technology that can achieve both high color development and a soft texture. Therefore, there has been a need for a photochromic fiber that can achieve both vivid color development without uneven coloring and a soft touch without hardening of the texture, and that can be used in clothing applications with high quality. [Means for solving the problem]

[0014] The object of the present invention is achieved by the following means: (1) A photochromic fiber comprising two or more polymers, wherein at least a portion of the fiber cross-section is composed of a nonpolar polymer containing a photochromic dye, and the composite ratio of the polymers is 50% or less. (2) The photochromic fiber according to (1), comprising a nonpolar polymer containing a photochromic dye and the other polymer, wherein the sum of the interface lengths is 1 to 100 μm. (3) The photochromic fiber according to (1) or (2), characterized in that the variation in the interface length between the nonpolar polymer containing the photochromic dye and the other polymer in the fiber cross-section is 0 to 30.0%. (4) A textile product that contains at least a portion of the photochromic fiber described in any of (1) to (3) above. (5) A woven or knitted fabric which contains at least a portion of the photochromic fibers described in any of (1) to (3) above, and has a surface exposure rate of 20% or more. [Effects of the Invention]

[0015] This technology provides photochromic fibers that can achieve high-quality vivid color development and a soft texture without hardening when exposed to ultraviolet light. [Brief explanation of the drawing]

[0016] [Figure 1] Figures 1(a) to (d) are schematic diagrams showing an example of the cross-sectional structure of the photochromic fiber of the present invention. [Figure 2] Figure 2 is a cross-sectional view of a die used to illustrate the method for producing photochromic fibers according to the present invention. [Modes for carrying out the invention]

[0017] The present invention will be described in detail below, along with preferred embodiments.

[0018] This invention relates to photochromic fibers and woven or knitted fabrics made therefrom. The photochromic fiber of the present invention is a composite fiber composed of two or more polymers, wherein at least a portion of the fiber's cross-section is composed of a nonpolar polymer containing a photochromic dye, and the composite ratio of the polymers is 50% or less. Of the two or more polymers, the polymer other than the nonpolar polymer is referred to as the other polymer.

[0019] In this invention, a photochromic fiber refers to a composite fiber that has a photochromic function, in which its color reversibly changes upon irradiation with ultraviolet light.

[0020] In this context, a photochromic dye refers to a dye in which, upon irradiation with light such as ultraviolet light, a rearrangement of bonds within the chemical structure occurs without a change in molecular weight, causing a change in the wavelength of light absorbed and thus a change in color. The reverse reaction occurs when the light is blocked, causing the color to return to its original state. The photochromic function of such a dye is the ability to reversibly change color depending on the presence or absence of irradiation with light such as ultraviolet light.

[0021] In order to achieve the objective of this invention, which is to obtain vivid color development when irradiated with ultraviolet light, the inventors have diligently studied the matter and found that the reactivity of the dye and polymer at high temperatures is important for suppressing the deactivation of the photochromic function, and this invention is based on the discovery of this phenomenon. That is, conventionally, it has been thought that photochromic dyes with low heat resistance change composition when excessive heat is applied, causing them to deactivate their photochromic function, so techniques have been developed to protect the dye from heat during melt mixing or molding by coating it with a styrene oligomer, or to lower the melting temperature itself by directly kneading the dye into a low-melting-point polymer.

[0022] However, our inventors have found that polymers without polar terms, i.e., nonpolar polymers, do not react with the chemical structure of photochromic dyes whose intramolecular bonds have been rearranged by heating. Therefore, even when exposed to temperatures above the heat resistance temperature of the photochromic dye for a long period of time, the photochromic function is not deactivated and the color development does not decrease.

[0023] Therefore, in the present invention, at least a portion of the fiber must be composed of a nonpolar polymer containing a photochromic dye.

[0024] In this context, nonpolar polymers refer to polymers with a Hansen solubility parameter (HSP value) of 20.0 MPa. 1 / 2 The following, and the polarity term of the HSP value, are 5.0 MPa. 1 / 2 This refers to the following polymers.

[0025] The Hansen solubility parameter (HSP value) referred to here is (solubility parameter) 2 =(dispersion term) 2 +(Polarity term) 2 +(hydrogen bond term) 2 As shown by the formula, it is a physical property value defined by the square root of the cohesive energy density, and is a parameter that takes into account the polarity of the polymer.

[0026] Within this range, the polarity term of the polymer becomes smaller, which has less effect on the rearrangement of the bonds of the photochromic dye molecules. As a result, the deactivation of the photochromic function is suppressed, and the color development does not decrease, making it a desirable range.

[0027] Furthermore, the HSP value of the nonpolar polymer is 18.0 MPa. 1 / 2 The following, and the polarity term of the HSP value, are 3.0 MPa. 1 / 2 The following is a preferred range in the present invention. Within this range, even when a nonpolar polymer containing a photochromic dye is heated at high temperature for a long time, it does not react with the chemical structure of the dye, and vivid color development when exposed to ultraviolet light can be expected even after melt kneading or molding, and is therefore a preferred range. Specifically, nonpolar polymers include olefin polymers such as polyethylene and polypropylene, and polystyrene polymers. In the present invention, in order to achieve a soft texture without hardening of the fabric when made into a cloth, it is preferable to suppress the densification of fibers due to heat treatment during higher-order processing, and in order to achieve both vivid color development and a soft texture, it is important to make the composite ratio (area ratio) of the nonpolar polymer containing the photochromic dye in the fiber cross-section 50% or less.

[0028] As described above, the presence of a non-polar polymer is important for achieving vivid color development. In general, however, non-polar polymers are prone to softening when heated due to their molecular chain structure. Therefore, conjugated fibers containing a non-polar polymer tend to deform due to softening of the non-polar polymer during heat treatment, and become densified to fill inter-fiber voids, which eventually results in a hard texture. Accordingly, in the present invention, by setting the composite ratio of the non-polar polymer in the conjugate fiber to 50% or less, the proportion of the polymer that softens during heat treatment is suppressed to a small amount, making it possible to achieve a soft tactile sensation without texture hardening. On the other hand, from the perspective of achieving both compatibility with color developability, it is preferable to incorporate a large amount of a polymer containing a photochromic dye. In the present invention, by incorporating the dye into the non-polar polymer, deterioration of the dye is significantly suppressed, so that vivid color developability can be achieved even if the composite ratio of the non-polar polymer is reduced. Based on this idea, the present invention achieves both vivid color developability and a soft tactile sensation without texture hardening. The present invention provides a conjugate fiber composed of two or more types of polymers, wherein at least a part of the fiber cross-section is constituted by a non-polar polymer containing a photochromic dye, and it is required that the composite ratio of the polymer is 50% or less.

[0029] The composite ratio of the non-polar polymer containing a photochromic dye in the present invention is determined as described below (see also Fig. 1).

[0030] After embedding the photochromic fiber of the present invention in an embedding agent such as epoxy resin, the cross-section is photographed at a magnification that allows the cross-section to be identified using a VHX-2000 digital microscope manufactured by KEYENCE, or the like. At this time, using a Contec black light UV-SVGNC365-01 (wavelength: 365 nm, light output: 690 mW, high mode), the cross-section is irradiated with ultraviolet light for 1 minute, the discolored portion is defined as the photochromic dye-containing layer, the non-discolored portion is defined as the non-dye-containing layer, and the junction between these portions is defined as the interface. Next, with respect to the cross-section of a single fiber present in the captured image, the area (μm 2 ) of the photochromic dye-containing layer (discolored portion) relative to the area of the entire fiber (μm 2The value obtained by dividing by () and multiplying by 100 is taken as the composite ratio (%) of the nonpolar polymer containing the photochromic dye in one fiber. The above measurement is performed for 10 fibers to calculate the composite ratio of each fiber, and the value obtained by rounding the arithmetic mean of these values ​​to the first decimal place is the composite ratio (%) of the nonpolar polymer containing the photochromic dye of the present invention.

[0031] Furthermore, in the present invention, the smaller the composite ratio of the nonpolar polymer containing the photochromic dye, the less the polymer softens during heat treatment in higher-order processing, resulting in a stronger fiber structure and making it suitable for photochromic fibers with a soft texture without hardening.

[0032] From the above perspective, it is preferable that the composite ratio of the nonpolar polymer containing the photochromic dye is 35% or less. Within this range, deformation of the fibers due to heat treatment during higher-order processing is minimal, and a soft touch can be achieved even in applications that come into direct contact with the skin, such as clothing, and therefore it can be cited as a preferred range.

[0033] Furthermore, a more preferable range in the present invention is when the composite ratio of nonpolar polymers is 25% or less. Within this range, even when the heat treatment temperature during advanced processing becomes high due to the blending of polyurethane fibers, etc., hardening of the texture is suppressed. This greatly expands the range of materials that can be combined and the process conditions in advanced processing, enabling a variety of material designs and advanced processing, and can therefore be cited as a more preferable range in the present invention.

[0034] However, from the perspective of improving texture, lowering the composite ratio is preferable, but this results in a photochromic dye content that is too low, leading to poor color development when exposed to ultraviolet light. Therefore, the lower limit of the composite ratio of the nonpolar polymer containing the photochromic dye in the composite fiber of the present invention is 5%, and above this level, the photochromic function can be sufficiently confirmed.

[0035] From the viewpoint of further improving the color development performance of the photochromic fiber of the present invention when irradiated with ultraviolet light, it is preferable that the sum of the interface lengths between the nonpolar polymer containing the photochromic dye and the other polymer in the fiber cross-section is 100 μm or less.

[0036] The sum of interface lengths referred to here is calculated as follows (see also Figure 1).

[0037] After embedding the photochromic fiber of the present invention in an embedding agent such as epoxy resin, the cross-section is photographed at a magnification that allows for cross-sectional identification using a Keyence VHX-2000 digital microscope or similar device. At this time, a Contec UV-SVGNC365-01 black light (wavelength 365 nm, light output 690 mW high mode) is used to irradiate the cross-section with ultraviolet light for 1 minute. The discolored portion is designated as the photochromic dye-containing layer, the undiscolored portion as the non-containing layer, and the junction between them as the interface. Next, for the cross-section of one fiber present in the captured image, an arbitrary position at the interface between the photochromic dye-containing layer and the non-containing layer is set as the measurement start point using image analysis software. The length from the measurement start point along the interface in a series of images and back to the measurement start point is measured, and this value is defined as the interface length (μm). All interface lengths in the cross-section are measured in the same manner, and their sum is defined as the total interface length (μm) of one fiber. The above measurements were performed on 10 fibers to calculate the sum of the interface lengths of each fiber. The sum of the interface lengths (μm) of the present invention is obtained by rounding the arithmetic mean of these sums to the first decimal place.

[0038] In other words, the inventors' studies have shown that at the interface between a nonpolar polymer containing a photochromic dye and another polymer, the polar portions of the dye and the other polymer come into contact, and therefore react when heated during melt spinning or higher-order processing.

[0039] Furthermore, it was found that this phenomenon causes a partial deactivation of the photochromic function, which is one of the reasons for the decrease in color development.

[0040] As a result of diligent research into suppressing this phenomenon, we found that if the sum of the interface lengths of the two polymers in the fiber cross-section is kept below 100 μm, the polarity contact between the dye and the other polymer is reduced, and the decrease in color development caused by the deactivation of the photochromic function at the interface becomes minor. This allowed us to achieve vivid color development even after advanced processing.

[0041] Taking this point further, if the sum of the interface lengths between the nonpolar polymer containing the photochromic dye and the other polymer is 80 μm or less, the amount of contact between the dye and the polar portion of the other polymer at the polymer interface will be reduced. Therefore, even when the heat treatment temperature during advanced processing becomes high due to blending with polyurethane fibers, etc., the decrease in color development is suppressed. As a result, the range of materials that can be combined and the process conditions in advanced processing are greatly expanded, enabling a variety of material designs and advanced processing, which can be cited as a more preferred range of the present invention.

[0042] Furthermore, although the reaction between the dye and the polar portion of the polymer proceeds at the polymer interface even when exposed to ultraviolet light, if the total interface length is kept below 65 μm, the decrease in color development due to repeated ultraviolet light irradiation can be suppressed, and the durability of the color development can be improved. This can be listed as a particularly preferred range of the present invention.

[0043] From the standpoint of suppressing the decrease in color development due to post-treatment, it is preferable to reduce the total interface length. However, if the content of the nonpolar polymer containing the photochromic dye becomes too low, the color development during UV irradiation will be low regardless of whether post-treatment is performed or not. Therefore, the lower limit of the total interface length between the nonpolar polymer containing the photochromic dye and the other polymer in the photochromic fiber of the present invention is 1 μm, and if it is greater than this, the photochromic function can be clearly seen.

[0044] The cross-sectional structure of the photochromic fiber of the present invention is preferably a shape in which the entire circumference of a nonpolar polymer A containing a photochromic dye is covered with the other polymer B, as illustrated in Figures 1(a) to (d), that is, a shape in which the nonpolar polymer containing the photochromic dye is not exposed on the surface. With such a cross-sectional structure, surface fusion between fibers due to heat treatment during higher-order processing can be suppressed, a soft feel without hardening of texture can be achieved, and basic properties such as durability such as lightfastness, washfastness, and frictionfastness, as well as gloss, can be excellent. Specifically, core-sheath type, sea-island type, and multilayer laminated type are preferred. Furthermore, from the viewpoint of vivid color development when irradiated with ultraviolet light, the core-sheath type, which minimizes the total interface length, is a more preferred range.

[0045] In the photochromic fiber of the present invention, it is preferable that the variation in the interface length between the polymer containing the photochromic dye and the other polymer in the fiber cross-section is 30.0% or less.

[0046] The interface length variation (%) referred to here is a value calculated based on the measurement results of the sum of interface lengths, using the formula: Interface Length Variation (Interface Length CV%) = (Standard Deviation of Sum of Interface Lengths / Mean of Sum of Interface Lengths). The value is rounded to two decimal places.

[0047] If the interface length variation in the fiber cross-section of a photochromic fiber is 30.0% or less, then there will be no variation in the interface length between fibers, i.e., no variation in the composite ratio of the nonpolar polymer containing the photochromic dye. This will result in a fiber without uneven color development between fibers when irradiated with ultraviolet light, which can be listed as a preferred range of the present invention.

[0048] Furthermore, a more preferable range in the present invention is when the interface length variation is 20.0% or less. Within this range, even when the fibers are dyed and only the other polymer that does not contain the photochromic dye is dyed, the ratio of the photochromic dye to the dye in the fiber cross-section remains constant, resulting in high-quality fibers without uneven dyeing or uneven color development during UV irradiation. Moreover, a particularly preferable range in the present invention is when the interface length variation is 10.0% or less. Within this range, even when the composite ratio of the nonpolar polymer containing the photochromic dye is low, vivid color development without uneven color development can be achieved, increasing the freedom of material design.

[0049] From this perspective, a smaller variation in interface length is preferable, but the practical lower limit of the variation in interface length in the present invention is 0.1% or more.

[0050] In the photochromic fiber of the present invention, it is preferable that the yarn variability U%(h) is 2.0% or less.

[0051] The term "yarn thickness variation U%(h)" used herein refers to the thickness variation of the yarn in the longitudinal direction of the fiber, measured using a Zerbeger Worcester UT-4 yarn thickness tester with a measurement speed of 200 m / min, a measurement time of 2.5 minutes, and a twister of 6000 rpm.

[0052] A yarn variability U%(h) of 2.0% or less is considered a preferable range because it ensures a constant composite ratio of nonpolar polymers containing photochromic dyes along the fiber axis, resulting in fibers without color variations during UV irradiation. Furthermore, a yarn variability U%(h) of 1.5% or less is considered an even more preferable range because it not only improves the uniformity of color development during UV irradiation but also yields high-quality fibers without color variations. However, the practical lower limit of yarn variability U%(h) is 0.1% or higher.

[0053] In accordance with the objectives of the present invention, it is preferable that the fiber diameter of the photochromic fiber be 40 μm or less, as this range is used to enhance the effect.

[0054] The fiber diameter referred to here is determined as follows:

[0055] In this invention, photochromic fibers are embedded in an embedding agent such as epoxy resin, and then their cross-sections are photographed at a magnification that allows for cross-sectional identification using a Keyence VHX-2000 digital microscope or similar device. The area of ​​fibers randomly selected from each image is measured, and the diameter, calculated as a perfect circle, is measured in μm to one decimal place. This process is performed for 10 filaments, and the simple numerical average of the results is calculated, rounded to the first decimal place, to obtain the fiber diameter (μm). If a hollow portion exists in the fiber cross-section perpendicular to the fiber axis, the area of ​​the hollow portion is also added to the fiber area.

[0056] In the photochromic fibers of the present invention, from the viewpoint of making the texture more flexible, the fiber diameter is preferably 40 μm or less. Furthermore, by making the fiber diameter 30 μm or less, the bending rigidity of the single fiber is reduced, making it more suitable for use as a textile for clothing such as outerwear. Furthermore, by making the fiber diameter 20 μm or less, the bending rigidity of the single fiber is further reduced, resulting in a softer feel, making it particularly suitable for general clothing applications such as innerwear, shirts, and blouses that come into contact with the skin. However, if the fiber is too thin, the bending recovery is reduced, which not only impairs the resilience required for general clothing applications, but also, when a product utilizing the photochromic fibers of the present invention is irradiated with ultraviolet light, the efficiency of irradiation to the photochromic dye is physically reduced, which may reduce the visible color development. In the present invention, a fiber diameter of 1 μm or more is the practical lower limit.

[0057] Furthermore, from a similar perspective, in the photochromic fiber of the present invention, the single fiber fineness is preferably 15.0 dtex or less, more preferably 10.0 dtex or less when applied to clothing, and particularly preferably 4.0 dtex or less when applied to clothing such as innerwear or shirts that come into direct contact with the skin.

[0058] In the photochromic fiber of the present invention, it is preferable that the melting point of the other polymer that does not contain a photochromic dye is 180°C or higher.

[0059] The melting point referred to here is the value measured by the following method. Specifically, a chip-shaped polymer was dried in a vacuum dryer to a moisture content of 200 ppm or less, and approximately 5 mg was weighed out. A differential scanning calorimeter (DSC) Q2000 manufactured by TA Instruments was used to measure the melting point from 0°C to 300°C at a heating rate of 16°C / min, and then held at 300°C for 5 minutes. The melting point was calculated from the melting peak observed during the heating process. Three measurements were taken for each sample, and the average value was taken as the melting point. In the case where multiple melting peaks were observed, the top melting peak on the highest temperature side was taken as the melting point.

[0060] If the melting point of the other polymer, which does not contain photochromic dyes, is 180°C or higher, it is possible to achieve a soft texture without hardening of the feel by preventing surface fusion of fibers during heat treatment in advanced processing, and this is considered a preferred range. Furthermore, if the melting point of the other polymer is 200°C or higher, surface fusion of fibers is suppressed even when the heat treatment temperature during advanced processing becomes high due to blending with polyurethane fibers, etc., so the range of materials that can be combined and the process conditions in advanced processing are greatly expanded, enabling various material designs and advanced processing, and this can be considered a more preferred range of the present invention.

[0061] On the other hand, if the melting point of the other polymer that does not contain a photochromic dye is made excessively high, it becomes necessary to set a high spinning temperature during melt spinning, which can easily lead to thermal decomposition of the dye and deactivation of the photochromic function at the composite interface, resulting in a decrease in color development. Therefore, the melting point of the other polymer is preferably 330°C or lower, more preferably 290°C or lower, even more preferably 250°C or lower, and particularly preferably 230°C or lower. Preferred specific examples of the other polymer will be described later.

[0062] In the photochromic fiber of the present invention, a dye concentration of 0.1 to 40.0% by weight in the nonpolar polymer containing the photochromic dye is a preferred range because the color development upon UV irradiation can be visually confirmed, and the color return is good when light is blocked after UV irradiation. Furthermore, a dye concentration of 0.5 to 10.0% by weight is a more preferred range because visibility and aesthetics are enhanced, and color development suitable for general clothing applications is obtained. Moreover, a dye concentration of 1.0 to 5.0% by weight maximizes the above effects, and is therefore a particularly preferred range.

[0063] In the photochromic fiber of the present invention, from the viewpoint of suppressing the degradation of the photochromic dye due to ultraviolet irradiation, it is preferable to include at least one of an antioxidant, a hindered amine-based stabilizer (HALS), and an ultraviolet absorber in the nonpolar polymer containing the photochromic dye. In particular, HALS can efficiently capture peroxide radicals generated in the polymer and suppress the decomposition of the photochromic dye by photo-oxidation, thereby improving color durability, and can therefore be cited as a more preferred form in the present invention. Furthermore, since HALS also has excellent thermal stability, it is effective even in high-temperature environments during melt spinning and advanced processing, and can therefore be suitably used in the present invention. The amounts of antioxidants, hindered amine-based stabilizers, and ultraviolet absorbers added are preferably 0.1 to 50 parts by weight each per 1 part by weight of the photochromic dye. Within this range, it is preferable because it is possible to suppress the deterioration of photochromic function while also preventing a deterioration of the mechanical properties of the fibers. Furthermore, if the amount added is 1 to 30 parts by weight, it is possible to achieve both antioxidant effect and polymer properties, minimizing the deterioration of photochromic function and further improving color development durability, which is even more preferable. Specific examples of HALS include bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidyl) 2-(3,5-di-t-butyl-4-hydroxybenzyl)-2-n-butylmalonate, tetrakiss butane-1,2,3,4-tetracarboxylic acid (1,2,2,6,6-pentamethyl-4-piperidyl), tetrakiss butane-1,2,3,4-tetracarboxylic acid (2,2,6,6-tetramethyl-4-piperidyl), and bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate. In the photochromic fibers of the present invention, any component may contain various additives in the polymer, such as inorganic substances like titanium dioxide, silica, and barium oxide, colorants like dyes and pigments, flame retardants, fluorescent whitening agents, antioxidants, or ultraviolet absorbers, to the extent that they do not interfere with the effects of the present invention.

[0064] When a textile product contains at least a portion of the photochromic fibers of the present invention, it is possible to achieve vivid color development upon UV irradiation and a soft texture without hardening of the fabric.

[0065] The term "textile products" as used here refers to a wide variety of intermediates such as fiber winding packages, tow, cut fibers, cotton, fiber balls, cords, piles, woven and knitted fabrics, and nonwoven fabrics, as well as products that utilize these intermediates, ranging from general clothing such as jackets, skirts, pants, and underwear, to sportswear, clothing materials, interior products such as carpets, sofas, and curtains, vehicle interior products such as car seats, and products for everyday use such as cosmetics, cosmetic masks, wiping cloths, and health products, to environmental and industrial materials such as abrasive cloths, filters, hazardous substance removal products, and battery separators, and medical products such as sutures, scaffolds, artificial blood vessels, and blood filters.

[0066] Furthermore, while the photochromic fibers of the present invention can be used in various textiles such as nonwoven fabrics and woven / knitted fabrics, from the viewpoint of suitability for the above-mentioned clothing applications, it is preferable to use woven / knitted fabrics that contain at least a portion of the photochromic fibers of the present invention.

[0067] The structure of the woven or knitted fabric of the present invention is not particularly limited. Examples of woven or knitted fabrics include plain weave, twill weave, satin weave, modified plain weave, modified twill weave, modified satin weave, stylized weave, patterned weave, single-layer weave, double weave, multi-layer weave, warp pile weave, weft pile weave, and leno weave. Examples of knitted fabrics include circular knitting, weft knitting, warp knitting (including tricot knitting and raschel knitting), pile knitting, plain knitting, jersey knitting, rib knitting, smooth knitting (double-sided knitting), rib knitting, pearl knitting, denby weave, cord weave, atlas weave, chain weave, and insert weave. Any structure is acceptable for both woven and knitted fabrics, but when mixed with other fibers, a structure that allows photochromic fibers to be more easily exposed on the surface of the fabric, such as twill weave rather than plain weave, is preferable because it increases the proportion of ultraviolet light directly hitting the photochromic fibers, allowing the photochromic function to be fully exhibited and high color development to be obtained.

[0068] In a woven or knitted fabric containing at least a portion of the photochromic fibers of the present invention, it is preferable that the surface exposure rate of the photochromic fibers in the woven or knitted fabric is 20% or more.

[0069] The surface exposure rate referred to here is calculated as follows:

[0070] The surface of a woven or knitted fabric containing at least a portion of the photochromic fibers of the present invention was photographed at 100x magnification using a Keyence VHX-2000 digital microscope. At this time, a Contec UV-SVGNC365-01 black light (wavelength 365nm, light output 690mW, high mode) was used to irradiate the woven or knitted fabric with ultraviolet light for 1 minute, utilizing the fact that the photochromic fibers change color. The area where the photochromic fibers were exposed (discolored area) on the surface of the woven or knitted fabric was then clearly identified. For the woven or knitted fabrics present in the captured images, image analysis software was used to measure the area of ​​the discolored portion due to ultraviolet irradiation, thereby determining the surface exposure area (μm²) of the photochromic fibers. 2 ) was defined as follows: Surface exposure area of ​​photochromic fiber (μm 2 ) is the total observation area (μm 2The value obtained by dividing by () and multiplying by 100 was calculated and represented as the surface exposure rate (%) of photochromic fibers in the woven or knitted fabric. The above measurement was performed three times, and the value obtained by rounding the arithmetic mean of these measurements to the first decimal place was represented as the surface exposure rate (%) of photochromic fibers in the woven or knitted fabric.

[0071] In a woven or knitted fabric containing at least a portion of the photochromic fibers of the present invention, a surface exposure rate of 20% or more of the photochromic fibers is preferable because it allows for visual confirmation of the color development when irradiated with ultraviolet light. Furthermore, a surface exposure rate of 40% or more is preferable because it increases the area of ​​discoloration on the surface of the woven or knitted fabric, resulting in more vivid color development. Moreover, a surface exposure rate of 50% or more is particularly preferable because it increases the proportion of ultraviolet light irradiated onto the woven or knitted fabric that directly hits the photochromic fibers, allowing the photochromic function to be fully exhibited and high color development to be obtained.

[0072] An example of a method for producing photochromic fibers and woven / knitted fabrics according to the present invention is described in detail below.

[0073] In the photochromic fibers of the present invention, specific examples of nonpolar polymers include olefin polymers such as polyethylene and polypropylene, and polystyrene polymers. Furthermore, as the other polymer that does not contain a photochromic dye, thermoplastic polymers with excellent processability, such as polyester, polyethylene, polypropylene, polystyrene, polyamide, polycarbonate, polymethyl methacrylate, and polyphenylene sulfide polymers and their copolymers, are preferred.

[0074] The photochromic dyes used in the present invention can be organic photochromic compounds such as azobenzene compounds, benzaldehyde compounds, azomethine compounds, stilbene compounds, spiropyran compounds, pyran compounds, spirooxazine compounds, spironaphthoxazine compounds, indolinospironaphthoxazine compounds, spirothiopyran compounds, fulgide compounds, diarylethene compounds, cinnamic acid compounds, retinal compounds, dithizone metal complexes, dihydroprene compounds, triphenylmethane compounds, and hemithioindico compounds. Among these, spiropyran compounds, pyran compounds, spirooxazine compounds, or spironaphthoxazine compounds are preferred from the viewpoint of color development and durability. A nonpolar polymer containing the photochromic dye used in the present invention can be produced by directly adding the photochromic dye to a nonpolar polymer and kneading it.

[0075] As a method for fiberizing the nonpolar polymer containing the above-mentioned photochromic dye and the other polymer, it is possible to select methods such as melt spinning for the purpose of producing long fibers, wet and wet-dry solution spinning, and melt-blown and spunbond methods suitable for obtaining sheet-like fiber structures. However, in view of the objectives of the present invention, melt spinning is preferred, and by utilizing this spinning method, the photochromic fibers of the present invention can be produced with high productivity.

[0076] Melt spinning involves melting the resin by pressing it against a hot plate or the like, and then extruding it through an extrusion hole drilled in a spinneret to form fibers. The melting temperature, or spinning temperature, is preferably set to a temperature at which high-melting-point and high-viscosity polymers exhibit fluidity. While this fluidity temperature varies depending on the molecular weight, setting it between the polymer's melting point and its melting point + 60°C allows for stable production.

[0077] The molten resin is taken up by a rotating roller or the like. The spinning speed is preferably around 500 to 6000 m / min, and can be changed depending on the properties of the polymer and the intended use of the fiber. In particular, from the viewpoint of achieving high orientation and improving mechanical properties, a speed of 500 to 4000 m / min followed by stretching is preferable because it promotes uniaxial orientation of the fiber. When stretching, it is preferable to set the preheating temperature appropriately, using the glass transition temperature of the polymer or the temperature at which it can be softened as a guide. The upper limit of the preheating temperature should preferably be such that no disruption of the fiber path occurs due to spontaneous elongation of the fiber during the preheating process. For example, in the case of PET, where the glass transition temperature is around 70°C, this preheating temperature is usually set to around 80 to 95°C.

[0078] Furthermore, stable production is possible by setting the discharge rate per single hole in the die to approximately 0.1 to 10 g / min / hole. After the discharged polymer flow cools and solidifies, an oil agent is applied, and it is picked up by a roller set to a specified peripheral speed. Subsequently, it is stretched by a heated roller to become the desired photochromic fiber.

[0079] The spinning end used in manufacturing the photochromic fibers of the present invention can also be manufactured using conventionally known composite spinning end caps. However, in the present invention, which aims to improve the color development of the product, improving the homogeneity of the fiber cross-section, such as variations in interface length, is important from the viewpoint of improving the quality of the textile product. For this reason, it is preferable to use a composite spinning end cap using a distribution plate, for example, as described in Japanese Patent Application Publication No. 2011-208313, which allows for the production of a composite cross-section in which the sum of the interface lengths of the nonpolar polymer containing the photochromic dye and the other polymer is precisely controlled.

[0080] The composite die shown in Figure 2 is assembled into a spinning pack with three main components stacked from top to bottom: a measuring plate 1, a distribution plate 2, and a discharge plate 3, and is used for spinning.

[0081] In the composite nozzle illustrated in Figure 2, the metering plate 1 measures and directs the amount of polymer into each discharge hole and distribution hole, the distribution plate 2 controls the composite cross-section and its cross-sectional shape in the cross-section of the single fiber, and the discharge plate 3 compresses the composite polymer flow formed by the distribution plate 2 and discharges it.

[0082] To avoid confusion in the explanation of the composite spinneret, although not shown in the diagram, for components stacked above the weighing plate 1, components with flow channels formed in accordance with the spinning machine and spinning pack can be used. By designing the weighing plate 1 to match existing flow channel components, existing spinning packs and their components can be used as is. Therefore, there is no need to exclusively use the spinning machine for this spinneret. In practice, it is also preferable to stack multiple flow channel plates between the flow channel and the weighing plate or between the weighing plate 1 and the distribution plate 2. The purpose of this is to provide flow channels that efficiently transfer the polymer in the direction of the spinneret cross-section and the cross-section of the single fiber, and to introduce it into the distribution plate 2. The composite polymer flow discharged from the discharge plate 3 is cooled and solidified according to the manufacturing method described above, then lubricated and taken up by rollers at a specified peripheral speed. After that, it is stretched by heated rollers to become the desired composite fiber.

[0083] In the photochromic fibers of the present invention, any component may contain various additives in the polymer, such as inorganic substances like titanium dioxide, silica, and barium oxide, colorants like dyes and pigments, flame retardants, fluorescent whitening agents, antioxidants, or ultraviolet absorbers, to the extent that they do not interfere with the effects of the present invention.

[0084] When the photochromic fibers of the present invention are used in textile products, after the photochromic fibers of the present invention are made into textiles, water-repellent, antistatic, flame-retardant, moisture-absorbing, antibacterial, softening, and other known post-processing treatments can be used in combination as needed.

[0085] The woven or knitted fabric of the present invention, which partially contains the photochromic fibers, is not particularly limited in terms of the weaving or knitting method, as long as the surface exposure rate of the photochromic fibers is 20% or more, and can be woven or knitted using conventional methods. In the case of a woven fabric, for example, weaving can be done using a water jet loom, air jet loom, rapier loom, jacquard loom, etc. In the case of a knitted fabric, for example, knitting can be done using a circular knitting machine, warp knitting machine, etc. [Examples]

[0086] The photochromic fibers of the present invention will be described in detail below with reference to examples.

[0087] The following evaluations were performed on the examples and comparative examples.

[0088] A. Melting point of polymers Chip-shaped polymer was dried in a vacuum dryer to a moisture content of 200 ppm or less, and approximately 5 mg was weighed. A differential scanning calorimeter (DSC) Q2000 manufactured by TA Instruments was used to measure the temperature from 0°C to 300°C at a heating rate of 16°C / min, and then held at 300°C for 5 minutes. The melting point was calculated from the melting peak observed during the heating process. Three measurements were performed for each sample, and the average value was taken as the melting point. In the case where multiple melting peaks were observed, the top of the highest temperature melting peak was taken as the melting point (°C).

[0089] B. Hansen's solubility parameters (HSP value, polarity term of HSP value) Prepare 24 different solvents with varying Hansen solubility parameters (HSP values), and add 0.10 g of tip-shaped polymer to 2 mL of each solvent (weight before immersion: W). D Add the solvent (W) and let it stand at room temperature for 7 days. After wiping off the solvent adhering to the surface of each polymer, weigh the polymer after immersion. W The measured solvent density (ρ) was weighed. L ) and polymer density (ρ S Using ), the polymer volume before immersion (V) is calculated using the following formula. D ), polymer volume after immersion (V W ), degree of swelling (S W ) was calculated. V D = W D / ρ S V W = V D +(W W -W D ) / ρ L S W = V W / V D Based on the above results, the swelling threshold was set to 1.05 for olefin polymers and 1.02 for polyester polymers. Those above the threshold were classified as good solvents, and those below the threshold were classified as poor solvents. For polyamides, the threshold was set to 0.95, and those below the threshold were classified as good solvents, while those above the threshold were classified as poor solvents. The results were entered into solubility parameter calculation software (HSPiP (ver. 5.2.05)) and the polarity term of the HSP value (MPa) was calculated. 1 / 2 ) and HSP value (MPa) 1 / 2 The following values ​​were calculated. Furthermore, the solubility parameters of the organic solvents were obtained using the values ​​from the aforementioned solubility parameter calculation software (HSPiP (ver. 5.2.05)).

[0090] C. Fineness The weight of 100m of fiber was measured, and this value was multiplied by 100 to calculate the fineness (dtex). This process was repeated 10 times, and the arithmetic mean of these values, rounded to two decimal places, was defined as the fineness (dtex). The single fiber fineness (dtex) is calculated by dividing the above fineness by the number of filaments.

[0091] D. Threads Yarn variability (U%(h)) was measured using a Zerbeger Worcester UT-4 yarn variability tester under the following conditions: measurement speed 200 m / min, measurement time 2.5 min, and twister 6000 / min.

[0092] E. Fiber diameter After embedding the fibers in an embedding agent such as epoxy resin, the cross-sections were photographed using a Keyence VHX-2000 digital microscope at any magnification between 20x and 2000x that allowed for cross-sectional identification. From each image, the area of ​​a randomly selected fiber was measured, and the diameter, calculated as a perfect circle, was measured in μm to one decimal place. This was done for 10 filaments, and the simple numerical average of the results was calculated, rounded to the first decimal place, to determine the fiber diameter (μm). If a hollow portion existed in the fiber cross-section perpendicular to the fiber axis, the area of ​​the hollow portion was added to the fiber area.

[0093] F. Cross-sectional parameters (composite ratio, sum of interface lengths, interface length variation) After embedding the fibers in an embedding agent such as epoxy resin, the cross-section was photographed using a Keyence VHX-2000 digital microscope at any magnification between 20x and 2000x that allowed for identification of the cross-section. During this process, a Contec UV-SVGNC365-01 black light (wavelength 365nm, light output 690mW, high mode) was used to irradiate the cross-section with ultraviolet light for 1 minute. The discolored areas were identified as the photochromic dye-containing layer, the undiscolored areas as the non-dye-containing layer, and the junctions between them as the interfaces. The composite ratio, sum of interface lengths, and interface length variation were calculated from the captured images using image analysis software with the following methods.

[0094] F-1. Composite ratio The composite ratio is the area (μm²) of the photochromic dye-containing layer that has changed color upon UV irradiation, for a cross-section of a single fiber present in the captured image. 2 ) is the total area of ​​the fiber cross-section (μm 2 The value obtained by dividing by () and multiplying by 100 was taken as the composite ratio (%) of the nonpolar polymer containing the photochromic dye in one fiber. The above measurement was performed for 10 fibers to calculate the composite ratio for each fiber, and the composite ratio (%) of the nonpolar polymer containing the photochromic dye was evaluated by rounding the first decimal place of these arithmetic mean values.

[0095] F-2. Sum of interface lengths The sum of interface lengths was calculated by first determining an arbitrary position at the interface between the photochromic dye-containing layer and the non-containing layer (which had changed color due to UV irradiation) in the cross-section of a single fiber present in the captured image. The measurement started from the starting point, followed by a series of images, and the length from there back to the starting point was measured. This value was defined as the interface length (μm). The same method was used to measure all interface lengths in the cross-section, and the sum of these was defined as the sum of interface lengths (μm) for a single fiber. The above measurement was performed for 10 fibers to calculate the sum of interface lengths for each fiber, and the sum of the arithmetic mean of these values, rounded to the first decimal place, was defined as the sum of interface lengths (μm).

[0096] F-3. Variation in interface length The interface length variation was calculated based on the measurement results of the sum of interface lengths calculated in F-2, using the formula: Interface Length Variation (Interface Length CV%) = (Standard Deviation of Sum of Interface Lengths / Mean of Sum of Interface Lengths). The value was rounded to two decimal places and given as Interface Length Variation (%).

[0097] G. Evaluation of fibers (color development, color durability) For the fibers to be evaluated, plate windings were prepared using an Eiko Sangyo Co., Ltd. aligned winding evaluation device (model SAW-S05-60) with a winding pitch of 0.3 mm and 8 traverses. Color development and color durability evaluations were then performed using the following methods.

[0098] G-1. Evaluation of the color development properties of fibers Using a Minolta CM-3700d spectrophotometer, with the reflectance of a standard white plate set to 100, the reflectance of a plate winding was measured using a D65 light source, a field of view of 10°, a measurement diameter of 8mm, and SCE (Specular Reflectance Rejection Method). A0 The reflectance (R) of the plate winding after UV irradiation in the wavelength range of 360-740 nm was measured and values ​​were extracted at 10 nm intervals. Next, using a CONTEC black light UV-SVGNC365-01 (wavelength 365 nm, light output 690 mW, high mode), the plate winding was irradiated with ultraviolet light at an irradiation distance of 1 cm for 1 minute, and the reflectance (R) of the plate winding after UV irradiation in the wavelength range of 360-740 nm was measured. A1 ) is measured, and the difference in reflectance of the composite fiber before and after UV irradiation at each wavelength (R A The value was calculated using the following formula. Reflectance difference R of composite fiber before and after UV irradiation A (%)=R A0 -R A1 The arithmetic mean of the results obtained by performing this operation at a total of three locations is calculated, and the value is rounded to the nearest whole number. The reflectance difference (R) at each wavelength is then calculated. A ) are compared and their maximum values ​​are the difference in maximum reflectance of the fiber before and after UV irradiation (R A_max )

[0099] The maximum reflectance difference obtained (R A_max The color development properties of the composite fibers were evaluated on a four-point scale based on the following criteria. S: Excellent color development (50 ≤ maximum reflectance difference R) A_max ) A: Good color development (30 ≤ maximum reflectance difference R) A_max <50) B: Has color development (10 ≤ maximum reflectance difference R) A_max <30) C: Poor color rendering (maximum reflectance difference R) A_max <10).

[0100] G-2. Evaluation of colorfastness and durability of fibers Using a Suga Test Instruments U48AU ultraviolet carbon arc lamp lightfastness tester, a plate winding was subjected to a radiation intensity test of 500 W / m². 2 Light irradiation was performed for 0 hours, 0.5 hours, 1 hour, and 2 hours. After irradiation, the difference in maximum fiber reflectance (R) before and after UV irradiation was measured for each plate winding using the same procedure as for G-1. A_max The maximum reflectance difference (R) at a light irradiation time of 0 hours was calculated. A_max The time during which the color retention rate was maintained at 80% or higher was defined as the durability time (T), and the color durability of the fibers was judged in four stages based on the following criteria. S: Excellent colorfastness and durability (durability time T=2 hours) A: Good color retention (durability time T=1 hour) B: Has good color retention (durability time T=0.5 hours) C: Poor color development durability (durability time T = less than 0.5 hours), or undeterminable (if a C rating is given in G-1. Fiber color development evaluation).

[0101] H. Evaluation of woven and knitted fabrics (surface exposure rate, color development, color durability, color uniformity) After scouring and heat setting the woven and knitted fabrics, the following methods were used to measure surface exposure, evaluate color development, evaluate color durability, and evaluate color uniformity.

[0102] H-1.Surface exposure rate Using a Keyence VHX-2000 digital microscope, the surface of woven and knitted fabrics was photographed at 100x magnification. During this process, a Contec UV-SVGNC365-01 black light (wavelength 365nm, light output 690mW, high mode) was used to irradiate the fabric with ultraviolet light for one minute. This utilized the fact that photochromic fibers change color, clearly identifying the area of ​​photochromic fiber exposure (discolored area) on the surface of the fabric. For the woven and knitted fabrics in the captured images, image analysis software was used to measure the area of ​​the discolored portion due to ultraviolet irradiation, thereby determining the surface exposure area (μm²) of the photochromic fibers. 2 ) was defined as follows: Surface exposure area of ​​photochromic fiber (μm 2 ) is the total observation area (μm 2 The value obtained by dividing by () and multiplying by 100 was calculated and represented as the surface exposure rate (%) of photochromic fibers in the woven or knitted fabric. The above measurement was performed three times, and the value obtained by rounding the arithmetic mean of these measurements to the first decimal place was represented as the surface exposure rate (%) of photochromic fibers in the woven or knitted fabric.

[0103] H-2. Evaluation of color development of woven and knitted fabrics Using a Minolta CM-3700d spectrophotometer, with the reflection of a standard white plate set to 100, the reflectance of woven and knitted fabrics was measured using a D65 light source, a field of view of 10°, a measurement diameter of 8mm, and SCE (Specular Reflectance Rejection). B0 The reflectance (R) of the woven or knitted fabric after UV irradiation was measured and values ​​were extracted at 10 nm intervals in the wavelength range of 360 to 740 nm. Next, a CONTEC black light UV-SVGNC365-01 (wavelength 365 nm, light output 690 mW, high mode) was used to irradiate the woven or knitted fabric with ultraviolet light at an irradiation distance of 1 cm for 1 minute, and the reflectance (R) of the woven or knitted fabric after UV irradiation in the wavelength range of 360 to 740 nm was measured. B1) is measured, and the difference in reflectance of the woven or knitted fabric before and after UV irradiation at each wavelength (R B The value was calculated using the following formula. Difference in reflectance R of woven or knitted fabrics before and after UV irradiation B (%)=R B0 -R B1 The arithmetic mean of the results obtained by performing this operation at a total of three locations is calculated, and the value is rounded to the nearest whole number. The reflectance difference (R) at each wavelength is then calculated. B ) are compared and their maximum values ​​are used to determine the difference in maximum reflectance of woven fabrics before and after UV irradiation (R B_max )

[0104] The maximum reflectance difference obtained (R B_max The color development of woven and knitted fabrics was evaluated on a four-point scale based on the following criteria. S: Excellent color development (50 ≤ maximum reflectance difference R) B_max ) A: Good color development (30 ≤ maximum reflectance difference R) B_max <50) B: Has color development (10 ≤ maximum reflectance difference R) B_max <30) C: Poor color rendering (maximum reflectance difference R) B_max <10).

[0105] H-3. Evaluation of colorfastness and durability of woven and knitted fabrics Using a Suga Test Instruments U48AU ultraviolet carbon arc lamp lightfastness tester, woven and knitted fabrics were subjected to a radiation intensity test of 500 W / m². 2 Light irradiation was performed for 0 hours, 0.5 hours, 1 hour, and 2 hours. After irradiation, the difference in maximum reflectance (R) of each woven or knitted fabric before and after UV irradiation was measured using the same procedure as in H-2. B_max The maximum reflectance difference (R) at a light irradiation time of 0 hours was calculated. B_max The time during which the color retention rate was maintained at 80% or higher was defined as the durability time (T), and the color durability of the woven or knitted fabric was judged in four stages based on the following criteria. S: Excellent colorfastness and durability (durability time T=2 hours) A: Good color retention (durability time T=1 hour) B: Has good color retention (durability time T=0.5 hours) C: Poor colorfastness (durability time T = less than 0.5 hours), or undeterminable (if a C rating is given in H-2. Evaluation of colorfastness of woven or knitted fabrics).

[0106] H-4. Evaluation of color uniformity of woven and knitted fabrics Using a CONTEC UV-SVGNC365-01 black light (wavelength 365nm, light output 690mW, high mode), ultraviolet light was shone onto a woven or knitted fabric at a distance of 1cm over a diameter of 4cm for 1 minute. This procedure was performed at five arbitrary locations, and based on the differences in color development (color intensity, unevenness) at these five locations, five inspectors with more than five years of experience in quality assessment determined the uniformity of color development on a four-point scale based on the following criteria. S: The color development is the same in all 5 locations. A: One out of five locations has a different color development. B: Two out of five locations have different color rendering. C: Color development differs in 3 or more out of 5 locations, or determination is impossible (H-2. If a C rating is given in the evaluation of color development of woven or knitted fabrics).

[0107] I. Texture Evaluation (Flexibility) After scouring and heat setting the woven and knitted fabrics, their flexibility was evaluated using the following methods.

[0108] Using a Kato Tech pure bending tester (KES-FB2), a 20cm x 20cm woven or knitted fabric was held with an effective sample length of 20cm x 1cm and bent in the weft direction, with curvature K being ±0.5 and ±1.5cm. -1 The bending moment per unit width (gf·cm / cm) is expressed as curvature (1cm -1 The value was calculated by dividing by ). This operation was performed 3 times at each location, and the simple numerical average of the results for a total of 10 locations was calculated. After rounding to the fourth decimal place, the value was divided by 100 to obtain the bending hardness B × 10 -2 (gf·cm 2 The bending hardness obtained was B × 10⁻¹⁰. -2 Flexibility was assessed on a three-point scale based on the following criteria. S: Excellent flexibility (bending hardness B x 10) -2 ≤3.5) A: Good flexibility (3.5 < Bending hardness B x 10)-2 ≤4.5) B: Flexible (4.5 < Bending hardness B x 10) -2 ≤5.5) C: Poor flexibility (5.5 < Bending hardness B x 10) -2 ).

[0109] [Example 1] Polymer 1 is a polypropylene (PP) containing 4 wt% of 1,3-dihydro-1,3,3-trimethyl-6'-(1-piperidinyl)-6-(trifluoromethyl)-spiro{2H-indole-2,3'(3H)naphtho(2,1-b)(1,4)oxazine (photochromic dye), with an HSP value of 16.8 MPa. 1 / 2 Polarity term of HSP value: 1.6 MPa 1 / 2 A mixture of polypropylene (melting point: 165°C) and polypropylene without photochromic dyes was prepared as a chip blend in a 1:1 weight ratio, and nylon 6 (N6, melting point: 220°C) was prepared as polymer 2.

[0110] After melting these polymers separately, polymer 1 / polymer 2 was weighed in a weight ratio of 20 / 80 and poured into a spinning pack incorporating the composite die shown in Figure 2. The incoming polymers were then extruded from the discharge hole to form a composite fiber cross-section with a core-sheath type circular cross-section (core: polymer 1, sheath: polymer 2) as illustrated in Figure 1(a).

[0111] A composite fiber with 56 dtex-24 filaments (single fiber fineness: 2.3 dtex, yarn unevenness U%(h): 0.8%) was produced by applying a cooling and solidification-based oil agent to the discharged composite polymer stream, winding it at a spinning speed of 800 m / min, and stretching it between rollers heated to 70°C and 150°C.

[0112] The resulting composite fiber has a core-sheath type composite cross-section in which the core component reversibly changes color from colorless to pink upon UV irradiation. The fiber diameter is 17 μm, the composite ratio of the photochromic dye-containing polymer (polymer 1) is 22%, the total interface length is 24 μm, the interface length variation is 3.0%, and the color development is measured by the maximum reflectance difference (R A_max) was 49%, which is favorable, and the color development durability was also favorable, confirming that the product is the photochromic fiber of the present invention.

[0113] Using the obtained photochromic fiber as the weft, and a general-purpose nylon 6 fiber (containing no photochromic dye, 56 dtex-40 filaments) as the warp, the cover factor in the warp direction (CF A ) was 1000, and the cover factor in the weft direction (CF B ) was adjusted to 1000 by adjusting the number of fibers, thereby obtaining a 1 / 3 twill woven fabric. However, the CF referred to herein A and CF B are values obtained by measuring the warp density and weft density of the woven fabric in a 2.54 cm section in accordance with JIS-L-1096:2010 8.6.1, and CF A = warp density × (fineness of warp) 1 / 2 , and CF B = weft density × (fineness of weft) 1 / 2 from the above formula.

[0114] The obtained woven fabric was scoured in warm water of 80°C containing a surfactant for 20 minutes, and then heat-set at 165°C for 1 minute.

[0115] The obtained woven fabric (surface exposure rate of photochromic fiber: 71%) reversibly discolors from colorless to pink under ultraviolet irradiation, and has uniform and favorable color developability with no color development spots (maximum reflectance difference R B_max : 47%) and color development durability. In addition, by reducing the compounding ratio of the nonpolar polymer containing the photochromic dye, the proportion of the polymer that softens during heat treatment (heat setting) is suppressed to a small amount in this fabric, thereby achieving good flexibility (bending hardness B: 3.7×10 -2 gf·cm 2 / cm) without texture hardening which was a conventional problem, and this woven fabric has both vivid color developability and soft texture which are not available in conventional materials. The results are shown in Table 1.

[0116] [Examples 2 and 3] Polymer 1 was replaced with high-density polyethylene (Example 2, HDPE, HSP value: 17.1 MPa 1 / 2, polar term of HSP value: 0.8 MPa 1 / 2 , melting point: 129°C), or syndiotactic polystyrene (Example 3, sPS, HSP value: 19.3 MPa 1 / 2 , polar term of HSP value: 4.5 MPa 1 / 2 , the procedure was performed in the same manner as in Example 1 except that the melting point was changed to 270°C).

[0117] In Example 2, since the HSP value or the polar term of the HSP value of the polymer containing the photochromic dye is small, deactivation of the photochromic function caused by the reaction between the dye and the polymer is suppressed, and the color developability of the conjugate fiber and the woven or knitted fabric is improved.

[0118] In Example 3, since the polymer containing the photochromic dye is also non-polar, the photochromic function is not deactivated. On the other hand, since the melting point is high, the heat resistance as a fiber is also improved. The results are shown in Table 1.

[0119] [Comparative Examples 1 and 2] Polymer 1 was changed to polyethylene terephthalate (Comparative Example 1, PET, HSP value: 21.4 MPa 1 / 2 , polar term of HSP value: 4.9 MPa 1 / 2 , melting point: 255°C), or nylon 6 (Comparative Example 2, N6, HSP value: 23.7 MPa 1 / 2 , polar term of HSP value: 10.1 MPa 1 / 2 , the procedure was performed in the same manner as in Example 1 except that the melting point was changed to 220°C).

[0120] In Comparative Examples 1 and 2, since the HSP value or the polar term of the HSP value of the polymer containing the photochromic dye is high, it is considered that when the polymer is melted, the photochromic dye reacts with the polar portion of the polymer to deactivate the photochromic function. The obtained conjugate fiber and woven fabric did not undergo any discoloration even when irradiated with ultraviolet light. In addition, since neither discolored by ultraviolet irradiation, the color development durability evaluation and the color development uniformity evaluation could not be determined. The results are shown in Table 1.

[0121] [Examples 4 and 5] The procedure was carried out in the same manner as in Example 1, except that the weight ratio of Polymer 1 / Polymer 2 was changed to 10 / 90 (Example 4) and 45 / 55 (Example 5).

[0122] In Example 4, by reducing the composite ratio of the nonpolar polymer (polymer 1) containing the photochromic dye to 12%, the proportion of polymer that softens during heat treatment is reduced, suppressing hardening of the texture, resulting in excellent flexibility even after heat treatment.

[0123] In Example 5, increasing the composite ratio of the nonpolar polymer containing the photochromic dye to 50% increased the photochromic dye content in the entire fiber, improving the color development and color durability when exposed to ultraviolet light. The results are shown in Table 1.

[0124] [Comparative Example 3] The procedure was carried out in the same manner as in Example 1, except that the weight ratio of Polymer 1 / Polymer 2 was changed to 60 / 40.

[0125] In Comparative Example 3, the high composite ratio of the nonpolar polymer containing the photochromic dye (67%) caused the fibers to deform due to the softening of the nonpolar polymer during heat treatment, resulting in densification that filled the interfiber gaps and thus a hardened texture and loss of flexibility. Furthermore, because PP and N6 have poor polymer compatibility, a higher composite ratio leads to unstable cross-sectional formation, increased variation in interface length, and a larger yarn variability (U%(h)), making it easier for unevenness in fiber density to occur and reducing color uniformity. The results are shown in Table 1.

[0126] [Table 1]

[0127] [Examples 6, 7, 8, 9, 10] Except for changing the discharge rate so that the fiber diameter of the photochromic fiber was 10 μm (Example 6), 21 μm (Example 7), 30 μm (Example 8), 40 μm (Example 9), and 50 μm (Example 10), all other steps were carried out according to Example 1.

[0128] In Example 6, reducing the fiber diameter or single fiber fineness resulted in a more uniform distribution of photochromic fibers throughout the fabric, improving color uniformity. In addition, the reduced fiber diameter or single fiber fineness led to a decrease in the bending stiffness of the single fibers, thus improving flexibility.

[0129] In Examples 7 to 10, as the fiber diameter or single fiber fineness increased, not only did the color development improve, but the resilience also increased while maintaining flexibility. The results are shown in Table 2.

[0130] [Examples 11, 12, 13] The composite fiber cross-section was made into a sea-island type with an island arrangement as shown in Figure 1, and the procedure was carried out in the same manner as in Example 1, except that the number of island components composed of polymer 1 was changed to 7 islands (Figure 1(b): Example 11), 13 islands (Figure 1(c): Example 12), and 109 islands (Figure 1(d): Example 13).

[0131] In Examples 11 to 13, as the number of islands increased, the nonpolar polymer containing the photochromic dye became finely dispersed in the fibers, improving color uniformity. In addition, the deformation of the fibers due to the softening of the nonpolar polymer during heat treatment was further suppressed, resulting in a texture that did not harden and exhibited excellent flexibility. The results are shown in Table 2.

[0132] [Table 2]

[0133] [Examples 14, 15] The procedure was carried out in the same manner as in Example 1, except that polymer 2 was changed to polyethylene terephthalate (PET, melting point: 255°C) and nylon 6 (N6, melting point: 180°C).

[0134] In Example 14, the placement of polymers with higher melting points on the fiber surface improved the heat resistance of the fiber and gave it the characteristic firmness and resilience of PET.

[0135] In Example 15, using a low-melting-point polymer as polymer 2 lowered the overall spinning temperature, suppressed the reaction at the interface between the polymer containing the photochromic dye and the other polymer, and slightly improved the color development. The results are shown in Table 3.

[0136] [Examples 16, 17] Photochromic fibers were manufactured in the same manner as in Example 1, and the photochromic fibers were used as the weft, while general-purpose nylon 6 single fibers (56dtex-40 filament) were used as the warp, with a warp direction cover factor (CF) A ) is 1000, and the weft direction cover factor (CF) B The number of fibers was adjusted so that the ratio was 1000, and plain weave fabric (Example 16) and 8-ply satin (Example 17) were obtained. The obtained fabrics were scouring in 80°C hot water containing a surfactant for 20 minutes, and then heat-set at 165°C for 1 minute.

[0137] In Example 16, by using a plain weave, the photochromic fibers were uniformly exposed throughout the fabric, resulting in improved color uniformity.

[0138] In Example 17, increasing the surface exposure rate of the photochromic fibers increased the proportion of ultraviolet light irradiated onto the fabric that directly hit the photochromic fibers, resulting in the photochromic function being fully utilized and improving color development. The results are shown in Table 3.

[0139] [Example 18] Photochromic fibers were produced in the same manner as in Example 1, and a smooth knitted fabric was obtained using these fibers on a 28G circular knitting machine. The resulting fabric was scouring in 80°C hot water containing a surfactant for 20 minutes, and then heat-set at 165°C for 1 minute.

[0140] In Example 18, the surface exposure rate of the photochromic fibers was 100%, and the photochromic function was fully exhibited across the entire surface of the knitted fabric, resulting in improved color uniformity and color development. The results are shown in Table 3.

[0141] [Comparative Example 4] The procedure was carried out in the same manner as in Comparative Example 3, except that the spinning pack was changed to one incorporating a conventionally known core-sheath type composite nozzle.

[0142] In Comparative Example 4, the use of a conventionally known composite die resulted in poor metering of the molten polymer, and the interface length variation in the fiber cross-section increased to 32%, and the yarn unevenness U%(h) in the fiber axis direction increased to 2.3%. Furthermore, the increased interface length variation and yarn unevenness U%(h) led to uneven color development in the resulting fabric, resulting in reduced color uniformity. The results are shown in Table 3.

[0143] [Example 19] The procedure was carried out in the same manner as in Example 1, except that the photochromic dye was changed to 1,3-dihydro-1,3,3-trimethyl-6'-(1-piperidinyl)-spiro{2H-indole-2,3'-[3H]naphtho[2,1-b][1,4]-oxazine.

[0144] In Example 19, by changing the type of photochromic dye, photochromic fibers and fabrics that changed from colorless to purple upon ultraviolet irradiation were obtained. The results are shown in Table 3.

[0145] [Example 20] Polymer 1 is a polypropylene (PP, HSP value: 16.8MPa) containing 4 wt% of 1,3-dihydro-1,3,3-trimethyl-6'-(1-piperidinyl)-6-(trifluoromethyl)-spiro{2H-indole-2,3'(3H)naphtho(2,1-b)(1,4)oxazine (photochromic dye) and 8 wt% of bis(2,2,6,6-tetramethyl-4-piperidyl) (HALS) sebacate. 1 / 2Polarity term of HSP value: 1.6 MPa 1 / 2 The procedure was carried out in the same manner as in Example 1, except that the mixture was changed to a chip blend of polypropylene without photochromic dye and HALS in a weight ratio of 1:1 (melting point: 165°C) and HALS-free polypropylene.

[0146] In Example 20, the addition of HALS improved the color development durability of the photochromic fibers and fabrics. The results are shown in Table 3.

[0147] [Table 3] [Industrial applicability]

[0148] The photochromic fibers of the present invention possess both vivid color development upon ultraviolet irradiation and a soft texture without hardening, making them suitable for a wide range of textile products, from general clothing such as jackets, skirts, pants, and underwear, to sportswear and clothing materials, as well as interior products such as carpets, sofas, and curtains, vehicle interior products such as car seats, cosmetics, cosmetic masks, wiping cloths, and health products, and environmental and industrial materials such as abrasive cloths, filters, hazardous substance removal products, and battery separators, and medical applications such as sutures, scaffolds, artificial blood vessels, and blood filters. [Explanation of Symbols]

[0149] A nonpolar polymer containing a photochromic dye. B interface C-preserved polymer 1 Measuring plate 2-way splitter plate 3 Discharge plate

Claims

1. A photochromic fiber comprising two or more polymers, wherein at least a portion of the fiber's cross-section is composed of a nonpolar polymer containing a photochromic dye, and the composite ratio of the polymers is 50% or less.

2. The photochromic fiber according to claim 1, comprising a nonpolar polymer containing a photochromic dye and another polymer, wherein the sum of the interface lengths is 1 to 100 μm.

3. The photochromic fiber according to claim 1 or 2, characterized in that the variation in the interface length between the nonpolar polymer containing the photochromic dye and the other polymer in the fiber cross-section is 0 to 30.0%.

4. A textile product comprising at least a portion of the photochromic fiber described in any one of claims 1 to 3.

5. A woven or knitted fabric comprising at least a portion of the photochromic fiber described in any one of claims 1 to 3, with a surface exposure rate of 20% or more.

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